Aluminum oxide tubes and process for their manufacture

Abstract

A process is described for the manufacture of a gas-tight aluminum oxide tube which is suitable for performing catalytic high-temperature reactions. For this purpose water, a binder and a plasticizer are added to aluminum oxide powder, the mixture is extruded to give a tubular green body and the tube is dense-sintered at about 1740.degree. C. An aqueous suspension of aluminum oxide is obtained by grinding aluminum oxide, and a spray powder of a maximum particle size of 200 .mu.m is prepared therefrom. Presintering takes place at a temperature T between 1300.degree. and 1400.degree. C. and grinding takes place with water and a water-soluble stabilizing agent. The aqueous suspension is sprayed and the resultant spray powder is treated with water and a plasticizer, the mixture is kneaded to give a plastic mass and this mass is extruded to give a tubular green body which is also presintered at the temperature T. The presintered tube is then immersed in water, briefly dried and the mixture consisting of water/stabilizing agent/spray powder is applied to the interior of the tube. The remainder is poured off, and the internally coated tube is dried and finally dense-sintered at about 1740.degree. C. A tube results with an Al.sub.2 O.sub.3 content of greater than 98%. The roughness of the coating on the interior is 2-10 .mu.m.