The Research Of Simultaneous Removal Of H2_S And PH₃ By Modified Activated Carbon Fiber In The Low-temperature And Micro-Oxygen Condition

Reductive industrial furnaces tail gas?such as yellow phosphorus tail gas and closed calcium carbide furnace exhaust?contains various exhaust gases,which including hydrogen sulfide?H₂S?and phosphine?PH₃?.These impurities have negative influence to the recycle of resource-type gas such as CO from the exhausted gas.Furthermore,hydrogen sulfide and phosphine may harm the environment and human health if they were discharged into environment directly without treatment.Therefore,it is particularly important to remove H₂S and PH₃ from industrial furnace tail gas.Activated carbon usually used in the dry catalytic oxidation method for the removal of H₂S and PH₃.However,activated carbon method has a low adsorption capacity and the purification mechanism is not clear yet.To solve this problem,activated carbon fiber?ACF?was chose to remove H₂S and PH₃ because of the high surface area and rich pore structure.In this study,ACF samples modified by transition metals were used to remove H₂S and PH₃ simultaneously.Compared to activated carbon,ACF has a larger specific surface area,richer microporous structure,higher adsorption rate and adsorption capacity which has great potential in the exhaust gas purification.And this study researched several factors,including reaction temperature,different transition metals,the metal concentrations,different precursors,the carbonization temperature,space velocity and the oxygen concentration.And some characterization experiments were used to demonstrate the adsorption and deactivated processes of the simultaneous removal process of H₂S and PH₃.The main results are as follow:?1?Screening and optimization of the preparation condition of one component modified ACF:The research shows the catalyzer prepared in the 0.15:1 Cu-ACF,calcinated at 550? possessed the highest adsorption capacity was about 104.75mgS/g and 169.90mgP/g.Compared with the ACF reported in other literatures,Cu-ACF's adsorption capacity had a obviously increase at the lower temperature?90??.BET,SEM,FTIR,in situ IR,X-ray diffraction,and XPS were employed to characterize its properties and morphology.As the BET and SEM results shows,Cu-ACF possessed the best specific surface area and porous structure because of the well-distribution of copper on ACF's surface.Furthermore,Cu-ACF can remove H₂S and PH₃ efficiently at low temperature and micro-oxygen condition due to its excellent oxidability.?2?The preparation and optimization of two component ACF samples:the effects of different metals and the ratios to ACF samples in the simultaneous removal were investigated.The Cu-Fe,Cu-Mn,Cu-Zn,Cu-Ni and Cu-Co ACF samples were calcinated at 550? for 1h,finally the 15%Cu-0.5% Zn-ACF have the highest removal efficiency.The H₂S removal efficiency can be maintained at 100% for 320 min,and the PH₃ removal efficiency kept over 99% for 280 min,the final adsorption capacity is109.25mgS/g and 187.6mgP/g.Compared with the 15% Cu-ACF,the sulfate adsorption capacity raised 4.3% and the phosphate adsorption capacity raised 10.4%.A little bit of zinc may improve the dispersibility of copper on ACF's surface.?3?The research of reaction conditions:The influences of different space velocity and oxygen concentrations were researched.The results show that the Cu-Zn-ACF exhibited the best simultaneous removal efficiency when space velocity is 5000h^-1,and Cu-Zn-ACF deactivated soon when the space velocity is 20000h^-1.Cu-Zn-ACF had the best removal efficiency at the condition of 1% oxygen concentration.?4?The speculation of deactivated mechanism:In order to infer the reaction mechanism of H₂S and PH₃ by modified ACF samples,XRD were carried out to different ACF samples,the results show that both Cu and CuO exist on the ACF surface.In some study,CuO was considered as the main active component of the removal of H₂S and PH₃,however,the XRD experiment between fresh and deactivated ACF samples shows the Cu exist as simple substance is the main active component in Cu-ACF.There was a positive correlation between the Cu peak intensity and the removal efficiency.And the XPS result indicated the reaction products accumulated on the surface of ACF which are responsible for the deactivation of catalyzer.And the H₂S and PH₃ converted to the sulfate and phosphate that destroyed the active sites of Cu-ACF.