Fatty alcohols, derived from natural sources, are commercially produced by hydrogenation of fatty acids or methyl esters in slurry-phase or fixed-bed reactors. One slurryphase hydrogenation of methyl ester process flows methyl esters and powdered copper chromite catalyst into tubular reactors under high hydrogen pressure and elevated temperature. In the present investigation, slurry-phase hydrogenations of C 12 methyl ester were carried out in semi-batch reactions at nonoptimal conditions (i.e., low hydrogen pressure and elevated temperature). These conditions were used to accentuate the host of side reactions that occur during the hydrogenation. Some 14 side reaction routes are outlined. As an extension of this study, copper chromite catalyst was produced under a number of varying calcination temperatures. Differences in catalytic activity and selectivity were determined by closely following side reaction products. Both activity and selectivity correlate well with the crystallinity of the copper chromite surface; they increase with decreasing crystallinity. The ability to follow the wide variety of side reactions may well provide an additional tool for the optimized design of hydrogenation catalysts. JAOCS 74, 333-339 (1997). FIG. 2. Potential reaction routes in the hydrogenation of alkyl methyl ester.

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. JAOCS 74, 341-345 (1997). KEY WORDS:Copper chromite, fatty alcohol, fatty-fatty ester, filtration, hydrogenolysis, methyl ester, particle size distribution, slurry hydrogenation, wax ester.Commercially, fatty alcohols are produced by methanolysis of triglyceride or fatty acid feed stock, followed by catalytic hydrogenolysis of the methyl ester (1). In the slurry process, the overall alcohol production rate per kilogram of catalyst depends upon the intrinsic activity, deactivation rate, and filtration characteristics of the catalyst. Conversion levels are maintained by continuously adding a small amount of fresh catalyst in the recycle stream, and withdrawing spent catalyst (2). The fresh catalyst in the oxide form is activated in situ (reduction of the cupric ions) under reaction conditions. The in situ reduction creates the active sites required for hydrogenolysis. The fatty alcohol producer therefore requires a catalyst with high activity, long life, and good separation properties. Therefore, research was undertaken to develop a catalyst with higher hydrogenation activity and selectivity.Catalyst samples were prepared by using procedures described in the literature (3). CuCr-I was prepared by a simultaneous precipitation technique, which involves injecting two streams, a metal-bearing (Cu and Cr) solution and ammonia, into a tank at rates that maintain a constant pH. CuCr-II was prepared by a sequential method in which ammonium chromate solution was added to copper nitrate solution. C...

The present work demonstrates the rate-limiting effect of varying levels of both glycerine and monoglyceride through a series of batch hydrogenations of fatty dodecyl methyl ester, using copper chromite as the catalyst. Reactions were carried out at 3000 psig H 2 , 280°C with catalyst levels varying between 1.25 and 1.80%. With increasing contaminant levels of glycerine (0.0, 0.1, 0.5, 5 wt%), conversion of fatty methyl ester to alcohol is correspondingly reduced (95, 89, 80, 2 wt%). On a molar basis of contaminant, monoglyceride equally reduces the conversion of methyl ester to alcohol. In both cases the latent appearance of fatty-fatty ester results from the slower hydrogenation rate. Chemistry is proposed outlining the thermal decomposition of glycerine or glyceride to intermediate components (acetol and acrolein), leading to the generation of propanediols. Experimental studies indicate that diols effectively deactivate the copper chromite catalyst, limiting the rate of fatty methyl ester hydrogenation. Catalyst deactivation is not permanent, suggesting catalyst site blockage by physical adsorption of the polyhydroxyl components. The complete understanding of this interaction holds promise for the development of glycerine/monoglyceride-insensitive catalysts. In addition, a brief overview of methyl ester hydrogenation inhibition effects of some heteroelements, water, and soap is presented. FIG. 3. Dodecyl methyl ester hydrogenation (depletion) vs. time as a function of glycerine (Gly) contamination. FIG. 4. Dodecanol generation vs. time as a function of glycerine (Gly) contamination. FIG. 5. Dodecyl dodecanoate generation and depletion vs. time as a function of glycerine (Gly) contamination. JAOCS, Vol. 76, no. 8 (1999) SCHEME 2 FIG. 7. Hydrogenation of dodecyl methyl ester with time in the presence or absence of 1,2-propanediol.