International Research Fellowship Program: Computer-Aided Molecular Design of Ionic Liquids for the Pretreatment of Cellulose

1006204 Weis国际研究奖学金计划使美国科学家和工程师能够在国外进行9至24个月的研究。该项目的奖项提供了联合研究的机会，并利用国外独特或互补的设施、专业知识和实验条件。该奖项将支持德里克·韦斯博士与澳大利亚莫纳什大学的道格·麦克法兰博士和美国阿拉巴马大学的罗宾·罗杰斯博士合作的为期24个月的研究奖学金。纤维素是一种丰富的可再生资源，可从植物中获得，可转化为乙醇并帮助取代化石燃料。纤维素的潜在饲料储备包括玉米秸秆和甘蔗渣等废品，或者种植特定作物的秋刀草以备收获。目前，纤维素乙醇的成本太高，无法实际考虑。环境友好的溶剂被称为离子液体，已经被确定为纤维素乙醇生产中的一个预处理步骤，通过使酶更容易将生物质分解为可发酵的糖来降低成本。离子液体可以正式定义为在100℃以下熔化的盐，通常由带正电荷的有机阳离子和带负电荷的阴离子组成。根据所选择的阳离子/阴离子，可以针对特定的应用微调溶剂化性质。近年来，离子液体因具有开发环境友好型溶剂的潜力而备受关注。一些有利的特性包括可以忽略的蒸汽压、不可燃性和热稳定性。可以忽略的蒸汽压是一个重要的特征，因为与传统溶剂释放的烟雾相比，呼吸问题的风险降低了。对于工业应用，还可以节省成本，因为可以将离子液体与工艺中的其他组分分离和回收。开发用于前处理步骤的更有效的离子液体的一些重要性质包括熔点、粘度和纤维素的溶解度。出于工艺操作方面的考虑，熔点和粘度都是必不可少的。例如，离子液体必须在所需温度下以液体形式存在。还可以通过专门设计低熔点的离子液体来节约能量，因为不需要大量的热量。以类似的方式，低粘度的离子液体将需要更少的能量来泵送和运输。计算机辅助分子设计(CAMD)技术正在被应用于帮助识别潜在的具有良好性能的新型离子液体，以便更有效地进行纤维素预处理。应用这种方法要快得多，成本更低，并允许更全面地寻找最合适的候选人。目前，具有纤维素溶解度数据的文献中只有有限数量的离子液体，因此，对于所需的应用，几乎没有选择。CAMD技术有助于从众多可用的阳离子/阴离子对组合中选择潜在的离子液体进行实验室合成和测试。

1006204WeisThe International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-four month research fellowship by Dr. Derick Weis to work with Dr. Doug MacFarlane at Monash University in Australia and in the U.S. with Dr. Robin Rogers at the University of Alabama.Cellulose is an abundant, renewable resource available from plants that can be turned into ethanol and help replace fossil fuels. Potential feed stocks for cellulose include waste products like corn stover and sugar cane bagasse, or planting a specific crop of switch grass for harvest. Currently, the cost of cellulosic ethanol is too high for practical consideration. Environmentally friendly solvents, known as ionic liquids, have been identified for a pretreatment step in the production of cellulosic ethanol as a way to reduce the cost by making it easier for enzymes to break down biomass into fermentable sugars. Ionic liquids can be formally defined as salts that melt below 100 oC, and generally consist of a positively charged organic cation with a negatively charged anion. The solvation properties can be fine-tuned for particular applications depending on the cation/anion chosen. In recent years, ionic liquids have received a lot of focus because of the potential to develop environmentally friendly solvents. Some of the favorable characteristics include negligible vapor pressure, non-flammability, and thermal stability. The negligible vapor pressure is an important feature because of the reduced risk of respiratory problems compared to the fumes given off from traditional solvents. There is also a cost savings for industrial applications because it is possible to separate and recycle ionic liquids from other components in the process. Some important properties for developing more effective ionic liquids to be used in a pretreatment step include melting point, viscosity, and cellulose solubility. Both melting point and viscosity are essential because of process operating considerations. For example, the ionic liquid must be present in liquid form at the required temperature. Energy can also be conserved by specifically designing ionic liquids with a low melting point because a significant amount of heat will not be necessary. In a similar manner, ionic liquids with low viscosity will require less energy to pump and transport.A computer-aided molecular design (CAMD) technique is being applied to help identify potentially new ionic liquids with favorable properties for more effective cellulose pretreatment. Applying this approach is much quicker, less expensive and allows for a more comprehensive search for the most suitable candidates. Currently, there are only a limited number of ionic liquids in the literature with cellulose solubility data, and thus, few options exist for the desired application. The CAMD technique helps to select potential ionic liquids for synthesis and testing in the laboratory from the numerous combinations of cation/anion pairs available.