Synthesis and characterization of new low-cost ILs based on butylammonium cation and application to lignocellulose hydrolysis

• Synthesis of new low cost ionic liquid and application in coir fiber treatment for bioethanol production.
• Determination of the best conditions for acid hydrolysis of coir fiber.
• Efficiency of the acid hydrolysis of coir fiber after treatment with ionic liquid.

Fourteen ionic liquids (ILs) were obtained and characterized by nuclear magnetic resonance and infra-red spectroscopy. One of these liquids, n-butylammonium acetate, was used in the treatment of coir fiber prior to acid hydrolysis. For this purpose, the fiber was pulped with 8% (w/w) sodium hydroxide for 6 h under 2.5 atm pressure at 137 °C and then treated with IL for 2 h at 90 °C. The samples were hydrolyzed in acetic acid at different concentrations and temperatures. The reducing sugar concentrations were determined in all samples, and the optimal hydrolysis conditions were established (32.2% acetic acid at 122.4 °C). The reaction time was also studied, and the conversion was maximized at 3 h. Under the best hydrolysis conditions, crude fiber, pulping fiber, and IL-treated fiber were hydrolyzed to yield 8.53%, 47.58%, and 89.75% of reducing sugars, respectively.