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Abstract

A continuous process is described for the production of 1,4-cyclohexanedimethanol (CHDM) having a desired or predetermined trans-:cis- isomer ratio by catalytic hydrogenation of a dialkyl 1,4-cyclohexanedicarboxylate in the presence of an ester hydrogenation catalyst. The process is capable of being operated for an extended period of time during which the hydrogenation catalyst declines in catalytic activity and comprises feeding a vaporous mixture of the dialkyl 1,4-cyclohexanedicarboxylate and hydrogen to a hydrogenation zone containing the hydrogenation catalyst and recovering CHDM product. The degree of conversion of the dialkyl 1,4-cyclohexanedicarboxylate at a particular combination of temperature and pressure is related to the trans-:cis- isomer ratio of the CHDM product and may be varied by adjusting at least one feed condition selected from (i) the dialkyl 1,4-cyclohexanedicarboxylate feed rate and (ii) the hydrogen-containing gas:dialkyl 1,4-cyclohexanedicarboxylate molar ratio. As catalyst activity declines during operation of the process over an extended period of time at a particular combination of temperature and pressure, the degree of conversion of the dialkyl 1,4-cyclohexanedicarboxylate and/or the trans-:cis- isomer ratio of the CHDM product may be maintained at a constant value by adjusting at least one of the feed conditions referred to above. The determination of the Actual Activity and Reference Activity of the catalyst and the Actual and Effective Residence Times are included in the hydrogenation process.

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