Research On Br(?)nsted Acidic Ionic Liquids-catalyzed Dehydrative Formation Of Isosorbide From Sorbitol

Isosorbide is one of the most high-value chemicals arising from biomass transformation.It is generally produced by dehydration of sorbitol using sulphuric acid as a catalyst,but suffering serious problems such as environmental pollution,significant handling risk,corrosive nature of catalyst and stability issues of products.Br???nsted acidic ionic liquids?BILs?,by introducing Br???nsted substituents into the cation/anion of the ionic liquids?ILs?,have flexible acidity,low vapour pressure,good thermal stability,and simple functionality.BILs have attracted special attention as efficient catalysts for the synthesis of valuable chemicals.Here,SO3H-based Br???nsted ionic liquid has been employed as catalysts in solvent free dehydration of sorbitol to isosorbide for the first time,which provides an efficient,novel and reusable catalysts.A series of BILs was accordingly synthesized as the catalysts candidates.The quality of BILs under study was characterized by a combination of NMR spectroscopy,Karl Fisher titration,acid-base titration,ESI detection,and TGA analysis.Their moisture concentration(?^H₂O:nwater/n?)is controlled less than 2 × 10^-3.Within this standard,the variation of behavior arising from different amount of H2O content could be neglected.The ionic liquids structure was studied using 1H NMR,revealing the acquisition ultrapure ionic liquids and the existence of hydrogen-bonded clusters.Acidity,quantified by Gutmann Acceptor Number?AN?,was found closely related to the liquid structure.Thermo gravimetric analysis?TGA?was indicating these BILs are thermally stable?Td>300 ??enough for catalytic conversion of sorbitol to isosorbide.The structure-performance relationship of SO3H-based Br???nsted ionic liquid has been investigated.The dehydration reaction rate depended on two factors:acidity?expressed as AN value?and stability?stability of SO3-H?H2O?···SO3CF3 in vacuum during dehydration?of Br???nsted Acidic Ionic Liquid catalyst.The reaction kinetics was experimentally determined for different temperature ranges and described by means of first order kinetic model and the Michaelis-Menten type mechanism kinetic model.Process simulations were subsequently conducted for a continuous stirred tank reactor?CSTR?by Aspen software based on these kinetic data.And the balance yield value of 82%was obtained.