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Title: Role of external surface sites in shape-selective catalysis over zeolites

Abstract

A simple kinetic model is developed having an analytic solution that explains and quantifies isomer shape selectivity in zeolite catalysis. The model, based on the assumption of existence of both shape-selective (e.g., para-selective) internal catalytic sites and nonselective (e.g., non-para-selective) external sites, addresses the preferred overall formation of the isomer that diffuses more rapidly in the intracrystalline space, as well as the decline in shape selectivity with conversion. Exemplified for the production of xylene from toluene over HZSM-5 catalysts, the model gives a very good fit with experimental data of toluene disproportionation. Lack or loss of para selectivity is thus explained as resulting from reactions occurring on the external surface of the zeolite. The model predicts maxima in {ital p}-xylene production, subject to system variables, as a function of reaction time.

Authors:
 [1]
  1. (Pittsburgh Univ., PA (USA). Dept. of Chemical and Petroleum Engineering)
Publication Date:
OSTI Identifier:
6464532
Resource Type:
Journal Article
Journal Name:
Industrial and Engineering Chemistry Research; (USA)
Additional Journal Information:
Journal Volume: 29:9; Journal ID: ISSN 0888-5885
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; 10 SYNTHETIC FUELS; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; XYLENES; PRODUCTION; ZEOLITES; CATALYTIC EFFECTS; CATALYTIC CONVERTERS; CHEMICAL REACTION KINETICS; EXPERIMENTAL DATA; TOLUENE; ALKYLATED AROMATICS; AROMATICS; DATA; EQUIPMENT; HYDROCARBONS; INFORMATION; INORGANIC ION EXCHANGERS; ION EXCHANGE MATERIALS; KINETICS; MATERIALS; MINERALS; NUMERICAL DATA; ORGANIC COMPOUNDS; POLLUTION CONTROL EQUIPMENT; REACTION KINETICS; 090900* - Biomass Fuels- Processing- (1990-); 100200 - Synthetic Fuels- Production- (1990-); 400201 - Chemical & Physicochemical Properties

Citation Formats

Fraenkel, D. Role of external surface sites in shape-selective catalysis over zeolites. United States: N. p., 1990. Web. doi:10.1021/ie00105a012.
Fraenkel, D. Role of external surface sites in shape-selective catalysis over zeolites. United States. doi:10.1021/ie00105a012.
Fraenkel, D. Sat . "Role of external surface sites in shape-selective catalysis over zeolites". United States. doi:10.1021/ie00105a012.
@article{osti_6464532,
title = {Role of external surface sites in shape-selective catalysis over zeolites},
author = {Fraenkel, D.},
abstractNote = {A simple kinetic model is developed having an analytic solution that explains and quantifies isomer shape selectivity in zeolite catalysis. The model, based on the assumption of existence of both shape-selective (e.g., para-selective) internal catalytic sites and nonselective (e.g., non-para-selective) external sites, addresses the preferred overall formation of the isomer that diffuses more rapidly in the intracrystalline space, as well as the decline in shape selectivity with conversion. Exemplified for the production of xylene from toluene over HZSM-5 catalysts, the model gives a very good fit with experimental data of toluene disproportionation. Lack or loss of para selectivity is thus explained as resulting from reactions occurring on the external surface of the zeolite. The model predicts maxima in {ital p}-xylene production, subject to system variables, as a function of reaction time.},
doi = {10.1021/ie00105a012},
journal = {Industrial and Engineering Chemistry Research; (USA)},
issn = {0888-5885},
number = ,
volume = 29:9,
place = {United States},
year = {1990},
month = {9}
}