Determination of the prevailing n-butenes dimerization mechanism over nickel containing Al-MCM-41/ZSM-5 mixed-phase catalysts

Nickel modified mixed-phase catalysts containing both mesoporous Al-MCM-41 and microporous ZSM-5 phases were synthesized via a one-pot synthesis. By varying the composition of the catalysts, optimum values regarding Si/Al ratio and nickel content for a highly selective dimerization of n-butenes were identified. An interaction of nickel sites with vicinal aluminum or acid sites can be assumed, since a correlation between Ni/(Al + Ni) ratio, catalytic activity and selectivity was found. Novel approaches to evaluate the contribution of the cationic or coordinative reaction mechanism to the overall reaction course are proposed.