Natural Gas Desulfurization by Adsorption

PI名称：Ralph T.Yang Proposal编号：1826621原始天然气含有不同浓度的硫化氢(H2S)气体，在美国，需要将其浓度降至百万分之四以下。传统上，天然气脱硫是通过使气流与吸收硫化氢的液体气流接触来完成的。虽然液体吸收工艺技术成熟，已经使用了近100年，但它是高度耗能的，也受到设备腐蚀和溶剂损失问题的困扰。吸附是一种非常适合于气体净化的技术，只要找到一种具有高吸附能力和H_2S选择性的高效吸附剂即可。在这项工作中，将开发合成具有优异硫容的胺接枝二氧化硅的新方法。该项目的研究结果可指导设计一种新的、更高效的天然气脱硫工艺。该项目将吸引不同群体的研究生和本科生的积极参与，特别是少数和女性学生。胺接枝介孔二氧化硅是目前最好的脱硫剂，因为它们具有良好的硫容量和选择性，高耐湿性/稳定性，快速吸收速度和可再生性；然而，硫容量需要进一步提高，以使吸附与液体洗涤过程竞争。胺的接枝是通过二氧化硅(即硅烷醇)的表面羟基与氨基硅烷掺杂剂之间的反应完成的。本工作所采用的方法是增加介孔二氧化硅上的硅醇密度，从而直接增加接枝胺，从而增加硫化氢的容量。这项工作包括增加硅醇密度的三个基本策略。介孔二氧化硅MCM-48具有较高的比表面积(~1400m2/g)，将成为主要的二氧化硅材料。也将使用其他二氧化硅，如SBA-15(具有大孔，7-20 nm)和具有扩展孔的MCM-x。这三种策略都是可扩展的和对环境无害的，概括在三个任务中：1)新的和改进的有机模板去除工艺；2)在富含羟基的环境中对介孔二氧化硅进行后处理(即去除模板后)；3)原位合成具有最大硅醇密度的介孔二氧化硅。任务1是主要任务，其中包括旨在提高硅醇密度的新模板去除工艺的五个子任务：微波消解；特殊气体氧化剂；超临界萃取；有机溶剂和离子液体萃取；以及非热(“冷”)等离子体。所得到的具有最高硅醇密度的介孔二氧化硅将进行氨基硅烷接枝和硫化氢吸附/脱附测量，包括平衡吸附等温线和吸附速率。由于这三种战略的结果可能是协同的，所以PI将在拟议工作的后期阶段研究联合治疗方法。这项工作将导致开发出性能优良的硫化氢吸附剂，使吸附技术能够取代目前用于天然气脱硫的湿法胺吸收技术。与煤炭和石油相比，清洁天然气使用量的增加将有助于缓解全球变暖。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

PI Name: Ralph T. YangProposal Number: 1826621Raw natural gas contains various concentrations of hydrogen sulfide (H2S) gas, which needs to be reduced to a concentration below 4 parts per million in the US. Conventionally, natural gas desulfurization is accomplished by contacting the gas stream with a liquid stream that absorbs the H2S. Although the liquid absorption process is technologically mature and has been used for nearly 100 years, it is highly energy intensive and is also plagued by equipment corrosion and solvent loss problems. Adsorption is a technology that is ideally suited for gas purification, provided an efficient sorbent with high adsorption capacity and H2S-selectivity is found. In this work, new approaches for synthesizing amine-grafted silicas with superior sulfur capacity will be developed. Results of this project may guide the design of a new, more efficient process for natural gas desulfurization. This project will involve active participation of a diverse group of graduate as well as undergraduate students, particularly minority and female students.Amine-grafted mesoporous silicas are currently the best desulfurization sorbents because they have good sulfur capacity and selectivity, high moisture resistance/stability, fast uptake rates, and regenerability; however, the sulfur capacity needs to be further improved to make adsorption competitive to the liquid scrubbing process. Amine grafting is accomplished by the reaction between the surface hydroxyl groups of silica (i.e., silanols) and an aminosilane dopant. The approach used in this work is to increase the silanol density on the mesoporous silica, thereby directly increasing the grafted amines and consequently the H2S capacity. The work includes three basic strategies to increase the silanol density. The mesoporous silica MCM-48 will be the main silica to be used because of its high BET surface area (~1400 m2/g). Other silicas such as SBA-15 (with large pores, 7-20 nm) and MCM-x with expanded pores will also be used. The three strategies are all scalable and environmentally sound, outlined in three tasks: 1) new and improved organic-template removal processes; 2) post-treatment (i.e., after template removal) of the mesoporous silica in a hydroxyl abundant environment; 3) in-situ synthesis of mesoporous silicas with maximized silanol densities. Task 1 is the main task, which includes five sub-tasks aimed at new template removal processes to increase silanol density: microwave digestion; special gaseous oxidants; supercritical extraction; extraction using organic solvents and ionic liquids, and nonthermal ("cold") plasma. The resulting mesoporous silicas with the highest silanol densities will be subjected to aminosilane grafting and H2S adsorption/desorption measurements including both equilibrium adsorption isotherms and rates. Because the results of the three strategies may be synergistic, the PI will study combined treatments during the later phase of the proposed work. This work will lead to the development of superior H2S adsorbents that may enable adsorption technology to replace the wet amine absorption technology that is currently used for natural gas desulfurization. The increased use of clean natural gas--compared to coal and oil--will help mitigate global warming.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.