A Study On Adsorption And Migration Of Hydrogen On Fe_1-xS Catalysts For Direct Coal Liquefaction

Coal is rich in China,and a huge amount of coal is produced each year,but petroleum resource is short and heavily dependent on import to meet domestic strong demands.The development of direct coal liquefaction technology can reduce petroleum import and ensure national energy security.Iron based catalyst is one of important factors affecting efficiency of direct coal liquefaction and Fe_1-xS is the active component.Study on hydrogen transfer law is of great importance to reduce hydrogen consumption and improve oil yield in direct coal liquefaction.However,the present researches for the hydrogen transfer process don’t involve Fe_1-xS catalysts and there are not related studies on the interaction and migration of hydrogen on Fe_1-xS catalysts.Therefore,in this work,Fe_1-xS catalysts were chosen as the research target to explore their hydrogen storage behavior and their dehydrogenation and re-hydrogenation behavior in different systems,which could help us to understand the law of hydrogen migration behavior on Fe_1-xS catalysts from a new perspective.The main conclusions for the research are shown as follows.（1）The Fe_1-xS catalysts were firstly prepared by pre-sulfidation experiments with Fe₂O₃ precursors.Hydrogen adsorption on Fe_1-xS catalysts was indirectly confirmed by methods of H₂-TPD,H₂-TPR and elemental analysis（EA）.It was also found that hydrogen adsorption occurred during the pre-sulfidation process of Fe₂O₃ precursors.（2）This work also adopted methods of chemical experiments to further prove hydrogen adsorption and dehydrogenation behavior of Fe_1-xS catalysts in both an anthracene system and a none anthracene system.The results showed that H₂ was produced by dehydrogenation in both two systems,and there were two transforming ways for hydrogen element on the Fe_1-xS catalysts in the anthracene system,which were to generate H₂ and make anthracene hydrogenation;with temperature increasing,the total amount of dehydrogenation gradually increased,which indicated high temperature was beneficial to dehydrogenation;the total amount of dehydrogenation also increased first and then unchanged with increasing time.The maximum total amount of dehydrogenation of Fe_1-xS catalyst was 2.37 mmol H/g at 420℃for1 h in the anthracene system.Besides,the solvent could promote dehydrogenation in both two systems.Lastly,thermodynamic parameters of dehydrogenation reactions in the anthracene system were calculated and the equilibrium constants at different temperatures were determined.Of course,dehydrogenation behavior of Fe_1-xS catalysts also had differences in the two systems.A total amount of dehydrogenation in the anthracene system was greater than that in none anthracene system at every temperature,and the temperature had a greater influence on dehydrogenation in the anthracene system.（3）The re-hydrogenation behaviors of Fe_1-xS catalysts in only H₂system and H₂+tetralin systems were both investigated.The results showed that Fe_1-xS catalysts could be re-hydrogenated in both systems.But with increase of temperature,the amount of hydrogenation decreased gradually,indicating that a lower temperature was favorable to re-hydrogenation reactions of the catalysts.The amount of hydrogenation increased first and then stabilized with increasing time.Besides,with an initial hydrogen pressure increasing,the amount of hydrogenation of catalysts increased first and then slowed down in both systems.The maximum amount of re-hydrogenation of Fe_1-xS catalyst was 4.20 mmol H/g at 360℃for 2 h in H₂ system.Fe_1-xS catalysts also had some differences in hydrogenation reaction between the two systems.At 380℃and below,the amount of re-hydrogenation of catalysts was larger in H₂ system,but at 400℃and above,the amount of re-hydrogenation of that in H₂+tetralin system was larger.The influence of temperature on re-hydrogenation reaction of Fe_1-xS catalysts in H₂ system was more significant.