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

[1033129]这个与能源相关的项目源于俄克拉何马大学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，利用固体颗粒稳定油包水乳状液并支持多相催化剂，可以实现生物油（木质纤维素生物质的热解产物）的原位升级。所使用的固体颗粒是通过在碳纳米管上融合二氧化硅颗粒而得到的杂化材料。为了将这一概念推广到大规模的工业应用中，有必要设计更简单、更便宜的颗粒来稳定水包油乳液并支持催化剂。有必要了解表征固体颗粒的分子水平特征如何决定液滴大小和形状等宏观性质，以及液滴聚结机制。还希望在生物油升级完成后可以回收颗粒。众所周知，固体颗粒在水-油界面吸附，以减少两种不混相之间的接触面积。当颗粒在界面处强烈吸附时，得到稳定的乳剂。通过添加适当的表面活性化合物，颗粒可以很容易地从界面中释放出来。一旦进入连续阶段，颗粒倾向于凝聚，有利于它们的回收。这些定性期望的量化将改变生物能源领域。实验证据表明，粒子在界面上的行为强烈依赖于粒子密度（紧急行为的一个特征）。为了使这些实验观察合理化，并使生物油原位升级在工业规模上的潜在变革性实施成为可能，需要一个多尺度热力学模型将分子水平的性质与宏观观察联系起来。智力优势：本提案的科学目标在于建立一个基于全原子和粗粒度水平模拟的多尺度理论模型，以阐明纳米颗粒在水-烷基界面吸附的紧急行为。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）纳米颗粒。为了稳定水-油乳液，这些颗粒被功能化成部分疏水性。将研究具有均匀表面特性的纳米粒子，以及表面部分疏水和部分亲水的Janus纳米粒子。更广泛的影响：本提案中导出的理论模型将使我们能够更好地理解和预测固体颗粒稳定乳液的性质。这些乳剂在新材料的制造、聚合物泡沫的稳定以及食品科学中得到了技术应用。了解颗粒在界面上的堆积，以及导致奇异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有意义，这种材料正在开发中，在其他应用中，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。代表性不足的少数民族，特别是女性和印第安人，将参与我们的活动。与拥有大量美国原住民学生的大学（特别是位于OK州塔勒夸的东北州立大学）建立了联系。本文提出的研究活动将有助于吸引高中生从事STEM职业，特别是在俄克拉荷马州，这个州的经济传统上依赖于能源生产和利用。为了实现这一目标，诺曼高中的中学科学老师大卫·阿斯基先生的合作已经得到了保障。该项目的资金允许研究人员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.