Coupling Catalytic Hydrolysis And Oxidation Of HCN Over HZSM-5 Modified By Metal(Fe,Cu) Oxides

Hydrogen cyanide is a highly flammable and toxic gas.Yellow phosphorus tail gas contains a large amount of harmful gases including hydrogen cyanide.The presence of hydrogen cyanide seriously restricts the recycling of industrial waste gas.On the basis of summarizing the existing research on hydrogen cyanide purification at home and abroad,this paper studies the catalytic hydrolysis and oxidation of hydrogen cyanide by the catalytic hydrolysis of modified HZSM-5.In this work,Fe-ZSM-5,Cu-ZSM-5 and Fe-Cu/ZSM-5 catalysts prepared by equal volume impregnation method were applied to the coupling catalytic hydrolysis oxidationreaction of HCN.First,the catalytic activity of single transition metal and double transition metal modified HZSM-5 was investigated.The experimental results show that the introduction of transition metals significantly improves the conversion efficiency and N₂ selectivity of HCN.Compared with HZSM-5,Fe-ZSM-5 and Cu-ZSM-5,Fe-Cu/ZSM-5 has the best catalytic conversion activity of HCN.When the reaction temperature is more than 250?,the conversion of HCN is more than99%,and N₂ selectivity reaches the maximum value of 80%at this temperature.Besides,the reaction temperature,the SiO₂/Al₂O₃ and the type of active components are considered as the key factors that affect the catalytic activity and N2selectivity of HCN.In order to investigate the effect of different Fe-Cu loads on the coupling catalytic hydrolysis and oxidation of HCN,four kinds of catalysts,Fe₂-Cu₈/ZSM-5,Fe₄-Cu₆/ZSM-5,Fe₆-Cu₄/ZSM-5,Fe₈-Cu₂/ZSM-5,were prepared and applied to the catalytic conversion of HCN.The results showed that with the increase of Cu loading,the conversion and N₂ selectivity of HCN at low temperature were all improved.Among them,Fe₂-Cu₈/ZSM-5 has the best catalytic activity for HCN conversion.At 200?,the conversion rate of HCN is 99%,and the selectivity of nitrogen is 83%.The catalysts were characterized by X ray diffraction?XRD?,N₂ desorption?BET?,X ray photoelectron spectroscopy?XPS?,Fu Liye infrared?FT-IR?,temperature programmed reduction?H₂-TPR?and temperature programmed desorption?TPD?.The crystal structure,pore structure and morphology of the catalyst were studied,as well as the possible catalytic reaction mechanism.The significant improvement of the activity of the catalyst may be due to the creation of highly dispersed iron and copper composites on the surface of the HZSM-5 support,which act as active site in the coupling catalytic hydrolysis oxidation of HCN.H₂-TPR,O1s spectra and activity tests showed that the adsorption of oxygen promoted the catalytic reduction of HCN.The high selectivity of N₂ in the reaction products is probably due to the formation of Fe-Cu nanocomposites on the catalyst surface,which plays an important role in NH₃-SCR.The reaction mechanism of HCN catalytic reduction can be deduced from the above experiments and characterization results,the interaction between catalytic hydrolysis and catalytic oxidation of HCN promoted the transformation of HCN.NH₃ and CO produced by hydrolysis of HCN react with O₂ to form N₂,NO_x and CO₂,When NH₃ and NO_x exist simultaneously in the reaction system,the two can also generate NH₃-SCR reaction to generate N₂,so that HCN is completely transformed.