Rational construction of secondary metal on to Ni-modified Al2O3 nanoflower to achieve synergetic catalytic epoxidation of styrene.

Styrene epoxidation to afford its epoxides shows a promising approach for value-added chemicals construction. By virtue of Ni-modified AlOOH nanoflowers as starting materials, secondary adsorption and thermal treatment transform the composite into Co/Cu coupled with NiO-modified Al2O3 nanoflowers. The results indicate that the Ni-modification improves the structural properties of AlOOH and regulates the morphology, while calcination treatment contributes to the surface area enlargement and hierarchical pore structure formation, which benefits the diffusion and accessibility of reactant molecules approaching reactive sites. The secondary introduced metal, including Cu/Co, affords a well-dispersed state close to the in situ formed NiO over the Al2O3 nanoflowers. It was found that the Co-modified catalyst Al2O3(Ni)-Cu exhibited the highest styrene conversion rate and styrene oxide selectivity compared to the Co-modified Al2O3(Ni)-Co and Al2O3(Ni). In addition, Al2O3(Ni)-Cu further showcases the great potential in the selective benzene oxidation to benzoquinone, in which benzene conversion reaches 60% at 10 h, and the benzoquinone selectivity was more than 90%, with near 1448 μmol yield. This finding indicates that copper and nickel species exert synergistic effects by electronic interactions between bimetals to influence the generation of final products, which provides valuable references for further research in related fields. This article is part of the theme issue 'Surfaces, interfaces and heterogeneous catalysis'.