An improved catalytic cracking of n-hexane via methanol coupling reaction over HZSM-5 zeolite catalysts

The coupling transformation of n-hexane and methanol over HZSM-5 has been investigated with a pulse-reaction system. In the temperature range of 400-500 degrees C, kinetic data was collected and reaction order was determined. Compared with the pure n-hexane cracking, the increased rate constant and the lowered apparent activation energy clearly demonstrate an improvement of n-hexane activation using methanol as co-reactant and an increased contribution of faster bimolecular mechanism to the n-hexane transformation due to methanol introduction. Similarly, the results of coupling transformation performed over HZSM-5 with different Al content further confirm the transition between reaction mechanisms of n-hexane on account of the introduction of methanol. Moreover, the further investigation suggests that the enhancement of n-hexane activation and the change of reaction mechanism are attributed to the presence of intermediate species evolved from methanol. Thus, a proposed reaction pathway of n-hexane activation with methanol as co-reactant was put forward.