Title of Invention	PROCESS FOR MIXING AN ACIDIC AQUEOUS SOLUTION COMPRISING HYDROXYLAMMONIUM AND PHOSPHATE WITH NITRIC ACID
Abstract	The invention relates to a process for mixing a first acidic aqueous solution comprsmg hydroxyiammonium and phosohate wiih a second acidic aqueous solution composing nitric ac;d 2; a temperature between 20 and 80 °C resulting in a third acidic aqueous solution comprising hydroxyiammonium, phosphate and nitric acid, wherein in the third acidic aquscus solution the totai acid concentration minus the chosphate concentration is lows- than 0.523 in([hydroxylammon[um]/1.25) + 422/(T + 31) whereby [hydrcxylamrnoniumj s the concentration of hydroxyiammonium in the third acidic aqueous soiuticr., T is the temperature of the third acidic aqueous solution expressed in °C and all concentrations are excressed in mol/l.

Title of Invention

PROCESS FOR MIXING AN ACIDIC AQUEOUS SOLUTION COMPRISING HYDROXYLAMMONIUM AND PHOSPHATE WITH NITRIC ACID

Abstract

The invention relates to a process for mixing a first acidic aqueous solution comprsmg hydroxyiammonium and phosohate wiih a second acidic aqueous solution composing nitric ac;d 2; a temperature between 20 and 80 °C resulting in a third acidic aqueous solution comprising hydroxyiammonium, phosphate and nitric acid, wherein in the third acidic aquscus solution the totai acid concentration minus the chosphate concentration is lows- than 0.523 in([hydroxylammon[um]/1.25) + 422/(T + 31) whereby [hydrcxylamrnoniumj s the concentration of hydroxyiammonium in the third acidic aqueous soiuticr., T is the temperature of the third acidic aqueous solution expressed in °C and all concentrations are excressed in mol/l.

Full Text	PROCESS FOR MIXING AN ACIDIC AQUEOUS SOLUTION COMPRISING HYDROXYLAMMONIUM AND PHOSPHATE WITH NITRIC ACID The invention relates to a process for mixing a first acidic aqueous solution comprising hydroxylammonium and phosphate with a second acidic aqueous solution comprising nitric acid, resulting in a third acidic aqueous solution comprising hydroxylammonium, phosphate and nitric acid. Cydohexanone oxime can be prepared in a process in which an aqueous reaction medium is cycled from a hydroxylammonium synthesis reactor in which hydroxylammonium is prepared by catalytic reduction of nitrate with hydrogen to a cydohexanone oxime synthesis reactor in which cydohexanone oxime is produced by reaction of hydroxylammonium with cydohexanone and from the cydohexanone oxime synthesis reactor back to the hydroxylammonium synthesis reactor. To make up for the nitrate that is reduced in the hydroxylammonium synthesis reactor, nitric add can be introduced into the aqueous reaction medium by mixing a nitric acid solution with the aqueous solution leaving the cydohexanone oxime synthesis zone. The aqueous reaction medium leaving the cydohexanone oxime synthesis reactor may comprise unreached hydroxylammonium. Said unreacted'hydroxylammonium may decompose as a result of the mixing with the nitric acid solution, this decomposition being disadvantageous, as hydroxylammonium is a useful product. CN-A-1281349 discloses the use of a static mixer for mixing both solutions. However, in the mixed solution decomposition of hydroxylammonium may stiii occur. The object of the present invention is to provide a process for mixing a first acidic aqueous solution comprising hydroxylammonium and phosphate with a second acidic aqueous solution comprising nitric acid, resulting in a third acidic aqueous solution comprising hydroxylammonium, phosphate and nitric acid, in which decomposition of hydroxylammonium in the third acidic aqueous solution is prevented or at least reduced. This object is achieved in that in the third acidic aqueous solution the total acid concentration minusJhe phosphate concentration is lower than 0.523 * ln([hydroxylammonium]/1.25) + 422/(T + 31) whereby [hydroxylammonium] is the concentration of hydroxylammonium in the third acidic aqueous solution, T is the temperature of the third acidic aqueous solution expressed in °C and all concentrations are expressed in mdl/!. It has ;n particular been found that decomposition of hydroxyiammonium can be reduced or even prevented by having a hydroxylammonium concentration in the firs: and/or third acidic aqueous solution sufficiently high such that the total acid concentration minus the phosphate concentration in the third acidic aqueous solution is Icv/erthan 0.523 * ln([hydroxylammonium]/1.25) + 4221(1 + 31). Obtaining a sufficiently nigh hydroxylammonium concentration in the first acidic aqueous solution can izr example be achieved by adding hydroxyiammonium to an acidic aqueous solution comprising hydroxylammonium to obtain the first acidic aqueous solution. Obtaining a sufficiently high hydroxylammonium concentration in the third acidic aqueous solution can for example be achieved by adding hydroxylammonium to the third acidic aqueous solution and/or by performing the mixing cf the first and second acidic aqueous solution in a hydroxyiammonium reactor in which hydroxylammonium is prepared by catalytic reduction of nitrate with hydrogen. As used herein, the total acid concentration of an acidic aqueous solution, for instance he first, second, third and fourth acidic aqueous solution, is preferably measured by titration to a pH of 4.2. Preferably, said titration is performed by adding 5 ml of the acicic aqueous solution to 50 ml distilled water and titration-with a 0.25 N NaOH solution to a pH of 4.2. In an acidic aqueous solution comprising H3PO^ and HN03 as the acids, the total acid concentration is a measure for the sum of the concentration of H3FCU and the concentration of HNO3. Preferably the total acid concentration in the firs: acidic aqueous solution is higher than 0.1 mol/l and tower than 6 mol/l. The process according to the invention comprises mixing a first acidic aqueous solution with a second acidic aqueous solution. The mixture obtained as a result of said mixing is. as used herein, also referred to as third acidic aqueous solution. Preferably, the process comprises mixing the first acidic aqueous solution with the second acidic aqueous solution at a temperature between 20 and 80 °C. The first acidic aqueous solution comprises hydroxylammonium and phosphate. The'second acidic aqueous solution comprises nitric acic. Any suitable first acidic aqueous solution and a second acidic aqueous solution may be used, such that the mixing thereof results in a third acidic aqueous solution in which cacid(3)-cphGSOn5ls(3) In a preferred embodiment, the invention provides a process comprising mixing a first acidic aqueous solution comprising hydroxylammonium and phosphate with a second acidic aqueous solution comprising-nitric acid, preferably at a temperature between 20 and 80 CC. resulting in a third acidic aqueous solution ution and in the second acidic aqueous solution respectively, expressed in mol/l. cPhosch3te(1) and cPho5?ra:a(2) are the phosphate concentration in the first acidic aqueous solution and in the second acidic aqueous solution respectively, expressed in moi/L Chya solution, expressed in volume of first acidic aqueous solution per second and volume of second acidic aqueous solution per second respectively. This embedment is an advantageous way for obtaining the third acidic aqueous solution according to the invention and for the prevention of decomposition of hydroxy!ammor.:um. tn general the nydroxylammonium concentration in the first acidic aqueous solution is higher than 0.002 mol/i. for instance higher than 0.005 mol/l, for instance higher than 0.01 mol/L for instance higher than 0.02 mol/l. Typically, the hydroxylammonium concentration in the first acidic aqueous solution ::s below 2 mol/l, preferably below 0.2 mol/L In an embodiment the process according to the invention comprises preparing hydroxylammonium oy catalytic reduction of nitrate with hydrogen in a hydroxylammonium synthesis reactor. The catalytic reduction of nitrate with hydrogen can be represented by the following equation: 2 H2P04 + NO,' + 3 H2 -» NH3OH+ + 2 H2P04_ + 2 H20 In an embodiment, the process according to the invention comprises preparing cyclohexanone oxime by reaction of hydroxylammonium and cyclohexanone in a cyclohexanone oxime synthesis reactor. The reaction of hydroxylammonium and cyclohexanone can be represented by the following equation: NH,OH+ + HzPO; + C5H10O -» C9H10NOH + Hr;P04 + H20 In an embodiment the process according to the invention comprises cycling an aqueous reaction medium from the hydroxylammonium synthesis reactor to the cyclohexanone oxime synthesis reactor, and from the cyclohexanone oxime synthesis reactor back to the hydroxylammonium synthesis reactor In an embodiment of the process according to the invention, an aaueous reaction medium leaving the cyclohexanone oxime synthesis reactor is usee a the first acidic aqueous solution. The use of the aqueous reaction medium leaving tne cyclohexanone oxime synthesis reactor as first acidic aqueous solution may involve a process wherein the aqueous reaction medium leaving the cyclohexanone oxime synthesis reactor is, as the first acidic aqueous medium, mixed with the second acidic aqueous solution, resulting in the third acidic aqueous solution. In an embodiment, the aoueous solution leaving the cyclohexanone oxime reactor may be subjected to extraction prior to mixing the aqueous reaction mixture with the second acidic aqueous solution, in an embodiment, part of the water may be separated from the aqueous reaction mixture leaving the cyclohexanone oxime synthesis reactor ry stripping prior :o mixing the aqueous reaction mixture with the secona acidic aauecJS solution. In an embodiment, the aqueous reaction mixture leaving the cydohexancne oxime synthesis reactor may, optionally after extraction and/or separation of water frcm the aqueous reaction mixture, be separatea into at least a first part and a second cart, and the first parr of the aqueous reaction medium may be mixed with me second acidic aqueous solution. Nitrogen oxides may be absorbed and oxidized in said second part to prepare nitric acid and to obtain the second acidic aqueous solution In an embodiment of the process according to the invention, the process comprises adding hydroxylammonium to an acidic aqueous solution comprising hydroxylammonium to obtain the first acidic aqueous solution. After said" ' adding, the resulting first acidic aqueous solution can be mixed with the second acidic aqueous solution. In another embodiment, the process according tc the invention comprises adding hydroxylammonium to the third acidic aqueous sciution during said mixing. Using the disclosure cf the present invention, the skilled man can determine the amount cf hydroxylammonium to be added to the acidic aqueous sciution that is sufficient to prevent decomposition of hydroxylammonium. It is surprising that adding extra hycroxylammonium :o a solution comprising hydroxylammonium can assist in preventing decomposition of hydroxylammonium. In an embodiment of the process according to the invention, the acidic aqueous solution tc which hydroxylammonium is added is an aqueous reaction medium leaving the cyclohexanone oxime synthesis reactor. In an embodiment, the invention provides a process comprising cycling an aqueous reaction meGium from the hydroxylammonium synthesis reactor to the cyclohexanone oxime synthesis reactor and from the cyclohexanone oxime synthesis reactor back to the hydroxylammonium synthesis reactor, the aqueous reaction medium leaving the cyclohexanone oxime synthesis reactor comprising hydroxylammonium; adding hydroxylammonium to the aqueous reaction medium leaving the cyclohexanone oxime synthesis reactor to obtain the first acidic aqueous solution; and mixing the first acidic aqueous solution with the second acidic aqueous solution. In a preferred embodiment, the aqueous reaction medium leaving the cyclohexanone oxime synthesis reactor is, optionally after having been subjected to extraction and/or separation of water from the aqueous reaction mixture by stripping, separated into at least a first part and a second part, and hydroxyiammonium is advantageously added :o the first part of the aqueous reaction medium; and nitrogen oxides are advantageously absorbed and or oxidized in the second part of the aqueous reaction medium to precare nitric acid to obtain the second acidic aqueous solution. This embodiment has ire advantage that absorption and/or oxidation of nitrogen oxides may be effected without oss of added hydroxylammonium. In a preferred embodiment, an aqueous reaction medium leaving a hydroxylammonium synthesis reactor is used to add said hydroxylammonium to an acidic aqueous soluticr. In a preferred emDOdiment, the process comprises adding pail of the aqueous readier, medium leaving the hydroxylammonium synthesis reactor tc an acidic aqueous solu::cn, preferably to the aqueous reaction medium leaving the cyclohexanone oxime synthesis reactor in such embodiments any part of the aqueous reaction medium leaving the hydroxylammonium synthesis reactor may be used to add hydroxylammonium tc said acidic aqueous reaction medium. Preferably, 1-5C % by volume, more preferac:/, 5-30 % by volume may be used. Generally, the phosphate concentration in the first acidic aqueous solution is higher than 2.3 mol/L Preferably, the phosphate concentration is such that no crystallization occurs, which depends amongst other things on the temperature and the concentration of ctrer components in the aqueous solution. Generally, the phosphate concentration in the first acidic aqueous solution is lower than 8 mcl/!, preferably lower than 5 nol/l. As used herein, the phosphate concentration is defined as the sum concentrate of all phosphates, irrespective of the form in which they are present, expressed in mot per litre of aqueous solution. Phosphates may be present as PCV"\ HP042', H2PO/, H3PO4, salts of PQ>, HPO/", HaPCV, and/or combinations thereof. Preferably, the first acidic aqueous solution comprising hydroxylammonium and phosphate is a pnesphate buffered solution. Generally, the first acidic aqueous solution comprises ammonium and/or nitrate. Any suitable acidic aqueous solution comprising nitric acid can be used as the second accic aqueous solution. The second acidic aqueous solution comprising nitric acid -ay be obtained by absorbing and oxidizing nitrogen oxides in an aqueous solution. It ;s 5;$o possible to use a concentrated nitric acid solution as the second acidic aqueous solution. Preferably such a concentrated nitric acid solution contains 30-75 °o by weight of nitric acid, in a preferred embodiment, an aqueous reaction medium lesv:-g the cyclohexanone oxime synthesis reactor is, optionally after separation of water fr:m the aqueous reaction mixture, separated into at least a first part and a second pat. and nitrogen oxides are advantageously absorbed and/or oxidized in the second part of the aqueous reaction medium to obtain, optionally after mixing with af preferably concentrated, nitric acid solution, the second acidic aqueous solution. Nitrogen oxides may be obtained from an ammonia-oxidation. The oxidation of ammonia can be represented by the following equation: 4 NH:. + 5 02 •» 4 NO 8 H20 The absorption and oxidation of nitrogen oxides in an aqueous solution to prepare nitric acid can be represented by the following equations: 2 NO + 02 -» 2 NQ2 4 N02 + 02 + 2 H20 ^ 4 HN03 3 N02 + H20 -» 2 HNO3 + NO There is no specific upper limit for the nitric acid concentration in the second acidic aqueous solution. Generally, the phosphate concentration in the third acidic aqueous solution is higher than 2.0 mol/I. Preferably, the phosphate concentration is such that no crystallization occurs, which depends amongst other things on the temperature and the concentration of other components in the third acidic aqueous solution. Generally, the phosphate concentration in the third acidic aqueous solution is iower than 8 rr.ol/!. preferably lower than 5 mol/l. As used herein, the phosphate concentration is defined as the sum concentration of ail phosphates, irrespective of the form, in which they are present, expressed in mol per litre of aqueous solution. Phosphates may be present as PO3", HP042\ H2P0A", H3PO, salts of P043', HP042\ H2P0,~, and/or combinations thereof. Preferably, the third acidic aqueous solution comprising hydroxyiammonium and phosphate is a phosphate buffered solution. Generally, the third acidic aqueous solution comprises ammonium and/or nitrate. Surprisingly, it has been found that decomposition of hydroxyiammonium in the third acidic aqueous solution may be reduced or even prevented by increasing the hydroxyiammonium concentration in the ' third acidic aqueous solution, for instance by addition of hydroxyiammonium or by enrichment of hydroxyiammonium in a hydroxyiammonium synthesis reactor There is no specific upper limit for the hydroxyiammonium concentration in the third acidic aqueous solution. Preferably, the hydroxyiammonium concentration in the third acidic aqueous solution is lower than 2.5 mol/l. The temperature of the mixture obtained as a result of said mixing, as used herein also referred to as third acidic aqueous solutions is preferably between 20 and 30 CC Preferably, the temperature of the third acidic aqueous solution is between 25 and 6C =C. The temperature may also be between 20 and 40 °C, for instance in an embodiment wherein the mixing of me first acidic aqueous solution with the second acidic aqueous solution is effected prior to Ceding the third or fourth acidic aqueous solution to the hydroxylammonium synthesis reactor. Mixing of the first acidic aqueous solution with the second acidic aqueous solution may be performed in any suitable manner, for instance by continuous merging the two acidic aqueous sciurions supplied in a continuous flow and/or by using a mixer, a flow or !ine mixer, an agitated vessel or a bubble column. The mixing may be performed with a turbine stirrer or a static mixer. After mixing the first acidic aqueous solution with the second acidic aqueous solution resulting in the third acidic aqueous solution, the concentration cf nitric acid in the third acidic aquecus solution may be further increased by mixing the third acidic aqueous solution with an acidic aqueous solution comprising nitric acid, preferably at a temperature between 20 and 80 °C, resulting in a fourth acidic aquecus solution comprising hydroxyiammonium, phosphate and nitric acid whereby the total acid concentration minus the phosphate concentration in the fourth acidic aqueous solution is lower than 0.523 * ln([hydroxylammonium]/1.25) + 422'(T + 81) wherein [hydroxylammonium] is the concentration of hydroxylammonium in the fourth acidic aqueous solution, T is the temperature of the fourth acidic aquecus solution expressed in 3C and all concentrations are expressed in mol/l. Preferably the total acid concentration in the fourth acidic aqueous solution is higher than 0.1 mot/I and lower than 6 mol/l. Generally, the phosphate concentration in the fourth acidic aqueous solution is higher than 2.0 mol/l. Preferably, the phosphate concentration is such that no crystallization occurs, which depends amongst other things on the temperature and the concentration of other components in the aqueous solution. Generally, the phosphate concentration in the fourth acidic aqueous solution is lower than 8 mol/i. preferably lower than 5 mol/L As used herein, the phosphate concentration is defined as the overall concentration of all phosphates, irrespective of the form in which they are present, expressed in mcl per litre of aqueous solution. Phosphates may be present as PCV\ HP04. H2P04", H3PO4. salts of PO/; HP042", H2P04\ and/or combinations thereof. Preferably, the fourth acidic aqueous solution comprising hydroxylammonium and phosphate is a phosphate buffered solution. Generally, the fourth acidic aqueous solution comprises ammonium and/or nitrate. The preferred upper limit ror the total acid concentration minus the phosphate ccncentraticn in the fourth acidic aqueous soiution is determined by the hydroxylammonium concentration ([hydroxylammonium]) and the temperature (T) in the fourth acidic aqueous solution. The total acid concentration minus the phosphate concentration is preferably such that it is lower than 0.523 ln([hydroxylammonium]/1.25) ■■ 422/(T.+ 31) whereby ail concentrations are expressed in moi/l, There is no specific upper limit for the hydroxylammonium concentration in the fourth acidic aqueous solution. Preferably, the hydroxylammonium concentration in the fourth acidic aqueous solution is lower than 2.5 mol/l. The temperature of the fourth acidic aqueous so'ution is preferably between 20 and 30 °C. Preferably, the temperature is between 25 and SO °C. The temperature may also ce between 20 and 40 9C, for instance in an embodiment wherein the mixing of the third acidic aqueous solution with the acidic aqueous solution comprising nitric acid is effected prior to feeding the fourth mixture to the hydroxylammonium synthesis reactor. Mixing of the third acidic aqueous solution with an acidic aqueous soiution comprising nitric acid may be performed by continuous merging the two acicic aqueous solutions supplied in a continuous flow and/or by using a mixer, a flow or line mixer, an agitated vessel or a bubble column. The mixing may be performed with a turbine stirrer or a static mixer. In preferred embodiment, the process comprises adding hydroxylammonium to the third acidic aqueous solution prior to mixing the third acidic aqueous solution with the acidic aqueous solution comprising nitric acid to form the fourth acidic aqueous solution. In a preferred embodiment, an aqueous reaction medium leaving a hydroxylammonium synthesis reactor is used to add said hydroxylammonium to the third acidic aqueous sciution. In a preferred embodiment, the process comprises adding part of the aqueous reaction medium leaving the hydroxylammonium synthesis reactor to the third acicic aqueous solution. Preferably, 1-50 % by volume, more preferably, 5-30 % by volume may be used. In an embodiment the mixing of the first and second acidic aqueous solution resulting in the third acidic aqueous solution is performed before the third acidic aqueous solution is fed to the hydroxylammonium synthesis reactor. In still another embodiment this third acidic aqueous solution is mixed with an acidic aqueous solution comprising nitric acid resulting in the fourth acidic aqueous solution before this fourth acidic aqueous solution is fed to the hydroxylammonium synthesis reactor. In another embodiment the mixing of the first acidic aqueous solution with the second acidic aqueous solution comprising nitric acid is performed in the hydroxylammonium synthesis reactor. This embodiment preferably comprises feeding the first acidic aqueous solution and the second acidic aqueous solution separately 10 the hydroxylammonium synthesis reactor. In this embodiment, the resulting third acidic aqueous solution is present in the hydroxylammonium synthesis reactor. In this embodiment, the third acidic aqueous solution is preferably enriched in hydroxylammonium in the hydroxylammonium synthesis reactor. In an embodiment, the invention provides a process comprising feeding a first acidic aqueous solution tc a hydroxylammonium synthesis reactor, said first acidic aqueous solution, comprising hydroxylammonium and phosphate-; feeding a second acidic aqueous solution to a hydroxylammonium synthesis reactor, said second acidic aqueous solution comprising nitric acid; preparing hydroxylammonium in said hydroxylammonium synthesis reactor by catalytic reduction of nitrate with hydrogen; wherein in the hydroxylammonium synthesis reactor the total acid concentration minus the phosphate concentration is lower than 0.523 ln([hydroxyiammonium]/1.25) + 422/(T + 81) whereby [hydroxylammonium] is the concentration of hydroxylammonium in the hydroxylammonium synthesis reactor, T is the temperature in the hydroxylammonium synthesis reactor expressed in °C and all concentrations are expressed in mol/I. In a preferred embodiment, the invention comprises mixing the third acidic aqueous solutior and the acidic aqueous solution comprising nitric acid in the hydroxylammonium synthesis reactor. This embodiment preferably comprises feeding the third acidic aqueous solution and the acidic aqueous solution comprising nitric acid separately to the hydroxylammonium synthesis reactor. In this embodiment, the resulting fourth acidic acueous solution is present in the hydroxylammonium synthesis reactor. In this embodiment, the fourth acidic aqueous solution is preferably enriched in hydroxylammonium in ;ne hydroxylammonium synthesis reactor. In an embodiment, the invention provides a process comprising feeding the third acidic aqueous solution to a hydroxylammonium synthesis reactor, said third acidic aqueous solution comprisir.g hydroxyiar monium and phosphate; feeding an acidic aqueous solution to a hydroxylammcnium s\ nthesis reactor said acidic aqueous solution comprisina nitric acia: preparing hydroxvlammoniurn in said hydroxylammonium synthesis reactor by ca:aiytic -eduction of n'.;rate with hydrogen; wherein in the hydroxylammonium synthesis reactor the tctai acid concentration minus the phosphate concentration is lower than 0.523 * in(>ydroxylammoniurn]/1.25) + 422/(T + 31) whereby [hydroxy.ammonium] is the concentration of hydroxylammonium in the hydroxyianmonium synthesis reactor, T is the temperature in the hydroxylammonium synthesis reactor expressed in ?C and all concentrations are expressed in mol/l. The nixing in the hydroxylammonium synthesis reactor preferably is performed by using a cubble column as a hydroxylammonium synthesis reactor. Preferably, the process according to the invention is a continuous process. Brief Description of the Drawing FIG. 1 is a schematic diagram of an embodiment of the process according to the present invention. Descriptor of an embodiment Referring to FIG. 1, A represents the hydroxylammonium raactor. B represents the cyclohexanone oxime reactor. To reactor A, containing catalyst, an acidic aqueous solution comprising hydroxylammonium, phosphate and nitric acid is fed as aqueous reaction medium through line 1 and hydrogen is fed through line 2; optionally an additional acidic aqueous solution comprising nitric acid is fed to reactor A through 'ine 3; unreacied hydrogen is discharged, with any other gases, via line 4. Ir. the hydroxylammonium reactor A, the aqueous reaction medium is enriched in hydroxylammonium. "his aqueous reaction medium being enriched in hydroxyianmonium leaves reactor A via line 5 and is cycled to the cyctohexanone oxime reactor B via lire 6. The cyclohexanone to be converted is fed to reactor B via line 7. The largest pa.-, of cyclohexanone oxime produced and dissolved in an organic solvent !s removed frcm the system via line 8. The aqueous reaction medium leaving the cyclohexanone c/ime reactor through line 9 is extracted in an extraction zone C. An extraction agent, an organic solvent, enters extraction zone C through line 10. Within extraction zone C, additional cyclohexanone oxime is removec from the aqueous reaction medium and carried out of zone C in the organic sc'vent and is fed through line 11 to zone 3. The aqueous reaction medium leaving extraction zone C through line 12 is recycled to the hydroxylammonium reactor A, through lines 13. "4, 15. and 1. A part of the aqueous reaction medium leaving the extraction zone C through line 12 is tapped for absorbing and oxidizing nitrogen oxides. This part of the aqueous reaction medium is fed through line 15 to absorption column Dr in which nitrogen oxides are absorbed, which are produced in reactor E by ammonia combustion and fed through 'ins 13 to absorption column D. In. column D nitric acid is produced from absorbed nitrogen oxides by a further reaction with water from the aqueous reaction medium. The aqusous reaction medium enriched with nitric acid passes from column D to bleaching column F through line 16. In column F residual nitrogen oxides are oxidized into nitric acid. Accordingly, the nitric acid concentration is increased in the aqueous reaction medium leaving column F through line 19. Optionally an additional amount of nitric acid can bs supplied through line 20 and mixed with the acidic aqueous solution comprising nitric acid passing through line 19. The thus obtained second acidic-aqueous solution comprising nitric acid passing through line 21 is mixed with the aqueous reaction medium passing through line 14, the first acidic aqueous solution. Optionally an additional amount of nitric acid can be supplied through line 22 and mixed with the third acidic aqueous solution passing through line 15. Subsequently the thus obtained third or fourth acidic aqueous solution is fed to the hydroxyiammoniun reactor through line 1, completing the cycle. The aqueous reaction medium passing through line 13 may be enriched with hydroxylammonium by adding an aqueous solution comprising hydroxylammonium through line 16, which may be tapped from line 5. Preferably, this process is carried cut continuously. The invention will be elucidated by the following examples, however these are not intended to limit the scope of the invention in any way. EXAMPLES !n ail examples the hydroxylammonium concentration in the acidic aqueous solution was determined by a potentiometric titration with K3Fe(CN)6, In all examoles the total acid concentration in the acidic aqueous solution was determined by titration up to the first equivalence point of H3PO4 (approx. pH 4.2) with NaOH. In all examples the phosphate concentration in the acidic aqueous solution was determined by titration with La(N03)3. In all examples decomposition of hydroxylammoniurn was monitored by monitoring gas evolution in the third acicic aqueous solution with a bubbler. Comparative Experiment A A glass reactor equipped with baffles and a turbine stirrer was filled with 40 ml of a first acidic aqueous solution, comprising per litre 0.029 mole hydroxylammoniurn, 4.51 mole phosphate, 3.52 moi ammonium and 1.51 moie nitrate, the total acid concentration being 2.67 moie oer litre. This first acidic aqueous solution was heated to 65 °C under a continuous stream of nitrogen gas ana vigorous stirring (600 rpm). After the solution has reached the desired temperature the supply of nitrogen was stopped and 30 ml of a second acidic aqueous solution, comprising per litre no hydroxylammoniurn, and 2.33 mole phosphate, 1.53 mole ammonium and 6.4^-mole nitrate, having a total acid concentration of 7.53 moie per litre, was mixed with the first acidic aqueous solution drop wise. At a certain point during the addition of the second acidic aqueous solution decomposition of hydroxylammoniurn starts, which was observed by a vigorous gas evolution. After the addition of the second acidic aqueous solution was completed and the gas evolution in the third acidic aqueous solution having a temperature of 65 °C had stopped the hydroxylammoniurn concentration in the third acidic aqueous solution was determined by titration and appeared to be 0.523 * ln([hydroxylammonium]/1.25) + 422/(T + 81) is 0.63. Thus this comparative Experiment demonstrates decomposition of hydroxylammoniurn in the case that the total acid concentration minus the phosphate concentration in the third acidic aquecus solution is higher than 0.523 * ln([hydroxyiammonium]/1 -25) + 422/(T + 81). Example I Comparative Experiment A was repeated excect :hat instead of 30 ml, 20 ml of the second acidic aqueous solution was mixed with the first acidic aquecus solution. In this case no vigorous gas evolution couid be observed. :n the third acidic aqueous solution having a temperature of 65 °C the hydroxylammcnium concentration determined by titration was 0.013 mol/l, which is equal to the calculated value of 0.09. The calculated total acid concentration minus the calculated phosphate concentration in the third acidic aquecus solution of this Example is 0.3 mol/l. The calculated value for 0.523 ln([hydroxylammonium]/1.25) + 422'(T + 81) is 0.7. Thus this example demonstrates that no decomposition of hydroxylammonium occurs in the third acidic aquecus solution when the total acid concentration minus the phosphate concentration in the third acidic aqueous solution is lower than 0.523 * in([hydroxylammomum]/1.25) + 422/(T + 31). Example II Comparative Experiment A was repeated except that the third acidic aqueous solution was heated to 35 °C. No vigorous gas evolution could be obsen/ed. In the third acidic aqueous solution the hydroxylammonium concentration determined by titration was 0,017 mol/l, which is equal to the calculated'hydroxylammonium concentration, being 0.017 mol/l. The calculated total acid concentration minus the calculated phosphate concentration in the third acidic aqueous solution cf this Examole is 1.2 mol/l. The calculated value for 0.523 * ln([hydroxylammonium]/1.25) + 422/(T ^ 31) is 1.4. Thus this Example demonstrates that no decomposition of hydroxylammonium occurs in the third acidic aqueous solution at a temperature of 35 °C when the total acia concentration minus the phosphate concentration in the third acidic aqueous solution is lower than 0.523 * ln([hydroxylanmonium]/1.25) + 422/(T + 81). Example III Comoarative Experiment A was repeated except that as first acidic aqueous solution, v/as used a solution comprising per litre 0.146 mole hydroxylammonium, 3.74 mole phosphate, 3.34 mole ammonium and 2.57 mol nitrate, the total acid concentration being 2.33 mol per litre. No vigorous gas evolution could be observed. In the third acidic aqueous solution having a temperature cf 65 5C the hydroxylammonium concentration determined by titration was 0.08 mol/l, which is equal to the calculated hydroxylammonium concentration, being 0.08 mol/l. The calculated total acid concentration minus the calculated phosphate concentration in the third acidic aqueous solution of this Example is 1.2 mol/I. The calculated value for 0.523 ■* h([hydroxyiammcnium]/1.25} ^ 422/(T + 81) is 1.5. Thus this Example demonstrates that no decomposition of hydroxylammonium occurs in the-third acidic aqueous solution when the total aciG concentration minus the phosphate concentration in the third acidic aqueous solution is lower than 0.523 * ln-([hydroxy»ammonium]/1.25) + 422/(T + 81). Examples IV-XXIV Comparative ExDeriment A was repeated except that different first and second acidic aqueous solutions and temperatures were used and that the addition of the second acidic aqueous solution was stopped at the moment gas evolution started. At that moment the amount of added second acidic aqueous solutions was determined, the total acid concentration minus the phosphate concentration in the third acidic aqueous solution was calculated, the value for 0.523 * ln([hydroxylammonium]/1.25) + 422/(T + 81)in the third acidic aqueous solution was calculated and the amount of hydroxylammonium was calculated. All data are given in Tables 1-3. These Examples show that decomposition of hydroxylammonium starts.at the point where the total acid concentration minus the phosphate concentration in the third acidic aqueous solution is equal to 0.523 * ln([hydroxylammonium]/1.25) + 422/(T + 81). Example XXV Ccroarative Experiment A was repeated except that glass reactor equipped with baffles and a turbine stirrer was filled with 75 ml of a first acidic aqueous solution, comprisirg ;s: !itre 1.58 r^oie hydroxylammonium, 3.76 mole phosphate. 3.94 mole ammonium, and 1.37 ~ole nitrate. :he total acid concentration being 0.74 mole/I. Under vigorous stirring (600 -m) a; a temperature of 30 °C 120 ml of a mixture of 6 parts of an acicic aqueous sclutic". ccmprisirg per i;:re no hydroxylammonium. 2.90 mole phosphate \ ,20 mo:e ammonium, and 6.11 rrcie nitrate, the total acid concentration being 7.70 mole per litre anc one pai: of a o5% aqueous nitre acid solution were mixed with the first acid'C aqueous solution. Ax :~s moment gas evolution started the calculated hydroxylammonium concentration in the trrd acidic acueous solution having a temperature of 50 °C was 0.61 mol/L The calculated tctal acid concen:ration minus the calculated phosphate concentration in the third acidic aqueous solution of this Example is 2.7 mol/L The calculated value for 0.523 * in([hyd"Oxylarmonium]/1.25j + 422/(T + 81) is 2.6. This Experiment demonstrates that in the third acidic aqueous solution comprising per litre 0.61 mole hydroxylammonium, obtained by mixing a ""3t acidic acueous solution with a second acidic aqueous solution which is obtained by r:xing an acicic aqueous solution comprising nitric acid and phesohate with a 65% nitric acid solution, decomposition ofhydroxylammonium starts at the moment that the total acid concentration minus the phosphate concentration in the third acidic aqueous solution is ecai to 0.522 * lr,([hydroxylammonium]/1,25) + 422/(T + 81). Example XXVI Example XXV was repeated except that for the second acidic aqueous solution a 65% aquecus nitric acid solution is used which was added drop wise to the first acidic aqueous sclutic" until gas evolution started. At the moment gas evolution stared 41 ml of the 65% aqueous nitric acid solution has been added and the calculated hydroxylammonium concentration ir. the third acidic aqueous solution having a temperature of 60 CC was 1.02 mo::. The caicuiatec total acid concentration minus the calculated phosphate concentration in the third acidic aqueous solution of this Example is 3.2 rr.cl/l. The calculated value fcr 0.523 * !n([hydroxylammonium]/1.25) + 422/(T + 31) is 2.9. This Example demonstrates that if the concentration of hydroxylammonium in the third acicic aqueous solution is 1.!2 mc'/i and the second acidic aqueous solution, being a 65% aqueous nitric acid sc'utiom is mixed crop wise with the first acidic aqueous solution no deccmpositicn occurs «nt;l the total acid concentration minus the phosphate concentration in the third acidic acueous solution is equal to 0.523 * ln([hydroxylamr.onium]/1.25) + 422/(T + 31). Comparative Experiment B Comparative Experiment A was repeated except that the glass reactor equipped with baffles and a turbine stirrer was rilled with 70 mi of a f rst acidic aqueous solution, comprising per lfire 0.020 mole hyaroxylammonium, -.55 mole phosphate, 3.32 no I ammonium, and 1,42 mcie nitrate, the totai acid concentration oeinc 2.74 mole/!. Under vigorous stirring (6G0 rprn) at a temperature of 45 °C 30 ml of a seccnd acidic aqueous solution, comprising per litre no hydroxylammonium, 7.70 mole totai acid and 2.90 mole phosphate and 5 ml of a 65% aqueous nitric acid solution were mixed with :he first acidic aqueous solution. Gas evolution was observed. After the gas evolution had stopoec the hydroxylammonium concentration in the third acidic aqueous solution was determined by titration and appeared to be Example XXVJJ Comparative Experiment B was repeated except that the hydroxylammonium concentration in the first acidic aqueous solution has been increased by adding 5 ml of an aquecus hydroxylammonium solution, comprising per litre 1.53 mole hydroxylammonium, 3.7c mole phosphate, 3,9^ mole ammonium and 1.37 mcie ni;-ate havinc a total acid concentration of 0.74 mole/I to 70 ml of a first acidic aqueous sorption comprising per litre 0.020 mole hydroxylammcnium, 4.55 mole phosphate, 3.32 mcie ammonium and 1.42 mcie nitrate having a total acid concentration cf 2.74 mole per litre. No gas evolution was observed. The calculated hydroxylammonium concentration in the third acidic aqueous solution having a temperature of 45 °C was 0.08-1 —oi/i. The calculated total acid concentration minus the calculated cnosphate concentration r :^e third acidic aqueous solution of this Example is 0.3 rnoVI and re calculated value for 0.523 - [n([hydroxyiarrmoniuT,]/1.25) + ±22/(T * 31) is 1.9. This Example demonstrates that increasing the amount of hydroxylammcrvum in the third acidic aqueous solution in such a way that the total acid concentration minus the phosphate concsnrsticn in the third acidic aqueous solution is iov/er than 0.523 * In [nydroxylammonium]/1.25 - 422'(T + 31), results in preventing decomposition of hydroxylammonium in the th 'd acidic aqueous solution. WO 2004/049326 PCTYIB2003/004990 7 CLAIMS 1. A method of recording blocks of data on an optical record carrier, said method comprising the steps of: 5 - writing a recording indication information on the optical record carrier to indicate that a recording has started, said recording indication information including a recording start address, and overwriting the recording indication information at an end of recording. 10 2. A recording method as claimed in claim 1, further comprising the step of writing a recovery header for each block recorded on the data carrier, the recovery header of a current block of data comprising a size of the current block and a location of a next block of data. 3. A recording method as claimed in claim 2, wherein the recovery header is written in a 15 private data stream. 4. A recording method as claimed in claim 1, wherein the recording indication information is written in a private data area of the record carrier. 20 5. A recording method as claimed in claim 1, wherein the recording indication information comprises a logical volume integrity descriptor. 6. A recording method as claimed in claim 1, wherein the recording indication information is stored in a recovery file on disc. 25 7. A method of recovering blocks of data recorded on an optical record carrier in case of a power failure affecting a recording and reproducing device containing said optical record carrier, said method comprising the steps of: reading a recording indication information on the optical record carrier, said 30 information indicating that a recording has been improperly stopped and including a recording start address, and parsing recorded data starting from the recording start address in order to find a * * recording end point in a last recorded data block. WO 2004/049326 PCT/IB2003/004990 8 8. A power failure recovery method as claimed in claim 7, further comprising the steps of: reading, on the optical record carrier, a recovery header associated with a recorded data block, and 5 - recovering a content of a current recorded data block and a location of a next recorded data block from a current block size and a next block pointer contained in the recovery header. 9. A recording and/or reproducing device comprising: 10 - means for writing a recording indication information on the optical record carrier to indicate that a recording has started, said recording indication information including a recording start address, - * * means for overwriting the recording indication information at an end of recording. 15 10. A recording and/or reproducing device comprising: means for reading a recording indication information on the optical record carrier, said recording indication information indicating that a recording has been improperly stopped and including a recording start address, and means for parsingjecorded data starting from the recording start address in order to 20 find a recording end point in a last recorded data block. 11. A computer program comprising program instructions for implementing a recording method as claimed in claim 1 when said program is executed by a processor. 25 12. A computer program comprising program instructions for implementing a power failure recovery method as claimed in claim 7 when said program is executed by a processor.

Full Text

PROCESS FOR MIXING AN ACIDIC AQUEOUS SOLUTION COMPRISING HYDROXYLAMMONIUM AND PHOSPHATE WITH NITRIC ACID
The invention relates to a process for mixing a first acidic aqueous solution comprising hydroxylammonium and phosphate with a second acidic aqueous solution comprising nitric acid, resulting in a third acidic aqueous solution comprising hydroxylammonium, phosphate and nitric acid.
Cydohexanone oxime can be prepared in a process in which an aqueous reaction medium is cycled from a hydroxylammonium synthesis reactor in which hydroxylammonium is prepared by catalytic reduction of nitrate with hydrogen to a cydohexanone oxime synthesis reactor in which cydohexanone oxime is produced by reaction of hydroxylammonium with cydohexanone and from the cydohexanone oxime synthesis reactor back to the hydroxylammonium synthesis reactor. To make up for the nitrate that is reduced in the hydroxylammonium synthesis reactor, nitric add can be introduced into the aqueous reaction medium by mixing a nitric acid solution with the aqueous solution leaving the cydohexanone oxime synthesis zone. The aqueous reaction medium leaving the cydohexanone oxime synthesis reactor may comprise unreached hydroxylammonium. Said unreacted'hydroxylammonium may decompose as a result of the mixing with the nitric acid solution, this decomposition being disadvantageous, as hydroxylammonium is a useful product.
CN-A-1281349 discloses the use of a static mixer for mixing both solutions. However, in the mixed solution decomposition of hydroxylammonium may stiii occur.
The object of the present invention is to provide a process for mixing a first acidic aqueous solution comprising hydroxylammonium and phosphate with a second acidic aqueous solution comprising nitric acid, resulting in a third acidic aqueous solution comprising hydroxylammonium, phosphate and nitric acid, in which decomposition of hydroxylammonium in the third acidic aqueous solution is prevented or at least reduced.
This object is achieved in that in the third acidic aqueous solution the total acid concentration minusJhe phosphate concentration is lower than

0.523 * ln([hydroxylammonium]/1.25) + 422/(T + 31) whereby [hydroxylammonium] is the concentration of hydroxylammonium in the third acidic aqueous solution, T is the temperature of the third acidic aqueous solution expressed in °C and all concentrations are expressed in mdl/!.
It has ;n particular been found that decomposition of hydroxyiammonium can be reduced or even prevented by having a hydroxylammonium concentration in the firs: and/or third acidic aqueous solution sufficiently high such that the total acid concentration minus the phosphate concentration in the third acidic aqueous solution is Icv/erthan 0.523 * ln([hydroxylammonium]/1.25) + 4221(1 + 31). Obtaining a sufficiently nigh hydroxylammonium concentration in the first acidic aqueous solution can izr example be achieved by adding hydroxyiammonium to an acidic aqueous solution comprising hydroxylammonium to obtain the first acidic aqueous solution. Obtaining a sufficiently high hydroxylammonium concentration in the third acidic aqueous solution can for example be achieved by adding hydroxylammonium to the third acidic aqueous solution and/or by performing the mixing cf the first and second acidic aqueous solution in a hydroxyiammonium reactor in which hydroxylammonium is prepared by catalytic reduction of nitrate with hydrogen.
As used herein, the total acid concentration of an acidic aqueous solution, for instance *he first, second, third and fourth acidic aqueous solution, is preferably measured by titration to a pH of 4.2. Preferably, said titration is performed by adding 5 ml of the acicic aqueous solution to 50 ml distilled water and titration-with a 0.25 N NaOH solution to a pH of 4.2. In an acidic aqueous solution comprising H3PO^ and HN03 as the acids, the total acid concentration is a measure for the sum of the concentration of H3FCU and the concentration of HNO3. Preferably the total acid concentration in the firs: acidic aqueous solution is higher than 0.1 mol/l and tower than
6 mol/l.
The process according to the invention comprises mixing a first acidic
aqueous solution with a second acidic aqueous solution. The mixture obtained as a
result of said mixing is. as used herein, also referred to as third acidic aqueous
solution.
Preferably, the process comprises mixing the first acidic aqueous solution with the second acidic aqueous solution at a temperature between 20 and 80 °C.

The first acidic aqueous solution comprises hydroxylammonium and phosphate. The'second acidic aqueous solution comprises nitric acic. Any suitable first acidic aqueous solution and a second acidic aqueous solution may be used, such that the mixing thereof results in a third acidic aqueous solution in which cacid(3)-cphGSOn5ls(3) In a preferred embodiment, the invention provides a process comprising mixing a first acidic aqueous solution comprising hydroxylammonium and phosphate with a second acidic aqueous solution comprising-nitric acid, preferably at a temperature between 20 and 80 CC. resulting in a third acidic aqueous solution
ution
and in the second acidic aqueous solution respectively, expressed in mol/l. cPhosch3te(1) and cPho5?ra:a(2) are the phosphate concentration in the first acidic aqueous solution and in the second acidic aqueous solution respectively, expressed in moi/L Chya
solution, expressed in volume of first acidic aqueous solution per second and volume of second acidic aqueous solution per second respectively. This embedment is an advantageous way for obtaining the third acidic aqueous solution according to the invention and for the prevention of decomposition of hydroxy!ammor.:um.
tn general the nydroxylammonium concentration in the first acidic aqueous solution is higher than 0.002 mol/i. for instance higher than 0.005 mol/l, for instance higher than 0.01 mol/L for instance higher than 0.02 mol/l. Typically, the hydroxylammonium concentration in the first acidic aqueous solution ::s below 2 mol/l, preferably below 0.2 mol/L
In an embodiment the process according to the invention comprises preparing hydroxylammonium oy catalytic reduction of nitrate with hydrogen in a hydroxylammonium synthesis reactor. The catalytic reduction of nitrate with hydrogen can be represented by the following equation:
2 H2P04 + NO,' + 3 H2 -» NH3OH+ + 2 H2P04_ + 2 H20
In an embodiment, the process according to the invention comprises preparing cyclohexanone oxime by reaction of hydroxylammonium and cyclohexanone in a cyclohexanone oxime synthesis reactor. The reaction of hydroxylammonium and cyclohexanone can be represented by the following equation:
NH,OH+ + HzPO; + C5H10O -» C9H10NOH + Hr;P04 + H20
In an embodiment the process according to the invention comprises cycling an aqueous reaction medium from the hydroxylammonium synthesis reactor to the cyclohexanone oxime synthesis reactor, and from the cyclohexanone oxime synthesis reactor back to the hydroxylammonium synthesis reactor
In an embodiment of the process according to the invention, an aaueous reaction medium leaving the cyclohexanone oxime synthesis reactor is usee a the first acidic aqueous solution. The use of the aqueous reaction medium leaving tne cyclohexanone oxime synthesis reactor as first acidic aqueous solution may involve a process wherein the aqueous reaction medium leaving the cyclohexanone oxime synthesis reactor is, as the first acidic aqueous medium, mixed with the second acidic aqueous solution, resulting in the third acidic aqueous solution. In an embodiment, the aoueous solution leaving the cyclohexanone oxime reactor may be subjected to

extraction prior to mixing the aqueous reaction mixture with the second acidic aqueous solution, in an embodiment, part of the water may be separated from the aqueous reaction mixture leaving the cyclohexanone oxime synthesis reactor ry stripping prior :o mixing the aqueous reaction mixture with the secona acidic aauecJS solution. In an embodiment, the aqueous reaction mixture leaving the cydohexancne oxime synthesis reactor may, optionally after extraction and/or separation of water frcm the aqueous reaction mixture, be separatea into at least a first part and a second cart, and the first parr of the aqueous reaction medium may be mixed with me second acidic aqueous solution. Nitrogen oxides may be absorbed and oxidized in said second part to prepare nitric acid and to obtain the second acidic aqueous solution
In an embodiment of the process according to the invention, the process comprises adding hydroxylammonium to an acidic aqueous solution comprising hydroxylammonium to obtain the first acidic aqueous solution. After said" ' adding, the resulting first acidic aqueous solution can be mixed with the second acidic aqueous solution. In another embodiment, the process according tc the invention comprises adding hydroxylammonium to the third acidic aqueous sciution during said mixing. Using the disclosure cf the present invention, the skilled man can determine the amount cf hydroxylammonium to be added to the acidic aqueous sciution that is sufficient to prevent decomposition of hydroxylammonium. It is surprising that adding extra hycroxylammonium :o a solution comprising hydroxylammonium can assist in preventing decomposition of hydroxylammonium. In an embodiment of the process according to the invention, the acidic aqueous solution tc which hydroxylammonium is added is an aqueous reaction medium leaving the cyclohexanone oxime synthesis reactor. In an embodiment, the invention provides a process comprising cycling an aqueous reaction meGium from the hydroxylammonium synthesis reactor to the cyclohexanone oxime synthesis reactor and from the cyclohexanone oxime synthesis reactor back to the hydroxylammonium synthesis reactor, the aqueous reaction medium leaving the cyclohexanone oxime synthesis reactor comprising hydroxylammonium; adding hydroxylammonium to the aqueous reaction medium leaving the cyclohexanone oxime synthesis reactor to obtain the first acidic aqueous solution; and mixing the first acidic aqueous solution with the second acidic aqueous solution. In a preferred embodiment, the aqueous reaction medium leaving the cyclohexanone oxime synthesis reactor is, optionally after having been subjected to extraction and/or separation of water from the aqueous reaction mixture by stripping, separated into at least a first part and a second part, and hydroxyiammonium is

advantageously added :o the first part of the aqueous reaction medium; and nitrogen oxides are advantageously absorbed and or oxidized in the second part of the aqueous reaction medium to precare nitric acid to obtain the second acidic aqueous solution. This embodiment has ire advantage that absorption and/or oxidation of nitrogen oxides may be effected without oss of added hydroxylammonium.
In a preferred embodiment, an aqueous reaction medium leaving a hydroxylammonium synthesis reactor is used to add said hydroxylammonium to an acidic aqueous soluticr. In a preferred emDOdiment, the process comprises adding pail of the aqueous readier, medium leaving the hydroxylammonium synthesis reactor tc an acidic aqueous solu::cn, preferably to the aqueous reaction medium leaving the cyclohexanone oxime synthesis reactor in such embodiments any part of the aqueous reaction medium leaving the hydroxylammonium synthesis reactor may be used to add hydroxylammonium tc said acidic aqueous reaction medium. Preferably, 1-5C % by volume, more preferac:/, 5-30 % by volume may be used.
Generally, the phosphate concentration in the first acidic aqueous solution is higher than 2.3 mol/L Preferably, the phosphate concentration is such that no crystallization occurs, which depends amongst other things on the temperature and the concentration of ctrer components in the aqueous solution. Generally, the phosphate concentration in the first acidic aqueous solution is lower than 8 mcl/!, preferably lower than 5 nol/l. As used herein, the phosphate concentration is defined as the sum concentrate of all phosphates, irrespective of the form in which they are present, expressed in mot per litre of aqueous solution. Phosphates may be present as PCV"\ HP042', H2PO/, H3PO4, salts of PQ>, HPO/", HaPCV, and/or combinations thereof. Preferably, the first acidic aqueous solution comprising hydroxylammonium and phosphate is a pnesphate buffered solution. Generally, the first acidic aqueous solution comprises ammonium and/or nitrate.
Any suitable acidic aqueous solution comprising nitric acid can be used as the second accic aqueous solution. The second acidic aqueous solution comprising nitric acid -ay be obtained by absorbing and oxidizing nitrogen oxides in an aqueous solution. It ;s 5;$o possible to use a concentrated nitric acid solution as the second acidic aqueous solution. Preferably such a concentrated nitric acid solution contains 30-75 °o by weight of nitric acid, in a preferred embodiment, an aqueous reaction medium lesv:-g the cyclohexanone oxime synthesis reactor is, optionally after separation of water fr:m the aqueous reaction mixture, separated into at least a first part and a second pat. and nitrogen oxides are advantageously absorbed and/or

oxidized in the second part of the aqueous reaction medium to obtain, optionally after mixing with af preferably concentrated, nitric acid solution, the second acidic aqueous solution.
Nitrogen oxides may be obtained from an ammonia-oxidation. The oxidation of ammonia can be represented by the following equation:
4 NH:. + 5 02 •» 4 NO * 8 H20
The absorption and oxidation of nitrogen oxides in an aqueous solution to prepare nitric acid can be represented by the following equations:
2 NO + 02 -» 2 NQ2
4 N02 + 02 + 2 H20 ^ 4 HN03
3 N02 + H20 -» 2 HNO3 + NO
There is no specific upper limit for the nitric acid concentration in the second acidic aqueous solution.
Generally, the phosphate concentration in the third acidic aqueous solution is higher than 2.0 mol/I. Preferably, the phosphate concentration is such that no crystallization occurs, which depends amongst other things on the temperature and the concentration of other components in the third acidic aqueous solution. Generally, the phosphate concentration in the third acidic aqueous solution is iower than 8 rr.ol/!. preferably lower than 5 mol/l. As used herein, the phosphate concentration is defined as the sum concentration of ail phosphates, irrespective of the form, in which they are present, expressed in mol per litre of aqueous solution. Phosphates may be present as PO*3", HP042\ H2P0A", H3PO*, salts of P043', HP042\ H2P0,~, and/or combinations thereof. Preferably, the third acidic aqueous solution comprising hydroxyiammonium and phosphate is a phosphate buffered solution. Generally, the third acidic aqueous solution comprises ammonium and/or nitrate. Surprisingly, it has been found that decomposition of hydroxyiammonium in the third acidic aqueous solution may be reduced or even prevented by increasing the hydroxyiammonium concentration in the ' third acidic aqueous solution, for instance by addition of hydroxyiammonium or by enrichment of hydroxyiammonium in a hydroxyiammonium synthesis reactor
There is no specific upper limit for the hydroxyiammonium concentration in the third acidic aqueous solution. Preferably, the hydroxyiammonium

concentration in the third acidic aqueous solution is lower than 2.5 mol/l.
The temperature of the mixture obtained as a result of said mixing, as used herein also referred to as third acidic aqueous solutions is preferably between 20 and 30 CC Preferably, the temperature of the third acidic aqueous solution is between 25 and 6C =C. The temperature may also be between 20 and 40 °C, for instance in an embodiment wherein the mixing of me first acidic aqueous solution with the second acidic aqueous solution is effected prior to Ceding the third or fourth acidic aqueous solution to the hydroxylammonium synthesis reactor.
Mixing of the first acidic aqueous solution with the second acidic aqueous solution may be performed in any suitable manner, for instance by continuous merging the two acidic aqueous sciurions supplied in a continuous flow and/or by using a mixer, a flow or !ine mixer, an agitated vessel or a bubble column. The mixing may be performed with a turbine stirrer or a static mixer.
After mixing the first acidic aqueous solution with the second acidic aqueous solution resulting in the third acidic aqueous solution, the concentration cf nitric acid in the third acidic aquecus solution may be further increased by mixing the third acidic aqueous solution with an acidic aqueous solution comprising nitric acid, preferably at a temperature between 20 and 80 °C, resulting in a fourth acidic aquecus solution comprising hydroxyiammonium, phosphate and nitric acid whereby the total acid concentration minus the phosphate concentration in the fourth acidic aqueous solution is lower than 0.523 * ln([hydroxylammonium]/1.25) + 422'(T + 81) wherein [hydroxylammonium] is the concentration of hydroxylammonium in the fourth acidic aqueous solution, T is the temperature of the fourth acidic aquecus solution expressed in 3C and all concentrations are expressed in mol/l.
Preferably the total acid concentration in the fourth acidic aqueous solution is higher than 0.1 mot/I and lower than 6 mol/l.
Generally, the phosphate concentration in the fourth acidic aqueous solution is higher than 2.0 mol/l. Preferably, the phosphate concentration is such that no crystallization occurs, which depends amongst other things on the temperature and the concentration of other components in the aqueous solution. Generally, the phosphate concentration in the fourth acidic aqueous solution is lower than 8 mol/i. preferably lower than 5 mol/L As used herein, the phosphate concentration is defined as the overall concentration of all phosphates, irrespective of the form in which they are present, expressed in mcl per litre of aqueous solution. Phosphates may be present as

PCV\ HP04*. H2P04", H3PO4. salts of PO/; HP042", H2P04\ and/or combinations thereof. Preferably, the fourth acidic aqueous solution comprising hydroxylammonium and phosphate is a phosphate buffered solution. Generally, the fourth acidic aqueous solution comprises ammonium and/or nitrate.
The preferred upper limit ror the total acid concentration minus the phosphate ccncentraticn in the fourth acidic aqueous soiution is determined by the hydroxylammonium concentration ([hydroxylammonium]) and the temperature (T) in the fourth acidic aqueous solution. The total acid concentration minus the phosphate concentration is preferably such that it is lower than
0.523 * ln([hydroxylammonium]/1.25) ■*■ 422/(T.+ 31) whereby ail concentrations are expressed in moi/l,
There is no specific upper limit for the hydroxylammonium concentration in the fourth acidic aqueous solution. Preferably, the hydroxylammonium concentration in the fourth acidic aqueous solution is lower than 2.5 mol/l.
The temperature of the fourth acidic aqueous so'ution is preferably between 20 and 30 °C. Preferably, the temperature is between 25 and SO °C. The temperature may also ce between 20 and 40 9C, for instance in an embodiment wherein the mixing of the third acidic aqueous solution with the acidic aqueous solution comprising nitric acid is effected prior to feeding the fourth mixture to the hydroxylammonium synthesis reactor.
Mixing of the third acidic aqueous solution with an acidic aqueous soiution comprising nitric acid may be performed by continuous merging the two acicic aqueous solutions supplied in a continuous flow and/or by using a mixer, a flow or line mixer, an agitated vessel or a bubble column. The mixing may be performed with a turbine stirrer or a static mixer.
In preferred embodiment, the process comprises adding hydroxylammonium to the third acidic aqueous solution prior to mixing the third acidic aqueous solution with the acidic aqueous solution comprising nitric acid to form the fourth acidic aqueous solution.
In a preferred embodiment, an aqueous reaction medium leaving a hydroxylammonium synthesis reactor is used to add said hydroxylammonium to the third acidic aqueous sciution. In a preferred embodiment, the process comprises adding part of the aqueous reaction medium leaving the hydroxylammonium synthesis reactor to the third acicic aqueous solution. Preferably, 1-50 % by volume, more

preferably, 5-30 % by volume may be used.
In an embodiment the mixing of the first and second acidic aqueous solution resulting in the third acidic aqueous solution is performed before the third acidic aqueous solution is fed to the hydroxylammonium synthesis reactor. In still another embodiment this third acidic aqueous solution is mixed with an acidic aqueous solution comprising nitric acid resulting in the fourth acidic aqueous solution before this fourth acidic aqueous solution is fed to the hydroxylammonium synthesis reactor.
In another embodiment the mixing of the first acidic aqueous solution with the second acidic aqueous solution comprising nitric acid is performed in the hydroxylammonium synthesis reactor. This embodiment preferably comprises feeding the first acidic aqueous solution and the second acidic aqueous solution separately 10 the hydroxylammonium synthesis reactor. In this embodiment, the resulting third acidic aqueous solution is present in the hydroxylammonium synthesis reactor. In this embodiment, the third acidic aqueous solution is preferably enriched in hydroxylammonium in the hydroxylammonium synthesis reactor. In an embodiment, the invention provides a process comprising feeding a first acidic aqueous solution tc a hydroxylammonium synthesis reactor, said first acidic aqueous solution, comprising hydroxylammonium and phosphate-; feeding a second acidic aqueous solution to a hydroxylammonium synthesis reactor, said second acidic aqueous solution comprising nitric acid; preparing hydroxylammonium in said hydroxylammonium synthesis reactor by catalytic reduction of nitrate with hydrogen; wherein in the hydroxylammonium synthesis reactor the total acid concentration minus the phosphate concentration is lower than 0.523 * ln([hydroxyiammonium]/1.25) + 422/(T + 81) whereby [hydroxylammonium] is the concentration of hydroxylammonium in the hydroxylammonium synthesis reactor, T is the temperature in the hydroxylammonium synthesis reactor expressed in °C and all concentrations are expressed in mol/I.
In a preferred embodiment, the invention comprises mixing the third acidic aqueous solutior and the acidic aqueous solution comprising nitric acid in the hydroxylammonium synthesis reactor. This embodiment preferably comprises feeding the third acidic aqueous solution and the acidic aqueous solution comprising nitric acid separately to the hydroxylammonium synthesis reactor. In this embodiment, the resulting fourth acidic acueous solution is present in the hydroxylammonium synthesis reactor. In this embodiment, the fourth acidic aqueous solution is preferably enriched in hydroxylammonium in ;ne hydroxylammonium synthesis reactor. In an embodiment,

the invention provides a process comprising feeding the third acidic aqueous solution to a hydroxylammonium synthesis reactor, said third acidic aqueous solution comprisir.g hydroxyiar monium and phosphate; feeding an acidic aqueous solution to a hydroxylammcnium s\ nthesis reactor said acidic aqueous solution comprisina nitric acia: preparing hydroxvlammoniurn in said hydroxylammonium synthesis reactor by ca:aiytic -eduction of n'.;rate with hydrogen; wherein in the hydroxylammonium synthesis reactor the tctai acid concentration minus the phosphate concentration is lower than 0.523 * in(>ydroxylammoniurn]/1.25) + 422/(T + 31) whereby [hydroxy.ammonium] is the concentration of hydroxylammonium in the hydroxyianmonium synthesis reactor, T is the temperature in the hydroxylammonium synthesis reactor expressed in ?C and all concentrations are expressed in mol/l.
The nixing in the hydroxylammonium synthesis reactor preferably is performed by using a cubble column as a hydroxylammonium synthesis reactor.
Preferably, the process according to the invention is a continuous process.
Brief Description of the Drawing
FIG. 1 is a schematic diagram of an embodiment of the process according to the present invention.
Descriptor of an embodiment
Referring to FIG. 1, A represents the hydroxylammonium raactor. B represents the cyclohexanone oxime reactor. To reactor A, containing catalyst, an acidic aqueous solution comprising hydroxylammonium, phosphate and nitric acid is fed as aqueous reaction medium through line 1 and hydrogen is fed through line 2; optionally an additional acidic aqueous solution comprising nitric acid is fed to reactor A through 'ine 3; unreacied hydrogen is discharged, with any other gases, via line 4. Ir. the hydroxylammonium reactor A, the aqueous reaction medium is enriched in hydroxylammonium. "his aqueous reaction medium being enriched in hydroxyianmonium leaves reactor A via line 5 and is cycled to the cyctohexanone oxime reactor B via lire 6. The cyclohexanone to be converted is fed to reactor B via line 7. The largest pa.-, of cyclohexanone oxime produced and dissolved in an organic solvent !s removed frcm the system via line 8. The aqueous reaction medium leaving the cyclohexanone c/ime reactor through line 9 is extracted in an extraction zone C.

An extraction agent, an organic solvent, enters extraction zone C through line 10. Within extraction zone C, additional cyclohexanone oxime is removec from the aqueous reaction medium and carried out of zone C in the organic sc'vent and is fed through line 11 to zone 3.
The aqueous reaction medium leaving extraction zone C through line 12 is recycled to the hydroxylammonium reactor A, through lines 13. "4, 15. and 1. A part of the aqueous reaction medium leaving the extraction zone C through line 12 is tapped for absorbing and oxidizing nitrogen oxides. This part of the aqueous reaction medium is fed through line 15 to absorption column Dr in which nitrogen oxides are absorbed, which are produced in reactor E by ammonia combustion and fed through 'ins 13 to absorption column D. In. column D nitric acid is produced from absorbed nitrogen oxides by a further reaction with water from the aqueous reaction medium. The aqusous reaction medium enriched with nitric acid passes from column D to bleaching column F through line 16. In column F residual nitrogen oxides are oxidized into nitric acid. Accordingly, the nitric acid concentration is increased in the aqueous reaction medium leaving column F through line 19. Optionally an additional amount of nitric acid can bs supplied through line 20 and mixed with the acidic aqueous solution comprising nitric acid passing through line 19. The thus obtained second acidic-aqueous solution comprising nitric acid passing through line 21 is mixed with the aqueous reaction medium passing through line 14, the first acidic aqueous solution. Optionally an additional amount of nitric acid can be supplied through line 22 and mixed with the third acidic aqueous solution passing through line 15. Subsequently the thus obtained third or fourth acidic aqueous solution is fed to the hydroxyiammoniun reactor through line 1, completing the cycle. The aqueous reaction medium passing through line 13 may be enriched with hydroxylammonium by adding an aqueous solution comprising hydroxylammonium through line 16, which may be tapped from line 5.
Preferably, this process is carried cut continuously. The invention will be elucidated by the following examples, however these are not intended to limit the scope of the invention in any way.
EXAMPLES
!n ail examples the hydroxylammonium concentration in the acidic aqueous solution was determined by a potentiometric titration with K3Fe(CN)6,
In all examoles the total acid concentration in the acidic aqueous solution was determined by titration up to the first equivalence point of H3PO4 (approx.

pH 4.2) with NaOH.
In all examples the phosphate concentration in the acidic aqueous solution was determined by titration with La(N03)3.
In all examples decomposition of hydroxylammoniurn was monitored by monitoring gas evolution in the third acicic aqueous solution with a bubbler.
Comparative Experiment A
A glass reactor equipped with baffles and a turbine stirrer was filled with 40 ml of a first acidic aqueous solution, comprising per litre 0.029 mole hydroxylammoniurn, 4.51 mole phosphate, 3.52 moi ammonium and 1.51 moie nitrate, the total acid concentration being 2.67 moie oer litre. This first acidic aqueous solution was heated to 65 °C under a continuous stream of nitrogen gas ana vigorous stirring (600 rpm). After the solution has reached the desired temperature the supply of nitrogen was stopped and 30 ml of a second acidic aqueous solution, comprising per litre no hydroxylammoniurn, and 2.33 mole phosphate, 1.53 mole ammonium and 6.4^-mole nitrate, having a total acid concentration of 7.53 moie per litre, was mixed with the first acidic aqueous solution drop wise. At a certain point during the addition of the second acidic aqueous solution decomposition of hydroxylammoniurn starts, which was observed by a vigorous gas evolution. After the addition of the second acidic aqueous solution was completed and the gas evolution in the third acidic aqueous solution having a temperature of 65 °C had stopped the hydroxylammoniurn concentration in the third acidic aqueous solution was determined by titration and appeared to be 0.523 * ln([hydroxylammonium]/1.25) + 422/(T + 81) is 0.63. Thus this comparative Experiment demonstrates decomposition of hydroxylammoniurn in the case that the total acid concentration minus the phosphate concentration in the third acidic aquecus solution is higher than 0.523 * ln([hydroxyiammonium]/1 -25) + 422/(T + 81).

Example I
Comparative Experiment A was repeated excect :hat instead of 30 ml, 20 ml of the second acidic aqueous solution was mixed with the first acidic aquecus solution. In this case no vigorous gas evolution couid be observed. :n the third acidic aqueous solution having a temperature of 65 °C the hydroxylammcnium concentration determined by titration was 0.013 mol/l, which is equal to the calculated value of 0.0*9. The calculated total acid concentration minus the calculated phosphate concentration in the third acidic aquecus solution of this Example is 0.3 mol/l. The calculated value for 0.523 * ln([hydroxylammonium]/1.25) + 422'(T + 81) is 0.7. Thus this example demonstrates that no decomposition of hydroxylammonium occurs in the third acidic aquecus solution when the total acid concentration minus the phosphate concentration in the third acidic aqueous solution is lower than 0.523 * in([hydroxylammomum]/1.25) + 422/(T + 31).
Example II
Comparative Experiment A was repeated except that the third acidic aqueous solution was heated to 35 °C. No vigorous gas evolution could be obsen/ed. In the third acidic aqueous solution the hydroxylammonium concentration determined by titration was 0,017 mol/l, which is equal to the calculated'hydroxylammonium concentration, being 0.017 mol/l. The calculated total acid concentration minus the calculated phosphate concentration in the third acidic aqueous solution cf this Examole is 1.2 mol/l. The calculated value for 0.523 * ln([hydroxylammonium]/1.25) + 422/(T ^ 31) is 1.4. Thus this Example demonstrates that no decomposition of hydroxylammonium occurs in the third acidic aqueous solution at a temperature of 35 °C when the total acia concentration minus the phosphate concentration in the third acidic aqueous solution is lower than 0.523 * ln([hydroxylanmonium]/1.25) + 422/(T + 81).
Example III
Comoarative Experiment A was repeated except that as first acidic aqueous solution, v/as used a solution comprising per litre 0.146 mole hydroxylammonium, 3.74 mole phosphate, 3.34 mole ammonium and 2.57 mol nitrate, the total acid concentration being 2.33 mol per litre. No vigorous gas evolution could be observed. In the third acidic aqueous solution having a temperature cf 65 5C the

hydroxylammonium concentration determined by titration was 0.08 mol/l, which is equal to the calculated hydroxylammonium concentration, being 0.08 mol/l. The calculated total acid concentration minus the calculated phosphate concentration in the third acidic aqueous solution of this Example is 1.2 mol/I. The calculated value for 0.523 ■* h([hydroxyiammcnium]/1.25} ^ 422/(T + 81) is 1.5. Thus this Example demonstrates that no decomposition of hydroxylammonium occurs in the-third acidic aqueous solution when the total aciG concentration minus the phosphate concentration in the third acidic aqueous solution is lower than 0.523 * ln-([hydroxy»ammonium]/1.25) + 422/(T + 81).
Examples IV-XXIV
Comparative ExDeriment A was repeated except that different first and second acidic aqueous solutions and temperatures were used and that the addition of the second acidic aqueous solution was stopped at the moment gas evolution started. At that moment the amount of added second acidic aqueous solutions was determined, the total acid concentration minus the phosphate concentration in the third acidic aqueous solution was calculated, the value for 0.523 * ln([hydroxylammonium]/1.25) + 422/(T + 81)in the third acidic aqueous solution was calculated and the amount of hydroxylammonium was calculated. All data are given in Tables 1-3. These Examples show that decomposition of hydroxylammonium starts.at the point where the total acid concentration minus the phosphate concentration in the third acidic aqueous solution is equal to 0.523 * ln([hydroxylammonium]/1.25) + 422/(T + 81).

Example XXV
Ccroarative Experiment A was repeated except that glass reactor equipped with baffles and a turbine stirrer was filled with 75 ml of a first acidic aqueous solution, comprisirg ;s: !itre 1.58 r^oie hydroxylammonium, 3.76 mole phosphate. 3.94 mole ammonium, and 1.37 ~ole nitrate. :he total acid concentration being 0.74 mole/I. Under vigorous stirring (600 -m) a; a temperature of 30 °C 120 ml of a mixture of 6 parts of an acicic aqueous sclutic". ccmprisirg per i;:re no hydroxylammonium. 2.90 mole phosphate \ ,20 mo:e ammonium, and 6.11 rrcie nitrate, the total acid concentration being 7.70 mole per litre anc one pai: of a o5% aqueous nitre acid solution were mixed with the first acid'C aqueous solution. Ax :~s moment gas evolution started the calculated hydroxylammonium concentration in the trrd acidic acueous solution having a temperature of 50 °C was 0.61 mol/L The calculated tctal acid concen:ration minus the calculated phosphate concentration in the third acidic aqueous solution of this Example is 2.7 mol/L The calculated value for 0.523 * in([hyd"Oxylarmonium]/1.25j + 422/(T + 81) is 2.6. This Experiment demonstrates that in the third acidic aqueous solution comprising per litre 0.61 mole hydroxylammonium, obtained by mixing a ""3t acidic acueous solution with a second acidic aqueous solution which is obtained by r:xing an acicic aqueous solution comprising nitric acid and phesohate with a 65% nitric acid solution, decomposition ofhydroxylammonium starts at the moment that the total acid concentration minus the phosphate concentration in the third acidic aqueous solution is ecai to 0.522 * lr,([hydroxylammonium]/1,25) + 422/(T + 81).
Example XXVI
Example XXV was repeated except that for the second acidic aqueous solution a 65% aquecus nitric acid solution is used which was added drop wise to the first acidic aqueous sclutic" until gas evolution started. At the moment gas evolution stared 41 ml of the 65% aqueous nitric acid solution has been added and the calculated hydroxylammonium concentration ir. the third acidic aqueous solution having a temperature of 60 CC was 1.02 mo::. The caicuiatec total acid concentration minus the calculated phosphate concentration in the third acidic aqueous solution of this Example is 3.2 rr.cl/l. The calculated value fcr 0.523 * !n([hydroxylammonium]/1.25) + 422/(T + 31) is 2.9. This Example demonstrates that if the concentration of hydroxylammonium in the third acicic aqueous solution is 1.!2 mc'/i and the second acidic aqueous solution, being a 65% aqueous nitric acid sc'utiom is mixed crop wise with the first acidic aqueous solution no deccmpositicn occurs «nt;l the total acid concentration minus the phosphate concentration in

the third acidic acueous solution is equal to 0.523 * ln([hydroxylamr.onium]/1.25) + 422/(T + 31).
Comparative Experiment B
Comparative Experiment A was repeated except that the glass reactor equipped with baffles and a turbine stirrer was rilled with 70 mi of a f rst acidic aqueous solution, comprising per lfire 0.020 mole hyaroxylammonium, -.55 mole phosphate, 3.32 no I ammonium, and 1,42 mcie nitrate, the totai acid concentration oeinc 2.74 mole/!. Under vigorous stirring (6G0 rprn) at a temperature of 45 °C 30 ml of a seccnd acidic aqueous solution, comprising per litre no hydroxylammonium, 7.70 mole totai acid and 2.90 mole phosphate and 5 ml of a 65% aqueous nitric acid solution were mixed with :he first acidic aqueous solution. Gas evolution was observed. After the gas evolution had stopoec the hydroxylammonium concentration in the third acidic aqueous solution was determined by titration and appeared to be Example XXVJJ
Comparative Experiment B was repeated except that the hydroxylammonium concentration in the first acidic aqueous solution has been increased by adding 5 ml of an aquecus hydroxylammonium solution, comprising per litre 1.53 mole hydroxylammonium, 3.7c mole phosphate, 3,9^ mole ammonium and 1.37 mcie ni;-ate havinc a total acid concentration of 0.74 mole/I to 70 ml of a first acidic aqueous sorption comprising per litre 0.020 mole hydroxylammcnium, 4.55 mole phosphate, 3.32 mcie ammonium and 1.42 mcie nitrate having a total acid concentration cf 2.74 mole per litre. No

gas evolution was observed. The calculated hydroxylammonium concentration in the third acidic aqueous solution having a temperature of 45 °C was 0.08-1 —oi/i. The calculated total acid concentration minus the calculated cnosphate concentration r :^e third acidic aqueous solution of this Example is 0.3 rnoVI and re calculated value for
0.523 - [n([hydroxyiarrmoniuT,]/1.25) + ±22/(T * 31) is 1.9. This Example demonstrates that increasing the amount of hydroxylammcrvum in the third acidic aqueous solution in such a way that the total acid concentration minus the phosphate concsnrsticn in the third acidic aqueous solution is iov/er than 0.523 * In [nydroxylammonium]/1.25 - 422'(T + 31), results in preventing decomposition of hydroxylammonium in the th 'd acidic aqueous solution.

WO 2004/049326 PCTYIB2003/004990
7
CLAIMS
1. A method of recording blocks of data on an optical record carrier, said method
comprising the steps of:
5 - writing a recording indication information on the optical record carrier to indicate that
a recording has started, said recording indication information including a recording start address, and
overwriting the recording indication information at an end of recording.
10 2. A recording method as claimed in claim 1, further comprising the step of writing a recovery header for each block recorded on the data carrier, the recovery header of a current block of data comprising a size of the current block and a location of a next block of data.
3. A recording method as claimed in claim 2, wherein the recovery header is written in a
15 private data stream.
4. A recording method as claimed in claim 1, wherein the recording indication
information is written in a private data area of the record carrier.
20 5. A recording method as claimed in claim 1, wherein the recording indication information comprises a logical volume integrity descriptor.
6. A recording method as claimed in claim 1, wherein the recording indication
information is stored in a recovery file on disc.
25
7. A method of recovering blocks of data recorded on an optical record carrier in case of
a power failure affecting a recording and reproducing device containing said optical record
carrier, said method comprising the steps of:
reading a recording indication information on the optical record carrier, said 30 information indicating that a recording has been improperly stopped and including a recording start address, and
parsing recorded data starting from the recording start address in order to find a * *
recording end point in a last recorded data block.

WO 2004/049326 PCT/IB2003/004990
8
8. A power failure recovery method as claimed in claim 7, further comprising the steps
of:
reading, on the optical record carrier, a recovery header associated with a recorded
data block, and
5 - recovering a content of a current recorded data block and a location of a next recorded
data block from a current block size and a next block pointer contained in the recovery header.
9. A recording and/or reproducing device comprising:
10 - means for writing a recording indication information on the optical record carrier to
indicate that a recording has started, said recording indication information including a recording start address, - * * means for overwriting the recording indication information at an end of recording.
15 10. A recording and/or reproducing device comprising:
means for reading a recording indication information on the optical record carrier, said recording indication information indicating that a recording has been improperly stopped and including a recording start address, and
means for parsingjecorded data starting from the recording start address in order to 20 find a recording end point in a last recorded data block.
11. A computer program comprising program instructions for implementing a recording method as claimed in claim 1 when said program is executed by a processor.
25 12. A computer program comprising program instructions for implementing a power
failure recovery method as claimed in claim 7 when said program is executed by a processor.

Documents:

1198-chenp-2005-abstract.pdf

1198-chenp-2005-claims.pdf

1198-chenp-2005-correspondnece-others.pdf

1198-chenp-2005-correspondnece-po.pdf

1198-chenp-2005-description(complete).pdf

1198-chenp-2005-drawings.pdf

1198-chenp-2005-form 1.pdf

1198-chenp-2005-form 26.pdf

1198-chenp-2005-form 3.pdf

1198-chenp-2005-form 5.pdf

1198-chenp-2005-form18.pdf

1198-chenp-2005-pct.pdf

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Patent Number

219843

Indian Patent Application Number

1198/CHENP/2005

PG Journal Number

27/2008

Publication Date

04-Jul-2008

Grant Date

13-May-2008

Date of Filing

10-Jun-2005

Name of Patentee

DSM IP ASSETS B.V

Applicant Address

HET OVERLOON 1, 6411 TE HEERLEN,

Inventors:

#	Inventor's Name	Inventor's Address
1	OEVERING, HENDRIK
2	BENNEKER, ARNO, HERALD

PCT International Classification Number

C01B 21/14

PCT International Application Number

PCT/NL03/00877

PCT International Filing date

2003-12-10

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	02080204.7	2002-12-11	EUROPEAN UNION