New technology for production of spherical alumina supports for fluidized bed combustion

Fluidized bed catalytic combustion has proved to be very promising for industrial application. The milestone problem is the development of support and catalyst with a high mechanical and thermal stability. We have developed a new technology for production of alumina supports with desired spherical shape, texture and structure. In this paper several pathways to produce aluminum hydroxide of a pseudoboehmite structure including conventional and new technologies are discussed. Properties of spherical granules depend on the method of granulation and most attention has been paid to development and optimization of hydrocarbon-ammonia molding to produce uniform alumina spheres. Several methods to estimate mechanical strength of spherical aluminas are applied to evaluate mechanical durability of prepared catalysts in a fluidized bed. Optimization of high quality spheres production focused on study of the effect of initial hydroxide properties and molding conditions on properties of the final product. Modification of spherical alumina with oxides of Mg, Ce, La and Si proved to be effective to substantially improve the mechanical and thermal stability. This effect is most pronounced when pairs of these dopes are introduced simultaneously. (C) 1999 Elsevier Science B.V. All rights reserved.