Hydrogenation-Esterification Of Aldehyde And Acid To Ester By One-Step Heterogeneous Catalysis

Biomass is the sole renewable carbon resource that can be transferred into gas, liquid and solid fuels as well as other chemicals. As the fossil energy will be exhausted, new energy has been attracted more and more attention in the world. At present, the major work is focused on the research and development of biomass energy to substitute for fossil energy. Bio-oil, i.e., oil from biomass cracking, has advantages of a large supply of renewable and cheap raw materials, high quantity of heat and low pollution when being used as liquid fuel after upgrading. Therefore, bio-oil upgrading became one of hot research subject in the field of energy chemical engineering. However, the intrinsic disadvantages such as high viscosity, thermal instability, corrosiveness, and chemical complexity bring many obstacles to the substitution of fossil derived fuels by bio-oils. Thus, the properties of bio-oils depend that it cannot be used directly for engine fuel, it need to upgrade to more stable for high quantity fuel oil. At present, a large number of studies were individually focused on hydrogenation and esterification. Many researchers had reported these two approaches, but few combined it into one step for bio-oil upgrading. In this paper, the major work is focused on the study of bifunctional catalysts preparation and the performance of catalytic hydrogenation-esterification reaction over bifuncational catalyst.The effects of various supports on reaction performance of Pt-Co based catalysts were studied. The results showed that the magnitude of metal-support interaction was an important factor affecting catalyst performance. The Pt-Co based catalysts supported different support such as Pt-Co/γ-Al2O3, Pt-Co/SO42--TiO2/γ-AlO3 and Pt-Co/HZSM-5 exhibited great difference in activity. It was first found that HZSM-5 was an excellent support of Pt-Co catalysts for direct heterogeneous hydrogenation-esterification of acetaldehyde and acetic acid. In comparison with Pt-Co/HZSM-5 catalyst, Pt-Co/γ-AlO3 and Pt-Co/SO42--TiO2/γ-Al2O3 catalysts showed poor activity. The results indicated that the optimal reaction conditions for Pt-Co/HZSM-5 catalyst were as follows:the reduction temperature is 400℃, the reaction temperature is 240℃, the calcination temperature is 450℃, and the catalyst amount is 2.0g.The Ni/HZSM-5 and Co/HZSM-5 single metal bifunctional catalysts were prepared using HZSM-5 as support by the incipient-wetness impregnation method. For Ni/HZSM-5 and Co/HZSM-5 catalysts, the effects of Ni/Co loading, calcining temperature, reduction temperature, reaction temperature, the molar ratio between H2 and aldehyde and catalyst amount on catalyst activity were systematically studied. The results showed that the optimal reaction conditions for Ni/HZSM-5 catalyst are as follows:the loading of Ni is 15%, calcination temperature is 723K, reduction temperature is 973K, reaction temperature is 473K, Hydrogen/aldehyde ratio is 5 and catalyst amount is 2.0g. Compared with the Ni/HZSM-5 catalyst, the optimal reaction conditions for Co/HZSM-5 catalyst are as follows:the loading of Co is 10%, calcination temperature is 723K, reduction temperature is 773K, reaction temperature is 513K, Hydrogen/aldehyde ratio is 5 and catalyst amount is 2.0g. It was found that compared with the Co/HZSM-5 single metal bifunctional catalyst, the Ni/HZSM-5 single metal bifunctional catalyst showed higher activity.Two noble catalysts, Pt-Ni/HZSM-5 and Pt-Co/HZSM-5, for upgrading bio-oil by heterogeneous hydrogenation-esterification of acetaldehyde and acetic acid have been studied. For Pt-Ni/HZSM-5 and Pt-Co/HZSM-5 catalyst, the effects of loading, calcining temperature, reduction temperature, reaction temperature, the molar ratio between H2 and aldehyde and catalyst amount on catalyst activity were systematically studied. It was found that added a small amount of Pt exhibited optimal activity than Ni/HZSM-5 and Co/HZSM-5 catalysts. The result of XRD confirmed that the small amount of Pt dispersed highly on the catalyst and promoted the improvement of catalyst activity.