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Preparation And Performance Of Catalytically Active ZSM-5Films

Posted on:2013-08-21Degree:MasterType:Thesis
Country:ChinaCandidate:H H WuFull Text:PDF
GTID:2251330401451707Subject:Chemistry
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The pore size of ZSM-5crystals with MFI structure is about0.55nm (close to the kinetic diameter of many molecules), which has good thermal stability and catalytic properties. ZSM-5zeolite has been widely used for petroleum industry and is an ideal inorganic membrane materials. These ZSM-5catalytic films have shown good potentials for endothermic fuels.This paper is consisted of three parts:(Ⅰ) Preparation and catalytic properties of ZSM-5films using FeCrAl grids as supports by in situ growth method;(Ⅱ) Preparation and characterization of ZSM-5films on the surface of high temperature alloy substrates; and (Ⅲ) Catalytic properties of ZSM-5films on the wall of tubular alloy substrates. The details are discussed below:Firstly, ZSM-5catalytic films have been synthesized using FeCrAl grids as supports by in-situ growth method. These films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The catalytic properties of these films were characterized using n-octane cracking as a model reaction. The results have shown that the conversion extent of n-octane on ZSM-5films was higher than that of thermal cracking under otherwise identical conditions. The catalytic activities of ZSM-5films seemed to be dependant on the amount of zeolite crystals grown on the support and the n(Si)/n(Al) ratio of these crystals. These properties could be controlled by adjusting the synthesis conditions.Secondly, in situ growth of ZSM-5films on the surface of high temperature alloy substrates of various shapes (discs and tubes) was investigated. Crystalline structure and morphology of zeolite crystals grown on the substrate were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The results have shown that several factors such as pretreatment temperature of the substrate, time and times of growth had influence to various degree on in situ growth of ZSM-5crystals on the surface of alloy substrates. A dense ZSM-5film could be grown on the wall of a long (750mm) alloy tube with an inner diameter of1mm using the repeated in situ hydrothermal method. Thirdly, catalytic properties of ZSM-5films on the wall of tubular alloy substrates for the endothermic fuel (n-heptane) were discussed. The results have shown that several factors such as pretreatment temperature of the substrate and times of growth had influence to the conversion rates of heptane, the average formation rates of gaseous products and the distribution of gaseous products.
Keywords/Search Tags:ZSM-5films, Catalytic cracking, FeCrAl grids, Alloy Substrates
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