Le, DuyChaidherasuwet, NattapornHinchiranan, Napida
13页
查看更多>>摘要：This study investigated the effect of magnesium oxide (MgO) incorporation into vanadium-KIT-6 (VKIT-6) catalysts and vanadium oxide (VxOy) contents impregnated into MgO-KIT-6 catalysts on the catalytic activity in the oxidative dehydrogenation of oleic acid to generate long-chain bio-olefins (>= C10). The nMgO-VKIT-6 catalysts containing different Mg/V molar ratios (n = 0.00-1.50) were prepared by the hydrothermal process, while xV/ MgO-KIT-6 catalysts were synthesized via wet-impregnation method with different vanadium contents (x = 0-9 wt%). The Mg/V molar ratios in the nMgO-VKIT-6 catalysts and VxOy contents in the xV/MgO-KIT-6 catalysts strongly affected the catalytic performance and selectivity to the desired products. Both 0.50MgOVKIT-6 and 1 V/MgO-KIT-6 catalysts showed the best catalytic activity for the desired products with selectivity to olefins (alkenes + dienes) and aromatics of 52% and 20%, respectively. The high selective production to the desired products was ascribed to the highly dispersed and isolated VxOy species on the catalysts.
查看更多>>摘要：Reprocessing end-of-life polymethyl methacrylate (PMMA) in fluidized beds substitutes fossil fuels as a feedstock for methacrylic acid (MAA). Impurities and high operating and separation costs thwarted the commercialization of the simpler thermolysis PMMA to methyl methacrylate process. In a thermogravimetric analyzer, < 6% of the PMMA decomposed at 230 ?, whereas it all reacted at 350?. In a 13 mm diameter micro-fluidized bed, all the PMMA reacted within 10 min at 350? while at 230? <= 30% reacted. Catalysts like gamma-A(2)O(3), FCC, MoO3-ZrO2/SiO2, zeolite Y, and CsxH(3)-xPW12O40/SiO2 hydrolyze MMA to MAA. The maximum MAA yield was less than 8% for gamma-A(2)O(3), FCC, MoO3-ZrO2/SiO2, while it reached 20% for the Cs heteropoly acid over SiO2 at 280 ?C and exceeded 30% with zeolite Y. Coking on the catalyst and product decomposition along the reactor wall reduced MAA yield. A tandem reactor configuration-thermolysis followed by hydrolysis-will maximize MAA yield.
查看更多>>摘要：The activity and selectivity of the Fe-based catalysts with different FeCx species had been long debated in Fischer-Tropsch Synthesis (FTS). In this manuscript, FeCx was encapsulated in carbon matrix by Prussian blue (Fe4(Fe(CN)(6))(3), PB) thermal treated, and the FeCx@C catalysts could be directly prepared. With the calcination temperature increasing, the FeCx species of core and the thickness of carbon shell in FeCx@C catalysts can be continuously tuned through adjusting the calcination temperature. Further characterization results suggested that the decarburization of FeCx@C catalyst occurred from the inside to the outside. In addition, the FTS results showed the value of carbon-chain growth probability (alpha value) presented the positive relationship with the catalyst calcination temperature. This work provides a novel and simple route to synthesize FeCx@C catalyst, and also provides evidence for the mechanism of FeCx species from the perspective of decarburization.
查看更多>>摘要：A spatially resolved technique was developed as a novel methodology to investigate the process of effective diffusions in monolith catalysts. The technique was then applied to the investigation of methane oxidation inside a commercial 3 wt% Pd/Al2O3 monolith catalyst. The mass transfer parameters of O-2 and CH4 were measured, and their effective diffusivities were calculated by a modified Bosanquet approach, which confirmed that the dominant diffusion regime in the substrate and the washcoat were molecular and Knudsen respectively. The applicability of this new approach was assessed via a comparison between simulations of the water-inhibited CH4 catalytic oxidation using either correlation or experimental-based mass transfer coefficients. This study demonstrates that careful measurement of diffusivity is essential to the accurate modelling of catalyst reaction rates.
Sutradhar, ManasMartins, Marta G.Simoes, David H. B. G. O. R.Serodio, Rita M. N....
9页
查看更多>>摘要：The aroylhydrazone Schiff bases 2-hydroxy-N'-(1-(pyrazin-2-yl)ethylidene)benzohydrazide and N,N'-bis(2-hydroxybenzylidene)oxalohydrazide, have been used to synthesize the dinuclear complexes [VO(HL1)(mu-O)](2) (1) and [{VO(OEt)(EtOH)}(2)(L-2)] (2)center dot 2 H2O. Complex 1 is newly synthesized and 2 was reported earlier. Structural characterization of 1 was accomplished by single crystal X-ray diffraction, elemental analysis, and IR spectroscopy. The catalytic performance of both vanadium complexes was investigated for the peroxidative oxidation of toluene and benzyl alcohol through advanced oxidation processes (AOPs). Besides the conventional heating (CONV), other energy inputs, i.e., ultrasound-assisted (US_PROBE and US_BATH) and photo-assisted (PHOTO) methods were explored. The effects of a series of parameters were studied to improve the catalytic reaction. For the peroxidative oxidation (H2O2, 30% aq.) of toluene for 1 h at room temperature, the oxygenated product yields followed the trend: US_PROBE (8.1%) > US_BATH (5.4%) > PHOTO (3.9%) > CONV (no oxygenated products). The effect of other energy inputs (besides conventional heating) in the formation of oxygenated products is even more pronounced in the peroxidative oxidation of benzyl alcohol carried out for 1 h at room temperature, with the following trend: US_PROBE (59.5%) > PHOTO (30.9%) US_BATH (21.5% of oxygenated products) > CONV (no oxygenated products detected). Complexes 1 and 2 are promising catalysts for the conversion of toluene and benzyl alcohol under very light reaction conditions when assisted by ultrasound irradiation, and this sonochemical approach is disclosed as a promising advanced oxidation process (AOP).
查看更多>>摘要：Herein, we show that textural properties of carbon supports have limited influence on the activity and stability of carbon supported Pd, Pt and Ru catalysts upon decarboxylation of a model triglyceride (tristearin) in the presence of subcritical water (256-326 ?). In contrast, surface acid-base properties of carbon supports were found to have a marked impact on the performance and stability of these catalysts. More precisely, for Pt group (Pt and Pd) a positive correlation could be observed between the concentration of surface basic sites and catalyst deoxygenation activity and durability while acid sites had the opposite effect. On the other hand, the activity of Ru-based catalysts were not analogously affected by the acid-base properties of carbon supports, even so a positive correlation was found between surface basicity and durability (reusability). Further, the activity of metals in decreasing order of TOF was Ru > Pt > Pd, irrespective of carbon support.
查看更多>>摘要：The design of highly efficient catalysts for CO2 reforming with ethanol is of great interest due to the serious coke deposition and the sintering of active metal. In this work, sandwich-type Co core@shell catalyst (SiO2 & nbsp;@Co@CeO2) with Co nanoparticles between SiO2 core and CeO2 shell was synthesized by strong electrostatic adsorption method. Interestingly, SiO2 @Co@CeO2 catalyst exhibited the outstanding activity/stability toward CO2 reforming of ethanol in comparison with Co-SiO2 catalyst. A bi-functional mechanism involving active sites on CeO2 shell was proposed. Indeed, cobalt nanoparticles between SiO2 core and CeO2 shell maintained the high dispersion because of the confinement effect, which supplied a stable Co-ceria interface area where the reaction occurred. In addition, CO(2 & nbsp;)could readily react with the O vacancies in CeO2 shell to form surface oxygen species and CO, which allowed a continuous cleaning of coke. These positive factors could make it as an attractive candidate for dry reforming process.
Nuguid, Rob Jeremiah G.Ferri, DavideLiu, QingcaiKroecher, Oliver...
14页
查看更多>>摘要：Mn-Ce/AC catalysts for low-temperature NH3-SCR of NOx were deliberately loaded with various potassium salts (KCl, KNO3, and K2SO4) to investigate the influence of the counter-ions on the poisoning impact. Whereas K salts poisoning had only marginal impact on the textural properties of the catalysts, but it altered the chemical properties of the catalysts significantly. Potassium addition lowered the relative surface concentration of Mn4+ and M-O in Mn-Ce/AC catalyst, suggesting that K might occupy the oxygen vacancies around Mn atoms, thereby weakening the NH3 adsorption. The extent of inhibition strongly depended on the anion, with Cl- causing a higher degree of poisoning than that of either NO3- or SO42- . While K+ could hinder NH3 adsorption, both NO3and SO42- provided new acid sites that could offset the deactivation.
查看更多>>摘要：A novel approach is reported for efficient esterifying low molecular acids with alcohols in molten salt hydrate (MSH) without additional catalyst. A series of MSHs (LiCl, CaCl2, ZnCl2 and ZnBr2) were evaluated for catalytic esterification of chloroacetic acid (CA) with methanol to methyl chloroacetate (MC). The effects of coordination water number also examined. It was found that appropriate coordination water number not only can promote the protonation of the reactant acids, but also enhance the activity of the protons as well as esterification equilibrium towards ester formation. A MC yield of 98.1% with concentration of 92.1% in the organic-phase could be readily achieved after reacting at 80 degrees C for 2.0 h in CaCl2.4H2O. MSH also demonstrated excellent performance in esterification of other acids (acetic, mercaptoacetic, propionic, n-butyric and levulinic acids) with alcohols (ethanol, n-propanol and n-butanol). After removing portion of the water from MSH, it can be reused without any difficulty. The promotion effects of MSH on the esterification reaction can be categorized to three aspects: (1) accelerating the reaction rate due to the enhanced protonation of the reactant acids and reduction in the hydration degree of the protons; (2) facilitating phase-splitting by virtue of the poor solubility in MSH and thus expelling the formed esters into organic-phase, as a result, boosting up esterification conversions; and (3) promoting the esterification reaction equilibrium owing to the strong hygroscopicity of MSH.Economic analysis shows, compared with the conventional esterification of CA with ethanol, in which organic solvents is used as the water-carrying agent, that esterification in MSH could not only accelerate the reaction rate and strengthen the equilibrium conversion, but also save energy input.
查看更多>>摘要：Porous boron nitride was synthesized using boric acid with urea and/or hexamethylenetetramine (HMTA) via pyrolysis method. X-ray diffraction and Fourier transform infrared measurements indicated that the synthesized boron nitride has a turbostratic structure with both amino and hydroxyl group on the surface. The synthesis using a mixture of two nitrogen-containing precursors was found to not only significantly increase the porosity, but also improve the surface functionality. X-ray photoelectron spectroscopy and B K-edge and O K-edge X-ray absorption fine structure measurements revealed that the proportion of amino and hydroxyl groups on the surface increased with increasing concentration of HMTA during synthesis. Solid-state 11B nuclear magnetic resonance spectroscopy indicated that all samples contained trigonal B-N, trigonal B-O and tetrahedral B-O sites, and that samples prepared with high concentrations of HMTA had less tetrahedral B-O sites, suppressing the formation of BOx species as byproducts. Solid base catalytic activity was evaluated through Knoevenagel condensation, and the catalytic performance was significantly improved by synthesizing boron nitride catalyst using a mixture of the two nitrogen-containing precursors. The enhancement of the activity was influenced by the development of the pore structure as well as the emergence of functional groups on the surface.
NSTL
Elsevier