The Emergent Behavior of Solid Nanoparticles at Oil-Water Interfaces: A Multi-Scale Thermodynamic Approach to Enable Bio-Oil Upgrade

这个与能源相关的项目源于俄克拉荷马大学Daniel Resasco研究小组最近报告的一项改变范式的概念验证结果[Science 327(2010)68]。实验结果表明，当固体颗粒同时用于稳定油包水乳状液和负载多相催化剂时，可以实现生物油(木质纤维生物质的热解产物)的原位升级。所使用的固体颗粒是通过将二氧化硅颗粒熔融在碳纳米管上而获得的杂化材料。为了将这一概念证明推广到大规模工业应用中，有必要设计出更简单、更便宜的颗粒，以稳定水包油乳状液并支持催化剂。有必要了解表征固体颗粒的分子水平特征如何决定液滴的大小和形状等宏观性质，以及液滴合并的机制。还希望在生物油升级完成后可以回收颗粒。众所周知，固体颗粒吸附在水-油界面上，减小了两不相容相之间的接触面积。当颗粒在界面上强烈吸附时，可以得到稳定的乳状液。通过添加适当的表面活性化合物，粒子可以很容易地从界面上释放出来，这是有可能的。一旦进入连续相，颗粒就会聚集在一起，便于回收。这些质量预期的量化将改变生物能源领域。实验证据表明，颗粒在界面上的行为强烈地依赖于颗粒密度(突现行为的特征)。为了使这些实验观察合理化，并能够在工业规模上实现就地生物油升级的潜在变革性，需要一个多尺度热力学模型来将分子水平的性质与宏观观察联系起来。智力优势：该提议的科学目标在于发展一个多尺度理论模型，基于全原子和粗颗粒水平的模拟，以阐明吸附在水正十烷界面上的纳米颗粒的紧急行为。感兴趣的纳米颗粒包括二氧化硅(球形和盘状)和氧化镁(立方体)。为了稳定油水乳状液，这些颗粒被功能化，使其部分疏水。具有均匀表面性质的纳米粒子以及部分表面疏水和部分亲水的Janus纳米粒子将被研究。更广泛的影响：在此建议中得出的理论模型将使我们能够更好地理解和预测固体粒子稳定乳液的性质。这些乳液正在新材料的制造、聚合物泡沫的稳定以及食品科学中找到技术应用。了解粒子在界面上的堆积，以及导致奇异的二维相出现的驱动力，对于聚合物纳米复合材料的制造也很感兴趣，这种材料正在开发的应用包括收集太阳能。推广和教育：该项目将涉及一名研究生和三名本科生研究人员。有代表性的少数族裔，特别是女性和美洲原住民，将参加我们的活动。与拥有大量美国原住民学生的大学(特别是位于俄克拉荷马州塔赫勒夸市的东北州立大学)建立了联系。本文提出的研究活动将有助于吸引高中生投身STEM职业，特别是在俄克拉何马州，该州的经济传统上依赖能源生产和利用。为了实现这一目标，诺曼高中中学科学教师大卫·阿斯基先生的合作得到了保障。该项目的资助使研究人员能够继续每年在诺曼高中举办一次研讨会。

1033129StrioloThis energy related project stems from a recent paradigm-changing proof-of-concept result reported by the research group of Daniel Resasco at the University of Oklahoma [Science 327 (2010) 68]. The experimental results showed that it is possible to perform in-situ upgrade of bio-oil (the pyrolisis product of lignocellulosic biomass) when solid particles are used to both stabilize water-in-oil emulsions and support heterogeneous catalysts. The solid particles used were hybrid materials obtained by fusing silica particles on carbon nanotubes. To generalize this proof of concept to large-scale industrial applications it is necessary to design simpler and cheaper particles that stabilize oil-in-water emulsions and support the catalysts. It is necessary to understand how the molecular level features characterizing the solid particles determine macroscopic properties such as drop size and shape, as well as the mechanism of droplets coalescence. It is also desirable that the particles can be recovered after the bio-oil upgrade is complete. It is well known that solid particles adsorb at water-oil interfaces to reduce the contact area between the two immiscible phases. Stable emulsions are obtained when the particles strongly adsorb at the interfaces. It is plausible that by adding appropriate surface-active compounds the particles can be easily released from the interfaces. Once in the continuous phase, the particles tend to agglomerate, facilitating their recovery. Quantification of these qualitative expectations will transform the bio-energy field. Experimental evidence shows that particles behavior at interfaces strongly depends on the particle density (a signature of emergent behavior). In order to rationalize these experimental observations and to enable the potentially transformative implementation of in-situ bio-oil upgrade at the industrial scale, a multi-scale thermodynamic model is required to link molecular-level properties to macroscopic observations.Intellectual Merit: The scientific goal of this proposal consists in the development of a multi-scale theoretical model, based on simulations at all-atom and coarse grained levels, to elucidate the emergent behavior of nanoparticles adsorbed at water decane interfaces. Nanoparticles of interest include silica (spherical and discoid) and MgO (cubic) ones. To stabilize water-oil emulsions, these particles are functionalized to become partially hydrophobic. Nanoparticles with uniform surface properties, as well as Janus nanoparticles in which part of the surface is hydrophobic and part of it is hydrophilic will be studied.Broader impacts: The theoretical model derived within this proposal will allow us to better understand and predict the properties of solid particle stabilized emulsions. These emulsions are finding technological applications in the manufacture of new materials, in the stabilization of polymeric foams, and also in food science. Understanding the packing of particles at interfaces, and the driving forces responsible for the appearance of exotic two-dimensional phases is also of interest for the manufacture of polymeric nanocomposite materials, which are being developed for, among other applications, harvesting solar energy.Outreach and Education: The project will involve one graduate student and three undergraduate researchers. Under represented minorities, especially females and Native Americans, will participate in our activities. Connections with colleges with significant Native American student population (specifically Northeastern State University in Tahlequah, OK) have been established. The research activities proposed herein will contribute to attract high-school students towards STEM careers, especially in Oklahoma, a state whose economy has traditionally relied on energy production and utilization. Towards this goal, the collaboration of Mr. David Askey, secondary science teacher at Norman High School, has been secured. Funding of this project allows the investigators to continue delivering seminars at Norman High School once a year.