Study On New Green Desulfurization System Of Substituted Heteropoly Compounds

Hydrogen sulfide(H2S)is a colorless,malodorous,flammable and highly toxic gas.It is a common pollutant in oil and gas production/processing,wastewater treatment plants,fossil fuel combustion,and landfill gases.Long-term low concentration or short-term high concentration exposure to H2S will cause serious harm to human being.The existence of H2S in industry will cause production waste.The H2S discharged into the atmosphere will form sulfur dioxide,which will cause environmental pollution such as acid rain.The green removal of H2S and the recovery of sulfur resources are topics that researchers have been paying close attention to,and a series of increasingly mature desulfurization processes have emerged.The wet method of chemical oxidation has gradually become the first choice for industrial desulfurization because of its large sulfur capacity and easy regeneration.Heteropoly compound and their salts have excellent redox capacity and stable structure,becoming the key factor of redox in wet method of chemical oxidation.In this paper,three different structures of substituted heteropoly compound desulfurization systems were created,which were Keggin heteropolytungstate substituted by transition metals,Keggin heteropolymolybdate substituted by transition metals and Dawson heteropolymolybdate substituted by rare earth metals.H2S dynamic absorption experiment is used to investigate the desulfurization capacity.Find the best desulfurization environment by condition optimization experiment.Characterize heteropoly compounds and desulfurization products and discuss desulfurization mechanisms.In the first system of this paper,Keggin-type heteropolyphosphorus tungstate substituted with transition metals(Fe,Co,Ni)was prepared by alkaline degradation method,and a desulfurization solution was prepared for hydrogen sulfide removal experiment.The structure of the prepared heteropolyphosphorus tungstate was analyzed by Fourier infrared spectroscopy(FT-IR).The comprehensive comparison of hydrogen sulfide absorption and regeneration experiment results shows that the transition metal iron Fe substitution formed phosphotungstic acid desulfurization effect is better,the optimal temperature for the test is 25?,the con centration of phosphotungstic acid desulfurization agent is higher,and the concentration of hydrogen sulfide is lower Facilitate the reaction.XPS characterization analysis results:the desulfurization products are elemental S and SO42-.In the second system of this paper,Keggin-type heteropoly compounds substituted by transition metals(Co,Mn,Ni and Zn),as well.as H3PMo12O40 and H3PMo11O39 were prepared by alkaline degradation.The desulfurizer is prepared by dissolving th e prepared heteropoly compoun d in water.The successful substitution of transition metals for heteropoly compounds was obtained from the results of infrared spectroscopy(FT-IR),elemental analysis,and scann ing electron microscopy(SEM).The desulfurization capacity was measured by the dynamic absorption test of H2S,and the air was blown off at 95? for 6 hours to complete the regeneration experiment.According to the comprehensive experimental results,the heteropoly compound substituted by the transition metal cobalt(Co)shows the best desulfurization ability.Under the optim al conditions,the H2S removal rate can reach more than 90%and be maintained for 400 minutes.When the solvent temperature is 25? and the pH is 5,the desulfurizer has the strongest H2S absorption capacity.Within a certain range,the desulfurization capacity is proportional to the concentration of heteropoly compounds and inversely proportional to the concentration of H2S.XPS analysis results prove that the final desulfurization conversion productw are S and SO42-,and the cobalt substituted heteropoly compounds plays a catalytic role in redox.In the third system of this paper,the Dawson-type heteropoly compounds K17[Ln(P2Mo17O61)2](Ln=Pr3+,Gd3+,Sm3+and Eu3+)were prepared by ether extraction.Its aqueous solution is used to dynamically remove H2S.FT-IR is used to analyze the successful substitution synthesis of heteropoly compounds.The regeneration experiment utilizes the electrochemical regeneration method.According to the results of selective experiments on rare earth species,the praseodymium(Pr)doped heteropoly compound K17[Pr(P2Mo17O61)2](PrP2Mo17)has the best desulfurization ability.Selective experimental results on the reaction condition factors indicate that room temperature(25?)is most conducive to the reaction.Within a certain limit,the higher the concentration of PrP2MO17,the lower the concentration of H2S gas,and the higher the removal rate of H2S.Since the pH of the solution is unstable during the reaction,this paper also explores the stabilizing effect of the pH buffer solution.Comparing the experimental results of the two adjustment methods,it is found that the desulfurization system with pH buffer solution as the solvent has a higher removal rate of the H2S,and the pH change range of the solution before and after absorption is smaller.Therefore,select the buffer solution with pH=6.8 as the optimal solvent acidity.XPS spectrum was used to analyze the mechanism of PrP2Mo17 desulfurization.Absorption process:H2S is oxidized into elemental S and SO42-,and the main role is the molybdenum(Mo)atom in PrP2Mo17,which changes from Mo(+?)to Mo(+?),Pr(+?)to Pr(+?).Electrochemical regeneration process all the elemental S is converted to SO42-,Mo(+?)is restored to Mo(+VI),and Pr(+?)is restored to Pr(+?).This process proves that PrP2Mo17 was successfully regenerated.In summary,the heteropoly compound PrP2Mo17 plays a catalytic role with redox in the whole absorption-regeneration process.