糠醛液相加氢用Mo改性Ni-B/TiO2-Al2O3(S)非晶态合金催化剂

以溶胶-凝胶法制备复合载体TiO2-Al2O3(S)负载非晶态Ni-B合金用于催化糠醛液相加氢反应, 并研究了Mo对催化剂的改性作用. 采用ICP(等离子发射光谱)、DSC(差示扫描量热)、N2吸附、TPR(程序升温还原)和TPD(程序升温脱附)等技术对催化剂进行了表征. 研究结果表明, 与单一氧化铝载体相比, 复合载体负载的Ni-B合金催化性能明显提高, 这是由于在同样的制备条件下, 复合载体负载的Ni-B中Ni含量更高, 同时TiO2分散到了γ-Al2O3的孔中, 堵住了部分细孔, 有利于产物糠醇扩散出来, 防止深度加氢. Mo能提高Ni-B/TiO2-Al2O3(S)的热稳定性, 增大Ni的负载量, 使部分氧化态物种变得易于被还原, 表面出现新的加氢活性中心, 并增加化学吸附中心数, 减弱吸氢强度, 因而显著提高了Ni-B/TiO2-Al2O3(S)的活性; Mo添加使Ni-B/TiO2-Al2O3(S)的平均孔径及总孔容均增大, 有利于产物糠醇扩散出来, 还能使糠醇更易从催化剂的表面脱附, 防止其深度加氢, 因而提高了糠醇的选择性. 当Mo含量为1.25%时, 糠醛转化率、糠醇选择性都达到了100%.

Modification of Ni-B/TiO2-Al2O3(S) Amorphous Alloy Catalyst by Mo for Liquid-phase Furfural Hydrogenation

The effects of Mo on the catalytic and surface properties of amorphous alloy Ni-B/TiO2-Al2O3(S) had been studied. Liquid-phase furfural hydrogenation to furfural alcohol was selected as probe reaction. The properties of the catalysts were characterized using ICP, DSC, N2 adsorption, TPD, and TPR, respectively. The catalytic activity of Ni-B/TiO2-Al2O3(S) was higher than that of Ni-B/γ-Al2O3, which was due to the more Ni content in the former. Moreover, the decrease of micro-pore number leaded to higher selectivity, since the diffusion of the product in micropore was difficult. The addition of Mo could make Ni be reduced easier, produce new active centers over the surface of the catalyst, weaken the strength of Ni—H bond, and increase the number of adsorption centers, which resulted in the increasing activity of Ni-B/TiO2-Al2O3(S). Mo could enlarge the average pore size and volume, resulting in the easier diffusion of furfural alcohol to the surface of catalyst. At the same time, the results of TPD showed that Mo made furfural alcohol desorb easier from the catalyst surface. Therefore, the selectivity of the catalyst was improved. When Mo Content was 1.25%, both of the activity and selectivity of the catalysts reached to 100%.