ACIDITY AND SURFACE BEHAVIOR OF ALUMINA-BORIA CATALYSTS STUDIED BY ADSORPTION MICROCALORIMETRY OF PROBE MOLECULES

Acidity and basicity of alumina-boria catalysts supported on porous or non-porous alumina have been studied by adsorption microcalorimetry o f probe molecules (ammonia, pyridine and sulphur dioxide). Despite dec reasing in initial heats, the total acidity as determined by ammonia a dsorption increased in number and strength as a function of percentage of boron oxide. Ammonia, as a strong base, was shown to cover all typ es sites from strong to weak acid sites. Pyridine, as a weaker probe, was shown to dose only the stronger sites of the samples which stay ne arly constant after B2O3 coverage approaching the monolayer. The basic sites of the amphoteric alumina support are neutralized by 10 wt% of boron oxide on non-porous alumina and 20 Wt% Of B2O3 On porous alumina . The catalytic activity for partial oxidation of ethane increased wit h acidity and reached a maximum constant value above 20 wt% of boron o xide.