烯烃对硫醚低温转化和NiMo催化剂表面组成的影响

Effect of olefin on hydro-conversion of thioether and surface composition over NiMo/Al2O3 catalyst at low reaction temperature

关键词:  烯烃  硫醚  竞争吸附  积碳  表面组成  镍钼催化剂 

Key words:  olefin  thioether  competitive adsorption  carbon deposition  surface composition  nickel-molybdenum catalyst.

摘要:

以Al₂O₃为载体采用等体积分步浸渍法制备了NiMo/Al₂O₃催化剂,在固定床反应器上研究了在相对较低的温度(200 ℃)条件下,烯烃的加入对甲基叔丁基硫醚的加氢转化的影响。实验结果表明,烯烃与硫醚在催化剂表面发生竞争吸附,其加入对硫醚的转化有明显的抑制作用。采用SEM电镜,S、C元素分析和X射线光电子能谱对催化剂的表面组成及形态进行表征,发现烯烃使得催化剂表面出现明显的颗粒聚集和结块现象,积碳量增加;同时,导致Ni向催化剂的表面迁移,Mo⁴⁺/Mo⁶⁺比值减小,Ni⁰/ Ni²⁺比值增大,这均在一定程度上减弱了催化剂的活性。 

Abstract:

Using Al₂O₃ as the support, the NiMo/Al₂O₃ catalyst was prepared by incipient wetness impregnation method. The effect of olefin on tert-butyl methyl sulfide hydro-conversion was researched in fixed bed reactor at relative low temperature of 200 ℃ over NiMo/Al₂O₃ catalyst. The result showed that the added olefine reduced conversion of thioether significantly because of competitive adsorption in the surface of catalyst. The surface composition and morphology of catalyst samples were characterized by scanning electron microscope, sulfur and carbon element analysis and X-ray photoelectron spectroscopy. The results indicated that the added olefin made catalyst surface appearing obvious particles aggregation, agglomeration and carbon deposition; and it resulted in Ni migration to the surface of the catalyst, decrease of Mo⁴⁺/ Mo⁶⁺ and increase of Ni⁰/Ni²⁺, which could reduce the activity of the catalyst in a certain degree.