Pressure-temperature phase diagram of tris(hydroxymethyl)aminomethane and phase diagram determination of tris(hydroxymethyl)aminomethane -- 2-amino-2-methyl-1, 3-propanediol (AMPL) binary system

A pressure-temperature phase diagram of the tris(hydroxymethyl)aminomethane(TRIS) and a temperature-composition equilibrium phase diagram of the tris(hydroxymethyl)aminomethane(TRIS) -- 2-Amino-2methyl-1,3-propanediol(AMPL) binary system are developed. The component organic crystalline materials undergo solid-solid phase transitions and their property make them suitable for storage of thermal energy. The low temperature crystal structure of pure TRIS is orthorhombic, and that of the pure AMPL is monoclinic.;In this study, Raman spectroscopy was performed at different temperatures and pressures to determine structural changes in the P-T diagram of TRIS. In situ high-pressure/high-temperature Raman spectroscopy experiments were carried out using resistively heated heated diamond anvil cells up to 160°C and 7 GPa. High pressure experiments performed at room temperature showed transformation of the orthorhombic alpha-TRIS to beta-TRIS phase at ∼1.17 GPa. As the temperature is increased to ∼130°C at ambient pressure, both alpha and beta phases transform to gamma-TRIS. The experiments were also run at different temperatures and pressures, by which a typical pressure-temperature phase diagram of TRIS has been developed.;The binary phase diagram of TRIS-AMPL was constructed using the PANalytical X-ray diffractometer and differential scanning calorimetric data. It was found that below ∼75°C, there is virtually no solubility of AMPL in TRIS or vice versa. The AMPL rich alpha phase transforms to an AMPL rich gamma phase at ∼75°C. Between ∼75°C and 105°C a wide beta+gamma phase region is observed. The maximum solubility of TRIS in AMPL is at ∼12% TRIS at 73°C and that of AMPL in TRIS is 40% AMPL at ∼125°C. The phase diagram exhibits two eutectoidal transformations at 73°C (gamma→alpha+beta) and at 108°C (gamma1→beta+gamma) respectively. The phase diagram also exhibits a peritectic transformation at 128°C (L+gamma 1→gamma). A two phase region with gamma+gamma1 plastic phases rich in TRIS and AMPL is also observed between 105°C and 125°C. Lattice parameters changes with increase in temperature have also been studied.