Acidity and catalytic activity of zeolite catalysts bound with silica and alumina

Show full item record

Title: Acidity and catalytic activity of zeolite catalysts bound with silica and alumina
Author: Wu, Xianchun
Abstract: Zeolites ZSM -5 (SiO2 /Al2O3=30 ~280 ) and Y (SiO2 /Al2O3=5 .2 ~80 ) are bound with silica gel (Ludox HS -40 and Ludox AS -40 ) and alumina ( ? - Al2O3 and boehmite ) by different binding methods , namely , gel -mixing , powder -mixing and powder -wet -mixing methods . The acidities of the bound catalysts and the zeolite powder are determined by NH3 -TPD and FTIR . The textures of these catalysts are analyzed on a BET machine with nitrogen as a probe molecule . The micropore surface area and micropore volume are determined by t -plot method . Micropore volume distribution is determined by Horvath -Kawazoe approach with a cylindrical pore model . Mesopore volume distribution is determined by BJH method from the nitrogen desorption isotherm . Silica from the binder may react with extra -framework alumina in zeolites to form a new protonic acid . SiO2 -bound catalysts have less strong acidity , Bronsted acidity and Lewis acidity than the zeolite powder . Also , the strength of strong acid sites of the zeolites is reduced when silica is embedded . Micropore surface area and micropore volume are reduced by about 19 % and 18 % , respectively , indicating some micropores of ZSM -5 are blocked on binding with silica . SiO2 -bound ZSM -5 catalysts have less catalytic activity for butane transformation (cracking and disproportionation ) and ethylene oligomerization than ZSM -5 powder . When alumina is used as a binder , both the total acid sites and Lewis acid sites are increased . Micropore surface area and micropore volume of ZSM -5 powder are reduced by 26 % and 23 % , respectively , indicating some micropores of ZSM -5 are blocked by the alumina binder . Alumina -bound catalysts showed a lower activity for butane transformation and ethylene oligomerization than ZSM -5 powder . Alkaline metals content in the binder is a crucial factor that influences the acidity of a bound catalyst . The metal cations neutralize more selectively Bronsted acid sites than Lewis acid sites . Alkaline metal cations in the binder and micropore blockage cause the bound catalysts to have a lower catalytic activity than the zeolite powder .
URI: http : / /hdl .handle .net /1969 .1 /561
Date: 2004-09-30

Citation

Acidity and catalytic activity of zeolite catalysts bound with silica and alumina. Available electronically from http : / /hdl .handle .net /1969 .1 /561 .

Files in this item

Files Size Format View
etd-tamu-2003C-CHEN-Wu-1.pdf 3.667Mb application/pdf View/Open

This item appears in the following Collection(s)

Show full item record

Search DSpace

Advanced Search

Browse