Catalytic Hydrogenation Of Dimethyl O-,M-,P-Phthalate Over Modified Skeletal Nickel

Dimethyl cyclohexanedicarboxylates are important intermediates in organic synthesis, which are widely used in the preparation of fragrance, flavor or serve as a modifier of polymer. By now, researchers have done many investigations about the hydrogenation of dimethyl phthalate to dimethyl cyclohexanedicarboxylate. In order to reduce catalyst cost and loss of noble metal, it is urgent to develop more efficient, inexpensive catalyst to replace the noble metal catalyst.The Mo modified skeletal Ni catalyst (QS-Ni) was prepared by quenching technique, and it was employed for the catalytic hydrogenation of dimethyl phthalate (DMP), dimethyl isophthalate (DMIP) and dimethyl terephthalate (DMT). Effects of solvent, reaction temperature, H2 pressure, initial concentration of substrate and amount of catalyst have been investigated. Under optimal reaction conditions, the stability of QS-Ni has been tested. The catalyst showed excellent catalytic activity and high selectivity to desired product.QS-Ni was proved to be very active for the hydrogenation of DMP to dimethyl 1,2-cyclohexanedicarboxylate. Under optimal reaction conditions:c(DMP) =2.7mol/L, m(DMP):m(QS-Ni)=20:1,100℃,4.0MPa H2 pressure, the selectivity was up to 99.3% with 100% conversion of DMP in isopropanol solvent. The catalyst still exhibited excellent activity and selectivity after QS-Ni was recycled for 10 times.The modified skeletal Ni was proved to be also active for the hydrogenation of DMT to dimethyl 1,4-cyclohexanedicarboxylate (DMCD). Under optimal reaction conditions: c(DMT)=1.0mol/L, m(DMT):m(QS-Ni)=4:1,95℃,6.0MPa H2 pressure, the selectivity of DMCD was up to 92.3% in 140min with 100% conversion of DMT in isopropanol solvent. After QS-Ni catalyst was recycled for 16 times, conversion of DMT and selectivity to DMCD still remain at 99.3% and 92.0%, respectively.We also investigated the catalytic hydrogenation of DMIP to dimethyl 1,3-cyclohexanedicarboxylate over QS-Ni. The product selectivity was up to 94.3% with 100% conversion of DMIP under 90℃,5.0MPa H2 pressure in isopropanol solvent.