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A practical approach to produce Mg‐Al spinel based on the modeling of phase equilibria for NH 4 Cl‐MgCl 2 ‐AlCl 3 ‐H 2 O system
Author(s) -
Gao Wencheng,
Li Zhibao
Publication year - 2013
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.13963
Subject(s) - coprecipitation , spinel , chemistry , calcination , phase (matter) , inorganic chemistry , catalysis , analytical chemistry (journal) , nuclear chemistry , materials science , metallurgy , chromatography , organic chemistry
Based on chemical modeling of phase equilibria for the NH 4 Cl‐MgCl 2 ‐AlCl 3 ‐H 2 O system, a practical approach to produce Mg‐Al spinel (MgAl 2 O 4 ) (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 Mg 4 Al 2 (OH) 14 ·3H 2 O from the NH 3 ‐MgCl 2 ‐AlCl 3 ‐H 2 O system; calcination of Mg 4 Al 2 (OH) 14 ·3H 2 O to obtain Mg‐Al spinel and recovery of NH 4 Cl from NH 4 Cl‐rich solutions by feeding MgCl 2 ‐AlCl 3 . A MSMPR reactor was applied to investigate the effect of temperature, feed concentration, and NH 4 Cl addition on coprecipitation of precursor Mg 4 Al 2 (OH) 14 ·3H 2 O from MgCl 2 ‐AlCl 3 solutions with Mg/Al ratio = 2 through gradual addition of NH 4 OH. The phase equilibria of the NH 4 Cl‐MgCl 2 ‐AlCl 3 ‐H 2 O 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 NH 4 Cl‐MgCl 2 ‐AlCl 3 ‐H 2 O 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 NH 4 Cl was successfully recovered through the common ion effect of MgCl 2 ‐AlCl 3 addition. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1855–1867, 2013