Linear Relationships for Modeling CO2 Absorption in Aqueous Alkanolamine Solutions in a Thermodynamically Consistent Way

A thermodynamically consistent model for the carbon dioxide (CO2) absorption in aqueous alkanolamine system is of great importance in the research and development of a CO2 capture process. To facilitate the development of thermodynamic models, linear Gibbs free energy, enthalpy, and heat capacity relationships using well-known amines as reference are used to correlate the standard reference state properties of ionic species with those of molecular species in the electrolyte system, which has been approved to provide a reliable and consistent way to estimate required parameters when there is minimal or no appropriate experimental data available. The proposed relationships have been applied to the development of an electrolyte Non-Random Two Liquid (NRTL) activity coefficient model for CO2 absorption in aqueous 1-amino-2-propanol (A2P) solution, as an example to demonstration the methodology. With limited vapor-liquid equilibrium data and other thermodynamic properties, the parameters in the electrolyte NRTL model are identified with good accuracy.

Process simulation of biodiesel production from vegetable oil deodorization distillate using hydrotalcite-hydroxyapatite as catalyst

In There are few simulation studies in the literature focusing on the production of biodiesel from vegetable oil deodorization distillate (VODD), a waste originating from the vegetable oil processing stage, using hydrotalcite-hydroxyapatite as a heterogeneous catalyst. In this study, the simulation process was performed using open interface software DWSIM® Version 6.3. The motivation relied on the positive performance of the catalyst during the experimental studies. So, in the simulator design, the lipid raw material, ethanol, and the catalyst were fed together in a CSTR-01 conversion reactor. The thermodynamic fluid package used for this process was the Non-Random Two-Liquid (NRTL) activity coefficient model. The process flowchart consisted of the reaction step (oil transesterification), and separation steps of the ethyl esters produced, excess ethanol and purification of biodiesel. As a result, different scenarios were simulated, using commercial soybean oil as a comparative form, different types of catalysts and different molar ratios of alcohol and VODD. Among the main differences between the simulated cases, it was demonstrated that the excess of alcohol (1:45) caused greater quantity of VODD consumption, and consequently the greater formation of ethyl esters (biodiesel), resulting higher conversions (> 95%). In addition, the results obtained confirmed the adequacy of VODD as a potential raw material to produce biodiesel, as it is relatively cheaper than edible oils and contributes to the use of waste. Thus, confirming that the chemical catalyst was able to form the main esters of fatty acids even using a residual raw material.

Measurement and Correlation of Isobaric Vapor-Liquid Equilibrium Data for Water + 2-Azido-N,N-Dimethylethanamine System at 4 kPa

Isobaric vapor-liquid equilibrium (VLE) data for binary system of water + 2-azido-N,N-dimethylethanamine (DMAZ) was measured at 4 kPa. The results showed an azeotropic point at x1 = 0.985 and T = 302.17 K. The data was correlated with nonrandom two-liquid (NRTL), Wilson and universal quasi-chemical activity coefficient (UNIQUAC) models for the liquid phase. A comparison of the model performances was made using of the criterion of the average absolute deviation, standard deviation and mean standard deviation in boiling-point temperature. The results indicated that the NRTL activity coefficient model satisfactorily correlated the VLE data.