Thin-sheet microfibrous-structured Al-fiber@ns-AlOOH@Pd catalysts with low Pd-loading engineered from micro-to macro-scale are developed for the gas-phase CO coupling to dimethyl oxalate, providing unique combination of high activity/selectivity and good stability with high permeability and high thermal conductivity. The support of Al-fiber@ns-AlOOH is initially prepared via endogenous growth of boehmite nanosheets (ns-AlOOH) on 3D network of 60-m Al-fiber. The palladium is then placed onto the surface of the ns-AlOOH rooted on the Al-fiber via incipient wetness impregnation method with a toluene solution of palladium acetate. As an example, the catalyst with a low Pd-loading of 0.25 wt% delivers ~66% CO conversion and ~94% DMO selectivity for a feed of CH 3 ONO/CO/N 2 (10/14/76, vol%) with a gas hourly space velocity of 3000 L kg-1 h-1 , and particularly, is stable for at least 200 h without deactivation. Our Al-fiber@ns-AlOOH@Pd catalyst demonstrates two times higher intrinsic activity (expressed by turnover frequency) compared to a traditional Pd/-Al 2 O 3. The existence of Pd-hydroxyl synergistic interaction is paramount to the enhanced catalytic performance for the CO coupling reaction, by nature, as the result of hydroxyl-promoted adsorption of bridged CO on the Pd surface.
Endogenous growth of 2D boehmite nanosheets on 3D Al-fiber network via steam-only oxidation has been demonstrated, showing substantial potentials for structured catalysts verified by several hot-topic reactions.
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