Composite catalysts involving acidic or basic zeolites and gamma-aluminum oxide or silicon dioxide-aluminum oxide and their application to cracking and reforming. (Volumes I and II).

摘要

The performance of catalysts involving zeolite composite catalysts on catalytic cracking and reforming is examined experimentally and theoretically. Several synergistic reactions and phenomena resulting from the coexistence of the various catalytic features of the different zeolites, and the two functions of the bifunctional zeolites employed, were discovered.; A comparison of the model of composite pellets made of zeolite crystals uniformly imbedded in an amorphous matrix with composite pellets of ZSM-5/{dollar}SiOsb2-Alsb2Osb3{dollar} for the cracking of n-hexane was tried. It was found that the present model describes fairly well the performance of composite catalytic particles. From the present analysis it was shown that the diffusion through the zeolite particles can be rate limiting under certain conditions. The application of the present model for the cracking of gas-oil gives satisfactory results in comparison with industrial moving bed reactors.; The performance of ZSM-5 and {dollar}beta{dollar} zeolite as possible additives to Y and USY fauja-sites for cracking reactions was examined. It was shown that the product selectivities are a strong function of the conversion level which alters significantly the extent of the various reactions that occur. The additivity rule for the prediction of the product selectivities over the composites from the individual catalysts is not always followed.; Zeolite {dollar}beta{dollar} supported Pt was proved to be more efficient reforming catalyst than the traditionally employed Pt/{dollar}gamma{dollar}-{dollar}Alsb2Osb3{dollar}. The former catalyst exhibits relatively high dehydroisomerization capabilities which lead to aromatics with methylcyclopentane. In addition, bimolecular alkylation reactions favored by the Bronsted acidity of the zeolite lead to aromatics with a carbon atoms number different than that of the feed hydrocarbon. It was found that Pt/{dollar}gamma{dollar}-{dollar}Alsb2Osb3{dollar} enhances dehydrogenation reactions. The balancing of the Bronsted acidity with the Pt loading via composites of Pt/{dollar}beta{dollar} zeolite with Pt/{dollar}gamma{dollar}-{dollar}Alsb2Osb3{dollar} can lead to the maximization of the dehydroisomerization of alkylcyclopentanes. The product selectivities are not influenced by the diffusional resistances that the composite pellets impose. Dealuminated {dollar}beta{dollar} zeolite at moderate hydrogen pressures minimizes significantly the coke generated over the Bronsted acid sites keeping simultaneously the rates of hydrocracking at very low levels. As a result, Pt/{dollar}beta{dollar} zeolite with a {dollar}SiOsb2/Alsb2Osb3{dollar} molar ratio and a Pt loading of 0.5 wt % at 100 psig exhibits high aromatic selectivities and unchanged activity after many hours of operation. This behavior for the reforming of naphthenic feeds results from the optimum synergism achieved between the Pt sites and its moderate Bronsted acidity.; A new type of synergism was discovered for the reforming of mixtures of paraffins over Pt/{dollar}beta{dollar}-Pt/L and Pt/USY-Pt/L composites. It was found that the aromatic selectivities of the mixtures over these composites are higher than those calculated from the behavior of individual hydrocarbons under identical conditions. This behavior was attributed to the synergistic colaboration between the components of the feed mixtures and the catalytic components of the composites.