Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06520, United States.
Environ Sci Technol. 2012 Sep 4;46(17):9793-801. doi: 10.1021/es301867b. Epub 2012 Aug 16.
With years of full-scale experience for precombustion CO(2) capture, amine-based technologies are emerging as the prime contender for postcombustion CO(2) capture. However, concerns for postcombustion applications have focused on the possible contamination of air or drinking water supplies downwind by potentially carcinogenic N-nitrosamines and N-nitramines released following their formation by NO(x) reactions with amines within the capture unit. Analytical methods for N-nitrosamines in drinking waters were adapted to measure specific N-nitrosamines and N-nitramines and total N-nitrosamines in solvent and washwater samples. The high levels of amines, aldehydes, and nitrite in these samples presented a risk for the artifactual formation of N-nitrosamines during sample storage or analysis. Application of a 30-fold molar excess of sulfamic acid to nitrite at pH 2 destroyed nitrite with no significant risk of artifactual nitrosation of amines. Analysis of aqueous morpholine solutions purged with different gas-phase NO and NO(2) concentrations indicated that N-nitrosamine formation generally exceeds N-nitramine formation. The total N-nitrosamine formation rate was at least an order of magnitude higher for the secondary amine piperazine (PZ) than for the primary amines 2-amino-2-methyl-1-propanol (AMP) and monoethanolamine (MEA) and the tertiary amine methyldiethanolamine (MDEA). Analysis of pilot washwater samples indicated a 59 μM total N-nitrosamine concentration for a system operated with a 25% AMP/15% PZ solvent, but only 0.73 μM for a 35% MEA solvent. Unfortunately, a greater fraction of the total N-nitrosamine signal was uncharacterized for the MEA-associated washwater. At a 0.73 μM total N-nitrosamine concentration, a ~25000-fold reduction in concentration is needed between washwater units and downwind drinking water supplies to meet proposed permit limits.
经过多年的预燃烧 CO(2)捕集全面经验，基于胺的技术作为后燃烧 CO(2)捕集的主要竞争者出现了。然而，对于后燃烧应用的关注集中在潜在的致癌性 N-亚硝胺和 N-亚硝胺可能污染空气或饮用水供应的可能性，这些物质是在氮氧化物（NOx）与捕集单元内的胺反应形成后释放的。对饮用水中的 N-亚硝胺的分析方法进行了调整，以测量溶剂和洗涤水样品中的特定 N-亚硝胺和 N-亚硝胺以及总 N-亚硝胺。这些样品中高浓度的胺、醛和亚硝酸盐存在样品储存或分析过程中人为形成 N-亚硝胺的风险。在 pH 值为 2 时，应用 30 倍摩尔过量的氨基磺酸处理亚硝酸盐，可以破坏亚硝酸盐，而胺的人为亚硝化风险很小。分析用不同气相 NO 和 NO(2)浓度吹扫的吗啉溶液表明，N-亚硝胺的形成通常超过 N-亚硝胺的形成。对于仲胺哌嗪（PZ），总 N-亚硝胺形成速率至少比伯胺 2-氨基-2-甲基-1-丙醇（AMP）和单乙醇胺（MEA）和叔胺甲基二乙醇胺（MDEA）高一个数量级。对中试洗涤水样品的分析表明，在 25%AMP/15%PZ 溶剂系统中运行时，总 N-亚硝胺浓度为 59 μM，但在 35%MEA 溶剂中仅为 0.73 μM。不幸的是，MEA 相关洗涤水中的总 N-亚硝胺信号的更大比例未被表征。在 0.73 μM 的总 N-亚硝胺浓度下，需要在洗涤水单元和下风饮用水供应之间将浓度降低 25000 倍，才能达到拟议的许可限值。
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