Sol-gel preparation of nanostructured adsorbents

This paper reports sol-gel synthesis and properties of several major cerami c adsorbents. Nanostructured gamma-alumina, zirconia and titania adsorbents with uniform pore size distribution and an average pore diameter of about 3 nm are prepared by hydrolysis and condensation of corresponding metalorga nic precursors. The as-synthesized adsorbents are in their meta-stable phas es, and transform to their stable phases upon heat-treatment. The phase tra nsformation accompanies a decrease in surface area and increase in pore siz e. Microporous (< 2 nm) silica adsorbents are prepared by the sol-gel metho d following a polymeric sol route. Doping alumina in silica adsorbents impr oves their thermal and hydrothermal stability. A sol-gel granulation proces s based on the oil-drop principle is described for preparation of gamma-alu mina granular particles. A solution-sol mixing coating method is used to co at active species on the pore surface of the granular gamma-alumina particl es. The sol-gel derived granular adsorbents exhibit high crush strength, go od attrition resistance and desired pore structure. Experimental results sh ow that the sol-gel derived CuO/gamma-alumina and CuCl/gamma-alumina granul ar adsorbents have better properties for sorption of SO2 and ethylene than similar adsorbents prepared by the conventional methods.