一步液滴法合成酸性和孔道属性可调的硅铝酸盐载体及其Pd基催化剂的性能研究

通过一步液滴法在不同的反应溶剂体系下制备了一系列无定形硅铝酸盐载体, 并进一步制备出Pd基负载型多孔催化材料, 探究了反应溶剂极性和反应物Si/Al比对载体材料和催化剂的影响, 实现了通过一步液滴法调控硅铝酸盐酸性和孔道属性. 结果表明, 在极性较小的反应溶剂体系中制得了富含介孔的无定形硅铝酸盐载体材料, 并且通过改变Si/Al比可实现载体材料的酸性、 比表面积及孔道尺寸的调控, 比表面积和总酸量分别达到349.6 m²/g和1.389 mmol/g. 由于该载体材料高的比表面积及丰富的介孔孔道, 所制得的Pd基负载型多孔催化材料的Pd金属分散性达到了63.17%, 在硝基苯加氢反应中实现了99.75%的转化率和94.62%的选择性, 在苯甲醇氧化反应中表现出40.61%的转化率及38.09%的选择性, 远远优于利用商用载体合成的 Pd/Al₂O₃催化材料. 这种简单有效的合成方法使得按照目标催化反应的类型来设计高效催化剂成为可能.

One-step Synthesis of Amorphous Silica Aluminum Support Materials with Controllable Acidity and Porosity and Catalytic Performance of Their Pd-based Catalysts

The catalytic performance of porous material-supported catalysts depends significantly on the acidity and porosity of support materials. One of the most critical challenges in the field of support-based catalysts is to effectively control the acidity and porosity of support materials simultaneously. Herein， we synthesized a series of porous amorphous silica aluminum（ASA） support materials by a spontaneous self-assembly process in different solvents. Further， porous ASA supported Pd catalysts were prepared by an impregnation method. Particularly， the effects of the polarity of solvent and the initial Si/Al ratio of ASA on the support materials as well as the obtained catalyst were investigated thoroughly. Results show that synthesis in a solvent with lower polarity produces ASA materials possessing abundant mesopores. And by means of tuning initial Si/Al ratio， the acidity， BET surface area， and pore size of ASA materials can be controlled readily. The optimal synthesis condition achieves a BET surface area and total acid amount up to 349.6 m²/g and 1.389 mmol/g， respectively. Due to the high BET surface area and abundant mesopores， the as-prepared ASA-supported Pd catalyst exhibits high dispersion of Pd metal particles， the dispersion of Pd is up to 63.17%. As a result， the obtained catalyst outperforms excessively its counterpart supported on commercial Al₂O₃， achieving a conversion of 99.75% and a selectivity to phenylamine of 94.62% for the hydrogenation of nitrobenzene and a conversion of 40.61% and a selectivity to benzaldehyde of 38.09% for the oxidation of benzyl alcohol. This facile and effective synthesis method makes it possible to synthesize efficient catalysts according to desired catalytic reactions.