Xiuling Wu

A novel solid acid catalyst synthesized from ZnAl2O4 spinel and its application in the esterification of acetic acid and n-butyl alcohol

A new spinel-style S2O82−/ZnAl2O4 solid acid catalyst was prepared by sol–gel method. The catalytic performance was evaluated by the esterification of n-butyl acetate. The structure, morphology and acidity of the samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FE-SEM), N2 physisorption, X-ray photoelectron spectroscopy (XPS) and NH3 temperature programmed desorption (NH3-TPD). The results showed that the catalytic performances were significantly affected by the calcination temperature. S2O82−/ZnAl2O4-600 exhibited the highest catalytic activity of 91.7% under the optimum reaction conditions. The characterization showed that the mesoporous structure S2O82−/ZnAl2O4-600 maintained the well crystallinity of spinel as well as the spinel-style carrier in the sulfidation and recycling.

Effects of citric acid and urea on the structural and morphological characteristics of BiVO4 synthesized by the sol–gel combustion method

Micro-sized spherical BiVO4 photocatalysts composed of nanoparticles were synthesized by the sol–gel combustion method. The effects of citric acid and urea on the structural and morphological characteristics of samples were studied by X-ray diffraction, field emission scanning electron microscopy, N2 adsorption and desorption and UV–Vis spectroscopy. The photocatalytic activity was evaluated by the photocatalytic degradation of rhodamine B under visible light. The results showed the sphere-shaped BiVO4 sample to have excellent photocatalytic performance compared with the bulk sample prepared by solid-state reaction. This enhancement could be attributed to the special spherical morphology, which enhanced the absorption ability, increased the separation efficiency of photon-generated carriers and improved surface reaction sites for consumption of photon-generated carriers.Graphical AbstractUniform micro-sized spherical BiVO4 samples composed of nanoparticles were successfully synthesized by the sol–gel combustion method. The relationships between the morphologies and citric acid with urea contents were studied by using the field emission scanning electron microscopy (FE-SEM) technology.FE-SEM images of the samples (A) the samples synthesized with different citric acid contents and (B) the samples synthesized with different urea contents

Polytypism and microstructures of the mixed-layer member B2S, CaCe3(CO3)4F3 in the bastnaesite-(Ce)–synchysite-(Ce) series

The crystal structures and polytypism of bastnaesite-(Ce) (CeCO3F, B layer) and synchysite-(Ce) (CeCO3F·CaCO3, S layer) mineral series are very complicated in Sichuan Province, Southwest China. Four new polytypes: 6R, 2H2, 4H and 12H of the mixed-layer member CaCe3(CO3)4F3 (B2S) of this series were discovered by X-ray diffraction analyses and high resolution transmission electron microscopy, structural symmetry, cell and subcell parameters, possible space group, and structural stacking mode (dededgfg/…). They reveal that the mixed-layer member B2S is formed by the ordered stacking of two structural unit layers of bastnaesite-(Ce) (B layer) and one unit layer of synchysite-(Ce) (S layer) along the c direction. The forming of the new polytypes may depend on distributions and the periodical variation of orientation of the [CO3] groups between the unit layers of B2S. We have observed the {000l} microtwin of the 6R polytype and the syntactic intergrowths among the different polytypes formed by stacking faults in B2S.

Enhanced visible light photocatalytic performances of self-assembled hierarchically structured BiVO4/Bi2WO6 heterojunction composites with different morphologies

Novel self-assembled hierarchical BiVO4/Bi2WO6 heterostructured composites with different morphologies were controllably synthesized via a facile and template-free solvothermal method. The effects of the molar ratio of V to W on the structure, morphology, photocatalytic activity and photoelectrochemical properties of the BiVO4/Bi2WO6 composite photocatalysts were investigated in detail. The results showed that all the BiVO4/Bi2WO6 composites exhibited much better photocatalytic activities for methylene blue (MB) degradation and photoelectrochemical performances than pure BiVO4 and Bi2WO6. Among the composites, the BiVO4/Bi2WO6 microsphere with the molar ratio of V to W of 2 : 1 exhibited the best photocatalytic performance. The mechanism of enhanced activity was systematically investigated by UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, and photo-electrochemical methods including transient photocurrent responses, electrochemical impedance spectroscopy (EIS) and Mott–Schottky plots. The enhanced photocatalytic activity could be ascribed to the tetragonal–monoclinic heterophase structure, high surface oxygen vacancy concentration, narrow band gap energy and mainly the formed heterojunction structure which could effectively promote the separation of photogenerated electron–hole pairs. In addition, a possible photocatalytic mechanism for the enhanced photocatalytic activity was proposed on the basis of the calculated energy band positions of BiVO4 and Bi2WO6.

Defect microstructures in garnet, omphacite and symplectite from UHP eclogites, eastern Dabieshan, China: aTEM and FTIR study

Abstract Garnets, omphacite and the minerals of a clinopyroxene/amphibole/plagioclase symplectite in UHP eclogites from Yingshan, Dabieshan have been investigated by TEM and Micro-FTIR. TEM reveals that the predominant microstructures in eclogites and symplectite-forming minerals are chain multiplicity faults (CMFs), dislocation substructures, clusters of water molecules up to ~50 nm in diameter and recrystallized grains -1.75 μm in diameter. This indicates dynamic recrystallization of omphacite, probably during an eclogite-facies metamorphic episode. The deformation structures in symplectite-forming minerals were produced by plastic deformation related to an amphibolite-facies retrograde metamorphic event. CMFs described in the present work demonstrate the existence of an infrequent ½<011> (010) slip system for Flln omphacite from an UHP eclogite sample from Dabieshan. The frequent occurrence of CMFs in omphacite suggests that they indicate an important deformation mechanism in omphacite and shows that this slip system plays a significant role in the deformation and recovery of eclogite. The hydrous components of deformed minerals may cause plastic deformation of the rocks by dislocation movement and accelerate retrograde metamorphism. Micro- FTIR results show that all the garnets and omphacites contain structural water occurring as hydroxyl groups (OH) or water (H2O). The structural water contents in omphacite range from 110-710 ppm and in garnet from 0-180 ppm. Water released during decompression might supply an early-stage retrograde metamorphic fluid.

Modification of kaolinite with alkylimidazolium salts

We have demonstrated that the d-spacing and thermal stability of the alkylimidazolium intercalated kaolinite compounds can be controlled by adjusting chain length of the alkyl groups. The composites were synthesized by displacement method using selected imidazolium ionic liquids bearing different short alkyl chains as guest molecules. The effects of the length of alkyl side chain on d-spacing and thermal stability of the ionic liquids–kaolinite intercalations were investigated by XRD and TG-DSC. Results revealed that in these composites, increasing the length of alkyl substituent led to larger d-spacing and decreased thermal stability. Temperature was found to have influence on the intercalation ratio but not on the d-spacing of final product. The present study shows an easy way of tailoring the performance of these intercalations via small variation of guest ionic liquids, providing the possibility of finding “species-specific” modifier for fully exfoliated nanocomposites.

STRUCTURAL CHARACTERIZATION OF A NEW DECAVANADATE COMPOUND WITH ORGANIC MOLECULES AND INORGANIC IONS

A new decavanadate compound V10O28[Co(H2O)6]3(C8H18O6N2S2)2 (I) is synthesized and characterized by single crystal X-ray diffraction, thermogravimetric analysis, FT-IR spectroscopy, and scanning electron microscopy. The sizes of the monoclinic unit cell are as follows: a = 13.2851(16) Å, b = 22.769(3) Å, c = 13.1883(16) Å, β= 117.555(2)°, V = 3536.7(7) Å3, C2/m space group, Z = 2. The studies revealed that different moieties in the compound show a three-dimensional framework structure, in which {CoO6}, the decavandate cluster anions, and 1,4-piperazinediethanesulfonic acid (PIPES) interact with each other by intermolecular forces and strong hydrogen bonding. Bond valence calculations were used to calculate the valence states of the atoms.

Synthesis, characterization and properties of Ce-modified S2O82−/ZnAl2O4 solid acid catalysts

A new spinel solid acid catalyst of S2O82−/ZnAl2O4-x wt% Ce was simply prepared by modifying S2O82−/ZnAl2O4 with Ce for acid catalysis of acetic acid and n-butanol. The prepared catalysts were characterized by means of XRD, IR, TG, XPS, NH3-TPD, SEM and N2-physisorption. The experimental results showed S2O82−/ZnAl2O4-x wt% Ce solid acid catalysts belonged to the spinel-type ZnAl2O4 structure. The addition of Ce played a key role in stabilizing the surface sulfur species and consequently increasing the acid strength of S2O82−/ZnAl2O4-x wt% Ce. The appropriate modification of Ce was 4 wt% and S2O82−/ZnAl2O4-4 wt% Ce catalyst had 95.9% esterification efficiency under the optimum reaction conditions. Compared with unmodified S2O82−/ZnAl2O4 catalyst, S2O82−/ZnAl2O4-4 wt% Ce solid acid catalyst showed much better reusability, which could remain above 80% esterification even after being used for six times. The loss of sulfur species on the surface of S2O82−/ZnAl2O4-4 wt% Ce solid acid was one of the essential reasons for its deactivation during the acid catalyzed reaction.

Hydrothermal synthesis, crystal structure, and thermal analysis of a Novel trinuclear manganese complex: Mn3(C12H8N2)2(C10H11O5)6

A novel trinuclear manganese(II) complex, Mn3(C12H8N2)2(C10H11O5)6 (I), has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction. The crystal belongs to the monoclinic system, space group P21/n, with cell parameters a = 12.1935(7), b = 19.0249(11), c = 18.0515(10)Å, β = 105.0430(10)°, V = 4044.1(4)Å3, Z = 2. Two of the three manganese atoms in the crystal structure are crystallographically equivalent and adopt N2O4 coordination mode, whereas the remaining manganese atom adopts O6 coordination mode, which forms a nearly regular octahedron. The experimental result of thermal analysis shows that complex I remains stable below 300°C.

Compressibility and structural properties of jadeite, NaAlSi2O6 at high pressure

The structural properties of jadeite at high pressures (0.000 1–30 GPa) are investigated using plane-wave pseudopotential density functional theory method. As a function of pressure, the monoclinic cell parameters were calculated and the compressibility coefficients are 0.002 6, 0.002 3 and 0.002 6 GPa−1, respectively. The bond length, bond angle and distortion variation were studied in order to obtain the information of polyhedral compression. The pressure-volume equation of state was considered in order to obtain the bulk modulus K0. Comparison between the calculated K0 values and the experimental data suggested that the model provides reasonable insights into crystallographic and physical properties of jadeite.