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The development of high‐efficiency heterogeneous bifunctional metal‐acid catalysts with an appropriate metal‐acid balance for the production of cyclohexylbenzene (CHB) via the one‐step tandem benzene hydroalkylation still faces a dilemma because of the difficulty in inhibiting the over hydrogenation of benzene substrate and cyclohexene intermediate and controlling target product selectivity. In this study, Nb‐doped WOx supported Pd nanocatalysts were developed. It has been shown that doping Nb into WOx supports altered surface properties and microstructures of catalysts, resulting in the generation of more surface acidic sites and defective W−Ov−Nb structures (Ov: oxygen vacancies). As‐constructed Pd‐based nanocatalyst with only 0.1 wt % Pd loading and a Nb/(Nb+W) molar ratio of 0.25 exhibited superior catalytic benzene hydroalkylation performance to undoped supported Pd catalyst, with a much higher yield of CHB (35.6 %) at 220 °C. It was authenticated that highly dispersed Pd sites facilitated the dissociation of hydrogen molecules, defective W−Ov−Nb structures were conductive to the surface transfer of active hydrogen species, a large number of acidic sites favored benzene/cyclohexene intermediate adsorption, and abundant Brønsted acidic sites promoted the alkylation between cyclohexene intermediate formed and benzene. Accordingly, excellent cooperative catalysis between Pd sites, acidic sites, and oxygen vacancies contributed to improved catalytic performance of Nb‐doped WOx supported Pd catalysts in benzene hydroalkylation. This research presents an alternative for the creation of low‐cost practical bifunctional metal‐acid catalysts for highly efficient benzene hydroalkylation. [ABSTRACT FROM AUTHOR]

Phenol production through the oxidation of cyclohexylbenzene (CHB) and the subsequent decomposition of tertiary hydroperoxide has attracted more and more attention. In this study, defective La2−xCuO4 perovskite-type oxide catalysts with tunable A-site deficient structures and abundant surface oxygen vacancies were developed for the liquid phase oxidation of CHB to produce cyclohexylbenzene-1-hydroperoxide (CHBHP). By tuning the amount of A-site La ions in the perovskite structure, more surface oxygen vacancies and Cu+ species were formed in catalysts. The A-site-deficient La1.9CuO4 catalyst achieved significant catalytic efficiency along with a high CHBHP yield of 27.6% at 48.6% CHB conversion under reaction conditions (i.e., 120 °C and 12 h), outperforming those of other transition metal-based catalysts previously reported in the literature. A series of structural characterization methods and catalytic reactions highlighted the crucial roles of surface oxygen vacancies and metal La and Cu ions in the oxidation process. It was revealed that metal ions favored CHB adsorption and activation, while surface oxygen vacancies facilitated the creation of active adsorbed oxygen species. The present study offers an opportunity for the future design of new high-efficiency heterogeneous catalyst systems for CHB oxidation to obtain phenol. [ABSTRACT FROM AUTHOR]

Series of Ni‐based nanocatalysts were fabricated for the HDO of lignin‐derived guaiacol to cyclohexane via a single‐source Ni−Fe−Al layered double hydroxide precursor route and characterized by XRD, BET, TEM, XAS, XPS, H2‐TPR, H2‐TPD, NH3‐TPD, and pyridine absorbed in situ FT‐IR. As‐fabricated bimetallic NiFe nanocatalyst bearing a Fe/Ni molar ratio of 0.5 : 3 attained a higher cyclohexane yield of 70.5 % under mild reaction conditions (i. e., 230 °C and 1.0 MPa of initial hydrogen pressure), compared to monometallic Ni and other NiFe bimetallic nanocatalysts, as well as monometallic Ni and bimetallic NiFe catalysts prepared by the impregnation method. Combination of experimental results and density functional theory calculations manifested that interfacial FeOx species profoundly facilitated the demethoxylation processes of guaiacol and 2‐methoxycyclohexanol intermediate, while both bimetallic NiFe sites and interfacial FeOx species greatly promoted the dehydroxylation of cyclohexanol intermediate. [ABSTRACT FROM AUTHOR]

In the heterogeneous catalysis, adsorption and desorption behaviors of reactants and products on the surface of catalysts can remarkably impact their catalytic activities and product selectivities. Here, series of Ru‐based catalysts supported on Zn‐incorporated Li−Al layered double hydroxides (Ru/LDH) were developed and employed in the selective benzene hydrogenation to produce cyclohexene without the use of any additional zinc salt additives. It was demonstrated that as‐constructed supported Ru catalyst bearing a Zn/(Li+Zn) molar ratio of 0.075 in the LDH support gave a higher cyclohexene yield of 43.2 % than those over other Ru‐based ones. Combining structural characterizations and catalytic hydrogenation reactions with temperature‐programmed desorption and in situ Fourier transform infrared spectroscopy of benzene and cyclohexene, it was revealed that the generation of appropriate surficial/interfacial Ru0/Ruδ+−O−Zn structures, as well as the existence of abundant hydroxyl groups on LDH supports, could facilitate the benzene adsorption and the cyclohexene desorption, thereby remarkably promoting the formation of cyclohexene. The present findings not only give a profound insight into the roles of surface‐interface structures of supported Ru catalysts for efficient benzene hydrogenation to produce cyclohexene but also simultaneously provide a promising guide to design high‐performance Ru‐based catalysts. [ABSTRACT FROM AUTHOR]

Currently, rapidly increasing consumption of fossil resources has propelled the upgrading of biomass as an alternative and sustainable technology to produce important chemicals and bio-oils. In this regard, the rational design of low-cost and robust supported metal-based catalysts that exhibit excellent catalytic hydrodeoxygenation (HDO) performance for the conversion of biomass is quite necessary. Herein, we developed hierarchical flower-like nitrogen-doped carbon layer-coated bimetallic Ni–Co nanoparticles, which were distributed over the carbonaceous matrix (NixCo@NC@C), via a metal–organic framework (MOF) ZIF-67 precursor approach, assisted by the etching of Ni2+ ions, hydrothermal treatment together with glucose, and following carbonization processes. The as-fabricated Ni3Co@NC@C catalyst bearing a 3 : 1 Ni/Co molar ratio showed a superior catalytic HDO activity towards aqueous phase HDO of vanillin to other bimetallic NiCo catalysts with different Ni/Co molar ratios under mild reaction conditions, along with a 100% selectivity to 2-methoxy-4-methylphenol at a full vanillin conversion, despite its smaller number of exposed metallic sites. It was revealed that over the Ni3Co@NC@C catalyst, the surface abundant defective oxygen vacancies and electron-rich Co0 species were conducive to the adsorption and activation of vanillin and the reaction intermediate, thereby giving rise to the outstanding catalytic activity. Moreover, for Ni3Co@NC@C, the adequate protection effect of surface carbon layers, as well as the unique hierarchical flower-like microstructure, could significantly inhibit the leaching of active metal species in the reaction medium, thereby leading to high structural stability. The present findings afford a promising strategy for constructing low-cost and robust carbon-supported bimetallic catalysts for the HDO of lignin-derived derivatives. [ABSTRACT FROM AUTHOR]

Currently, the hydrodeoxygenation (HDO) process of biomass-derived phenolics is regarded as one of the most promising methods of upgrading to produce various high-value-added chemical raw feeds (e.g., benzene, toluene, and xylene) as well as potentially applied bio-oils with less oxygen content. In this work, a series of surface MoO3-decorated nanosized tetragonal zirconia (t-ZrO2) supports were utilized to immobilize Ru nanoclusters for the aqueous-phase HDO of anisole. Structural characterizations revealed the presence of uniformly dispersed Ru nanoclusters and defective MoOx clusters on the t-ZrO2, thereby forming strong Ru-MoOx interactions and thus the generation of abundant interfacial Ruδ+ species and oxygen vacancies. As-fabricated supported Ru nanoclusters as the catalyst could achieve a much higher benzene selectivity of ∼84.7% than the Mo-free supported Ru one (25.1%) in the HDO of anisole under mild reaction conditions, despite a lowered anisole conversion, which was associated with the cooperative effect between active Ru0 nanoclusters and favorable interfacial Ruδ+-Ov-Mo5+ sites (Ov = oxygen vacancy), thereby enhancing the adsorption of the methoxy group in anisole and the further demethoxylation to form benzene. Our present findings provide a promising way to regulate the selectivity of deoxygenated products in the HDO of biomass-derived phenolics via finely tuning active metal–support interfacial sites. [ABSTRACT FROM AUTHOR]

Currently, the catalytic transformation and utilization of biomass-derived compounds are of great importance to the alleviation of environmental problems and sustainable development. Among them, furfural alcohol derived from biomass resources has been found to be one of the most prospective biomass platforms for high-value chemicals and biofuels. Herein, high-surface-area ZrO2 with abundant oxygen defects and surface acid–base sites was synthesized and used as a heterogeneous catalyst for the catalytic transfer hydrogenation of furfural into furfural alcohol using alcohol as a hydrogen donor. The as-synthesized ZrO2 exhibited excellent catalytic performance with 98.2% FA conversion and 97.1% FOL selectivity, even comparable with that of a homogeneous Lewis acid catalyst. A series of characterization studies and experimental results revealed that acid sites on the surface of ZrO2 could adsorb and activate the C＝O bond in furfural and base sites could facilitate the formation of alkoxide species. The synergistic effect of surface acid–base sites affords a harmonious environment for the reaction, which is crucial for catalytic transfer hydrogenation of furfural with high efficiency. Furthermore, the as-prepared ZrO2 catalyst also exhibited a potential application for the efficient catalytic transfer hydrogenation of a series of biomass-derived carbonyl compounds. [ABSTRACT FROM AUTHOR]

In the present work, a novel hybrid nanocomposite of bimetallic Co–Ni hydroxide and polyaniline-modified partially reduced graphene oxide (PRGO) was assembled via in situ growth route for supercapacitor application. A series of characterizations demonstrated that large quantities of bimetallic Co–Ni hydroxide nanosheets could longitudinally grow on the surface of PRGO substrate and intercross together, forming a hierarchical honeycomb-like micro/nanostructure array. As-assembled CoNi(OH)2/PRGO nanocomposite showed a much higher specific capacitance of 2760 ± 160 F g−1 at 1.0 A g−1 in three-electrode measurements, in comparison with pristine bimetallic Co–Ni hydroxide, Co(OH)2/PRGO, and Ni(OH)2/PRGO reference electrodes, which originated from the synergy effect between component units and unique three-dimensional conductive porous framework of nanocomposite, thereby greatly promoting the redox processes of metal ions and facilitating the ion diffusion between the electrolyte and the electrode, as well as the electron transfer. Furthermore, after 1000 charge–discharge cycles, as-assembled nanocomposite electrode possessed good cycling stability, along with a high 93.2% retention level of capacitance at 10 A g−1. An asymmetric flexible all-solid-state supercapacitor device was equipped with poly (vinyl alcohol) film as the solid electrolyte, and as-assembled CoNi(OH)2/PRGO as the positive electrode delivered a 74.84 ± 1.46 wh kg−1 energy density and a 374.34 ± 0.15 w kg−1 power density at 0.5 A g−1, indicating good supercapacitor performance for energy storage and applications in flexible and wearable electronics. [ABSTRACT FROM AUTHOR]

In this work, a new hybrid composite of hydroxyapatite and Ca–Al layered double hydroxide (HAP-LDH) was successfully assembled via an in situ growth route, by which large quantities of small needle-like HAP crystals in situ grew over the lateral surface of large platelet-like CaAl-LDH particles, and applied to immobilize Au nanoparticles for base-free aerobic glucose oxidation in water to produce gluconic acid using molecular oxygen. A combination of characterization techniques and catalytic experiments revealed that the activity of supported Au catalysts was strongly associated with the composition of supports, and the hybrid HAP-LDH supported one with a Au loading amount of about 0.2 wt% delivered a high gluconic acid yield of ＞98% under optimal reaction conditions, along with a quite high turnover frequency value of ∼20 225 h−1. High efficiency of the as-formed Au/HAP-LDH was mainly ascribed to cooperation between favorable surface Au species (Au0/Auδ+) and abundant basic sites. Furthermore, the present catalyst also presented good structural stability, because of the novel hybrid three-dimensional nano/microstructure of the HAP-LDH composite support facilitating the stabilization of active Au species and components of the support. The present synthesis strategy of employing a hybrid composite support provides a new way to design stable and high-performance supported metal nanocatalysts for a variety of advanced heterogeneous catalytic processes. [ABSTRACT FROM AUTHOR]

Exploring high-performance and stable electrocatalysts for the oxygen evolution reaction (OER) is critical for the conversion and storage of renewable energy. Herein, a novel strategy was developed for the construction of dispersive nickel phosphide (Ni2P) embedded in two-dimensional (2D) amorphous alumina arrays on three-dimensional (3D) nickel foam (NiP–Al2O3/NF) electrocatalysts via the reduction of a layered double hydroxide (LDH) precursor. Owing to its unique 3D nano/micro-architecture, multi-porous structure, interconnected conductive skeleton, and highly dispersive Ni2P active sites, the NiP–Al2O3/NF electrocatalyst exhibited excellent OER activity with overpotential as low as 193 mV at 10 mA cm−2 in a 1.0 M KOH solution and superior catalytic activity for the oxidation of 5-hydroxymethylfurfural in alkaline media. Density functional theory calculations demonstrated that the introduction of P to Ni could effectively reduce the OER overpotential. Furthermore, benefiting from the flexibility of compositional tailoring of both the brucite-like layers and interlayer anions of LDHs, the synthesis strategy presented here can be easily extended to the fabrication of various nanostructured noble-metal-free functional materials, which are expected to have wide application prospects in many domains, especially in catalysis. [ABSTRACT FROM AUTHOR]

Abstract: Currently, the base‐free aerobic oxidation of biomass‐derived 5‐hydroxymethylfurfural (HMF) to produce 2,5‐furandicarboxylic acid (FDCA) is attracting intense interest due to its prospects for the green, sustainable, and promising production of biomass‐based aromatic polymers. Herein, we have developed a new Pt catalyst supported on nitrogen‐doped‐carbon‐decorated CeO2 (NC‐CeO2) for the aerobic oxidation of HMF in water without the addition of any homogeneous base. It was demonstrated that the small‐sized Pt particles could be well dispersed on the surface of the hybrid NC‐CeO2 support, and the activity of the supported Pt catalyst depended strongly on the surface structure and properties of the catalysts. The as‐fabricated Pt/NC‐CeO2 catalyst, with abundant surface defects, enhanced basicity, and favorable electron‐deficient metallic Pt species, enabled an almost 100 % yield of FDCA in water with molecular oxygen (0.4 MPa) at 110 °C for 8 h without the addition of any homogeneous base, which is indicative of exceptional catalytic performance. Furthermore, this Pt/NC‐CeO2 catalyst also showed good stability and reusability owing to strong metal–support interactions. An understanding of the role of surface structural defects and basicity of the hybrid NC‐CeO2 support provides a basis for the rational design of high‐performance and stable supported metal catalysts with practical applications in various transformations of biomass‐derived compounds. [ABSTRACT FROM AUTHOR]

Tuning the surface properties of supported metal catalysts is of vital importance for governing their catalytic performances in nanocatalysis. Here, we report highly dispersed nanometric gold nanoparticles (NPs) supported on Ni–Ti layered double hydroxides (NiTi-LDHs), which were employed in solvent-free and base-free selective oxidation of benzyl alcohol. A series of characterization techniques demonstrated that defect-rich NiTi-LDHs could efficiently stabilize Au NPs and decrease surface electron density of Au NPs. The as-formed Au/NiTi-LDH catalyst with a Ni/Ti molar ratio of 3 : 1 and an Au loading of 0.71 wt% yielded the highest turnover frequency value of ∼4981 h−1 at 120 °C among tested Au/NiTi-LDH catalysts with different Ni/Ti molar ratios, along with a high benzaldehyde selectivity of 98%. High catalytic efficiency of the catalyst was mainly correlated with surface cooperation between unique defects (i.e. defective Ti3+ species and oxygen vacancies) and abundant hydroxyl groups on the brucite-like layers of the NiTi-LDH support, which could lead to the preferential adsorption and activation of an alcohol hydroxyl moiety in benzyl alcohol and oxygen molecule, as well as the formation of more electron-deficient Ni3+ and Au0 species on the catalyst surface. Furthermore, the present Au/NiTi-LDH catalyst tolerated the oxidation of a wide variety of substrate structures into the corresponding aldehydes, acids or ketones. Our primary results illustrate that defect-rich NiTi-LDHs are promising supports which can efficiently modify surface structure and electronic properties of supported metal catalysts and consequently improve their catalytic performances. [ABSTRACT FROM AUTHOR]

2,5-Dimethylfuran (DMF) and phenol are considered as one of the new-fashioned liquid transportation biofuels and a key motif for industrial chemicals, respectively. Herein, a highly efficient vapor-phase dehydrogenation–hydrogenation coupling process over bimetallic Ni–Cu alloy nanocatalysts was established for the synchronized production of phenol and DMF with unprecedentedly high yields (＞97%) from two cyclohexanol (CHL) and biomass-derived 5-hydroxymethylfurfural (HMF) substrates, without any external hydrogen and oxygen supply. Systematic characterization and catalytic experiments revealed that the production of phenol went through a consecutive triple-dehydrogenation process from CHL, while HMF was simultaneously hydrogenated into DMF using active hydrogen species generated from the dehydrogenation process. The bimetallic Ni–Cu alloy nanostructures derived from Ni–Cu–Al layered double hydroxide precursors and strong metal–support interactions play important roles in governing the present coupling process. An appropriate Ni–Cu alloy nanostructure could greatly facilitate the dehydrogenative aromatization of CHL, thus significantly improving the selectivities to both phenol and DMF. Such an unparalleled efficient, eco-friendly and versatile coupling process for the synchronized production of various substituted phenols and DMF makes it practically promising for large-scale industrial applications in terms of green chemistry and sustainable development. [ABSTRACT FROM AUTHOR]

In this work, nitrogen-doped carbon modified MgO–MgFe2O4 (CN-MgFeO) magnetic composites were synthesized by a facile thermal decomposition of Mg–Fe layered double hydroxide (MgFe-LDH) and cyanamide mixture precursors. A series of comprehensive characterization studies including powder X-ray diffraction, transmission electron microscopy, Fourier transform infrared of CO2 adsorption, CO2-temperature programmed desorption, and X-ray photoelectron spectroscopy indicated that the introduction of cyanamide could finely tune the surface basicity of the resulting CN-MgFeO composites, especially surface strong Lewis basicity. Compared with CN-free MgFeO, the as-fabricated CN-MgFeO catalysts showed higher activity in the liquid-phase transesterification of tributyrin with methanol. Particularly, the CN-MgFeO composite prepared at a cyanamide/Mg molar ratio of 1.5 in the synthesis mixture gave a highest methylbutyrate yield of 80% after a reaction for 20 min. The high catalytic performance was attributable to the presence of a large amount of strong Lewis basic sites originating from highly dispersed basic MgO–MgFe2O4 mixed metal oxides and CN component in the composite. What is more, such a cost-effective CN-MgFeO catalyst had the advantages of intrinsic magnetic properties and an excellent structural stability. We expect that they may have potential practical applications in the field of industrial production of biodiesels. [ABSTRACT FROM AUTHOR]

The catalytic production of methyl methacrylate through the direct oxidative esterification of methacrolein is important in terms of green chemistry and sustainable development. In the present work, Au nanoparticles supported on three needle-like, lamella-like, and rodlike hydroxyapatites were synthesized. We demonstrated that needle-like hydroxyapatite could facilitate the higher dispersion of Au species because of its high specific surface area, and the strong interaction between the Au nanoparticles and the support resulted in the formation of more surface defects because of the existence of partially encapsulated Au particles by the needle-like hydroxyapatite. The surface defects were related closely to the generation of strong basic sites. Compared with the other two materials, the Au supported on the needle-like hydroxyapatite catalyst, which had a large amount of surface acid-base sites, exhibited a much higher catalytic activity and selectivity to methyl methacrylate in the direct oxidative esterification of methacrolein with methanol under mild reaction conditions (i.e., ambient pressure, low reaction temperature of 70 °C, and low methanol/aldehyde ratio of 8:1). The superior catalytic performance of the Au supported on needle-like hydroxyapatite catalyst was attributable to a cooperative effect between abundant acid-base sites for the preferential chemisorption of methacrolein and highly dispersed active Au species for the favorable formation of β-hydride and oxygen activation. The present findings open a new and promising route for the practical production of methyl methacrylate using high-performance hydroxyapatite-supported metal catalyst systems. [ABSTRACT FROM AUTHOR]

A facile and economical strategy to synthesize high surface area Mg-doped ZnAl2O4 spinels is developed. These materials are employed as catalyst supports to prepare supported gold catalysts for the aerobic oxidation of benzyl alcohol by using molecular oxygen in the absence of additional alkali. The as-fabricated supported Au catalyst with the Mg/(Mg+Zn) molar ratio of 0.15 was found to show good catalytic activity with high benzaldehyde selectivity (>99%) and a high turnover frequency of 5382h-1. The relationship between the surface properties of the supported Au catalysts and their catalytic performances reveals that the high catalytic efficiency is mainly attributable to surface cooperative effects between the abundant basic sites and favorable active Au species, including metallic Au and cationic Auδ+ ions. A possible mechanism for selective oxidation of benzyl alcohol is tentatively proposed. Moreover, the as-fabricated supported Au catalyst could be reused at least four times without significant loss of its catalytic performance. The present finding provides a new route for designing high-performance supported noble or non-noble metal catalysts by using high surface area ZnAl2O4-based spinels. [ABSTRACT FROM AUTHOR]

The synthesis of highly efficient supported metal catalysts is of vital importance for the modern development of the production of chemicals. In this regard, biomass-based chemical transformation holds potential promise through many heterogeneous catalytic processes. Herein, we report surface defect engineering on a carbon-supported, Ru-based catalyst by a two-step hybridization-self-reduction route, which involves the assembly of a hybrid composite of ternary Co-Al-Ru layered double hydroxide (CoAlRu-LDH) and amorphous carbon through the carbonization of glucose and a subsequent in situ self-reduction process. The results revealed that Ru3+ species in the resulting CoAlRu-LDH-C composite could be reduced in situ to Ru0 species by the carbon component in the hybrid composite, and Co-containing spinels with a large quantity of surface oxygen vacancies could be formed simultaneously on the surface. The as-fabricated Ru-based catalyst showed a superior catalytic performance in the liquid-phase transfer hydrogenation of furfural to furfuryl alcohol using benzyl alcohol as hydrogen donator to other Ru-based catalysts derived from LDH-C composite precursors. It was proven that surface defects (i.e., oxygen vacancies, Co2+ species) could enable the chemisorption of furfural spatially and ensure the activation of its carbonyl groups, which promoted the transfer hydrogenation greatly. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, we report a facile synthetic approach for supported copper nanocatalysts with a thin nitrogen‐doped carbon (CN) overlayer. This Cu@CN catalyst was directly generated by a thermal decomposition of Cu‐Al layered double hydroxide (CuAl‐LDH)/melamine hybrid precursor, and employed in the liquid‐phase transfer dehydrogenation of primary aliphatic alcohols. The strategy was found to be useful for the formation of a very thin in situ formed CN overlayer of 0.5–0.7 nm in thickness on copper nanoparticles of about 8.5 nm in diameter. Compared with uncoated copper‐based catalyst derived from pristine CuAl‐LDH, as‐fabricated Cu@CN catalyst showed significantly enhanced catalytic activity, which was attributed to the surface cooperative effect among strong Lewis base sites originating from the CN layer, well‐dispersed Cu0 nanoparticles and Cu+ species, thereby greatly promoting the activation of hydroxyl group in primary aliphatic alcohols and the following abstraction and transfer of hydrogen. Most importantly, the thin CN overlayer could successfully stabilize copper nanoparticles, thus preventing the leaching and the growth of copper species over the course of the reaction. This work offers a new strategy for fabricating cost‐effective, highly efficient and extremely stable supported copper catalysts for the transfer dehydrogenation of primary aliphatic alcohols. [ABSTRACT FROM AUTHOR]

With ever increasing demand of sustainable energy, biomass has been regarded as an ideal alternative to fossil resources. Herein, hierarchical three-dimensional nickel-based nanowalls on a nickel foam substrate were fabricated by a Ni-Zr-Al layered double hydroxide (NiZrAl-LDH) precursor route, which involved in situ growth of the Zr-containing precursor on the Ni foam strut through surface activation without an external nickel source. After calcination-reduction treatment, the nanowalls were applied as a structured catalyst for selectively hydrogenating biomass-derived levulinic acid to γ-valerolactone. Systematic characterization revealed that highly dispersed Ni nanoparticles could be generated on the platelet-like Zr-containing oxide matrix derived from hierarchical 3 D NiZrAl-LDH nanowalls. Under vapor-phase, solvent-free hydrogenation conditions (250 °C, ambient pressure), the yield and productivity for as-fabricated Ni-based structured catalyst could reach as high as 97.7 % and 5.747 kgGVL kgcat−1 h−1, respectively. Such high catalytic efficiency was reasonably attributable to highly dispersed Ni nanoparticles and abundant surface Lewis acid sites, as well as favorable heat-transfer nature of present catalytic system. Moreover, the newly developed structured nanowall-like Ni-based catalyst possesses high structural and chemical stability, which makes the vapor-phase hydrogenation process promising in terms of green sustainable chemistry. [ABSTRACT FROM AUTHOR]

A solvent-free gas-phase coupling process through hydrogen transfer without external hydrogen supply over novel bifunctional base-metal heterogeneous catalysts was developed for the simultaneous production of γ-butyrolactone and furfuryl alcohol with high yields of 95.0% from biomass-derived compounds. Such a practical, unparallely efficient and environmentally benign process makes it promising in terms of both green sustainable chemistry and industrial perspective. [ABSTRACT FROM AUTHOR]

Controlling the metal–support interactions, as well as the nature of support materials, is of vital importance for enhancing the catalytic performance of supported metal catalysts. In the present work, supported nickel nanocatalysts with abundant surface defects (e.g. oxygen vacancies, Ti3+ species) were directly synthesized via a facile single-source Ni–Ti layered double hydroxide precursor route, and their catalytic performance in the liquid phase selective hydrogenation of chloronitrobenzenes to chloroanilines was investigated. A series of characterization techniques including XRD, TEM, STEM, PL, XPS, H2–TPR and H2 chemisorption clearly demonstrated that the resultant Ni nanoparticles were uniformly dispersed on the surface of the Ni–Ti mixed metal oxide support formed in situ, thereby leading to strong metal–support interactions and the formation of a large amount of surface oxygen vacancies and Ti3+ species. Compared with that prepared using a conventional impregnation method, the as-formed Ni-based nanocatalysts exhibited significantly enhanced catalytic performance with a high chloroaniline yield of 99.0% under mild reaction conditions (i.e. a low hydrogen pressure of 0.2 MPa). Such an unprecedented catalytic efficiency was mainly attributed to the promotional effect of surface defects. Furthermore, the present Ni-based nanocatalysts could be reused five times without serious aggregation of active species and remarkable activity loss, indicative of high stability. [ABSTRACT FROM AUTHOR]

In the present work, a La-doped Mg–Al mixed metal oxide supported copper catalyst (Cu/La–MgAlO) was synthesized through a layered double hydroxide precursor route. The materials were characterized by powder X-ray diffraction, transmission electron microscopy, CO2-temperature programmed desorption, Fourier transform infrared spectra of CO2 absorption, and X-ray photoelectron spectroscopy. The results revealed that the introduction of a trace amount of La could significantly improve the surface basicity of the Cu/La–MgAlO catalyst, especially strong Lewis basicity. Compared with the undoped supported Cu catalyst, Cu/La–MgAlO exhibited much higher activity and selectivity in the liquid-phase transfer dehydrogenation of 1-decanol with a 1-decanal yield up to 89%. The excellent catalytic efficiency was mainly ascribed to the surface cooperation between the Lewis basic sites and the adjacent Cu0/Cu+ species. That is, basic sites, especially strong-strength basic sites, held the key to the abstraction of protons from the hydroxyl group in 1-decanol, while the adjacent Cu0 and Cu+ species were responsible for the hydrogen transfer and the adsorption of styrene in the transfer dehydrogenation and hydrogenation reactions, respectively. This study provides a new method for designing cost-effective supported copper-based catalysts highly efficient for the transfer dehydrogenation of primary aliphatic alcohols by modifying the surface basicity of metal oxide supports. [ABSTRACT FROM AUTHOR]

The selective oxidation of alkylaromatics is of vital importance for the production of high-added-value raw materials. The development of highly efficient heterogeneous catalytic oxidation systems under mild conditions has become an attractive research area. In this work, hybrid Co-Cu-Al layered double hydroxide/graphene (CoCuAl-LDH/graphene) nanocomposites, which were assembled successfully by a one-step coprecipitation route without the use of any additional reducing agents, were used as highly efficient catalysts for the liquid-phase selective oxidation of ethylbenzene using tert-butyl hydroperoxide as the oxidant. A series of characterizations revealed that graphene could stabilize CoCuAl-LDH nanoplatelets effectively in the nanocomposites, and in turn, highly dispersed CoCuAl-LDH could prevent the aggregation of the graphene nanosheets. By fine-tuning the mass ratio of graphene to CoCuAl-LDH, such nanocomposites offered a tunable catalytic oxidation performance. In particular, the nanocomposite with the graphene/CoCuAl-LDH mass ratio of 0.4:1 exhibited a remarkable catalytic performance with a considerable conversion (96.8 %) and selectivity to acetophenone (>95.0 %), which was mainly attributed to the synergism between the active CoCuAl-LDH component and the graphene matrix in the unique hetero-nanostructure. Moreover, the as-assembled nanocomposite catalysts displayed good recyclability and were active for the selective oxidation of other alkylaromatics. [ABSTRACT FROM AUTHOR]

The efficient gas-phase selective hydrogenation of a series of esters to the corresponding alcohols was achieved over well-dispersed aluminum-doped zirconia-supported copper nanocatalysts (Cu/Al-ZrO2), which were prepared through a homogeneous coprecipitation route in the presence of cetyl trimethyl ammonium bromide. The characterization revealed that the structure and catalytic performance of Cu/Al-ZrO2 nanocatalysts were profoundly affected by the addition of Al. Compared with the Al-free catalyst, Al-doped materials had higher specific surface areas and smaller copper nanoparticles. In particular, the results confirmed that the incorporation of Al into the ZrO2 framework could form tetrahedrally coordinated Al3+ species, leading to the improvement of metal dispersion and the formation of more surface Lewis acid sites. In the gas-phase selective hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG), 100 % DMO conversion, 97.1 % EG selectivity, and a high turnover frequency of 16.9 h−1 were achieved over Cu/Al-ZrO2 catalyst with a Al/(Cu+Zr+Al) mass ratio of 0.1. The high efficiency of Cu/Al-ZrO2 catalysts in DMO hydrogenation was attributed mainly to the surface synergistic catalytic effect between highly dispersed metallic copper species and strong Lewis acid sites, which promoted the hydrogenation reaction related to the ester groups, unlike the single case of Cu+Cu0 synergy reported previously that was found to control the extent of hydrogenation. The obtained catalysts displayed excellent catalytic performance in the gas-phase hydrogenation of other esters including dimethyl succinate, dimethyl maleate, dimethyl adipate, and 1,4-cycolhexane dicarboxylate. [ABSTRACT FROM AUTHOR]

Control of the dispersion and size of metallic nanoparticles, as well as metal-support interaction, is of vital importance to enhance the catalytic performance of supported metal nanocatalysts. In this work, carbon-supported boron-promoted Ni nanocatalysts (B-Ni) were synthesized via an in situ self-reduction process of hybrid borate-intercalated NiAl-layered double hydroxide/carbon nanocomposites, and the promotional effect of boron on the catalytic performance of Ni nanocatalysts formed in liquid phase hydrodechlorination of chlorobenzene was studied. A series of XRD, TEM, STEM, XPS, low temperature N2 adsorption, and H2 chemisorption results revealed that the resulting spherical B-modified Ni nanoparticles were homogeneously dispersed and anchored tightly on the surface of the carbon support. A suitable amount of boron was essential for the formation of highly dispersed and uniform nanoparticles and pronounced surface Ni-B interaction, as well as strong Ni-B-support interactions, accounting for the significantly enhanced hydrodechlorination activity, in comparison with a B-free Ni catalyst. Moreover, as-synthesized B-Ni nanocatalysts exhibited good stability, without obvious aggregation and loss of active species after five recycles. [ABSTRACT FROM AUTHOR]

In this paper, graphene-supported Ni nanocatalyst (Ni/G) was prepared via self-reduction of a hybrid Ni-Al layered double hydroxide/graphene (NiAl-LDH/G) composite precursor. NiAl-LDH/G nanocomposite was assembled via a facile one-step coprecipitation route, which involved the nucleation and growth of NiAl-LDH, simultaneously accompanied by the reduction of graphene oxide without the addition of any reducing agents. The characterization results demonstrated that NiAl-LDH nanoplatelets were homogeneously dispersed on both sides of an exfoliated, structurally flexible graphene The graphene component in the precursor, serving as reducing agent, could in situ reduce Ni[sup 2+] species to Ni[sub 0] on heating under an inert atmosphere, thus facilitating the formation of highly dispersed Ni nanoparticles with a uniform size. Compared with those prepared by conventional methods, as-formed graphene-supported Ni nanocatalyst exhibited superior catalytic performance in the liquid phase selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde owing to the much higher metal dispersion and smaller size of Ni nanoparticles in the catalyst. The present finding provides a simple approach to fabricate new types of graphene-supported, metal-based heterogeneous catalysts with advanced catalytic performance. [ABSTRACT FROM AUTHOR]

The uniform Pd nanoparticles were immobilized on the surface of spinel-type ZnAlO support for Suzuki-Miyaura coupling reactions. High-surface-area ZnAlO support with microporous framework was successfully synthesized utilizing concurrent hexamethylenetetramine hydrolysis and homogeneous coprecipitation induced spontaneously under solvothermal conditions. The obtained support Pd catalyst was used as heterogeneous and recyclable catalyst for the Suzuki-Miyaura coupling reaction in an environmentally friendly ethanol solvent under ligand-free ambient conditions, and exhibited excellent catalytic activity. The remarkable catalytic activity is attributed to the homogeneous distribution of small Pd nanoparticles on the ZnAlO matrix as well as the strong metal-support interaction. Furthermore, the catalytic activity did not deteriorate after recycling for five times, suggestive of the good stability of the catalyst. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The gas-phase hydrogenation of dimethyl 1,4-cyclohexane dicarboxylate to 1,4-cyclohexane dimethanol was performed on a well-dispersed Cr-free supported copper-based catalyst derived from a Cu–Mg–Al layered double hydroxide precursor, and achieved a lasting 100% conversion with 99.8% selectivity up to 200 hours. The unprecedented catalytic performance is ascribed to the synergistic effect between surface active Cu0 sites and Lewis base sites. [ABSTRACT FROM AUTHOR]

Spinel-type zinc aluminate (ZnAl2O4) thin films with controlled surface microstructure on aluminum substrates were fabricated via a facile and effective in situ crystallization method without using any templates or surfactants. The surface microstructure of ZnAl2O4 films could be significantly controlled by varying the experimental conditions including concentration of reactants, crystallization temperature, and crystallization time. After surface modification, the specific topography of ZnAl2O4 films was beneficial to obtain surface hydrophobic or superhydrophobic properties. More importantly, compared to nanoparticle- and nanosword-assembled ZnAl2O4 films, nanorod-assembled ZnAl2O4 film provided a more effective barrier to aggressive species for aluminum substrates in a wide range of pH values; very low corrosion current density of the order of ∼10−19 A cm−12 could be achieved. A new contribution to the development of advanced coating system with ZnAl2O4 film materials that can be used in practical application for corrosion protection of aluminum materials is provided. © 2011 American Institute of Chemical Engineers AIChE J, 2012 [ABSTRACT FROM AUTHOR]

The highly-dispersed copper-based catalysts for the gas-phase hydrogenation of dimethyl oxalate to ethylene glycol (EG) were prepared from a Cu-Zn-Al layered double hydroxide (LDH) precursor. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N adsorption-desorption, H temperature programmed reduction (H-TPR) and H-NO titration indicated that the composition, texture, and structure of resulting copper-based catalysts were profoundly affected by the calcination temperature of LDH precursor. Moreover, the as-synthesized catalyst calcined at 600 °C was found to exhibit a superior catalytic hydrogenation performance with an EG yield of 94.7 % to the other catalysts calcined at 500 and 700 °C, which should be mainly attributed to the presence of the highly-dispersed active metallic copper species over metal oxide matrix. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Nickel ferrite (NiFe2O4) films with macroporous frameworks are successfully fabricated on silicon substrates viaa novel template-assisted route. The fabrication approach mainly involves the formation of two-phase composite (desired nickel ferrite and nickel oxide phases) films by thermal conversion of Ni–Fe layered double hydroxide precursor films followed by a selective leaching of self-generated NiO template from the two-phase composite films. The microstructural, magnetic and interfacial properties of the resulting films were characterized by means of X-ray diffraction (XRD), chemical analyses, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). The results revealed that the microstructures (e.g.particle sizes and spacing among particles), magnetism and surface hydrophobic property of as-fabricated NiFe2O4films could be finely tuned by varying the composition of precursor films. The increasing Ni/Fe ratio in precursor films leads to reduced particle sizes and enlarged spacing among ferrite particles in NiFe2O4films. Furthermore, the as-fabricated NiFe2O4films show tunable saturation magnetization varying from 36 to 55 emu/g and excellent surface hydrophobicity ranging from 139 to 152° after surface modification of films. We believe that such unique macroporous NiFe2O4films can open up new opportunities for a wide range of advanced applications. [ABSTRACT FROM AUTHOR]

Nickel ferrite (NiFe2O4) films with macroporous frameworks are successfully fabricated on silicon substrates viaa novel template-assisted route. The fabrication approach mainly involves the formation of two-phase composite (desired nickel ferrite and nickel oxide phases) films by thermal conversion of Ni–Fe layered double hydroxide precursor films followed by a selective leaching of self-generated NiO template from the two-phase composite films. The microstructural, magnetic and interfacial properties of the resulting films were characterized by means of X-ray diffraction (XRD), chemical analyses, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). The results revealed that the microstructures (e.g.particle sizes and spacing among particles), magnetism and surface hydrophobic property of as-fabricated NiFe2O4films could be finely tuned by varying the composition of precursor films. The increasing Ni/Fe ratio in precursor films leads to reduced particle sizes and enlarged spacing among ferrite particles in NiFe2O4films. Furthermore, the as-fabricated NiFe2O4films show tunable saturation magnetization varying from 36 to 55 emu/g and excellent surface hydrophobicity ranging from 139 to 152° after surface modification of films. We believe that such unique macroporous NiFe2O4films can open up new opportunities for a wide range of advanced applications. [ABSTRACT FROM AUTHOR]