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RESEARCH PRODUCT

The Relevance of Kneading and Extrusion Parameters in the Manufacture of Active Porous Aluminas from Pseudoboehmites

subject

description

In order to study the effect-on crushing strength, attrition resistance, specific pore volume, and pore volume distribution of extrudates-of kneading and extrusion parameters in the manufacture of active porous aluminas, a commercial pseudoboehmite (Pural SB from Condea Chemie, Brunsbuttel, FRG) was employed. A minimum kneading torque was required to prepare an extrudable paste, predetermined by extrusion conditions. The torque had an upper limit with respect to certain extrudate properties. The amount of water and the concentration of nitric acid as binder solutions were found to have a decisive bearing on the mechanical properties and the distribution of the pore volume. Crushing strength and attrition resistance were primarily controlled by the amount and distribution of mocropores. (change-para-here) On increasing the speed of revolution of the kneader, the necessary kneading time was reduced. Extrudates with smooth surfaces were obtained at a low speed of the extruder screw and employing dies with a bore diameter of one third of their length.