Ni-La/AC甲醇气相羰基化催化剂失活行为的研究

采用等容浸渍法制备了Ni-La/AC双金属催化剂,在连续流动固定床反应装置中,于260℃、1.5 MPa、CO/CH3OH/CH3I摩尔比20/19/17、.5 g-cath.mol-1条件下考察了催化剂的稳定性,并通过BET、XRD、TPR和ICP等技术手段对甲醇气相羰基化反应失活前后Ni-La/AC催化剂进行了表征,考察了催化剂在反应过程中的结构变化和失活行为。结果表明:La组分的引入促进了Ni在催化剂表面的分散,提高了反应的初活性。但是在长时间运转条件下,羰基化活性中心Ni晶粒发生聚集,成为积碳的活性中心,堵塞了部分催化剂微孔,使得催化剂比表面积减小导致催化剂失活。失活催化剂再生后,比表面积有所回升,但Ni晶粒明显增大,反应过程中失活速率加快。此外,活性金属镍的流失以及Ni、La在催化剂上分布的变化也是催化剂失活的原因之一。

Deactivation of Ni-La/AC Catalyst for Vapor Phase Methanol Carbonylation

A Ni-La/AC catalyst was prepared by incipient wetness impregnation techniques.The carbonylation reaction was carried out in a fixed bed reactor at pressurized condition in the presence of methyl iodide as the promoter.The stability and structure change of the fresh and the used catalysts were characterized by several characterization techniques(XRD,BET,TPR and ICP).The characterization results show that the addition of La improved greatly the dispersion of Ni on the surface of the support.Correspondingly,a high methanol conversion was obtained.But after a long reaction time,the reduced Ni accumulated on the surface of the catalyst,and formed the active centers for carbon deposition,resulting in the catalyst deactivation.The loss of Ni inside the catalyst and the change of Ni/La atom ratio on the catalyst surface were also the reasons of catalyst deactivation.In addition,the regeneration of deactivated catalyst was also investigated.Results showes that the BET surface area increased after the deactivated catalyst was regenerated by H_2,The regenerated catalyst had bigger granularity of Ni particle and higher deactivation rate than the fresh reduced catalyst.