Study On Suitable Catalytic Systems For The Preparation Of Ethyl Mercaptan Via Hydrogen Sulfide And Ethylene

Ethyl mercaptan is an important chemical intermediate for the production of insecticides,herbicides and pharmaceuticals.The main process for the preparation of ethyl mercaptan on industrial scale is via the addition of hydrogen sulfide to ethylene,and it is a green synthesis route with 100% atom availability.In this study,the synthesis of ethyl mercaptan was studied over a series of transition metal sulfides and different pore structure and acidity modified MFI-type?HZSM-5?zeolites.The physicochemical properties of the catalysts were characterized by combination of XRD,N2 adsorption,SEM,XPS,H₂-TPR,MAS NMR and NH₃-TPD,etc.In addition,the catalytic performance and stability was tested in a home-made fixed bed reactor.In the Co-Mo-S/?-Al₂O₃ catalytic system,the structure of active phase mainly located in the borders and corners of MoS2 slabs.The addition of proper content of Co could improve the dispersibility and educibility of Mo species,thus promote the formation of more active phase.Catalytic activity was strongly influenced by Co/Mo loadings and preparation conditions.The obtained results demonstrated that the sample of C6M6 A with 6 wt% Co and Mo loadings exhibited the best activity and stability.Under the evaluation condition of 280 ?,1.6 MPa,GHSV of ethylene of 280 h-1,and molar ratio of hydrogen sul fide to ethylene of 3:1,the conversion of ethylene was 94.8% and the selectivity of ethyl mercaptan was 83.6%.The obtained results also revealed that alkaline treatment led to the development of considerable mesoporosity without destruction of the intrinsic zeolite properties,which could facilitate mass transfer and suppress the side reactions.Meanwhile,the mesopores made some acid sites originally in the micropores exposing to the external surface of zeolites,thus preventing the catalyst deactivation and extending catalyst lifetime on the order of several hours.Variation of treatment time enables tailoring of the mesopore volume and modifying of the acidity.The sample that treated in 0.2 mol/L NaOH solution showed the best performance,with ethylene conversion of 89.2% and ethyl mercaptan selectivity of 93.8%.Introduction of phosphorus in HZSM-5 zeolite leaded to the reduction of strong aicd strength and concentration,thus restrict the formation of coke and condensation products.The catalyst lifetime of phosphorus-modified HZSM-5 with P/Al = 1.0 increased nearly three-fold.We can obtain a deep understanding about the synthesis of ethyl mercaptan and the structure of active phase through this study.In order to aid the development of applicable industrial catalysts for ethyl mercaptan production,there has been a strong emphasis on establishing fundamental relationships between the mechanism of reaction and the catalytic performance.