Synthesis of an Immobilized Brönsted Acidic Ionic Liquid Catalyst and Hydrolysis of Cellulose in Water Under Mild Conditions

A Brönsted acidic ionic liquid catalyst with a sulfonic acid group tethered to imidazolium cation, and immobilized on polystyrene was prepared by a two step method in 83% overall yield. This immobilized Brönsted acidic ionic liquid catalyst was shown to be a significantly better catalyst than H+ form of Dowex-50X8 of similar SO3H group loading for hydrolysis of untreated Sigmacell cellulose (DP ~ 450) in water under hydrothermal conditions. For example cellulose hydrolyzed with immobilized Brönsted acidic ionic liquid catalyst produced 50.1 % yield of total reducing sugars (TRS) after 3 hr, at 160 °C, whereas sample heated with Dowex-50X8 produced only 9.2 % TRS yield under identical conditions. Similarly, cellulose hydrolysis using immobilized ionic liquid catalyst produced a maximum glucose yield of 21.7% after 3 hr, at 160 °C, while the maximum glucose yield with Dowex-50X8 catalyst was 4.5 %, which was achieved after 3 hr, at 170 °C. This enhancement in catalytic activity is explained as a result of an interaction between cellulose, and immobilized imidazolium ionic liquid structure with chloride anion. Keywords: Cellulose, hydrolysis, Acidic ionic liquid, Saccharification, Solid acid catalyst.