Study On The Removal Of Hydrogen Sulfide In Coke Oven Gas By Ionic Liquid Based Absorbents

In recent years,China's petroleum consumption has been increasing year by year while domestic reserves are seriously insufficient,which results in import dependence,creating a serious threat to energy security.Therefore,improving the utilization efficiency of domestic coal resources is a practical and effective way to mitigate the energy crisis.However,in coal chemical industry how to remove hydrogen sulfide(H2S)in coke oven gas which is harmful to the environment,human health and the equipment is another problem we face.In this study,in order to absorb H2S and avoid environmental pollution of wasted absorbents,ionic liquids(ILs)and deep eutectic solvents(DESs)were prepared as green absorbents for removing H2S from coke oven gas.In this paper,two conventional ionic liquids:diethanolamine acetate([DEA]Ac)and diethylenetriamineacetate([DETA]Ac),two iron-based ionic liquids:triethylamine hydrochloride ferric chloride(TEAH·FeCl4)and urea ferric chloride(Urea·FeCl3)and two types of DESs:tetrabutylammonium bromide/propionic acid(TBAB/Pro)and tetrabutylammonium bromide/caprolactam(TBAB/CPL),were prepared.The effects of temperature and pressure on the amount of H2S absorbed by each absorbent were investigated in the range of 298 K-318 K and 0.10-0.60 MPa temperature and pressure respectively.For above mentioned six absorbents,low temperature and high pressure conditions are favorable for the absorption of H2S,and the optimal absorption temperature is 298 K.For the two kinds of iron-based ionic liquids and the two kinds of DESs,the effects of the molar ratio of iron salt and hydrogen bond donor to hydrogen bond acceptor on the amount of H2S absorbed by each absorbent were investigated respectively.The absorbents with optimum performance are 1.5TEAH·FeCl4,2Urea·FeCl3,TBAB/Pro and TBAB/2CPL.At the temperature of 298 K,the absorption amount of H2S by the six absorbents:[DETA]Ac,[DEA]Ac,1.5TEAH·FeCl4,2Urea·FeCl3,TBAB/Pro and TBAB/2CPL reached 2.91 mmol/g,2.42 mmol/g,3.35 mmol/g,2.13 mmol/g,3.77 mmol/g,and 4.15 mmol/g respectively.Afterwards,the six absorbents:[DETA]Ac,[DEA]Ac,1.5TEAH FeCl4,2Urea-FeCl3,TBAB/Pro and TBAB/2CPL were regenerated,and the absorption performances of H2S by the regenerated absorbents were studied at 298 K and 0.15 MPa.Experimental results showed that for each absorbent the absorption performances of H2S reduced to 89.0%,89.6%,87.1%,84.4%,92.1%and 93.1%of fresh absorbents after 5 times cycles respectively.Finally,the absorption amount of CH4,CO,H2 and C02 by the six absorbents of[DETA]Ac,[DEA]Ac,1.5TEAH·FeCl4,2Urea·FeCl3,TBAB/Pro and TBAB/2CPL is compared with that of H2S.The results showed that the six absorbents almost do not absorb CH4,CO or H2.At the same time they have higher absorption for C02,especially in TBAB/Pro and TBAB/2CPL systems.All in all,the DESs have higher desulfurization selectivity and reutilization performance than the ionic liquids.The two DESs:TBAB/2CPL and TBAB/Pro can remove H2S in large quantities and showed good performance after regeneration.Therefore,TBAB/2CPL and TBAB/Pro can be selected as absorbents for selective removal of H2S from coke oven gas.