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Reaction Kinetics and Catalysis Letters

Current research reports and chronological list of recent articles..




Reaction Kinetics and Catalysis Letters is a medium for the rapid publication of original contributions in such fields as kinetics of homogeneous reactions in gas, liquid and solid phase; homogeneous and heterogeneous catalysis; adsorption in heterogeneous catalysis; transport processes related to reaction kinetics and catalysis; preparation and study of catalysts; reactors and apparatus.

The publisher is Springer. The copyright and publishing rights of specialized products listed below are in this publishing house. This is also responsible for the content shown.

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Additional research articles see Current Chemistry Research Articles. Magazines with similar content (reaction kinetics and catalysis):

 - International Journal of Chemical Kinetics.



Reaction Kinetics and Catalysis Letters - Abstracts



Influence of microwave activation on the catalytic behavior of Pd-Au/C catalysts employed in the hydrodechlorination of tetrachloromethane

Abstract

This work investigates the influence of activation by microwave irradiation on the catalytic properties of Pd-Au/CSibunit catalysts in the hydrodechlorination of CCl4. Pd and Pd-Au samples were thoroughly characterized by CO chemisorption, X-ray diffraction, TPHD and STEM, and used in gas phase hydrodechlorination of tetrachloromethane. The studies showed that homogenous Pd-Au alloys are formed more efficiently if short-time microwave activation is applied instead of conventional activation by H2 reduction at 380 °C. These catalysts show higher activity, stability and higher selectivity towards the desired products (C1–C5 hydrocarbons) than the catalysts activated by conventional reduction in 10%H2/Ar flow.


Datum: 01.06.2018


Physico-chemical characterization of shaped mesoporous silica prepared by pseudomorphic transformation as catalyst support in methane steam reforming

Abstract

In this work, pseudomorphic transformation is introduced as an effective method to prepare mesoporous silica in the shape of millimeter sized disc from a biosilica precursor. The samples were prepared by two approaches. In the former method, pre-shaped silica discs were autoclaved in a basic solution containing cethyltrimethyl ammonium bromide (CTAB) and trimethyl benzene (TMB) to perform pseudomorphic transformation (S1) and in the latter case, silica powders were initially transformed by a pseudomorphic reaction following by shaping them before the removal of CTAB and TMB in calcination and sintering step (S2). The textural properties of the obtained mesoporous silica discs present that S2 sample results in larger pore size and also higher pore volume. The prepared samples have been utilized for preparation of Ni impregnated-silica catalysts in steam reforming of methane. Ni/S2 sample has been shown superior catalytic activity in comparison with other samples (methane conversion of 75% and hydrogen yields more than 40% at 550 °C). The measured physicochemical properties of the samples have been implemented to describe the catalytic results and possible coking mechanism on different samples.


Datum: 01.06.2018


Correlation between the porosity of γ-Al 2 O 3 and the performance of CuO–ZnO–Al 2 O 3 catalysts for CO 2 hydrogenation into methanol

Abstract

The influence of the porosity of γ-Al2O3 on the performance of CuO–ZnO–Al2O3 catalysts for methanol synthesis from H2 + CO2 mixture was studied. Various types of γ-Al2O3 with different surface areas (from 130 to 280 m2/g) and pore sizes (from 3 to 11 nm) were investigated. N2 adsorption, XRD, TPR studies and grand canonical Monte Carlo simulation were utilized to determine the correlation between their physico-chemical properties and catalytic performance. It was shown that the crystallite size of CuO (determined by XRD) and BET surface area of supports are not the key factors for methanol productivity. The TPR profiles of catalysts demonstrated a direct relationship between CuO–ZnO interaction with their catalytic performance. Interestingly, samples with the uniform pore size of 5 nm exhibit a higher CuO–ZnO interaction and the highest methanol yield. In addition, at this pore size, simulation results showed that the ratio of H2 and CO2 inside the γ-Al2O3 pore was 1.5, which could be an appropriate feed ratio for high methanol productivity.


Datum: 01.06.2018


Thiophene oxidation with H 2 O 2 over defect and perfect titanium silicalite-1: a computational study

Abstract

The oxidation mechanisms of thiophene (Tp) with H2O2 over defect and perfect titanium silicalite-1 (TS-1) were investigated by means of DFT/ONIOM2 calculations for different models 7T:45T, 9T:45T and 13T:45T. The B3LYP, ωB97X-D, and M06-2X functionals were used in the high-level part of ONIOM2, with PM6 in the lower-level part. The related potential energy surface profiles are constructed based on the ωB97X-D/ONIOM2 method for 13T:45T cluster. Four possible paths are proposed for the oxidation of Tp into sulfoxide and sulfoxide into sulfone using H2O2 as an oxidant over defect and perfect TS-1. The dimerization of sulfoxide and sulfone through Diels–Alder cycloaddition is also studied. It is found that perfect TS-1 is highly unfavorable compared to defect TS-1 (TS-d). The calculated activation energy of Tp oxidation with TS-d is found to be remarkably lower than that without any zeolite catalyst. The calculated results may contribute to the understanding of the reaction mechanism of the catalytic oxidative desulfurization of sulfides in liquid fuels.


Datum: 01.06.2018


Fabrication of carbon fiber supported zirconium–titanium nanocomposites for efficient photocatalytic decolorization of Orange II dye under visible light irradiation

Abstract

A series of carbon fiber based ZrO2–TiO2 (Zr/Ti/CF) nanocomposites were synthesized with carbon fiber loadings from 3 to 10 wt% by the solvothermal method. For comparison, Zr/Ti, Ti/CF and Zr/CF catalysts were also synthesized. The resultant samples were characterized by SEM, XPS, XRD, FT-IR, and UV–Vis spectroscopy. XRD results revealed that the catalysts were having anatase TiO2 with excellent crystallinity. SEM studies show that the surface of Zr/Ti/CF/10 catalyst has round-shaped grains with dimensions in the range of 16–20 nm. Under UV-A and visible light irradiation, Zr/Ti/CF catalyst exhibited excellent photocatalytic performance for Orange II degradation when compared with Zr/Ti, Zr/CF and Ti/CF. The enhancing efficiency was attributed to the synergetic effect of adsorption–photocatalysis and to the reduction of the band gap energy.


Datum: 01.06.2018


Ethanol conversion reaction over M/ZrO 2 (M = Mg, Ca, Sr, and Ba) catalysts: effect of alkaline earth metal introduction

Abstract

A series of alkaline earth metal-doped M/ZrO2 catalysts (M = Mg, Ca, Sr, and Ba) were prepared by co-precipitation method. The influence of alkaline earth metal on the physicochemical properties and catalytic performance of M/ZrO2 catalysts in the conversion of ethanol was investigated. The catalysts were characterized by N2 adsorption/desorption method, temperature programmed desorption and X-ray diffraction. It was revealed that the introduction of alkaline earth metal changed the acidity/basicity of catalysts and positively enhanced catalytic performance in the ethanol conversion to olefins reaction. The ethylene yield increased with the introduction of alkaline earth metals, which was attributed to higher amount of strong acid sites. The maximum yield of ethylene and propylene reached 80.8% over Sr(1)/ZrO2 catalyst. The adsorption of ethanol on perfect-ZrO2(101) and Sr/ZrO2(101) surfaces was investigated with density functional theory. The adsorption for ethanol on Sr/ZrO2(101) surface was more stable than on perfect-ZrO2(101). The ethanol molecule has stronger interaction with Sr/ZrO2(101) surface than perfect-ZrO2(101) surface.


Datum: 01.06.2018


The effect of different solvents on graphene supported cobalt Fischer-Tropsch catalyst

Abstract

Graphene supported Fischer-Tropsch cobalt catalysts are prepared via hydrothermal synthesis, and the effect of different solvents, water and ethanol used in the preparation on the structure and catalyst activity are discussed. The catalysts are characterized by differential thermogravimetric analysis (DTA), nitrogen physisorption, X-ray diffraction (XRD), Raman spectrum, hydrogen-temperature program reduction (H2-TPR), ammonia temperature programmed desorption (NH3-TPD), scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The results indicate that the catalyst prepared using ethanol as a solvent in a fixed-bed shows better thermostability, lower reduction temperature, smaller crystallite of Co3O4 and relatively narrower and more uniform distribution of Co3O4 crystallite than that prepared in water. The catalyst prepared using ethanol as a solvent exhibits a higher CO conversion and higher C5+ selectivity.


Datum: 01.06.2018


Theoretical investigation of non-uniform bifunctional catalyst for the aromatization of methyl cyclopentane

Abstract

In this work, a mathematical model is considered to investigate the influence of the concentration and the non-uniform distribution of the catalytic sites on the performances of an isothermal fixed bed reactor with axial dispersion and mass transfer resistance under steady state conditions. This model is applied to the methyl cyclopentane aromatization network. The simulation of the model for a particular chemical reaction network showed that the catalyst activity depends on the balance between the number, per unit volume, of the active sites and the way they are distributed throughout the pellet. The model involves the use of two types of catalytic functions (bi-functional) and can be applied to any chemical reaction network related to catalytic reforming.


Datum: 01.06.2018


Photocatalytic CO oxidation with water over Pt/TiO 2 catalysts

Abstract

This paper reports that Pt/TiO2 and to some extent, Pt/Al2O3 and Pt/SiO2 catalysts show some activity in the photocatalytic oxidation of CO by water at low temperature (< 100 °C) in the absence of oxygen. For Pt/TiO2 catalysts, CO conversion is dependent on the Pt loading as well as the temperature of their reduction. There are an optimal platinum loading (5 wt%) and catalyst reduction temperature (500 °C) ensuring the best photocatalytic efficiency. Catalytic performance results from the combined effects of electron–hole photogeneration and partial photodesorption of CO from the platinum surface, followed by the adsorption and subsequent dissociation of H2O. The probable mechanism of photooxidation of CO by H2O was proposed.


Datum: 01.06.2018


Fabrication of immobilized powdered activated carbon as a sub-layer of TiO 2 for the photocatalytic-adsorptive removal of phenol

Abstract

A highly effective and reusable immobilized powdered activated carbon (PAC) was fabricated on the glass plate via a dip-coating technique to remove aqueous phenol. This immobilized PAC layer would become a sub-layer of TiO2 in the TiO2/PAC layer by layer system. The immobilized PAC was characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and Brunauer, Emmett and Teller surface area (S BET ). FTIR spectra showed that PAC did not form any crosslinking reaction with ENR–PVC blend when both materials were mixed while PAC particles were enwrapped with ENR–PVC, which reduced the S BET from 620.3 to 317.5 m2 g−1. It was found that the thickness of immobilized PAC increased proportionally with loadings with improved removal efficiency. Preliminary efficiency tests on immobilized TiO2/PAC layer by layer system under indoor lamp and solar irradiation for phenol removal proved that the immobilized PAC was a suitable sub-layer adsorbent for TiO2.


Datum: 01.06.2018


Ni 2 (BDC) 2 (DABCO) metal–organic framework for cyclic carbonate synthesis from CO 2 and epoxides (BDC = 1,4-benzendicarboxylic acid, DABCO = 1,4-diazabicyclo[2.2.2]octane)

Abstract

A Ni based metal organic framework Ni2(BDC)2(DABCO) has been synthesized by using Ni(II) ions and BDC (1,4-benzendicarboxylic acid) and DABCO (1,4-diazabicyclo[2.2.2]octane) ligands under solvothermal conditions. The prepared catalyst has been analyzed using various physicochemical techniques such as PXRD, FT-IR, ICP-OES, XPS, NH3-TPD, CO2-TPD, and BET. The heterogeneous catalytic performance of synthesized catalyst in the cycloaddition of CO2 and epoxides was investigated without using any solvent under mild reaction conditions. The influence of various reaction parameters like CO2 pressure, catalyst amount, time, and temperature, has been studied. Ni2(BDC)2(DABCO) was reused for five times without any considerable loss in the initial activity. Based on literature inferences and our previous studies, a plausible reaction mechanism for the cycloaddition reaction was also suggested.


Datum: 01.06.2018


Effect of precipitants on the catalytic performance of Pd–Cu/attapulgite clay catalyst for CO oxidation at room temperature and in humid circumstances

Abstract

The Pd–Cu/attapulgite clay catalysts were synthesized using a deposition–precipitation method with different precipitants. The as-synthesized catalysts were characterized by ICP-AES, N2-physisorption, XRD, FT-IR, TEM and TPR. Their catalytic activities for CO oxidation were tested by a fixed-bed continuous flow reactor at room temperature and in humid circumstances. The results illustrated that the activity of CO oxidation strongly depended on the precipitant. The best catalytic performance is achieved by using NH3·H2O (PC-AH) or NH4HCO3 (PC-AHC) as precipitants. The crystalline phase of PC-AH and PC-AHC comprised of Cu2Cl(OH)3 and CuO, while the catalysts prepared with NaOH (PC-SH) or NaHCO3 (PC-SHC) as precipitants were mainly CuO. Combined with FT-IR and TEM results, it could be found that Cu2Cl(OH)3 on PC-AH and PC-AHC possessed higher stability than that on PC-SH and PC-SHC due to the different formation process and morphology of Cu2Cl(OH)3 species. The TPR results showed that the Cu2Cl(OH)3 had a strong interaction with Pd species and enhanced reducibility. Moreover, the residual sodium ions on PC-SH and PC-SHC may have adverse effect on the catalytic activity. A suitable precipitant resulted in the most efficient CO oxidation catalyst at room temperature and in humid circumstances.


Datum: 01.06.2018


Al,Fe,Ni-pillared bentonite in the catalytic wet peroxide oxidation of the textile dye Acid Yellow 99

Abstract

The main goal of this work was to prove that nickel containing Al,Fe pillared bentonites have enhanced catalytic properties. The chosen test system was the catalytic wet peroxide oxidation (CWPO) the Acid Yellow 99 dye (AY99) with the initial concentration of 50 mg dm−3, the amount of H2O2 that exceeded the stoichiometric one, 60 °C, magnetic stirrer, atmospheric pressure. Bentonite was successfully pillared with AlFe and AlFeNi polyoxo cations. The chemical composition of the synthesized samples was: SiO2 56.5, Al2O3 31.3, Fe2O3 9.2; SiO2 56.4, Al2O3 31.9, Fe2O3 8.9 and NiO 0.1; SiO2 61.1, Al2O3 31.3, Fe2O3 4.8 and NiO < 0.01 for AlFe10-PILC, AlFe10Ni5-PILC and AlFe5Ni5-PILC, respectively. The values of textural property parameters decreased in the following order AlFe10-PILC > AlFe10Ni5-PILC > AlFe5Ni5-PILC. Almost complete decolorization was achieved using all synthesized catalysts and followed first order kinetics. AlFe10Ni5-PILC induced the highest decolorization rate. Somewhat higher decolorization rate in the presence of AlFe10Ni5-PILC in comparison with AlFe5Ni5-PILC can probably be ascribed to one of the following properties or their combined effect: higher Fe content and more developed porous structure. Adsorption of AY99 on AlFe5Ni5-PILC and its degradation by H2O2 (without catalyst) were investigated in order for their influence on the decolorization of AY99, in comparison with that of CWPO using AlFe10Ni5-PILC, to be estimated. The adsorption was the least efficient, followed by degradation using H2O2 (without catalyst). CWPO was more efficient when compared to adsorption and degradation by H2O2 together. CWPO using Al,Fe,Ni-PILC can be regarded as promising method for degradation of azo dyes.


Datum: 01.06.2018


The green and expeditious synthesis of sulfated titania with enhanced catalytic activity in polyoxymethylene dimethyl ethers synthesis

Abstract

Sulfated titania solid acid has been successfully synthesized by the one-pot method, which is an economical and environmentally friendly process, compared to the conventional two-step method. The sol–gel process was often chosen as the typical method to prepare these multicomponent samples with excellent chemical homogeneity. Surprisingly, the sulfate species was predominantly anchored on the surface of sulfated titania that was prepared by the one-pot method. Meanwhile, the typical material exhibited higher dimethoxymethane and trioxane reaction rates and polyoxymethylene dimethyl ethers formation rates, compared to catalysts obtained by the wet-impregnation method. Moreover, this green process was more controllable and could be a promising alternative for the preparation of sulfated titania oxides.


Datum: 01.06.2018


Promoted catalytic performance of Ni-SBA-15 catalysts by modifying with Fe and Cu for hydrogenation of levulinic acid to gamma-valerolactone

Abstract

A series of Ni-based SBA-15 catalysts were prepared via a wet impregnation method and tested for hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL). A GVL yield of 56% was obtained over Ni-SBA-15 catalyst and the GVL yield increased to 64% as the addition of Fe. Compared with the results above, a better performance with 93% GVL yield was obtained over the Ni–Fe–Cu/SBA-15. Extensive catalysts characterization techniques including TPR, XRD, XPS and porosity analysis have been performed to study the nature of nickel-based catalysts. Porosity analysis and XRD showed that all the studied catalysts had a typical mesoporous texture. The TPR and XPS results indicated that there was a strong interaction among Ni, Fe and Cu species and the nickel species was relatively enriched on the surface of the catalysts, which could be accounting for the highest catalytic performance of the Ni–Fe–Cu–SBA-15 catalyst with GVL yield of 93%. In addition, the reaction parameters such as temperature, time, catalysts loading and H2 pressure have been systematically optimized, giving a near quantitative yield of GVL over Ni–Fe–Cu/SBA-15 in the presence of the reaction temperature of 200 °C, time of 5 h, mass ratio of catalyst/reactant LA 0.3 and H2 pressure of 3.0 MPa.


Datum: 01.06.2018


Industrial application of molecular computations on the dimerization of methylene diphenyl diisocyanate

Abstract

In the polyurethane industry, the undesirable dimerization and oligomerization of methylene diphenyl diisocyanate (MDI) are unwanted and problematic phenomena. The relative ratios of these dimers and oligomers have a strong temperature dependence, and they can be formed below and above the melting point of MDI (316.15 K). All possible structures of the isomers and their dimers were optimized, and then their thermodynamic functions were calculated at the M06-2X/6-31(d,p) level of theory. The dimerization of isocyanate groups can result in four-, five-, and six-membered rings. The four-membered ring is the most stable one due to the aromatic electrons in π orbitals of the uretidione ring. The relative stability of the dimers is therefore influenced by the steric effects and the relative positions of isocyanate groups. The most stable dimer is the one which is formed from the reaction of the p,o- and o,p-MDI isomers due to their intrinsic interactions, which were classified, and their impact on dimer stability was discussed.


Datum: 01.06.2018


Enhanced catalytic activity of graphene oxide/CeO 2 supported Pt toward HCHO decomposition at room temperature

Abstract

Graphene oxide (GO)/CeO2 nanocomposite supported Pt catalysts were prepared for formaldehyde (HCHO) oxidation at room temperature. The investigation showed that the addition of GO could enhance the catalytic performance of Pt supported on CeO2 (Pt/Ce) catalyst mainly due to the functional features of GO nanosheets. The content of GO in the composite catalyst had an effect on the catalytic activity of the prepared catalysts. Formate species were the main intermediates during HCHO oxidation over GO/CeO2 nanocomposite supported Pt catalyst investigated by in situ DRIFTS. The most active GO/CeO2 supported Pt catalyst (Pt/Ce-2) exhibited a good stability for removal of HCHO, indicating it a potential alternative catalyst for complete decomposition of HCHO into CO2 and H2O at room temperature.


Datum: 01.06.2018


Effect of water and methanol in the production of methyl methacrylate over iron phosphate catalysts

Abstract

This work discusses two production routes to methyl methacrylate (MMA) over an iron phosphate catalyst, namely oxidative dehydrogenation of methyl isobutyrate (MIB) and isobutyric acid (IBA) with methanol as co-feed. In situ studies show that at 400 °C, a mixture of the iron tridymite and quartz like phases are present under air, H2 and N2. The catalyst was tested in a fixed bed stainless steel reactor. The feed was passed over the catalyst with air and methanol; and air, water and methanol. The effects of the water to feed ratio and methanol to feed ratio were studied in terms of maximum conversion, yield and selectivity to MMA. Using methyl isobutyrate as a feed and methanol as a co-feed, the best yield of methylmethacrylate obtained was 40%. This corresponds to a selectivity of 73%, at a conversion of 55%. Feeding isobutyric acid and methanol over the iron phosphate catalyst gave an optimum yield of 15% methyl methacrylate at 400 °C. The yield of the products increased with increasing methanol/IBA ratio due to methanol limiting the hydrolysis reactions. The results obtained in this study show that MMA can be formed by the oxidative dehydrogenation–esterification of IBA and methanol over the iron phosphate catalyst.


Datum: 01.06.2018


Selective catalytic reduction of NO x with NH 3 over Sb modified CeZrO x catalyst

Abstract

A series of novel Sb modified CeZrOx catalysts were prepared by a homogeneous precipitation method and used for the selective catalytic reduction NOx by NH3 (NH3-SCR). The CeSbZrOx catalyst exhibited high SCR activity and SO2/H2O resistance. The characterization results showed that the addition of Sb into the CeZrOx catalyst inhibited the growth of CeO2 crystallite size, enlarged the surface area and pore volume, increased the acidity and enhanced the redox ability, intensified the NH3 and NOx adsorption capability and improved Ce3+/Ce4+ molar ratio on the catalyst surface, all of which were responsible for achieving the high NH3-SCR activity.


Datum: 01.06.2018


The particular characteristics of the active sites of MoS 2 , WS 2 catalysts in thiophene hydrodesulfurization

Abstract

It was reported in earlier studies that a linear correlation existed between the total sulfur exchange capacity and thiophene hydrodesulfurization activity of different, alumina- or silica-supported molybdenum- or tungsten-sulfide based porous catalysts promoted with different metals: Co, Ni, Pt and Pd. The aim of this study was to clear up how general the linear correlation is, whether that correlation is generally applicable, whether it shows a particular character of the active sites in thiophene hydrodesulfurization (HDS). Industrial catalysts are more complex than typical model catalysts so the extents of thiophene HDS were determined on six industrially manufactured catalysts available today (combinations of Mo, W and Ni supported on alumina and of one NiW on silica-alumina) and compared to their sulfur uptake, and radiosulfur exchange capacity at 623 K. The majority of these catalyst samples also contained some phosphorus in different amounts. The results of the cyclohexane dehydrogenation as a model reaction indicated the absence of metallic nickel on the surface of the catalysts. A linear correlation was observed between the sulfur exchange capacity and HDS activity of these catalysts (with the exception of the sample supported on silica-alumina) similar to that observed previously.


Datum: 01.06.2018


 


Category: Current Chemistry Research

Last update: 03.04.2018.






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