The Role Of The Catalytic Properties Of Rare Earth Transition Metal Doped Mesoporous Alumina

Phenol is important fine chemical intermediates with high economical value. Until now the phenol production is still growing. The traditional methods of producing them always have Multi-step reactions, complicated processed many by-products such as acetone and other contaminations. It is inconsistent with the strategy for sustainable development. In recent years, as a more economical route, reaction of benzene direct hydroxylation to phenol aroused extensive concerns. Directly benzene oxidation to phenol, only one step from raw materials to the final product accords with the viewpoint of Green Chemistry.Supported several transition metals ordered mesoporous alumina was synthesized by sol-gel process with aluminum isopropoxide as aluminum source, glucose as template in acid condition. Catalytic activity test was carried out in the hydroxylation of benzene to phenol with aqueous hydrogen peroxide as oxidation agent, the reaction condition was that H2O2/C6H6(molar ratio)=3:1, reaction media is acetonitrile, temperature 60℃, reaction time 4h. The results show that transition metals supported ordered mesoporous alumina showed higher catalytic activity than the support alumina. We can conclude that transition metals in the framework of mesoporous alumina were the catalytic activity center. Cr/Al2O3 showed the best catalytic activity in all of them.Rare earth metals supported ordered mesoporous alumina was synthesized by sol-gel process in acid condition in the same. Catalytic activity test was also carried out in the hydroxylation of benzene to phenol with aqueous hydrogen peroxide as oxidation agent. Rare earth metals supported ordered mesoporous alumina showed higher catalytic activity than the support alumina.We found that Cr/Al2O3 showed the best catalytic activity in the synthesis process of transition metals supported ordered mesoporous alumina. Four kind of rare-earth metals (Er,Gd,Yb,Sm) were introduced into Cr/Al2O3 to enhance the catalytic activity. The prepared catalysts were characterized by X-ray diffraction, N2 absorption-desorption, TG-DSC, Temperature programmed reduction and Transmission electron microscopy. The results of benzene oxidation to phenol showed that the catalytic activities of catalysts were enhanced when rare-earth metals introduced into the catalysts. The selectivity of Yb-Cr/Al2O3 and Sm-Cr/Al2O3,Gd-Cr/Al2O3 came to be 100%. We elucidated structure- activity relationship elementally with respect to the characterization results.