| Iron oxide materials cause much attention for its rich structures and widely applications.In recent years,with the gradual improvement of environmental requirements,the highly toxic and foul-smelling H2S gas emission standards have been becoming increasingly stringent.In many solid desulfurization agents,iron-based sorbent for its high sulfur capacity,good regeneration,cheap and readily available raw materials,are widely used.However,the studies concerning desulfurization mechanism and active site of iron-based sorbents were carried out less.Therefore,it is absolutely necessary to carry out related research to provide theoretical guidance for the development of wider application scope and better performance desulfurization sorbent.So,in this paper,selecting the y-FeOOH,which has relatively simple and layered structure,as the research object and starting from iron oxide morphology,crystal phase,surface groups,we have delved into the main factors of influencing the desulfurization performance and established mutual connections among phase structure,surface species and material desulfurization performance by utilizing XRD,BET,SEM,TEM,XPS,Raman,In situ DRIFTS,to provide reference and guidance for the development of more high-performance iron-based desulfurization material.Firstly,the effects of different preparation conditions(temperature,reaction time,EDTA content,etc.)on ?-FeOOH crystal phase and surface groups were characterized and analyzed.The results showed that,when c(Fe2+)/c(EDTA)=1:0.03,the crystallization of the product was more perfect,and excessive Fe2+ on growth of grains had a certain inhibition,resulting in some agglomeration.Higher reaction temperature(40 ?),suitable aging temperature(50 ?)and long aging time(4h)favor the growth of crystal grains.For another prepared preferably crystallization of y-FeOOH,its surface was rich hydroxyl groups and adsorbed a certain amount of H2O molecules,with very little EDTA residue.Secondly,through regulating the solution pH during the preparation system,we prepared the ?-FeOOH having a different surface hydroxyl species and explored the relationship between H2S removal performance of the related materials at low temperature and the structure,surface hydroxyl groups.At pH=5,6,breakthrough sulfur capacity of the synthesized samples were only 1.2%?1.5%,desulfurization precision very poor;but at pH=7,8,9,it were up to 55%with extremely high precision desulfurization.Before the samples were exhausted,its outlet H2S is 0 ppm.Series characterization discovered that with the pH increased,particle size was decreased,slightly,and its morphology changed from the wider lath-shaped into elongated rod-shaped.The number of ?2-OH and ?3-OH almost unchanged,the ?-OH gradually increased,which were a good correlation with desulfurization performance of samples.It can be concluded,the basic hydroxyl groups,?-OH on ?-FeOOH surface may be the active sites removal H2S at low temperature.Finally,by calcination controlling the dehydrated degree of precursor ?-FeOOH,we prepared the iron oxides having a different crystal phase,surface species and specific surface area,and then its removal performance were investigated.We found that different iron oxides had significantly different desulfurization active sites.The sample treated by relative low temperature(?220?)still being?-FeOOH,its surface hydroxyl species were the key active sites;the treated sample at 250 ?being ?-Fe2O3,rich oxygen vacancies was the main active sites.In addition,its larger specific surface area to improve desulfurization performance made a great contribution;with temperature increasing,the sample became preferably crystallized?-Fe2O3 at 350 ?,and although its specific surface area was decreased significantly,rich oxygen vacancies still made it show excellent desulfurization performance on its surface;the sample calcined at 450 ? being ?-Fe2O3,removal H2S at low temperature was the worst.It was the smallest surface area that affected the reaction of H2S in contact with the sample. |
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