Gas-solid chromatographic studies of two well-known catalysts

Mason, Robert Peter

Gas-solid chromatographic studies of two well-known catalysts

Master Thesis

1983

Publisher

University of Cape Town

Department

Department of Chemistry

Faculty

Faculty of Science

Abstract

This work was initiated to explore the scope and feasibility of using a gas chromatograph to study catalytic reactions. Various methods have been proposed in the literature and it was decided to investigate various possible systems. Two catalysts were chosen for study. The dehydration of alcohols over alumina catalysts has been extensively studied and found to be ideally suited to studies by gas chromatography. The effect of modification of the catalyst by inorganic ions and by water was investigated. The dehydration of ethanol and pentanol were studied. Results indicated that alumina has two types of active sites responsible for the dehydration of alcohols. Zeolite catalysts are well-known and in this work the catalytic cracking of alkanes over zeolite Y was studied. The reaction mechanism was found to be complex and catalyst deactivation due to build-up of highly carbonaceous deposits occurred. All components of the reaction products were produced at similar rates to the overall reaction rate indicating that desorption of alkane product species was not the rate determining step. Between 150° and 300°C propane was the smallest product formed. Only alkanes were found in the product spectrum which was temperature dependent. Addition of hydrogen gas greatly increased the amount of detectable products. Heptane was found to react significantly above 200 °C, hexane about above 225°C and pentane above 250°C. Hexane and cyclohexane reacted at similar temperatures.

Description

Bibliography:pages 116-120.

Keywords

Chemistry

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