IR OBSERVATION OF ADSORPTION AND INITIAL REACTIONS OF OLEFINS ON BRONSTED ACID SITES OF A DEUTERATED ZSM-5

Adsorption of linear olefins (C-2-C-4) on a deuterated H-ZSM-5 (D-ZSM- 5) was studied by infrared (IR) spectroscopy. The initial interaction of the olefins with Bronsted acidic OD groups was hydrogen-bonding to form II-complexes at low temperatures. The adsorbed ethene and propene desorbed by heating under evacuation, while various reactions took pl ace for adsorbed I-butene; double bond migration (DBM) to 2-butene bel ow 230 K followed by dimerization at room temperature. An unusual reac tion path was deduced for DBM of I-butene, where proton transfer from Bronsted acid sites (BAS) to the adsorbed I-butene was not essential.