Development And Process Design Of Environmentally Friendly Fe-based Ionic Liquid Desulfurizer

Ionic liquids have low saturation vapor pressure,good chemical stability,and thermal stability.Due to the addition of iron ions,iron-based ionic liquid have excellent catalytic oxidation characteristics,are easily separated from sulfur and can reduce environmental pollution caused by volatilization or degradation.Therefore,it is recyclable and a new type of environmentally friendly iron-based desulfurizer.And it can reduce the circulation of the desulphurizing solution because its theoretical sulfur capacity is 100 times higher than that of the conventional water phase oxidation process.Thus.it can realize the miniaturization of the desulphurizing device.The desulphurization degree of iron-based ionic liquid（Fe-IL）can satisfy the index of gas transmission and the stability of the solvent is high.So,it can reduce the difficulty of natural gas purification process and the danger of operation,which makes the production process safer.In this paper,the experimental research of the removal of H₂S by Fe-IL was carried out and the desulfurization process was designed in order to analyze the technical rationality of the Desulphurizer and process,and lay the foundation for the follow-up study.The specific research content is as follows:（1）Fe-IL was synthesized by FeCl₃ and 1-Butyl-3-methylimidazolium chloride（[Bmim]Cl）as raw materials under different ratios.And after purification,the yield was up to 86.97%.It was higher 27.15%than that by the common method and the use of ferric chloride was reduced by 20%.（2）[Bmim]Fe_0.97Cl_4.13,the molecular formula of Fe-IL,was determined by chemical titration,instrument determination and FT-IR characterization.The viscosity temperature test showed that the viscosity of Fe-IL was only 19.6 mPa·s at 45℃.It was 39.1%lower than that at 25℃and beneficial to industrial application.The chemical structure of the prepared Fe-IL remains unchanged after being placed in the air for 90 days,which showed its chemical stability was excellent.（3）The desulfurization experiment of Fe-IL showed that the maximum sulfur capacity was only 4.6%of the theoretical sulfur capacity,the apparent activity of iron ion was low and there were two absorption,physical and chemical oxidation absorption,in the desulfurization process at 25℃,1.01×10⁵Pa.The desulfurization absorption experiment of natural gas containing 5%H₂S showed that the sulfur capacity was 0.38 g/L and the desulfurization process was mainly by chemical oxidation absorption.For the absorption experiment of natural gas containing 99.9%H₂S,the sulfur capacity was up to 3.1 g/L and the physical absorption of the total desulfurization rate was up to 78.7%.It was possibly caused by high concentration of H₂S rapidly dissolved in ionic liquids by physical absorption to promote chemical oxidation absorption.Therefore,the sulfur capacity of the desulfurizer was increased.（4）The water was produced in the purification process of natural gas because of the hydrophobicity and weak acidity of Fe-IL.Fe-IL with water desulphurization experiment indicated that water had a promoting effect on the absorption of H₂S by Fe-IL in a certain range,but excessive water can reduce the absorption of H₂S.When the water content was 2%,the mass of H₂S liquid by absorption was increased by 18.6%than that of non water absorption.It may be that the water decreases the viscosity of the desulfurizer and promotes the gas-liquid mass transfer rate.Or the water reduced the acid in the desulfurizer,so that H₂S was more easily dissolved in the desulfurizer to promote oxidation absorption.（5）A wet oxidation desulfurization process at normal temperature and atmospheric pressure was developed based on the characteristics of high sulfur capacity,hydrophobicity and oxidation absorption of Fe-IL.It has the characteristics of higher desulfurization efficiency,no pollution for the environment and lower energy.Therefore,it can solve the shortcomings of the current sulfur containing tail gas treatment technology to meet the increasing environmental protection requirements,lay a solid foundation for the green development and transformation of the industrial technology of sulfur containing tail gas treatment.