Haiqing Wang

Spherical V-MCM-48: the synthesis, characterization and catalytic performance in styrene oxidation

A series of spherical, vanadium-containing, mesoporous V-MCM-48 catalysts with different V/Si atomic ratios were synthesized by a direct hydrothermal method. The structure and morphology of the samples and the states of vanadium in the materials were systematically characterized by XRD, N2 physisorption, FE-SEM, HRTEM, ICP, UV-vis, 51V MAS-NMR, ESR and XPS. The possible formation mechanism of spherical V-MCM-48 was proposed based on the Stober process. Simultaneously, the catalytic activities of the samples were evaluated in the oxidation of styrene to benzaldehyde using H2O2 as oxidant. The results show that the V-MCM-48 samples have regular spherical morphology, homogeneous dispersion and highly ordered cubic mesostructure. Characterization results about the coordination states of vanadium species demonstrated that most of vanadium existed as tetracoordinated V4+ species in a silicate framework and a small amount of vanadium as isolated V5+ species on the surface. The prepared spherical V-MCM-48 exhibits much higher catalytic activity in the catalytic conversion of styrene to benzaldehyde. Spherical morphology contributes significantly to the improved catalytic performance of materials. V5+ species on the surface and/or produced from the oxidation of some V4+ in the framework act as active sites. Furthermore, the reaction parameters such as vanadium content in V-MCM-48, molar ratio of H2O2/styrene, temperature, time and solvents were optimized.

Coordination of manganese porphyrins on amino-functionalized MCM-41 for heterogeneous catalysis of naphthalene hydroxylation

Abstract The different amounts of [5,10,15,20-tetrakis-(pentafluorophenyl)porphyrin] manganese chloride (TF 20 PPMnCl) were immobilized on amino-functionalized MCM-41 for catalysis of the hydroxylation of naphthalene. The samples were characterized by X-ray powder diffraction, N 2 adsorption/desorption isotherms, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, diffuse reflectance ultraviolet-visible spectroscopy, thermogravimetric and differential scanning calorimetry, and inductively coupled plasma mass spectrometry. The results indicated that the manganese porphyrins were axially coordinated on amino-functionalized MCM-41. The prepared samples showed remarkable catalytic activity in the hydroxylation of naphthalene with meta -chloroperbenzoic acid as the oxidant. The catalyst could be reused several times without loss of its activity.

One-Pot Synthesis of Iron-Containing Nanoreactors with Controllable Catalytic Activity Based on Multichannel Mesoporous Silica

We have constructed Fe‐substituted silicate nanotube reactors (Fe–NTRs) through a newly developed one‐step solubilization (OSS) method in which cetyltrimethylammonium bromide and P123 are used as structure‐directing and shape‐controlling agents, respectively, and ferrocene is utilized as iron source by solubilizing inside the hydrophobic inner core of the surfactant micelles. The Fe–NTRs showed regular morphology, highly ordered multichannel mesopores, controllable sizes with lengths changing from 150 nm to 1.2 μm, diameters of approximately 130 nm and pore sizes of approximately 2.7 nm, and iron contents in a range from 0.66 to 1.59 wt %. The OSS strategy is also applicable for other metal‐functioned silicate nanoreactors. The catalytic activity of Fe–NTRs in the direct hydroxylation of phenol can be essentially manipulated by the controllable sizes. The release behavior of reactants reveals that the diffusion control derived from the lengths of Fe–NTR should be responsible for the resultant reactivity.

Spherical V-Fe-MCM-48: The Synthesis, Characterization and Hydrothermal Stability

Spherical MCM-48 mesoporous sieve co-doped with vanadium and iron was successfully synthesized via one-step hydrothermal method. The material was characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption isotherms, inductively coupled plasma (ICP), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance UV-vis spectra, and X-ray photoelectron spectra (XPS) techniques. Results indicated that the V-Fe-MCM-48 showed an ordered 3D cubic mesostructure with spherical morphology, narrow pore size distribution and high specific surface area. Most of vanadium and iron atoms existing as tetrahedral V4+ and Fe3+ species were co-doped into the silicate framework. The particle sizes of V-Fe-MCM-48 were smaller and the specific area was much higher than those of of V-MCM-48. Additionally, the synthesized V-Fe-MCM-48 exhibited improved hydrothermal stability compared with the pure MCM-48.