Fuel cells are systems poised to replace batteries in mobile phones, laptops, and vehicles. They convert the energy produced by combining oxygen and hydrogen into electricity. However, there are currently challenges in storing hydrogen safely, although a good option is to use an infrastructure that generates hydrogen gas within the fuel cell itself.
In these cases, methanol is typically used as a raw material. For example, instead of powering vehicles or phones with hydrogen, methanol can be added, converting it into hydrogen as needed. Now, researchers at the University of the Basque Country (UPV/EHU) have developed a device to improve this process.
They have designed a special infrastructure: a reactor made up of microchannels. The resulting microreactor is one hundred times smaller than a conventional reactor system. The reactor size is crucial for all these mobile devices. “Developing a reactor composed of microchannels is no easy task,” explained Oihane Sanz, a researcher in the Department of Applied Chemistry at the University of the Basque Country (UPV/EHU). “It is essential to carefully select the materials, machine the microchannels, assemble the system, and apply the catalytic coating, among other things.”.
As they have observed, these reactors composed of microchannels help improve heat transfer for converting methanol into hydrogen. Thanks to this, the reaction temperature is properly controlled, thus minimizing hot spots where carbon monoxide (CO) is produced. If CO is generated along with the hydrogen, it can contaminate the fuel cell and prevent it from functioning correctly, thus halting energy production.
A stable catalyst
Similarly, choosing a catalyst and using an appropriate placement method are essential for the reaction to proceed most efficiently. “One of the biggest challenges with these microchannel reactors is introducing the catalyst into such tiny channels. That's why the goal of this research was to design a stable catalyst and install it in the system in the best possible way,” explains Sanz.
In processes for producing hydrogen from methanol, palladium (Pd) catalysts are used, as in this case. Specifically, they used PdZnO. Often, "when integrating catalysts into reactors made up of microchannels, the catalysts' characteristics are lost. However, with the catalysts used in this study, in addition to maintaining their characteristics, we were able to carry out the process easily," he adds.
With the appropriate infrastructure and catalyst, the designed microreactor produces 30 liquid hydrogen/Hg; methanol conversion is 95%, and carbon monoxide (CO) conversion is less than 1%. “It is very important to control carbon monoxide production, as it can contaminate the fuel cell,” Sanz points out.
“Systems that produce a greater quantity of hydrogen (12-50 lH2/hg) have been documented, but the methanol conversion is lower (around 80%, and in some cases, as low as 4%), and, in addition, marginal products are generated,” adds Sanz, who highlights how this design “allows us to develop a cleaner, safer and less costly process.”.
The research was carried out by the Department of Applied Chemistry at the Faculty of Chemical Sciences of the University of the Basque Country (UPV/EHU), led by Professor Mario Montes. Also collaborating were the group led by Professor José Antonio Odriozola (ICMS, Joint Center US-CSIC) at the University of Seville, and the group led by Professors Gurutze Arzamendi and Luis M. Gandia at the Public University of Navarre.
Bibliographic reference
FJ Echave, O. Sanz, M. Montes. “Washcoating of micro-channel reactors with PdZnO catalyst for methanol steam reforming” Applied Catalysis A: General: 159 -167 2014.
Source: SINC Agency
