Esters hydrogenolysis

Alcohols are the most frequently formed products of ester hydrogenolysis. The hydrogenation of esters to alcohols is a reversible reaction with alcohol formation favored at high pressure, ester at low pressure (/). Copper chromite is usually the catalyst of choice. Details for the preparation of this catalyst (/7) and a detailed procedure for hydrogenation of ethyl adipate to hexamethylene glycol (/[Pg.80]

Benzyl ester, hydrogenolysis of, 1034 Benzyl group, 518 Benzylic, 377... 

A low-cost route to 1,4-butanediol and tetrahydrofuran based on maleic anhydride has been disclosed (Davy process).343,344 Here dimethyl or diethyl maleate is hydrogenated over a copper catalyst. Rapid saturation of the C—C double bond forms diethyl succinate, which subsequently undergoes further slower transformations (ester hydrogenolysis and reduction as well as dehydration) to yield a mixture of y-butyrolactone, 1,4-butanediol, tetrahydrofuran, and ethanol. After separation both ethanol and y-butyrolactone are recycled. 

Methyl Ester Hydrogenolysis. The flow sheet for the continuous methyl ester, catalyst slurry process is shown in Figure 1. The dry methyl ester, hydrogen, and catalyst slurry are fed cocurrently to a series of four vertical reactors operated at 250—300°C and 20,700 kPa (3000 psi). The reactors are unagitated, empty tubes, designed to provide adequate residence time, minimum backmixing, and a reasonable column height. Fresh catalyst powder is... 

Cu-. [M THarshaw] Copper chromite cat yst for dehydrogenation of alcohols, decomposition of methanol, oxygen scavenging, dehydrogenation of piperazines to pyrazines, methyl ester hydrogenolysis and dehydrogenation. 

The use of copper-based catalysts for the reactions of ester hydrogenolysis and alcohol dehydrogenation is well established [2-26, 30,31]. Raney -type skeletal copper catalysts are widely used in these reactions [5-11,17-26,30,31]. However, significant catalyst deactivation is experienced [5-6,25-29]. Evans et al studied the hydrogenolysis of formates in the gas phase over a variety of copper-based catalysts, including skeletal copper and copper chromite... 

The results from the hydrogenolysis experiments indicate that the Cr203 promoted skeletal Cu catalysts have great potential for application in industrial processes for ester hydrogenolysis. 

A. Bliek, The relation between reduction temperature and activity in copper catalysed ester hydrogenolysis and methanol synthesis. Catal Lett., 36 175-182,... 

D.S. Brands, E.K. Poels, A. Bliek, Ester hydrogenolysis over promoted CU/S1O2 catalysts. Appl. Catal. A General, 184 279-289,1999. 

M.A. Kohler, N.M. Cant, M.S. Wainwright and D.L. Trimm, The mechanism of the catalytic chemistry of ester hydrogenolysis on copper surfaces. Proc. Int. Congr. Cato/., 9 1043-1050, 1988. 

Scheme 18.18 Mechanism of esters hydrogenolysis on isolated Rh atoms.

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