| Phosphorus chemical industry is one of the pillar industries in Yunnan province,and the yellow phosphorus yield is the highest in the world,the purification of yellow phosphorus tail gas is more urgent.Yellow phosphorus tend to produce a large amount of exhaust gas in the production process,its main composition is CO,an important chemical raw material can be used,but the hydrogen sulfide(H-2S),carbon disulfide(CS2)and carbonyl sulfide(COS),and other impurity gas exist in the yellow phosphorus tail gas.This makes the recycling CO from yellow phosphorus tail gas become difficult.This study researched the adsorption oxidation in the case of CO is not affected.In recent years,more and more scholars paid close attention to the non-thermal plasma(NTP)application in material surface modification.The non-thermal plasma modification mainly influences the adsorption performance of the catalysts,and the introduction of specific active group or functional groups on the catalyst surface,can influence the particle size of active components,can also affect load component dispersion on the catalyst surface.According to the preliminary study of catalyst surface modified by Non-thermal plasma,this research used the non-thermal plasma to modify walnut shell activated carbon catalyst,and study the influence of different modification conditions on adsorption/oxidation of H-2S over activated carbon catalyst,and exploratory researched the mechanism of non-thermal plasma modified catalyst.This study can provide a theoretical foundation for the further research about the non-thermal plasma modification mechanism.This research mainly divided into three parts:(1)the catalysts modified with different of discharge type for removing H2S;(2)the catalysts modified with different discharge intensity for removing H2S;(3)the exploration about the NTP surface modification mechanism.The corresponding research contents and conclusions are as follow:(1)The catalysts modified with different discharge type for removing H2SFirst of all,the DBD reactor(plate-plate type,coaxial-cylinder type and needle-plate type)was investigated to modify activated carbon for H2S removal,and found the catalyst modified in coaxial-cylinder type reactor showed a better removal effect,which due to it can produce a uniform discharge.Then with the coaxial-cylinder reactor,different discharge gas(H2,O2,N2,and NH3)was used to modify catalysts on the H2S removal.And the CO2-TPD,CO pulse,and the In-Situ FTIR characterization methods were used to analyze the alkaline loci,the active component,the dispersion of load components and the grain size of active particles,and surface active group on the influence of H2S adsorption oxidation.Different discharge gas would cause different effect on catalyst,which due to the chemical properties of the gas are different.The catalyst modified by oxygen plasma have a bad effect for H2S removal,which would formed the excess oxygen containing groups in the catalyst surface,and reduced the basic sites on the surface of the catalyst,while the effect of etching and ablation may lead to blockages in activated carbon catalyst part of the channel.And the catalysts modified by ammonia plasma show a best hydrogen sulfide removal effect,it can due to ammonia alkali generated by plasma on the surface of the catalyst,and increased the alkali groups,which caused the acidic hydrogen sulfide removal.(2)The catalysts modified with different discharge intensity for removing H2SThe research of this part mainly examines the catalysts modified by different discharge intensity of non-thermal plasma on the removal of H2S.And the different modified voltage(20,25,30,35 and 40 v),different modification time(7.5,10,5,12.5 and 15 min),different electrical gap(3.5,4.5,5.5,4.5 and 7.5 mm)and the thickness of different media(1.0,1.5,and 2.0 mm)were investigated to modifiy active carbon catalyst for H2S removal.And combining with the SEM,BET,XPS,the In-Situ FTIR characterization methods to analyz the experiment result.According to the changes of the catalyst surface morphology after modification,the pore distribution,specific surface,surface elements content and the functional groups were analyzed to explain the influence of NTP modification on catalyst.The catalyst modified with input voltage of 30V has a best effect on H2S removal.The excessive decoration time will lead the surface crosslinking effect and the stoppage of pore structure.From the result of XPS characterization,K and Fe atom were decreased after NTP modification,it seems that the metal particles became smaller after NTP modification,and small particles was easily into the channel that would affect the performance of the H2S adsorption oxidation.After resolvation of N element,the increase of amino was found on catalyst surface,and amine as the basic reactive effect on removal of H2S.Experiment and characterization analysis further showed that non-thermal plasma surface modification effect on the activated carbon catalyst pore structure and the influence of surface chemical groups,which is good for removing hydrogen sulfide.(3)The exploration about the NTP surface modification mechanismThe mechanism of NTP surface modification on the catalyst was explored in this section,it simulated the experimeny of H2S removal and the addition of ammonia to the process of hydrogen sulfide removal.And this section combined with in-situ FTIR experiment to investigate the process of H2S removal over the activated carbon modified by NTP,and used its result to speculate the modification mechanism of NTP on catalysts.Test results show that,first of all,in the process of ammonia plasma modified active carbon catalyst,a part of the ammonia adsorbed to the catalyst surface,and under the action of plasma,a small amount of amino was introduced into the catalyst surface;Then in the process of removing hydrogen sulfide,the hydrogen sulfide and ammonia under atmospheric pressure is easy to react to form NH4-HS,at the same time there is a small number of hydrogen sulfide and amino groups reacted on the surface of the catalyst and formed S-N bond;Sulphide ammonia extremely unstable,and easy to oxidation,this nature makes it easy react with some active hydroxyl oxygen on the catalyst surface and the surface adsorption oxygen oxidation,and further to produce sulfur oxides.At the same time,the sulfur on the S-N was also oxidized to the sulfur oxide.The existence of amino and adsorption of ammonia,change the reaction path of H2S removal over the activated carbon catalysts,it seems that the amino as a bridge,reduces the activation energy required for the oxidation of hydrogen sulfide.In order to test this hypothesis,the study also investigated the effect of the group introduced by NTP modification for the removal of hydrogen sulfide. |
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