Collaborative Research: Fundamentals of Natural Gas Conversion to Fuels and Chemicals over Molybdenum Nanostructures

天然气或甲烷是一种丰富的资源，不幸的是，由于缺乏有效的技术，使其转化为易于冷凝或适合运输的液体产品，因此未得到充分利用。偏远地区的大部分天然气储量和原油开采过程中产生的伴生气被归类为搁浅，典型的处置方式是放空和燃烧，造成了严重的环境问题和碳氢化合物资源的浪费。天然气转化为液体燃料和化学品是一个非常理想的目标，因为北美拥有世界上最大的天然气储量，可以作为安全稳定的碳氢化合物来源。目前，从甲烷中生产化学品和液体燃料的技术主要依靠合成气的产生作为第一步。然而，这些技术具有固有的低效率，因为在合成气生产中所有甲烷C-H键的断裂必须在随后的步骤中进行实质性的逆转。因此，目前正在加紧研究开发甲烷转化的直接方法。甲烷催化活化的研究仍然是一个具有很高科学和工业意义的领域，但目前对甲烷活化的催化化学知之甚少。这种情况将随着新泽西州史蒂文斯理工学院的西蒙·波德科尔津和宾夕法尼亚州利哈伊大学的以色列·瓦克斯的获奖而改变。该研究的目的是建立一个分子筛负载Mo纳米结构催化甲烷转化为液体燃料和化学品的分子水平模型。甲烷在Mo纳米结构上的转化为选择性甲烷活化提供了一种很有前途的替代方法。中国大连的一个研究小组最近报道了这种化学反应。在甲烷脱氢芳构化过程中，甲烷可直接一步转化为苯，选择性为70 ~ 80 mol %，转化率超过10 mol %。与其他甲烷直接活化化学反应相比，该过程有两个独特的优点，因为甲烷的转化不需要任何额外的反应物。首先，不可能像采用O2或H2O加成法那样，将甲烷完全氧化为碳氧化物。从安全的角度来看，这也是有利的。其次，天然气处理在概念上可以在偏远地区进行，因为不需要运输试剂。他们打算在纳米尺度上研究反应条件下活性表面位点的动力学。他们将结合最新发展的分子光谱表征技术（拉曼，红外和紫外-可见）在纳米尺度下的高温反应条件下的催化剂动力学测试，动力学建模和量子化学计算。先进的时间分辨原子XANES/EXAFS表征将与布鲁克海文国家实验室合作进行。该项目的成果将对纳米技术和能源研究产生变革性影响，通过开发纳米材料将天然气有效地转化为液态碳氢化合物，并有可能使大量滞留天然气可用，同时解决在偏远地区排放和燃烧伴生气的环境问题。广泛的教育推广项目是该计划的组成部分，包括研究经验以及能源研究和纳米材料的大学和K-12教学模块。

Natural gas, or methane, is an abundant resource that is unfortunately underutilized due to a lack of efficient technologies that enable its conversion into easily condensable or liquid products amenable to transport. Most natural gas reserves and the associated gas produced in the course of crude oil production at remote locations are classified as stranded, and venting and flaring is a typical method of disposal, resulting in a significant environmental issue as well as a waste of hydrocarbon resource. Natural gas conversion to liquid fuels and chemicals represents a highly desirable goal since North America has some of the largest gas reserves in the world that can serve as a safe and stable source of hydrocarbons. Production of chemicals and liquid fuels from methane is currently dominated by technologies that rely on generation of synthesis gas as the first step. These technologies, however, have an inherent inefficiency since the breaking of all methane C-H bonds in synthesis gas production has to be substantially reversed in subsequent steps. There are, therefore, intense current research efforts for development of direct methods for methane conversion. Research on catalytic methane activation remains an area of high scientific and industrial significance but the catalytic chemistry of methane activation is currently poorly understood. This situation will change with an award made to investigators Simon Podkolzin of the Stevens Institute of Technology, New Jersey, and Israel Wachs of Lehigh University, Pennsylvania. The objective of the proposed research is to develop a molecular level model of catalytic methane conversion to liquid fuels and chemicals by zeolite-supported Mo nanostructures. Methane conversion over Mo nanostructures supported on shape selective zeolites offers a promising alternative for selective methane activation. This chemistry was recently reported by a group from Dalian, China. In this process of methane dehydoaromatization, methane can be converted directly in a single step into benzene with a selectivity of 70-80 mol % and conversions exceeding 10 mol %. In contrast to other direct methane activation chemistries, this process has two unique advantages since methane is converted without any additional reactants. First, complete oxidation of methane to carbon oxides is not possible as in the processes employing O2 or H2O addition. This is also advantageous from the safety perspective. Second, natural gas processing can in concept be performed at remote locations since transportation of reagents is not required. The PIs intend to study the dynamics of active surface sites at the nanoscale under reaction conditions. They will combine the latest developments in molecular spectroscopic characterization techniques (Raman, IR and UV-vis) at the nanoscale under reaction conditions at elevated temperatures with catalyst kinetic testing, kinetic modeling, and quantum-chemical calculations. Advanced time-resolved atomic XANES/EXAFS characterization will be performed in collaboration with Brookhaven National Laboratory. Results of this program will have transformative effects in nanotechnology and energy research by developing nanomaterials for efficient conversion of natural gas into liquid hydrocarbons and potentially making available large reserves of stranded gas, while addressing the environmental issue of venting and burning of associated gas at remote locations. A broad spectrum of educational outreach projects is an integral part of the program, including research experiences as well as university and K-12 teaching modules on energy research and nanomaterials.