Characterization of shape selectivity catalyst systems

Abstract

The shape selectivity and catalytic properties of organically pillared zirconium phosphates, novel aluminophosphate (AlP12A), AlPO[4]-5 with transition metal oxides, and silicalite with transition metal oxides have been characterized. For organically pillared zirconium phosphates, the BET surface area has been found to increase with the increase in size of the organic groups in the interlayers. [alpha]-Zirconium phosphate pillared by diphenyl has interlayer openings large enough to sorb isopropanol. In contrast, the phenyl and dimethylphenyl pillared zirconium phosphates have less free space for isopropanol, and sorb isopropanol only on the surface. The decomposition of isopropanol occurs within the interlayers for diphenyl but only on the outersurface for the dimethyl and phenyl. The dehydration of isopropanol to propylene has been found to be the primary reaction for all the zirconium phosphate catalysts. For the aluminophosphate series catalysts, AlP12A has pore-window opening about the molecular size of isopropanol. Three different sizes of pore may be in AlP12A. However, it was found that both AlP12A and AlPO[4]-5 were weak acid catalyst. The improvement of catalytic property AlPO[4]-5 was made by preparing transition metal oxides in the crystal. It was found that AlPO[4]-5 with cobalt loading as low as 1.06% has significantly higher activity than AlPO[4]-5 for cracking reaction. From the comparison studies of cobalt oxides, isomorphous substitution in the silicalite framework or impregnated in silicalite, acidic sites with different strength and higher reduction resistance of cobalt oxides by hydrogen on the framework samples have been found. Both series catalysts with cobalt loading less than 1% have strong acidic properties for cracking.