裂解汽油加氢钯系催化剂中毒原因的分析

Cause of Poisoning of Palladium-Based Catalyst for Hydrogenation of Pyrolysis Gasoline

对某石化公司裂解汽油加氢装置的钯系催化剂在使用过程中出现的中毒失活问题进行了分析研究.比较了中毒催化剂与新鲜催化剂的晶相和钯含量,并分析了原料中砷、水和硫化物的含量及硫化物的分布.分析结果表明,中毒前后催化剂的晶相和钯含量没有明显变化,原料中砷、水和硫化物的含量在正常范围内,但原料中CS2含量较高,达到1.8 ～ 20.2 μg/g.分析了生产正常的裂解汽油加氢原料,原料中CS2的含量低于1μg/g.CS2、二甲基二硫醚和噻吩的致毒性评价实验结果表明,致毒性大小的顺序为：CS2＞＞二甲基二硫醚＞噻吩.由此确定了导致钯系催化剂中毒的物质是CS2.一段加氢原料中cS2含量与C5含量基本呈线性关系,将一段加氢原料中C5含量控制在0.5％（w）以下,cs2含量会降至1 μg/g以下,使加氢生产保持正常.

The deactivation of palladium-based catalyst for the hydrogenation of pyrolysis gasoline was investigated.The crystallite structure and palladium content of the poisoned and fresh catalyst were measured.The contents of arsenic,H2O and sulfides in the feedstocks were determined.The results showed that the crystallite structure and palladium content of the catalyst almost unchanged after poisoning.The contents of arsenic,H2O and sulfides in the feedstocks were within normal limits,but the content of CS2 in the feedstocks was high in the range of 1.8-20.2 μg/g.The CS2 content in feedstock should be less than 1 μg/g in well-running hydrogenation units.A deactivation test for the hydrogenation catalyst was carried out by adding CS2,dimethyl disulfide and thiophene to feedstock.The effects of the catalyst poisoning on the hydrogenation are in order of CS2 ＞＞ dimethyl disulfide ＞ thiophene.So the deactivation of the catalyst resulted from CS2 in the feedstock.The CS2 content is linearly related with the C5 content in the feedstock.The CS2 content in the feedstock is less than 1 μg/ g when the C5 content is less than 0.5％ （w）,and then the hydrogenation unit can run normally.