Formation of compaction products in methane dry reforming on a Ni-containing catalyst

The formation of compaction products and their morphological features in the process of methane dry reforming on a Ni₃Al catalyst were studied. It was shown that the initial porous structure of a sample was retained in the course of reaction, and the formation of carbon deposits did not decrease the catalytic activity of Ni₃Al over a long period of time.     

Mechanistic study on dimerization of acetylene with a Nieuwland catalyst

A mechanistic study on the Nieuwland catalysis for dimerization of acetylene is performed by detecting copper–acetylene and copper–monovinylacetylene π‐complexes and also by examining the kinetics under virtually the same reaction conditions employed in the industrial process. An efficient H/D exchange occurs between acetylene and protons in the Nieuwland catalytic system. Addition of a coordinating ligand to the conventional Nieuwland catalytic system results in improvement of the catalytic activity and selectivity for the acetylene dimerization. The kinetic analysis including the kinetic deuterium isotope effect provides valuable insight into the Nieuwland catalytic mechanism of the dimerization of acetylene. Copyright © 2008 John Wiley & Sons, Ltd.     

Dehydrogenation inhibition on nano-Au/ZSM-5 catalyst: a novel route for anti-coking in methanol to propylene reaction

A novel route for anti-deactivation of methanol-to-propylene catalyst has been established through supporting nano-gold on ZSM-5, which efficiently reinforces the catalytic stability due to the effect of gold nanoparticles on the stabilization of dehydrogenation intermediates within the coking process.     

Formation of methyl platinum complex in the reaction of methane with chloroplatinic acid

The¹HNMR method and chemical analysis indicate that a complex of Pt(IV) containing a CH₃–Pt fragment is formed in the reaction of H₂PtCl₆+H₂PtCl₄ with methane at 120 °C in aqueous CF₃CO₂H. The complex was isolated from the solution as an adduct of Ph₃P.

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, H₂PtCl₆ H₂PtCl₄ CF₃COOH 120°C (IV), Pt–CH₃. Ph₃P , .

     

A novel montmorillonite-enwrapped scandium as a heterogeneous catalyst for Michael reaction

Treatment of a Na+-exchanged montmorillonite with an aqueous Sc(OTf)3 solution afforded a robust Sc3+ aqua complex enwrapped by the silicate layers of the montmorillonites (Sc3+-mont). The resulting Sc3+-mont showed outstanding catalytic activities for the Michael reaction of 1,3-dicarbonyls under aqueous and solvent-free conditions. Moreover, this heterogeneous catalyst had an advantage of a strikingly simple workup procedure over the Lewis acids reported to date and was reusable without any appreciable losses in its activity and selectivity.     

Influence of a Fe/activated carbon catalyst and reaction parameters on methane decomposition during the synthesis of carbon nanotubes

In our experimental work on carbon nanotubes synthesis, the influence of pre-treatment and reaction temperature conditions over Fe catalyst loaded on low-cost activated carbon (AC) in the catalytic chemical vapor deposition of methane was studied. Catalyst with the metal concentration of 5 mass % calcined at 350°C and reduced at 450°C was effective in CH₄ decomposition giving 98 % conversions. TEM images showed that thin multi-walled carbon nanotubes (MWNTs) with the average internal diameter of ∼ 8 nm and the wall thickness of ∼ 2.5 nm were obtained over unreduced Fe/AC catalyst at the reaction temperature of 850°C. On the other hand, broader filamentous nanostructures with the diameter of ∼ 22 nm and the wall thickness of ∼ 3.72 nm were observed over reduced catalyst.     

Influences of reaction conditions on methane decomposition over non-supported Ni catalyst

Effects of reaction temperature and methane gas hourly space velocity (GHSV) on methane decomposition over non-supported Ni catalyst have been investigated in this work.Methane molecules activation,Ni particles growth and nano-carbon diffusion were the main factors influencing methane decomposition stability of non-supported Ni.The results of methane decomposition activity test on the non-supported Ni catalyst showed that the prepared non-supported Ni could exhibit a good methane decomposition performance with 273 gC/gNi and 2667 molH2/molNi at 500 -C and 45000 mL/(gcat h).Scanning electron microscope (SEM),X-ray powder diffraction (XRD) and temperature-programmed oxi- dation (TPO) have been carried out to characterize the used catalysts.The deposited carbon was carbon nanofibers,among which graphitic carbon formation increased with the reaction time of methane decomposition.Ni particle size was not the decisive factor during the carbon growing stage.     

In situ DRIFT study of nonoxidative methane reaction on Mo/SnO2 catalyst

A kinetic study of the homogeneous catalytic hydrogenation of avermectins is reported for a series of isosteric p-substituted arylphosphines as ligands. The activity of the rhodium complexes formed in situ from [RhCl(COD)]₂ increased with increasing the electron-donor capacity of the P(p-XC₆H₄)₃: P(p-ClC₆H₄)₃ < P(C₆H₅)₃ < P(p-CH₃C₆H₄)₃ < P(p-OCH₃C₆H₄)₃. As expected, this trend was also observed when using preformed complexes thereof. Linear correlations based on Hammett and Kabachnik treatments are provided as useful tools to guide the exploration work towards improved [RhCl(COD)]₂/P(p-XC₆H₄)₃ catalytic systems.     

The heterogeneous catalytic oxidation of propylene in the presence of singlet oxygen in the reaction mixture

Three methods for the introduction of singlet oxygen into the reaction mixture were tested, including thermal generation of singlet oxygen on the catalyst itself, the introduction of singlet oxygen from an external source, and photogeneration of singlet oxygen on the catalyst. Zeolites with admixtures of Mo, Bi, V, and Ni and SiO₂ with deposited Mo, V, and Bi were used. Common to all reactions was an increase in the yield of deep oxidation products in the presence of singlet oxygen. A sharp increase in the yield of mild oxidation products was observed in the oxidation of propylene on a Bi/SiO₂ catalyst. The generation of singlet oxygen under irradiation at 240–260 nm was found to cause deep oxidation only. Mild oxidation products could only form under the action of total mercury lamp light.     

A 13CO isotopic study on the CO promotion effect in methane dehydroaromatization reaction over a Mo/HMCM-49 catalyst

The promotion effect of CO in methane dehydroaromatization was investigated using 13CO probe molecules. By alternative injection of 13CO to the methane feed,the distribution of 13CxC6-xH6(x=0-3)products changed significantly,confirming the participation of13CO in the reaction network.The addition of 13CO did not change the conversion of CH4 but improved slightly the durability of the methane dehydroaromatization(MDA)reaction,which might be caused by the interaction of the dissociated oxygen species and the ...     

Effect of alumina in multicomponent bismuth phosphate catalyst supported on silica-alumina for propylene ammoxidation reaction

The effect of compositions of silica-alumina support on multicomponent bismuth phosphate catalyst (MBP) was investigated for the propylene ammoxidation. It is appears that small amounts of Al₂O₃ cause retardation of the ammoxidation reaction, which would be due to activation of the selective oxidation pathway. It is understood from such results that the catalytic action of the MBP is essentially different with that of the multicomponent bismuth molybdate catalyst (MBM), which is generally used as propylene ammoxidation catalyst. This revised version was published online in June 2006 with corrections to the Cover Date.     

乙炔、丙烯在多种分子筛上的吸附和脱附性质

在80℃下研究了ZSM5、13X、Y、MOR、5A、SAPO34等多种分子筛和常见载体上乙炔和丙烯的吸附和脱附性能。结果表明,乙炔和丙烯在SiO2、γ-Al2O3上不吸附,而与分子筛存在较强的相互作用。对于同类型的分子筛,两者的饱和吸附量均随分子筛硅铝比的增大而减小。在同一种分子筛上,以摩尔计的丙烯吸附量均明显高于乙炔。在80℃改性β分子筛上乙炔和丙烯饱和吸附量可分别达到0.11mmol/g和4.89mmol/g,该结果明显高于文献报道的结果。     

Pd@GO/Fe3O4/PAA/DCA: a novel magnetic heterogeneous catalyst for promoting the Sonogashira cross-coupling reaction

Abstract

A hybrid system involving graphene oxide (GO), magnetic oxide (Fe₃O₄), acrylamide and dicyandiamide was prepared via amine functionalization of GO/Fe₃O₄ by means of covalent bonding with acrylamide and subsequent reaction with dicyandiamide to provide a multinitrogen containing polymer on the surface of GO. This hybrid system was utilized as a heterogeneous catalyst support for immobilizing Pd nanoparticles to provide the hybrid, Pd@GO/Fe₃O₄/PAA/DCA. This nano-Pd composite was characterized using Fourier transform infrared, transmission electron microscopy, scanning electron microscopy, vibrating sample magnetometer, thermogravimetric analysis, X-ray diffraction, and ICP techniques and used for promoting Sonogashira cross-coupling under mild reaction conditions. This heterogeneous and magnetic catalyst was easily separated by external magnet and was reused in a model reaction, efficiently up to six times with slight loss of catalytic activity and Pd leaching, showing the suitability of GO/Fe₃O₄/PAA/DCA for embedding Pd nanoparticles. To check the effect of the number of surface nitrogens of the polymeric chain on the catalytic performance, the activity of the catalyst was compared with Pd@GO/Fe₃O₄/PAA; increased number of the surface nitrogens on the chain polymer leads to higher loading of Pd and lower the Pd leaching.     

Copolymerization of propylene with acrylate by a Ziegler-Natta type catalyst

Propylene was polymerized by using a Ziegler-Natta type catalyst in the presence of ethylchloroaluminum acrylate, which was formed by the reaction of diethylaluminum chloride with acrylic acid. The polymer obtained contained acrylic units which were proved to be copolymerized with propylene units by solvent extraction, infrared spectrum, and NMR spectrum. The copolymer showed much improved properties compared with the polypropylene homopolymer.     

The reaction of the hydroxyl radical with acetylene

The reaction of OH with acetylene was studied in a discharge flow system at room temperature. OH was generated by the reaction of atomic hydrogen with NO₂ and was monitored throughout the reaction using ESR spectroscopy. Mass-spectrometric analysis of the reaction products yielded the following results: (1) less than 3 molecules of OH were consumed, and less than 2 molecules of H₂O were formed for every molecule of acetylene that reacted; (2) CO was identified as the major carbon-containing product; (3) NO, formed in the generation of OH, reacted with a reaction intermediate to give among other products N₂O. These observations placed severe limitations on the choice of a reaction mechanism. A mechanism containing the reaction OH + C₂H₂ → HC₂O + H₂ better accounted for the experimental results than one involving the abstraction reaction OH + C₂H₂ → C₂H + H₂O. The rate constant for the initial reaction was measured as 1.9 ± 0.6 × 10^?13 cm³ molecule^?1 sec^?1.     

Liquid-phase hydrogenation of acetylene on the Pd/sibunit catalyst in the presence of carbon monoxide

The liquid-phase catalytic hydrogenation of acetylene into ethylene in the presence of CO over palladium supported on the graphite-like material Sibunit has been investigated. Carbon monoxide is an effective modifier of the selective hydrogenation process, exerting its effect by competing with acetylene and ethylene for chemisorption sites on the palladium surface. Under the optimum conditions (T = 90°C; N-methylpyrrolidone solvent; feed consisting of 2 vol % C₂H₂, 90 vol % H₂, and He balance), the introduction of 2 vol % CO ensures a high ethylene selectivity of 89.6 ± 1.5% at an acetylene conversion of 95.8 ± 1.3%, with the acetylene converted into hydrooligomers taken into account.