Climate change, expedited by anthropogenic activities, has become a major environmental concern in this century. Governments and organizations worldwide are gradually making substantial efforts to mitigate this challenge. A concrete step in this direction is to develop novel technologies that capture and convert low-concentration carbon dioxide into useful products. Recently, scientists have proposed carbon dioxide methanation in a membrane reactor as a promising approach. Specifically, distribution-type membrane reactors are appealing owing to high catalyst activity through hotspot formation mitigation.
Although the effectiveness of membrane reactors has been confirmed, the efficiency of membrane properties and heat transfer characteristics of membrane materials remain unclear.
In a new study, a team of researchers led by Professor Mikihiro Nomura from Shibaura Institute of Technology, Japan, and including Yuka Shimizu from the same institute and Marcin Moździerz, Grzegorz Brus, and Elzbieta Fornalik-Wajs from AGH University of Krakow, Poland, has demonstrated the novelty of distribution-type membrane reactor for carbon dioxide utilization. Their findings were made available online on 17 September 2025 and have been published in Volume 462 of the journal Catalysis Today on 1 February 2026.
"Through a double degree program between Shibaura Institute of Technology and AGH University of Krakow, we evaluated heat transfer in membrane components, which enabled us to demonstrate the specific advantages of the membrane reactors addressed in our research," explains Prof. Nomura.
Following this, the team controlled the reaction rate inside the reactor by distributed reactant feeding through the membrane. They subsequently conducted accurate thermal conductivity evaluation of the porous alumina (Al2O3) membrane with minute physical and chemical structural features via laser flash analysis measurements. The thermal conductivity in the solid part of this sample was measured to be 36.4% lower than that of non-porous alumina.
The researchers then utilized a catalytic membrane with a silica separation layer—with a hydrogen gas permeance of 1.4 × 10⁻⁶ mol m−2 s−1 Pa−1 and a hydrogen-to-carbon dioxide selectivity of 35.9—in the distributor-type membrane reactor test. They obtained a high carbon dioxide conversion of 92.3% at 350 ℃.
Built on these results, the team carried out Ansys Fluent software-based simulations to examine the impact of membrane thermal conductivity and permselectivity. The team set carbon dioxide permeance of the membrane to 3.91 × 10−8 mol m−2 s−1 Pa−1 for all situations, finding that the carbon dioxide permselective membrane with a high selectivity of 35.9 produces about 1.4 times more methane than the hydrogen permselective membrane with a low selectivity of 0.10. Furthermore, higher thermal conductivity of the membrane suppresses the temperature rise in the reactor.
"Membrane reactors enable spatially distributed reactant feeding within the reactor, providing enhanced control over reaction rates and temperature profiles in both the axial (flow) and the radial (membrane surface) directions. This unique capability and membrane shape make them well-suited for application in small-scale facilities. Therefore, applying membrane reactors to small-scale carbon dioxide emission sources—which are commonly owned by many small- and medium-sized enterprises with limited funding—will accelerate the realization of a carbon-neutral society. In particular, we anticipate their use in small combustion devices such as boilers, an area that has received little attention in efforts to combat global warming," concludes Prof. Nomura.
These results can also guide other exothermic processes such as hydrocarbon partial oxidation in membrane reactor systems, boosting sustainable technologies.
