Pd/CNTs对4-氯苯酚的液相催化加氢去氯

Liquid-phase catalytic hydrodechlorination of 4-chlorophenol over Pd/CNTs

以浓硝酸酸化后的多壁碳纳米管(CNTs)为原料,PdCl_2为前体,甲醛为还原剂,采用化学浸渍法制备了5%Pd/CNTs催化剂。通过ICP、XRD、BET、TEM对其进行表征,证实5%的钯纳米粒子成功负载在CNTs管外壁上,钯纳米粒子的平均粒径为4.30nm。在合成Pd/CNTs催化剂的基础上,研究了温和条件下其对4-氯苯酚(4-CP)的液相催化加氢去氯(HDC)规律。考察了体系反应温度、催化剂用量、NaOH用量、反应底物浓度对4-CP降解速率的影响,建立了动力学模型。得到了最佳反应条件:反应温度40℃,催化剂用量20mg,Cl~–、OH~–摩尔比1∶1.1;Pd/CNTs对4-CP加氢去氯反应为零级反应,反应活化能为E_a=40.12k J/mol,指前因子A=1.66×10~7mol/(L·min)。

5% Pd/CNTs was synthesized by chemical impregnation method using multi-walled carbon nanotubes （CNTs） which was acidified by concentrated nitric acid as starting materials, PdCl2 as precursor and formaldehyde as reducing agent. The catalyst was characterized by means of ICP, XRD, BET and TEM. The results showed that 5% Palladium nanoparticles were successfully loaded on the outer wall of the CNTs tubes and the mean diameter of the Pd nanoparticles was 4.30nm. The performance of the Pd/CNTs catalysts in the liquid-phase catalytic hydrodechlorination （HDC） of 4-chlorphenol （4-CP） under mild conditions was also investigated. Effects of reaction temperature, catalyst and NaOH dosage, substrate concentration , as well as the reaction kinetics were studied. The optimized operating parameters were obtained as reaction temperature 40 ℃, catalyst dosage 20mg, and Cl^- ： OH-=1 ： 1.1 （molar ratio） . The reaction kinetics could be described by a zero-order kinetics model. The activation energy Ea and pre-exponential factor A were estimated as 40.12kJ/mol, and 1.66× 10^7mol/（L·min）, respectively.