Selectivity in the high-temperature hydrogenation of acetone with silica-supported nickel and cobalt catalysts

In this work, both the physicochemical properties and the selectivity in the acetone hydrogenation for a series of silica-supported nickel and cobalt catalyst were studied, The influence of several preparative aspects, such as the source of the silica support, its sodium content, the calcination temperature and the H-2 reduction temperature of the precursors on the metallic dispersions were investigated. The hydrogenation of acetone was carried out at experimental conditions similar to those necessary for a chemical heat pump application (200 degrees C and high overall acetone conversions), Very high selectivities to 2-propanol are required at these severe and unusual conditions, An excellent performance was found for one of the nickel on silica catalysts which gives selectivities to 2-propanol higher than 99% at 200 degrees C for acetone overall conversions up to 35%, It has been found that the selectivity to this product can be improved by neutralizing the acidic functions of the catalyst, When the sodium content of a poorly alkaline silica is increased, its selectivity to 2-propanol increases due to the suppression of the diisopropyl ether formation, However, an adequate balance between sites is needed since an excessive amount of sodium increases the selectivity to methane, Higher selectivities to 2-propanol were found with Ni compared to Co catalysts due to the formation of methane in significant amounts with Co. The selectivity to 2-propanol decreases as both hydrogenation temperature and acetone feed contents increase, increasing in this way the selectivity to the hydrocracking products. (C) 1995 Academic Press, Inc.