The Form of Sulfate in Pseudo-Boehmite and Its Effect on Properties of Pseudo-Boehmite

A series of pseudo-boehmite samples with their sulfate radicals(SO2-4) concentration ranging from 0.9% to 3.0% were prepared by the reaction of Na Al O2 solution on Al2(SO4)3 solution. The existing form of sulfate radicals was investigated. Results have shown that sulfates in pseudo-boehmite included two parts, the soluble sulfate radicals and the insoluble sulfate radicals, which accounted for 99% of the total amount of sulfate radicals. XRD, low-temperature N2-adsorption, and TEM were used to characterize the properties of these pseudo-boehmite samples. Results have shown that the relative crystallinity and crystal size of pseudo-boehmite decreased with the increase of sulfate radicals in the support. In the meanwhile, the bound water content in pseudo-boehmite increased. The TEM images of pseudo-boehmite indicated that the pseudoboehmite was prone to become amorphous hydrated alumina. However, the effect of sulfate content on the specific surface area and pore structure of aluminium oxide was insignificant.