Fatty methyl ester hydrogenation to fatty alcohol part II: Process issues

Fatty alcohols are produced by hydrogenating fatty methyl esters in slurry phase in the presence of copper chromite catalyst at temperatures of 250–300°C and hydrogen pressures of 2000–3000 psi. The fatty methyl ester, catalyst, and hydrogen are fed to the reactor cocurrently. The product slurry is passed through gas-liquid separators and then through a continuous filtration system for removal of the catalyst. A portion of the used catalyst in crude alcohol is recycled to the hydrogenator. The overall efficiency of the process depends upon the intrinsic activity, life, and filterability of the catalyst. The fatty alcohol producer therefore requires a catalyst with high activity, long life, and good separation properties. The main goal of the present laboratory investigation was to develop a superior copper chromite catalyst for the slurry-phase process. Two copper chromite catalysts, prepared by different procedures, were tested for methyl ester hydrogenolysis activity, reusability, and filtration characteristics. The reaction was carried out in a batch autoclave at 280°C and 2000–3000 psi hydrogen pressure. The reaction rates were calculated by assuming a kinetic mechanism that was first-order in methyl ester concentration. The catalyst with the narrower particle size distribution was 30% more active, filtered faster, and maintained activity for several more uses than the catalyst with the broader particle size distribution. X-ray photoelectron spectroscopy data showed higher surface copper concentrations for the former catalyst.