September 13, 2011Advances in understanding molybdenum nanostructures and molecular mechanisms of catalytic reactions to provide improved natural gas processing technologies.
Natural gas is an abundant resource that is tremendously underutilized due to a lack of efficient technologies that enable its conversion into shippable products. To address this problem, Dr. Simon G. Podkolzin of Stevens Institute of Technology and Dr. Israel E. Wachs of Lehigh University are studying the fundamentals of a new catalytic process for converting natural gas into benzene and other easily shippable liquid hydrocarbons over supported molybdenum nanoparticles. Their joint research has recently been awarded a research grant from the National Science Foundation (NSF).
"By enabling more practical and efficient consumer access to natural gas, this research has enormous potential to expand our use of this relatively clean energy source," says Dr. Michael Bruno, Dean of the Charles V. Schaefer, Jr. School of Engineering and Science.
Natural gas is more environmentally friendly than oil or coal-based fuels because it has the highest hydrogen to carbon ratio of all hydrocarbons. Although the United States has one of the biggest natural gas reserves in the world, gas utilization is severely restricted because 30-60% of its reserves are classified as "stranded." Stranded natural gas cannot be used locally due to a lack of on-site demand and cannot be efficiently transported to consumers due to a lack of infrastructure. This is because it is usually uneconomical to transport natural gas in the gas phase, and the costs of gas liquefaction or building a pipeline are usually prohibitively high.
The problem of natural gas under-utilization is exacerbated by the fact that when natural gas is produced in the course of crude oil production at remote locations, it is usually burned at the well or vented as a means of disposal due to a lack of efficient processing technologies. In recent years, approximately 150 billion cubic meters of natural gas have been wasted by flaring or venting worldwide annually, which is equivalent to about 25% of the total gas consumption in the US. Moreover, the environmental impact of wasteful natural gas venting is so severe that solving the problem of stranded natural gas conversion alone would more than meet the requirements of the Kyoto Protocol on the reduction of greenhouse gas emissions to combat global warming. Development of efficient natural gas conversion technologies is, therefore, urgent and essential not only for energy production and sustainability of feedstocks for the chemical industry but also for protecting the environment.
The objective of the NSF-funded research is to develop a molecular level understanding of natural gas conversion to liquid fuels and chemicals by zeolite-supported molybdenum nanostructures. The gained fundamental insights into the properties of molybdenum nanostructures and molecular mechanisms of catalytic reactions will be applied to the development of improved natural gas process technologies. Preliminary results obtained by Professors Wachs and Podkolzin for the first time identified the initial structure of molybdenum catalytic active sites and demonstrated that this initial structure can be fully recovered on catalyst regeneration with gas-phase oxygen. The project synergistically combines the premier expertise of Dr. Wachs in the field of operando molecular spectroscopy of catalytic processes, which involves simultaneous spectroscopic analysis of catalytic surface events and online analysis of reaction products that allows the development of fundamental structure-activity relationships, with the expertise of Dr. Podkolzin in reaction kinetics, kinetic modeling, and quantum-chemical calculations with vibrational analyses for the interpretation of experimental spectra. The research, thus, combines the latest advances in molecular spectroscopy under reaction conditions with quantum-chemical calculations that were not feasible even several years ago.
"The results of this research will be far-reaching for nanotechnology applications and our understanding of catalytic chemistry at the fundamental level," reports Dr. Henry Du, Department Director for Chemical Engineering and Materials Science at Stevens. 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, thus, making available large reserves of stranded gas and solving the environmental issue of venting and burning of natural gas at remote locations. This research program will also have a transformative effect on catalytic chemistry by developing methodologies for combining experimental molecular spectroscopy of supported nanostructures under reaction conditions with quantum-chemical calculations and reaction kinetics in order to describe dynamic changes in the catalyst structure and obtain molecular level insights into reaction pathways of light hydrocarbons over solid catalysts. The anticipated wealth of basic and applied knowledge resulting from this research program will advance the rational design of catalytic materials and, more broadly, technologies that involve a gas-solid interface (for example, sensors) as well as synthesis and characterization of nanomaterials.