Study On Preparation And Properties Of 1-butyl-3-methylimidazolium Terachloroferrate Desulfurizer With High Sulfur Capacity

Hydrogen sulfide?H₂S?gas produced in industrial production is an exceedingly harmful environmental pollutant,which is harmful to the industry,the environment and human health.In recent years,quite a few researchers have carried out research and development of new green ionic liquid desulfurizers for the removal of H₂S,and achieved some positive results.Among them,the 1-butyl-3-methylimidazolium terachloroferrate?[Bmim]FeCl₄,Fe-IL?was favored by researchers because it can be directly oxidized by H₂S to obtain sulfur due to its non-aqueous phase catalytic oxidation.It produces less sewage and is not easily degraded,and its green desulfurization essence is studied.However,the pure Fe-IL desulfurization solution has a viscosity of 283.15K up to 36mPa.s,and the acidity is strong,resulting in poor gas-liquid mass transfer rate.The working sulfur capacity is only 0.1g/L,the same with the traditional aqueous phase wet oxidative desulfurization lo-cat process sulfur capacity,and much smaller than its theoretical sulfur capacity,which hinders the ability of Fe-IL to efficiently absorb H₂S.In this thesis,a composite desulfurizing agent was constructed by introducing different types of aprotic strong polar organic solvents and Fe-IL desulfurizer and the physical solvent has the advantage of excellent absorption of H₂S.Firstly,the physical dissolution of H₂S is promoted,elemental sulfur is formed by the high concentration of Fe?III?in the ionic liquid to oxidize H₂S,thereby a high sulfur capacity desulfurizer is prepared to achieve high-efficiency absorption and desulfurization of H₂S,the basic research on phase equilibrium and desulfurization kinetics was further carried out on the prepared composite desulfurizer.The main results are as following:For the features of strong acidity and high viscosity of pure Fe-IL,this study selected weak alkaline and low viscosity organic solvent of N-methylpyrrolidone?NMP?,Polyethylene glycol dimethyl ether?PEGDE?,and N-formylmorpholine?NFM?,with Fe-IL are mutually soluble to form a composite desulfurizing agent,based on the pure Fe-IL desulfurization performance.Experiments show that several physical solvents can form a good solvent solution with Fe-IL,which enhance the desulfurization effect.When the mass ratio of physical solvent to Fe-IL is 5:5,the effect of enhanced desulfurization is the best.Among them,Fe-IL desulfurization effect reaches the best when NMP add.Fe-IL:NMP=5:5composite desulfurization solution,293.15K and 1atm,5%H₂S concentration of standard gas?CH₄ 95%?at 10ml/min flow rate,30min desulfurization time,low purity of purified natural gas H₂S at 10mg/m³,the chemical sulfur capacity is 0.42g/L,which is 2.5 times of the pure Fe-IL sulfur capacity,which is more than 4 times that of the conventional lo-cat chemical sulfur capacity 0.1g/L,which reaches the preparation of high sulfur capacity of Fe-IL requirements.?2?In order to understand the solubility of H₂S in Fe-IL/NMP desulfurization solution,further phase equilibrium studies were carried out,the results show that the equilibrium solubility of H₂S in the desulfurized liquid increases with increasing pressure,temperature and NMP in the composite desulfurizer.At the same time,the order of influence on equilibrium solubility is:pressure>compound ratio>temperature;the absorption of H₂S in pure Fe-IL is mainly physical dissolution and its chemical sulfur capacity increase with the pressure and temperature increase;the Fe-IL/NMP compound solution increases from293.15K to 333.15K,and the desorption tendency of H₂S from the composite desulfurizer increases,resulting in a decrease in physical solubility.When the temperature rises,the viscosity of the system decreases,which promotes the dissolution and diffusion of H₂S in the desulfurization solution,which is beneficial to the dissociation of H₂S and the oxidation reaction with Fe?III?.The increase of chemical solubility promotes the enhancement of oxidation absorption efficiency;among them,composite desulfurizer reached the dissolution equilibrium at 333.15K and 1.8MPa when Fe-IL:NMP=5:5,and the physical solubility was0.5721mol/L and the chemical sulfur capacity was 28.56g/L.?3?The kinetics of H₂S absorption by Fe-IL/NMP desulfurizer was studied by using the levenspiel partition method.The results show that the process of absorbing H₂S is a rapid first-order reaction,and the desulfurization process is mainly controlled by liquid film,the Fe-IL:NMP=5:5 desulfurization kinetics study show that the reaction order of Fe?III?was2.07.Under the conditions of 293.15K and 0.5MPa,the conversion of Fe?III?before and after the reaction was 32%.Compared with pure Fe-IL,the Fe?III?conversion rate increased by 3times under the same conditions,which indicate that the addition of NMP can reduce the acidity of the desulfurizer and promote the dissolution of H₂S.On the other hand,the decrease of the viscosity of the solution improves the gas.The liquid mass transfer efficiency also ultimately promotes the increase of the reaction rate.In summary,by adding a certain proportion of physical solvent to the pure Fe-IL desulfurizer,not only can the desulfurizer maintain high purification degree,but also the sulfur capacity is significantly increased,the goal of preparing high sulfur capacity desulfurizer is achieved.It lays a good foundation for the later development and application of desulfurizer.