载体焙烧温度对Pd/TiO2催化剂上对羧基苯甲醛加氢性能的影响

 采用浸渍法以TiO₂成型载体制备了Pd/TiO₂催化剂。采用BET、XRD、XPS、H₂-TPR等手段对所制备的催化剂进行了表征。将不同温度下焙烧的TiO₂为载体制备的Pd/TiO₂催化剂用于粗对苯二甲酸(CTA)中的主要杂质对羧基苯甲醛(4-CBA)的催化加氢反应，考察了载体焙烧温度对其所制备的催化剂活性的影响。结果表明，随着TiO₂成型载体焙烧温度的升高， Pd/TiO₂催化剂的比表面积和孔容降低，平均孔径增大。Pd/TiO₂催化剂样品XRD谱中未检测到金属Pd的特征衍射峰，同时催化剂中TiO₂的晶相始终保持锐钛型结构。Pd/TiO₂催化剂表面Pd的比表面积随着载体焙烧温度的升高而降低。载体焙烧温度的高低可改变PdHx物种在其所制备的催化剂表面的数量及其结合状态。当TiO₂载体焙烧温度为500℃时，所制备的Pd/TiO₂催化剂表面Pd的比表面积最大，催化剂的加氢活性最高，在反应温度280℃、H₂分压0.6 MPa、反应时间0.3 h的条件下，4-CBA转化率可达到99.5%以上。

EFFECTS OF SUPPORT CALCINATION TEMPERATURE ON p-CARBOXY BENZALDEHYDE HYDROGENATION PERFORMANCE OF Pd/TiO2 CATALYSTS

Pd/TiO2 catalysts were prepared by the impregnation method with the formed TiO2 as supports and were characterized by BET, XRD, XPS and H2-TPR techniques. The effects of calcination temperature of TiO2 support on the hydrogenation activity of Pd/TiO2 catalysts for p-carboxy benzaldehyde(4-CBA), the main impurity in crude terephthalic acid (CTA), were investigated. Results showed that the surface area and pore volume of Pd/TiO2 catalysts decreased, however, the average pore size increased with the increase of TiO2 support calcination temperature. No Pd metal phase was detected in Pd/TiO2 catalysts, and the crystal phase of TiO2 remained anatase when the TiO2 support was calcined below 800℃. It was found that increasing the calcination temperature of TiO2 support would lead to the decrease of the surface area of Pd. The TiO2 support calcination temperature could change the amount and the binding state of PdHx species on the surface of Pd/TiO2 catalyst. The Pd/TiO2 catalyst prepared with TiO2 support calcined at 500℃ exhibited its highest catalytic activity, over which the conversion of 4-CBA was over 99.5% under reaction temperature of 280℃, H2 partial pressure of 0.6 MPa and reaction time of 0.3 h.