渣油加氢处理催化剂积炭分析

Analysis of Coke on Spent Catalysts Used for Residue Hydrotreating Process

采用热重、差热分析、低温氮吸附、元素分析等技术对渣油加氢处理过程中5种催化剂上的积炭进行了分析。结果表明,结焦催化剂表面积炭沉积和孔道堵塞现象严重,比表面积和孔容大量损失,孔分布向小孔范围迁移,催化剂孔径越小,损失越严重。催化剂上沉积的焦炭可分为低温型和高温型两种,前者燃烧放热集中在400℃左右,后者集中在470℃左右。积炭形成类型与积炭前身物——沥青质的结构有关,芳香碳分率低,缩合指数小的沥青质形成低温型积炭;芳香碳分率高,缩合指数大的沥青质形成高温型积炭。催化剂促使沉积物脱氢形成积炭,并且使积炭从低温型向高温型转化,催化剂活性越高,转化越明显。

The cokes on catalysts from residue hydrotreating process were analyzed by using TG,DTA, low temperature N2 adsorption and elementary analysis. The results shown that the surface was covered and the pores were blocked obviously for the coked catalysts, the specific surface area and pore volume lost greatly,pore size distribution shifted to small pore end. The smaller pore size was, the more severity pore lost. The deposited coke was divided into two types, low-temperature type and high-temperature type, the former burning mainly at 400 ℃, the later at 470 ℃. The coked type was related to the structure of precursor （asphaltene）. The asphaltene with lower aromaticity and condensed index would produce low-temperature type coke, while The asphaltene with higher aromaticity and condensed index would produce high-temperature type coke. Catalysts made the deposition dehydrogenate to form coke and the coke convert from low-temperature type to high-temperature type. The higher the catalyst activity was, the more the conversion was.