Bifunctional catalysis Application in valorisation of light alkanes and in Fine Chemicals

Article [J 1 217] demonstrates the essential role played by bifunctional redox-acid catalysis in the major conversion processes of petroleum refining and petrochemicals. The catalysts used have two types of active site:

• hydrodehydrogenating sites originating either from noble metals Pt or Pd, or from mixed sulphides of metals from groups 6 (Mo or W) and 8 (Co, Ni);

• protonic acid sites from inorganic oxides: chlorinated aluminas, acid zeolites and silica aluminas.

Reaction schemes for bifunctional hydrocarbon transformations involve multiple successive steps of catalysis at hydrodehydrogenating and protonic sites, and transport of reactant molecules, products and reaction intermediates. Despite this complexity, these transformations occur very rapidly and in an apparent single step, with the thermodynamically disadvantaged unsaturated intermediates appearing only in trace form in the final products. In addition, process optimization (catalyst and operating conditions) makes it possible to direct selectivity towards the desired products, while limiting catalyst deactivation.

These assets can be, and already are, partially valorized in the upgrading of light alkanes C ₁ -C ₄ and in the organic synthesis of high value-added products (Fine Chemicals). This article [J1 218] reviews the advances made in these fields, the choice to deal with them in a specific article being linked to the significant limitations imposed in the development of industrial processes by the peculiarities of most of the desired transformations.

– The first, which applies equally to the upgrading of light alkanes and to Fine Chemicals, is that the bond-cutting reactions that predominate in oil refining and petrochemical processes are naturally supplanted by condensation reactions.

– The second, specific to Fine Chemicals, is the very high reactivity of reagent molecules, intermediates and products (whether desired or not) conferred by the functional groups they contain.