CO2 POISONING EFFECT ON HY ZEOLITE DEHYDRATION CATALYST

The poisoning effect of CO2 on a HY catalyst for the dehydration of 2- (2-hydroxyethyl)-pyridine (HEP) to 2-vinylpyridine (VP) has been inves tigated by FT-IR analysis in the presence and absence of pyridine. CO2 was found to adsorb on sites not occupied by pyridine, i.e. on weak b asic sites accompanying the strongly acidic sites, characteristic of Y zeolites in the protonated form. When the basic sites are occupied by preadsorbed CO2, HEP dehydration cannot take place any more through t he minor mechanism, involving a couple of acid-base sites, and the rea ction proceeds only through the major mechanism, involving a carbocati on intermediate, on Bronsted acid sites only.