SAPO分子筛的酸性及孔道分布对丁烷异构脱氢反应的影响

Effects of Acidity and Pore Structure of SAPO Molecular Sieves on Dehydroisomerization of n-Butane to Isobutene over Pd/SAPO Catalysts

合成了四种磷铝及硅磷铝系列分子筛 ,并用XRD表征了分子筛的晶体结构 ,用X荧光光谱测定了其元素组成 ,用NH3 TPD和物理吸附考察了其酸性和孔道分布 .考察了以合成的分子筛为基质制备的催化剂上丁烷异构脱氢反应的性能 .结果表明 ,以弱酸性的SAPO 5分子筛和孔口狭窄的SAPO 34分子筛为载体的催化剂 ,它们的催化性能较差 ;以十元环的SAPO 11分子筛为载体的催化剂显示出较高的活性和选择性 .同时 ,考察了不同分子筛催化剂上Pd金属粒子的分散状态 。

Several aluminophosphate and silicoaluminophosphate molecular sieves were synthesized. The XRD results indicated that the samples have different crystal structure. The acidity and pore distribution of the samples were measured by using NH3-TPD and physical adsorption of nitrogen. The supported Pd catalyst samples were prepared based on the molecular sieves and used for dehydroisomerization of n-butane to isobutene. Poor activity and selectivity for isobutene were obtained over Pd/SAPO-5 catalyst with weak acidity and over Pd/SAPO-34 catalyst with narrow pore opening. Pd/SAPO-11 with 10-member ring pore opening showed the highest activity and selectivity for isobutene. Based on the characterization data and reaction results, the effects of acidity and pore structure of the catalyst samples on their catalytic performance were discussed.