The control of the pore volume and pore size distribution in alumina and silica gels by the addition of water soluble organic polymers

Abstract

A method is described for preparing alumina and silica gels containing a controlled and enlarged pore volume distribution by the addition of water soluble organic polymers. Mixtures of hydrous gel and polymer were prepared in two ways: by precipitating the gel from solutions containing the dissolved organic matter; and by dispersing the polymer in the hydrous gel after the precipitation step. The organic matter was carried through the drying process until the structure set then calcined out of the system. It was found that polymers such as (a) the polyethylene glycols and polyethylene oxides bring about a large increase in the pore volume in the pore size range 1000 to 20 Å radius, (b) the methyl cellulose compounds form mainly large pores, and (c) polymers such as the polyvinyl alcohols and the polyacrylamides increase the pore volume across the entire pore size range 10 5 to 20 Å radius. The pore volume distribution, surface area, and apparent bulk density data are given for typical gels made with each type of polymer. The volume distribution measurements were made by the method of mercury penetration and the surface areas measured by the nitrogen adsorption technique.