载体对Pt催化剂制备邻苯基苯酚催化性能的影响

分别以活性炭(AC)、γ-Al2O3、MgO、TiO2为载体,氯铂酸为活性金属前驱体,采用等体积浸渍法制得不同载体负载的Pt催化剂,考察了它们对环己烯基环己酮(dimer)脱氢制备邻苯基苯酚(OPP)的催化活性和选择性。并用X射线衍射(XRD)、X射线光电子能谱(XPS)、H2程序升温脱附(H2-TPD)、CO2程序升温脱附(CO2-TPD)等对催化剂进行表征。结果表明,载体对所制备的催化剂表面Pt含量、酸碱性和对氢吸附能力等微观性能有影响,以γ-Al2O3为载体制备的Pt-K/γ-Al2O3催化剂,由于催化剂表面Pt质量分数高达0.41%,碱性强和碱中心多,利于氢和中间产物在催化剂表面的吸附,从而提高环己烯基环己酮的转化率和OPP选择性。Pt/γ-Al2O3催化剂在LHSV 0.12 h-1、H2空速33 mL/(g.h)、反应温度380℃的条件下,在200 t/a的工业化装置运转8 000h后,环己酮二聚物转化率仍能达99%以上,OPP选择性达90%以上。

Effect of Supports on Catalytic Performance of Platinum Catalysts for preparing o-phenylphenol

Pt-K/AC,Pt-K/γ-Al2O3,Pt-K/MgO and Pt-K/TiO2 catalysts with different supports were prepared by impregnation method using AC,γ-Al2O3,MgO and TiO2 as the support,respectively,and H2PtCl6 as the precursor.The catalytic performance of the catalysts in preparing o-phenylphenol(OPP) through dehydrogenation of cyclohexanone dimers was evaluated in a fixed bed reactor.These catalysts were characterized by means of X-ray diffraction,X-ray photoelectron spectroscopy,H2 temperature programmed desorption and CO2 temperature programmed desorption.The results show that the Pt content,basicity and adsorption of hydrogen of the Pt catalysts were influenced by the different supports.Pt-K/γ-Al2O3 had the highest surface Pt content(0.41%),and more surface base sites were favorable to the adsorption of hydrogen and intermediate products and consequently increased the conversion of dimers and the selectivity for OPP.The conversion of the dimers and the selectivity of OPP were respectively over 99% and 90% with 0.12 h-1 of LHSV and 33 mL/(g·h) H2 flow rate at 380 ℃ over Pt-K/γ-Al2O3 catalyst during the pilot scale test of～8 000 h.