Preparation Of Spherical Alumina With High Hydrothermal Stability And Its Application In Catalysis

Catalyst palys a decisive role in the field of chemical industry because 85% of the chemical reaction is done under the effect of catalyst 70% of the catalyst is the supported catalyst. The support plays a very important role in the supported catalyst. Y-Al2O3 reflects broad industrial application in numerous support because it has a large specific surface area, specific pore structure, easy forming and many other advantages. Spherical γ-Al2O3 support usually is prepared pseudo-boehmite as precursor by oil-ammonia-column method or oil-column method, so the performance of support is closely related to the physical and chemical properties of pseudo-boehmite.In this paper, in view of bad hydrothermal stability of Al2O3 support, we research the controllable preparation of pseudo-boehmite with large specific surface area by controlling the nucleation and growth process of pseudo-boehmite with Al2(SO4)3 and NaAlO2. The hydrothermal stability of pore structure of spherical γ-Al2O3 support that prepared pseudo-boehmite as precursor by oil-ammonia-column method and its influencing factors are studied through the accelerated hydrothermal aging means. We preliminarily research the catarytic activity and stability of two catalyst that prepared by the prepared spherical y-Al2O3 as support respectively loading Pd or PtSn applying in anthraquinone hydrogenation process and n-heptane platinum reforming reaction.Firstly, we can prepare pseudo-boehmite from Al2(SO4)3 and NaAlO2 by nucleation crystallization separation method and coprecipitation method. Then XRD, BET, SEM and other characterization techniques are used to analyze its structure, surface morphology. The results show that the specific surface area of pseudo-boehmite prepared by nucleation crystallization separation method and coprecipitation method are respectively 445 m2·g-1 and 328 m2·g-1 more than the specific surface area of the commercial SB(261 m2·g-1).Then, we can prepare spherical Al2O3 material using precursor synthesized by nucleation crystallization separation method, coprecipitation method and template method as raw material through the oil-ammonia-column method, respectively marked as Al2O3-Ⅰ, A12O3-Ⅱ and Al2O3-Ⅲ. Then XRD, BET, SEM and other characterization techniques are used to analyze its crystal structure, surface morphology and pore structure. The results show that the specific surface area of Al2O3-Ⅰ and Al2O3-Ⅱ are respectively 280 m2·g-1 and 330 m2·g-1 more than the specific surface area of Al2O3 from Sasol (210 m2·g-1).The phenomenon that the specific surface area of Al2O3-Ⅰ and Al2O3-Ⅱ maintains 185 m2·g-1 more than the specific surface area of Al2O3 from Sasol (140 m2·g-1 ) after 192 h hydrothermal treatment illustrates perfect hydrothermal stability of spherical Al2O3 by these methods. Al2O3 prepared P123 as template has ordered mesoporous and its specific surface area is 340 m2·g-1 ,while its specific surface area maintains 220 m2·g-1 after 48 h hydrothermal treatment.Finally, We research the catalytic activity and stability of two catalyst that prepared by the prepared spherical y-Al2O3 respectively as support loading Pd or PtSn applying in anthraquinone hydrogenation process and n-heptane platinum reforming reaction. The results show hydrogenated efficiency of Pd/Al2O3-Ⅰ and Pd/Al2O3-Ⅱ are respectively 6.50 g·L-1 and 8.10 g·L-1 in anthraquinone hydrogenation process. The phenomenon that hydrogenated efficiency of Pd/Al2O3-Ⅱ is close to the traditional Pd/Al2O3 which is 8.25 g·L-1 illustrates its application prospect in anthraquinone hydrogenation field. PtSn/Al2O3-Ⅱ has a good conversion and reusability in n-heptane platinum reforming reaction. Conversion of n-heptane is up to 65%, and the performance of regeneration catalyst and fresh catalyst looks alike. PtSn/Al2O3-Ⅱ has potential application value in the field of platforming catalyst.