EAGER: Permeability of Biomass and Impact of Transport on Reaction Rates Under Supercritical Carbon Dioxide Treatment

生物质具有取代石油作为燃料和化学品原料的巨大潜力，但需要开发低成本和环境友好的生物质转化工艺。生物质转化过程涉及复杂的化学和传输现象。超临界状态下的二氧化碳已显示出作为预处理和直接提取生物质制备高价值化学品的溶剂的前景。这种方法的一个限制是转换效率低。在不同的研究中也有不一致的结果，这些结果归因于生物量密度和形态的差异等因素。该项目将研究超临界二氧化碳处理前后生物质内的传质限制，以了解这些限制对转化率和程度的影响。该项目将推进超临界二氧化碳处理作为生产高价值化学品的有效生物质转化策略的可行性。这项工作还将促进研究与生物质转化相关的化学动力学和传输现象的新工具的发展。在超临界二氧化碳处理过程中，生物质组成和形态的演变对转化程度和效率的重要性知之甚少。该项目的目的是研究超临界二氧化碳处理过程中生物质形态的演变，以评估传质在半纤维素、纤维素和木质素转化中的作用。这一目标将通过使用现有技术和开发新技术，通过实验表征不断变化的生物量形态和处理时间来实现。具体来说，将获得新的见解生物量形态的演变为一系列生物量结构，密度和颗粒大小。使用超临界二氧化碳与环境友好的共溶剂，如水，已被证明是有效的水解生物质聚合物通过形成碳酸。因此，研究将集中在这种共溶剂系统上，研究结果将被纳入一个模型，该模型考虑了水解化学和生物质形态的演变，以描述转化过程。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Biomass has vast potential to replace petroleum as a feedstock for fuels and chemicals, but low cost and environmentally-friendly processes for biomass conversion need to be developed. Biomass conversion processes involve complex chemistry and transport phenomena. Carbon dioxide at supercritical states has shown promise as a solvent for pretreatment and direct extraction of biomass to high-value chemicals. One limitation of this approach is low conversion efficiency. There are also inconsistent results across different studies which have been attributed to, among other factors, differences in the density and morphology of the biomass. This project will investigate mass transfer limitations within the biomass before and after supercritical carbon dioxide treatment to understand the impact of these limitations on conversion rates and extents. This project will advance the viability of supercritical carbon dioxide treatment as an effective biomass conversion strategy to produce high value chemicals. This work will also facilitate the development of new tools for studying chemical kinetics and transport phenomena associated with biomass conversion.The evolution of biomass composition and morphology during supercritical carbon dioxide treatment is poorly understood, despite their demonstrated importance to conversion extent and efficiency. The objective of this project is to investigate the evolution of biomass morphology during supercritical carbon dioxide treatment in order to assess the role of mass transfer in the conversion of hemicellulose, cellulose and lignin. This objective will be achieved through experimental characterization of evolving biomass morphology with treatment duration through the use of established techniques and the development of novel techniques. Specifically, new insights into the evolution of biomass morphology for a range of biomass structures, densities and particle sizes will be gained. The use of supercritical carbon dioxide with environmentally benign co-solvents, such as water, has been shown to be effective at hydrolysis of biomass polymers via the formation of carbonic acid. Thus, research will focus on this co-solvent system and results will be incorporated into a model that accounts for hydrolysis chemistry and evolving biomass morphology to describe the conversion process.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.