催化剂表面分形结构对催化反应的影响

用溶胶－凝胶方法制备了ＳｉＯ２并以其及另一种ＳｉＯ２气凝胶作载体，用浸渍法制备了两种铑基催化剂。以ｎ－Ｃ５～Ｃ８烷烃为探针分子，测得两种催化剂的表面分形维数Ｄ分别为３和２。在两种催化剂上，ＣＯ加氢和丙烷氢解反应的选择性没有显著差别，但在Ｄ＝２的催化剂上，ＣＯ加氢和丙烷氢解反应的速度显著高于Ｄ＝３的催化剂

EFFECT OF SURFACE FRACTAL DIMENSION ON CATALYTIC REACTIONS

A porous SiO2 was prepared by a sol-gel route, and it and another aerosil SiO2 were used as supports for the preparation of two catalysts, 2Rh4CeO2/SiO2(S) and 2Rh4CeO2/SiO2(A) by impregnation, respectively The surface dimensions, D , of the two catalysts were measured by the absorption of a group of C5C8 normal alkanes and the catalytic properties in CO hydrogenation and propane hydrogenolysis were studied D =2 and 3 were obtained on the aerosil and the porous SiO2 supported catalysts, respectively, indicating that the surface of the aerosil SiO2 supported catalysts is smooth, while that with porous SiO2 as support goes to another extreme, very rough There is no much difference among the selectivities of both CO hydrogenation and propane hydrogenolysis However, on the catalyst with D =2, both CO hydrogenation and propane hydrogenolysis show much higher reaction rates than on the one with D =3 Calculation shows that on D =3 fractal surface, only 59% and 43% active centers can be reached by CO and C3H8, respectively This might be why the catalyst with TBXD =2 was more active than the one with DTBZ=3