Degradation of Amines

Abstract

In view of the rising amounts of greenhouse gases in the atmosphere, preventing CO2 emissions has become increasingly important. The combustion of fossil fuels for energy production and transportation is a large contributor to the problem. One of the ways to reduce the amounts of CO2 being released from combustion is carbon capture and storage (CCS). Post-combustion is the capturing method which has been deemed the easiest to apply to existing power plants in a short period of time. Absorption of CO2 by MEA is the most common method used in post-combustion carbon capture, but there are still many aspects of the process that are not fully understood. Understanding the absorption mechanisms will make it easier to make more economical and environmentally friendly choices in the future. In this thesis the oxidative degradation of monoethanolamine (MEA) has been studied using an open batch setup. The stability of MEA has been studied under different temperatures and concentrations of oxygen in the gas stream. These experiments give a matrix of experiments performed at 55, 65 and 75 °C, with oxygen concentrations of 6, 21, 50 and 98% in the gas stream. To monitor how well the experimental results could be trusted, the water balance was maintained throughout the experiments, and the pH was measured in the flasks capturing volatile degradation compounds.To get a detailed picture of the degradation, the weight percent of nitrogen and the CO2 concentration has been found in the end samples, and the alkalinity and MEA concentration was found for all the samples.11 known degradation compounds have been monitored for the different experiments, and the conditions these compounds are formed at have been compared with the suggested reaction mechanisms. 4 of the products were analyzed as anions using Ion chromatography (IC), and 7 secondary reaction products were analyzed as part of a degradation mix in LC-MS. The dependency of these compounds to temperature and oxygen conditions has been discussed. The primary degradation compounds seems to show a more direct correlation to oxygen flow or temperature, while the secondary degradation reaction shows a bigger variation of temperature and oxygen dependency relative to the conditions of the experiments. Various analytical methods for determination of the known compounds were used to determine the concentration of the degradation compounds in the experiments. The accuracy of these methods was investigated, and the results investigated for both LC-MS, GC-MS and IC-EC, showed large variations. Mixing experiments were performed to investigate the unknown mechanism of N-(2-hydroxyethyl) glycine.