Conversion of Natural Gas to Aromatic Hydrocarbons
From Article by Kevin Bullis, MIT Technology Review, 3-1-13
High-performance ceramic membranes from the R&D company Ceramatec could lead to a cheaper way to convert natural gas into benzene, a liquid that can be used to make a wide variety of chemicals and serve as a component of gasoline.
If the approach works, it would open up large new markets for natural gas. It could also reduce the practice of flaring natural gas, which wastes about 140 billion cubic meters of gas each year worldwide, or the equivalent of about 20 percent of the annual demand in the United States. Oil wells in remote areas often use flaring because transporting the natural gas to market would be too expensive. The technology could work efficiently at relatively small scales, and be deployed at wells to produce liquids that are cheaper to transport than gas.
Existing gas-to-liquids conversion technology can require huge $15 billion to $20 billion plants (see “Turning Gas Flares into Fuel”). Such plants require expensive equipment that’s used to produce pure oxygen, which is reacted with methane, the chief component of natural gas.
The Ceramatec membrane could enable an alternative process pursued by Enrique Iglesia, a professor of chemical engineering at the University of California at Berkeley. Iglesia’s approach involves heating up methane to about 800 °C in the presence of catalysts to make liquid hydrocarbons. His process doesn’t use oxygen, and could also be far more selective, producing more of a desired product, which can also improve the economics.
Iglesia has previously developed catalysts for converting methane into liquid hydrocarbons without oxygen, but such processes have been impractical because the chemical reactions involved produce hydrogen, which build up in the reactor and inhibit chemical reactions. He tried to remove the hydrogen with membranes that conducted hydrogen out of the reactor while keeping the methane inside, but they couldn’t remove the hydrogen fast enough.
The current work, a collaboration with Ceramatec, is being supported by a $1.3 million grant from the U.S. Advanced Research Projects Agency for Energy. At an ARPA-E workshop just over a year ago, members of Iglesia’s research group met representatives from Ceramatec, which had developed a ceramic membrane that allowed hydrogen to flow orders of magnitude faster than other membranes. That meeting formed the basis of the current project, which will pair zeolite-based catalysts from Berkeley with Ceramatec membranes.
The technology is one of several funded by ARPA-E that are aimed at capitalizing on abundant natural gas supplies in the United States. In November, ARPA-E announced funding for the Gas Technology Institute, which is developing a process that converts methane to methanol. It also funded Pratt & Whitney to develop an approach that would use natural gas to produce low-cost gasoline that is says will be competitive with oil prices of $50 a barrel or higher.
NOTE: There are at least four stages in the development of a new commercial chemical process: (a) research in the laboratory, (b) development at bench-scale and pilot plant, (c) full scale size involving shake-down or de-bottle-necking, and (d) optimized design and construction of economically feasible chemical process. A new idea for a chemical process can and frequently does fail at one of these four states. The production of benzene from natural gas via ceramic catalyst appears to have successfully past the first of these stages. How well it can be scaled up to a commercial size remains to be determined. D.G.N.