Textural properties, surface chemistry and cyclohexene conversion of AlPO4-Al2O3 catalysts (original) (raw)

The effects of surface dehydration on crystallinity, textural properties (surface area and pore volume) and surface acid-base properties of differently prepared AlP04-Al203 (75:25 wt%) systems have been studied. Physical characterization was carried out by N2 adsorption, TG and XRD ~asureaents and by infrared spectroscopy. The catalysts were characterized by surface acid-basic site concentrations using a spectrophotometric method and by their catalytic activities in cyclohexene skeletal isomerization (CSI) through the use of a microcatalytic pulse reactor. Al203 was found to increase both the surface area and pore volume of A1P04 through the inhibition of the A1P04 crystallization at 1073 K. Apparent rate constants and activation energies in CSI were obtained according to the kinetic model of Bassett-Habgood developed for first order processes. Selectivity studies lead to the conclusion that I-and 3-methylcyclopentenes are competitive stable primary reaction products coming from cyclohexene across a parallel reaction network. The addition of Al203 to AlP04 catalysts enhances considerably both the catalytic activity to 1-, 3-and 4-~thylcy~lopentenes (I-, 3-and 4-HCP) and the selectivity to l-MCP (u) in these systems for the CSI indicating an increased strong acidity.