Predictive Multi-scale Modeling of Shape-Selective Adsorption and Reaction in Acid/Base Zeolite Biofuel Catalysts

0932777 Auerbach智力优点：目标：PI将继续开发和应用理论化学方法，以帮助设计沸石作为生物燃料和生物产品催化剂。在以前的工作中，他模拟了含氮沸石X/Y/ZSM 5的光谱特征和形成/稳定性动力学，即，一些桥氧被桥胺（-NH-）基团取代的沸石-其显示出作为用于生物燃料生产的形状选择性碱催化剂的前景。在这项工作中，他将通过直接模拟酸性和碱性沸石X/Y/ZSM 5中羟醛缩合（碳-碳键形成反应）的尺寸和形状选择性来继续研究含氮沸石，以确定沸石化学如何影响催化剂的选择性和活性。在一个新的方向上，他将进行尖端建模，以研究在催化快速热解（CFP）的高温条件下这些沸石中的尺寸和形状选择性吸附，Huber已经展示了将纤维素直接转化为生物燃料的过程。他将量化沸石孔的大小和形状的热变形，以及这种变形如何影响相关生物饲料和生物燃料的吸附和扩散。方法：（i）羟醛缩合：PI将模拟糠醛（C5）和丙酮（C3）到C8产物（所谓的“单体”）的羟醛缩合。他还将模拟C8单体和糠醛到C13“二聚体”产物的额外缩合。这些反应是将生物质衍生的进料升级为汽油范围燃料的有前途的途径。他将学习如何通过计算中孔（ZSM 5）和大孔（X/Y）沸石中的反应途径来调整单体/二聚体选择性。他将学习如何通过模拟这些沸石的酸性和碱性版本中的这些反应来调节活性。电子能量将使用嵌入式簇（QM/MM）技术计算;复杂的反应途径将使用“攀爬图像轻推弹性带”方法发现，他最近用高斯计算化学程序以有效的方式实现了该方法。(ii)高温吸附：PI将执行周期性的电子结构计算与各种晶胞尺寸，以参数化一个新的力场，再现沸石热膨胀。使用这种新的力场，他将进行统计上严格的恒压模拟，以确定沸石变形如何适应相对较大的分子（如葡萄糖和左旋葡聚糖）的吸附，以及相对较大的物质（如萘）的形成。科学影响：PI对羟醛缩合的计算研究将揭示如何利用沸石催化剂的择形特性来生产所需长度的生物燃料。他的工作将直接影响，并将受益于与马萨诸塞大学的Huber小组的合作（见支持信），该小组正在实验研究这些相同的反应。他对高温吸附的建模将有助于解释CFP产品（如萘）是在沸石内部还是外部形成的，为进一步改进和优化CFP提供了必要的见解。该项目将直接影响并受益于我们与纽约州立大学斯托尼布鲁克的格雷小组的合作（见支持信），该小组正在使用X射线测量沸石膨胀。更广泛的影响：PI将继续招募代表性不足的学生参加这一计划，利用现有的NSF资助的REU和NEAGAP计划在麻省大学。他将继续与天才青年中心合作，利用生物燃料作为吸引年轻人的诱饵，参与中学外展活动。PI将在2009年秋季提供一门关于可再生能源的本科课程，其中生物燃料将发挥重要作用。与此同时，PI正在麻省大学领导一个委员会，以开发一个新的跨学科的浓度（如未成年人）对可再生能源。该提案将支持本科生研究作为可再生能源浓度的顶峰经验。

0932777 AuerbachIntellectual Merit: Objectives: The PI will continue developing and applying methods of theoretical chemistry to assist in the design of zeolites as biofuel and bioproduct catalysts. In previous work, he has modeled the spectroscopic signatures and formation/stability kinetics of nitrogen-containing zeolites X/Y/ZSM5 - i.e., zeolites with some bridging oxygens replaced with bridging amine (-NH-) groups - which show promise as shape-selective base catalysts for biofuel production. In this work he will continue study of nitrogen-containing zeolites by directly modeling size- and shape-selectivity of aldol condensation (a carbon-carbon bond forming reaction) in both acidic and basic zeolites X/Y/ZSM5, to identify how zeolite chemistry impacts catalyst selectivity and activity. In a new direction, he will perform cutting-edge modeling to investigate size- and shape-selective adsorption in these zeolites under the high-temperature conditions of catalytic fast-pyrolysis (CFP), a process that Huber has shown converts cellulose directly into biofuels. He will quantify thermal distortions of the sizes and shapes of zeolite pores, and how such distortions impact adsorption and diffusion of relevant biofeeds and biofuels. Approaches: (i) Aldol Condensation: The PI will model the aldol condensation of furfural (C5) and acetone (C3) to the C8 product (so-called "monomer"). He will also model an additional condensation of C8 monomer and furfural to a C13 "dimer" product. Such reactions are promising routes for upgrading biomass-derived feeds into gasoline-range fuels. He will learn how to tune the monomer/dimer selectivity by computing the reaction pathways in medium-pore (ZSM5) and large-pore (X/Y) zeolites. He will learn how to tune activities by modeling these reactions in both acidic and basic versions of these zeolites. Electronic energies will be computed using embedded cluster (QM/MM) techniques; complex reaction pathways will be discovered using the "climbing image nudged-elastic band" method, which he has recently implemented in an efficient way with the Gaussian computational chemistry program. (ii) High-temp Adsorption: The PI will perform periodic electronic structure calculations with various unit cell sizes to parameterize a new forcefield that reproduces zeolite thermal expansion. Using this new forcefield, he will perform statistically rigorous constant-pressure simulations to determine how zeolite distortions may accommodate the adsorption of relatively large molecules such as glucose and levoglucosan, and the formation of relatively large species such as naphthalene, during CFP. Scientific Impacts: The PI's computational studies of aldol condensation will shed light on how to exploit the shape-selective properties of zeolite catalysts to produce biofuels of desired lengths. His work will directly impact, and will benefit from, collaboration with the Huber group at UMass (see support letter), which is experimentally studying these same reactions. His modeling of high-temperature adsorption will help to explain whether CFP products such as naphthalene are formed inside or outside of zeolites, providing the insights necessary to further improve and optimize CFP. This project will directly impact, and benefit from, our collaboration with the Grey group at SUNY Stony Brook (see support letter), which is using X-rays to measure zeolite expansion. Broader Impacts: The PI will continue to recruit under-represented students to this program, exploiting existing NSF-funded REU and NEAGAP programs at UMass. He will continue to collaborate with the Center for Talented Youth to engage in middle-school outreach using Biofuels as the hook for young minds. The PI will deliver an undergraduate course on Renewable Energy in Fall 2009, in which Biofuels will play a prominent role. In parallel, the PI is leading a committee at UMass to develop a new interdisciplinary concentration (like a minor) on Renewable Energy. This proposal will support undergraduate research as a capstone experience of the Renewable Energy concentration.