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

Journal Article · Sat Sep 01 04:00:00 EDT 1990 · Industrial and Engineering Chemistry Research; (USA)

DOI:https://doi.org/10.1021/ie00105a012· OSTI ID:6464532

Fraenkel, D ^[1]

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1. Pittsburgh Univ., PA (USA). Dept. of Chemical and Petroleum Engineering

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.

• OSTI ID: 6464532
• Journal Information: Industrial and Engineering Chemistry Research; (USA), Journal Name: Industrial and Engineering Chemistry Research; (USA) Vol. 29:9; ISSN 0888-5885; ISSN IECRE
• Country of Publication: United States
• Language: English

Related Subjects

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ALKYLATED AROMATICS
AROMATICS
CATALYTIC CONVERTERS
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
DATA
EQUIPMENT
EXPERIMENTAL DATA
HYDROCARBONS
INFORMATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
KINETICS
MATERIALS
MINERALS
NUMERICAL DATA
ORGANIC COMPOUNDS
POLLUTION CONTROL EQUIPMENT
PRODUCTION
REACTION KINETICS
TOLUENE
XYLENES
ZEOLITES