In this work the solidÀliquid equilibrium (SLE) and freezing-point depression (FPD) in the electrolytic binary aqueous systems piperazine (PZ, and aqueous 2-amino-2-methyl-1-propanol (AMP, were measured. The FPD and solubility were also determined in the ternary AMPÀPZÀH 2 O system. A method was developed by which solubility can be determined at higher temperatures using the FPD setup. A total of 86 data points are listed in the full concentration range from (À35 to 90)°C. The solid phases piperazine hexahydrate (PZ 3 6H 2 O), piperazine hemihydrate (PZ 3 1/2H 2 O), and anhydrous PZ precipitated during the experiments. The data can be used in the formulation, prevention, or intentional formation of slurries in piperazine solvents for promoting CO 2 capture using absorption and desorption. INTRODUCTIONCO 2 capture is an openly debated topic for carbon emission reduction to reduce pollution by greenhouse gases. Process streams containing carbon dioxide can be cleaned by absorption in aqueous liquid solvents. Amines, strong bases, or combination of the two are typically used as active components. The low heats of absorption and desorption are design criteria that reduce the cost of energy in regeneration of the solvent. This is obtained by using sterically hindered amines. The result is often slow reaction kinetics between the solvent and CO 2 . Consequently piperazine (PZ) is being used in solution formulation to create an enhanced CO 2 capture solvent. PZ can be used with both amine and potash solutions (K 2 CO 3 ) to increase the rate of absorption and thereby promote the CO 2 capture.A lower PZ concentration was typically used in literature. Recently the scope has changed, and PZ is now being used at higher concentrations. On increasing the concentration, the solubility limit of PZ is being reached, especially during winter temperatures and even up to room temperature. The unexpected formation of slurries and solids downstream may create unforeseen process conditions, decrease efficiency, and create clogging which will result in unfortunate hazardous operations. In general it could be interesting to provoke the formation of CO 2 containing solids and thereby facilitate and increase the capacity of the capture solvent. CO 2 deprived solids are rarely preferable in terms of CO 2 capture.The aim of this work is to determine the solidÀliquid phase boundary in the two binary PZÀH 2 O and AMPÀH 2 O systems and also in the ternary AMPÀPZÀH 2 O system. 2-Amino-2-methyl-1-propanol (AMP) is a sterically hindered amine. CO 2 absorption in AMP solutions can be promoted by adding PZ.An additional goal of this work was to enhance the utilization of freezing-point depression (FPD) equipment developing a method for the purpose of studying solidÀliquid equilibrium (SLE) behavior in solutions precipitating solids other than ice.

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In this work the solid-liquid equilibrium (SLE) of the ternary system 2-amino-2-methyl-propanol (AMP)-piperazine (PZ)-H2O and the aqueous binary system AMP were determined using a freezing point depression (FPD) setup and differential scanning calorimetry (DSC). A total of 59 new data points are listed in the full concentration range of 0 < w(AMP) < 100 % and 0 < w(PZ) < 61 %. The SLE phase boundary of AMP tetrahydrate (AMP•4H2O) was determined and confirmed by its crystal structure obtained from powder x-ray diffraction (PXRD).The new data of this work can be used in the creation of thermodynamic model for prevention of AMP and PZ precipitates from solvents used for CO2 capture. This gives a higher degree of safe

In this work, the solid–liquid equilibrium (SLE) of the systems glycine (Gly)–H2O, Gly–NaOH–H2O, Gly–NaHCO3–H2O, and Gly–NaOH–NaHCO3–H2O was determined using a freezing point depression (FPD) setup. A total of 131 new data points are listed in the concentration range 0 < b (sodium glycinate (SG)) < 25 mol SG/kg water. The system Gly–NaOH–H2O with five different mole ratios (n NaOH:n Gly) 1:1, 1:2, 1:5, 2:1, and 5:1 and the CO2-loaded system Gly–NaOH–NaHCO3–H2O were analyzed in a loading range of 0.1–1 mol CO2 per mol SG. Eutectic points and hydrate formations were identified in the systems Gly–H2O, Gly–NaOH–H2O, and Gly–NaOH–NaHCO3–H2O. The solubility of SG increased linearly with higher concentrations for systems with an excess of NaOH. The solubility of SG decreased significantly with an excess addition of NaOH and glycine. The same trend was observed in the CO2-loaded system. The new data create a better understanding of phase equilibria in this system. This understanding is useful for the thermodynamic modeling of the system, which can potentially be used for CO2 capture. The data give a clear representation of the degree of safe operation in terms of managing a plant without solid formation.