Synthesis of Polyoxymethylene Dimethyl Ethers Catalyzed by Broensted Acid Ionic Liquids with Alkanesulfonic Acid Groups

• Published in: Industrial & engineering chemistry research Vol. 53; no. 42; pp. 16254 - 16260
• Main Authors: Wu, Qin, Wang, Min, Hao, Yu, Li, Hansheng, Zhao, Yun, Jiao, Qingze
• Format: Journal Article
• Language: English
• Published: 22.10.2014
• Subjects: Acetal resins; Alkanes; Catalysis; Catalysts; Conversion; Dimethyl ether; Industrial engineering; Ionic liquids; Optimization
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/ie502409t

Catalytic reaction of methylal (DMM) with trioxane (TOX) for preparation of polyoxymethylene dimethyl ethers (PODME sub(n), CH sub(3)O(CH sub(2)O) sub(n)CH sub(3,) where n > 1) was investigated in a series of Broensted acid ionic liquids with alkanesulfonic acid groups. The structures, acidities, and properties of ionic liquids were experimentally characterized and theoretically analyzed. The Broensted acidity-activity correlation for the ionic liquids was studied. Among all these ionic liquids, 1-(4-sulfonic acid) butylpyridinium hydrogen sulfate ([PY-BS][HSO sub(4) super(-)]) exhibited the best catalytic performance, which was ascribed to its strong Broensted acidity. The influences of ionic liquid dosage, molar ratio of DMM to TOX, and reaction temperature on the catalytic reaction were explored using [PY-BS][HSO sub(4) super(-)] as the catalyst. Under the optimal conditions of n(methylal):n(trioxane):n(ILs) = 180:60:1, 170 degree C, and 10h, the conversion of trioxane and the selectivity of PODME sub(3-8) were as high as 91.18% and 70.90%, respectively. The ionic liquid [PY-BS][HSO sub(4) super(-)] could be reused.