Determination of Vapor–Liquid Equilibrium (VLE) Plots of 1-Dimethylamino-2-propanol Solutions Using the pH Method

In this work, the pH values of 1-dimethylamino-2-propanol (1DMA2P) solution were measured over a CO2 loading range of 0–0.8 mol CO2/mol amine, 1DMA2P concentration range of 1.5–4.0 mol/L, and a temperature range of 298–303 K. Two-dimensional (2D) vapor–liquid equilibrium (VLE) plots of the 1DMA2P–H2O–CO2 system were established by calculating ion concentrations in the 1DMA2P solution using the pH method. A three-dimensional (3D) VLE surface representing the concentrations of ions in the 1DMA2P solution was also obtained. In addition, equations were generated and used to predict CO2 loading in 1DMA2P solution, based on knowledge of amine concentration, temperature, and pH of the solution. The results showed that these equations performed very well in predicting the CO2 loading of a 1DMA2P solution, with an absolute average deviation (AAD) of 9.2%.