As easy as playing Lego: Clean way to convert carbon dioxide waste into useful industrial products

Open flame
In an article published in the journal Advanced Energy Materials, Dr. Rahman Daiyan and Dr. Emma Lovell of the UNSW School of Chemical Engineering describe a method for producing nanoparticles that promote the conversion of carbon dioxide waste into useful industrial components. The researchers, who carried out their work in the Particle and Catalysis Research Laboratory, led by Scientia Professor Rose Amal, demonstrate that by producing zinc oxide at very high temperatures using a technique called Flame Spray Pyrolysis (FSP), they can create nanoparticles that act as a catalyst for the conversion of carbon dioxide into "synthesis gas" - a mixture of hydrogen and carbon monoxide used in the manufacture of industrial products. The researchers say that this method is cheaper and more scalable for the needs of heavy industry than what is available today.

"We used an open flame that burns at 2000 degrees to create nanoparticles of zinc oxide that can then be used to convert CO2 into synthesis gas using electricity," says Dr. Lovell.

"Syngas is often considered the chemical equivalent of Lego because the two building blocks - hydrogen and carbon monoxide - can be used in different ratios to produce things like synthetic diesel, methanol, alcohol or plastics, which are very important industrial precursors.

"So what we are essentially doing is converting CO2 into these precursors that can be used to make all these vital industrial chemicals.

Closing the loop
In an industrial environment, an electrolyzer containing the zinc oxide particles produced by FSP could be used to convert the waste CO2 into useful permutations of synthesis gas, says Dr. Daiyan.

"Waste CO2, for example from a power plant or cement factory, can be passed through this electrolyser, and inside we have our flame-sprayed zinc oxide material in the form of an electrode. When we introduce the waste CO2, it is processed using electricity and released from an outlet as synthesis gas in a mixture of CO and hydrogen," he says.

The researchers say they are in fact closing the carbon cycle in industrial processes that produce harmful greenhouse gases. And by making small adjustments to the way the nanoparticles are burned by the FSP technique, they can determine the possible mixture of synthesis gas building blocks that are produced when carbon dioxide is converted.

"At the moment, you are producing synthesis gas by using natural gas - that is, from fossil fuels," says Dr. Daiyan. "But we use waste carbon dioxide and then convert it into synthesis gas in a ratio that depends on what industry you want to use it in.

For example, a one-to-one ratio of carbon monoxide to hydrogen is suitable for synthesis gas that can be used as a fuel. But a ratio of four parts carbon monoxide and one part hydrogen is suitable for the production of plastics, says Dr. Daiyan.

Inexpensive and accessible
By choosing zinc oxide as a catalyst, the researchers have ensured that their solution remains a cheaper alternative to what has been attempted in this area up to now.

"Previous experiments have used expensive materials such as palladium, but this is the first case where a very cheap and abundant material mined locally in Australia has been successfully applied to the problem of converting carbon dioxide from waste," says Dr. Daiyan.

Dr. Lovell adds that what also makes this method attractive is the use of the FSP flame system to generate and control these valuable materials.

"It means that it can be used industrially, that it is scalable, that it is super fast in producing the materials and that it is very effective," she says.

"We don't have to worry about complicated synthesis processes that use really expensive metals and precursors - we can burn it and have these particles ready to use in 10 minutes. And by controlling how we burn it, we can control these ratios of the desired synthesis gas building blocks.

Upscaling
While the duo has already built an electrolyzer that has been tested with contaminated CO2 exhaust, scaling the technology to the point where it could convert all the carbon dioxide emitted by a power plant is still a long way off.

"The idea is that we can take a point source of CO2, such as a coal-fired power plant, a gas-fired power plant or even a natural gas-fired power plant.

Original publication: Advanced Energy Materials - Uncovering Atomic-Scale Stability and Reactivity in Engineered Zinc Oxide Electrocatalysts for Controllable Syngas Production

Source: Chemie.de - So einfach wie Legospielen: Sauberer Weg zur Umwandlung von Kohlendioxidabfällen in nützliche Industrieprodukte
Image Source: Wikimedia Commons - Arnold Paul