Yunjie Ding

Why lanthanum-substituted bismuth titanate becomes fatigue free in a ferroelectric capacitor with platinum electrodes

Bi4Ti3O12, (BTO) a Bi-layered perovskite oxide, shows fatigue after repeated ferroelectric polarization reversals. On the other hand, Bi3.25La0.75Ti3O12 (BLT) is fatigue free. From an extensive transmission electron microscopy study, it was found that there is a high density of antiphase boundaries (APBs) in BLT like in the fatigue-free SrBi2Ta2O9 but not in BTO. It is proposed that the existence of APBs possibly plays a key role in the fatigue-free behavior of Bi-layered perovskite oxides.

Glycerol dehydration to acrolein over activated carbon-supported silicotungstic acids

Activated carbon (AC)-supported silicotungstic acid (H-4[SiW12O40] center dot nH(2)O, HSiW) catalysts were employed to produce acrolein from glycerol dehydration. The results indicated that catalysts with 10% HSiW loading exhibited the highest activity and selectivity. The space time yield of acrolein reached 68.5 mmol/(g.h), which is the best result ever reported in the literature. The properties of the catalysts were closely related to the HSiW dispersion and the relative quantities of strong acid sites.

A study of Rh-Sm-V/SiO2 catalysts for the preparation of C2-oxygenates from syngas

Abstract Rh-Sm-V/SiO 2 catalysts for the preparation of C 2 -oxygenates were studied by CO+H 2 reactions under medium pressure, temperature-programmed reduction, adsorption of H 2 and CO, and desorption of adsorbed hydrogen. The addition of Sm and V to the Rh/SiO 2 catalyst obviously promoted the activity and selectivity to C 2 -oxygenates. The Sm 3+ ions on the catalysts can be reduced only with difficulty. These Sm 3+ ions play roles of improving the dispersion of rhodium, increasing the uptakes of CO and H 2 , and promoting the formation of acetic acid and acetaldehyde. Vanadium ions of lower valence have a good capacity of hydrogen storage, and this can enhance the hydrogenation ability of the catalyst, as well as promoting the formation of ethanol.

Effects of zirconia phase on the synthesis of higher alcohols over zirconia and modified zirconia

The catalytic performances of ZrO2-based catalysts were evaluated for the synthesis of higher alcohols from synthesis gas. The crystal phase structures were characterized by X-ray diffraction (XRD) and UV Raman. The results indicated that ZrO2 and Pd modified ZrO2 catalysts were effective catalysts in the synthesis of ethanol or isobutanol, and their selectivities basically depended on the crystal phase of ZrO2 surface. The ZrO2 with surface tetragonal crystal phase exhibited a high activity to form ethanol, while the ZrO2 with surface monoclinic crystal phase exhibited a high activity to form isobutanol. Temperature-programmed desorption (TPD) experiment indicated that the high activity of isobutanol formation from synthesis gas over monoclinic zirconia was due probably to the strong Lewis acidity of Zr4+ cations and the strong Lewis basicity of O2− anions of coordinative unsaturated Zr4+–O2− pairs on the surface of monoclinic ZrO2.

Solvent Effect on Selective Dehydroxylation of Glycerol to 1,3-Propanediol over a Pt/WO3/ZrO2 Catalyst

Different solvents were studied for dehydroxylation of glycerol to1,3-propanediol over a Pt/WO3/ZrO2 catalyst. Protic solvents such as ethanol and water favored the formation of 1,3-propanediol from glycerol. Binary solvents containing a protic component showed a synergetic solvent effect on the selective dehydroxylation of glycerol to 1,3-propanediol. The protic component in the binary solvent influenced the performance of the Pt/WO3/ZrO2 catalyst.

Influence of lanthanum on the performance of Zr-Co/activated carbon catalysts in Fischer-Tropsch synthesis

Abstract The influence of La loading on Zr-Co/activated carbon (AC) catalysts has been studied for Fischer-Tropsch synthesis. The catalyst samples were characterized by XRD, TPR, CO-TPD, and temperature programmed CO hydrogenation. The catalytic property was evaluated in a fixed bed reactor. The experimental results showed that CO conversion increased from 86.4% to 92.3% and the selectivity to methane decreased from 14.2% to 11.5% and C 5+ selectivity increased from 71.0% to 74.7% when low La loading (La = 0.2wt%) was added into the Zr-Co/AC catalyst. However, high loadings of La (La = 0.3–1.0 wt%) would decrease catalyst activity as well as the C 5+ selectivity and increase methane selectivity. XRD results displayed that La-modified Zr-Co/AC catalyst had little effect on the dispersion of Co catalyst. But, the results of TPR, CO-TPD, and temperature programmed CO hydrogenation techniques indicated that the extent of cobalt reduction was found to greatly influence the activity and selectivity of the catalyst. The addition of a small amount of La increased the reducibility of the Zr-Co/AC catalyst and restrained the formation of methane and improved the selectivity to long chain hydrocarbons. However, excess of La led to the decrease of the reducibility of Co catalyst thus resulted in higher methanation activity.

Single atom dispersed Rh-biphephos&PPh3@porous organic copolymers: highly efficient catalysts for continuous fixed-bed hydroformylation of propene

A vinyl functionalized biphephos ligand with high steric hindrance was copolymerized with tris(4-vinphenyl)phosphane and other ligands to afford efficient porous organic copolymers (POPs) through the solvothermal synthesis technique. By employing the copolymer self-supported heterogeneous Rh/CPOL-bp&P catalysts, the hydroformylation of propene to linear-butaldehyde can be performed efficiently in a continuous fixed-bed reactor with high regioselectivity (l/b > 24), activity (TOF > 1200 h−1) and stability (over 1000 h) under mild conditions (70 °C, 0.5 MPa), which represents a substantial improvement in the efficiency of this important industrial process. EXAFS and HAADF-STEM showed that the Rh was a single atom dispersion, which explained well the high efficiency of the Rh/CPOL-bp&P catalysts. Compared with liquid–liquid biphasic (LLB) and ionic liquid (IL) systems, this highly efficient solvent free system has the advantages of simple operability, and almost no waste emission, which meets the demands of green industrial processing.

Supported rhodium and supported aqueous-phase catalyst, and supported rhodium catalyst modified with water-soluble TPPTS ligands

Two types of novel catalysts: supported rhodium and supported aqueous-phase (SAP/Rh-SiO2), and supported rhodium modified with water-soluble TPPTS ligands (TPPTS-Rh/SiO 2), were prepared. Hydroformylation of 1-hexene showed that SAP/Rh-SiO2 and TPPTS-Rh/SiO2 catalyst processed high activity for aldehydes and especially high selectivity towards aldehydes and high n/i- ratio of aldehydes. These results were significantly different from the performances of Rh/SiO 2 catalyst, but very comparable to those of SAP catalyst. 31 P NMR spectrum of TPPTS-Rh/SiO2 catalyst demonstrated that TPPTS ligands chemically bonded to highly dispersed rhodium metal particles. It make clear the reason that yield of aldehydes of SAP/Rh-SiO2 was nearly the sum of the yield of SAP catalyst and the yield of TPPTS-Rh/SiO2 catalyst, while all of catalytic selectivities were equal, because SAP/Rh-SiO2 was actually made up of SAP and TPPTS-Rh/SiO2 catalysts. The catalytic performance of TPPTS-Rh/SiO2 catalyst strongly depended on the molar ratio of P:Rh, which was similar to that of SAP catalyst to a certain extent.

A Review on the Synthesis and Applications of Mesostructured Transition Metal Phosphates

Considerable efforts have been devoted to extending the range of the elemental composition of mesoporous materials since the pioneering work of the M41S family of ordered mesoporous silica by Mobil researchers. The synthesis of transition metal-containing mesostructured materials with large surface area and high porosity has drawn great attention for its potential applications in acid and redox catalysis, photocatalysis, proton conducting devices, environmental restoration and so on. Thus, various transition metals-containing mesoporous materials, including transition metal-substituted mesoporous silicates, mesostructured transition metal oxides and transition metal phosphates (TMP), have been documented in the literature. Among these, mesostructured TMP materials are less studied, but possess some unique features, partly because of the easy and facile functionalization of PO4 and/or P–OH groups, rendering them interesting functional materials. This review first introduced the general synthesis strategies for manufacturing mesostructured TMP materials, as well as advantages and disadvantages of the respective method; then, we surveyed the ongoing developments of fabrication and application of the TMP materials in three groups on the basis of their components and application fields. Future perspectives on existing problems related to the present synthesis routes and further modifying of the functional groups for the purpose of tailoring special physical-chemical properties to meet wide application requirements were also provided in the last part.

Effect of Al2O3 Promoter on a Performance of C1–C14 α-Alcohols Direct Synthesis over Co/AC Catalysts via Fischer–Tropsch Synthesis

The influence of Al2O3 promoter on a performance of C1–C14 α-alcohols direct synthesis from syngas over activated carbon (AC) supported cobalt catalysts (Co/AC catalysts) was investigated using CO hydrogenation evaluation, XRD, HRTEM, H2-TPR, pulsed CO chemisorption, H2-TPD and N2 physisorption techniques. The results obtained showed that the addition of Al2O3 increased significantly the Co component dispersion without remarkably decreasing its reducibility and inhibited its aggregation during reaction, resulting in greatly enhanced reaction activity as well as increased selectivity towards liquid products. Appropriate amounts of Al2O3 can promote the formation of Co2C, leading to an increase of total alcohol fraction in the liquid products. Moreover, the Al2O3 addition can further promote the formation of higher alcohols (C6–C14 alcohols).Graphical Abstract