Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1984-11-30
1986-09-09
Evans, J. E.
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
562607, 568864, C07C 29136
Patent
active
046110852
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the vapour phase hydrogenation of carboxylic acid esters to give alcohols.
It is disclosed in GB Pat. No. 1 471 233 that catalysts prepared from transition metal compounds and a defined carbon support may be used for certain hydrogenation reactions. However there is no suggestion that such catalysts would be useful for the hydrogenation of carboxylic esters to give alcohols. This is a very difficult reaction to carry out with adequate selectivity. Attempts to hydrogenate carboxylic acid esters often give the acid and a hydrocarbon rather than the alcohol. There is nothing in GB Pat. No. 1 471 233 to suggest that the catalysts described therein would be in any way suitable for the hydrogenation of esters to give alcohols.
U.S. Pat. No. 4,346,240 discloses a process for the liquid phase hydrogenation of esters to give alcohols. The catalyst used is prepared from transition metals, activated carbon, and alkali metals. The alkali metal is introduced onto the carbon either as the free metal or as a cationic form with a very strongly basic anion. When an alkali metal compound is used, it is introduced onto the support using solvents which lack free hydroxyl groups. Water could not be used as a solvent for the alkali metal compounds disclosed in U.S. Pat. No. 4,346,240.
U.S. Pat. No. 4,346,240 states that the hydrogenation may be carried out at temperatures in the range 0.degree.-150.degree. C., but a preference is expressed for temperatures of 25.degree.-100.degree. C. It is stated that higher temperatures may be used and are considered to be equivalent to the temperature ranges given.
In a liquid phase process any increase in the reaction temperature will cause an increase in the reaction pressure necessary to keep the reaction in the liquid phase, which will increase the cost of the process. In these specific examples of U.S. Pat. No. 4,346,240 reaction pressures of 770 kPa (90 psig) and 1150 kPa (150 psig) are used. Very long contact times are also used. The shortest time was two hours but in most examples the reaction time was 24 hours.
It would be desirable to be able to prepare alcohols from esters by a continuous vapour phase process rather than by the liquid phase batch process disclosed in U.S. Pat. No. 4,346,240. However in order to obtain a useful production rate it is necessary to use comparatively short contact times. In order to obtain a useful rate of reaction with a short contact time, it is necessary to use a relatively high reaction temperature.
U.S. Pat. No. 4,346,240 discusses several known catalysts used for the hydrogenation of esters. These use temperatures above 150.degree. C., but also use very high pressures (13.8 MPa to 20.7 MPa) so that the process will be a liquid phase process. The catalysts mentioned are Raney nickel, copper chromite or zinc-chromium oxide. However if such catalysts are used in vapour phase processes instead of liquid phase processes the elevated temperature the results deteriorate markedly. Thus until now it has not been possible to carry out the vapour phase hydrogenation of esters to alcohols in a satisfactory manner.
There is nothing in U.S. Pat. No. 4,346,240 to suggest that the nature of the carbon support is in any way important for the hydrogenation of esters or that ester hydrogenation catalysts can be made without the use of promoters in the form of free metals or in the form of special ionic forms unstable to water.
According to the present invention the process for the production of an alcohol by hydrogenation of an ester with a hydrogenation catalyst comprising a Group VIII element, a promoter, and a carbon support is characterized in that (1) the Group VIII element is ruthenium, nickel or rhodium, (2) the promoter is introduced onto the carbon as a water stable compound of a Group IA, IIA metal a lanthanide or actinide, and (3) the carbon has a BET surface area of at least 100 m.sup.2 /g, and a ratio of BET to basal plane surface area not greater than 4:1, and (4) the hydrogenation is carried out in the vapour phase at
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Evans J. E.
The British Petroleum Company p.l.c.
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