PREPARATION OF 1,4-CYCLOHEXANE DIMETHANOL BY CATALYTIC HYDROGENATION OF DIALKYL 1,4-CYCLOHEXANEDICARBOXYLATE

摘要

The continuous prodn. of 1,4-cyclohexanedimethanol having a predetermined trans:cis isomer ratio comprises (a) providing a hydrogenation zone contg. a charge of granular hydrogeneration catalyst selected from Cu-contg. catalysts and Gp. VIII metal-contg. catalysts capable of catalysing the hydrogenation of esters; (b) determining a Reference Activity (RA) of the catalyst by measuring the extent of conversion of the dialkyl 1,4-cyclohexanedicarboxylate to 1,4-cyclohexanedimethanol in the passage of a reaction mixt. comprising the dialkyl 1,4-cyclohexanedicarboxylate and a H2-contg. gas through the catalyst at a preselected feed temp., feed pressure, dialkyl 1,4-cyclohexanedicarboxylate feed rate, and H2-contg. gas:dialkyl 1,4-cyclohexanedicarboxylate molar ratio; (c) determining fan Effective Residence Time (ERT) for contact of the reaction mixt. at the preselected feed temp. and feed pressure with the catalyst at the RA which produced 1,4-cyclohexanedimethanol having he desired trans:cis isomer ratio; (d) forming a vaporous feed stream comprising the dialkyl 1,4-cyclohexanedicarboxylate and a H2-contg. gas having a preselected molar ratio; (e) feeding the vaporous feed stream to the hydrogenation zone at a constant temp. of 150-350 deg. C and which is above the dew point of the feed stream and at a constant pressure of 150-2000 psia at a rate which corresponds to an Actual Residence Time (ART) of the feed stream in contact with the catalyst which yields 1,4-cyclohexanedimethanol of the desired trans:cis isomer ratio; (f) recovering a prod. stream contg. 1,4-cyclohexanedimethanol; (g) monitoring the Actual Activity (AA) of the catalyst with passage of time by measuring the extent of conversion of the dialkyl 1,4-cyclohexanedicarboxylate to 1,4-cyclohexanedimethanol under actual operating conditions of feed temp., feed pressure, dialkyl 1,4-cyclohexanedicarboxylate feed rate, and H2-contg. gas:dialkyl 1,4-cyclohexanedicarboxylate molar ratio; and (h) adjusting at least one feed condition of the vaporous feed stream to the hydrogenation zone selected from (1) the dialkyl 1,4-cyclohexanedicarboxylate feed rate, and (2) the H2-contg. gas: dialkyl 1,4-cyclohexanedicarboxylate molar ratio; while maintaining the feed stream above its dew point to provide an ART which corresponds to the ERT required to provide 1,4-cyclohexanedimethanol having the desired trans:cis ratio in accordance with the relationship (I). The dialkyl cyclohexanedicarboxylate is selected from di(1-4C alkyl) cyclohexanedicarboxylates.