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%.