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Issue 14, 2018
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Ionic liquid-mediated solvothermal synthesis of 4,4′-methylenediphenyl diisocyanate (MDI): an efficient and environment-friendly process

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Abstract

4,4′-Methylenediphenyl diisocyanate (4,4′-MDI) is an immensely important intermediate employed in the manufacturing of polyurethanes. Many synthetic routes have been developed over the decades for the synthesis of 4,4′-MDI compounds on a large scale; these compounds are highly toxic and hazardous in nature. In this study, an environment-friendly route is proposed for the synthesis of 4,4′-MDI using 4,4′-diaminodiphenylmethane and dimethyl carbonate (DMC) as starting materials, which are nontoxic in nature. The synthesis of ionic liquids (ILs) and their utilization in the decomposition reaction are systematically investigated. Imidazole-functionalized ionic liquids were prepared for the synthesis of 4,4′-MDI, and their thermal performances were evaluated by TGA. We found that in comparison with other imidazole-functionalized ionic liquids, 1-ethoxycarbonylmethyl-3-methylimidazolium tetrafluoroborate ([EAmim]BF4) exhibited preferable thermal activity for the decomposition of 4,4′-methylenediphenyl dimethylcarbamate (4,4′-MDC). Moreover, these ILs were more effective when they were combined with zinc as a catalyst, which enhanced the decomposition of MDC. Under optimal conditions, the yield of MDI compared to that of Zn(OAc)2–[EAmim]BF4 catalyst increased up to 96%. The mechanism of the enhanced performance of ionic liquids by catalytic activity of zinc acetate was also investigated.

Graphical abstract: Ionic liquid-mediated solvothermal synthesis of 4,4′-methylenediphenyl diisocyanate (MDI): an efficient and environment-friendly process

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Publication details

The article was received on 13 Mar 2018, accepted on 14 Jun 2018 and first published on 15 Jun 2018


Article type: Paper
DOI: 10.1039/C8NJ01175C
Citation: New J. Chem., 2018,42, 12243-12255
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    Ionic liquid-mediated solvothermal synthesis of 4,4′-methylenediphenyl diisocyanate (MDI): an efficient and environment-friendly process

    C. W. Duan, J. You, B. Liu, J. L. Ma, H. P. Zhou, H. B. Zhang and J. Zhang, New J. Chem., 2018, 42, 12243
    DOI: 10.1039/C8NJ01175C

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