加氢脱氮催化剂中硫化钼结构的表征

CHARACTERIZATION OF THE STRUCTURE OF SULFIDIC MOLYBDENUM IN HYDRODENITROGENATION CATALYST

众所周知,重油加氢脱氮(HDN)所用Mo-Ni/Al2O3催化剂需经预硫化后始有显著的活性,关于硫化的条件工业上已较成熟,但在持续反应过程中硫化催化剂的结构与活性间的关系则很复杂,如硫化钼的价态和结构、金属组分和担体间的相互作用、反应条件及原料对催化剂组分的影响,以及硫化态催化剂中MoS2结晶的形貌等都可以引起催化剂活性本质的变化.

Low temperature O2 chemisorption (LTOC) and transmission electron microscopy (TEM) have been used to study the coordinately unsat-urated Mo ions and the MoS2 crystallites on presulfided and industrially used hydrodenitrogenation (HDN ) catalysts. The amount of O2 chemisorption increases significantly for the used catalyst. This observation is consistent with the results of the presulfided catalyst followed by H2 treatment at temperatures higher than 370℃. It implies the loss of sulfur ions from sulfidic molybdenum of HDN catalyst during reaction process. After resulfidation of the used catalyst, the O2 uptake decreases and the change of morphology of MoS2 crystallite also takes place. On the basis of the results obtained the causes of deactivation of the HDN catalyst are discussed.