Title of Invention

A PROCESS FOR THE PREPARATION OF A MODIFIED NICKEL CATALYST

Abstract

This invention relates to an improved process for the preparation of modified nickel catalyst. The catalyst is useful for the reduction of organic compounds. The modified raney nickel catalysts consisting of combinations of metals and their salts from group VIII(Fe,Co,Ni families) and other transition metals in combination with alkali and alkaline metal salts and in varied solvent media under optimum conditions of temperature,hydrogen pressure, Ph and time.The catalyst is used for the direct reduction/hydrogenation of aldehydes, a,ß-unsaturated aldehydes and allylic alcohols to corresponding saturated alcohols.

Full Text

This invention relates to an improved process for the preparation of modified nickel catalyst. This invention particularly relates to an improved process for the production of modified nickel catalyst for the direct red uction/hydrogenation of aldehydes, a,ß-unsaturated aldehydes and allylic alcohols to corresponding saturated alcohols without affecting other isolated unsaturated centers in the molecule. More particularly this invention relates to the development of selective modified raney nickel catalysts consisting of combinations of metals and their salts from group VIII(Fe,Co,Ni families) and other transition which are suitably used in the media either as such or in combination with alkali and alkaline metal salts and in varied solvent media under optimum conditions of temperature, hydrogen pressure, Ph and time. Nickel and cobalt are important hydrogenation catalyst because of their ability to chemisorb hydrogen. Raney Nickel is one of the most important catalysts of nickel and is used widely in laboratory and industrial hydrogenation processes. It is the most active and the least specific nickel catalyst and also has been used in continuous hydrogenation processes. The activity and specificity of nickel catalyst is also very much dependent upon its method of preparation and other parameters of temperature, time and mode of addition. A variety of nickel catalysts are available which are used for specific purposes. The hydrogenation of unsaturated aldehydes and ketones in the presence of Raney Nickel is a complex process and mixture of 3 products viz, saturated carbonyl, unsaturated alcohols and the saturated alcohols, may well be obtained. In general, mild conditions lead to a predominance of saturated carbonyl whilst more forcing conditions favour the saturated alcohols. Raney Nickel in general, cannot be used directly for the hydrogenation of aldehydic functions in presence of isolated olefinic centers because of its activity to hydrogenate both the centers. It is therefore, required to modify the catalyst in such a way that only the aldehydic function or a, ß-unsaturated aldehydes or allylic alcohols are hydrogenated into saturated alcohols without affecting the isolated olefmic centers. No prior art is available in the literature concerning the present invention. Heterogenous catalytic hydrogenation and chemical reduction of aldehydes and other organic compounds in liquid phase has been attempted by several workers using nickel, cobalt, palladium, platinum and ruthenium metal catalysts [ BASF, DE-OS 2934250,1979, (M. Horn-er, M. Irgang, A. Nissen, Universal oil products [US. 3275 696, 1961 (E. Goldstar), metal hydrides [J.S. Pizey, Synthetic Reagents Vol. 1 (1974) p. 106, John wiley & Sons], and many other reagents [Neri, G. et al, J. Chem. Technol Biotechnol. (1994) 60, 838]. Some of the catalysts mentioned above are even employed on a commercial scale but suffer for want of side reactions and are accompanied with undesirable products above tolerable limits," which are difficult to separate economically. These processes are also time consuming and are quite complicated. The present invention provides a modified Raney Nickel catalyst to convert aldehydes, a, /3-unsaturated aldehydes and allylic alcohols into saturated alcohols in high yields without side reactions. The isolated olefmic linkages present in the organic molecules remain unaffected thus clearly indicating an edge over conventional Raney Nickel catalyst. Therefore, invention of a direct heterogenous hydrogenation catalyst for direct reduction/ hydrogenatiotf of aldehydes, a, /3-unsaturated aldehydes and allylic alcohols to corresponding saturated^ alcofrols without affecting other isolated unsaturated centers in the molecule in a single step without side reactions,is advantageous. Further the corresponding esters present in the oil also get changed into alcohols, thus affording a product of high purity. The main object of the present invention is to provide a novel catalyst useful for the reduction of organic compounds. Another objective is to provide a process for the production of catalyst for the transformation of substituted aldehydes, a, ß-unsaturated aldehydes and allylic alcohols into corresponding saturated alcohols without or with minimum side reactions which obviates the drawbacks of the present methods as detailed above. Another objective of the present invention is to develop a process for an improved modified Raney Nickel catalyst with suitable modifiers to protect other isolated unsaturated centers in the molecule suitable for the direct reduction / hydrogenation of aldehydes, a, ß-unsaturated aldehydes and allylic alcohols. Yet another objective of the invention is to use a novel catalyst in such a way which will hydrogenate the aldehydic function or the a, ß-unsaturated aldehydes only, without affecting the isolated double bond of the molecule so as to give the maximum yield of the product. Yet still another objective is that by employing the catalyst and the conditions mentioned in the invention, the formation of undesired side products is totally hindered or minimized and catalyst recovered for reprocessing. An improved process for the preparation of modified nickel catalyse which comprises; a) preparing fresh raney nickel catalys, by conventional methods as herein described b) treating the said fresh raney nickel catalyst 80 to 99.4 mole % characterised in that with salts of metals of Group I 0.3 to 18.5 mole %, Group II and transition metal 0.3 to 19.5 mole % optionally in presence of organic base such as amino compound and acid at a temperature in the range of 10 to -10 deg.C for a period of 1.5 to 4.0 hr to get modified nickel catalyst. Raney Nickel catalyst may be prepared by reacting nickel-aluminum alloy in presence of alkali hydroxide at a temperature in the range of 10° C to -10 C. In an embodiment of the present invention the metal salts may be of Group I, Group II, Group VIII such as sodium bicarbonate, sodium carbonate, potassium carbonate and other transition metal salts used may be of copper, iron, cobalt and/or barium sulphate and mixture thereof. In another embodiment of the invention the organic base used may be amino compounds such as triethylamine, piperidine, collidine and mixture thereof. We have found that although noble metal and modified Raney Nickel catalyst give hydrogenated products more or less in good amounts but the selectivity and yields were more pronounced when the catalysts were used in the presence of inorganic & organic bases, and salts of Group b Group ILfGroup VIII and other transition metals.Reduction of aldehydes and allylic aldehydes proceeded efficiently by heterogenous catalysis with modified nickel catalyst under blanket of hydrogen to give corresponding saturated alcohols in high yields. Most of the allylic alcohols were also reduced efficiently, but isolated and sterically hindered olefins resisted the reduction. Nickel catalyst suitable for the present operation was prepared from nickel-aluminum alloy in the presence of modifiers like organic and inorganic bases and/or in the presence of salts of Group I, Group II, Group VIII and other transition metals and by leaching of alloy with lye at a temperature of -10° to 100°C. It is, of course convenient to use hydrocarbons and alcohols as a medium and very convenient to use reaction mixture itself. Depending on the system the catalysts can be prepared and utilized directly or can be stored as per requirements. The catalysts so invented are suitable for operations under batch processes at elevated temperature, hydrogen pressure and wide pH range. In some instances the combination was found to be the best when generated in situ. In general the usual relationship of time, temperature, activity of catalyst, ratio of activity to volume of catalyst etc. apply in the present case. We have found that the most suitable catalyst for the present invention comprises a moderately active modified Raney nickel type catalyst at suitable temperature/and pressure applied under the conditions of hydrogenation in the presence of hydrogen above atmospheric pressure. In some cases mineral acids, inorganic and organic bases, salts of Group I, Group II, Group VIII and other transition metals are used as modifiers to retard or check the hydrogenation of other isolated olefinic centers in the molecule. The modified nickel catalyst so developed comprises of 80 to 99.4 mql% of nickel, 0.3 to 18.5 mol% of alkali metal salts like sodium carbonate/ potassium bicarbonate and 0.3 to 19.5 mol% of and alkaline and transition metal salts like copper sulphate/ ferrous sulphate/ cobalt nitrate and/or barium sulphate and organic bases like triethylamine, piperidine or collidine etc. suitable for hydrogenation of aldehydes, a, ß-unsaturated aldehydes and allylic alcohols into saturated alcohols of high purity. In general the usual relationship of catalyst activity, temperature, pressure, medium and time, along with other physical and chemical parameters apply in the present case. It is important to optimize all the above mentioned conditions in order to get the desired product. The above mentioned catalyst was employed to reduce various aldehydes, a, ß-unsaturated aldehydes and allylic alcohols. In every case saturated alcohols were obtained without any side reactions and isolated olefins survived the reaction conditions employed. The chemically/ catalytically treat¬ed reaction product was suitably filtered/ centrifuged and rectified in batch fractionating column. The modified Raney Nickel catalyst so prepared in the presence of suitable modifiers is suitable for the direct reduction/ hydrogenation of aldehydes, a, ß-unsaturated aldehydes and allylic alcohols particularly of citronellal, citral and geraniol and/or mixture of these compounds and of essential oils containing these compounds (ex. Eucalyptus citriodora, Java citronella, lemon grass, Litsea cubeba and other oils) in varied solvent media under optimum conditions of temperature, hydrogen pressure, pH and time to get perfumery grade citronellol of high purity without or with a trace of dihydrocitronellol. The invention is described further with reference to examples given below. These examples should not be construed as to restrict the scope of the invention. Example- 1 Sodium hydroxide (400 g.) and distilled water (1500 ml.) were taken in a glass beaker and contents cooled to -5° C with vigorous stirring. Nickel-Aluminum alloy (300 g.) was added slowly at such a rate that the reaction temperature remained below -5° C. The reaction mixture was further stirred additionally for six hours at 10°C. The catalyst washed with water followed by alcohol and pH adjusted to 7.0-12 by addition of sodium carbonate, and triethyl amine. The selectivity was further modified by addition of barium sulphate (2.5%;4.8 g.). The mixture of catalyst and additives was further stirred for four hours at -10°C and allowed to settle down. The catalyst was used directly for the reductions. Example- 2 Sodium hydroxide (400 g.) and distilled water (1500 ml.) were taken in a glass beaker and contents cooled to -5° C with vigorous stirring. Nickel-Aluminum alloy (300 g.) was added slowly at such a rate that the reaction temperature remained below -5° C. The reaction mixture was further stirred additionally for six hours at 10°C. The catalyst washed with water and modified by addition of sodium bicarbonate and (2.5%;4.8 g) ferric sulphate (0.4%;0.8 g.). The mixture of catalyst and additives was further stirred for four hours at -10° C and allowed to settle down. The catalyst was stored in alcohol and used for the reductions when required. Example-3 100 g. Sodium hydroxide was dissolved in 300 ml. of distilled water in a glass beaker and contents cooled to -8° C with vigorous stirring. Nickel-Aluminum alloy (100 g.) was added slowly while maintaining reaction temperature below 10° C. The reaction mixture further stirred for two hours at 10° C. The catalyst washed with water and to it added 2.5 g. ferrous sulphate and 1.4 g. cobalt nitrate. The mixture of catalyst and additives was stirred for 1.5 hours at -3° C and allowed to settle down. The catalyst was used directly for the reductions. Example-4 100 g. Sodium hydroxide was dissolved in 300 ml. of distilled water in a glass beaker and contents cooled to -8° C with vigorous stirring. Nickel-Aluminum alloy (100 g.) was added slowly while maintaining reaction temperature below 10° C. The reaction mixture further stirred for two hours at 10° C. The catalyst washed with water and to it added 5.3 g. copper sulphate and 0.4 g. sulphuric acid. The mixture of catalyst and additives was stirred for 1.5 hours at -3° C and allowed to settle down. The catalyst was used directly for the reductions. Example -5 In the reactor fitted with all the necessary gadgets were placed lemon grass oil (1.0 kg) having a citral content of 75%. The oil was diluted with the isopropanol (6 times) and the mechanical agitator started. Then modified nickel catalyst (150 g), copper sulphate (15.0 g.) and sulphuric acid (1.0 ml) were fed through the opening and the vessel evacuated. The hydrogen inlet valve was opened and hydrogen gas injected to maintain the required conditions. After the necessary conditions have been maintained and reaction complete, the vessel was degassed and the catalyst filtered out to recover the oil. The solvent was then removed under reduced pressure to yield the reduced oil. GC analysis showed that whole of citral has changed into citronellol. Advantages: 1. The main advantage of the present invention is to provide a selective catalyst for the transformation of substituted aldehydes, a, ß-unsaturated aldehydes and allylic alcohols into corresponding saturated alcohols without side reactions. 2. Provide a catalyst that does not disturb the isolated olefinic linkages in the molecules which results in the product of high purity. We Claim: 1. An improved process for the preparation of modified nickel catalyst which comprises; a) preparing fresh raney nickel catalyst by conventional methods as herein described, b) treating the said fresh raney nickel catalyst 80 to 99.4 mole % characterised in that with salts of metals of Group 1/0.3 to 18.5 mole %, Group II/and transition metal 0.3 to 19.5 mole % optionally in presence of organic base such as amino compound and acid at a temperature in the range of 10 to -10 deg.C for a period of 1.5 to 4.0 hr to get modified nickel catalyst. 2. An improved process as claimed in claim 1 wherein the metal salts of Group I are selected from sodium bicarbonate, sodium carbonate, potassium carbonate, Group II salt is barium sulphate and transition metal salts are selected from copper, iron, cobalt or mixture thereof. 3. An improved process as claimed in claims 1 to 2 wherein amino compounds are selected from triethylamine, piperdine, collidine and mixture thereof. 4. An improved process as claimed in claims 1 to 3 wherein the acid is sulphuric acid. 5. An improved process for the preparation of modified nickel catalyst substantially as herein described with reference to examples.

Documents:

729-del-1999-abstract.pdf

729-del-1999-claims.pdf

729-del-1999-correspondence-others.pdf

729-del-1999-correspondence-po.pdf

729-del-1999-description (complete).pdf

729-del-1999-form-1.pdf

729-del-1999-form-19.pdf

729-del-1999-form-2.pdf