Preparation of Diisopropyl Carbonate from Isosorbitol by Ionic Liquid Catalysis

Ionic liquids, as catalysts for carbonate derivatives, have high conversion rates and strong selectivity, and are environment-friendly. In this study, [HO–(CH₂)₂–mim]5[Ti(H₂O)FeMo₁₁O₃₉] (IL-Fe) was prepared using sodium molybdate, TiCl₄, and 1-hydroxypropyl-3-methylimidazolium bromide salt ([HO–(CH₂)₂–mim]Br). The products were characterised by IR, XRD, TGA, and UV spectroscopy, which showed that the structures were correct and that the catalysts were thermally stable. The synthesis of BISBC by IL-Fe-catalysed ISB was carried out and the structural characterisation and synthetic conditions of BISBC were optimised by orthogonal tests. The experimental results showed that four factors, i.e. feeding ratio, catalyst dosage, reaction temperature, and reaction time, affected the yield of the BISBC prepolymer in descending order. The optimum process conditions for the BISBC yield were defined: feeding ratio n(DMC) : n(ISB) = 5; catalyst dosage = 1.0 wt %; reaction temperature = 80°C; reaction time = 5 h. Under these reaction conditions, one-way experiments were again carried out for validation, and the BISBC yield was as high as 75.32%.