载体成型方法对丙烷脱氢催化剂性能的影响

Effect of support molding method on the performances of propane dehydrogenation catalyst

焙烧拟薄水铝石得到氧化铝粉末,分别采用压片成型、挤条成型和油柱成型3种方法得到不同的氧化铝载体颗粒。分别以氧化铝粉末和成型氧化铝为载体制备Pt-Sn-Na/Al2O3催化剂,并考察了催化剂在丙烷脱氢制丙烯(PDH)反应中的催化性能。通过XRD、N2吸附-脱附和颗粒强度测定等表征手段研究了氧化铝载体和Pt基催化剂的物理结构,借助TG-DTG表征研究了反应过程中催化剂的积碳特征。实验结果表明,3种成型过程均会导致氧化铝孔道尺寸变小和比表面积下降,其中影响最显著的是挤条成型方法。Pt-Sn-Na/Al2O3催化剂在PDH反应中的催化性能与氧化铝载体颗粒的物理结构有直接关系。孔体积和孔径较大的氧化铝载体有利于活性组分分散,使得制备的催化剂具有更高的丙烷转化率和丙烯选择性。使用挤条成型方法得到的氧化铝制备PDH催化剂时,催化剂在反应中易积碳;而油柱成型方法得到的氧化铝载体则有助于抑制反应中积碳物种的沉积。

A kind of alumina powder is obtained by calcining a pseudo-boehmite,and different alumina support particles are obtained by compression molding,extrusion molding and oil column molding.Four Pt-Sn-Na/Al2O3 catalysts were prepared by using alumina powder and formed alumina samples as supports.The catalytic performances of the catalysts in the reaction of propane dehydrogenation to propylene(PDH)were investigated.The physical structures of the alumina supports and Pt-based catalysts were studied by XRD,N2 adsorption-desorption,and particle strength measurement.The carbon deposition characteristics of the catalysts during the PDH reaction were studied by thermal analysis.The result shows that the three molding methods all lead to the reduction of alumina pore size and specific surface area,in particular,extrusion molding method.The catalytic performances of Pt-Sn-Na/Al2O3 catalyst for PDH reaction are directly related to the physical structure of alumina support particles.The alumina support with larger pore size and pore size is conducive to the dispersion of active components,which makes the prepared catalyst have higher propane conversion and propylene selectivity.The catalyst prepared from alumina by extrusion molding is easy to accumulate carbon in the PDH reaction.On the contrary,the alumina support obtained by the oil column forming method is helpful to inhibit the deposition of carbon species.