加氢脱氯Pd/C催化剂失活原因探讨

Study on the Cause of Deactivation of Pd/C in the Hydrodechlorination Reaction

在自制的气-固连续固定床反应器上,在反应温度为145℃,氢气体积流速为140ml/min,空速为10g/(g·cat)的条件下,对采用传统浸渍方法制备的载钯量为1.25%(质量分数)的Pd/C催化剂的寿命进行评价。其实验结果表明,Pd/C催化剂是氯乙酸母液混酯选择性加氢脱氯制备氯乙酸甲酯优良的催化剂。为了找到催化剂失活的原因,分别对反应前后的催化剂进行了XRD,差示热分析(DTA)和X射线光电子光谱(XPS)分析。结果表明,催化剂表面炭化物沉积是催化剂失活的主要原因,积炭物中以物理吸附的非永久性积炭为主,并可以通过惰性气体吹扫而除掉。

1.25 wt% Pd/C catalyst prepared by impregnation, which is used in the hydrodechlorination of mixed esters of mother liquor of chloroacetic acid, was studied. Experiment was carried out in a continuous gas-solid fixed bed reactor at 145° C, 140 ml/min of hydrogen and 10 g/(g.cat) space-time yield. In order to study the cause of deactivation, fresh and used catalysts were characterized by X-ray diffraction, thermogravimetry and X-ray photoelectron spectroscopy. Characterization results indicate that the deactivation is caused mainly by the formation of carbonaceous deposits. Most of the carbon depositions were physisorpted in the surface of catalyst, which can be removed by sweeping in indifferent gas.