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Abstract

Quantitative experiments on the oxidation of propene to acrolein and carbon oxides over pelleted tin-antimony oxide (Part I) and bismuth molybdate catalysts (Part II) and iso-butene to methacrolein and carbon oxides (Part III) over a bismuth molybdate catalyst were carried out using a well stirred reactor. The oxidation of both gases over copper oxide and cobalt molybdate catalysts was also investigated.

In the three main parts experimental data was fitted to a variety of models based on Langmuir isotherms using a non-linear least squares fitting procedure. The ratios of fitting to experimental variances were used to choose preferred models for each of the main reactions and the formation of carbon oxides in Parts II and III.

In Part I the preferred model assumes two types of active sites, those with affinity for propene only and those with affinity for oxygen only. The model also assumes oxygen adsorption on pairs of adjacent sites. Surface coverage with oxygen varied with both temperature and age. No mass transfer effects could be detected.

In Part II the preferred model for the main reaction assumes propene to be adsorbed on a single active site with a correction term for the effect of the surface reaction on the propene adsorption/desorption equilibrium. No oxygen term was necessary. The carbon oxides model assumes all oxides are formed by the degradation of acrolein, the first step in the process being rate determining. Acrolein is assumed to be adsorbed on pairs of adjacent sites, again with a correction term similar to the main reaction except that it is the acrolein adsorption/desorption equilibria. Apparent activation energies for both reactions were calculated and found to be similar. No mass transfer or reactor geometry effects.

In Part III the main reaction was found to be independent of fuel concentration. Oxygen was assumed to be adsorbed on pairs of adjacent active sites and again a correction term for the effects of surface reaction was necessary. The carbon oxide model was similar to Part II. Methacrolein was assumed to be adsorbed on pairs of adjacent active sites (allowance being made for initial methacrolein formed) with a correction term for surface reaction.

An apparent activation energy for the carbon oxide formation reaction was calculated and found to be similar to that in Part II. No mass transfer effects observed.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science Q Science > QD Chemistry T Technology > TP Chemical technology
Departments:	School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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