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A series of Ni catalysts supported on alumina with different Ce contents(1.0%–6.0%, mass fraction) was prepared by the impregnation method and used for dry reforming of methane(DRM) at a relatively low temperature of 650 °C. The promotion effect of Ce with different loading amounts on the physicochemical properties of the catalysts was systematically characterized by transmission electron microscopy(TEM), X-ray diffraction(XRD), N2 adsorption-desorption, thermo elemental IRIS Intrepid inductively coupled plasma atomic emission spectrometer (ICP-AES), UV-visible diffuse reflectance spectroscopy(UV-Vis DRS), Fourier transformation infrared(FTIR) spectra, H2-temperature programmed reduction(H2-TPR) analysis, H2-temperature programmed desorption(H2-TPD), and The X-ray photoelectron spectroscopy(XPS) techniques. The results indicate that all the catalysts mainly exist in the NiAl2O4 phase after being calcined at 750 °C with small Ni particle sizes due to the strong metal-support interaction derived from the reduction of the NiAl2O4 phase. The Ce-promoted catalysts show better catalytic performance as well as the resistance against sintering of Ni particles and deposition of carbon compared to the Ni/Al2O3 catalyst. The Ni-6Ce/Al2O3 exhibits the best catalytic stability and coke resistance among the four catalysts studied, which is due to its small Ni nanoparticles sizes, excellent reducibility as well as high amount of active oxygen species. In a 400 h stability test for DRM reaction at 650 °C, Ni-6Ce/Al2O3 exhibits less coke deposition and small growth of Ni nanoparticles. This work provides a simple way to preparing the Ni-Ce/Al2O3 catalyst with enhanced catalytic performance in DRM. The Ni-6Ce/Al2O3 catalyst has great potential for industrial application due to its anti-sintering ability and resistance to carbon deposition.

Niobium oxides and tantalum oxides are typical solid acid catalysts that exhibit high activity and high water-resistance in the aqueous environment. To understand their acid catalytic performance, ...

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Cuprous oxide microcrystals with {111}, {111}/{100}, and {100} exposed facets were synthesized. 31 P MAS NMR using trimethylphosphine as the probe molecule was employed to study the acidic properties of samples. It was found that the total acidic density of samples increases evidently after sulfation compared with the pristine cuprous oxide microcrystals. During sulfation, new {100} facets are formed at the expense of {111} facets and lead to the generation of two Lewis acid sites due to the different binding states of SO42- on {111} and {100} facets. Moreover, DFT calculation was used to illustrate the binding models of SO42- on {111} and {100} facets. Also, a Pechmann condensation reaction was applied to study the acidic catalytic activity of these samples. It was found that the sulfated {111} facet has better activity due to its higher Lewis acid density compared with the sulfated {100} facet.

Ni-based catalysts supported on alumina derived from the pseudo-boehmite prepared by the impregnation method were employed for catalytic dry reforming of methane reaction at the temperature of 550–750 °C. The effect of calcination temperature on physicochemical properties such as the Ni dispersion, reduction degree, nickel crystallite sizes, and metal–support interaction of the catalysts was investigated. The characterization results show that increasing the catalyst calcination temperature leads to the formation of nickel-alumina spinel, which enhances the metal–support interaction and increases the reduction temperature. The nickel nanoparticle size decreases and the effective dispersion increases with the increasing calcination temperature from 450 °C to 750 °C due to the formation of nickel aluminate. The catalyst calcined at 750 °C exhibits the highest CH4 and CO2 conversion owing to the small Ni0 active sites and high Ni dispersion. In a 200 h stability test in dry reforming of methane at 700 °C, the Ni/Al2O3-750 catalyst exhibits excellent catalytic stability and anti-coking ability.

In this work various amount of phosphomolybdic acid (PMo) were immobilized on amine functionalized SBA-15 and used as heterogeneous catalysts in the epimerization of glucose in aqueous solution. 13.3PMo/NH2-SBA-15 exhibited the best catalytic performance with a glucose conversion of 34.8% and mannose selectivity of 85.6% within two hours at 120 &deg, C. The activation energy of 80.1 &plusmn, 0.1 kJ&middot, mol&minus, 1 was lower than that of 96 kJ&middot, 1 over the homogeneous H3PMo12O40 catalyst. The catalytic activities of 13.3PMo/NH2-SBA-15 for the transformation of some other aldoses including mannose, arabinose and xylose were also investigated.

Ni/Al 2 O 3 catalysts were derived from spinel NiAl 2 O 4 with different Ni content ((2.5, 5 and 7.5) wt%). The catalysts were obtained by H 2 reduction and were investigated for the low-temperature hydrogenation of maleic anhydride (MA) to produce succinic anhydride (SA). The characterization results showed that Ni 0 active sites were mainly derived during the H 2 reduction from spinel NiAl 2 O 4 . Among the catalysts studied, employing the optimum preparation and reaction conditions with Ni(5%)/Al 2 O 3 yielded the highest catalytic performance. A near-100% conversion of MA and ∼90% selectivity to SA were achieved at 120 °C and 0.5 MPa of H 2 with a weighted hourly space velocity (MA) of 2 h −1 .

In the present study, we assembled and compared two mitogenomes from the Rhizopogon genus. The two mitogenomes of R. salebrosus and R. vinicolor comprised circular DNA molecules, with the sizes of 66,704 bp and 77,109 bp, respectively. Comparative mitogenome analysis indicated that the length and base composition of protein coding genes (PCGs), rRNA genes and tRNA genes varied between the two species. Large fragments aligned between the mitochondrial and nuclear genomes of both R. salebrosus (43.41 kb) and R. vinicolor (12.83 kb) indicated that genetic transfer between mitochondrial and nuclear genomes has occurred over evolutionary time of Rhizopogon species. Intronic regions were found to be the main factors contributing to mitogenome expansion in R. vinicolor. Variations in the number and type of introns in the two mitogenomes indicated that frequent intron loss/gain events occurred during the evolution of Rhizopogon species. Phylogenetic analyses based on Bayesian inference (BI) and Maximum likelihood (ML) methods using a combined mitochondrial gene set yielded identical and well-supported tree topologies, wherein Rhizopogon species showed close relationships with Agaricales species. This is the first study of mitogenomes within the genus Rhizopogon, and it provides a basis for understanding the evolution and differentiation of mitogenomes from the ectomycorrhizal fungal genus.

Three morphology-controlled CeO2, namely nanorods (NRs), nanocubes (NCs), and nanopolyhedra (NPs), with different mainly exposed crystal facets of (110), (100), and (111), respectively, have been used as supports to prepare Ru (3 wt.%) nanoparticle-loaded catalysts. The catalysts were characterized by H2-temperature programmed reduction (H2-TPR), CO&ndash, temperature programmed desorption (CO-TPD), N2 adsorption&ndash, desorption, X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (XDS). The characterization results showed that CeO2-NRs, CeO2-NCs, and CeO2-NPs mainly expose (110), (100) and (111) facets, respectively. Moreover, CeO2-NRs and CeO2-NCs present higher oxygen vacancy concentration than CeO2-NPs. In the CO2 reforming of methane reaction, Ru/CeO2-NR and Ru/CeO2-NC catalysts showed better catalytic performance than Ru/CeO2-NPs, indicating that the catalysts with high oxygen vacancy concentration are beneficial for promoting catalytic activity.

Four isostructural polyoxometalates consisting of Nb/W mixed addenda Dawson-type subunits and lanthanide ions, K4Na8H4{[Nb4O6(H2O)4Na4(H2O)8][LaP2W12Nb6O61(H2O)7]4}·60H2O (1-La), K4Na8H4{[Nb4O6(H2O)4Na4(H2O)8][CeP2W12Nb6O61(H2O)7]4}·58H2O (1-Ce), K4Na8H4{[Nb4O6(H2O)4Na4(H2O)8][PrP2W12Nb6O61(H2O)7]4}·78H2O (1-Pr), K4Na8H4{[Nb4O6(H2O)4Na4(H2O)8][NdP2W12Nb6O61(H2O)7]4}·66H2O (1-Nd), have been synthesized using dimeric Dawson-type POMs, [H6P2W12Nb4O59(NbO2)2]28− and lanthanide salts as starting materials in acidic solution. The single crystal X-ray diffraction analysis indicates that the Dawson-type subunit {P2W12Nb6} is connected by terminal oxygen atoms of Nb at equatorial sites to form the dimeric unit. Two dimeric units are further linked by {Nb4O6} clusters to form tetrameric polyanions. The lanthanide ions are coordinated by the terminal oxygen atoms of Nb at polar sites in Dawson-type subunits. These compounds were further characterized by Fourier transform IR (FT-IR), thermogravimetry (TG), and cyclic voltammetry (CV) and exhibited electrochemical catalytic activity towards reduction of bromate ions.

A series of graphitic carbon nitride supported vanadium catalysts ( x V/g-C 3 N 4 ) with different vanadium contents ( x /%) were prepared by impregnation. XRD, FT-IR, TEM, TG-DTG, nitrogen adsorption and XPS characterizations were conducted which revealed a strong interaction between the vanadium species and g-C 3 N 4 support. 8V/g-C 3 N 4 exhibited the highest activity and showed stable recyclability in the benzene hydroxylation reaction with a benzene conversion of 24.6% and phenol selectivity of 99.2% under the optimized conditions. The excellent catalytic performance of x V/g-C 3 N 4 was due to the integration of vanadium species with high catalytic activity and the g-C 3 N 4 support in their interaction with the benzene substrate

A series of metal oxide (V, Fe, Cu) supported graphene oxide (M/GO) catalysts have been prepared by the impregnation method. The catalysts were characterized by TEM, XRD, FT-IR, and Raman spectroscopies and the results showed that the metal oxide nanoparticles were highly dispersed and successfully incorporated on graphene oxide sheets. Among the catalysts, V/GO exhibited the highest efficiency in direct hydroxylation of benzene using H2O2 as an oxidant in acetic acid solvent with a phenol yield of 22.7% and a selectivity of 98.4% under the optimized condition along with good recycle performance.

Organic–inorganic hybrid polyoxometalate (POM) compounds are a subset of materials with unique structures and physical/chemical properties. The combination of metal-organic coordination complexes with classical POMs not only provides a powerful way to gain multifarious new compounds but also affords a new method to modify and functionalize POMs. In parallel with the many reports on the synthesis and structure of new hybrid POM compounds, the application of these compounds for heterogeneous catalysis has also attracted considerable attention. The hybrid POM compounds show noteworthy catalytic performance in acid, oxidation, and even in asymmetric catalytic reactions. This review summarizes the design and synthesis of organic–inorganic hybrid POM compounds and particularly highlights their recent progress in heterogeneous catalysis.

Single-crystalline palladium arrow-headed tripods exhibiting high electro-activity in formic acid oxidation were prepared via a simple one-pot strategy by manipulating the reduction kinetics, concentration gradient and surface diffusion of atoms.

A series of nickel-containing mesoporous silica samples (Ni-SiO2) with different nickel content (3.1%–13.2%) were synthesized by the evaporation-induced self-assembly method. Their catalytic activity was tested in carbon dioxide reforming of methane. The characterization results revealed that the catalysts, e.g., 6.7%Ni-SiO2, with highly dispersed small nickel particles, exhibited excellent catalytic activity and long-term stability. The metallic nickel particle size was significantly affected by the metal anchoring effect between metallic nickel particles and unreduced nickel ions in the silica matrix. A strong anchoring effect was suggested to account for the remaining of small Ni particle size and the improved catalytic performance.

The confinement effect on enantioselective hydrogenation of acetophenone and its derivatives over free-standing mesoporous Pd network catalysts was systematically studied. It was found for the first time that the enantiomeric excess (ee) could be effectively tuned by altering the confinement effect optimized by precise control of the topology, pore size, and lattice structure of mesoporous Pd catalysts. The double gyroid structure with proper pore size and desired lattice structure formed by KBH4 reduction provided suitable microenvironment to generate optimized confinement effect. The optimized catalyst exhibited ee of 40-73% at 273 K under atmospheric pressure of H2. DFT study revealed that the major enantiomeric product could be predicted by comparing relative energies of prochiral-R and -S complexes formed by acetophenone derivatives with S-proline. The energetically favored complex led to the formation of the corresponding enantiomer in excess upon hydrogenation, and ee was found to be linearly correlated with the energy difference between prochiral-R and -S complexes. © 2014 Elsevier Inc. All rights reserved.

A novel organic–inorganic hybrid compound H 2 [Cu 2 (bpy) 2 (H 2 O) 2 (μ-ox)] 2 [H 2 W 12 O 40 ]·9H 2 O ( 1 ) (2,2 ′ -bipyrine and ox = oxalate) has been successfully synthesized under open-air mild reaction condition and characterized by elemental analysis, IR spectrum, thermal stability analysis, single-crystal X-ray diffraction and magnetic susceptibility measurement. The main structural feature of compound 1 is the presence of α-metatungstate cluster [H 2 W 12 O 40 ] 6− as inorganic building blocks, on which the bridged-oxalate dinuclear copper metalorganic units are supported. Magnetic susceptibility studies reveal that the compound 1 shows paramagnetic property with a magnetic moment about the Cu 2+ ion, indicating antiferromagnetic coupling between the neighboring Cu 2+ ions in the structure. The compound 1 also displays a good catalytic activity with the conversion 42.4% for H 2 O 2 decomposition.

Mesoporous silica molecular sieves are a kind of unique catalyst support due to their large pore size and high surface area. Several methods have been developed to immobilize heteropolyacids (HPAs) inside the channels of these mesoporous silicas. The mesoporous silica-supported HPA materials have been widely used as recyclable catalysts in heterogeneous systems. They have shown high catalytic activities and shape selectivities in some reactions, compared to the parent HPAs in homogeneous systems. This review summarizes recent progress in the field of mesoporous silica-supported HPAs applied in the heterogeneous catalysis area and preparation of nanostructured metal oxides using HPAs as precursors and mesoporous silicas as hard templates.

A series of remarkable crystalline compounds [Cu(2)(BTC)(4/3)(H(2)O)(2)](6)[H(n)XM(12)O(40)].(C(4)H(12)N)(2) (X = Si, Ge, P, As; M = W, Mo) were obtained from the simple one-step hydrothermal reaction of copper nitrate, benzentricaboxylate (BTC), and different Keggin polyoxometalates (POMs). In these compounds, the catalytically active Keggin polyanions were alternately arrayed as noncoordinating guests in the cuboctahedral cages of a Cu-BTC-based metal-organic framework (MOF) host matrix. X-ray crystallographic analyses, TG, FT-IR, UV-vis, N(2) adsorption studies, and acid-base titration demonstrated their high stability and toleration for thermal and acid-base conditions. No POM leaching or framework decomposition was observed in our study. The representative acid catalytic performance of a compound containing PW(12) species was assessed through the hydrolysis of esters in excess water, which showed high catalytic activity and can be used repeatedly without activity loss. Moreover, catalytic selectivity, which is dependent on the molecular size of substrates, and substrate accessibility for the pore surface were observed. It is the first time that the well-defined, crystalline, MOF-supported POM compound has behaved as a true heterogeneous acid catalyst. The unique attributes of MOF and well-dispersed level of POMs prohibited the conglomeration and deactivation of POMs, which allowed for the enhancement of their catalytic properties.

Sulfated titania solid superacids with dominant {001}, {001}/{101}, and {101} facets were prepared by the hydrothermal method and subsequent sulfation. Their facet-dependent acidic properties were investigated by the solid-state (31)P NMR technique and Pechmann condensation of 5,7-dihydroxy-4-methyl coumarin.

Four compounds based on polyoxometalates, [Cu(4-bpo)(H2O)][Cu2(μ2-Cl)(4-bpo)2(H2O)][SiW12O40][N(CH3)4]2·H2O (1), [Cu(4-bpo)]4[P2W18O62][N(CH3)4]2·6H2O (2), [Cu2(μ2-OH)(4-bpo)2(Hina)(H2O)2]2[P2W18O62]·4H2O (3), and [Cu2(Hina)4(H2O)2][H2P2W18O62](Hina)·11H2O (4) (4-bpo=2,5-bis(4-pyridyl)-1,3,4-oxadiazole, ina=isonicotinic acid), have been hydrothermally synthesized and characterized by elemental analysis, IR, and single-crystal X-ray diffraction. The 3-D framework of 1 is composed by Keggin-type polyoxoanions {SiW12} and two types of infinite chains, {Cu(4-bpo)(H2O)}n and {Cu2(μ2-Cl)(4-bpo)2(H2O)}n, through hydrogen bonds. Compound 2 has a 3-D rigid framework which is fabricated by Wells–Dawson type polyoxoanions {P2W18} and Cu-(4-bpo) chains through covalent bonds. Compound 3 contains an infinite {Cu2(μ2-OH)(4-bpo)2(Hina)(H2O)2}n double-chain and {P2W18} polyoxoanions immobilized in the voids between the chains. Compound 4 exhibits a 3-D supramolecular network directed by hydrogen bonds between {P2W18} polyoxoanions and the double paddle-wheel {Cu2(Hina)4(H2O)2}. Compounds 1–4 were tested as heterogeneous catalysts for the epoxidation of styrene using tert-butyl hydroperoxide (TBHP) as oxidant. The compounds show catalytic activity with 2 giving the highest yield of styrene oxide.

In situ NMR studies of C(1)-C(5) light alkane activation and functionalisation in heterogeneous catalytic systems are overviewed. The results obtained from the NMR technique, particularly those quantitative ones, provide unique information on the activation of alkane molecules and the nature of relevant intermediates, leading to better understanding reaction mechanisms and designing catalysts.

Aluminum doped cesium salts of tungstophosphoric acid, AlxCs2.5–3xH0.5PW12O40 (x = 0.05, 0.1 and 0.15), were prepared via a solid state synthesis method and their catalytic activity in n-butane isomerization reaction was tested using the 13C MAS NMR technique and 1-13C-n-butane as the reactant. All AlxCs2.5–3xH0.5PW12O40 catalysts show higher catalytic activity than Cs2.5H0.5PW12O40. Among them, Al0.1Cs2.2H0.5PW12O40 exhibits the best performance. The MAS NMR technique was further employed to characterize the acidity of the catalysts using trimethylphosphine and 2-13C-acetone as the basic probe molecules. Al0.1Cs2.2H0.5PW12O40 possesses higher Bronsted acid strength than Cs2.5H0.5PW12O40, which parallels the activity of the catalysts. For a catalyst used in n-butane isomerization reaction, to enhance its Bronsted acid strength rather than to increase its acid density is more important for improving the activity of the catalyst.

Three polyoxometalates (POM)-based coordination polymers, [CuII2(C5H5NCOO)2(4-bpo)2(H2O)2]SiW12O40·H2O (1), [CuI4(4-bpo)6]SiW12O40·3H2O (2), and [CuI4(3-bpo)4]SiW12O40·3H2O (3), were hydrothermally synthesized from the mixture of H4SiW12O40, copper salts, and 3-bpo (2,5-bis(3-pyridyl)-1,3,4-oxadiazole) or 4-bpo (2,5-bis(4-pyridyl)-1,3,4-oxadiazole) and characterized by elemental analysis, IR spectroscopy, TG analysis, and single crystal X-ray diffraction. The 4-bpo molecules are connected into an infinite double-chain in compound 1 as a bidentate ligand. Compound 2 contains large hexagonal prism shaped molecular cages defined by copper ions and 4-bpo molecules which wrap Keggin ions inside. In compound 3 {Cu2(3-bpo)2} molecular rings connect with Keggin ions to form a 1D chain. By inspection of the structures, the geometry and the coordination mode of bpo ligands play important roles in the formation of 1–3. The catalytic performance of 1–3 was investigated for epoxidation of styrene using tert-butyl hydroperoxide (TBHP) as the oxidant. Compounds 1–3 present promising activity as heterogeneous catalysts while compound 1 exhibits the best yield of styrene epoxide.