Simulational And Experimental Study On The Adsorption Of Some Gases On ZSM-5 Zeolite

ZSM-5 zeolite is a wide-used kind of zeolite with high SiO2/Al2O3 ratio. The unique pore system of this zeolite leads to its excellent thermal stability, which is suitable for separation of many important industrial organic substances. Having high catalytic activity and high selectivity of modified zeolites, the zeolite has been applied to produce the petrochemical products, fine chemicals and in the environmental protection. Thus, it is of great theoretical and practical significance to research its adsorption characters of ZSM-5 zeolite.In this work, both experiment and simulation have been used to study the adsorption of the sorbates with small molecular weight and on ZSM-5 zeolite as sorbent. Based on the experiment, the reliability and feasibility of molecular simulation to prodict the adsorption rules have been investigated.At the temperature of 77K, the adsorption isotherms of some gases of nitrogen, argon, oxygen and hydrogen on ZSM-5 zeolite have been studied experimentally. Adsorption isotherms of the four gases have been typed. The non-linear regression of the adsorption isotherms have been carried out according to Langmuir equation. It is indicated that the adsorption isotherms of nitrogen, argon and oxygen are recognised as Langmuir monolayer adsorption. The adsorption isotherm of hydrogen on ZSM-5 zeolite fits Langmuir function under low pressure(0-2.5kPa), but does not fit the function in the whole pressure(0-80kPa) because of the multilayer adsorption.At the temperature of 50K, 77K and 100K, the adsorption isotherms of nitrogen, argon, oxygen and hydrogen on ZSM-5 zeolite have been studied by the simulation based on the GCMC method, using the forcefields of COMPASS and UNIVERSAL, respectively. It is found that the adsorbed quantity of these four gases on ZSM-5 zeolite decreases with the increased temperature, and increases with the enhanced pressure, which matches the experimental results.The comparison between simulations and experiments has been carried out in order to validate the reliability of GCMC.method. It is revealed that the discrepancy between simulation and experiment is considerable in the adsorption system of hydrogen on ZSM-5 zeolite. In the other three adsorption systems, the deviation between simulations and experiments is about 10%, and the cause for this deviation has been explored, i. e., the impurity and fugacity coefficient of sorbates, and the crystallinity, impurity and cations of ZSM-5 zeolite crystal may result in the deviaton. After the modification with fugacity coefficient and crystallinity, the deviation is reduced. It is illuminated that the GCMC simulation method is of reliability and feasibility to simulate the adsorption of gas on ZSM-5 zeolite.