Preparation of extruded alumina with suitable crushing strength and good stability

Abstract

The extruded alumina was prepared via extrusion of a paste which contains boehmie, δ-alumina, polyethylene glycol 400 as an additive and nitric acid as a peptizing agent. Porosity and crushing strength of the samples were carried out by means of N2 adsorption-desorption isotherm and mechanical strength instrument respectively. The calcined extruded alumina has the specific surface area of 168-240 m2/g, pore volume 0.37-0.5 cm3/g and pore diameter 8.2-8.8 nm. More than 36% of pore volume belonged to the pore diameters larger than 10 nm. The lateral crushing strength was found to be 232-476 N/cm2. The highest crushing strength of prepared samples was 30% higher than those reported in the literature. Addition of aluminum nitrate to the paste increased 50%in the lateral crushing strengthso it reached the value of622 N/cm2. This was mainly due to the binder functionality of aluminum nitrate which led to stronger connections between the particles. The extruded alumina did not show any deformation when introduce to the impregnation solution. This extruded alumina can be used as the catalyst support.