Search

Ru/SBA-15 showed excellent activity for phenol to cyclohexanol at 20 °C and exhibited a zero-order character with low Ea of 10.88 kJ mol−1. A high yield of 37.4% of cyclohexanol was obtained at 80 °C and 4 h when using eugenol as substrate.

An asymmetric retro-[1,4]-Brook rearrangement of 3-silyl allyloxysilanes has been developed

Two different methods of introducing potassium into Cu/TS-1 were conducted and the catalysts obtained showed a rather different catalytic activity in the ammoxidation of benzene to aniline. K could enter the Cu/TS-1 catalyst under reaction conditions, and the resultant catalyst exhibited acceptable selectivity of 99.5% to aniline. However, the catalyst with potassium introduced by wet impregnation exhibited undesirable selectivity (

Herein, metal–ligand bonding features in a chelation N,N′-dioxide–Sc(III) complex have been addressed using the DFT method at the M06/6-31+G** Level. The donor–acceptor interaction between the carbonyl substrate and Sc(III)-based catalyst is analyzed in detail by the activation strain model (ASM), energy decomposition analysis (EDA), and natural orbital for chemical valence (NOCV) calculations. The orbital interaction is the major contributor to N,N′-dioxide–[Sc(OTf)]2+ bonding, whereas the electrostatic interaction plays a more important role than orbital interaction in the activation of a carbonyl compound in hexacoordinate N,N′-dioxide–Sc(III) complexes. The substituents in the amide group of the N,N′-dioxide ligand (L) affect the electrostatic energy as well as the orbital energy between the CH2O and Sc(III)-based catalyst by adjusting the Lewis acidity of the metal centre. The complex with ortho-diisopropylphenyl groups in the ligand exhibits a higher reactivity towards CH2O. Compared to OiPr, the counter ion OTf in the Sc(III)-complex enhances the Lewis acidity of the metal centre and facilitates the activation of CH2O by promoting electron density flow from CH2O to the metal fragment. The high catalytic performance of the N,N′-dioxide–Sc(III) complex towards PhCHO and chalcone is attributed to their good nucleophilicity that results in a more stabilizing electrostatic and orbital interaction between the N,N′-dioxide–[Sc(OTf)]2+ complex and carbonyl substrate.

A series of VOx/HZSM-22 catalysts for the partial oxidation of ethylbenzene was prepared with 0.09–2.86 wt% V loading by an incipient wetness impregnation method, and the catalysts were characterized by inductively coupled plasma-atomic emission spectrometer, X-ray diffraction, Fourier transform infrared spectroscopy, N2 physisorption analysis, X-ray photoelectron spectroscopy, diffuse reflectance ultraviolet-visible spectroscopy, temperature-programmed calcination-mass spectroscopy, and temperature-programmed hydrogen reduction. The results showed that the chemical nature of vanadium species on HZSM-22 depended on V loading. The amount of vanadium species incorporated into the framework of HZSM-22 increased with V loading firstly and reached a relatively stable value of about 0.2 wt%. The decomposed ammonia might reduce V5+ to V4+ in the calcination process. Highly dispersed extra-framework vanadium species, especially surface extra-framework V4+, promised a good effect on the oxidation of ethylbenzene, under optimized conditions, a high yield of 17.5% with 72.5% selectivity to acetophenone was obtained.

The preparation of activated carbon from rice husk residue using H3PO4 as activation agent was studied. The samples were characterized by elemental analysis, N2 adsorption–desorption, scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), temperature programmed decomposition-mass spectra (TPD-MS), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The role of H3PO4 in the activation process was discussed. A maximum surface area of 1016 m2 g−1 was obtained under the optimized conditions, that is, a base treated solid material to H3PO4 mass ratio of 1:2, an activation temperature of 500 °C and an activation time of 1 h. H3PO4 might act as a catalyst which facilitates the release of CO2, an oxidant which reacts with carbon after dehydration, and a reagent which enters AC through C–O–P bonds.

A Zr and Mn co-promoted Ni-based catalyst was prepared using an impregnation method and employed for the dry reforming of methane. Characterization of the catalysts has been performed using XRD, TEM Mapping, XPS, TPR, TPO, TG, TPH and Raman techniques. The results showed that the addition sequence of the Mn and Zr promoters contributed substantially to the structure and activity of the catalyst. A high dispersion of the Ni, Mn and Zr species and strong interactions of the metallic oxides with the support were observed on ZrOx/Ni–MnOx/SiO2 catalysts, which enhanced the formation of polymeric carbon species capable of being gasified by CO2 to release CO and H2. Under these conditions the ZrOx/Ni–MnOx/SiO2 catalyst exhibited high initial activity and excellent stability.

Rice husk pyrolytic carbon (PC) was pretreated by NaOH solution at 100 °C for 5 h to remove SiO2 and then used to prepare Fe/activated carbon catalyst. The treated sample was impregnated with ferric nitrate solution, and then activated under N2 atmosphere, obtaining Fe/activated carbon catalysts. The samples were characterized by temperature programed decomposition-mass spectra (TPD-MS), Brauner–Emmett–Teller (BET), inductively coupled plasma atomic emission spectrometry (ICP-AES), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The specific surface area increased with activation temperature until 750 °C. With the increase of iron content, the specific surface area of carbon increased first up to 0.39 mmol g−1 iron loaded and then decreased. Reactive decomposition of ferric nitrate happened at 120–350 °C releasing NO and CO2. Part of ferric (Fe(III)) species was reduced to ferrous (Fe(II)) species forming Fe3O4 at 400–550 °C, and metal Fe at 650–750 °C. The Fe/activated carbon exhibited high activity and selectivity for phenol hydroxylation.

The activation mechanism of C2H6 on a Pt4 cluster has been theoretically investigated in the ground state and the first excited state potential energy surfaces at the BPW91/Lanl2tz, aug-cc-pvtz//BPW91/Lanl2tz, 6-311++G(d, p) level. On the Pt4 cluster, the optimal channel order was kinetically as follows: demethanation > dehydrogenation > deethylenation from C2H6. The two-fold dehydrogenation of ethane to acetylene was almost equivalent to its single dehydrogenation to ethylene, both thermodynamically and kinetically. In addition, the C–H cleavage intermediate was kinetically more preferable than the C–C cleavage intermediate, while both the C–H cleavage intermediate and the C–C cleavage intermediate were thermodynamically favoured. Nevertheless, the extremely stable C–H cleavage intermediate was trapped in a deep well, which hindered the release of H2. Together with the excellent reactivity of the Pt4 cluster, for the design of an efficient and selective catalyst towards the dehydrogenation of C2H6, one can expect that it is necessary to improve the release of H2 from the C–H cleavage intermediate by introducing some additive or support into the Pt4 cluster, which decreases the binding of the catalyst towards H2. Concerning selectivity, the Pt atom was the most favourable for the dehydrogenation, the Pt2 cluster was the most preferable for deethylenation, and the Pt4 cluster was the most beneficial for the demethanation. Both Pt4 and Pt2 clusters exhibited more promising catalytic performance compared with the mononuclear Pt atom towards C2H6 activation.

The dehydrogenative cross-coupling between caffeine and 2-formylfuran has been theoretically studied using a DFT method. It is found that the coupling process consists of three steps: 2 consecutive C–H bond activations, and reductive elimination. The mechanism with pyridine added as a ligand is energetically more favored than that with the solvent molecule or the generated acetic acid as or without ligand. Two kinds of pathways involving the prior activation of one of the coupling partners have been performed, and the prior activation of caffeine by the Pd(OAc)2 catalyst, followed by the activation of 2-formylfuran is energetically preferred. The calculated results indicated that the activation of 2-formylfuran is the rate-determining step with an energy barrier of 75.3 kJ mol−1. The interaction of the first activated partner with the catalyst assists the activation of the second partner, and the C–H activation of caffeine is easier than that of 2-formylfuran as the energy barrier is 22.3 kJ mol−1 lower. The above two parameters provide mainly the high selectivity to the cross-coupling product. The mechanism of the dehydrogenative cross-coupling of caffeine and 2-formylthiophen is similar to that described above.

Ethyl valerate (EV) as a promising fuel additive was produced by esterification of valeric acid with ethanol over Bronsted acidic amino acid ionic liquids. Hammett method and density functional theory (DFT) calculations were preformed to evaluate the acidities of the catalysts. The composition of catalyst, reaction temperature, reaction time, molar ratio of reactants, amount of catalyst, and recycling ability of the catalyst were investigated. Proline bisulfate (ProHSO4) ionic liquid has the highest catalytic activity and the best recyclability under the optimized esterification conditions. A high conversion of valeric acid (>99.9%) was obtained for 7 h at 80 °C, with 100% selectivity of EV. The density, viscosity, melting point, boiling point, elemental analysis and heat of combustion of the EV product were measured. The density of EV is 0.896 g cm−3. The viscosity of EV was 1.7 cP at room temperature. The heating values of EV are 4158.1 kJ mol−1 and 31.9 kJ g−1. EV obtained from esterification has higher energy density than methanol, ethanol, γ-valerolactone, and valeric acid, which illustrates that EV is a promising biofuel candidate.

A modified hydrothermal method was used to synthesize Cu doped TS-1 zeolite (Cu-TS-1) from TEOS, TBOT and Cu(CH3COO)2 with TPAOH as the template. The impregnation of TS-1 with aqueous solution of Cu(NO3)2 was also carried out to introduce Cu species onto TS-1 to obtain Cu/TS-1 catalyst. The TS-1, Cu/TS-1 and Cu-TS-1 samples were characterized by XRD, XPS, SEM, UV-VIS, FT-IR, Raman and NH3-TPD-MS to reveal the effect of the preparation procedure and Cu contents on the properties of Cu-TS-1 zeolite samples. Cu species doped via the modified hydrothermal method made the crystal shape of the samples change from round to polygon, however, the crystal shape was almost unchanged when Cu species was doped via wet impregnation. A proper amount of Cu species in the Cu-TS-1 zeolite could promote the crystallization of MFI structure and limit the formation of extra-framework TiO2. The Cu-TS-1 zeolite was employed as a catalyst in the nitration of benzene with ammonium acetate as the nitrating agent and hydrogen peroxide as the oxidizing agent under mild conditions. The synergetic effect of doped Cu and TS-1 zeolite with MFI structure restrained the hydroxylation reaction, and increased the yield and selectivity to nitrobenzene. 47.8 μmol (about 0.4%) yield and 57.0% selectivity to nitrobenzene with a ITOF = 9.6 h−1 and a IITOF = 38.3 h−1 were obtained on Cu-TS-1 (1.76 wt% Cu content) catalyst under optimized reaction conditions.

A large abundance of environmentally harmful biomass waste is generated by water blooms. In order to provide an applicable solution for the relief of the environmental pressure, natural algae of Taihu Lake water blooms (CTL), mainly cyanobacteria, were catalytically pyrolyzed over silica-supported nickel phosphide to produce bio-oil. The properties of the bio-oil, such as chemical composition, elemental composition, and higher heating value (HHV), were examined. The composition of the gas product was also detected. The results suggest that catalytic pyrolysis could effectively convert the algae to a high quality bio-oil, in which the oxygen content was considerably reduced from 41.7 wt% in the algae to 8.0 wt% in the bio-oil. Long-chained alkanes became the primary component (59.4%). The HHV of the bio-oil obtained from catalytic pyrolysis was 37.2 MJ kg−1. The results indicate that it is possible to achieve high-grade renewable transportation fuels via catalytic pyrolysis of environmentally harmful CTL, and nickel phosphide is an applicable and effective catalyst.

The mechanism by which benzene is converted to phenol through hydroxylation, catalyzed by vanadium in CH3CN is explored at the B3LYP(IEF-PCM)//B3LYP/6-311G(2d,2p) level. Three candidate catalysts are used to simulate the catalytic cycle. The solvent effectively reduces the free energy barriers of the C–H bond activation step. The binuclear vanadium species is predicted to be the main form of the operative catalyst. The cooperative role of the two vanadium centres and the dynamic charge distribution of the binuclear vanadium species are found to increase the catalytic activity. The conservation of aromaticity for the phenyl ring in the benzene or phenyl ligand is essential for the benzene hydroxylation.