| As a common odorous,toxic and corrosive gas,hydrogen sulfide generally exists in industrial gases such as natural gas,coal gasification gas,and so on.Hydrogen sulfide has been a huge obstacle to industrial production.Moreover,the leakage of hydrogen sulfide is a heavy threat to human being.Therefore,the removal of H2S from sulfur-bearing gas has been an important topic for researchers.To remove H2S,a large number of processes have been developed.The desulfurization processes could be divided into two major forms,wet method and dry method.Environmentally friendly materials,such as molecular sieve,heteropoly compound?HPC?and ionic liquid?IL?,show perfect desulfurization performance due to their unique properties.In this work,a series of green desulfurization systems have been developed.The desulfurizers as well as desulfurization products were characterized by FT-IR,XRD,elemental analysis,XPS,SEM,EDA,TGA-DSC and so on.The influence factors were studied in detail.The content of this thesis contains the following seven parts:?)Polyethylene polyamine was loade on the surface of clay powder modified by calcination and hydrochloric acid treatment.The adsorbent was characterized by Fourier transform infrared?FT-IR?,scanning electron microscopy?SEM?,Specific surface test?BET?,X-ray fluorescence?XRF?and X-ray diffraction?XRD?.The results of XRD and XRF showed that the major components of the adsorbent were attapulgite,montmorillonoid and quartz.FT-IR spectra and SEM images demonstrated that the polyethylene polyamine had been loaded on the surface of the clay.The H2S removal performance of the adsorbent was investigated by dynamic H2S adsorption experiment.The results showed that calcination treatment at 400?was the best modification method for H2S removal.The water vapour pretreatment and relatively low adsorption temperature and is more conductive to H2S removal using adsorbent.The H2S removal rate could reach 100%.The optimal loading amount of polyethylene polyamine is 33.3 wt%.The results of FT-IR and BET before and after the adsorption of H2S showed that H2S molecular is adsorbed mainly via chemical absorption of amino.The regeneration performance of adsorbent showed that the adsorbent can be recycled for several times,and no significant decline of desulfurization performance could be observed.?)The 4A molecular sieve zeolite was synthesized from clay?industrial building materials?in different conditions and was applied to H2S removal for the first time.The prepared molecular siecve was characterized by SEM,XRD,FT-IR and N2 adsorption/desorption.The results of XRD and SEM demonstrated that the 4A molecular sieve had been synthesized successfully.The influence of the synthesis condition and adsorption temperature on the desulfurization performance of adsorbent was investigated through dynamic H2S adsorption experiment.The H2S adsorption results have showed that the optimal synthesis conditions are as follows:n?SiO2?/n?Al2O3?= 1.5,n?Na2O?/n?SiO2?= 1.5,n?H2O?/n?Na2O?= 30,crystallization temperature and crystallization time is 90 ?,4h,respectively.The optimal adsorption temperature is identified as 50 ?.The breakthrough and saturation sulfur adsorption capacities of 4A molecular sieve zeolite synthesized under optimum conditions are 8.36 and 12.4 mg/g-sorbent,respectively,and the H2S removal efficiency of the adsorbent is nearly 100%.The regeneration performance of sorbent was investigated and a significant decline of the H2S adsorption capacity of regenerated sorbent was observed.The results of XRD,SEM and FT-IR demonstrated that this phenomenon was caused by the damage of particle structure taking place in the regeneration process.However,during the next sorption-desorption cycles,no significant decline in H2S sorption capacity can be observed.In order to investigate the adsorption kinetics of H2S on 4A zeolites,four equations pseudo-first-order,pseudo-second-order,intra-particle diffusion and Bangham models have been tested.The adsorption kinetics nonlinear fitting results demonstrated that the adsorption of H2S on 4A molecular sieve zeolite follows Bingham model,which demonstrate that the adsorption kinetics of are limited by the pore diffusion.?)Seven hydroxyl ammonium ionic liquids?ILs?were prepared by neutralization reaction:ethanolamine acetate?MEA-A?,ethanolamine formate?MEA-F?,ethanolamine propionate?MEA-P?,ethanolamine lactate?MEA-L?,diethanolamine acetate?DEA-A?,triethanolamine acetate?TEA-A?and N-methyl diethanolamine acetate?MDEA-A?.The desulfurization performances were investigated through dynamic H2S adsorption experiment.The pure hydroxyl ammonium ILs showed weak physical and chemical absorption for H2S,and the H2S removal efficiencies were all decreased to below 10%within 15 min.To enhance the desulfurization performance of ILs,hydramine was dissolved in ionic liquids with corresponding cations.The solution of MEA/MEA-L showed the best desulfurization performance,and the H2S removal efficiency can keep nearly 100%for 2 h.The results showed that the lower temperature and H2S concentration were in favor of H2S removal.The results of mathematical calculation demonstrated that the absorption of H2S using MEA/MEA-L solution is a pseudo first order reaction.The saturated sulfur capacity of MEA/MEA-L solution is 17.0 mg-H2S/g-absorbent at 25?.The result of absorbent regeneration experiment showed that MEA/MEA-L solution can be regenerated perfectly.The FT-IR spectra of absorbents demonstrated that the ionic liquids were synthesized successfully,and single hydroxyl ammonium ILs did not react with H2S molecular.Besides,the H2S removal was achieved by amino group existed in hydramine.Therefore,the reactions of MEA/MEA-L solution with H2S molecule can be expressed as follows:HOCH2CH2NH2+H2S???HOCH2NH3+HS Furthermore,compared with aqueous solution of hydramine,the MEA/MEA-L solution has advantages for avoiding mass loss and foaming.?)A new process for H2S removal using the solution of peroxo heteropoly acid has been developed.The solutions of peroxo heteropoly acid were prepared by mixing heteropoly acid and H2O2 with a molar ratio of 1:24.The desulfurization performances of the solutions were investigated through dynamic H2S adsorption experiment.The results showed that the solution of peroxo phosphomolybdic acid can remove H2S perfectly.The influence of temperature,concentrations of H2S as well as peroxo phosphomolybdic acid on H2S removal was investigated.According to the results,a higher absorbent concentration,lower H2S concentration,slightly excessive H2O2 as well as relatively low absorption temperature are conductive to H2S removal.According to the experiment,the H2S removal efficiency could achieve 100%for 10 h by using two-stage absorption with an absorbent concentration of 0.02 mol/L,proving the solution of peroxo phosphomolybdic acid was an excellent H2S adsorbent.The absorbent showed a perfect regeneration performance,and could be reactivated simply by adding a few drops of 30%H2O2 solution.The change of oxidation-reduction potential of the absorbent was measured.The oxidation-reduction potential decreased slowly with the continuous absorption process as the consumption of peroxo species,and then recovered rapidly after the addition of H2O2 because of the regeneration of peroxo phosphomolybdic acid.The X-ray photoelectron?XPS?spectra showed that the H2S was oxidized to SO42-finally.?)Five peroxo heteropoly compounds?PHPC?,[?C4H9?4N]3{PO4[MoO?O2?2]4},[CH3?CH2?11N?CH3?3]3{PO4[MoO?O2?2]4},[CH3?CH2?13N?CH3?3]3{PO4[MoO?O2?2]4},[CH3?CH2?15N?CH3?3]3{PO4[MoO?O2?2]4} and[CH3?CH2?17N?CH3?3]3{PO4[MoO?O2?2]4},were synthesized and dissolved in four ionic liquids,1-N-butyl-3-methylimidazolium bis?trifluoromethanesulfonyl?imide?[BmimT][Tf2N]?,1-N-butyl-3-methylimidazolium hexafluorophosphate?[Bmim][PF6]?,1-N-butyl-3-methylimidazolium tetrafluoroborate?[Bmim][BF4]?and 1-N-butyl-3-methylimidazolium bicarbonate?[Bmim][HCO3]?,to remove H2S.The results of FT-IR spectrum,Raman spectrum,elemental analysis,Nuclear Magnetic Resonance?NMR?and XRD proved that the PHPC has been synthesized successfully.Besides,the PHPC and IL were characterized by thermogravimetry and differential thermal analysis?TGA-DSC?.The results showed that[CH3?CH2?isN?CH3?3]3{PO4[MoO?O2?2]4} begins to decompose at around 150?,and[Bmim][HCO3]is stable in the experimental temperature.The influences of ILs and cations of PHPC on H2S removal were investigated by dynamic H2S absorption experiment.The desulfurization results showed that H2S removal capacity decreased in the sequence:[Bmim][HCO3]>[Bmim][BF4]>[Bmim][Tf2N]>[Bmim][PF6],and increased in the sequence of[?C4H9?4N]+<[CH3?CH2?11N?CH3?3]+<[CH3?CH2?13N?CH3?3]+<[CH3?CH2?15N?CH3?3]+ ?[CH3?CH2?17N?CH3?3]+.Hence,[CH3?CH2?15N?CH3?3]3{P04[MoO?O2?2]4} dissolved in[Bmim][HC03]showed the best H2S removal performance.Condition optimization experiments showed that a low H2S concentration and high PHPC concentration is beneficial to H2S removal.The optimal absorption temperature is identified as 95?.The H2S removal efficiency of absorbent could reach nearly 100%for 2 h under the optimal conditions.According to the regeneration experiment,after the first regeneration process,the H2S removal efficiency of absorbent decreased to nearly 85%when the absorption experiment lasted for 1 h,and no obvious decrease was observed after several cycles.Furthermore,the desulfurization product was proved to be sulfur.?)A series of substituted heteropoly compounds?HPCs?,Bmim3PW12-XMoxO40?x = 0,1,3,6,9,12??abbreviated as PW12-xMox?and Bmim3+xPMo12-xVxO40?x = 0,1,2,3,6??abbreviated as PMo12-xVx?,were synthesized and dissolved into ionic liquid 1-N-butyl-3-methylimidazolium chloride?BmimCl?to remove H2S at 200?.The absorbents and desulfurization products were characterized by FT-IR spectra,elemental analysis,TGA-DSC and XPS.The results of FT-IR spectra and elemental analysis demonstrated that the HPCs were synthesized successfully.The results of TGA-DSC showed that the HPCs and BmimCl are stable at the experimental temperature.According to the dynamic H2S absorption results,the desulfurization ability of Mo-V doped HPC is far stronger than that of W-Mo doped HPC,demonstrating that V and Mo atoms in HPC are more conductive to H2S removal compared with W atom.For solutions of PMo12-xVx/BmimCl,the desulfurization efficiencies of five solutions were all above 90%within 6 h,among which,the solution of PMo10V2/BmimCl has the strongest desulfurization capacity.The regeneration experiment showed that all HPC/IL solution can be regenerated easily.The result of multiple regeneration experiment showed that the solution of PMo10V2/BmimCl is an efficient renewable high-temperature desulfurizer.Besides,the lower H2S concentration and higher HPC concentration are in favor of H2S removal.Interestingly,there is liner correlation between the H2S breakthrough removal amount and the PMo10V2 concentration,demonstrating that the H2S removal is mainly achieved by HPC,and the IL plays a role of reaction medium.To investigate the desulfurization mechanism of PMo10V2/BmimCl solution,the samples before and after regeneration were characterized by XPS and FT-IR analyses.The results showed that the oxygen in heteropoly anion could be replaced by S2-,which greatly improved the sulfur capacity of desulfurizer.Furthermore,the final desulfurization product is proved to be S.This phenomenon was never found before in liquid phase.The equation of absorption reaction could be expressed as:PMo10V2O40+H2S?PM10V2O40-nSn+H2O?1 ? n ? 40?;the equation of regeneration reaction could be expressed as:PMo10V2O40-nSn+O2?PMo10V2O4+S.The response equation of the whole absorption-regeneration reaction should be expressed as:2H2S+O2?HPC/IL2H2O+2S.?)The macro-kinetic characteristics of hydrogen sulfide absorption of three systems for H2S removal,[Bmim]3PMo12O40/BmimCl,the aqueous solution of peroxo phosphomolybdic acid and the aqueous solution of CuH2PMo11VO40,have been investigated by a double stirred gas-liquid reaction cell.The gas and liquid phase mass transfer coefficients were measured,and the macro reaction orders and activation energies were identified.The gas and liquid phase mass transfer coefficients of H2S in the reaction cell at 25? were 1.46×10-10kmol/?m2·s·Pa?and 3.26×10-5 m/s,respectively.For[Bmim]3PMo12O40/BmimCl,the reaction orders to[Bmim]3PMo12O40 and H2S were 0.099 and 1.120,respectively.The activation energy of the overall reaction was identified as 8.84 KJ/mol,and the macro-kinetics equation could be expressed as:NH2S=6.6×10-2·[exp?-1064/T?]-CH2S1.120·C[Bmim]3PMo12O400.099.For the aqueous solution of peroxo phosphomolybdic,the reaction order to peroxo phosphomolybdic was 0.131,and 0.252 to H2S.The activation energy of the overall reaction was identified as 6.57 KJ/mol,and the macro-kinetics equation could be expressed as:NH2S=2.68×10-6.[exp?-790/T?]·CH2S0.252.CPHPMo0.131.For the aqueous solution of CuH2PMo11VO40,the reaction order to CuH2PM011VO40 was 0.131,and 0.252 to H2S.The activation energy of the overall reaction was identified as-5.04 KJ/mol,and the macro-kinetics equation could be expressed as:NH2S=1.02×10-6·[exp?607/T?·CH2S0.510·CCuH2PMo11VO400.431. |
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