Van der Mynsbrugge Jeroen, Janda Amber, Lin Li-Chiang, Van Speybroeck Veronique, Head-Gordon Martin, Bell Alexis T
Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, 94720, USA.
Center for Molecular Modeling, Ghent University, Tech Lane Ghent Science Park Campus A, Technologiepark 903, 9052, Zwijnaarde, Belgium.
Chemphyschem. 2018 Feb 19;19(4):341-358. doi: 10.1002/cphc.201701084. Epub 2018 Jan 18.
Acidic zeolites are effective catalysts for the cracking of large hydrocarbon molecules into lower molecular weight products required for transportation fuels. However, the ways in which the zeolite structure affects the catalytic activity at Brønsted protons are not fully understood. One way to characterize the influence of the zeolite structure on the catalysis is to study alkane cracking and dehydrogenation at very low conversion, conditions for which the kinetics are well defined. To understand the effects of zeolite structure on the measured rate coefficient (k ), it is necessary to identify the equilibrium constant for adsorption into the reactant state (K ) and the intrinsic rate coefficient of the reaction (k ) at reaction temperatures, since k is proportional to the product of K and k . We show that K cannot be calculated from experimental adsorption data collected near ambient temperature, but can, however, be estimated accurately from configurational-bias Monte Carlo (CBMC) simulations. Using monomolecular cracking and dehydrogenation of C -C alkanes as an example, we review recent efforts aimed at elucidating the influence of the acid site location and the zeolite framework structure on the observed values of k and its components, K and k .
酸性沸石是将大分子烃裂解为运输燃料所需的较低分子量产物的有效催化剂。然而，沸石结构影响布朗斯台德质子催化活性的方式尚未完全明确。表征沸石结构对催化作用影响的一种方法是在非常低的转化率下研究烷烃裂解和脱氢，在这种条件下动力学已得到很好的定义。为了理解沸石结构对测得的速率系数（k）的影响，有必要确定在反应温度下吸附到反应物状态的平衡常数（K）和反应的本征速率系数（k），因为k与K和k的乘积成正比。我们表明，K不能从接近环境温度下收集的实验吸附数据计算得出，但可以通过构型偏置蒙特卡罗（CBMC）模拟准确估计。以C -C烷烃的单分子裂解和脱氢为例，我们回顾了最近旨在阐明酸位点位置和沸石骨架结构对k及其组分K和k观测值影响的研究工作。
