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

智力优势：目标：PI将继续发展和应用理论化学方法，以协助设计作为生物燃料和生物产品催化剂的沸石。在之前的工作中，他模拟了含氮沸石X/Y/ZSM5的光谱特征和形成/稳定性动力学，即一些桥接氧被桥接胺（- nh -）取代的沸石，它有望成为生物燃料生产的形状选择性碱催化剂。在这项工作中，他将继续研究含氮沸石，通过直接模拟酸性和碱性沸石X/Y/ZSM5中醛醇缩合（碳-碳键形成反应）的尺寸和形状选择性，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，他将进行尖端的建模来研究这些沸石在催化快速热解（CFP）的高温条件下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。他将量化沸石孔隙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)醛醇缩合：PI将模拟醛醇缩合糠醛（C5）和丙酮（C3）到C8产物（所谓的“单体”）。他还将模拟C8单体和糠醛生成C13“二聚体”的额外缩合反应。这样的反应很有希望将生物质原料升级为汽油燃料。他将学习如何通过计算中孔（ZSM5）和大孔（X/Y）沸石的反应途径来调整单体/二聚体的选择性。他将学习如何通过在这些沸石的酸性和碱性版本中模拟这些反应来调节活动。电子能量将使用嵌入式簇（QM/MM）技术计算；他最近用高斯计算化学程序以一种有效的方式实现了“爬升图像轻推弹性带”方法，以发现复杂的反应途径。（ii）高温吸附：PI将以不同的单元胞大小进行周期性的电子结构计算，以参数化重现沸石热膨胀的新力场。利用这个新的力场，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CFP过程中相对大分子（如葡萄糖和左旋葡聚糖）的吸附，以及相对大分子（如萘）的形成。科学影响：PI对醛醇缩合的计算研究将揭示如何利用沸石催化剂的形状选择特性来生产所需长度的生物燃料。他的工作将直接影响并受益于与麻省理工大学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。他的高温吸附模型将有助于解释CFP产物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石溪分校Grey小组的合作（见支持信），该小组使用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该项目，利用现有的nsf资助的REU和NEAGAP项目。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纽带，在中学开展推广活动。该学院将于2009年秋季开设一门关于可再生能源的本科课程，生物燃料将在其中扮演重要角色。与此同时，PI正在领导麻省理工学院的一个委员会，开发一个新的跨学科的可再生能源专业（如辅修）。该提案将支持作为可再生能源集中的顶点经验的本科生研究。

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.