制备温度对Pd/C加氢脱氯催化剂失活的影响

Effect of Preparation Temperature on Deactivation of Pd/C Catalysts in Hydrodechlorination

在气固连续固定床反应器上对不同温度制备的Pd/C催化剂于145℃下进行了加氢脱氯寿命实验.结果表明,随着催化剂制备温度的升高,催化剂失活加快.采用XRD和DTA对新旧催化剂进行了表征,结果表明,积炭是催化剂失活的主要原因,并且随着制备温度的提高,由于大的活性基团的形成,积炭反应速度加快.在催化剂的制备与反应过程中,载体发生了明显氢化,随制备温度的提高,Pd/C催化剂载体的燃烧温度由纯载体的610～625℃降低到589℃左右,并且制备温度大于450℃后在530℃左右出现了1新的燃烧峰.随反应时间的延长,载体加氢程度加深,失活后载体的燃烧峰均出现在490～500℃之间,且载体的氢化程度与催化剂的活性有一定的相关性.

The life of each of Pd/C catalysts prepared at different temperatures was tested on a continuous gas solid fixed bed reactor at 145 ℃. The results show that the deactivation rates of catalysts were speeded up with increasing the preparation temperature. When the as prepared and used catalysts were characterized by XRD and DTA, it was found that carbonaceous deposit was the main factor of the deactivation of catalysts. As the preparation temperature increased, the rates of the carbonaceous deposits were speeded up due to the formation of big active particles of metal. During the preparations of catalysts and the hydrodechlorination reaction, the supports of catalysts were apparently hydrogenated. With the preparation temperature increasing, the burning temperature of the supports of Pd/C catalysts lowered from 610~625 ℃ of pure supports to about 589 ℃. When the preparation temperature was over 450 ℃, a new burning peak of the supports appeared at about 530 ℃ . The degree of hydrogenations of supports was greater with the reaction time increasing. The burning peaks of all the supports appeared at 490~500 ℃ after deactivation of catalysts. And the hydrogenation degrees were related to the deactivation of catalysts.