Synthesis Of MoS₂ By Solvothermal And Its Hydrogenation Performance For Coal Tar Model Compounds

Recently,molybdenum disulfide(MoS₂),as a kind of inorganic disulfide,has attracted more and more attention due to its layered structure similar to two-dimensional layered compound graphene and its strong activity in the field of catalytic hydrodesulfurization.Because of its special S-Mo-S layered structure,different reaction conditions in the synthesis process will lead to large differences in the structure,morphology,size,configuration and active sites of the prepared MoS₂,and the synthesized MoS₂ is easy to agglomerate.Based on these problems,in this paper,MoS₂was synthesized by solvothermal synthesis using organic solvent(non-aqueous)as reaction system by searching and controlling the reaction conditions,and its catalytic performance for hydrodesulfurization of sulfur-containing polycyclic compound-dibenzothiophene(DBT)in a slurry bed was studied.The main research contents and results are as follows:1.The mixed 1T/2H-MoS₂ with few layers and 47.8%of 1T phase was successfully synthesized from ammonium heptamolybdate tetrahydrate and thiourea by glycol-water mixed solvothermal method.The effects of p H value,molar concentration of molybdenum,Mo/S and volume ratio of glycol-water were studied.The obtained MoS₂ was characterized by SEM,XRD,Raman,XPS and BET.The results showed that:(1)with the increase of p H value,molybdate concentration,the conversion of synthetic MoS₂ catalyst for DBT hydrodesulfurization first increases and then decreases and the conversion reaches the maximum when the concentration of 12 M hydrochloric acid is 2m L and the molybdate concentration is 0.02 M;(2)With the decrease of Mo/S,the conversion of DBT increased first and then decreased,and reached the maximum when Mo/S ratio was 1:4;(3)with the increase of ethylene glycol volume fraction,the conversion of DBT hydrodesulfurization basically showed a trend from large to small,and the conversion of DBT hydrodesulfurization catalyzed by MoS₂synthesized at 10%ethylene glycol volume fraction reached the maximum.The optimum conditions for the synthesis of MoS₂ were determined as follows:12 M hydrochloric acid is 2 m L,molybdate molar concentration is 0.02 M,molar ratio of Mo/S is 1:4 and volume fraction of ethylene glycol is 10%.It was found that the addition of ethylene glycol could inhibit the catalytic activity of MoS₂.2.MoS₂ with few layers and 1T phase up to 48.0%was successfully synthesized by ethanol-water mixed solvothermal method using ammonium heptamolybdate tetrahydrate and thiourea as Mo and S sources respectively.The morphology of MoS₂showed a layered structure with more plane exposure and zigzag edges.The effects of Mo/S,standing time,p H value and volume ratio of ethanol-water were studied.The synthesized MoS₂ was characterized by SEM,EDS,TEM,XRD,FT-IR,Raman,XPS and BET.The results show that:(1)with the decrease of Mo/S and the increase of standing time,the conversion of DBT hydrodesulfurization over synthetic MoS₂ catalyst decreases gradually,and reaches the maximum when Mo/S ratio is 1:4 and standing time is 0 h;(2)with the increase of p H value,the conversion rate decreased,and reached the maximum at p H 1.40;(3)with the increase of ethanol volume fraction,the conversion first increased and then decreased,and reached the maximum at 50%ethanol volume fraction.Finally,the optimal conditions for the synthesis of MoS₂ were determined as follows:molar ratio of Mo/S is 1:4,standing time is 0 h,p H value is 1.40and volume fraction of ethanol is 50%.It was found that the thickness of nanosheets for the synthesis of MoS₂ had a certain correlation with Hansen solubility parameters.3.MoS₂ with 1T phase of 51.8%was successfully prepared by xylene-water mixed extraction solvent method with ammonium heptamolybdate tetrahydrate as molybdenum source and thiourea as sulfur source.The effects of p H value,standing time,molar concentration of molybdenum and Mo/S were studied.The synthesized MoS₂ was characterized by SEM,XRD,Raman,XPS and BET.The results showed that:(1)with the increase of p H value and standing time,the conversion of DBT hydrodesulfurization catalyzed by MoS₂ increased at first and then decreased;and reached the maximum when the concentration of 12 M hydrochloric acid was 0.4 m L and the standing time was 36 h;(2)with the increase of molybdate molar concentration and the decrease of Mo/S ratio,the conversion first decreases and then increases,and reaches the maximum when molybdate molar concentration is 0.1 M and Mo/S ratio is1:1.Finally,the optimal conditions for the synthesis of MoS₂ were determined as follows:the amount of 12 M hydrochloric acid is 0.4 m L,the standing time is 36 h,the molar concentration of molybdenum is 0.1 M and molar ratio of Mo/S is 1:1.It was found that the MoS₂ synthesized by this method showed better performance than that synthesized in pure water and commercial.