The effects of addition of alumina to the matrices of cracking catalysts containing different types of zeolite Y, on their cracking performance, were investigated using a micro activity test and two different feed oils. For the heavier feed oil, the alumina addition resulted in a higher conversion at the same catalyst to oil ratio independent of the type of zeolite. This higher conversion was accompanied by a greater selectivity for coke and a lower selectivity for gasoline. For the lighter feed oil the effect of alumina addition on the total conversion was much less pronounced while the effects on the selectivity were similar to those observed using the heavier feed. The performance of the catalysts in a commercial fluid catalytic cracking unit is discussed in view of their coke forming tendencies and the heat balance of the cracker.
The effects, on the activity and selectivity for cracking heavy oils, of varying the alumina-silica ratio in amorphous aluminosilicate matrices for CREY, REUSY, USY, and LZ zeolites were studied using a microactivity test and two different feedstocks. With a heavy aromatic feedstock gasoline yields and octane numbers showed a pronounced maximum for matrix alumina-silica weight ratios in the range 90:10-70:30 and with CREY zeolite as the main active component. With a lighter aliphatic feedstock the gasoline yields and octane numbers were much less dependent on the alumina-silica weight ratio. The effects on pore structure and selectivity of hydrothermal treatment of conventional amorphous aluminosilicate catalysts and zeolite catalysts with amorphous silica-alumina matrices having alumina-silica weight ratios in the range 90:10-70:30 are discussed.
Three types of alumina-montmorillonite complexes were evaluated as cracking catalysts, alone and in admixture with rare earth exchanged zeolite Y (REY), using the micro activity test and three different feed oils. Prior to the test, all catalysts were steam treated at 750°C for 18 h. For cracking of heavy oils, the alumina-montmorillonites showed conversions similar to that of a reference catalyst containing 20% REY in a kaolin-binder matrix. The alumina-montmorillonites showed higher coke and lower gas yield when compared with the reference catalyst while the gasoline yields were essentially the same over the two types of catalysts. The selectivity for light cycle oil was considerably greater for the alumina-montmorillonites. When used as matrices for REY, the alumina-montmorillonites resulted in considerably more active catalysts at the same zeolite content compared with a catalyst having a kaolin-binder matrix, while the selectivity properties differed very little between the two types of catalysts.
Changes in pore structure on thermal and hydrothermal treatment of three different alumina-montmorillonite complexes were investigated using nitrogen adsorption-desorption measurements, thermogravimetric analysis, adsorption of condensed aromatic molecules and acidity measurements by pyridine adsorption. The surface area retention of the alumina-montmorillonites after thermal and hydrothermal treatment increased with increasing temperature of hydrothermal treatment of the aluminum chlorohydrate solution used in the preparation of the materials. Hydrothermal treatment of the alumina-montmorillonites at 750°C for 18 h resulted in increased average layer distances in the materials primarily due to a collapse of micropores. The acidity retentions of the alumina-montmorillonites, measured by pyridine adsorption, were approximately proportional to the corresponding surface area retentions.