Thin‐Film Catalytic Coating of a Microreactor for Preferential CO Oxidation over Pt Catalysts

Abstract

Different Pt-based catalyst layers have been prepared and tested in a stacked foil microreactor for CO oxidation and preferential oxidation of CO in presence of hydrogen. The reactions were performed on Pt without support by impregnation of a pre-oxidized microstructured metal plate, Pt/Al 2 O 3 and Pt/CeO 2 based on sol methods as well as Pt/nano-Al 2 O 3 , a combined method of sol-gel and nanoparticle slurry coating. The ceria based sol-gel catalyst was much more active for CO oxidation than alumina based sol-gel catalysts at low temperature. However, total oxidation was only obtained at higher temperature on the alumina based catalysts. The combined method seems to have advantages in terms of less internal mass transfer limitation when trying to increase the catalyst coating thickness based on sol-gel approaches due to no reduction of CO selectivity up to 300°C reaction temperature. Experiments on CO oxidation with the Pt/CeO 2 catalyst have been conducted in an oxygen supply microreactor to evaluate the catalyst performance under sequential oxygen supply to reaction zone (CO excess).

Capillary microreactors based on hierarchical SiO2 monoliths incorporating noble metal nanoparticles for the Preferential Oxidation of CO

“…Regarding the deactivation of the catalysts in the longterm catalytic tests, it should be mentioned that only few works related to microreactors technology have addressed this issue [13], [31] and, in some cases, deactivation of the catalysts has also been found, even for Pt-based catalysts. This is not the case of the Pt/SiO 2 microreactor presented in this work that displays selectivity values at complete CO depletion of ~50%, very similar to that previously reported for other kind of microreactors in the literature [4], [12], [38]. It should me mentioned that in some cases where very good activity performances have been reported, selectivity results are not provided [27].…”

“…Usually, the microreactors designed for this application consist on thin layers of catalyst deposited on these structures [4], [12], [13]. However, the preparation of mechanically stable, homogeneous crack-free coatings of the catalyst along the microchannel is not straightforward.…”

Electrochemically dealloyed platinum with hierarchical pore structure as highly active catalytic coating

“…Moreover, the small channel dimensions efficiently quench gas phase radical chemistry, which allows reactor operation in the explosive regime of feed gas mixtures 4 (e.g. Supported catalysts were realized by adding an active metal to the sol either prior to deposition 16 or after deposition 15,17 and subsequent calcination/reduction. The excellent transfer capabilities, low catalyst inventory and increased safety allow operation under unconventional harsh reaction conditions, i.e.…”

“…Typically employed powders are micron sized IJPt/Al 2 O 3 , Rh/Al 2 O 3 , 11 Al 2 O 3 12 ) or ball-milled IJAl 2 O 3 , 13 1.5 wt% Pd/Na-Al-Si-Ox 14 ) commercial catalysts or catalyst supports. Smaller particle sizes of the deposited powders were obtained with self-made small sols of oxides IJAl 2 O 3 , 15,16 SiO 2 , 15 TiO 2 , 15 CeO 2 17 ). Supported catalysts were realized by adding an active metal to the sol either prior to deposition 16 or after deposition 15,17 and subsequent calcination/reduction.…”

“…Smaller particle sizes of the deposited powders were obtained with self-made small sols of oxides IJAl 2 O 3 , 15,16 SiO 2 , 15 TiO 2 , 15 CeO 2 17 ). Supported catalysts were realized by adding an active metal to the sol either prior to deposition 16 or after deposition 15,17 and subsequent calcination/reduction. When the sols are deposited in the presence of pore templates such as polymer micelles wall-coated catalyst layers with ordered porosity and high internal surface area can be obtained.…”