Catalytic Preparation Research Articles

Low-temperature catalytic preparation of multi-wall MoS2 nanotubes

In the catalytic reduction atmosphere of H 2 +CH 4 +C 4 H 4 S, the ball-milled precursor (NH 4 ) 2 MoS 4 is heated to 300℃ for decomposition. The as-synthesized product is characterized by XRD, SEM, TEM, HRTEM, EDX, and BET. The results show that multi-wall MoS 2 nanotubes are obtained. The length of the nanotubes is around 3—5 μm. The diameters of the nanotubes are homogeneous, with an inner diameter of ~15 nm, an outer diameter of ~30 nm, and an interlayer (002) d -spacing of 0.63 nm. This catalytic thermal reaction occurring at low temperatures is important for the large-scale preparation of similar transition-metal disulfide nanotubes.

The influence of vanadium catalyst preparation method on butadiene polymerization

The butadiene polymerization in toluene at 25°C using a VOCl3–Al(iso-C4H9)3 catalytic system was studied. The maximum of activity corresponded to the ratio . The polymer contained 90% 1,4-trans- and 10% 1,2-units. The kinetic parameters of polymerization and molecular characteristics of polybutadiene were determined, and they testify to the influence of catalytic complex preparation and polymerization conditions on them. It was suggested that there are several types of active centers that differ in activity, stereospecificity of action, and stability.

Relationship between the stereospecificity of lanthanide catalysts and the structures of active sites and dienes, the nature of a cocatalyst, and preparation conditions

Several types of active sites can be formed during the polymerization of dienes in the presence of lanthanide catalytic systems. These sites differ in the nearest environment of a lanthanide atom (the numbers of chlorine and carbon atoms) and in the number of lanthanide–carbon bonds involved in chain growth. Quantum-chemical calculation shows that the π-allyl binding of the terminal unit of a growing polymeric chain with the lanthanide atom of an active site may be the reason for the cis-stereospecificity of the site. Therefore, the active sites containing electron-acceptor chlorine atoms that favor π-allyl binding can form cis-polydienes. Depending on the conditions of catalytic system preparation, primarily on the nature of an organic compound of a nontransition metal, one or another set of active sites is formed that can affect its stereospecificity. The quantitative analysis of kinetic data for diene polymerization shows that the anti-synisomerization of terminal units of growing polymeric chains made a certain contribution to the formation of trans-1,4 units in the presence of cis-regulating active sites.

2H-Chromenes from salicylaldehydes by a catalytic petasis reaction

The Petasis condensation of vinylic or aromatic boronic acids, aromatic aldehydes, and amines is assisted by a hydroxy group adjacent to the aldehyde moiety. The products derived from salicylaldehydes and vinylboronic acids undergo cyclization to 2H-chromene compounds with ejection of amine upon heating. A catalytic preparation of 2H-chromenes using resin-bound amine is reported, allowing the convenient incorporation of a variety of components.

Catalytic Preparation of Non-Symmetrical Ketones in the Gas Phase Over Iron Oxide

The catalytic conversion of esters and mixtures of alcohols and aldehydes in the gas phase over iron oxide has been studied. The method allows for effective synthesis of non-symmetrical ketones.

ChemInform Abstract: Catalytic Preparation of Aziridines with an Iron Lewis Acid.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Alkoxylation reaction catalysed by layered double hydroxides

Layered double hydroxides (LDHs) are extensively studied as precursors for catalysts, following a calcination at high temperatures to yield mixed oxides. However, these materials are less used as layered materials, i.e., without undergoing thermal activation. We have focused in this work on the use of a series of as-synthesised LDHs for the catalytic preparation of glycol ethers, which is a reaction of primary commercial importance. Two main systems are considered, namely the [Cu–Cr] and [Mg–Al] LDHs. The [Cu–Cr–Cl] LDH is obtained by the coprecipitation method, then through the appropriate chimie douce exchange reactions the original chloride anions are replaced by a variety of oxo- and polyoxometallates, (CrO 4) 2−, (Cr 2O 7) 2−, (V 2O 7) 2−, (V 10O 28) 6− and (Mo 7O 24) 6−. On the other hand, the [Mg–Al] hydrotalcites, intercalated by (V 2O 7) 2−, (V 10O 28) 6− and [Fe III(CN) 6] 3− anions, are obtained by structure regeneration. This was done by rehydration of a commercial calcined material (Kyowa) in aqueous solutions containing the desired anion. The different materials have been fully characterised by conventional analytical techniques to evidence their lamellar properties and chemical nature. They were then tested in the catalytic reaction involving butan-1-ol and one or more units of ethylene oxide to make butyl-monoglycol ether (BMGE), di-glycol ether (BDGE), tri-glycol ether (BTGE), etc. The reactions were carried out between 80 and 120°C, temperature range in which no collapse of the lamellar structure is normally observed. In this paper it is shown that decavanadate exchanged LDHs proved to be very selective catalysts for the preparation of the monoglycol adduct, some samples achieving up to 100% selectivity in the screening tests.

Catalytic Preparation of Aziridines with an Iron Lewis Acid.

The iron Lewis acid, [(eta(5)-C(5)H(5))Fe(CO)(2)(THF)](+)[BF(4)](-), was found to be an effective catalyst for the preparation of aziridines. This new method provides a facile, one-step route to predominantly cis-aziridines, with yields up to 95%, from compounds with a diazo functionality and a variety of substituted N-benzylidene imines with N-aryl or N-alkyl groups. The reaction mechanism is believed to proceed through an electrophilic iminium ion intermediate. To support this idea, the iron Lewis acid-imine complex [(eta(5)-C(5)H(5))Fe(CO)(2)(PhCH=NPh)](+)[BF(4)](-) was prepared, characterized, and reacted with different diazo compounds to provide the resultant cis-aziridines. Alternatively, it may be possible that the aziridines were derived from an electrophilic carbenoid intermediate, as is often proposed. Thus, the iron carbene [(eta(5)-C(5)H(5))Fe(CO)(2)(CHPh)](+)[SO(3)CF(3)](-) was prepared and treated with N-benzylideneaniline; however, the resultant aziridine was not formed.

Catalytic Preparation and Characterization of C60Br24

In this paper the procedure for catalytical bromination of C60 with elementary bromine with FeBr3 as a catalyst is described. In this procedures only one reaction product - C60 Br24 is obtained. The twenty four bromine atoms are symmetrically distributed over the C60 sphere, which was confirmed by thermogravimetric analysis. The yield of bromine derivative in this reaction is 98%.

Catalytic preparation of narrow pore size distribution mesoporous carbon

The carbon deposited during the catalytic decomposition of CH 4 over Ni, Co or Fe particles, at temperatures between 500 and 780 °C, was investigated by N 2 adsorption, TEM and XPS. A much larger amount of carbon was formed on Ni than on Co or Fe. The pore size distribution curves indicate that the carbon deposited on the three metals has most of the pores in the 3–4 nm range. The proportion of pores in that range decreases on Ni, but increases on Co or Fe with reaction time. During the CH 4 decomposition over Ni at 500 °C, two kinds of carbon were identified: 1) nanotube carbon (with the smallest inner diameter of about 3 nm) and 2) mesoporous carbon. At high temperatures, almost only the mesoporous carbon with a narrow pore size distribution around 3.5 nm could be observed. It is likely that the nanotubes are the precursors of the mesoporous carbon, because the inner diameter of the smaller ones is almost equal to the size of the pores, and the nanotubes are no longer present at high temperatures.

5585496 Catalytic preparation of condensation products of formaldehyde: Teles Joaquim H; Melder Johann-Peter; Gehrer Eugen; Harder Wolfgang; Ebel Klaus; Groening Carsten; Meyer Regina Ludwigshafen, Germany assigned to Basf Aktiengesellschaft

5585496 Catalytic preparation of condensation products of formaldehyde: Teles Joaquim H; Melder Johann-Peter; Gehrer Eugen; Harder Wolfgang; Ebel Klaus; Groening Carsten; Meyer Regina Ludwigshafen, Germany assigned to Basf Aktiengesellschaft

Phase Transfer Catalytic Preparation of p-Chlorophenoxy Acetic Acid

Phase Transfer Catalytic Preparation of p-Chlorophenoxy Acetic Acid

Catalytic preparation of mesityl oxide from acetone

In the process of the aldol condensation of acetone the preparation of mesityl oxide has been studied with respect to the temperature and the nature of catalyst. Strong basic ion exchangers Ionenaustauscher III (Merck III) and Lewatit MP 500 were used in the temperature range from 0 to 50°C. Better results are achieved with Merck III, as is evident from DAA/MO yields, rate constants and energy activation values. Empirical expressions for DAA/MO production are given.

Catalytic preparation of diacetone alcohol in controlled flow conditions

Catalytic preparation of diacetone alcohol from acetone was studied using strong basic ion exchangers as catalysts. A continuous process was carried out in an enlarged laboratory set-up with controlled flow rate. Experiments were performed with respect to experiment duration, temperature, flow rate, catalyst porosity and catalyst-acetone ratio. The quantity of DAA was determined by gas chromatography. The effects of temperature, catalyst porosity and catalyst-acetone ratio on the reaction course were significant in comparison with other parameters examined. An exponential dependence of C/A ratio on DAA yield was found.

A New Way to SiC Ceramic Precursors by Catalytic Preparation of Preparation Polymers

A New Way to SiC Ceramic Precursors by Catalytic Preparation of Preparation Polymers

Specimen limitations in nanocharacterization by TEM/STEM of industrial heterogenous catalysts: In situ, irradiation damage and micro/macro correlations

Three types of problems related to nanometer-scale characterization are discussed with reference to heterogeneous catalysts. Changes occurring in air-sensitive samples, notably reoxidation of reduced metallic particles leading to flase size distributions, can be avoided by use of transfer devices and special preparation techniques. Specimen damage constitutes a greater problem and can only be overcome by degrading the available resolution. The possibility of correlating nanoanalysis with information obtained from larger-scale techniques is greatly enhanced by extending the use of ultramicrotome cross-sectioning, which can preserve positional information up to a millimeter scale, to this class of materials. The use of ultramicrotome sections has the added advantage of constant specimen thickness leading to increased dependability of X-ray analysis. An example is given of analysis of a bimetallic catalyst in comparison with electron probe microanalysis in which STEM confirms the EPMA results and provides in addition valuable particle-by-particle information relevant to catalytic preparation and performance.

ChemInform Abstract: Applications of Phase‐Transfer Catalysis. Part 38. Phase‐Transfer Catalytic Preparation of the Dipolar Aprotic Solvents DMI and DMPU.

ChemInform Abstract: Applications of Phase‐Transfer Catalysis. Part 38. Phase‐Transfer Catalytic Preparation of the Dipolar Aprotic Solvents DMI and DMPU.

Phase Transfer Catalytic Preparation of the Dipolar Aprotic Solvents DMI and DMPU

Abstract The title compounds are prepared by methylation of the respective cyclic ureas using Me2SO4/catalyst/powdered NaOH (for DMI) or K2CO3 (for DMPU). Improved procedures are communicated for the preparation of 2-imidazolidine and trimethylene urea.

The direct synthesis of triorganotin compounds: Process and reaction mechanism

AbstractThe reaction of tin metal with alkyl halides in the presence of a stoichiometric amount of halide ion rapidly produces very high yields of triorganotin halides. An overview of these reaction conditions and those required for the catalytic preparation of diorganotin dihalides shows that these preparations follow the normal reactivity of the alkyl halides towards nucleophiles. Both processes are satisfactorily explained by a mechanism involving tin halogenoanions as nucleophiles. A similar mechanism also explains the formation of organomagnesium and organozinc halides.

ChemInform Abstract: Development of a Process of the Catalytic Preparation of a Perfluoroalkyl Sulfonamide by Addition of Ethylamine to a Perfluoroalkyl Sulfonic Acid Chloride.

AbstractEs wird eine optimierte Synthese des Sulfonamids (W, das als Zwischenprodukt zur Herstellung von Verbindungen zur Hydro‐ und Oleophobierung von Papier Interesse besitzt, beschrieben.