Heterogeneously Catalysed Combustion

A catalyst is a substance that increases the rate at which a chemical system approaches equilibrium, without being consumed in the process. Catalytic materials are classified as being either homogeneous catalysts, if the catalyst and reactants are present in the same phase, or heterogeneous catalysts, if they are not. The industrial applications of heterogeneous catalysts includes energy conversion and the production of hydrocarbon feedstocks, the petroleum industry, the petrochemical industry, the heavy inorganic chemicals industry, the fine chemicals industry and atmospheric pollution control. A well known application of catalytic combustion is that of a catalytic converter, used for exhaust emission control.

In the most general case reaction systems involving a catalytic agent on a solid support and housed in a stirred vessel involve interactions between the homogeneous and heterogeneous reactions. Depending upon the application these may, or may not, be a desirable feature. Thus the modelling of these systems is made on three levels: (i) consideration of the homogeneous reaction alone, (ii) consideration of the solid catalyst alone, and (iii) examination of the behaviour of the reactor and catalyst material together.

My aims/results in catalytic combustion are:

• To examine the competition between adsorption-desorption processes and the catalytic reaction.
• Determine appropriate operating conditions for optimal reactor performance.
• Investigating the effect of passing a current through the catalyst.
• To investigate reversible deactivation of the catalyst by a poison.
• To examine the effect of coupling between homogeneous gas-phase combustion and heterogeneously catalysed (surface-gas) combustion at high temperatures.

These processes are being investigated within the framework of a continuously stirred tank reactor. The resulting spatially-uniform models are then investigated by using the techniques of bifurcation theory, continuation methods and dynamical systems theory.

Highlights of work in heterogeneously catalysed combustion

1. The introduction of a low-dimension model for heterogeneously catalysed combustion in a well-stirred continuously-stirred tank reactor in which adsorption and desorption processes were modelled using the established physical chemistry of these processes Previously only isothermal models had been investigated. (Abstract).
2. Showed the critical importance of the initial conditions in determining the evolution of the system when the inflow concentration is the experimentally varied parameter: reactor efficiency can be dramatically increased, upto a factor of 10³, by fine-tuning the initial conditions. (Abstract).
3. Showed that running a current through a catalyst is equivalent to manipulating the coolant temperature.
4. Showed that the transitions between non-autothermal/autothermal behaviour and autothermal/supercatalytic behaviour can be understood from the response curve as the coolant temperature is varied. The dynamical systems framework then establishes the reactor conditions required to operate either autothermally or supercatalytically.

My collaborators in modelling heterogeneously catalytic combustion

Short article on heterogeneous catalysis

I've written a series of short articles. Each of these provides a short overview of particular topic that I've investigated in my research. There's one article relating to heterogeneous catalysis.