Standard molar entropy

About: Standard molar entropy is a research topic. Over the lifetime, 1586 publications have been published within this topic receiving 29886 citations.

Solubility of CO2 in Sulfonate Ionic Liquids at High Pressure

Abstract: In this work, the solubility of CO2 in sulfonate ionic liquids (ILs), such as trihexyl (tetradecyl) phosphonium dodecylbenzenesulfonates ([P6,6,6,14][C12H25PhSO3]) and trihexyl (tetradecyl) phosphonium mesylate ([P6,6,6,14][MeSO3]), was determined at temperatures ranging from (305 to 325) K and pressures ranging from (4 to 9) MPa. It was found that the difference of the solubility of CO2 in two kinds of sulfonate ILs is not dramatic on the basis of molality. The solubility of CO2 in [P6,6,6,14][MeSO3] is higher than that in [P6,6,6,14][C12H25PhSO3]. The solubility data were correlated by means of the extended Henry's law, and the thermodynamic functions, such as the standard enthalpy, standard Gibbs free energy, and standard entropy, were obtained. The Henry's law constant for CO2 in all the investigated ionic liquids increases with increasing temperature.

The assessment of thermodynamic parameters in the Al2O3‐Y2O3 system and phase relations in the Y‐Al‐O system

Abstract: Thermodynamic parameters for solid and liquid phases in the Al 2 O 3 -Y 2 O 3 system are assessed using new calorimetric measurement for the YAG (Y 3 Al 5 O 12 ), YAP (YAlO 3 ) and YAM (Y 4 Al 2 O 9 ) phases. The calculated phase diagram of the Al 2 O 3 -Y 2 O 3 system is in reasonable agreement with experimental data. According to the calculations, the YAP phase melts congruently and is stable down to the low temperatures, while the YAM phase disproportionates to a mixture of YAP and Y 2 O 3 phases at temperatures below 1385 K. The calculated entropy of the YAG phase 300.1 J/(mol.K) is between 2 experimentally determined values 284.8 and 349.1 J/(mol K). However, the difference between calculated and experimental values exceeds uncertainty limits of adiabatic calorimetry data. The enthalpies of melting for the YAG and YAP phases calculated in this study are in reasonable agreement with DTA measurements. The calculated enthalpy of melting for the YAG phase is not consistent with estimates based on solution calorimetric data. New independent measurement of the standard entropy and enthalpy of melting are desirable for the YAG, YAM and YAP phases. The liquidus surface and isothermal section at 2000 K for ternary Al-Y-O system are calculated in this study.

Characterization of catalyst acidity by microcalorimetry and temperature-programmed desorption

Abstract: Microcalorimetric measurements and temperature-programmed desorption (TPD) experiments were conducted to study the acidic properties of H-mordenite and H-ZSM-5. Both zeolites possess a relatively homogeneous acid-strength distribution. The enthalpy changes of adsorption for ammonia on H-mordenite and H-ZSM-5 are −157 and −150 kJ mol−1, respectively. Analyses of the TPD spectra, constrained by the microcalorimetric results, indicate that the standard entropy changes of ammonia adsorption on H-mordenite and H-ZSM-5 are −159 and −171 J mol−1 K−1, respectively. Accordingly, ammonia retains a significant fraction of its local entropy on H-mordenite (i.e., rotation and vibration ), while ammonia adsorbed on H-ZSM-5 loses approximately a third of its local entropy. Pyridine desorption from these zeolites is limited by molecular diffusion in the zeolite particles and for this reason is a poor choice as a probe molecule for assessment of acid-site strength by TPD.