THE EFFECT OF PROPANE ACTIVATION OVER GA-MODIFIED H-ZS M-5 CATALYSTS

In situ C-13 MAS NMR was used to investigate the influence of total an d partial pressure of propane on the initial stages of its conversion over a Ga/H-MFI catalyst (2-C-13). Propane was the labelled reactant. Different pressures were achieved by varying the amounts of propane an d of nitrogen as diluent in the cell. The nature of primary and second ary labelled reaction products depends on total pressure. High total a nd partial pressures of propane enhance bimolecular primary formation of n-butane and isobutane via a BREST (Bifunctional Reaction Step) mec hanism(1). Low total pressure leads to methane and polymeric fragments as primary products. A reaction pathway including the formation of a polymeric hydrocarbon-chain intermediate is proposed to account for se condary isobutane formation at low pressure. The influence of pressure on reaction equilibria and kinetics and on adsorption and exchange pr ocesses is discussed.