Thin-sheet sinter-locked Ti-microfiber-supported binary-oxide-nanocomposite catalysts engineered on the micro- to macroscales were developed for the gas-phase aerobic oxidation of benzyl alcohol to benzaldehyde. The catalysts demonstrated higher activity than single-oxide and noble-metal catalysts with good stability and regenerability. The catalysts were obtained by placing transient metal (e.g., Ni, Co, Cu, Mn) nitrates onto a Ti-microfiber surface by impregnation, and the supported nitrates were subsequently in situ transformed into the binary-oxide composites in the real reaction stream at 300 °C. Among them, CoO-2.5–CuO_x-2.5/Ti-fiber was found to be the best catalyst; it delivered 93.5 % conversion of benzyl alcohol (b.p. 210 °C) with 99.2 % selectivity to benzaldehyde at 230 °C. In situ induced formation of “CoO@Cu₂O” ensembles (i.e., larger CoO nanoparticles partially covered with smaller Cu₂O clusters and/or nanoparticles) was identified, which by nature resulted in a large Cu₂O–CoO interface and led to a significant improvement in the low-temperature activity.

Concerns about the clean utilization of coal and the development of sustainable energy have provided a particular impetus for the exploration into the production of substitute natural gas (SNG) by syngas methanation in some parts of world. Owing to heat-transfer limitations, current SNG technology based on a series of fixed-bed reactors packed with oxide-supported Ni catalysts suffers from issues such as high costs, low efficiency, and catalyst sintering. We report a monolithic Ni-Ce-Al₂O₃/Ni-foam catalyst obtainable by modified wet-chemical etching of Ni foam. Such a catalyst, with significantly enhanced heat transfer, is highly active, highly selective, and very stable for syngas methanation. Computational fluid dynamics calculations and experimental measurements consistently show a large reduction in the “hotspot” temperature in the Ni-foam-structured catalyst bed owing to high thermal conductivity. We anticipate that our approach will open a new opportunity for next-generation SNG plant design.

The highly active and selective gold-on-copper fiber catalysts with excellent heat conductivity were successfully prepared for high-efficiency gas-phase selective oxidation of various alcohols. The Au/Cu-fiber catalysts were obtained by conducting galvanic deposition of Au onto a thin-sheet microfibrous structure that consisted of 5 vol % Cu-fiber (8 μm diameter), and 95 vol % voidage. The best catalyst was Au-3/Cu-fiber-200 (Au loading: 3 wt %; calcined at 200 °C in air), which was effective for acyclic, benzylic, and polynary alcohols using a high weight hourly space velocity of 20 h⁻¹. Benzyl alcohol conversion of 86 % was obtained with 99 % selectivity to benzaldehyde at 220 °C. Cyclopropanemethanol could be transformed to cyclopropanecarboxaldehyde, with conversion of 91 % and selectivity of 95 % at 250 °C. 1,2-Propanediol demonstrated a high conversion of 92 %, with a medium selectivity of 74 % at 340 °C. An oxidation of volatile unsaturated alcohols, such as crotyl alcohol and 3-methyl-2-butenol, could also proceed highly selectively with good conversions at 280 °C. A low ΔT of less than 10 °C between the catalyst bed and the external wall of the reactor was observed in the selective oxidation of benzyl alcohol owing to the enhanced heat-transfer ability that permits rapid dissipation of large quantities of the reaction heat. Special AuCu(alloy)–Cu₂O active composites were formed during the reaction, and their cooperative effect contributed to increasing the low-temperature activity. By nature, the AuCu alloy can catalyze the oxidation of Cu₂O–H species with O₂ to release active Cu₂O sites.