pH值调控构建的纳米Ni-W催化剂用于纤维素氢解制多元醇的研究

摘要

The Ni-W/SBA-15 catalysts prepared by incipient-wetness impregnation method and controlled by the pH value were developed.Potassium hydroxide and citric acid regarded as the pH value regulators were added to the solution before impregnation to provide an acidic or basic condition at different pH values (0.83, 1.00, 3.09, 5.00, 7.03, 8.97 and 11.0).The 74.5% yield of total low carbon (C2,3) polyols including ethylene glycol (EG), 1,2-propylene glycol (1,2-PG) and glycerol (Gly) was obtained over 10%Ni-20%W/SBA-15 catalyst prepared at pH value of 1.00 and 518 K under H2 pressure of 5.0 MPa.Furthermore, the physical properties of this series of nickel-tungsten catalysts were characterized by BET and SEM.The results demonstrated that the catalysts showed excellent thermal stability and the surface area was mainly in range of 330-450 m2/g.The particles had a good dispersion on the surface of SBA-15 but some aggregations were existed which could be characterized by TEM and SEM-EDX.However, the reduction of metallic oxides especially for NiO was obviously influenced by pH value control and some metallic species characterized by XRD.According to XRD results, the impregnation pH value influenced the reduction of NiO and the phase states of nickel and tungsten species.%采用等体积浸渍法制备了双金属Ni-W催化剂,并研究了制备过程中前驱体溶液pH值对活性的影响.柠檬酸和氢氧化钾分别作为酸碱调节剂将前驱体溶液pH值调节至0.83、1.00、3.09、5.00、7.03、8.97和11.0.纤维素氢解反应结果表明,当前驱体溶液的pH值为1.00时,在氢压为5.0MPa、温度为518K的反应条件下,得到低碳(C2,3)多元醇的总收率为74.5%.此外,通过BET和SEM表征了催化剂的物理性质.其比表面积为330-450m2/g,且在高温煅烧下SBA-15仍保持良好的水热稳定性.TEM和SEM-EDX结果显示,催化剂粒子在载体表面分散性较好,但也有少量的聚集现象.XRD表征表明,NiO等物种的还原程度明显受到pH值的影响,且镍、钨物种的相态也存在着显著不同.