Indian Patents. 222295:A PROCESS FOR THE REMOVAL OF METAL CARBONYL FROM A GASEOUS STREAM CONTAINING WATER AND HYDROGEN SULPHIDE

Title of Invention	A PROCESS FOR THE REMOVAL OF METAL CARBONYL FROM A GASEOUS STREAM CONTAINING WATER AND HYDROGEN SULPHIDE
Abstract	This invention relates to a process for the removal of metal carbonyl from a gaseous stream containing water and hydrogen sulphide. This gaseous stream is allowed to contact a hydrophobic crystalline, porous adsorbent with an accessible pore volume for pore sizes between 0.55 and 4 nm of at least 0.005 ml/g for such removal.

Full Text	The present invention relates to a process for the removal ox metal carbonyl from a gaseous stream such as synthesis gas using an adsorbent. The presence of metal carbonyls in synthesis gas which is used as feedstock for industrial processes catalysed by catalysts, poses severe problems. The catalysts can be poisoned by metal carbonyls or their decomposition products and as a consequence perform less. During the production of synthesis gas from the partial oxidation of hydrocarbon containing material such as natural gas, oil and coal in a gasification plant, not only carbon monoxide and hydrogen are formed but also amounts of hydrogen sulphide and, albeit in smaller quantities carbonyl compounds of nickel and iron. Under conditions prevailing in gasification plants carbon monoxide can react with iron and nickel surfaces and with iron and nickel present in the feed of the process to give the corresponding metal carbonyls. Iron carbonyl is often formed by the reaction of carbon monoxide with steel materials in the process equipment. Also metal carbonyls can be formed when gases are transported or stored in metal containers. Nickel tetracarbonyl and iron pentacarbonyl, especially in combination with hydrogen sulphide, can cause serious problems during treatment of raw synthesis gas, mainly due to thermal and/or chemical carbonyl decomposition. The term nraw synthesis gas' refers to the effluent gas from the gasification reactor consisting mainly of CO and H2 (up to 95 %v) , the remainder being water, CO2/ N2> hydrogen sulphide and traces of COS, CH4 and NH3. Synthesis gas produced using steam-methane reforming or autotherma* reforming instead of using oil or coal gasification, may also be treated similarly as the raw synthesis gas produced by gasification is treated. Pressure build-ups downstream frcm the gasification reactor may occur, as metal (sulphide' is being deposited on catalysts used in synthesis gas treating processes, such as COS hydrolysis and the water shift reaction. The term "water shift reaction" refers to the conversion of CO and H2O to H2 and CO2, i.e. the catalytic reaction between carbon monoxide and water in wnich each molecule of carbon monoxide is replaced by a molecule of hydrogen according the following equation CO + H2O > H2 + CO2- This reaction is also referred to as "the CO Shift Conversion" . Also in Claus plants metal carbonyls can cause problems. For example, if cryogenic methanol is used as a liquid adsorbent for the removal of acid gases, such as hydrogen sulphide and carbon dioxide (as in the Rectisol process) in combination with the Claus plant, deposition of metal oxides and/or metal sulphides can be expected throughout the Claus plant. Part of the carbonyls that cannot be converted by the treating process (e.g. the Rectisol process or other treating processes such as the Selexol process, the Purisol process or the Sulfinol process) will enter the Claus process and gives iron sulphide and nickel sulphide formation in the first catalyst bed. Furthermore in the treating processes as mentioned before sulphides my be formed giving fouling problems. The "Claus process" is a process for the manufacture of sulphur from hydrogen sulphide comprising oxidation of part of the hydrogen sulphide to S02 in a thermal reaction stage, followed by the catalytic reaction of the remaining hydrogen sulphide with the SO2 formed to give elemental sulphur in accordance with the following equation 2H2S + SO2 > 3S + 2H2O. The "Rectisol process" is a process for desulphurisation and removal of CO2. It. is a physical washing system which uses cold (cryogenic) methanol (about -30 °C) as its solvent. Both hyarogen sulphide and COS are washed out of the incoming raw synthesis gas with the cold methanol. The "Sulfinol process" is a process for the removal of, amongst others, hydrogen sulphide and/or CO2/ which process is well known to the man skilled in the art and is for example defined and described in Oil & Gas Journal, 89 (33) (1991), pp. 57-59. The "Purisol process" is a process for the removal of H2S and to a lesser extent CO2 from natural gas and syngas. A description of the process can be found in Kohl and Riesenfeld "Gas Purification", 4th Ed., Gulf Publ. Comp., Houston, London, Paris, Tokyo 1985 ISBN 0-87201-314-6, p. 851. Furthermore nickel tetracarbonyl and iron pentacarbonyl are toxic already in low concentrations (MAC value 0.05 ppmv). For these reasons it is important that metal carbonyls can be effectively removed from gaseous streams. Given the fact that during normal operation of a gasification plant several tons of iron carbonyl and nickel carbonyl per year are produced, the metal carbonyl problem is a sizeable one. US 5451384 describes a process for reducing the content of metal carbonyls in gas streams by contacting the gas stream with lead oxide, PbO, dispersed upon a support. The catalyst poisoning problem of metal carbonyls is extensively discussed therein. As suitable supports for the lead oxide zeolites (crystalline silica aluminas) and aluminas are mentioned. For the removal of Fe(C0)5 from a CO gas PbO/gamma-alumir.a is used in an example. The pore volume of this adscrrent is 0.42 cm^/g. In an other example Fe(C0)5 is removeci from synthesis gas. In this example the same PbO/gamma-alumina is used as adsorbent as the one specified above. In US 5451384 it is stated that sulphur will preferably already have been removed from the gas to be treated p:;:r to contact with the metal carbonyl trap. As reason is uven the fact that it is known that sulphur compounds sucr. as H2S will poison the catalyst used in processes lownstream of the metal carbonyl trap. Further it is mentioned that certain sulphur compounds will compete with tr.o removal of metal carbonyls from the gas stream. In Sep. Sci. and Techn. 26 (12), pp. 1559-1574, 1991 (by Bhatt, B.L., et al.) and Ind. Enc. Chem. Res.f 30 pp. 502-50, 1991 (by Golden T.C. at al) , a process is described for the removal of metal carbonyl from gas, such as synthesis gas, in which the gas is contacted with zeolite. The process described therein is carried out in the absence of hydrogen sulphide. A method for the removal of iron pentacarbonyl and/or nickel carbonyl from hydrogen sulphide containing gas streams has been described in EP 023911 A2. According to this patent application a gas stream containing hydrogen sulphide up to 5 vol.% is led over a fixed adsorption bed consisting of zinc sulphide and zinc cxide. The adsorption bed reduces the iron carbonyl content of the gas stream by 99%, whereas the nickel -arbonyl content of the gas stream is lowered by 77% only. This may indicate a relatively low adsorption capacity for nickel carbonyl and/or a contact time limitation and as a consequence forms a constraint on the use of this adsorbent. As can be deduced from the prior art, it is very difficult to remove iron pentacarbonyl and nickel tetracarbonyl from gas streams which contain both water and hydrogen sulphide. Further it has seen found (ref.: Example 2 hereafter) that porous inorganic substances have relatively low adsorption capacity for metal carbonyl, especially when the raw gas contains water. It has now also been found that certain non-lead containing hydrophobic porous adsorbents are surprisingly capable of effectively removing metal carbonyls from gaseous streams containing water and/or hydrogen sulphide. For the purpose of this application the term "hydrophobic porous adsorbents" refers to hydrophobic adsorbents which contain micro pores having sizes in the range of 0.55 and 4 nm and which only weakly adsorb water. Suitable hydrophobic adsorbents adsorb less than 25 kg H2O/IOO kg of dry adsorbent (25 °C, water vapour pressure 0.1 kPa), more suitably less than 10 kg H2O/IOO kg dry adsorbent. Particular good results are obtained when between 0.001 and 5 kg H2O/IOO kg dry adsorbent is adsorbed, especially between 0.01 and 3 kg H2O/IOO kg dry adsorbent. Preferably between 0.1 and 2 kg H2O/IOO kg dry adsorbent is adsorbed. The invention, therefore, provides a process for the removal of metal carbonyl from a gaseous stream containing water and/or hydrogen sulphide using a hydrophobic microporous adsorbent with an accessible pore volume for pore sizes between 0.55 ana 4 nm of at least 0.005 ml/g. It has now further been found that the process is particularly suitable for removing metal carbonyls from gaseous streams containing carbon monoxide. Preferably the microporous material is an oxide and more in particular a Si and/or Al containing zeolite. In an alternative formulation the process of the present invention concerns a process for the removal of metal carbonyl from a gaseous stream containing water and/or hydrogen sulphide using a microporouz adsorbent with an accessible pore volume for pore sizer oetween 0.55 and 4 nm of at least 0.005 ml/g, the micrcporous material being an oxide and more in particular Si and/or Al containing zeolite. The silica/alumina ratio of the zeolite is preferably at least 25 and the accessible pore volume for pore sizes between 0.55 and 2 nm is at least 0.C2 ml/g. In case of the use of a hydrophobic microporous oxide, its structure is preferably selected from the group consisting of CLO, VFI, AET, API, AFR, AFS, AFY, ATS BEA, BOG, BHP, CAN, EMT, FAU, GME, LTL, MAZ, MOR, MTW, OFF, and ROG. The structures indicated by these capital codes are well known to the r.an skilled in the art and are for example defined and described in Colloid Polym. Science 270: pp. 711-715 (1992; and W.M. Meier and D.H. Olson Atlas of Zeolite Structure Types, 3rd Ed. 1992 Rutterworth-Heinemann, London (1992) ISBN 0-7506-9331-2. The zeolite which is preferably used as an adsorbent is zeolite Y. The present process Lc particularly suitable for the removal of iron caroonyl and/or nickel carbonyl and/or cobalt carbonyl from laseous streams and more in particular from synthesis gas. The present process is preferably used for the removal of metal carbonyls from synthesis gas which is obtained from the partial oxidation of coal and/or liquid hydrocarbons and/or emulsion of hydrocarbons. For large scale applications of the adsorbents according to the present invention it is much more practical to apply extrudates in stead of powders. Therefore, the zeolite is suitably used in the form of an extrudate comprising small zeolite particles and a binder. The zeolite particles are suitably between 0.01 and 100 micron, preferably between 0.1 and 50 micron, more preferably between 0.5 and 20 micron, especially between 1 and 10 micron. The binder may be a binder well known in the art, e.g. a binder which is known from fluid catalytic cracking (FCC). Suitably alumina, silica or silica/alumina may be used. The amount zt binder is suitably between 5 and 80 wt% of the total composition, especially between 10 and 50 wt%. 15-23 wt% gamma-alumina is a preferred binder in view of its good extrusion properties. Usually the binder will have an amorphous structure. To prevent any diffusion proclems, the binder will have relatively large pores when compared with the zeolites, especially macropores and/or mesopores, i.e. pores larger than 2 nanometers. Suitably the binder will have pores between 3 and 500 nanometers, especially between 5 and 100 nanometers. The preparation of the above mentioned extrudates is well known in the art, especially prior art relating to FCC. The nominal diameter of the extrudates is suitably between 0.5 and 10 mm, preferably between 1 and 5 mm, more preferably between 1.5 and 4 mm. The length is suitably 1 to 40 mm, preferably 2 to 30 mm, especially 3 to 15 mm. The weight ratio between zeolite and binder is suitably oetween 20 and 0.1, preferably between 10 and 1. The extrudates may have any suitable shape, e.g. round, triiobes and rings. Another possibility (to be considered as. an equivalent of the extrudates as discussed above) to avoid the use of powders is the use of pellets, balls, pills or rings made from zeolite particles and binder as described above. Conventional techniques well known in the art can be used to produce these pellets etc. The difference between these alternatives and the extrudates described above concerns the way of preparation. The present invention concerns a process for the removal of metal carbonyl from a gaseous stream containing water and/or hydrogen sulphide using a microporous adsorbent with an accessible pore volume for pore sizes between 0.55 and 4 nm of at least 0.005 ml/g, the microporous material being an oxide and more in particular a Si and/or Al containing zeolite. The silica/alumina ratio is preferably at least 25. Particular good results are obtained with a SAR of at least 50, especially at least 75. A suitable upper limit is 1000, especially 600. The process is further preferably used prior to passing the synthesis gas to a process unit for the removal of hydrogen sulphide and/or CO2 from the synthesis gas. In particular the process is used prior to passing the synthesis gas to a Rectisol unit and/or Sulfinol unit, in which hydrogen sulphide and/or CO2 are removed from the synthesis gas. Accordingly the present invention also relates to these respective uses of the present metal carbonyl removal process. As described herein the present invention is particularly suitable for the removal of metal carbonyl from carbon monoxide and/or synthesis gas and is therefore also related to respectively the carbon monoxide and the synthesis gas so obtained. Still further the synthesis gas from which metal carbonyl is removed is particularly suitable for use as feedstock for a hydrogen plant or a petrochemical plant, such as a methanol plant or a plant for the production of hydrocarbons. Therefore the present invention also relates to these respective uses. The carbon monoxide from which metal carbonyl is removed using the present process, is particularly suitable for use as a feedstock for a petrochemical plant, preferably a plant for the production of a CO based polymer. Accordingly, the present invention also relates to these respective uses. Accordingly, the present invention provides a process for the removal of metal carbonyl from a gaseous stream containing water and hydrogen sulphide by contacting the gaseous stream with a porous crystalline adsorbent, characterized in that the porous crystalline adsorbent is a hydrophobic crystalline porous adsorbent with an accessible pore volume for pore sizes between 0.55 and 4 nm of at least 0.005 ml/g and wherein the porous hydrophobic adsorbent adsorbs less than 25 kg H2O/100 kg of dry adsorbent. The present invention will now be furtr.er described in more detail with reference to the relieving examples. Example 1 - The adsorption of iron pentacarbonyi and nickel tetracarbonyl was studied using the gas phase as described in Table 1. In a typical experiment 1 ml of the icsorber.t (particle size; sieve fraction 0.425-0.800 mmj to be zested was loaded in a glass tubular reactor (diameter 10 mm, length 150 mm) and the gas phase without the metal carbonyls present was admitted to the reactor. Once the adsorbents were saturated with water and hydrogen sulphide - as monitored by on line measurement using mass spectrometry; influent concentration is effluent concentration)- the metal carbonyls were introduced to the gas phase and their concentration was monitored upstream and downstream of the reactor using on line UV-VIS spectrometry. The gas hourly space velocity (GHSV NL/L,h} was set at 6000 h"1. The equilibrium capacity of the adsorbents for iron pentacarbonyl and nickel tetracarbonyl is reached when the reactor outlet concentration is equal to the reactor inlet concentration. The results for a number of hydrophobic adsorbents with a suitable pore structure are given in Table 2. n.m. = not measured *SAR = silica alumina ratio means 3 dimensional pores [ ] means 2 dimensional pores This example clearly demonstrates that hydrophobic adsorbents with the claimed pore size show a high capacity for both Fe(C0)5 and Ni(CO)4 in the presence of both water and hydrogen sulphide. Example 2 In this experiment the influence of the concentration of both hydrogen sulphide and water in the gas phase on the capacity of Faujasite for the adsorption of Fe(C0)5 and Ni(C0)4 was studied. First a gas phase was used as in example 1 but without the presence of hydrogen sulphide and water. Water and both water and hydrogen sulphide were added in further tests. The results for Faujasite (see entry 2, Table 2) are collected in Table 3. This example clearly demonstrates that for a hydrophobic adsorbent (as indicated by the high SAR) the capacity of the adsorbent for Fe(C0)5 is not affected by the presence in the gas phase of both water and hydrogen . sulphide. This example also illustrates clearly that when use is made of an hydrophilic adsorbent (SAR = 5) with the same pore structure the capacity of the adsorbent is strongly affected by the presence of water arta hydrogen sulphide in the gas phase. From Zeolites, vol. 12, pp 155-159, 1992, Simonot-Grange, H.H. cs., it is known that the adsorption of zeolites at a SAR of about 30 becomes very small. Example 3 Using the method and the equipment of sample 1 the influence of the required (average) pore size of the adsorbent was studied. Results of the experiments are collected in Table 4. Table 4 Capacity of various adsorbents for Fe(CO)5 This example demonstrates that if the pore size is too small (Mordenite and ZMS-5) the capacity for both Fe(CO)5 and Ni(CO)4 is negligible. An adsorbent with large pores (but within the range claimed) still shows some capacity for Fe(CO)5- This clearly shows that if the pores are too small no capacity for the adsorption of both ?e(CO)5 and Ni(CO)4 was observed. Example 4 Using the method and the equipment as described in example 1 we studied the adsorption capacity of the amorphous porous materials AI2O3 and SiC>2 b°th exibiting a high surface area (300-400 m2/g). To increase their hydrophobic nature the active hydroxyl groups were silylated by reaction with hexamethyldisiloxane (HMDSo). Both treated and untreated materials were tested and the results are collected in Table 5. In this example it is clearly illustrated that a porous adsorbent with a wide -non defined- pore size distribution shows only a very limited capacity for Fe (CO)5, indicating the importance of the pore size as claimed in claim 1. Furthermore it shows that only increasing the hydrophobic nature of the adsorbent does not give the desired capacity for carbonyl adsorption. A combination of pore size and hydrophobicity is essential. Example 5 In a separate experiment it was investigated if the external surface of the crystalline adsorbents claimed could be responsible for the observed adsorption capacity for metal carbonyls. For that purpose we tested Zeolite for Fe(CO)5 adsorption was only 0.6 %m, whereas after removal of the template -by calcination in air at 450 °C-the capacity increased to 9.8 %m, indicating the importance of the pore size (HP 2D 0.76 x 0.64 nm; 5.5 x 5.5 nm) and volume. Example 6 In this example the influence of binder materials as to the adsorption properties of faujasite was investigated. For this purpose -using the method and equipment as described in example 1 (except c(H2S)= 0 %v, c(H20)= 3 %v)- we studied the influence of alumina and silica as a binder material on the adsorption capacity of faujasite with a SAR of 91. Extrudated samples containing either 20 %w silica or 20 %w alumina were used. The results of these experiments are collected in Table 6. WE CLAIM: 1. A process for the removal of metal carbonyl from a gaseous stream containing water and hydrogen sulphide by contacting the gaseous stream with a porous crystalline adsorbent, characterized in that the porous crystalline adsorbent is a hydrophobic crystalline porous adsorbent with an accessible pore volume for pore sizes between 0.55 and 4 nm of at least 0.005 ml/g and wherein the porous hydrophobic adsorbent adsorbs less than 25 kg H2O/100 kg of dry adsorbent. 2. The process as claimed in claim 1, in which the gaseous stream contains carbon monoxide. 3. The process as claimed in claim 1, in which the gaseous stream is obtained in a gasification reactor. 4. The process as claimed in any one of the claims 1 to 3, in which the hydrophobic porous adsorbent is an oxide, preferably a Si and/or Al containing zeolite. 5. The process as claimed in claim 4, in which the silica/alumina ratio of the zeolite is at least 25 and the accessible pore volume for pore sizes between 0.55 and 2 nm is at least 0.02 ml/g. 6. The process as claimed in claim 4, in which the structure of the oxide is selected from the group consisting of CLO, VFI, AET, AFI, AFR, AFS, AFY, ATO, ATS, BEA, BOG, BHP, CAN, EMT, FAU, GME, LTL, MAZ, MEI, MOR, MTW, OFF and ROG, preferably zeolite Y. 7. The process as claimed in any one of the claims 1 to 6, in which the metal carbonyl is iron carbonyl and/or nickel carbonyl and/or cobalt carbonyl. 8. The process as claimed in any one of the claims 1 to 7, in which the porous adsorbent is present in the form of an extrudate of the adsorbent and a binder. 9. The process as claimed in any one of claims 1 to 8, wherein the porous hydrophobic adsorbent adsorbs between 0.001 and 5 kg H2O/100 kg of dry adsorbent. 10. A process for the removal of metal carbonyl from a gaseous stream containing water and hydrogen sulphide substantially as herein described and exemplified.

Full Text

The present invention relates to a process for the removal ox metal carbonyl from a gaseous stream such as synthesis gas using an adsorbent.
The presence of metal carbonyls in synthesis gas which is used as feedstock for industrial processes catalysed by catalysts, poses severe problems. The catalysts can be poisoned by metal carbonyls or their decomposition products and as a consequence perform less. During the production of synthesis gas from the partial oxidation of hydrocarbon containing material such as natural gas, oil and coal in a gasification plant, not only carbon monoxide and hydrogen are formed but also amounts of hydrogen sulphide and, albeit in smaller quantities carbonyl compounds of nickel and iron. Under conditions prevailing in gasification plants carbon monoxide can react with iron and nickel surfaces and with iron and nickel present in the feed of the process to give the corresponding metal carbonyls. Iron carbonyl is often formed by the reaction of carbon monoxide with steel materials in the process equipment. Also metal carbonyls can be formed when gases are transported or stored in metal containers. Nickel tetracarbonyl and iron pentacarbonyl, especially in combination with hydrogen sulphide, can cause serious problems during treatment of raw synthesis gas, mainly due to thermal and/or chemical carbonyl decomposition. The term nraw synthesis gas' refers to the effluent gas from the gasification reactor consisting mainly of CO and H2 (up to 95 %v) , the
remainder being water, CO2/ N2> hydrogen sulphide and

traces of COS, CH4 and NH3. Synthesis gas produced using steam-methane reforming or autotherma* reforming instead of using oil or coal gasification, may also be treated similarly as the raw synthesis gas produced by gasification is treated.
Pressure build-ups downstream frcm the gasification reactor may occur, as metal (sulphide' is being deposited on catalysts used in synthesis gas treating processes, such as COS hydrolysis and the water shift reaction. The term "water shift reaction" refers to the conversion of CO and H2O to H2 and CO2, i.e. the catalytic reaction
between carbon monoxide and water in wnich each molecule
of carbon monoxide is replaced by a molecule of hydrogen
according the following equation CO + H2O > H2 + CO2-
This reaction is also referred to as "the CO Shift Conversion" . Also in Claus plants metal carbonyls can cause problems. For example, if cryogenic methanol is used as a liquid adsorbent for the removal of acid gases, such as hydrogen sulphide and carbon dioxide (as in the Rectisol process) in combination with the Claus plant, deposition of metal oxides and/or metal sulphides can be expected throughout the Claus plant. Part of the carbonyls that cannot be converted by the treating process (e.g. the Rectisol process or other treating processes such as the Selexol process, the Purisol process or the Sulfinol process) will enter the Claus process and gives iron sulphide and nickel sulphide formation in the first catalyst bed. Furthermore in the treating processes as mentioned before sulphides m*y be formed giving fouling problems.
The "Claus process" is a process for the manufacture of sulphur from hydrogen sulphide comprising oxidation of part of the hydrogen sulphide to S02 in a thermal reaction stage, followed by the catalytic reaction of the

remaining hydrogen sulphide with the SO2 formed to give
elemental sulphur in accordance with the following
equation 2H2S + SO2 > 3S + 2H2O.
The "Rectisol process" is a process for desulphurisation and removal of CO2. It. is a physical
washing system which uses cold (cryogenic) methanol (about -30 °C) as its solvent. Both hyarogen sulphide and COS are washed out of the incoming raw synthesis gas with the cold methanol.
The "Sulfinol process" is a process for the removal of, amongst others, hydrogen sulphide and/or CO2/ which
process is well known to the man skilled in the art and is for example defined and described in Oil & Gas Journal, 89 (33) (1991), pp. 57-59.
The "Purisol process" is a process for the removal of H2S and to a lesser extent CO2 from natural gas and
syngas. A description of the process can be found in Kohl and Riesenfeld "Gas Purification", 4th Ed., Gulf Publ. Comp., Houston, London, Paris, Tokyo 1985 ISBN 0-87201-314-6, p. 851.
Furthermore nickel tetracarbonyl and iron pentacarbonyl are toxic already in low concentrations (MAC value 0.05 ppmv). For these reasons it is important that metal carbonyls can be effectively removed from gaseous streams. Given the fact that during normal operation of a gasification plant several tons of iron carbonyl and nickel carbonyl per year are produced, the metal carbonyl problem is a sizeable one.
US 5451384 describes a process for reducing the content of metal carbonyls in gas streams by contacting the gas stream with lead oxide, PbO, dispersed upon a support. The catalyst poisoning problem of metal carbonyls is extensively discussed therein. As suitable supports for the lead oxide zeolites (crystalline silica

aluminas) and aluminas are mentioned. For the removal of Fe(C0)5 from a CO gas PbO/gamma-alumir.a is used in an
example. The pore volume of this adscrrent is 0.42 cm^/g. In an other example Fe(C0)5 is removeci from synthesis
gas. In this example the same PbO/gamma-alumina is used as adsorbent as the one specified above. In US 5451384 it is stated that sulphur will preferably already have been removed from the gas to be treated p:;:r to contact with the metal carbonyl trap. As reason is uven the fact that it is known that sulphur compounds sucr. as H2S will
poison the catalyst used in processes lownstream of the metal carbonyl trap. Further it is mentioned that certain sulphur compounds will compete with tr.o removal of metal carbonyls from the gas stream.
In Sep. Sci. and Techn. 26 (12), pp. 1559-1574, 1991 (by Bhatt, B.L., et al.) and Ind. Enc. Chem. Res.f 30 pp. 502-50, 1991 (by Golden T.C. at al) , a process is described for the removal of metal carbonyl from gas, such as synthesis gas, in which the gas is contacted with zeolite. The process described therein is carried out in the absence of hydrogen sulphide.
A method for the removal of iron pentacarbonyl and/or nickel carbonyl from hydrogen sulphide containing gas streams has been described in EP 023911 A2. According to this patent application a gas stream containing hydrogen sulphide up to 5 vol.% is led over a fixed adsorption bed consisting of zinc sulphide and zinc cxide. The adsorption bed reduces the iron carbonyl content of the gas stream by 99%, whereas the nickel -arbonyl content of the gas stream is lowered by 77% only. This may indicate a relatively low adsorption capacity for nickel carbonyl and/or a contact time limitation and as a consequence forms a constraint on the use of this adsorbent.

As can be deduced from the prior art, it is very difficult to remove iron pentacarbonyl and nickel tetracarbonyl from gas streams which contain both water and hydrogen sulphide. Further it has seen found (ref.: Example 2 hereafter) that porous inorganic substances have relatively low adsorption capacity for metal carbonyl, especially when the raw gas contains water.
It has now also been found that certain non-lead containing hydrophobic porous adsorbents are surprisingly capable of effectively removing metal carbonyls from gaseous streams containing water and/or hydrogen sulphide. For the purpose of this application the term "hydrophobic porous adsorbents" refers to hydrophobic adsorbents which contain micro pores having sizes in the range of 0.55 and 4 nm and which only weakly adsorb water. Suitable hydrophobic adsorbents adsorb less than 25 kg H2O/IOO kg of dry adsorbent (25 °C, water vapour
pressure 0.1 kPa), more suitably less than 10 kg H2O/IOO kg dry adsorbent. Particular good results are
obtained when between 0.001 and 5 kg H2O/IOO kg dry
adsorbent is adsorbed, especially between 0.01 and 3 kg H2O/IOO kg dry adsorbent. Preferably between 0.1 and 2 kg
H2O/IOO kg dry adsorbent is adsorbed.
The invention, therefore, provides a process for the removal of metal carbonyl from a gaseous stream containing water and/or hydrogen sulphide using a hydrophobic microporous adsorbent with an accessible pore volume for pore sizes between 0.55 ana 4 nm of at least 0.005 ml/g.
It has now further been found that the process is particularly suitable for removing metal carbonyls from gaseous streams containing carbon monoxide. Preferably the microporous material is an oxide and more in

particular a Si and/or Al containing zeolite. In an alternative formulation the process of the present invention concerns a process for the removal of metal carbonyl from a gaseous stream containing water and/or hydrogen sulphide using a microporouz adsorbent with an accessible pore volume for pore sizer oetween 0.55 and 4 nm of at least 0.005 ml/g, the micrcporous material being an oxide and more in particular * Si and/or Al containing zeolite.
The silica/alumina ratio of the zeolite is preferably at least 25 and the accessible pore volume for pore sizes between 0.55 and 2 nm is at least 0.C2 ml/g.
In case of the use of a hydrophobic microporous oxide, its structure is preferably selected from the group consisting of CLO, VFI, AET, API, AFR, AFS, AFY, ATS BEA, BOG, BHP, CAN, EMT, FAU, GME, LTL, MAZ, MOR, MTW, OFF, and ROG. The structures indicated by these capital codes are well known to the r.an skilled in the art and are for example defined and described in Colloid Polym. Science 270: pp. 711-715 (1992; and W.M. Meier and D.H. Olson Atlas of Zeolite Structure Types, 3rd Ed. 1992 Rutterworth-Heinemann, London (1992) ISBN 0-7506-9331-2. The zeolite which is preferably used as an adsorbent is zeolite Y. The present process Lc particularly suitable for the removal of iron caroonyl and/or nickel carbonyl and/or cobalt carbonyl from laseous streams and more in particular from synthesis gas. The present process is preferably used for the removal of metal carbonyls from synthesis gas which is obtained from the partial oxidation of coal and/or liquid hydrocarbons and/or emulsion of hydrocarbons.
For large scale applications of the adsorbents according to the present invention it is much more practical to apply extrudates in stead of powders. Therefore, the zeolite is suitably used in the form of an

extrudate comprising small zeolite particles and a binder. The zeolite particles are suitably between 0.01 and 100 micron, preferably between 0.1 and 50 micron, more preferably between 0.5 and 20 micron, especially between 1 and 10 micron. The binder may be a binder well known in the art, e.g. a binder which is known from fluid catalytic cracking (FCC). Suitably alumina, silica or silica/alumina may be used. The amount zt binder is suitably between 5 and 80 wt% of the total composition, especially between 10 and 50 wt%. 15-23 wt% gamma-alumina is a preferred binder in view of its good extrusion properties. Usually the binder will have an amorphous structure. To prevent any diffusion proclems, the binder will have relatively large pores when compared with the zeolites, especially macropores and/or mesopores, i.e. pores larger than 2 nanometers. Suitably the binder will have pores between 3 and 500 nanometers, especially between 5 and 100 nanometers. The preparation of the above mentioned extrudates is well known in the art, especially prior art relating to FCC. The nominal diameter of the extrudates is suitably between 0.5 and 10 mm, preferably between 1 and 5 mm, more preferably between 1.5 and 4 mm. The length is suitably 1 to 40 mm, preferably 2 to 30 mm, especially 3 to 15 mm. The weight ratio between zeolite and binder is suitably oetween 20 and 0.1, preferably between 10 and 1. The extrudates may have any suitable shape, e.g. round, triiobes and rings. Another possibility (to be considered as. an equivalent of the extrudates as discussed above) to avoid the use of powders is the use of pellets, balls, pills or rings made from zeolite particles and binder as described above. Conventional techniques well known in the art can be used to produce these pellets etc. The difference between these alternatives and the extrudates described above concerns the way of preparation.

The present invention concerns a process for the removal of metal carbonyl from a gaseous stream containing water and/or hydrogen sulphide using a microporous adsorbent with an accessible pore volume for pore sizes between 0.55 and 4 nm of at least 0.005 ml/g, the microporous material being an oxide and more in particular a Si and/or Al containing zeolite. The silica/alumina ratio is preferably at least 25. Particular good results are obtained with a SAR of at least 50, especially at least 75. A suitable upper limit is 1000, especially 600.
The process is further preferably used prior to passing the synthesis gas to a process unit for the removal of hydrogen sulphide and/or CO2 from the
synthesis gas. In particular the process is used prior to passing the synthesis gas to a Rectisol unit and/or Sulfinol unit, in which hydrogen sulphide and/or CO2 are
removed from the synthesis gas. Accordingly the present invention also relates to these respective uses of the present metal carbonyl removal process.
As described herein the present invention is particularly suitable for the removal of metal carbonyl from carbon monoxide and/or synthesis gas and is therefore also related to respectively the carbon monoxide and the synthesis gas so obtained.
Still further the synthesis gas from which metal carbonyl is removed is particularly suitable for use as feedstock for a hydrogen plant or a petrochemical plant, such as a methanol plant or a plant for the production of hydrocarbons. Therefore the present invention also relates to these respective uses.
The carbon monoxide from which metal carbonyl is removed using the present process, is particularly suitable for use as a feedstock for a petrochemical

plant, preferably a plant for the production of a CO based polymer. Accordingly, the present invention also relates to these respective uses.
Accordingly, the present invention provides a process for the removal of metal carbonyl from a gaseous stream containing water and hydrogen sulphide by contacting the gaseous stream with a porous crystalline adsorbent, characterized in that the porous crystalline adsorbent is a hydrophobic crystalline porous adsorbent with an accessible pore volume for pore sizes between 0.55 and 4 nm of at least 0.005 ml/g and wherein the porous hydrophobic adsorbent adsorbs less than 25 kg H2O/100 kg of dry adsorbent.

The present invention will now be furtr.er described in more detail with reference to the relieving examples.
Example 1
-
The adsorption of iron pentacarbonyi and nickel tetracarbonyl was studied using the gas phase as described in Table 1.

In a typical experiment 1 ml of the icsorber.t (particle size; sieve fraction 0.425-0.800 mmj to be zested was loaded in a glass tubular reactor (diameter 10 mm, length 150 mm) and the gas phase without the metal carbonyls present was admitted to the reactor. Once the adsorbents were saturated with water and hydrogen sulphide - as monitored by on line measurement using mass spectrometry;

influent concentration is effluent concentration)- the metal carbonyls were introduced to the gas phase and their concentration was monitored upstream and downstream of the reactor using on line UV-VIS spectrometry. The gas
hourly space velocity (GHSV NL/L,h} was set at 6000 h"1. The equilibrium capacity of the adsorbents for iron pentacarbonyl and nickel tetracarbonyl is reached when the reactor outlet concentration is equal to the reactor inlet concentration. The results for a number of hydrophobic adsorbents with a suitable pore structure are given in Table 2.

n.m. = not measured *SAR = silica alumina ratio means 3 dimensional pores [ ] means 2 dimensional pores
This example clearly demonstrates that hydrophobic adsorbents with the claimed pore size show a high capacity for both Fe(C0)5 and Ni(CO)4 in the presence of
both water and hydrogen sulphide.

Example 2
In this experiment the influence of the concentration of both hydrogen sulphide and water in the gas phase on the capacity of Faujasite for the adsorption of Fe(C0)5
and Ni(C0)4 was studied. First a gas phase was used as in
example 1 but without the presence of hydrogen sulphide and water. Water and both water and hydrogen sulphide were added in further tests. The results for Faujasite (see entry 2, Table 2) are collected in Table 3.

This example clearly demonstrates that for a hydrophobic adsorbent (as indicated by the high SAR) the capacity of the adsorbent for Fe(C0)5 is not affected by
the presence in the gas phase of both water and hydrogen . sulphide. This example also illustrates clearly that when use is made of an hydrophilic adsorbent (SAR = 5) with the same pore structure the capacity of the adsorbent is

strongly affected by the presence of water arta hydrogen sulphide in the gas phase.
From Zeolites, vol. 12, pp 155-159, 1992, Simonot-Grange, H.H. cs., it is known that the adsorption of zeolites at a SAR of about 30 becomes very small. Example 3
Using the method and the equipment of sample 1 the influence of the required (average) pore size of the adsorbent was studied. Results of the experiments are collected in Table 4.
Table 4 Capacity of various adsorbents for Fe(CO)5

This example demonstrates that if the pore size is too small (Mordenite and ZMS-5) the capacity for both Fe(CO)5
and Ni(CO)4 is negligible. An adsorbent with large pores
(but within the range claimed) still shows some capacity for Fe(CO)5- This clearly shows that if the pores are too
small no capacity for the adsorption of both ?e(CO)5 and
Ni(CO)4 was observed.
Example 4
Using the method and the equipment as described in example 1 we studied the adsorption capacity of the

amorphous porous materials AI2O3 and SiC>2 b°th exibiting
a high surface area (300-400 m2/g). To increase their hydrophobic nature the active hydroxyl groups were silylated by reaction with hexamethyldisiloxane (HMDSo). Both treated and untreated materials were tested and the results are collected in Table 5.

In this example it is clearly illustrated that a porous adsorbent with a wide -non defined- pore size distribution shows only a very limited capacity for Fe (CO)5, indicating the importance of the pore size as
claimed in claim 1. Furthermore it shows that only increasing the hydrophobic nature of the adsorbent does not give the desired capacity for carbonyl adsorption. A combination of pore size and hydrophobicity is essential. Example 5
In a separate experiment it was investigated if the external surface of the crystalline adsorbents claimed could be responsible for the observed adsorption capacity for metal carbonyls. For that purpose we tested Zeolite

for Fe(CO)5 adsorption was only 0.6 %m, whereas after removal of the template -by calcination in air at 450 °C-the capacity increased to 9.8 %m, indicating the importance of the pore size (HP 2D 0.76 x 0.64 nm; 5.5 x 5.5 nm) and volume. Example 6
In this example the influence of binder materials as to the adsorption properties of faujasite was investigated. For this purpose -using the method and equipment as described in example 1 (except c(H2S)= 0 %v,
c(H20)= 3 %v)- we studied the influence of alumina and
silica as a binder material on the adsorption capacity of faujasite with a SAR of 91. Extrudated samples containing either 20 %w silica or 20 %w alumina were used. The results of these experiments are collected in Table 6.

WE CLAIM:
1. A process for the removal of metal carbonyl from a gaseous stream containing water and hydrogen sulphide by contacting the gaseous stream with a porous crystalline adsorbent, characterized in that the porous crystalline adsorbent is a hydrophobic crystalline porous adsorbent with an accessible pore volume for pore sizes between 0.55 and 4 nm of at least 0.005 ml/g and wherein the porous hydrophobic adsorbent adsorbs less than 25 kg H2O/100 kg of dry adsorbent.
2. The process as claimed in claim 1, in which the gaseous stream contains carbon monoxide.
3. The process as claimed in claim 1, in which the gaseous stream is obtained in a gasification reactor.
4. The process as claimed in any one of the claims 1 to 3, in which the hydrophobic porous adsorbent is an oxide, preferably a Si and/or Al containing zeolite.
5. The process as claimed in claim 4, in which the silica/alumina ratio of the zeolite is at least 25 and the accessible pore volume for pore sizes between 0.55 and 2 nm is at least 0.02 ml/g.
6. The process as claimed in claim 4, in which the structure of the oxide is selected from the group consisting of CLO, VFI, AET, AFI, AFR, AFS, AFY, ATO, ATS, BEA, BOG, BHP, CAN, EMT, FAU, GME, LTL, MAZ, MEI, MOR, MTW, OFF and ROG, preferably zeolite Y.

7. The process as claimed in any one of the claims 1 to 6, in which the metal carbonyl is iron carbonyl and/or nickel carbonyl and/or cobalt carbonyl.
8. The process as claimed in any one of the claims 1 to 7, in which the porous adsorbent is present in the form of an extrudate of the adsorbent and a binder.
9. The process as claimed in any one of claims 1 to 8, wherein the porous
hydrophobic adsorbent adsorbs between 0.001 and 5 kg H2O/100 kg of dry
adsorbent.
10. A process for the removal of metal carbonyl from a gaseous stream containing
water and hydrogen sulphide substantially as herein described and exemplified.

Documents:

in-pct-2001-017-che-abstract.pdf

in-pct-2001-017-che-claims.pdf

in-pct-2001-017-che-correspondance others.pdf

in-pct-2001-017-che-correspondance po.pdf

in-pct-2001-017-che-description complete.pdf

in-pct-2001-017-che-form 1.pdf

in-pct-2001-017-che-form 19.pdf

in-pct-2001-017-che-form 26.pdf

in-pct-2001-017-che-form 3.pdf

in-pct-2001-017-che-form 5.pdf

in-pct-2001-017-che-pct.pdf

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Patent Number

222295

Indian Patent Application Number

IN/PCT/2001/17/CHE

PG Journal Number

47/2008

Publication Date

21-Nov-2008

Grant Date

05-Aug-2008

Date of Filing

04-Jan-2001

Name of Patentee

SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.

Applicant Address

CAREL VAN BYLANDTLAAN 30, NL-2596 HR, THE HAGUE,

Inventors:

#	Inventor's Name	Inventor's Address
1	ROGER EIJKHOUDT	VLETWEIDE 186, NL-3981 ZR, BUNNIK,
2	JOHN, WILHELM GEUS	GEZICHTSLAAN 100, NL-3723 GJ BILTHOVEN,
3	CORNELIS, JACOBUS SMIT	BADHUISWEG 3, NL-1031 CM, AMSTERDAM,

PCT International Classification Number

B01D53/46

PCT International Application Number

PCT/EP1999/04916

PCT International Filing date

1999-07-05

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	98305411.5	1998-07-08	EUROPEAN UNION