Oct 17 2017
Methane gas, an abundant natural resource, is frequently disposed of through burning, but new research by Researchers at MIT could make it easier to trap this gas for use as a chemical feedstock or fuel.
MIT chemistry professor Yogesh Surendranath and three colleagues have found a way to use electricity, which could potentially come from renewable sources, to convert methane into derivatives of methanol. The researchers developed a low-temperature electrochemical process that would continuously replenish a catalyst material that can rapidly carry out the conversion. (Courtesy of the researchers)
Numerous oil wells burn off methane — the largest constituent of natural gas — in a process known as flaring, which presently wastes 150 billion cubic meters of the gas annually and produces an astounding 400 million tons of carbon dioxide, making this process a huge contributor to global warming. Allowing the gas to escape unburned would result in even greater environmental damage, however, because methane is an even stronger greenhouse gas than carbon dioxide is.
Why is all this methane being wasted, when at the same time natural gas is publicized as a vital “bridge” fuel as the world moves away from fossil fuels, and is the cornerstone of the so-called shale-gas revolution? The answer, as the maxim goes in the real estate industry, is simple: location, location, location.
The wells where methane is flared away are chiefly being used for their petroleum; the methane is just a byproduct. In areas where it is convenient to do so, methane is captured and used to produce electrical power or make chemicals. However, special equipment is necessary to cool and pressurize methane gas, and special pipelines or pressurized containers are required to transport it. In many places, such as remote oil fields or offshore oil platforms far from the required infrastructure, that is just not economically feasible.
But currently, MIT Chemistry Professor Yogesh Surendranath and three colleagues have discovered a way to use electricity, which could potentially be achieved using renewable sources, to convert methane into byproducts of methanol, a liquid that can be transformed into automotive fuel or used as a precursor to a range of chemical products. This new technique may allow for cheaper methane conversion at remote sites. The findings, illustrated in the journal ACS Central Science, could open doors to making use of a substantial methane supply that is otherwise completely wasted.
This finding opens the doors for a new paradigm of methane conversion chemistry.
Jillian Dempsey, Assistant Professor of Chemistry, The University of North Carolina
Current industrial processes for converting methane to liquid intermediate chemical forms require extremely high operating temperatures and large, capital-intensive equipment. Instead, the team has created a low-temperature electrochemical process that would uninterruptedly replenish a catalyst material that can swiftly perform the conversion. This technology could potentially result in, “a relatively low-cost, on-site addition to existing wellhead operations,” says Surendranath, who is the Paul M. Cook Career Development Assistant Professor in MIT’s Department of Chemistry.
The electricity to run such systems could be acquired from solar panels or wind turbines close to the site, he says. This electrochemical process, he says, could offer a way to achieve the methane conversion — a process also referred to as functionalizing — “remotely, where a lot of the ‘stranded’ methane reserves are.”
Already, he says, “methane is playing a key role as a transition fuel.” But the quantity of this beneficial fuel that is at present just flared away, he says, “is pretty staggering.” That massive quantity of wasted natural gas has even been picked up in satellite images of the Earth at night, in areas such as the Bakken oil fields in North Dakota that light up as luminously as big metropolitan areas due to flaring. Based on World Bank predictions, worldwide flaring of methane wastes a quantity equivalent to approximately one-fifth of U.S. natural gas consumption.
When that gas gets flared off instead of directly discharged, Surendranath says, “you’re reducing the environmental harm, but you’re also wasting the energy.” Finding a way to perform methane conversion at satisfactorily low cost to make it feasible for remote sites, “has been a grand challenge in chemistry for decades,” he says. The reason why methane conversion is so tough is that the carbon-hydrogen bonds in the methane molecule resist being broken, and at the same time there is a risk of overdoing the reaction and causing a runaway process that terminates the desired end-product.
Catalysts that could do the job have been explored for a number of years, but they usually require strong chemical agents that restrict the speed of the reaction, he says. The main new advance was incorporating an electrical driving force that could be tweaked precisely to produce more potent catalysts with extremely high reaction rates.
Since we’re using electricity to drive the process, this opens up new opportunities for making the process more rapid, selective, and portable than existing methods. We can access catalysts that no one has observed before, because we’re generating them in a new way.
Yogesh Surendranath, Chemistry Professor, MIT
The result of the reaction is a pair of liquid chemicals, methyl bisulfate and methanesulfonic acid, which can be additionally processed to make liquid methanol, a beneficial chemical intermediate to fuels, pharmaceuticals and plastics. The extra processing steps required to make methanol remain highly challenging and must be improved before this technology can be used on an industrial scale. The Researchers are vigorously refining their technique to handle these technological obstacles.
This work really stands out because it not only reports a new system for selective catalytic functionalization of methane to methanol precursors, but it includes detailed insight into how the system is able to carry out this selective chemistry. The mechanistic information will be instrumental in translating this exciting discovery into an industrial technology.
Jillian Dempsey, Assistant Professor of Chemistry, The University of North Carolina
The research team included postdoc Matthew O’Reilly and doctoral students Rebecca Soyoung Kim and Seokjoon Oh, all in MIT’s Department of Chemistry. The research was supported by the Italian energy company Eni S.p.A. through the MIT Energy Initiative.