微-介孔SAPO-11分子筛的合成及其临氢异构性能

Synthesis of micro-mesoporous SAPO-11 and its catalytic performance in hydroisomerization

采用水热合成法分别以酸性硅溶胶和介孔材料MCM-41作为硅源合成SAPO-11分子筛,与机械混合法合成的复合分子筛进行对比。。利用X射线衍射(XRD)、N2吸附-脱附、NH3程序升温脱附(NH3-TPD)以及扫描电子显微镜(SEM)分别对分子筛的晶相、孔道结构、酸性性质和形貌进行表征。以正十六烷为原料,评价铂负载量为0.5%的催化剂的临氢异构反应性能。结果表明,在SAPO-11分子筛中引入介孔材料MCM-41可以提供更大的比表面积和孔道,减小传质阻力,缩短异构烯烃中间体在孔道内的停留时间,提高目标产物收率。在340℃、1.5 MPa、WHSV=1.5 h^-1、V(H2):V(正十六烷)=1 000:1时,正十六烷转化率达到95.5%,异构十六烷选择性为98.9%。

SAPO-11 molecular sieves were synthesized by a hydrothermal method with mesoporous material MCM-41 and silica sol as silica sources,and their properties were compared with mechanically synthesized composite molecular sieves.The crystal phase,pore structure,acidity and morphology of zeolites were characterized by X-ray diffraction,N2 adsorption-desorption isothermal analysis,NH3-TPD and scanning electron microscopy,respectively.The catalytic hydroisomerization performance of SAPO-11 catalysts with0.5%Pt loading was evaluated with n-hexadecane as a model material.The results show that the introduction of mesoporous material MCM-41 in SAPO-11 molecular sieve can provide larger pores and surface area,reduce mass transfer resistance,shorten the residence time of isomeric olefin intermediates in the pores,and effectively improve catalytic activity of long chain alkanes in the hydroisomerization reaction.The n-hexadecane conversion rate is 95.5% and the selectivity of iso-hexadecane is 98.9% at the reaction temperature of 340℃,reaction pressure of 1.5 MPa,WHSV=1.5 h^-1 and V(H2):U(n-hexadecane)=1 000:1.