Catalytic performance of silica-aluminas synthesised with the help of chitosan biopolymer

MARISA FALCO; JAIME RETUERT; ALEXIS HIDROBO; CRISTIAN COVARRUBIAS; PAULO ARAYA; ULISES SEDRAN

APPLIED CATALYSIS A-GENERAL

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2009 vol. 366 p. 269 - 274

0926-860X

Mesoporous amorphous silica-aluminas were synthesised with standard aluminium and silicon sources by means of the formation of inorganic–organic composites with the addition of chitosan biopolymer, and compared to analogous catalysts synthesised conventionally. Some catalysts were subjected to hydrothermal treatment. The resulting specific surface areas were from 480 to 573 m2/g in the untreated samples and 300–430 m2/g in the hydrotreated catalysts, average pore sizes ranging from 32 to 100A˚ with sharp, unimodal distributions. The chitosan materials showed higher specific 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 the conversion of triisopropylbenzene at 400 8C, to  assess activity and accessibility, and cyclohexene at 300 8C, 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 unitcell sizes, equilibrium commercial FCC catalysts.