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[Display omitted] • Unique pompon-like RuCo catalysts were fabricated. • Atomically dispersed Ru-Co sites facilitated the adsorption/activation of reactants. • Excellent catalytic performance was achieved in the guaiacol hydrodeoxygenation. • Ru-Co synergy, as well as favorable hcp structure, contributed to high catalytic efficiency. Currently, the highly efficient conversion of biomass resources into highly valuable chemicals and biofuels is one of the most prospective approaches to reduce greenhouse gases emission and environmental pollution caused by excess consumption of fossil fuels. Herein, three-dimensional pompon-like well-defined RuCo particles with tunable crystallographic structures and surface atomically dispersed Ru atoms were constructed and intensively investigated as support-free metal catalysts in the hydrodeoxygenation (HDO) of lignin-derived guaiacol. It was demonstrated that the 300 °C-reduced RuCo sample possessed the hexagonal close-packed (hcp) crystallographic structure with surface abundant atomically dispersed Ru atoms, whereas 600 °C-reduced RuCo sample presented the face-centered cubic phase with lower surface Ru concentration. The as-fabricated RuCo-300 sample showed excellent catalytic HDO activity with a high cyclohexane yield of 85.3%. Comprehensive structural characterizations unveiled that the introduction of atomically dispersed Ru atoms into the RuCo-300 favored the formation of abundant surface Ru-Co sites, as well as electron-rich Ru0, and such-constructed Ru-Co sites were highly beneficial to the hydrogen dissociation on single Ru0 atoms and the further hydrogen spillover to adjacent Co0 atoms to promote the HDO process. Moreover, density functional theory (DFT) calculations revealed that the hcp structure of RuCo catalysts benefited the adsorption of guaiacol. The unique pompon-like microstructure of RuCo catalysts was conducive to the exposure of active sites and provided more open channels for the easy diffusion of reactants and products. Over the RuCo-300 catalyst, the guaiacol HDO could proceed rapidly via an initial demethoxylation reaction. The present Ru-Co synergetic catalysis in the structure of RuCo catalysts would provide a new strategy for constructing robust heterogeneous bimetal catalysts applied in practical HDO processes of a variety of lignin-derived phenolic compounds. [ABSTRACT FROM AUTHOR]

Abstract: The present work reported the synthesis of Co–Al mixed metal oxides/carbon nanotubes (CoAl-MMO/CNT) nanocomposite from Co–Al layered double hydroxide/CNTs composite precursor (CoAl-LDH/CNT). The materials were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), low temperature nitrogen adsorption–desorption experiments, thermogravimetric and differential thermal analyses (TG–DTA), Raman spectra and X-ray photoelectron spectroscopy (XPS). The results revealed that in CoAl-MMO/CNT nanocomposite, the nanoparticles of cobalt oxide (CoO) and Co-containing spinel-type complex metal oxides could be well-dispersed on the surface of CNTs, thus forming the heterostructure of CoAl-MMO and CNTs. Furthermore, as-synthesized CoAl-MMO/CNT nanocomposite was utilized as additives for catalytic thermal decomposition of ammonium perchlorate (AP). Compared to those for pure AP and CoAl-MMO, the peak temperature of AP decomposition for CoAl-MMO/CNT was significantly decreased, which is attributed to the novel heterostructure and synergistic effect of multi-component metal oxides of nanocomposite. [Copyright &y& Elsevier]

[Display omitted] • K-containing spinel-type ZnCo x Fe 2-x O 4 nanoparticles were fabricated. • Ternary ZnCo x Fe 2-x O 4 nanoparticles facilitated in situ the generation of iron-cobalt carbide. • An unprecedentedly high iron time yield to light olefins was obtained. • Fe-Co interactions boosted CO 2 hydrogenation to produce light olefins. Currently, the CO 2 conversion to light olefins is attractive in clean energy research. Despite numerous works on Co-Fe bimetallic catalysts, the lack of well-defined bulk structures with identical crystalline phase and similar textural property hinders the in-depth understanding of the roles of Fe and Co species. Herein, series of uniform K-containing spinel-type ZnCo x Fe 2-x O 4 nanoparticles (x = 0, 0.5, 1.0, 1.5, 2.0) were successfully synthesized via a single source layered double hydroxide precursor route. Compared to ZnFe 2 O 4 and ZnCo 2 O 4 , as-fabricated ternary ZnCo 0.5 Fe 1.5 O 4 spinel nanoparticles as the catalyst exhibited an outstanding performance toward CO 2 hydrogenation to produce light olefins, with a 36.1% selectivity toward C 2 =-C 4 = products at a 49.6% conversion and an unprecedentedly high iron time yield for CO 2 conversion to light olefins (∼29.1 μmol CO2 ·g Fe −1·s−1) at the gaseous hourly space velocity of 24000 mL·g cat −1·h−1. In combination with structural characterizations and reaction results, it was unveiled that during the CO 2 hydrogenation over ternary ZnCo x Fe 2-x O 4 catalysts, the formation of electron-rich Fe0 atoms in the CoFe alloy phase significantly promoted in situ the generation of active iron-cobalt carbide, Co 2 C, and θ -Fe 3 C phases, thereby improving the reactivity of catalysts for the production of hydrocarbons and simultaneously inhibiting both the CO 2 methanation and the secondary hydrogenation of olefins. The present findings provide a clear understanding of the roles of Fe-Co interactions over ternary ZnCo x Fe 2-x O 4 catalysts for the highly efficient hydrogenation of CO 2 to produce light olefins. [ABSTRACT FROM AUTHOR]

• MoO x -decorated Ni-based catalysts were fabricated via a single-source precursor route. • As-fabricated Ni-based catalyst was highly active for γ-valerolactone hydrogenolysis. • Surface defective MoO x species facilitated the activation of carbonyl group. • A cooperation between Ni0 species and surface defects contributed to high efficiency. Currently, highly efficient biomass upgrading over non-noble metal catalysts is of vital importance for reducing equipment and operation expenses in biorefinery industries. In this respect, the related heterogeneous catalysis demands the design and construction of mutual cooperative microstructure of catalysts to improve their catalytic performances. Here, an efficient catalytic process for selective hydrogenolysis of biomass-derived γ-valerolactone (GVL) to produce 1,4-pentanediol (1,4-PDO) and 2-methyltetrahydrofuran (2-MTHF) was developed by earth-abundant nickel-based catalysts, which were derived from a molybdate intercalated Ni-Al layered double hydroxide precursor. It was found that with the elevated reduction temperature, the amount of surface defective MoO x species (0 < x < 3) was gradually increased. Especially, as-fabricated Ni-MoO x /Al 2 O 3 catalyst obtained at the reduction temperature of 600 °C delivered a 94.0% combined yield of 1,4-PDO and 2-MTHF under mild reaction conditions. It was demonstrated that over the present Ni-MoO x /Al 2 O 3 catalyst system, surface defective MoO x species could greatly facilitate the adsorption and activation of carbonyl group in GVL and thus significantly promote the cleavage of C O bond and its adjacent C O bond. This finding opens a promising door to engineer surface defective structure of high-performance supported metal catalysts. [ABSTRACT FROM AUTHOR]

New Mn-containing spinel-supported copper nanocatalysts were directly generated via a Cu–Mn–Al layered double hydroxide precursor route and employed in gas-phase hydrogenation of dimethyl succinate (DMS) to γ-butyrolactone (GBL). It was found that the introduction of manganese into catalyst precursors led to the formation of Mn-containing spinel phases, thereby giving rise to highly dispersive Cu 0 nanoparticles and a large number of surface defects (i.e., oxygen vacancies (O v ), Mn 2+ species) in reduced catalysts. As-formed copper-based nanocatalysts exhibited exceptional catalytic hydrogenation performance with stability enduring up to 100 h. Such high catalytic efficiency could reasonably be attributed to the surface synergism between Mn 2+ –O v –Mn 2+ defect structures and active metallic copper species, which controlled the key to hydrogenation related to the adsorption of DMS molecules and following activation of carbonyl groups and the dissociation of hydrogen. Most importantly, such copper-based nanocatalysts displayed great potential applications in the hydrogenations of other biomass-derived compounds containing carbonyl groups (e.g., acetol, levulinic acid, levulinic acid esters, and furfural). The present strategy enables us to tune the surface structures of catalysts for designing new type of copper-based catalysts with significantly enhanced catalytic performance. [ABSTRACT FROM AUTHOR]