Catalytic Properties Of Metal Clusters Enclosed In SBA-16

Ordered mesoporous silicas as one kind of inorganic material, which have been obtained by means of the corporative interaction between inorganic precursors and super-molecular surfactants through sol-gel process. Because of special cage structure and favoring for the diffusion of reaction molecules, SBA-16 is used in the filed of catalysis, adsorption, separation, drug carrier material and biological molecules.Firstly, this paper studies encapsulation of RhCl(TPP)3 in the cubic cage-like pore of SBA-16 mesoporous materials was prepared by flexible ligand method, and characterized by ICP-AES, XRD, N2 adsorption, SEM, TEM, FT-IR. The results showed that the complex RhCl(TPP)3 can be formed and entrapped in the supercages of SBA-16 mesoporous materials. The catalyst of RhCl(TPP)3/SBA-16 was used to carbonylation of methyl acetate. The influence of Rh loaded、ligand loaded、reaction temperature and reaction time on carbonylation reaction were investigated. Under the optimum reaction conditions n(Rh)/m(SBA-16)=0.48mmol/g, n(ligand)/m(SBA-16)=3.90mmol/g, 160℃, 6h and methyl acetate conversion rate is up to 79%, ethylidene diacetate selectivity is 67.7%. The prepared catalysts were stable and could be recycled three times without loss the activity.Secondly, the SBA-16 molecular sieves catalysts modified with different vanadium loading were prepared by incipient-wetness impregnation method. The structure properties of samples were characterized by XRD, SEM, TEM and N2 adsorption-desorption, which reveal that the SBA-16 molecular sieves catalysts possess a large surface, uniform pore size and 3D cubic porestructure. The surface active species were characterized with FT-IR, NH3-TPD, CO2-TPD and H2-TPR measurements, which confirms that highly dispersed VOx are main active species for dehydrogenation of ethylbenzene, V2O5 species with large particle size are beneficial to the reaction. Dehydrogenation of ethylbenzene(EB) to styrene(ST) in the presence of carbon dioxide was investigated over a series of SBA-16-supported vanadia catalysts(VOx/SBA-16) with the vanadium loading of 0.4–2.0 mmol/g. It was found that the highest activity was obtained under reaction condition: 300 mg VOx/SBA-16(1.2mmol/g) as catalyst, CO2 gas flow rate is 13.3mL/min, ethylbenzene flow rate is 0.3mL/h, reaction temperature at 550℃, reaction time for 12 h. Ethylbenzene conversion rate is up to 46.54%, the selectivity of styrene is 98.0%. Meanwhile, under the optimum reaction conditions, use the synthetic VOx/SBA-15 and VOx/MCM-41 catalysts respectively for catalytic performance testing. The three types of supported catalyst make a contrast on the selectivity and yield of the reaction product. The highest yield of the styrene obtained after the catalytic is vanadium species loading SBA-16 molecular sieves, which is higher than those of catalysts VOx/SBA-15 and VOx/MCM-41 with SBA-15 and MCM-41 molecular sieve as the supports.