Characterization of fractal surface roughness and its influence on diffusion and reaction
Characterization of fractal surface roughness and its influence on diffusion and reaction
复制标题
DOI：
10.1016/s0927-7757(01)00639-2
复制
发表时间：
2001-08-31
影响因子：
5.2
通讯作者：
Coppens, MO
中科院分区：
文献类型：
--
作者：
Coppens, MO
为了研究表面粗糙度对多孔“非晶”催化剂中扩散和反应的影响，需要一个真实的粗糙度模型。通过结合小角度和广角 X 射线散射，可以证实吸附实验表明表面通常是分形的，因为这些技术允许在更广泛的尺度上测量表面和体积特性，从而可以揭示完整的缩放状态（如果存在）。可以确定分形维数，以及分形尺度范围的内部和外部截止。沸石没有发现显着的分形表面粗糙度，但对于介孔γ-Al(2)O(3)、催化重整和加氢处理催化剂等材料却显示出明显的分形表面粗糙度。类似于催化剂制备中使用的溶胶-凝胶合成过程中发生的聚集现象的模拟结果带来了更多的见解。催化剂或催化剂载体在分子尺度上的分形表面粗糙度对化学反应的转化率和选择性具有显着影响，特别是当它们受到克努森扩散限制时。这种效应在工业反应器的规模上都能感受到，这意味着改变分形表面粗糙度可以提高工业过程的性能。 (C) 2001 Elsevier Science B.V. 保留所有权利。
To investigate the effect of surface roughness on diffusion and reaction in porous 'amorphous' catalysts, a realistic model of roughness is necessary. By combining small-angle and wide-angle X-ray scattering, the suggestion from adsorption experiments that the surface is often fractal can be confirmed, since these techniques allow to measure the surface and bulk properties over a wider range of scales, so that the complete scaling regime, if present, can be revealed. The fractal dimension can be determined, as well as the inner and outer cutoff of the fractal scaling regime. No significant fractal surface roughness is found for zeolites, but is shown for such materials as a mesoporous gamma -Al(2)O(3), catalytic reforming and hydrotreating catalysts. Results from the simulation of aggregation phenomena similar to those occurring during the sol-gel synthesis used in catalyst preparation lead to additional insights. The fractal surface roughness of a catalyst or catalyst support on molecular scales has a significant influence on the conversions and selectivities of chemical reactions, especially when they are limited by Knudsen diffusion. This effect is felt up to the scale of industrial reactors, which implies that changing the fractal surface roughness can improve the performance of an industrial process. (C) 2001 Elsevier Science B.V. All rights reserved.