Natural Gas Desulfurization by Adsorption

PI姓名：Ralph T. YangProposal编号：1826621原料天然气含有各种浓度的硫化氢（H2S）气体，在美国需要将其浓度降低到低于百万分之四。常规地，天然气脱硫通过使气流与吸收H2S的液流接触来实现。 虽然液体吸收工艺技术成熟，使用了近100年，但它是高能耗的，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气体净化的技术，只要找到具有高吸附容量和H2S选择性的有效吸附剂，在这项工作中，将开发合成具有上级硫容量的胺接枝二氧化硅的新方法。 该项目的结果可以指导设计一种新的，更有效的天然气脱硫工艺。 胺接枝介孔二氧化硅是目前最好的脱硫吸附剂，因为它们具有良好的硫容量和选择性，高的抗湿/稳定性，快速的吸收速率和可再生性;然而，需要进一步提高硫容量以使吸附与液体洗涤工艺竞争。胺接枝是通过二氧化硅的表面羟基（即，硅烷醇）和氨基硅烷掺杂剂。 在这项工作中使用的方法是增加硅醇密度的介孔二氧化硅，从而直接增加接枝胺，因此H2S的容量。 这项工作包括三个基本策略，以增加硅烷醇密度。 介孔二氧化硅MCM-48将是主要的二氧化硅被使用，因为它的高BET表面积（~1400 m2/g）。 也将使用其它二氧化硅，例如SBA-15（具有大孔，7-20 nm）和具有膨胀孔的MCM-x。这三项战略都是可扩展的和环境无害的，概述了三项任务：1）新的和改进的有机模板去除工艺; 2）后处理（即，模板去除后）在羟基丰富的环境中的介孔二氧化硅; 3）原位合成具有最大化硅烷醇密度的介孔二氧化硅。 任务1是主要任务，其包括针对新的模板去除工艺以增加硅烷醇密度的五个子任务：微波消解;特殊气体氧化剂;超临界萃取;使用有机溶剂和离子液体的萃取，以及非热（“冷”）等离子体。 所得具有最高硅烷醇密度的中孔二氧化硅将经受氨基硅烷接枝和H2S吸附/脱附测量，包括平衡吸附等温线和速率。由于三种策略的结果可能是协同的，PI将在拟议工作的后期研究联合治疗。这项工作将导致上级H2S吸附剂的发展，可能使吸附技术，以取代目前用于天然气脱硫的湿胺吸收技术。与煤炭和石油相比，清洁天然气的使用增加将有助于减缓全球变暖。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值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.