Br？nsted acidic ionic liquid 1-(1-propylsulfonic)-3-methylimidazolium chloride (PSMIMCl) shows a higher catalytic activity than sulfuric acid in the hydrolysis of D-cellobiose to D-glucose in water at 90–120°C. This catalytic activity enhancement is more significant at higher temperatures, and at 120°C, PSMIMCl produced 64.5% glucose yield, whereas H2SO4 produced only 42.2% after 40？min. reaction, and this is a 52.8% enhancement of catalytic activity due to the alkylimidazolium group attached to the sulfonic acid group. 1H NMR monitoring of the D-cellobiose hydrolysis in PSMIMCl and sulfuric acid mediums failed to reveal intermediates in the hydrolysis reaction, and this is probably due to rapid conversion of the intermediate(s) to a mixture of D-glucose anomers with . 1. Introduction Hydrolysis of lignocellulosic biomass to fermentable sugars is an essential step in the production of cellulosic-ethanol and is the most challenging step in the whole process [1–5]. Enzymatic hydrolysis is the widely used technology in current pilot plants, but this method requires a drastic pretreatment at high temperature and pressure to disrupt the strong hydrogen bonding network in cellulose, before exposure to the enzyme. Furthermore, commercialization of the enzymatic process is hindered by the prohibitive cost of the currently available enzyme preparations as well [6]. As an alternative to the enzymatic methods, dilute aqueous solution of sulfuric acid can also be used as a catalyst for the direct hydrolysis of cellulose at high temperature and pressure. Even though, the direct dilute acid saccharification gives lower sugar yields compared to enzymatic saccharification, a number of research groups have taken an interest in this old process [7–9] taking a second look at this technology due to its simplicity, and lower cost when compared to enzymatic saccharification, which anyhow requires an energy consuming pretreatment. Ionic liquids are well known for their unique combination of attractive properties and as green solvents for numerous applications, but currently there is a marked interest in using ionic liquids in a number of other functions such as electrolytes [10], polymeric materials [11, 12], and catalysts [13]. In addition to this, 2002 discovery [14] of the use of ionic liquids as a cellulose dissolving solvent has sparked a new field of research on the use of ionic-liquid-based systems for the depolymerization of cellulose. The initial efforts in this direction were reported by Li et al. in 2007, where they published the use of catalytic amount of H2SO4
References
[1]
J. Goettemoeller and A. Goettemoeller, Sustainable Ethanol: Biofuels, Biorefineries, Cellulosic Biomass, Flex-fuel Vehicles, and Sustainable Farming for Energy Independence, Prairie Oak, Maryville, Mo, USA, 2007.
[2]
R. Katzen and D. J. Schell, Biorefineries—Industrial Processes and Products, vol. 1, Wiley-VCH, Weinheim, Germany, 2006, edited by B. Kamm, P.R. Gruber, M. Kamm.
[3]
C. Wyman, Handbook on Bioethanol: Production and Utilization, Taylor & Francis, Washington, DC, USA, 1996.
[4]
G. W. Huber, S. Iborra, and A. Corma, “Synthesis of transportation fuels from biomass: chemistry, catalysts, and engineering,” Chemical Reviews, vol. 106, no. 9, pp. 4044–4098, 2006.
[5]
M. Balat and H. Balat, “Recent trends in global production and utilization of bio-ethanol fuel,” Applied Energy, vol. 86, no. 11, pp. 2273–2282, 2009.
[6]
R. K. Sukumaran, R. R. Singhania, G. M. Mathew, and A. Pandey, “Cellulase production using biomass feed stock and its application in lignocellulose saccharification for bio-ethanol production,” Renewable Energy, vol. 34, no. 2, pp. 421–424, 2009.
[7]
P. Lenihan, A. Orozco, E. O'Neill, M. N. M. Ahmad, D. W. Rooney, and G. M. Walker, “Dilute acid hydrolysis of lignocellulosic biomass,” Chemical Engineering Journal, vol. 156, no. 2, pp. 395–403, 2010.
[8]
G. Sanchez, L. Pilcher, C. Roslander, T. Modig, M. Galbe, and G. Liden, “Dilute-acid hydrolysis for fermentation of the Bolivian straw material Paja Brava,” Bioresource Technology, vol. 93, no. 3, pp. 249–256, 2004.
[9]
Q. Xiang, Y. Y. Lee, and R. W. Torget, “Kinetics of glucose decomposition during dilute-acid hydrolysis of lignocellulosic biomass,” Applied Biochemistry and Biotechnology, vol. 113, pp. 1127–1138, 2004.
[10]
T. Sato, S. Marukane, T. Narutomi, and T. Akao, “High rate performance of a lithium polymer battery using a novel ionic liquid polymer composite,” Journal of Power Sources, vol. 164, no. 1, pp. 390–396, 2007.
[11]
A. S. Amarasekara and P. Shanbhag, “Synthesis and characterization of polymeric ionic liquid poly(imidazolium chloride-1,3-diylbutane-1,4-diyl),” Polymer Bulletin, vol. 67, no. 4, pp. 623–629, 2011.
[12]
A. S. Amarasekara, B. Callis, and B. Wiredu, “Synthesis and characterization of branched polymeric ionic liquids with imidazolium chloride segments,” Polymer Bulletin, vol. 68, no. 4, pp. 901–908, 2011.
[13]
H. Olivier-Bourbigou, L. Magna, and D. Morvan, “Ionic liquids and catalysis: recent progress from knowledge to applications,” Applied Catalysis A, vol. 373, no. 1-2, pp. 1–56, 2010.
[14]
R. P. Swatloski, S. K. Spear, J. D. Holbrey, and R. D. Rogers, “Dissolution of cellose with ionic liquids,” Journal of the American Chemical Society, vol. 124, no. 18, pp. 4974–4975, 2002.
[15]
C. Li and Z. K. Zhao, “Efficient acid-catalyzed hydrolysis of cellulose in ionic liquid,” Advanced Synthesis and Catalysis, vol. 349, no. 11-12, pp. 1847–1850, 2007.
[16]
C. Li, Q. Wang, and Z. K. Zhao, “Acid in ionic liquid: an efficient system for hydrolysis of lignocellulose,” Green Chemistry, vol. 10, no. 2, pp. 177–182, 2008.
[17]
R. Rinaldi, R. Palkovits, and F. Schüth, “Depolymerization of cellulose using solid catalysts in ionic liquids,” Angewandte Chemie—International Edition, vol. 47, no. 42, pp. 8047–8050, 2008.
[18]
Z. Zhang and Z. K. Zhao, “Solid acid and microwave-assisted hydrolysis of cellulose in ionic liquid,” Carbohydrate Research, vol. 344, no. 15, pp. 2069–2072, 2009.
[19]
S. J. Kim, A. A. Dwiatmoko, J. W. Choi, Y. W. Suh, D. J. Suh, and M. Oh, “Cellulose pretreatment with 1-n-butyl-3-methylimidazolium chloride for solid acid-catalyzed hydrolysis,” Bioresource Technology, vol. 101, no. 21, pp. 8273–8279, 2010.
[20]
A. S. Amarasekara and O. S. Owereh, “Synthesis of a sulfonic acid functionalized acidic ionic liquid modified silica catalyst and applications in the hydrolysis of cellulose,” Catalysis Communications, vol. 11, no. 13, pp. 1072–1075, 2010.
[21]
A. S. Amarasekara and O. S. Owereh, “Hydrolysis and decomposition of cellulose in bron？sted acidic ionic liquids under mild conditions,” Industrial and Engineering Chemistry Research, vol. 48, no. 22, pp. 10152–10155, 2009.
[22]
A. S. Amarasekara and B. Wiredu, “Degradation of cellulose in dilute aqueous solutions of acidic ionic liquid 1-(1-propylsulfonic)-3-methylimidazolium chloride, and p-toluenesulfonic acid at moderate temperatures and pressures,” Industrial and Engineering Chemistry Research, vol. 50, no. 21, pp. 12276–12280, 2011.
[23]
A. A. Dwiatmoko, J. W. Choi, D. J. Suh, Y.-W. Suh, and H. H. Kung, “Understanding the role of halogen-containing ionic liquids in the hydrolysis of cellobiose catalyzed by acid resins,” Applied Catalysis A, vol. 387, no. 1-2, pp. 209–214, 2010.
[24]
Q. Yang, Z. Wei, H. Xing, and Q. Ren, “Br？nsted acidic ionic liquids as novel catalysts for the hydrolyzation of soybean isoflavone glycosides,” Catalysis Communications, vol. 9, no. 6, pp. 1307–1311, 2008.
[25]
G. Y. Zhu, R. Wang, G. H. Liu, L. Q. Xu, B. Zhang, and X. Q. Wu, “Synthesis of multi-hydroxyl and sulfonyl dual-functionalized room temperature ionic liquids,” Chinese Chemical Letters, vol. 18, no. 6, pp. 633–635, 2007.
[26]
H. U. Bergmeyer and E. Bernt, “Glucose determination with glucose oxidase and peroxidase,” in Methods of Enzymatic Analysis, H. U. Bergmeyer, Ed., pp. 1205–1212, Academic Press, New York, NY, USA, 1974.
[27]
D. A. T. Southgate, Determination of Food Carbohydrates, Applied Science Publishers, London, UK, 1961.
[28]
L. Kupiainen, J. Ahola, and J. Tanskanen, “Comparison of formic and sulfuric acids as a glucose decomposition catalyst,” Industrial and Engineering Chemistry Research, vol. 49, no. 18, pp. 8444–8449, 2010.
[29]
J. L. Oscarson, R. M. Izatt, P. R. Brown, Z. Pawlak, S. E. Gillespie, and J. J. Christensen, “Thermodynamic quantities for the interaction of with and in aqueous solution from 150 to 320°C,” Journal of Solution Chemistry, vol. 17, no. 9, pp. 841–863, 1988.
[30]
J. Zhang, H. Zhang, J. Wu, J. Zhang, J. He, and J. Xiang, “NMR spectroscopic studies of cellobiose solvation in EmimAc aimed to understand the dissolution mechanism of cellulose in ionic liquids,” Physical Chemistry Chemical Physics, vol. 12, no. 8, pp. 1941–1947, 2010.
[31]
Q. Xiang, Y. Y. Lee, and R. W. Torget, “Kinetics of glucose decomposition during dilute-acid hydrolysis of lignocellulosic biomass,” Applied Biochemistry and Biotechnology A, vol. 115, no. 1–3, pp. 1127–1138, 2004.
[32]
X. Huang, H. Duan, and S. A. Barringer, “Effects of buffer and temperature on formation of furan, acetic acid and formic acid from carbohydrate model systems,” LWT—Food Science and Technology, vol. 44, no. 8, pp. 1761–1765, 2011.
[33]
M. U. Roslund, P. T？htinen, M. Niemitz, and R. Sj？holm, “Complete assignments of the 1H and 13C chemical shifts and coupling constants in NMR spectra of D-glucopyranose and all D-glucopyranosyl-D-glucopyranosides,” Carbohydrate Research, vol. 343, no. 1, pp. 101–112, 2008.
