Study On The Stabilty Of γ-Al₂O₃in Water Vapor At High Temperature

Aluminum oxide has been widely used in ceramics, medicine, catalyst and many fields. γ-Al2O3plays a critical role as a support due to its high surface area, porosity and acidity. In this paper, we researched the hydrothermal technology of alumina and the hydrothermal stability of alumina derived from different pseudo-boehmite, and improved the hydrothermal stability of γ-Al2O3by introducing phosphorus. The aluminum oxides were characterized by means of XRD, BET, SEM and FT-IR and so on. Main results from this work are as follows:Compared with the influence of water vapor treatment and hot water treatment in the autoclave on the hydrothermal stability of alumina, and the autoclave within the alumina was heated to180℃and kept for24.0h was used to investigate its hydrothermal stability. We also studyed the influence of pseudo-boehmite on the hydrothermal stability of Al2O3. It was found that the hydrothermal stability of the γ-Al2O3is determined by the crystallinity of pseudo-boehmite. The well crystallized γ-Al2O3compared with poor crystallized one exhibits higher hydrothermal stability. Hydrothermal modification can improve the crystallinity of pseudo-boehmite, thus improve the hydrothermal stability of Al2O3.The influence of phosphorus content and phosphorus salts on the hydrothermal stability of γ-Al2O3:ammonium phosphate is found the best phosphorus source on alumina modification compared with other phosphorus sources.The phosphorus content needed for alumina modification is different. The hydrothermal stability of A1can be greatly improved after0.5percent phosphorus modification. But for A3which has poor hydrothermal stability, it is found that1%phosphorus is enough to restrain its hydration.The Ni-based catalyst supported on the P-modified alumina was used for the production of substitute natural gas (SNG) from syngas:CO conversion was99%, the yield of methane was22m3/100m3, the deactivation was not observed for the P-modified catalyst even after having been tested for a long time which means that the catalyst has high stability. The carbon deposition for the used P-modified catalyst decreased significantly compared with unmodified one, means that the Ni-based catalysts supported on the P-modified alumina has the resistance to carbon deposition.