The authors of a new research argue that the first thermodynamically reversible chemical reactor that can produce hydrogen as a pure product stream demonstrates a “transformational” move in the chemical industry.
The new reactor, reported in the prestigious academic journal Nature Chemistry on May 28th, 2019, prevents mixing of reactant gases by transferring oxygen between reactant streams through a solid-state oxygen reservoir.
This reservoir is developed in such a way that it maintains near equilibrium with the reacting gas streams as they trace their reaction trajectory and therefore retains a “chemical memory” of the conditions to which it has been subjected to.
The outcome is that hydrogen is formed as a pure product stream, eliminating the need for expensive separation of the final products.
The study headed by Newcastle University, United Kingdom, included experts from the universities of Durham and Edinburgh and the European Synchrotron Radiation Facility in France and was funded by the Engineering and Physical Sciences Research Council (EPSRC).
Chemical changes are usually performed via mixed reactions whereby multiple reactants are mixed together and heated. But this leads to losses, incomplete conversion of reactants and a final mixture of products that need to be separated. With our Hydrogen Memory Reactor we can produce pure, separated products. You could call it the perfect reactor.
Professor Ian Metcalfe, Lead Author and Professor, Chemical Engineering, Newcastle University
Most Abundant Element in the Universe
The most abundant element in the universe is hydrogen. It is synthesized by the splitting of water molecules, and the shift toward renewable energy has resulted in an increase in what is called “green hydrogen.”
Hydrogen is a clean and valuable energy store and can be used as a fuel, to produce electricity, and can be stored and carried through the gas networks.
All processes—regardless of whether they are mechanical, electrical, or chemical—are thermodynamically irreversible and are less efficient than they otherwise could be.
This implies that when hydrogen is generated in conventional chemical reactors, it must be isolated from other products, a process that is expensive as well as often energy intensive.
The researchers described their new system and demonstrate a chemical reactor that, for the first time, can approach thermodynamically reversible operation.
In the system, water reacts with carbon monoxide to produce hydrogen and carbon dioxide, and also stops carbon from passing into the hydrogen and producing stream in the form of carbon dioxide or carbon monoxide, thereby preventing contamination of the product.
By “Flipping” the reservoir somewhat like a switch, the researchers demonstrated that high conversion can be achieved in the system so that hydrogen and carbon dioxide are formed at either end of the reactor as pure products.
“Whereas conventional hydrogen production requires two reactors and a separation, our reactor accomplishes all the steps in one unit,” adds Professor Metcalfe.
“And while we demonstrate the concept with hydrogen, the memory reactor concept may also be applied to other processes.”