ROLE OF SURFACE ACIDIC CENTERS IN EXTENSIVE OXIDATION OF 1-BUTENE OVER MOLYBDENUM OXIDE-BASED CATALYSTS

In order to study the role of surface acidic properties on isomerization and extensive oxidation reactions, the catalytic behavior of a large series of poorly selective molybdates and selective tellurium-doped molybdates in the oxidation of 1-butene was investigated at different reaction temperatures. This study was carried out both in the presence and absence of steam in the feed. Strong analogies within the series of the investigated catalysts were observed: (i) The more active a catalyst is in the isomerization at low temperature (usually 330 °C), the higher the amounts of carbon oxides it produces at high temperature (usually 390 °C); (ii) the decrease with temperature of the isomers yield is related to the corresponding increase of the carbon oxides yield within the class of both selective and poorly selective catalysts; and (iii) the addition of steam increases the isomers yield and decreases the yield of carbon oxides. Again the two changes are related within the class of both selective and poorly selective catalysts. It is assumed that these effects come about by the transformation of the Brönsted sites (responsible for low temperature isomerization) into Lewis sites at high temperature (responsible for the formation of carbon oxides). It is proposed that the extensive oxidation to CO and CO2 involves an interaction between an acidic center, an activated hydrocarbon molecule, and oxygen. It is advanced that the difference in the catalytic behavior between poorly selective and selective catalysts is due to the fact that the Brönsted sites are destroyed by the addition of tellurium. © 1978 Academic Press, Inc. All rights of reproduction in any form reserved.