Study On The Novel Catalysts For Carbon Disulfide Removal

A large amount of waste gases containing carbon disulfide?CS₂?are emitted during the production of viscose fiber.This kind of waste gases damages human health and affects the quality of the surrounding environment because they can produce acid gas by oxidation or hydrolysis reaction in the atmosphere,form secondary aerosols with other pollutants,and aggravate air pollution.The efficient removal of CS₂ from exhaust gases at low temperatures is a difficult and critical issue of viscose fiber industry.Catalytic hydrolysis is able to achieve low-temperature removal of CS₂,but it can not simultaneously remove hydrolysate H₂S,so the waste gases are not completely purified.The low-temperature adsorption-catalytic hydrolysis process has the characteristics of fast removal,high efficiency and synergistic purification of products.The core of this method focuses on the development of low-temperature catalysts.In this thesis,a series of metal-supported catalysts were prepared by ultrasonic-assisted impregnation method for the removal of CS₂ at low temperatures.The study on catalytic hydrolysis process and influencing factors of CS₂removal by Cu-supported catalyst was performed in this thesis.The effects of carriers,calcination conditions,ultrasonic time,metal loading and alkali impregnation on the removal efficiency of CS₂ were systematically investigated.At the same time,the effects of CS₂ inlet concentration,water vapor content,space velocity and reaction temperature on the removal of CS₂ from gases were systematically investigated.The catalysts were characterized by XRD,BET,XPS and CO₂-TPD.It was found that under the conditions of 30°C and 5%water vapor content,the removal efficiency of CS₂ by 6%CuO supported on activated carbon was the optimal choice,and the maintenance time was 216 min for the removal rate over 90%.The catalyst possessed large specific surface area and a large number of alkaline sites contributing to the hydrolysis and conversion of CS₂.The reaction mechanism of CS₂ removal at low temperatures was that CuO catalyzed the conversion of CS₂ to H₂S.The produced H₂S was partially oxidized by CuO to sulfate,sulfite and sulfur deposited in the catalyst,while the rest was adsorbed on the surface of the catalyst.Simultaneously,CuO was reduced during the reaction,and the number of active sites decreased,resulting in catalyst deactivation.The rapid regeneration of CuO catalyst was achieved within 90 min by programmed heating to350°C in nitrogen,and the performance was stable after ten cycle tests.The catalytic hydrolysis of CS₂ by multi-component catalysts doped with Mg,Zr,Mo,Ni and Zn and the influencing factors were also studied.It was found that the deactivation resistance performance of Cu/Mg bimetallic catalyst which were prepared by step impregnation and calcination method,was much better than that of single metallic CuO catalyst.When the MgO loading was 1%and the molar ratio of Cu and Ni was 1:1?the loading was 6%?,the catalyst possessed the optimal removal property of CS₂.The maintenance time of removal rate over 90%was 228 min with the condition of 3%water vapor content at 20°C.The addition of Mg improved the quantity of basic sites,and thus enhanced the deactivation performance of the catalyst.The catalyst had a long-lifetime of 300 min?with CS₂ removal rate>90%?,and good recycling performance.The capacity of Cu-Ni/Mg trimetallic catalyst for CS₂ removal remained stable after five times of regeneration tests.