Study On Simultaneous Catalytic Hydrolysis Of HCN,COS,CS₂ And Reaction Mechanism Over Activated Carbon Based Catalyst

Ore-smelting furnace tail gas contains a large amount of CO that can be used as high quality chemical raw material gas.However,the tail gas contains traces of cyanide and sulfur-containing impurities,such as HCN(45?130 mg/m³),COS(700?1000 mg/m³)and CS₂(20?80 mg/m³)et al.At present,the resource utilization of ore-smelting furnace tail gas has been listed as a national strategy and priority development theme by our country.Due to the complex impurities in the ore-smelting furnace tail gas,it is difficult to oxidize under low temperature and micro-oxygen conditions,and the lack of multi-impurity purification theory and special catalysts makes it difficult to purify ore-smelting furnace tail gas deeply.The water vapor contained in the reducing furnace gas was used to hydrolyze HCN,COS and CS₂,and converted them into easy-to-handle substances.Among them,HCN was hydrolyzed to generate NH₃ and CO,and COS/CS₂ was hydrolyzed to generate H₂S and CO₂.Based on the previous research foundation of our research group,this paper continued to explore the performance of main activated carbon catalysts(biochar and coal-based activated carbon)to remove HCN,COS and CS₂.At the same time,the theoretical calculation method was used to explore the reaction mechanism,which provided a theoretical basis for the research and application of the catalytic hydrolysis of HCN,CS₂ and COS and the resource utilization of ore-smelting furnace tail gas.The specific research content and conclusions were as follows:(1)Corn stalks were used as raw materials to prepare activated carbon,the effects of different types of activators,carbonization temperature,activator flow rate and activation temperature on the simultaneous removal of HCN,COS and CS₂ by corn straw activated carbon were studied.Studies have shown that under the optimal preparation conditions(activator was CO₂,carbonization temperature was 600?,gas flow rate was50 m L/min,activation temperature was 700?),CO₂ activated corn straw activated carbon exhibited excellent removal performance of HCN,COS and CS₂.Comparing the previous research results of our group,the removal effects of COS and CS₂ have been improved,and can synergistically remove HCN.(2)Using microwave coal-based activated carbon as the raw material in this study,the microwave coal-based carbon catalyst was prepared by sol-gel method supporting metal components.The effects of different metal types,precursors,metal oxide content and calcination temperature on the simultaneous removal of HCN,COS and CS₂ were studied.The results showed that under the optimal preparation conditions(metal composition was Al,precursor was Al(NO₃)₃,metal content was 3%,and calcination temperature was 400?),microwave coal-based catalysts can effectively purify HCN,COS and CS₂ synergistically.Comparing the previous research results of our group,the removal effects of COS and CS₂ have been improved,and can synergistically remove HCN.(3)The effects of different reaction conditions on the simultaneous removal of HCN,CS₂ and COS over microwave coal-based catalysts were studied.It was found that higher reaction temperature could promote the catalytic process and lead to deactivation;lower reaction temperature does not reach the activation temperature of the active components,resulting in low removal rate.Higher relative humidity could inhibit the distribution of HCN,COS and CS₂ hydrolysis centers on the catalyst surface;lower relative humidity cannot provide enough hydrolysis groups.The catalyst regeneration methods were studied,studies have found that nitrogen purging has the best catalytic activity recovery ability.When the nitrogen purge temperature was too low,most of the sulfate has not yet decomposed under low temperature conditions;when the nitrogen purge temperature was too high,Al₂O₃ will react with C to cause the active component to decompose under high temperature and oxygen-free conditions,decrease in consumption and catalytic performance.(4)With theoretical calculations method,using graphene to simulate activated carbon support,the competitive adsorption relationship of HCN,COS,CS₂ and H₂O was studied.Studies have shown that when H₂O was present,it could promote the adsorption of HCN,COS,and CS₂ on the surface of the carrier.H₂O adsorbed preferentially and then formed a stable system structure with HCN,COS and CS₂ respectively.The exploration of the dissociation configuration of H₂O molecule found that the dissociation of H₂O occured preferentially when HCN,COS,and CS₂ existed with H₂O.(5)The catalytic hydrolysis process of HCN,COS and CS₂ on the catalytic hydrolysis process of HCN,COS and CS₂ on active component Al₂O₃(110)surface was explained in detail by theoretical calculation method.During the catalytic hydrolysis of HCN,the C atom took the O in the Al₂O₃ molecule to form a C=O bond,and the formation of the H-N bond in the product NH₃ molecule were the control steps for the catalytic hydrolysis of HCN on the Al₂O₃(110)surface.COS took the O from H₂O to form a bond C=O in the process of hydrolysis,and the cleavage process of the C=S bond was a key step.The C in the hydrolysis process of CS₂ captures O in Al₂O₃ to form C=O bond,and the formation process of H=S bond were control steps.