Microreactors technology for hydrogen purification: Effect of the catalytic layer thickness on CuO /CeO2-coated microchannel reactors for the PROX reaction

Abstract

Two blocks of microreactors composed by 100 microchannels and coated, respectively, with 150 and 300 mg of a CuO x /CeO 2 catalyst, were prepared and tested in the preferential oxidation of CO in presence of H 2 (PROX). The deposition of different amount of catalyst resulted in different catalytic layer thicknesses thus modifying the catalytic performances of the microreactor. The evaluation of the main reaction variables (the space velocity, the O 2 -to-CO ratio and the presence of H 2 O and/or CO 2 in the stream) was performed over both microreactors and compared to that of the parent powder catalyst. The least loaded microreactor, with a coating thickness around 10 µm, presented the highest CO conversion and selectivity levels at temperatures below 160 ºC.This result evidences i) the improvement of the catalytic performances got by the structuration of the powder catalyst and ii) the importance of the selection of the adequate thickness of the catalytic layer on the microreactor, which have not to exceed and optimal value. An adequate coating thickness allows minimizing the mass and heat transport limitations, thus resulting in the enhancement of the catalytic performance during the PROX reaction.

Structuring Pt/CeO2/Al2O3 WGS catalyst: Introduction of buffer layer

“…For instance, Laguna et al [17] recently demonstrated the absence of significant diffusional limitations controlling the catalytic performances for layer thicknesses around 10 m. Moreover, Potemkin et al [36] established a limit slightly higher for the layer thickness, above 20 m, for which the diffusional processes does not control the reaction rate .…”

“…Considering that those processes are controlled by the layer thickness, the use of micromonolithic structures should improve the diffusional processes and allow a better control of the reaction through an appropriate catalytic layer thickness providing a better temperature control hindering the hot spot formation [16,17]. Therefore, the layer thickness should be well-controlled in order to maintain the enhancement of the transport phenomena provided by the micromonoliths.…”

Monoliths: A Review of the Basics, Preparation Methods and Their Relevance to Oxidation

“…In addition, coating monoliths by solution-combustion synthesis has given materials with good catalytic performance for the PrOx reaction in the presence of H 2 O and CO 2 [295,296]. Other properties that should be optimized to enhance the performance of copper/ceria monolithic catalysts include the coating thickness [297] and cell density of the structure [293].…”

An overview of the methanol reforming process: Comparison of fuels, catalysts, reformers, and systems

“…The catalyst coating methods for the wash‐coated microchannel reformers are out of the scope of this review paper; however, interested readers can refer to other studies …”