FORMATION OF SURFACE METHOXY GROUPS ON H-ZEOLITES FROM METHANOL - A QUANTUM-CHEMICAL STUDY

Methanol interaction with active sites on H-zeolites was studied by me ans of quantum chemical methods. Ab initio calculations at MP2/6-311+G (d)/6-31G(d,p)/31G level using the model cluster approximation were ma de for different possible conformations of chemisorbed methanol on H-z eolite. All structures were optimized and characterized as stationary points at the HF/3-21G level. Two model clusters with a different numb er of oxygen atoms able to interact with methanol were considered. We found three reaction paths for the interaction of methanol with the ac id zeolite cluster. Our results also suggest that a population of the methoxy-zeolite complex, which has been proposed as an active electrop hile in aromatic alkylations, can exist on SiOSi bridges, and such spe cies are strongly activated for electrophilic attack.