Tandem Mass Spectrometry Measurement of the Collision Products of Carbamate Anions Derived from CO<sub>2</sub> Capture Sorbents: Paving the Way for Accurate Quantitation
作者:Phil Jackson、Keith J. Fisher、Moetaz Ibrahim Attalla
DOI:10.1007/s13361-011-0161-5
日期:2011.8.1
The reaction between CO2 and aqueous amines to produce a charged carbamate product plays a crucial role in post-combustion capture chemistry when primary and secondary amines are used. In this paper, we report the low energy negative-ion CID results for several anionic carbamates derived from primary and secondary amines commonly used as post-combustion capture solvents. The study was performed using the modern equivalent of a triple quadrupole instrument equipped with a T-wave collision cell. Deuterium labeling of 2-aminoethanol (1,1,2,2,-d4-2-aminoethanol) and computations at the M06-2X/6-311++G(d,p) level were used to confirm the identity of the fragmentation products for 2-hydroxyethylcarbamate (derived from 2-aminoethanol), in particular the ions CN−, NCO− and facile neutral losses of CO2 and water; there is precedent for the latter in condensed phase isocyanate chemistry. The fragmentations of 2-hydroxyethylcarbamate were generalized for carbamate anions derived from other capture amines, including ethylenediamine, diethanolamine, and piperazine. We also report unequivocal evidence for the existence of carbamate anions derived from sterically hindered amines (Tris(2-hydroxymethyl)aminomethane and 2-methyl-2-aminopropanol). For the suite of carbamates investigated, diagnostic losses include the decarboxylation product (−CO2, 44 mass units), loss of 46 mass units and the fragments NCO− (m/z 42) and CN− (m/z 26). We also report low energy CID results for the dicarbamate dianion (−O2CNHC2H4NHCO2−) commonly encountered in CO2 capture solution utilizing ethylenediamine. Finally, we demonstrate a promising ion chromatography-MS based procedure for the separation and quantitation of aqueous anionic carbamates, which is based on the reported CID findings. The availability of accurate quantitation methods for ionic CO2 capture products could lead to dynamic operational tuning of CO2 capture-plants and, thus, cost-savings via real-time manipulation of solvent regeneration energies.
CO2与水合胺反应生成带电的碳酸酯产品,在使用一胺和二胺时在后燃烧捕获化学中发挥着至关重要的作用。本文报告了一些常用于后燃烧捕获溶剂的一胺和二胺衍生的阴离子碳酸酯的低能负离子碰撞解离(CID)结果。该研究采用现代三重四极杆仪器及T波碰撞池进行。对2-氨基乙醇(1,1,2,2,-d4-2-氨基乙醇)的重氮标记以及M06-2X/6-311++G(d,p)水平的计算用于确认2-羟基乙基碳酸酯(源自2-氨基乙醇)裂解产物的身份,特别是离子CN−、NCO−及易于失去的CO2和水;后者在凝聚态异氰酸酯化学中已有先例。2-羟基乙基碳酸酯的裂解情况为来自其他捕获胺(包括乙二胺、二乙醇胺和哌嗪)的碳酸酯阴离子进行了概括。我们还报告了来源于空间位阻较大的胺(Tris(2-羟基甲基)氨基甲烷和2-甲基-2-氨基丙醇)的碳酸酯阴离子存在的明确证据。对于所研究的一系列碳酸酯,特征性失去包括脱羧产物(−CO2, 44质量单位)、损失46质量单位,以及片段NCO−(m/z 42)和CN−(m/z 26)。我们还报告了在利用乙二胺的CO2捕获溶液中常遇到的二碳酸酯二阴离子(−O2CNHC2H4NHCO2−)的低能CID结果。最后,我们展示了一种基于离子色谱-MS的有前景的水合阴离子碳酸酯分离和定量程序,该程序基于所报告的CID发现。对于离子CO2捕获产物的准确定量方法的可用性可能导致CO2捕获工厂的动态操作调整,从而通过实时操控溶剂再生能量实现成本节约。