1,2-环己二醇脱氢制邻苯二酚镍基催化剂的研究

Ni-Based Catalysts for Dehydrogenation of 1,2-Cyclohexandiol to Catechol

以硝酸镍为镍源,分别以硅藻土、活性炭、MgO和γ-Al2O3为载体,采用均相沉淀法与等体积浸渍法制备了负载型镍基催化剂,考察了所制备的催化剂对1,2-环己二醇脱氢制邻苯二酚反应的活性和选择性,并对催化剂进行了BET,XRD,SEM等表征。实验结果表明,催化剂的比表面积与脱氢活性无对应关系,但平均孔径大有利于提高邻苯二酚的选择性;沉淀剂影响催化剂的微孔结构和粒径分布。以硅藻土为载体、NH3.H2O+NH4HCO3为沉淀剂制备的镍基催化剂,镍物种的晶粒度小、分散度较高,催化剂的平均孔径大,表现出良好的活性和选择性,在320℃、101kPa、液态空速2.6h-1、N2流量30mL/min、n(1,2-环己二醇)∶n(H2O)=1∶4的条件下,1,2-环己二醇的转化率达到98.3%,邻苯二酚的选择性为85.2%。

Supported nickel-based catalysts were prepared through homogeneous precipitation method or isochoric impregnation method using nickel nitrate as nickel source, and kieselguhr, activated carbon, MgO, or γ-Al2O3 as supports. These catalysts were characterized by means of BET, XRD and SEM. Their properties in dehydrogenation of 1,2-cyclohexandiol to catechol was evaluated in a fixed-bed reactor. Results showed that activities of the nickel-based catalysts were not associated with their specific surface areas, but selectivity to catechol was obviously enhanced by the catalyst with large average pore diameter. Effects of precipitant type on pore structures and particle dispersions of the catalysts were significant. Dispersity of active nickel species was high and pore size was large in nickel-based catalysts prepared with kieselguhr as support and NH3 ·H2O ＋ NH4HCO3 as precipitant, which exhibited high activity and selectivity in the dehydrogenation. Conversion of 1,2-cyclohexandiol and selectivity to catechol in the dehydrogenation could reach 98.3% and 85.2% respectively under conditions of 320 ℃, LHSV 2.6 h^-1, 101 kPa, N2 30 mL/min and n（1,2-cyclohexandiol） ： n（H20） = 1：4.