Preparation And Catalytic Properties Of Metallic Catalyst Materials For Hydrogenation Of Dimethyhl Terephthalate

1,4-cyclohexanedimethanol (CHDM) and 1,4-dimethyl cyclohexane dicarboxylate (DMHT) are important raw materials for industrial production of polyester material, wherein DMHT is an intermediate for the synthesis of polyester, polyamide resin and medicine. Traditionally, CHDM is produced by two-step process from the hydrogenation of DMT. In the first step, DMT is converted into DMHT by Pd-based catalyst, and then CHDM is generated by Cu-Cr catalyst. However, the complicated process, the expensive Pd-based catalyst and poisonous Cr-based catalyst limit its industrial application. So, the development of new catalyst materials and technology will be conducive to the industrialization of DMT hydrogenation.In this thesis, trimetallic RuPtSn/Al2O3 supported catalyst were prepared and were used to convert DMT into CHDM by one-step method. The effect of catalyst composition on the reaction performance and the operating conditions were aslo explored. Meanwhile, based on the crystal structure of the hydrotalcite (layered double hydroxides, referred as LDHs). The Ni/Al2O3 catalyst materials with active component highly dispersed were prepared use Ni2Al-LDH as precursor. The catalysts were used for the liquid phase catalytic hydrogenation of DMT into DMHT. The effect of preparation conditions on the catalyst structure and reaction performance were aslo studied. The results of research are as follows:1. The RuPtSn/Al2O3 catalyst materials prepared by the traditional co-impregnation method was used to convert DMT into CHDM under the two stage process of controlling temperature and pressure in one reactor. The reaction results showed that the addition of metal Pt into RuSn/Al2O3 could improve the dispersibility of the catalyst and reducing the metal particles and thus increased the yield of CHDM (75.1%). The active sites of RuPtSn/Al2O3 catalyst were proposed according to the reaction and related characterization results. "RuPt site" and "RuSn site" both had synergies effect, the former one promoted the generation of DMHT, and the latter one for CHDM.2. The Ni/Al2O3 catalyst materials by in-situ (one step) or calcination-reduction (two step) method were prepared use Ni2Al-LDH as precursor. The catalyst materials were used for the liquid phase catalytic hydrogenation of DMT into DMHT. The results showed that Ni/Al2O3 catalyst material prepared by in-situ (500 ℃) can converted DMT into DMHT more effectively than the other two catalysts for its larger surface area and smaller particle size of the active metal Ni in ethyl acetate as solvent. However, Ni/Al2O3 catalyst material prepared by calcination-reduction is the best one for Ni/NiO composite system in isopropanol as solvent. When the reaction temperature was lower to 110 ℃, DMT was completely converted and selectivity of DMHT reached 93%.