Pd/PA-Ca催化剂低温催化苯甲醛氧化制备苯甲酸

以植酸钙(PA-Ca)为载体、H2Pd Cl4为前驱体、甲醇为还原剂,制备了PA-Ca负载Pd的Pd/PA-Ca催化剂,对其进行XRF、BET、SEM、TEM、XRD和XPS表征,并用于苯甲醛氧化制备苯甲酸反应,考察催化剂用量、反应温度和溶剂种类对催化剂催化性能的影响。结果表明,催化剂中负载Pd质量分数为1.03%,钠质量分数为1.05%;合成的PA-Ca载体为晶化程度较低的介孔材料,比表面积为18.85 m~2·g~(-1);催化剂活性物种为Pd0和PdO。在催化剂用量n(苯甲醛)∶n(Pd)=2 000∶1、乙腈作溶剂、O_2压力101.325 k Pa(流速20 m L·min~(-1))、反应温度30℃和反应时间4 h条件下,苯甲醛转化率为83%,苯甲酸选择性为100%;催化剂具有较好的稳定性,可循环使用3~4次。

Oxidation of benzaldehyde to benzoic acid catalyzed by Pd/PA-Ca catalyst at low temperature

A novel catalyst (Pd/PA-Ca) of palladium nanoparticles supported on phytic acid calcium (PA-Ca) was prepared by methanol reduction of palladium chloride acid.The as-prepared catalyst was characterized by XRF,BET,SEM,TEM,XRD and XPS.Pd/PA-Ca catalyst was applied in the oxidation of benzaldehyde. The effects of catalyst amounts,reaction temperatures and solvent types on the catalytic performance of Pd/PA-Ca catalyst were investigated.The results indicated that the mass fraction of Pd and Na in the catalyst were 1.03% and 1.05%,respectively;the prepared PA-Ca support was a typical mesoporous material with low crystallization and the specific surface area of 18.85 m² · g^-1;the active species in the catalyst were Pd0 and PdO.The conversion of benzaldehyde and the selectivity to benzoic acid were 83% and 100%,respectively under the condition as follows:n(benzaldehyde)∶n(Pd)=2 000∶1,acetonitrile as the solvent,O2 pressure 101.325 kPa and flow rate 20 mL·min-1,reaction temperature 30 ℃ and reaction time 4 h.The catalyst exhibited good stability and could be reused (3-4) times.