ORALS

Depolymerization of cellulosic biomass to sugars is a challenging step and is the primary obstacle for the large scale processing of cellulosic biomass to biofuels and renewable feedstocks. Ionic liquids are well known for their ability to dissolve cellulose and our interest in the search for efficient catalytic methods for saccharification of polysaccharides has led us to develop –SO₃H group functionalized Brønsted acidic ionic liquids (BAILs) as solvents as well as catalysts [1]. Later we found that these sulfuric acid derivatives can be used as catalysts in aqueous phase as well. For example, BAIL 1-(1-propylsulfonic)-3-methylimidazolium chloride aqueous solution was shown to be a better catalyst than H₂SO₄ of the same [H⁺] for the degradation of cellulose [2]. This observation is an important lead for the development of a BAIL based cellulase mimic type catalyst for depolymerization of cellulose [3]. In an attempt to develop recyclable, simple enzyme mimic type catalysts, we have studied quantitative structure activity relationships (QSAR) of a series of BAIL catalysts and found that activity with different cation types decreases in the order: imidazolium > pyridinium > triethanol ammonium [4]. Furthermore, we have investigated the effects of selected metal ions on 1-(1-propylsulfonic)-3-methylimidazolium chloride BAIL catalyzed hydrolysis of cellulose in water at 140-170 °C. The total reducing sugar (TRS) yields produced during the hydrolysis of cellulose (DP ~ 450) in aq. 1-(1-propylsulfonic)-3-methylimidazolium chloride solution at 140 - 170 °C using Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺ Ni²⁺, Cu²⁺, Zn²⁺, and La³⁺ chlorides as co-catalysts were studied. Cellulose samples heated with Mn²⁺, Fe³⁺, Co²⁺ as co-catalysts produce significantly higher TRS yields compared to the sample heated without the metal ions. The highest catalytic effect enhancement is observed with Mn²⁺ and produced TRS yields of 59.1, 78.4, 91.8, and 91.9 % at 140, 150, 160, and 170 °C respectively, whereas cellulose hydrolyzed without Mn²⁺ produced TRS yields of 9.8, 16.5, 28.0, and 28.7 % at the same four temperatures. This is a 503, 375, 228, and 220 % enhancement in TRS yield due to the addition of Mn²⁺ as a co-catalyst to BAIL catalyzed cellulose hydrolysis at 140, 150, 160 and 170°C respectively. This paper will present the development of BAIL based artificial cellulase type catalysts, QSAR studies, catalyst immobilizations, applications on lignocellulosic biomass materials (corn stover, switchgrass, poplar) and recycling studies.

References:
1. A.S. Amarasekara et al., Ind. Eng. Chem. Res., 2009, 48(22), 10152.
2. A.S. Amarasekara et al., Ind. Eng. Chem. Res., 2011, 50(21), 12276.
3. A.S. Amarasekara et al., Cat.. Sci. Tech., 2016, 6, 426.
4. A.S. Amarasekara et al., Sustain. Energ., 2014, 2(3), 102.