The effect of the change of the structure on oxidative dehydrogenation of propane over cerium–zirconium catalysts

A series of pure CeO₂, ZrO₂, and CeZrO_x mixed metal oxide catalysts were prepared by a wetness impregnation method and were applied to the dehydrogenation of propane to propylene at 500°C and 0.1 MPa. The prepared catalysts were characterized by thermal gravimetric analysis (TGA), Brunauer, Emmett, and Teller (BET), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopes (TEM), Raman spectroscopy, and H₂-TPR. It was observed that the zirconium content of the solid solution of the mixed metal oxide catalyst was 5%–25%, while the zirconium content of the material with phase segregation was higher (50%). The addition of zirconium was proven to decrease the oxygen vacancy concentration on the catalyst surface and change the intensity of (111) crystal of cerium oxide in the catalysts. Among the prepared catalysts, the Ce_0.90Zr_0.10O_x catalyst with the maximum strength of the (111) crystal plane of cerium oxide exhibited the better catalytic oxidation performance for the dehydrogenation of propane to propylene. Compared with ZrO₂ in the blank experiment, the average propane conversion and propylene selectivity of the Ce_0.90Zr_0.10O_x catalyst were increased by 10.78% and 17.95%, respectively.     

Synergistic flame retardancy of ZnO and piperazine pyrophosphate/melamine cyanurate in polypropylene

In order to improve the flame retardant efficiency and smoke-suppression of piperazine pyrophosphate/melamine cyanurate (PPAP/MCA) in PP, the synergism of ZnO and PPAP/MCA was investigated by limiting oxygen index (LOI) determination, UL-94 test, and cone calorimetry test (CCT). It is found that ZnO performs an exceptional synergism in flame retardant effect and inhibition on the flame propagation. Besides, ZnO can significantly inhibit the production of the smoke and CO. The TGA of the PP composites, the component and structure analysis of the heated composites and CCT residues reveal that ZnO performs the synergism primarily by the following modes: ZnO promotes obviously the charring of the composite, and improves the thermal stability as well as the strength of the intumescent layer, which brings about an improved flame retardant property and inhibiting ability on the flame propagation.     

Model predictive in vitro dissolution testing in pharmaceutical continuous manufacturing: An equivalence study

A predictive mathematical model for tablet dissolution was developed and implemented in an end-to-end integrated continuous manufacturing pilot plant. The tablets were produced for immediate release with a proprietary extrusion-molding-coating (EMC) unit operation. Besides the mass balance of API solute in the buffer solution, the model consisted of the dissolution, diffusion, and population balance of API particles in the swollen tablet, which was mainly controlled by the swelling and erosion of the polymeric excipient matrix. An equivalence study was investigated by comparing the model prediction to the experiments that were conducted according to USP42-NF37 General Chapter <711> Dissolution, during which the drug dose level was varied in a range from 60 to 80 wt%. Consistent equivalence was demonstrated with the similarity factor f₂ > 50 for all sampled tablets. Concluding remarks and industrial perspectives on model predictive in vitro dissolution testing are provided.     

Preparation of γ-linolenic acid rich triacylglycerol from borage oil via a two-step lipase-catalyzed reaction

γ-Linolenic acid (GLA) rich triacylglycerol (TAG) was successfully synthesized from glyceride, instead of glycerol, and fatty acid (FA) via Lipozyme TL IM-catalyzed esterification as a novel strategy. In the first step, GLA was enriched into glyceride fraction from borage oil by Candida rugosa lipase-catalyzed hydrolysis. The glyceride was separated from the reaction mixture by molecular distillation. GLA was enriched from 20.64% in borage oil to 45.94% in the glyceride fraction under optimum conditions. In the second step, the Lipozyme TL IM-catalyzed synthesis of TAG was carried out with the glyceride, and the FA obtained by saponification of a portion of the glyceride. The optimum conditions were the temperature of 50°C, the enzyme loading of 10%, and the vacuum level of 20 mmHg, respectively. The maximum TAG content of approximately 92% was achieved after 12 h under the optimum conditions.     

Microstructures and photovoltaic effect of KNbO3–SrCo0.5Hf0.5O3−δ ferroelectric semiconductors

Polarization is one of the unique properties of ferroelectric materials; yet the polarization mechanism for enhancing ferroelectric photovoltaic performance is rarely been investigated, particularly in terms of bandgap variation. In this work, the effect of high-field polarization on the enhanced photovoltaic performance of a ferroelectric ceramic, 0.98KNbO₃–0.02SrCo_0.5Hf_0.5O_3−δ (KNSCH2), was explored in terms of bandgap variation. The bandgap of the KNSCH2 sample shrank after polarization because of the increase in potential energy band overlap and the upward shift of the valence band due to increased oxygen-vacancy defects. The polarization optimized the energy band structure of KNSCH2, promoting the separation and transport of photoinduced carriers and thus further enhancing its photovoltaic performance. The KNSCH2 sample shows a twofold enhancement in J_sc after 60 kV/cm polarization. The degree of the lattice distortion of KNSNH2 increased following polarization, causing a minute increase in its cell asymmetry. The reasons for the bandgap narrowing and the creation of sub-bandgaps in the KNSCH samples were also investigated. This work opened new doors to understanding the mechanisms underlying the polarization-enhanced photovoltaic performance of ferroelectric materials.     

Optimization of LC droplet size and electro‐optical properties of acrylate‐based polymer‐dispersed liquid crystal by controlling photocure rate

We investigated the effects of the different content ratios of 2‐ethylhexylacrylate (2‐EHA) and 2‐ethylhexylmethacrylate (2‐EHMA) on the relationships among the photopolymerization rate, morphology of liquid crystals (LCs) droplets, and electro‐optical properties of trifunctional urethane acrylate‐based polymer‐dispersed liquid crystal (PDLC) systems. Photo‐differential scanning calorimetry (DSC) analysis and resistivity measurement revealed that increasing 2‐EHMA content gradually decreased the photocure rate of trifunctional urethane acrylate‐based PDLCs, which prolonged the phase separation between the LC molecules and the prepolymers. Morphological observations and electro‐optical measurements demonstrated that trifunctional urethane acrylate‐based PDLCs with the 2‐EHA:2‐EHMA ratios from 4:1 to 3:2 in weight percent formed the favorable microstructures of LC droplets being within the range of 1–5 µm to scatter light efficiently and showed the satisfactory off‐state opacity and on‐state transmittance and the relatively low‐driving voltage. The microstructures of LC droplets and electro‐optical properties of trifunctional urethane acrylate‐based PDLCs could be usefully optimized by controlling the photocure rate using the different 2‐EHA/2‐EHMA content ratios. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3098–3104, 2013     

Temperature-independent and enhanced dielectric properties for two-layer structure capacitors with 0.8Pb(Fe2/3W1/3)O3–0.2PbTiO3–MnO and 0.7Pb(Fe2/3W1/3)O3–0.3PbTiO3–MnO ceramics

This study fabricates capacitors with two-layer structure and different compositions, 0.8Pb(Fe_2/3W_1/3)O₃–0.2PbTiO₃–MnO and 0.7Pb(Fe_2/3W_1/3)O₃–0.3PbTiO₃–MnO, by using the conventional solid state oxide reaction method. By using the temperature compensation effect and adjusting the thickness ratio of the two layers with different compositions, the temperature–dielectric peak is enhanced and smoothed. The dielectric loss, space charge polarization and dc conduction are suppressed at the highest temperature region. Furthermore, the Maxwell–Wagner model is used to fit and explain the dielectric behaviors. This study also provides suggestions and discussion related to the effect of the interfacial region based on the experimental data and fitting results.     

White light emission from Eu co-activated Ca2Gd8Si6O26:Dy nanophosphors by solvothermalsynthesis

Ca₂Gd₈(SiO₄)₆O₂ (CGS) nanophosphors with different concentrations of single-doped Dy³⁺ ions and co-doped Dy³⁺/Eu³⁺ ions were prepared by a solvothermal synthesis. Very fine particles in the nanometer range could be achieved by this method, as evidenced by transmission electron microscope measurements. The hexagonal phase of the oxyapatite structure was confirmed by X-ray diffraction patterns. The energy transfer between Eu³⁺ and Dy³⁺ ions was investigated by photoluminescence excitation and emission properties. These phosphors had absorption bands in the UV and NUV region, which are suitable for the emission wavelength of UV or NUV light-emitting diodes (LEDs). With increasing the Eu³⁺ ion concentration, the emission peak intensity corresponding to the ⁵D₀→⁷F₂ transition increased and the yellow (⁴F_9/2→⁶H_13/2) emission intensity also increased compared to the blue (⁴F_9/2→⁶H_15/2) emission intensity due to the increased energy transfer between Dy³⁺ to Eu³⁺ ions. Thus, the Eu³⁺ ions compensated the red emission component of the Dy³⁺ doped CGS nanophosphors. Such phosphors are expected to have potential applications for NUV based white LEDs.     

Grain growth and crystallinity of ultrafine barium titanate particles prepared by various routes

Variations in tetragonal distortion and the degree of crystallinity of ultrafine BaTiO₃ particles—both industrially applied criteria qualifying their polar characteristics—upon growth during annealing were studied on powders, prepared by the hydrothermal synthesis and by the oxalate route respectively. Regardless of the synthetic route both these properties were found to develop approximately to the same extent with increasing primary particle size. The degree of crystallinity was detectable only above a critical value of c/a=1.007 at an average particle size of around 120 nm. Intragranular porosity in hydrothermal powders and the stoichiometric Ba/Ti-ratio are of minor influence. However, distinct differences in particle growth behavior for both powders were observed. This discrepancy is ascribed to a special morphology of the hydrothermal product, where enhanced particle growth was found to be governed by oriented attachment of individual crystallites and by the motion of solid–solid interfaces.     

水煤浆气化炉使用煤质管理探讨

针对水煤浆气化装置使用煤质比较苛刻,煤质管理难度较大的问题.文章主要从技术角度和管理角度对煤质管理进行剖析,探讨了煤质管理措施及可行性.