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

天然气，或称甲烷，是一种丰富的资源，不幸的是，由于缺乏有效的技术将其转化为易于冷凝或易于运输的液体产品，这种资源没有得到充分利用。偏远地区的天然气储量和原油开采过程中产生的伴生气大多属于滞留状态，排放和燃烧是一种典型的处置方式，造成了严重的环境问题和油气资源的浪费。将天然气转换为液体燃料和化学品是一个非常可取的目标，因为北美拥有世界上一些最大的天然气储量，可以作为安全稳定的碳氢化合物来源。目前，从甲烷生产化学品和液体燃料的技术主要依赖于生产合成气作为第一步。然而，这些技术具有内在的低效，因为在合成气生产中，所有甲烷C-H键的断裂必须在后续步骤中基本上逆转。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。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伊斯雷尔·瓦克斯获奖，这种情况将会改变。本研究旨在建立分子筛负载钼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。择形沸石负载的Mo纳米结构上的甲烷转化为甲烷的选择性活化提供了一种很有前途的选择。来自大连的中国小组最近报道了这种化学作用。在甲烷脱去芳构化过程中，甲烷可一步直接转化为苯，选择性为70-80摩尔%，转化率超过10摩尔%。与其他甲烷直接活化化学方法相比，该过程有两个独特的优点，因为甲烷无需任何额外的反应物即可转化。首先，甲烷完全氧化成碳氧化物是不可能的，因为在使用O2或H2O加成的过程中。从安全的角度来看，这也是有利的。其次，天然气加工在概念上可以在偏远地区进行，因为不需要运输试剂。PI打算在反应条件下研究纳米尺度上的活性表面位置的动力学。他们将结合纳米级分子光谱表征技术(拉曼光谱、红外光谱和紫外可见光谱)在高温反应条件下的最新发展，与催化剂动力学测试、动力学建模和量子化学计算相结合。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。该计划的成果将对纳米技术和能源研究产生革命性的影响，开发将天然气有效转化为液态碳氢化合物的纳米材料，并有可能获得大量滞留天然气，同时解决偏远地区伴生天然气排放和燃烧的环境问题。广泛的教育推广项目是该计划的组成部分，包括研究经验以及关于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.