The chromium terephthalate MIL‐101 has been prepared rapidly and efficiently by using microwave‐assisted hydrothermal synthesis. The resulting material exhibits giant pores and very large surface ...areas and demonstrates a huge, rapid adsorption of benzene in both vapor (see figure) and liquid phases.
As a size‐selective molecular sieve, the coordination polymer formed from cobalt and pyridine‐2,4‐dicarboxylic acid (CUK‐1, see figure) shows unprecedented selectivity for O2 and preferential ...selectivity for CO2 over CH4. The present sorption results encourage the development of new adsorbent materials that may find use in the production of high‐purity gas products. This work demonstrates that CUK‐1 can be utilized, for the first time, in the separation of light gases via gas chromatography.
Bifunctional heterogeneous catalysts with pore structure have been synthesized by the coupling between nickel oxide and titanium oxide. The resulting porous nanocomposites show promising bifunctional ...catalytic activity against the selective epoxidation of olefin molecules as well as visible light driven photolysis.
Cerium-containing mesoporous materials have been synthesized by hydrothermal method and characterized by IR, DR-UV–vis and DRIFT spectroscopy, XRD and N
2 adsorption methods. Important factors ...affecting the catalytic activity of Ce-SBA-15, namely the effect of cerium content, the state of cerium ions, the state of silanol groups on the surface of Ce-SBA-15 and stability of the catalyst have been studied in the cyclohexanol and cyclohexene oxidation with hydrogen peroxide. The reaction mechanism was discussed.
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Cerium-containing mesoporous materials have been synthesized by hydrothermal method and characterized by IR, DR-UV–vis and DRIFT spectroscopy, XRD and N
2 adsorption methods. It was established that the
d
100 and unit-cell (
a
0) parameter increase with the increase of cerium content up to 2% in SBA-15 and then tend to remain the same. According to DR-UV–vis spectroscopic data, an agglomeration of cerium atoms was observed in the form of fine CeO
2 crystallites. Important factors affecting the catalytic activity of Ce-SBA-15, namely the effect of cerium content, the state of cerium ions, the state of silanol groups on the surface of Ce-SBA-15, and stability of the catalyst have been studied in the cyclohexanol and cyclohexene oxidation with hydrogen peroxide.
Zeolitic imidazolate frameworks (ZIFs) possess unique structural, textural, and physico-chemical properties and, therefore, they are promising materials for the synthesis of catalysts. The presence ...of acidic and basic sites in the structure of ZIFs and the possibility of controlling their number and accessibility offer various ways of using ZIFs in acid-base catalysis. Domestic and foreign works devoted to the study of the catalytic properties of ZIFs in reactions of the acid-base type and published within the recent 15 years are reviewed. Special attention is given to the effect of the crystal size of ZIFs on their catalytic properties in such reactions as condensation, cyclization, and esterification. The advantages and drawbacks of ZIFs as catalysts and the main questions that arise during practical use are considered.
Catalytic properties of transition-metal-containing silicate materials with hexagonally packed mesopore-channels, Ti-MMM-2 and Ce-SBA-15, have been studied in oxidative cleavage of cyclohexene (CyH) ...to adipic acid using aqueous H2O2 as oxidant. In a solvent-free system, the yield of adipic acid reached 10-15% at H2O2/CyH 3.6 mol mol-1 and 80 deg C after 72 h. The stepwise addition of the oxidant to the reaction mixture allowed increasing the yield of the target product up to 33 and 18% for Ti-MMM-2 and Ce-SBA-15, respectively. For both catalysts, the yield of adipic acid decreased significantly in the second run despite CyH conversion attained 100%. The catalyst stability and the reasons of the deactivation have been explored. For both catalytic materials, partial decrease of the mesopore surface area and mesopore volume was observed after the CyH oxidation run. DRS-UV-vis study revealed irreversible formation of oligomerized TiO2-like species on the Ti-MMM-2 surface due to interaction of Ti centres with the oxidant and the reaction products. The elemental analysis data showed that adipic acid causes leaching of titanium from Ti-MMM-2 into solution. Ce-SBA-15 was found to be more stable with respect to the active metal leaching but prone to deactivation due to agglomeration of cerium ions to form cerium oxide nanocrystallites; partial reduction of Ce(IV) to Ce(III) also occurred.
Pure and Ru-doped nanostructured SnO
2 sensing materials were synthesized using a modified Pechini route. Incorporation of Ru in SnO
2 results in the reduction of particle size (8.3
nm) compared with ...that of the pure SnO
2 (28.2
nm). Moreover, the sensor exhibited a reasonably good sensitivity towards both H
2 and liquified petroleum gas (LPG). The effect of Ru incorporation, operating temperature, and gas concentration on the structure, morphology, and sensitivity is discussed using the results of X-ray diffraction (XRD), and scanning electron microscopy (SEM) along with sensing performance.
Introduction
Incidence for depression increases during the perinatal period. Risk factors for depression may differentially affect each time period.
Objectives
To assess demographic, psychological ...and obstetric risk factors that differentially affect prenatal and postpartum depression
Methods
A total of 169 subjects participated. Assessment was conducted during the first trimester, second trimester, third trimester, within a month after childbirth, and a month after childbirth. Demographic and obstetric measures, as well as psychological measures, including the Edinburgh Postnatal Depression Scale were conducted. Multiple regression and the Mann-Whitney U test were performed to examine the association between variables and depression scores.
Results
Depression score was higher during the postpartum period than the prenatal period. Younger age was associated with depression during the first trimester. In the second trimester, less education, a history of depression and having stress within a year significantly affected depression scores. Smoking, artificial abortion and lack of support from family and parents correlated with depression during the third trimester. Within a month after childbirth, psychiatric and depression history, smoking, stress level within a year and lack of family support were associated with depression. At a month after childbirth, those who were primiparous and not breastfeeding had significantly higher depression scores.
Conclusions
This study identifies various risk factors for each gestational and postpartum period and suggests differential interventions for different perinatal periods.
SAPO-5 and SAPO-34 molecular sieves can be selectively formed with microwave irradiation and hydrothermal heating, respectively, of the same gel irrespective of the acidity or the type of the ...templates such as triethylamine and
N,
N,
N
′,
N
′-tetraethylethylenediamine. The SAPO-5 structure may transform into the SAPO-34 structure with increase of crystallization time probably due to the relative stability of the two phases at the reaction conditions. Crystallization with microwave irradiation can be used as a phase selective synthesis method for unstable material because of fast crystallization.
The effect of synthesis parameters such as H
2O/Ti, Ba/Ti and OH
−/Ti ratios and heating methods (microwave irradiation and hydrothermal heating) on the synthesis of BaTiO
3 crystals has been ...investigated to prepare nanocrystalline BaTiO
3 crystals. The nanocrystals (less than 30 nm) were synthesized with microwave irradiation of reaction mixture prepared from conventional chloride precursors. The crystal size decreased with an increase of hydroxide and barium concentrations, whereas the size decreased with a decrease of the water concentration. Synthesis of BaTiO
3 with the microwave provided advantages of fast crystallization and decreased crystal size.
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