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The worldwide production of ethylbenzene (EB) and isopropylbenzene (cumene) is estimated (for 2001) as 23 and 8.3 million metric tons, respectively. These chemicals are currently produced by alkylation of benzene with ethene and propene over zeolite catalysts. All existing processes for ethene and propene production operate at very high temperatures (600-1000 C) and consume the huge amount of energy that is required for highly endothermic reactions taking place. In some processes, all necessary energy is generated by direct burning of fuel, and in the others, the energy is also supplied by oxidation of coke formed in the catalysts together with direct burning of fuel. Also, the majority of the existing technologies suffer from poor product alkene selectivities, e.g. in steam cracking of naphtha (main process used in Europe and Japan) the selectivity to ethene and propene is around 25 and 18 wt%, respectively. Hence, it is obvious that the existing technologies of EB and cumene production (via benzene alkylation with the corresponding alkene) are very energy intensive, consume fossil fuels and produce a greenhouse gas, namely C02. Given consideration to the scale of production of these chemicals, one can easily identify serious problems with the existing technology in terms of Green Chemistry and Sustainable Development.This project aims to engineer new catalytic reaction pathways for production of EB and cumene via benzene alkylation with ethane and propane, respectively, thus eliminating the use of the corresponding alkenes and, consequently, the problems (to very large extent) identified above. The underlining idea of our research is to couple alkane dehydrogenation and benzene alkylation with alkenes, and to carry out, study and develop this novel chemistry at relatively low temperatures (250-400 C). At such temperatures the equilibrium dehydrogenation conversions of ethane and propane are lower than 1-2% and it is therefore not surprising that practically no research has been performed under these conditions to date. Our idea is based on understanding that thermodynamic equilibrium is a dynamic (not static) phenomenon, and we suggest to by-pass the thermodynamic limitations by trapping the alkenes (products of dehydrogenation) with benzene. Thus, it is proposed to develop a bifunctional catalyst(s) that will be active, selective and stable in both the dehydrogenation and alkylation reactions. To achieve this goal, we plan to study and optimise the dehydrogenation/alkylation activities of the catalysts, their stability to coke formation, role of reaction/diffusion (activity/pore structure), effects of reaction conditions and feed composition on the catalyst performance.The essential feature of our project is the day-to-day collaboration of a chemist with extensive experience in the mechanisms and kinetics of catalytic heterogeneous reactions and a chemical engineer with extensive expertise in analysis of catalyst pore structure and diffusion processes. In our view, such collaboration is vital for successful development of a potentially commercially viable bifunctional catalyst, since it is essential that catalyst design and optimisation (chemistry input) is integrated with an understanding of mass transport and kinetics (chemical engineering input) from Day 1. This will ensure optimal matching of the rates of the individual steps and enable highest reaction efficiency and selectivity in the proposed combined process. Another, quite different (but also important) benefit is envisaged from the chemist/chemical engineer collaboration in this project, namely accelerated knowledge transfer between two investigators and the Chemistry and Chemical Engineering PhD students, which would be jointly supervised by both investigators.
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