Yuanhang Ren

Progress of the Application of Mesoporous Silica-Supported Heteropolyacids in Heterogeneous Catalysis and Preparation of Nanostructured Metal Oxides

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.

Heterogeneous Catalysis of Polyoxometalate Based Organic–Inorganic Hybrids

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.

Highly Dispersed Nickel-Containing Mesoporous Silica with Superior Stability in Carbon Dioxide Reforming of Methane: The Effect of Anchoring

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.

Three POM-based coordination polymers: hydrothermal synthesis, characterization, and catalytic activity in epoxidation of styrene

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.

Recent development in in situ NMR study on heterogeneous catalysis: mechanisms of light alkane functionalisation

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.

Vanadium supported on graphitic carbon nitride as a heterogeneous catalyst for the direct oxidation of benzene to phenol

Abstract 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

Four organic–inorganic compounds based on polyoxometalates: crystal structures and catalytic epoxidation of styrene

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. Four organic–inorganic hybrid compounds were hydrothermally synthesized based on polyoxometalates, copper salts, and 2,5-bis(4-pyridyl)-1,3,4-oxadiazole or isonicotinic acid ligands. Among those four compounds, compound 2, [Cu(4-bpo)]4[P2W18O62][N(CH3)4]2·6H2O, showed the best catalytic activity for heterogeneous epoxidation of styrene to styrene oxide using tert-butyl hydroperoxide as oxidant.

Preparation and Photocatalytic Activity of Lanthanide Loaded Microporous Titanosilicate ETS-10 Catalysts

The three dimensional microporous titanosilicate, ETS-10, was synthesized by a hydrothermal synthesis route using TiCl4 and a sodium silicate aqueous solution as starting materials. Lanthanide (La, Ce, Pr, Nd) loaded ETS-10 catalysts were prepared by the impregnation method. The catalysts were characterized by X-ray diffraction, 29Si magic angle spinning NMR, UV-Vis diffuse reflectance spectroscopy, N2 adsorption-desorption measurement, and X-Ray fluorescence spectroscopy. The degradation of methyl orange under near-UV light was used to investigate the photocatalytic activity of the catalysts in aqueous suspensions. The lanthanide loaded ETS-10 catalysts exhibit higher activity than the unmodified ETS-10. The combination of loading lanthanide and increasing the surface defects of ETS-10 by a HF treatment gave an enhancement of the photocatalytic activity, which became comparable with that of anatase TiO2.

Honeycomb nanoscale-porous material constructed from copper complexes and mixed-addenda Lindqvist-type polyoxoanions

A honeycomb nanoscale-porous material constructed from straight metal–organic chains and octahedral Lindqvist-type polyoxoanion building blocks is solvothermally synthesized, exhibiting a hexagonal array of one-dimensional pores similar with that of MCM-41. The pore sizes are in the range of 16.33 to 23.71 A and the sorption property of the material is investigated.

尖晶石型衍生的Ni/Al 2 O 3 催化剂低温催化顺酐加氢合成丁二酸酐

ABSTRACT 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 .