On the role of strength and location of Brønsted acid sites for ethylamine synthesis on mordenite catalysts

Abstract

The elementary steps of alkylation of ammonia with ethanol and the role of the strength and location of the acid sites of the mordenite catalysts were investigated by means of in situ i.r. spectroscopy, temperature-programmed desorption and kinetic measurements. Ethanol and ammonia have access to all Brønsted acid sites of the mordenites investigated. From the products only monoethylamine reached all acid sites, while di- and triethylamine sorbed only on 60% and 45% of the sites, respectively. The Brønsted acid sites of HNa-mordenites are exclusively located in the main channel up to an hydrogen exchange degree of 60%. Only at higher exchange degrees are the sites in the side pockets also exchanged. These latter acid sites apparently contribute significantly to the overall rate of amination. Mordenite with a high concentration of Na + ions (low H + exchange degree) stabilize ammonium less than those with a low Na + concentration. This leads to more ethene produced during the amination reaction. While some diethyl ether is formed during amination, the alcohol and not the ether is the primary alkylating agent.