Accumulation of heat stable salts and degraded products during thermal degradation of aqueous methyldiethanolamine (MDEA) using microwave digester and high pressure reactor

Abstract

This study examined thermal degradation of Methyldiethanolamine (MDEA) under different experimental conditions. Samples of the degraded solution were taken at regular interval of times and analyzed using ion chromatography (IC), gas chromatography mass spectrometry (GC–MS) and direct sample analysis with time-of-flight (DSA–TOF) mass spectrometry instruments. Acid–base titrations were carried out to determine the degradation kinetics of MDEA. Heat stable salts (HSS) and various organic degradation products were identified with increasing concentration as degradation time increased. Microwave digester and high pressure reactor were used to study the thermal degradation with fresh 3.781 M MDEA loaded with sour gas (H2S 38 ppm and RSH 40 ppm) at different temperatures and pressures. It was observed that initially thermal degradation of fresh MDEA showed the highest formation of HSS and was ranked as glycolate > acetate > formate using microwave digester. Higher formation rates of the acetate and the glycolate were obtained at higher pressure (2.5 bars) of laboratory reactor, whereas the formation rate of the formate obtained at 2.5 bars was lower than that obtained at 2.0 bars pressure. The degraded products like ethylenediamine, bicine, bis(hydroxyethyl) piperazine (bHEP) etc. were observed with increasing concentration using DSA–TOF analysis. The current research work sheds light on MDEA degradation using different types of reactor, degradation kinetics and degradation products. Details of degradation products as well as kinetic results are presented in this work.