ON THE INTERACTION OF 1-PROPANAMINE WITH CATION-CONTAINING MFI ZEOLITE

The interaction of 1-propanamine (1-PA) with H-MFI zeolite and its Ga, In, and Cu modifications, prepared by solid state ion exchange, has been studied by thermal analysis, high resolution gas chromatography, mass spectrometry, and catalytic reactor experiments. Two completely different desorption features have been observed when the H-MFI sample is first equilibrated with I-PA at 323 and 593 K and then heated to 823 K. These desorption features have been ascribed to the decomposition of propylammonium and dipropylammonium ions adsorbed at the proton sites of the zeolite. Catalytic experiments confirmed dipropylamine as the major product of 1-PA conversion at 593 K over an H-MFI catalyst. In contrast, a radical change in the interaction of 1-PA with the zeolite has been observed as a result of the replacement of the protons in MFI with Ga, In, or Cu cations. More than one I-PA molecule can be coordinated to a cation even at relatively high temperatures, facilitating both bimolecular transalkylation and dehydrogenation processes. The desorption features of 1-PA with cation containing MFI differ generally from those of pure H-MFI zeolite. NH3 product is desorbed at temperatures as much as 160 K below that of H-MFI. Nitriles, C2-C6 hydrocarbons, and some aromatics appear in appeciable amounts in the decomposition products. Gas-phase hydrogen inhibits the dehydrogenation processes and prevents the formation of a residue. Catalytic experiments in a gradientless batch recirculating reactor have revealed that different dehydrogenation reactions predominate depending on the nature of the zeolite cation. While a C6-imine appears as a major product of the reaction of 1-PA over In-MFI, more dehydrogenated N-containing compounds such as propionitrile and a C6-nitrile predominate over Ga-MFI and Cu-MFI, respectively. These differences can be interpreted in terms of the differing Lewis acid strengths and reducibilities of the Ga, In, and Cu cations. (C) 1994 Academic Press, Inc.