Zhenfeng Sun,Kaiqiang Zhao,Chen Wang,Jie Li,Haisheng Xu,Chao Yang
Presulfiding agents are widely used in oil refining and chemical industry, how to produce safe and efficient presulfiding agent by more environmentally friendly synthesis process are still problems to be solved. In this study, the organic polysulfide FSA-55 was synthesized by a practical one-pot process using isobutene and sulfur as raw materials and organic amine as a catalysts. The product components were analyzed and the possible catalytic reaction pathways in the thermal conversion of sulfides were elucidated. The amine catalysts showed a catalytic activities in inducing the ring opening of the cyclic molecular structure of sulfur at high temperature, thereby releasing the reactive sulfur radicals, which react with unsaturated double bonds through addition reactions. Different molecular structures of polysulfide were generated through molecular rearrangement and cyclization reactions. The suitability of the product as a presulfiding agent was investigated by analyzing the thermal properties and studying the presulfiding effect on hydrogenation catalysts. The polysulfide has a wide decomposition temperature range (100–260 °C), which can effectively avoid the occurrence of concentrated exothermic phenomena during presulfiding of hydrogenation catalysts. The presulfiding degree of the catalysts can reach 58.32%, which shows the great potential of oil processing as a presulfiding agent.
Yang Bai,Fuxiang Feng,Lei Tian,Yankun Xiong,Yong Yang,Qiang Guo,Yuan Liu
To advance the direct coal liquefaction (DCL) technology by a “Catalytic cycle of hydrogen donor solvents” pathway, it was important for the iron-based DCL catalyst to be pre-sulfurized under a suitable condition. In this report, the effect of liquid medium in the slurry bed pre-sulfurization process on iron-based catalyst was studied. Catalysts were pre-sulfurized under a variety of liquid mediums including alkanes, aromatics and heteroatom-containing compounds and the activity were evaluated according to their performance on hydrogenation of naphthalene . It was observed that, the nitrogen-containing medium give rise to the significant negative influence on the catalytic activity (with only 2.5 %-15.3 % of naphthalene conversions). Multiple spectroscopic and microscopic analyses of catalysts exhibited that the decrease of S vacancies was mainly responsible for the low activity. It was due to the promotion effect on Fe 1-x S crystallization and troilite generation. S vacancies of the iron-based catalysts was considered as Lewis acid sites to catalyze the hydrogenation reaction. The new findings from this work is beneficial for the development and optimization of pre-sulfurization technology .
A Co-Mo sulfide catalyst with tube-like structure was prepared through a low-temperature pre-sulfurization process using rod-like CoMoO 4 as the precursor. The pre-sulfurization temperature greatly affected the total pore volume, the concentration of CoMoS species, the microstructure of (Co)MoS 2 slabs and the catalytic desulfurization activity. The increased temperature can promote the formation of hollow structure and the sulfurization degree of the precursor. It was found that the excessive temperature induced the Co atoms to form more isolated Co 9 S 8 species, hindering the formation of highly active CoMoS species. Therefore, appropriate temperature is more favorable to form the (Co)MoS 2 slabs with shorter length and higher stacking number, leading to more coordinatively unsaturated sites, especially the corner sites. According to the results of hydrodesulfurization reaction, the reaction rate of dibenzothiophene and the yields of liquid products are highly depended on the number of surface-active sites, which are mainly originated from the Type II CoMoS species. Moreover, the extended pre-sulfurization time can further improve the catalytic desulfurization activity of the catalyst at an appropriate pre-sulfurization temperature.
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