SHAPE-SELECTIVE METHYLAMINE SYNTHESIS OVER SMALL-PORE ZEOLITE CATALYSTS

Methylamine syntheses from methanol and ammonia on various zeolite cat alysts have been studied over a temperature range of 573-673 K. The H- chabazite catalyst gives enhanced yield of monomethylamine at higher p artial pressures of ammonia, while the formation of trimethylamine and dimethyl ether has been extremely retarded, Sorption-desorption exper iments reveal nearly complete exclusion of TMA from the chabazite cage s. Sorption and IR spectroscopic data provide evidence that the initia l methylamine formation involves methanol and ammonia that are both bo und to Bronsted acid sites and follows a Langmuir-Hinshelwood mechanis m, in contrast to the Eley-Rideal mechanism that is observed with larg e pore zeolites or other solid catalysts. Transition state selectivity , rather than product selectivity, is invoked as the main cause for th e preponderance of monomethylamine and dimethylamine and the almost co mplete suppression of trimethylamine. (C) 1996 Academic Press, Inc.