ACID-BASE BIFUNCTIONAL CATALYSIS IN THE DECOMPOSITION OF ALKYLAMINES

Conversion of primary, secondary and tertiary alkylamines were studied at 673-773 K over three conventional catalysts, SiO2-Al2O3 (SA), MgO, and ZrO2, which were a typical solid acid, a solid base and an acid-base bifunctional catalyst, respectively, and two new types of synthesized acid-base bifunctional catalysts, SiO(x)/MgO and hybrid SA/MgO, which consist of a silanization of MgO and a mechanical mixture of SA and MgO, respectively. The results indicate that acid and base bifunctional properties are necessary for an effective synthesis of nitriles from alkylamines, especially from tertiary and secondary alkylamines, in which the acidic functions mainly contribute to the dealkylation of the latter two amines to their corresponding primary ones while the basic site serves mainly the dehydrogenation of the resultant primary amine to nitrile. A detailed comparison of the behavior of SA/MgO, SiO(x)/MgO and ZrO2 suggests that the relative orientation of the acidic and basic sites greatly affects the product selectivity in the alkylamine conversion.