Xiaoyuan Yang

Different transition metal (Fe2+, Co2+, Ni2+, Cu2+ or VO2+) Schiff complexes immobilized onto three-dimensional mesoporous silica KIT-6 for the epoxidation of styrene

Highly ordered three-dimensional Ia3d mesoporous silica KIT-6 was functionalized with 3-aminopropyltriethoxysilane (3-APTES), following by post-grafting of various transition metal (Fe2+, Co2+, Ni2+, Cu2+ or VO2+) Schiff complexes onto amino-functionalized KIT-6. The surface functionalized materials were analyzed by a series of characterization techniques such as XRD, X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption, IR spectroscopy, inductively coupled plasma (ICP), scanning electron microscopy (SEM), and thermal gravimetric analyses (TGA), etc. The characterization results demonstrated structural intact of the mesoporous hosts throughout the grafting procedures and successfully anchoring of transition metal Schiff complexes on the modified KIT-6. The obtained organic–inorganic hybrid materials were subsequently employed as catalysts for the epoxidation of styrene under optimized reaction conditions. It was indicated that Cu-NH2-KIT-6 showed very high substrate conversion (98.6%) and excellent epoxide selectivity (97.8%) when using tert-butyl hydroperoxide (TBHP) as the oxidant at 80 °C after 6 h. It was also observed that the catalyst could be recycled three times without obvious loss in catalytic activity and selectivity.

Highly dispersed cobalt oxide nanoparticles on CMK-3 for selective oxidation of benzyl alcohol

Nano cobalt oxide particles supported on ordered mesoporous carbon CMK-3 (CMK: carbon material from Korea) were prepared by a hydrothermal synthesis method. The catalysts were characterized by various characterization methods such as XRD, FT-IR, TEM, FESEM, N2 adsorption and desorption, XPS, Raman and ICP-AES, which indicated that the size of the cobalt oxide nanoparticles was estimated to be ∼2 nm and that they were uniformly dispersed on CMK-3. The approach obtained smaller and narrow distributed cobalt oxide nanoparticles which was the key to complete the reaction with 82.1% conversion and 97.7% benzaldehyde selectivity within 6 h. The average TOF of Co3O4/CMK-3 can reach as high as 25.4 h−1 in the initial two hours, which was far higher than that of the unsupported nano Co3O4 (less than 1.0 h−1) and so far reported cobalt-based catalysts (e.g. 1.34 h−1 for Co3O4/RGON). In addition, the catalytic activity of Co3O4/CMK-3 was not obviously deteriorated after 4 runs.

Application of metal organic frameworks M(bdc)(ted)0.5 (M = Co, Zn, Ni, Cu) in the oxidation of benzyl alcohol

The selective oxidation of benzyl alcohol to benzaldehyde is an important process in heterogeneous catalysis and green organic chemistry. Herein, we investigated the effect of different metal ions in the metal organic framework M(bdc)(ted)0.5 (M = Co, Zn, Ni, Cu, bdc = 1,4-benzenedicarboxylate, ted = triethylenediamine) on the catalytic activity of benzyl alcohol oxidation. The catalytic results demonstrated that Co(bdc)(ted)0.5 achieved good benzyl alcohol conversion (81.8%) and benzaldehyde selectivity (>99%) by using O2 as the oxidant. The catalysts could be reused several times without significant degradation in activity.

Effect of the particle size of MoO3 on the catalytic activity of Mo/ZSM-5 in methane non-oxidative aromatization

Three types of molybdenum oxide with different sizes (i.e. 10–20 μm, 0.1–1 μm and 30–150 nm) were used to modify ZSM-5, which were investigated in the methane non-oxidative aromatization reaction. The structure and surface properties of the prepared catalysts were studied using XRD, SEM, N2 adsorption/desorption, ICP-AES, NH3-TPD and the IR spectra of pyridine adsorption. The characterization results showed that MoO3 with smaller size calcined at 500 °C more easily sublimated to form Mo-species at a atomic/molecular level, diffused into the channels of ZSM-5 and reacted with the Bronsted acid to form Mo–O–Al species, which resulted in the decrease of the Bronsted acid sites in the catalysts. The catalytic results confirmed that nano MoO3 modified ZSM-5 zeolites calcined at 500 °C showed higher methane conversion (14.1%) and aromatics yield (9.5%) than micron MoO3 modified ZSM-5. In addition, micron MoO3 modified ZSM-5 calcined under higher temperature (i.e. 550 °C) or calcined at 500 °C for longer time did not achieve the higher catalytic behaviour. Moreover, nano-MoO3 modified ZSM-5 showed better catalytic stability when compared with micron-MoO3 modified ZSM-5.

Oxidation of benzyl alcohol over metal organic frameworks M-BTC (M = Co, Cu, Fe)

A series of metal organic frameworks (MOFs) with cobalt, copper and iron as central metal atoms and 1,3,5-benzenetricarboxylic acid as a ligand were synthesized (denoted M-BTC) for selective oxidation of benzyl alcohols. High conversion (92.9%) and good selectivity (97.1%) were achieved over Co-BTC with air as the oxidant.

Highly efficient Ni–Co oxide nanoparticles on nitrogen-doped FDU-15 for aerobic benzyl alcohol oxidation

Ni–Co bimetallic oxide catalysts with various loadings and Ni/Co ratios supported on N-doped FDU-15 were prepared by a facile and controllable one-pot method and tested as heterogeneous catalysts for the oxidation of benzyl alcohol. The prepared materials were characterized by a series of characterization techniques such as XRD, TEM, SEM-EDX, FT-IR, XPS, N2 adsorption–desorption, Raman and ICP-AES. Catalytic results showed that 2 wt% Ni–Co3/FDU-15-N possessed very high substrate conversion (93.4%) and excellent benzaldehyde selectivity (97.8%) when using air as the oxidant at 110 °C. This superior catalytic performance over bimetallic catalysts indicated a synergy effect between Ni and Co. The improved redox ability and dispersion of Ni–Co alloying sites also contributed to this enhancement. Additionally, N-doped Ni–Co3/FDU-15-N might strengthen the interaction between NiO, Co3O4 and the support and thus improve the dispersion of the metal oxides.

Anchoring Tri(8-Quinolinolato)Iron Onto Sba-15 for Partial Oxidation of Benzyl Alcohol Using Water as the Solvent

Abstract Tri(8-quinolinolato)iron complex immobilized onto SBA-15 catalyst has been synthesized through a stepwise procedure. The characterization results indicated that the BET surface area, total pore volume and average pore width decrease after stepwise modification of SBA-15, while the structure keeps intact. Catalytic tests showed that FeQ3-SBA-15 catalyzes the oxidation reaction well with 34.8% conversion of benzyl alcohol and 74.7% selectivity to benzaldehyde when water is used as the solvent after 1 h reaction. In addition, homogeneous catalyst tri(8-quinolinolato)iron exhibits very bad catalytic behavior using water as the solvent.

Effect of Different Silicate Supports on the Catalytic Performance of MoVTeO Mixed Oxides in Partial Oxidation of Isobutane

Abstract A series of 5% MoV0.3Te0.25 supported on different silicates (i.e. SiO2, HMS, MCM-41, and MCM-48) have been prepared, characterized, and tested as catalysts in the partial oxidation of isobutane to methacrolein. Characterization results showed that the supports almost kept intact structures after supporting 5 wt.% MoV0.3Te0.25 and the supported catalysts had large specific surface areas. Catalytic tests showed that the specific surface area played a key role in the catalytic activity for the supported catalysts.