Date of Award

2009

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

First Advisor

Dr. Abbas Khalecl

Second Advisor

Dr. Sofian Kanan

Third Advisor

Dr. Ali AI-Marzouqi

Abstract

Heterogeneous catalysts which are mainly based on metal particles and metal oxides have shown promising activity and selectivity in several environmental and industrial important reactions. Catalysis plays a key role in chemical and material manufacturing, fuel cells as well as other energy conversion and pollution control systems. Petroleum and fuel industry, in particular, rely largely on heterogeneous catalysis. Since catalysts play such a critical role in essential processes, the search for more effective and selective catalysts continues to be of great importance for both environmental and commercial considerations. The current study focuses on the catalytic conversion of methanol to other fuel alternatives and valuable chemicals, especially dimethyl ether (DME) which has attracted the attention of several companies and researchers due to its potential use as an environmentally clean fuel.

Several metal oxide catalysts were investigated in this study including chromium(III) oxide, iron (III)oxide, titanium oxide, aluminum oxide, and several composites based on these oxides. The selection of these systems was based on their known activity in acid-base as well as oxidation-reduction surface reactions. The first part of this work involves various studies aimed at developing cost-effective methods to prepare nano-structured chromium(III) oxide-based catalysts. Pure chromium oxide and chromium oxide-containing catalysts have been prepared by sol gel and forced precipitation methods. These are appropriate preparative methods for the synthesis of ultra-fine oxide materials at relatively low temperatures and reasonable cost. The effect of chromium on the composition and textural properties was characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), FTIR spectroscopy, and N2 adsorption.

In the second part of this work, the activity and selectivity of these catalysts in methanol conversion to dimethyl ether (DME) and other valuable chemicals was investigated. This study involved all chromium mixed oxides as well as prepared and commercial corresponding pure oxides. Comparison between the catalysts and correlation between the catalysts' activity and the composition as well as textural characteristics were established.

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