Performance of palladium-containing supported catalysts in the oxidation of 1-butene

Performance of palladium-containing supported catalysts in the oxidation of 1-butene was investigated in a fixed-bed flow microreactor. The Pd-Fe-HCl/Ti-Al catalyst is the best among the five Pd-Fe-HCl/X (A = SiO2, gamma-Al2O3, Al-Ti, TiO2, MCM-22) catalysts for the oxidation of I-butene to butanone. It is interesting that high propionic acid selectivity can be obtained when V and H2SO4 are added to the palladium-containing supported catalysts.

Total oxidation of naphthalene using palladium nanoparticles supported on BETA, ZSM-5, SAPO-5 and alumina powders

A range of catalysts based on Pd nanoparticles supported on inorganic supports such as BETA and ZSM-5 zeolites, a silicoaluminophosphate molecular sieve (SAPO-5) and γ-alumina as a standard support have been tested for the total oxidation of naphthalene (100 ppm, total flow 50 ml/min) showing a conversion to carbon dioxide of 100% between 165 and 180 °C for all the analysed catalysts. From the combined use of zeolites with PVP polymer protected Pd based nanoparticles, enhanced properties have been found for the total abatement of naphthalene in contrast with other kinds of catalysts. A Pd/BETA catalyst has been demonstrated to have excellent activity, with a high degree of stability, as shown by time on line experiments maintaining 100% conversion to CO2 during the 48 h tested.

Total oxidation of naphthalene at low temperatures using palladium nanoparticles supported on inorganic oxide-coated cordierite honeycomb monoliths

A study on the preparation of thin films of ZSM-5 and BETA zeolites, and a SAPO-5 silicoaluminophosphate, supported on cordierite honeycomb monoliths by in situ synthesis was carried out for their use as catalyst supports. Furthermore γ-Al2O3 was also coated onto a cordierite honeycomb monolith by a dip-coating method for use as a standard support. Structured monolithic catalysts were prepared by impregnation of the aforementioned coated monoliths with polymer-protected Pd nanoparticles. The monolithic catalysts have been tested for the total oxidation of naphthalene (100 ppm, GHSV 1220 h−1). From the combined use of the zeolite with polymer-protected nanoparticles, enhanced catalytic properties have been found for the total abatement of naphthalene. The Pd/MBETA and Pd/MZSM-5 catalytic monoliths have shown excellent activity with a high degree of stability, even after undergoing accelerated ageing experiments.

Carbon dioxide reforming of methane to produce synthesis gas over metal-supported catalysts: State of the art

Carbon dioxide reforming of methane produces synthesis gas with a low hydrogen to carbon monoxide ratio, which is desirable for many industrial synthesis processes. This reaction also has very important environmental implications since both methane and carbon dioxide contribute to the greenhouse effect. Converting these gases into a valuable feedstock may significantly reduce the atmospheric emissions of CO2 and CH4. In this paper, we present a comprehensive review on the thermodynamics, catalyst selection and activity, reaction mechanism, and kinetics of this important reaction. Recently, research has centered on the development of catalysts and the feasible applications of this reaction in industry. Group VIII metals supported on oxides are found to be effective for this reason. However, carbon deposition causing catalyst deactivation is the major problem inhibiting the industrial application of the CO2/CH4 reaction. Ni-based catalysts impregnated on certain supports show carbon-free operation and thus attract much attention. To develop an effective catalyst for CO2 reforming of CH4 and accelerate the commercial application of the reaction, the following are identified to be the most important areas for future work: (1) selection of metal and support and studying the effect of their interaction on catalyst activity; (2) the effect of different promoter on catalyst activity; (3) the reaction mechanism and kinetics; and (4) pilot reactor performance and scale-up operation.

New Insights into Selective Heterogeneous Nucleation of Metal Nanoparticles on Oxides by Microwave-Assisted Reduction: Rapid Synthesis of High-Activity Supported Catalysts

Microwave-based methods are widely employed to synthesize metal nanoparticles on various substrates. However, the detailed mechanism of formation of such hybrids has not been addressed. In this paper, we describe the thermodynamic and kinetic aspects of reduction of metal salts by ethylene glycol under microwave heating conditions. On the basis of this analysis, we identify the temperatures above which the reduction of the metal salt is thermodynamically favorable and temperatures above which the rates of homogeneous nucleation of the metal and the heterogeneous nucleation of the metal on supports are favored. We delineate different conditions which favor the heterogeneous nucleation of the metal on the supports over homogeneous nucleation in the solvent medium based on the dielectric loss parameters of the solvent and the support and the metal/solvent and metal/support interfacial energies. Contrary to current understanding, we show that metal particles can be selectively formed on the substrate even under situations where the temperature of the substrate Is lower than that of the surrounding medium. The catalytic activity of the Pt/CeO(2) and Pt/TiO(2) hybrids synthesized by this method for H(2) combustion reaction shows that complete conversion is achieved at temperatures as low as 100 degrees C with Pt-CeO(2) catalyst and at 50 degrees C with Pt-TiO(2) catalyst. Our method thus opens up possibilities for rational synthesis of high-activity supported catalysts using a fast microwave-based reduction method.

Promoting effects in hydrogenation and hydrodesulfurization reactions on the zirconia and titania supported catalysts

Tetralin hydrogenation (HYD) and thiophene hydrodesulfurization (HDS) were studied for the supported MoS2 and WS2 sulfides, either non-promoted or promoted with Co and Ni. The supports used were ZrO2, alumina-stabilized TiO2 and pure alumina. Preparation of catalysts included presulfidation of non-promoted system with subsequent addition of promoter and resulfidation. It has been found that the nature of promoter plays determining role for the catalytic performance. The most active in both HYD and HDS reactions are Ni-promoted Mo and W catalysts, supported on ZrO2. (C) 2003 Published by Elsevier B.V.

Ion channel behavior of amphotericin B in sterol-free and cholesterol- or ergosterol-containing supported phosphatidylcholine bilayer model membranes investigated by electrochemistry and spectroscopy

Amphotericin B (AmB) is a popular drug frequently applied in the treatment of systemic fungal infections. In the presence of ruthenium (II) as the maker ion, the behavior of AmB to form ion channels in sterol-free and cholesterol- or ergosterol-containing supported phosphatidylcholine bilayer model membranes were studied by cyclic votammetry, AC impedance spectroscopy, and UV/visible absorbance spectroscopy. Different concentrations of AmB ranging from a molecularly dispersed to a highly aggregated state of the drug were investigated. In a fixed cholesterol or ergosterol content (5 mol %) in glassy carbon electrode-supported model membranes, our results showed that no matter what form of AmB, monomeric or aggregated, AmB could form ion channels in supported ergosterol-containing phosphatidylcholine bilayer model membranes. However, AmB could not form ion channels in its monomeric form in sterol-free and cholesterol-containing supported model membranes. On the one hand, when AmB is present as an aggregated state, it can form ion channels in cholesterol-containing supported model membranes; on the other hand, only when AmB is present as a relatively highly aggregated state can it form ion channels in sterol-free supported phosphatidylcholine bilayer model membranes. The results showed that the state of AmB played an important role in forming ion channels in sterol-free and cholesterol-containing supported phosphatidylcholine bilayer model membranes.

Synthesis of C-1 bridge-containing metallocene catalysts and their catalytic activities for olefin polymerization

The synthesis and characterization of metallocene complexes which can be used as catalysts in the presence of MAO for olefin polymerization were discussed in the present paper. The metallocene complexes have been characterized by IR, H-1 NMR, EI-MS spectra and element analyses; The catalytic features of Olefin polymerization were studied under different conditions. Metallocenes in which metals is Ti had no activity for ethylene polymerization, Polymers with different features can be obtained by using different catalysts.