Prediction of Sorption and Diffusion in Zeolite Catalysts

这是对碳氢化合物在五烷基沸石中的吸附和扩散现象的探索性研究。这是为了从微观结构和化学组成中对这些现象进行定量预测而开发可靠方法的第一步。作为测试用例，对甲烷/硅石体系和丁烷/硅石体系进行了深入研究。使用强大的计算技术（构型积分评估、分子动力学、大正则系综蒙特卡罗）在原子水平上模拟这些系统，推导平衡吸收等温线和自扩散系数，并扩展对潜在分子机制的基本理解，远远超出其目前的状态。理论预测将根据现有的实验证据进行检验。此外，将开始一项实验工作，以制备具有良好特征的大晶体硅石样品，并通过重量技术直接测量吸附和扩散。本初步研究的分子模拟方法具有较强的通用性。一旦它们的预测能力在定义良好的测试系统中建立起来，它们在各种沸石和山梨石上的应用将是直截了当的。本研究的长期目标是获得自一致的吸附和扩散的微观图像，用于分离和催化应用的分子筛系统的分子工程设计。

This is an exploratory study of the phenomena of sorption and diffusion of hydrocarbons in pentasil zeolites. It is undertaken as a first step towards the development of reliable methods for the quantitative prediction of these phenomena from microscopic structure and chemical constitution. The systems methane/silicalite and butane/silicalite are investigated in depth, as test cases. Powerful computational techniques (evaluation of configurational integrals, molecular dynamics, grand canonical ensemble Monte Carlo) are employed to simulate these systems at an atomistic level, deduce equilibrium sorption isotherms and self-diffusion coefficients, and extend the fundamental understanding of underlying molecular mechanisms far beyond its present status. Theoretical predictions will be checked against available experimental evidence. In addition, an experimental effort will be initiated for the preparation of well characterized, large crystal silicalite samples and the direct measurement of sorption and diffusion by gravimetric techniques. The molecular simulation methods developed in this preliminary study are quite general. Once their predictive power is established in well defined test systems, their application to a wide variety of zeolites and sorbates will be straightforward. The long range objective of this research is to arrive at a self- consistent microscopic picture of sorption and diffusion, useful for the molecular engineering design of zeolite systems for separations and catalytic applications.