Storing carbon dioxide emissions from power plants underground to battle climate change is an attractive concept. But carbon storage carries risks. So many researchers have been trying to find ways to recycle the greenhouse gas by turning it into fuels such as methanol and hydrogen. The methods developed so far have been expensive and complicated, with several steps involved.

A team of chemists and engineers at the University of Texas at Arlington has now come up with a one-step process to convert carbon dioxide and water into a liquid hydrocarbon fuel. Their process involves a combination of high-intensity light, high pressure and temperature, and a cheap, abundant catalyst.

As an environment-friendly bonus, the process also produces oxygen as a by-product, the researchers say. The team’s goal is to eventually drive the process by using sunlight for both the heat and the light, making it sustainable and carbon-neutral. Their results are published in Proceedings of the National Academy of Sciences.

The researchers built a tube-shaped reactor filled with glass beads that are coated with a catalyst powder made from cobalt and titanium dioxide. They injected carbon dioxide and steam at one end of the tube. An electric heating rod passing through the tube heated the catalyst to 180–200°C, while four mercury lamps surrounding the tube shone intense light on it. The pressure was kept between 1 and 6 atmospheres. The researchers condensed the gas coming out the other end of the tube to get the liquid fuels, which included methanol and propanol.

The researchers admit that the efficiency of the process is not commercially viable; it’s just a lab demonstration at this point and is far form optimized, they point out.

The cobalt-titanium dioxide catalyst only absorbs part of the sun’s light spectrum. The team plans to make a catalyst that would absorb all of it, so that they can use sunlight instead of mercury lamps. They envision using mirrors to concentrate sunlight on the catalyst, providing both heat and light for the reaction. – Prachi Patel | 25 February 2016

Source: Wilaiwan Chanmanee, Mohammad Fakrul Islam, Brian H. Dennis, and Frederick M. MacDonnell (2016). Solar photothermochemical alkane reverse combustion. PNAS doi: 10.1073/pnas.1516945113