A practical approach to produce Mg‐Al spinel based on the modeling of phase equilibria for NH₄Cl‐MgCl₂‐AlCl₃‐H₂O system

Abstract

Based on chemical modeling of phase equilibria for the NH4Cl‐MgCl2‐AlCl3‐H2O system, a practical approach to produce Mg‐Al spinel (MgAl2O4) (widely used as refractory brick, supports in catalysts, and inert material for oxygen carriers) is proposed and proven feasible. This novel process includes coprecipitation of Mg4Al2(OH)14·3H2O from the NH3‐MgCl2‐AlCl3‐H2O system; calcination of Mg4Al2(OH)14·3H2O to obtain Mg‐Al spinel and recovery of NH4Cl from NH4Cl‐rich solutions by feeding MgCl2‐AlCl3. A MSMPR reactor was applied to investigate the effect of temperature, feed concentration, and NH4Cl addition on coprecipitation of precursor Mg4Al2(OH)14·3H2O from MgCl2‐AlCl3 solutions with Mg/Al ratio = 2 through gradual addition of NH4OH. The phase equilibria of the NH4Cl‐MgCl2‐AlCl3‐H2O system were determined over the temperature range 283.2 to 363.2 K using dynamic method. The experimental solubilities were regressed to obtain new Bromley‐Zemaitis model parameters. These newly obtained parameters were verified by predicting the quaternary system. A chemical model for the NH4Cl‐MgCl2‐AlCl3‐H2O system has been established with the OLI platform. All the results generated from this study will provide the theoretical basis for Mg‐Al spinel production. The high quality Mg‐Al spinel was prepared by calcination of precursor from 773.2 to 1273.2 K, and the NH4Cl was successfully recovered through the common ion effect of MgCl2‐AlCl3 addition. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1855–1867, 2013

Determination and modeling of the solubilities of NH4Al(SO4)2·12H2O in the NH4+-Al3+-H3O+-HSO4−-SO42−-H2O system at different H2SO4 molalities and temperatures

“…In this work, the experiments were carried out in a 250 mL jacketed glass vessel by using the dynamic method [21][22]. Fig.…”

“…2À-H 2 O system were measured by using a dynamic method[21][22] at a temperature range from 293.15 to 323.15 K. New parameters of the electrolyte NRTL model[23] in the Aspen plus are obtained via the regression of the all experimental data with the aid of determined K sp of NH 4 Al (SO 4 ) 2 Á12H 2 O. With the new parameters, a chemical model was established for predicting the solubility of NH 4 Al(SO 4 ) 2 Á12H 2 O in the systems mentioned above.…”

A new process for fuel ethanol dehydration based on modeling the phase equilibria of the anhydrous MgCl2 + ethanol + water system

“…The dynamic method similar to that used by Gao and Li 44 was adopted. A known mass of ethanol solution was added to a 250-mL jacketed glass vessel equipped with magnetic stirrer.…”

Measurement and Correlation of Phase Equilibria of Ammonium, Calcium, Aluminum, and Chloride in Aqueous Solution at 298.15 K

“…Among these agents, a waste HCl solution and NH 4 Cl were considered as alternative leaching agents; based on this point, a complex leaching solution containing NH 4 Cl, CaCl 2 , and AlCl 3 was formed; then, separation through crystallization can be used for such complex solution, whereas the design of the crystallization separation process relies on the phase equilibrium research results of the corresponding system. Till now, some papers describing the phase equilibria of the NH 4 Cl, CaCl 2 , and AlCl 3 -containing systems have been reported. − However, there is no report on the phase equilibria of the quaternary system NH 4 Cl–CaCl 2 –AlCl 3 –H 2 O at 298.15 K. Accordingly, in this study, the values of solubility, density, and refractive index of the NH 4 Cl–CaCl 2 –AlCl 3 –H 2 O quaternary system were measured at 298.15 K and the relative diagrams were constructed. Moreover, the equilibrium thermodynamics data of the system NH 4 Cl–CaCl 2 –AlCl 3 –H 2 O at 298.15 K was calculated from the Pitzer and extended Pitzer–Harvie–Weare thermodynamic model.…”