Preparation And Catalytic Properties Of Ni-W-B Amorphous Catalysts For 4-cresol Hydrodeoxygenation

Traditional energy causes serious pollution to the environment, leading to ecological destruction. Energy shortage, environmental pollution and ecological damage are bottlenecks which constrain economic development. Developing new renewable green environmental protection resources is already in the extremely urgency. Bio-oil is the liquid production of fast pyrolysis of biomass particles(wood,straw, etc.) under the conditions of isolated from oxygen and high temperature(773~873 K). Bio-oil has attracted a lot of attentions because of its properties of abundance, easy to transport, renewable and high energy density. However, this lignocellulosic-derived bio-oil contains a considerable amount of oxygenated compounds, resulting in some defects such as thermal instability, easy corrosion, low heating value, incompatibility with conventional fuels, and high viscosity, which hinders its wide utilization as fuel. So we need further hydrogenation deoxidization refined. Therefore, the development of oil hydrogenation deoxidization modification research is of great significance for the preparation of new oil alternative energy.Among many oxygen-containing groups in the bio-oil, phenolic hydroxyl oxygen is considered as the most difficult one to remove because the C-O σ-bond is attached to aromatic ring and then cleavage of this bond needs high activation energy.Generally, phenols HDO mechanism includes direct hydrogenolysis(DDO) route yielding aromatic products and hydrogenation-dehydration(HYD) route producing cycloalkanes. The DDO route requires a high reaction temperature, HYD route can significantly decrease the reaction temperature, the key is to prepare a HDO catalyst with high activity. Amorphous catalyst has some interesting and intrinsic properties such as a microstructure of long-range disorder and short-range order, and high concentration of coordinative unsaturated sites, leading to its excellent activity and selectivity in the catalytic reactions.This study focused on the preparation of Ce-Ni-W-B amorphous catalysts by chemical reduction method and the effect of Ce content on their catalytic activities in the hydrodeoxygenation(HDO) of phenols in the bio-oil. Adding the promoter Ce could increase the content of Ni0 and WO3 on the Ce-Ni-W-B catalyst surface, leading to the improvement of the deoxygenation activity, but excess Ce would cover some active sites, resulting in a reduction of the catalytic activity. The HDO activity of catalyst mainly depended on the relative content of Ni0 and the molar ratio of Ni0andWO3 in catalyst surface. With an optimum content of the Ce promoter in the Ni-W-B amorphous catalyst(2.5% mol), the deoxygenation degree was up to 98.1% with a low selectivity of 1.0% toluene in the HDO of p-cresol under the conditions of temperature 498 K, hydrogen pressure 4.0MPa and time 1 hour. Based on this, adding ammonium hydroxide to prepare Ni-W-B amorphous catalysts. Ammonium hydroxide could control the reaction rate of metal ions with Na BH4. The main research was the effect of Ni/W molar ratio on their catalytic activities in the HDO of phenols in bio-oil.The difference of Ni/W molar ratio could control the balance between Ni0 and WO3,leading to the difference in the conversion and product distribution.With the decrease of Ni/W molar ratio, the hydrogenation activity of the catalyst was declined while the deoxygenation activity was enhanced. The catalyst had the highest activity of HDO when the Ni/W molar ratio was 1:3. After 4 hours, the deoxygenation degree was high to 88.4% at 498 K.