CONICET | Buscador de Institutos y Recursos Humanos

The catalytic cracking of hydrocarbons (FCC) develops new trends in response to increasing demands to process heavier crudes and residual feedstocks, to control contaminants in products and emissions, and to maximize the yields of petrochemical materials. Consequently, the formulation of FCC catalysts is shifting to high accessibility, resid or bottoms upgrading catalysts with active matrices. Active matrices are either silica-aluminas or aluminas. Within the growing interest in mesoporous materials with controlled morphology, with pore sizes between 20 and 200 Å, one of the approaches is the production of composites between inorganic networks, such as silica, and organic polymers. The removal of the organic component by calcination these composites develops porosity. Mesoporous silica-aluminas were synthesised with standard aluminium and silicon sources by means of inorganic organic composites with the addition of chitosan biopolymer, and compared to conventional analogous catalysts. Some catalysts were subjected to hydrothermal treatment. The surface areas were from 480 to 573 m2/g in the untreated samples and 300 to 430 m2/g in the hydrotreated catalysts, average pore sizes ranging from 32 to 100 Å with sharp, unimodal distributions. The chitosan materials showed higher surface areas and larger pore sizes than those of their non chitosan counterparts. The most important differences in the acidic properties were in the relationships between tetrahedral and octahedral aluminium atoms, the chitosan materials having higher relative amounts of tetrahedral aluminium than the conventional silica-aluminas. Evidences of stabilization in the physical and chemical properties were observed in the chitosan-containing catalysts. The catalytic performance was evaluated with tri-isopropylbenzene at 400 ºC, to assess activity and accessibility, and cyclohexene at 300 ºC, to assess hydrogen transfer properties. The highest activity and accessibility was observed in the hydrotreated, chitosan-containing catalyst, while hydrogen transfer capabilities were similar to those of medium unit cell sizes, equilibrium commercial FCC catalysts.