Journal of Molecular Structure, 239 (1990) 185-192 Elsevier Science Publishers B.V., Amsterdam 185 zyxwvutsrqp SURFACE INTERMEDIATES IN THE TRANSFORMATION OF ALLYL ALCOHOL OVER ZEOLITES I. KIRICSI and GY. TASI Applied Chemistry Department, Jozsef Attila University, H- 6720 Szeged, Rerrich B. t. 1 (Hungary ) A. MOLNAR O rganic Chemistry Department, Jozsef Attila University, H- 6720 Szeged, Dom t. 8 (Hungary) H. FijRSTER Institute of Physical Chemistry, University of Hamburg, Bundesstrafie 45, D-2000 Hamburg 13 (Federal Republic of Germany) (Received 2 January 1990) ABSTRACT Interaction of ally1 alcohol, acrolein and allene with zeolite HZSM-5 results in the formation of alkenyl carbenium ion oligomers as intermediates. According to the molecular electrostatic poten- tial map and to the partial atomic charges from MNDO calculations as the preliminary step, the oxygen atom of ally1 alcohol is attacked by the proton, followed by dehydration to allene, undergo- ing further transformation. INTRODUCTION Adsorption and reaction of alcohols over acidic zeolites have been investi- gated and reviewed by a number of authors [ 11. Oxonium ions and carboca- tions were assumed to be the surface intermediates in dehydration and in the further reactions of the primary products. In the formation of these ions, Brijnsted acid centres of the zeolites are involved. The main products identi- fied were water, the corresponding ethers and olefins. The formation of alde- hydes and ketones depended on the concentration of basic sites such as Na+, K+ and Cs+ ions [2]. It was also shown that under suitable conditions stoi- chiometric adsorption complexes were formed upon adsorption of various al- cohols on zeolite HZSM-5 of different Si/Al ratios [ 31. Infra-red (IR), Ther- mal Programmed Desorption-Mass Spectrometry (TPD-MS) and Thermogrammetric Analysis-Mass Spectrometry (TGA-MS) studies re- vealed that both the formation and the desorption of water and the correspond- ing olefin took place simultaneously. Investigating the adsorption of 2-pro- panol on H,Na-mordenites by ultraviolet-visible (UV-VIS) spectroscopy, zyxwvutsrqpon 0022-2860/90/$03.50 0 1990 - Elsevier Science Publishers B.V.