New Methods for Predicting Mechanisms for Complex Heterogeneous Catalysts with Applications to Metal Oxide Functionalization of Alkanes

预测复杂多相催化剂机理的新方法及其在烷烃金属氧化物官能化中的应用

• 批准号: 1214158
• 负责人: William Goddard
• 金额: $ 39万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-06-01 至 2016-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1214158&HistoricalAwards=false
• 关键词: New; Methods; Predicting; Mechanisms; Complex

With this award from the Chemical Catalysis Program of the Chemistry Division, Professor William A. Goddard and colleague Robert Nielsen from the Departments of Chemistry and Chemical Engineering at the California Institute of Technology will develop and apply reactive force field (ReaxFF), through Monte Carlo (MC) and molecular dynamics (MD) simulations, to determine the in situ atomic scale structure of catalyst surfaces and heterogeneous interfaces in coordination with quantum mechanical (QM) studies of reactivity. The multiparadigm ReaxFF/MC/MD framework will be used to resolve the integral-occupation supercell structures of occupationally disordered multimetal oxides responsible for propane and propene ammoxidation. Most prominent among these are MoVNbTeO catalysts for ammoxidation of propene to acrylonitrile. Combining high temperature reactive dynamics trajectories with quantum-mechanical studies of key intermediates and transition states, the metallic elements involved in rate- and selectivity determining CH activation and carbon-heteroatom bond-forming steps will be identified. Separately, the chemical mechanism by which vanadyl pyrophosphate ((VO)2P2O7) stores oxygen atoms at its surface for use in the 14-electron oxidation of butane to maleic anhydride will be determined by simulating the annealing and calcination of large unit cell models of the vanadyl pyrophosphate and other high oxidation state V/P/O phases. New heterogeneous multimetallic catalysts for hydrocarbon functionalization will be posited through the optimal combination of the CH activation, radical trapping, ammonia activation and oxygen activation functions of existing catalysts. This computational framework has been validated on simpler bimetallic oxides, and will continue to be optimized. Developmental work will focus on (1) streamlining the fitting of force-field parameters for new combinations of elements against QM training sets and (2) extending the MC application of ReaxFF to grand canonical implementations. Interfacial phenomena in catalysis and applications necessary for sustainable energy consumption occur at a regime too large for mature quantum mechanics-based simulations to play a predictive role: passivation and band tuning at semiconductor surfaces, grain boundaries in layered thermoelectric materials, semiconductor-metal and semiconductor organometallic solvent interfaces which facilitate charge transfer between photosensitive and catalytic components in photosynthetic or photovoltaic devices. The broader scientific impact of developing the ReaxFF/MC/MD approach to classical but reactive molecular dynamics simulations will be a tool for addressing a limiting factor in many heterogeneous catalysis and interfacial science applications: determining atomic-scale structures under operating conditions. Multimetal oxide catalysts are used to produce the commodity chemicals acrolein and acrylonitrile from propene, and even small improvements in catalytic performance (i.e., selectivity and activity) will have a substantial effect on energy consumption and yield. The economic impact of replacing propene with propane cannot be overstated. Since propene is generated from propane with an approximate cost of 10 ¢/lb, elimination of this step has the potential to save the US chemical industry several hundred million dollars per year. In addition, each quarter of Prof. Goddard's year long class is informed by progress in the group's current research. Applications which illustrate specific kinds of atomic interactions are discussed in the quarter of lectures in chemical physics; new and established computational techniques are taught in the quarter of lectures on methods; methods and software developed through the group's research are applied by students from experimental groups in the quarter of hands-on project work in students' respective fields.

获化学系化学催化计划颁发此奖项的威廉A.来自加州理工学院化学与化学工程系的戈达德和同事罗伯特·尼尔森将通过蒙特卡罗（MC）和分子动力学（MD）模拟开发和应用反应力场（ReaxFF），以确定催化剂表面和非均相界面的原位原子尺度结构，并与反应性的量子力学（QM）研究相协调。多范式的ReaxFF/MC/MD框架将被用来解决职业无序的多金属氧化物的丙烷和丙烯氨氧化的整体占领超晶胞结构。其中最突出的是用于丙烯氨氧化成丙烯腈的MoVNbTeO催化剂。结合高温反应动力学轨迹与关键中间体和过渡态的量子力学研究，参与速率和选择性确定CH活化和碳-杂原子键形成步骤的金属元素将被确定。另外，焦磷酸氧钒（（VO）2 P2 O 7）存储氧原子在其表面用于丁烷的14-电子氧化为马来酸酐的化学机制将通过模拟焦磷酸氧钒和其他高氧化态V/P/O相的大晶胞模型的退火和煅烧来确定。通过现有催化剂的CH活化、自由基捕集、氨活化和氧活化功能的优化组合，将提出用于烃官能化的新的多相多金属催化剂。这种计算框架已经在更简单的氧化物上得到了验证，并将继续优化。开发工作将集中在（1）简化针对QM训练集的新元素组合的力场参数的拟合，以及（2）将ReaxFF的MC应用扩展到大规范实现。可持续能源消耗所需的催化和应用中的界面现象发生在一个太大的区域，以至于成熟的基于量子力学的模拟无法发挥预测作用：半导体表面的钝化和能带调谐，层状热电材料中的晶界，半导体-在光合成或光生伏打中促进光敏和催化组分之间电荷转移的金属和半导体有机金属溶剂界面装置.开发ReaxFF/MC/MD方法对经典但反应性分子动力学模拟的更广泛的科学影响将成为解决许多多相催化和界面科学应用中的限制因素的工具：确定操作条件下的原子尺度结构。多金属氧化物催化剂用于由丙烯生产商品化学品丙烯醛和丙烯腈，甚至催化性能的微小改进（即，选择性和活性）将对能量消耗和产率产生显著影响。用丙烷取代丙烯的经济影响怎么强调都不过分。由于丙烯是由丙烷产生的，成本约为10美分/磅，因此消除这一步骤有可能每年为美国化学工业节省数亿美元。此外，戈达德教授为期一年的课程的每一个季度都是由该小组目前的研究进展所告知的。说明原子相互作用的具体类型的应用程序在化学物理讲座的四分之一中进行了讨论;新的和建立的计算技术在方法讲座的四分之一中教授;通过小组研究开发的方法和软件由实验组的学生在学生各自领域的动手项目工作的四分之一中应用。