If new catalysts work as well in a large, commercial scale plant as they do in tests, Siluria says, the company could produce gasoline from natural gas at about half the cost of making it from crude oil—at least at today’s cheap natural-gas prices. If Siluria really can make cheap gasoline from natural gas it will have achieved something that has eluded the world’s top chemists and oil and gas companies for decades. Indeed, finding an inexpensive and direct way to upgrade natural gas into more valuable and useful chemicals and fuels could finally mean a cheap replacement for petroleum.
Natural gas burns much more cleanly than oil—power plants that burn oil emit 50 percent more carbon dioxide than natural gas ones. It also is between two and six times more abundant than oil, and its price has fallen dramatically now that technologies like fracking and horizontal drilling have led to a surge of production from unconventional sources like the Marcellus Shale. While oil costs around $100 a barrel, natural gas sells in the U.S. for the equivalent of $20 a barrel.
ut until now oil has maintained a crucial advantage: natural gas is much more difficult to convert into chemicals such as those used to make plastics. And it is relatively expensive to convert natural gas into liquid fuels such as gasoline. It cost Shell $19 billion to build a massive gas-to-liquids plant in Qatar, where natural gas is almost free. The South African energy and chemicals company Sasol is considering a gas-to-liquids plant in Louisiana that it says will cost between $11 billion and $14 billion. Altogether, such plants produce only about 400,000 barrels of liquid fuels and chemicals a day, which is less than half of 1 percent of the 90 million barrels of oil produced daily around the world.
The costs are so high largely because the process is complex and consumes a lot of energy. First high temperatures are required to break methane down into carbon monoxide and hydrogen, creating what is called syngas. The syngas is then subjected to catalytic reactions that turn it into a mixture of hydrocarbons that is costly to refine and separate into products.
Rapidly screening tens of thousands of catalysts
Siluria thinks it can succeed where others have failed not because it understands the chemistry better, but because it has developed new tools for making and screening potential catalysts. Traditionally, chemists have developed catalysts by analyzing how they work and calculating what combination of elements might improve them. Siluria’s basic philosophy is to try out a huge number of catalysts in the hope of getting lucky. The company built an automated system—it looks like a mess of steel and plastic tubes, mass spectrometers, small stainless steel furnaces, and data cables—that can quickly synthesize hundreds of different catalysts at a time and then test how well they convert methane into ethylene.
The system works by varying both what catalysts are made of—the combinations and ratios of various elements—and their microscopic structure. Siluria was founded based on the work of Angela Belcher, a professor of biological engineering at MIT who developed viruses that can assemble atoms of inorganic materials into precise shapes. Siluria uses this and other methods to form nanowires from the materials that make up its catalysts. Sometimes the shape of a nanowire changes the way the catalyst interacts with gases such as methane—and this can transform a useless combination of elements into an effective one. “How you build up the structure of the catalyst matters as much as its composition,” says Erik Scher, Siluria’s vice president of research and development.
The process of making and testing catalysts isn’t completely random—Siluria has the work of earlier chemists to guide it, and it has developed software that sorts out the most efficient way to screen a wide variety of possibilities. The result is that what used to take chemists a year Siluria can now do in a couple of days, Scher says. “We’ve made and screened over 50,000 catalysts at last count,” he says. “And I haven’t been counting in a while.”