3D printers are proving to have many more applications than those they were originally created for. At the University of Alicante, they have been used to design and manufacture advanced catalysts for environmental applications to reduce greenhouse gas emissions, such as carbon dioxide (CO2), and energy applications, for instance, purifying the hydrogen needed in fuel cells. In fact these devices have been proposed as an environmentally friendly alternative to conventional vehicle engines.
These applications have been achieved thanks to a new methodology for designing and manufacturing advanced catalysts using 3D printing developed and patented by the team of researchers led by the UA’s professors of Inorganic Chemistry, Agustín Bueno López and Dolores Lozano Castelló. The patent is the result of the work of both of them together with a team composed of four doctoral students and a postdoctoral contract researcher. The scientists have shown that 3D printers offer a cheap, fast and versatile alternative for designing and manufacturing the interior of monoliths, the parts that make up the catalysts.
Cell-structured monoliths, such as ‘honeycombs’, are used to support catalysts in many heterogeneous catalyst reactions at the industrial level and also in engines. In these reactions, the gases that react with each other and the solids or dust, which act as catalysts, play a major role. These two agents participate inside the monolith producing the chemical reactions and thus, transforming toxic gases into non-toxic ones, or obtaining a desired final product.
Nowadays, these monoliths are obtained by extrusion, so that only monoliths with parallel channels can be obtained. The possibility that solids could be deposited in geometric structures of the monolith would improve the chemical reactions thanks to an improved use of dust. This is precisely what has been achieved using the UA’s patented methodology, which consists of designing and manufacturing catalysts with advanced channel designs, using 3D printing, as an alternative to the standard extrusion method.
The high cost of the powder used as a catalyst is the reason why it is important to take advantage of it. This material, which acts as active phases of the catalyst, is synthesised in the laboratory by the UA research group. It is very expensive and not very abundant, based on metals such as platinum, palladium, rhodium or cerium oxides, as explained by Agustín Bueno. The importance of having achieved interior channels in the monolith with geometric shapes and advanced designs lies here.
One of the key actions in these applications of heterogeneous catalysis is to optimise the contact between gases and solids, a problem that has already been solved by the research team. As Dolores Lozano assured, 3D printing allows for manufacturing monoliths with new compositions, such as ceramics, carbon, polymers, and new channel designs, not only parallel channels as are currently obtained by extrusion, but with advanced designs, which will make it possible to design and develop catalysts optimised for heterogeneous catalysis reactions, where the reagents are in the gas phase, thus improving the conventional catalysts used.
The use of this type of catalyst allows for a reduction in greenhouse effect emissions, as it has been used in the carbon dioxide (CO2) methanation reaction, a reaction where CO2 is turned into methane, which is of great interest for CO2 recovery. Today, the conversion and use of CO2 is an attractive and promising solution to reduce greenhouse gas emissions. Agustín Bueno explained how this research has managed to considerably increase the speed of CO2 methanisation, using advanced catalyst supports designed and manufactured with 3D printing.
Also, selective oxidation of carbon monoxide (CO) is a necessary reaction to purify the hydrogen used in fuel cells. This type of device is proposed as an eco-friendly alternative to conventional combustion engines. The new designs of catalysts manufactured by means of 3D printing in the research developed at the UA make it possible to optimise their composition, as well as the geometry of the monoliths, synthesising catalysts with excellent behaviour in CO selective oxidation, working more efficiently and at temperatures below 150o C», Dolores Lozano said.