How do crystal shapes of nano-ceria determine its ketonization performance during biomass pyrolysis?

Catalytic pyrolysis of biomass over CeO 2 to prepare ketonic chemicals is an important way to achieve carbon emission reduction, whereas the role of catalyst structure has long been overlooked. In this work, nano-CeO 2 with different crystal shapes, namely nanorods (R-CeO 2 ), nano-polyhedra (P-CeO 2 ), and nanocubes (C-CeO 2 ), were synthesized and then tested in catalytic ketonization of xylan . Results showed that among all the three catalysts, C-CeO 2 produced the highest yield of ketones . Characterization results revealed that C-CeO 2 presented the lowest content of oxygen vacancies while exhibiting the highest proportion of {100} facets, proving that the {100} facets made a greater contribution to the total yield of ketones . On the other hand, P-CeO 2 and R-CeO 2 displayed a better selectivity to linear ketones, which was beneficial to improving the product quality. The relative contents of {111} facets of these catalysts were higher than C-CeO 2 , demonstrating that the {111} facets could selectively produce linear ketones. The proposed mechanism indicated that P-CeO 2 and R-CeO 2 principally enhanced the ketonic deoxygenation reactions, while C-CeO 2 also promoted the recyclization reaction, producing more cyclic ketones . These findings disclose that the {111} facets of CeO 2 are more favorable to producing valuable linear ketones.