Synthesis Of Silicalite-1 Zeolite Membrane And The Design & Application Of Silicalite-1 Core-Shell Catalyst

There is substantial interest in Direct Internal Reforming-Molten Carbonate Fuel Cell (DIR-MCFC) as potential alternative to thermoelectric plants for distributed electrical power generation.With internal nature gas or methane fuel reforming,the DIR-MCFC eliminates the need for an external reformer,has the advantage of higher energy and system efficiency as well as maximizes hydrogen production and improves carbon dioxide managements in the fuel cell.But the nickel catalyst for methane steam reforming deteriorates under the high working temperature in the DIR-MCFC,which negatively affects its operation and performance.Hence,improving alkali resistance ability of the reforming catalyst becomes the key act to extend DIR-MCFC working life,reduce capital cost and maintain efficiency of the system.Zeolite membrane or film possesses uniform and well-defined micropores system with pores of nearly molecular size,and was widely used for adsorption,catalysis as well as gas separation due to its good chemical stability,intense mechanical strength and capability of working at high temperature.Meanwhile,with the development of membrane technology and materials science,zeolite membrane or film also becomes applicable as core-shell structure, hollow sphere and capsule except for conventional application.In this paper,Silicalite-1 membrane encapsulated core-shell nickel catalyst was designed to solve the problem of catalyst poisoning by alkali in DIR-MCFC,and then was conducted for out-of-cell alkali treatment as well as steam reforming of methane reaction(SRM).(1) Silicalite-1 crystals with size of 150 nm were synthesized and characterized by XRD and SEM to evaluate its morphology,particle size and crystal lattice.(2) A novel method for Silicalite-1 zeolite crystals assembly on SiO₂ beads,nickel grid and foam was designed using 3-aminopropyltrimethoxysilane(AP-TMS) as covalent-linkers. Using monolayer of Silicalite-1 crystals as seeds,Silicalite-1 membrane was secondarygrown on to the substrates by hydrothermal treatment.Synthesis parameters such as substrate property,precursor composition,crystallization time and temperature were investigated.The process of Silicalite- 1 membrane synthesis was explained by Vander Drift evolution theory.(3) Ni-SiO₂ and Ni-Al₂O₃ reforming catalyst(12.5wt%) was prepared by incipient wetness impregnation method.After assemble of monolayer of Silicalite-1 crystals on as-synthesized catalyst,Silicalite-1 membrane was grown by hydrothermal treatment to form Silicalite-1/Ni-SiO₂ and Silicalite-1/Ni-Al₂O₃ core-shell catalyst.SEM measurements were used to characterize membrane morphology and thickness.S 150-24å’ŒS 175-24 samples were conducted in out-of-cell alkali treatment as well as SRM(pattern A and pattern B).It was indicated that Silicalite-1/Ni-SiO₂ and Silicalite-1/Ni-Al₂O₃ core-shell catalyst showed good alkali resistance performance with methane conversion of 16%and 58%which is much higher than that of 2%and 8%for fresh catalyst,respectively.