n-Butane isomerization over H-mordenite: role of the monomolecular mechanism Original Research Article

Isomerization of n-butane over several H-mordenite and Pd/H-mordenite samples with different Si/Al ratios is studied. 1,1,1,3,3,3-Hexamethyldisilazane was injected to obtain catalysts with poisoned external Brönsted acid sites. In the absence of metal, isomerization activity was virtually suppressed for the poisoned non-dealuminated mordenite catalysts. However, dealuminated samples were more resistant to the poisoning, and showed a higher selectivity to isobutane. For these samples, the reaction order with respect to n-butane was close to 1 for isobutane and close to 2 for pentanes, and turnover frequency (TOF) was not dependent on acid site density. No significant behaviour changes were observed for samples modified with Pd. It is proposed that isomerization of n-butane over the dealuminated samples can take place via monomolecular mechanism.