Study On Preparation Of 1,4 - Cyclohexanedimethanol By Hydrogenation Of 1,3 - Cyclohexanedicarboxylate With High Efficiency Cu - Based Catalyst

In the field of polymer industry, 1,4-cyclohexanedimethanol（CHDM） occupies an important position especially for the synthesis of highly valued polyesterand polyester fibers. Because of its high symmetry, CHDM is preferred to ethylene glycol and other polyol in the production of polyester resins with good thermal stability and thermoplastic.Industrially, CHDM is prepared by a two-step process using reactors. The first step is the conversion of DMT into DMCD by the hydrogenation of the phenyl group, the second one is the scheduled conversion of carboxylic ester to corresponding alcohol, resulting in the production of CHDM. With regard to the hydrogenation of DMT, many procedures used Pd/Al₂O₃ as the catalysts. Esters are normally produced by catalytic hydrogenation over traditional Cr₂O₃-promoted Cu-based heterogeneous catalysts. In consideration of the toxicity of such types of Cr-containing catalysts can cause a serious of environmental pollution, it is imperative to look for a Cr-free catalyst.Therefore, different promoters and layered double hydroxides precursors were used to obtain highly specific surface area copper-based catalyst, which exhibited excellent performance in the catalytic hydrogenation of DMCD. Through a series characterization, the relationship between the structure and catalytic performance had been disclosed.The Cu_xMg_12-xAl₆O₂₁ catalyst for hydrogenation of DMCD was prepared by a co-precipitation method. The results showed that Cu₃Mg₉Al₆O₁₈ exhibited the best activity. When the reaction temperature was 180℃, and the reaction pressure was 4 MPa, a DMCD conversion over 99% along with CHDM selectivity of 96% were achieved. In addition, there was no significant decrease in either the activity or the selectivity when the catalysts remained during nearly 500 h test.A serious of Cu₃Zn_xMg_9-xAl₆O₁₈ catalysts with different Zn²⁺/Mg²⁺ ratios were prepared by co precipitation method with the addition of Zn as additive.The optimum operating conditions were as follows: reaction temperature of 170℃, reaction pressure of 4 MPa, and LHSV=1.6×10^-7 mol DMCD g Cu^-1 s^-1. Compared with our previous work, the catalytic activity and stability were improved with higher LHSV and lower temperature.