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Date of Award

2-1974

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

Supervisor

Dr. T. W. Hoffman

Abstract

The objective of this research program was to evaluate a gas-solid contacting reactor (called a transported bed reactor) in which the solid catalyst is conveyed upward in a vertical pipe by the gaseous reactants/products; at the top of the reactor the solids are separated from the gas stream and recirculated through the system. The reaction employed in this evaluation was the oxidation of orthoxylene on a vanadia on silica gel catalyst.

This oxidation reaction was studied separately on the same catalyst in a bench-scale fixed bed reactor over a range of temperatures, oxygen and orthoxylene concentrations and flow rates to provide conversions from 1 to 100% and considerable variation in selectivity. Reaction products were analyzed at short on-stream times and after considerable reaction times. These results indicated that reaction rates on freshly oxidized catalyst are much higher than those observed after steady-state has been achieved; selectivity to organic oxidation products is also improved significantly. Reaction studies are also carried out with other catalysts, notably a titania based one, and these results are similar in general behaviour but differ in some important details. Kinetic parameters in the Redox or steady-state adsorption models are evaluated.

This reaction was carried out in a pilot scale transported bed reactor, 3/4 in. O.D. by 27 ft. long. Solid hold-up was measured by activating quick shut-off values. It was demonstrated that stable operation could be achieved at very high solids loadings (solid/gas ratios up to 250 and voidages from 0.60 to 0.86). It is demonstrated that the high reaction rates and selectivities can be exploited in such reactors. Suggestions for further research on such reactor systems are included.

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