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Ionic Liquid–Silicotungstic Acid Composites as Efficient and Recyclable Catalysts for the Selective Esterification of Glycerol with Lauric Acid to Monolaurin
Author(s) -
Han Xiaoxiang,
Zhang Xiaofang,
Zhu Guangqi,
Liang Juanjuan,
Cao Xianghui,
Kan Renjun,
Hung ChinTe,
Liu LiLi,
Liu ShangBin
Publication year - 2017
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201600788
Subject(s) - silicotungstic acid , catalysis , ionic liquid , lauric acid , chemistry , glycerol , yield (engineering) , mesoporous material , nuclear chemistry , organic chemistry , materials science , fatty acid , metallurgy
The synthesis of glycerol monolaurate (GML) by the esterification of glycerol (GL) with lauric acid (LA) over a series of propyl sulfonic acid‐functionalized ionic liquids (SAFILs)‐modified silicotungstic acid (STA; H 4 SiW 12 O 40 ) composite catalysts has been investigated. The synthesized organic–inorganic hybrid catalysts were characterized by different physicochemical techniques. In particular, their acidic properties were studied by solid‐state 31 P magic angle spinning (MAS) NMR spectroscopy by using adsorbed trimethylphosphine oxide (TMPO) as a probe. The effects of key reaction parameters, such as glycerol/lauric acid molar ratio, amount of catalyst, reaction time, and reaction temperature on LA conversion and GML product yield were elucidated and optimized with response surface methodology (RSM). The N , N ‐dimethyl(benzyl)ammonium propyl sulfobetaine (DMBPS)‐modified STA [DMBPSH]H 3 SiW 12 O 40 exhibited the optimal catalytic activity and was exploited for process optimization. A highest GML yield of 79.1 % was achieved with the optimized reaction conditions. The high catalytic activity of these hybrid catalysts were attributed to strong acidity, low transport resistance, and their “pseudoliquid” characteristics. A kinetic study was made based on a second‐order irreversible model of the esterification reaction, which resulted in an activation energy of 39.49 kJ mol −1 for [DMBPSH]H 3 SiW 12 O 40 under optimized reaction conditions.