One-step vapor-phase synthesis of 2-methyl-1-naphthol from 1-tetralone

A one-step reaction scheme is proposed for prepn. of 2-methyl-1-naphthol from 1-tetralone. The process includes two fixed-bed reactors in line or a single reactor with a double-layered or mixed catalytic bed. The main advantage of the proposed scheme is to avoid the intermediate sepn. and purifn. steps. [on SciFinder (R)

Zeolite/sintered metal fibers composites as effective structured catalysts

The catalytic filters of sintered metal fibers (SMF) coated by thin MFI-type zeolite (silicalite-1, ZSM-5) films have been synthesized and tested in the reactor with structured catalytic bed. The catalysts show multifunctional behavior, combining catalysis with heat exchange, mixing, and particulates removal. The reactors based on the zeolite/SMF composite elements have a three-level structure: (i) a micro-scale due to oriented submicron zeolite crystals; (ii) a meso-scale due to homogeneous porosity of metal fiber filters; (iii) a macro-scale due to the design characteristics of the catalyst packing. The catalytic bed of the FeZSM-5/SMFFecralloy was efficient and the one-step benzene hydroxylation to phenol with N2O at temperatures as low as 270 °C without loosing N2O via decomposition to nitrogen and oxygen (selectivity close to 100%). The catalyst was effective in the N2O decomposition at temperatures 400–500 °C

Highly Selective Catalytic Reduction of Nitro- to Azoarenes under Ambient Conditions

Catalytic system of Au nanoparticles supported on metal oxides has been developed to produce azoarenes in one-step directly from nitroarenes under mild conditions (30°C, 1bar of N2) using 2-propanol as solvent and reducing agent. Close to 100% chemoselectivity to substituted azoarenes with different functional groups left intact and close to quantitative yields make this procedure promising for the production of azoarenes

Dehydrogenation of Formic Acid over a Homogeneous Ru-TPPTS Catalyst: Unwanted CO Production and Its Successful Removal by PROX

Formic acid (FA) is considered as a potential durable energy carrier. It contains ~4.4 wt % of hydrogen (or 53 g/L) which can be catalytically released and converted to electricity using a proton exchange membrane (PEM) fuel cell. Although various catalysts have been reported to be very selective towards FA dehydrogenation (resulting in H2 and CO2), a side-production of CO and H2O (FA dehydration) should also be considered, because most PEM hydrogen fuel cells are poisoned by CO. In this research, a highly active aqueous catalytic system containing Ru(III) chloride and meta-trisulfonated triphenylphosphine (mTPPTS) as a ligand was applied for FA dehydrogenation in a continuous mode. CO concentration (8–70 ppm) in the resulting H2 + CO2 gas stream was measured using a wide range of reactor operating conditions. The CO concentration was found to be independent on the reactor temperature but increased with increasing FA feed. It was concluded that unwanted CO concentration in the H2 + CO2 gas stream was dependent on the current FA concentration in the reactor which was in turn dependent on the reaction design. Next, preferential oxidation (PROX) on a Pt/Al2O3 catalyst was applied to remove CO traces from the H2 + CO2 stream. It was demonstrated that CO concentration in the stream could be reduced to a level tolerable for PEM fuel cells (~3 ppm)

Highly dispersed gold on activated carbon fibers for low temperature CO oxidation

Gold nanoparticles of 2–5 nm supported on woven fabrics of activated carbon fibers (ACF) were effective during CO oxidation at room temperature. To obtain a high metal dispersion, Au was deposited on ACF from aqueous solution of ethylenediamine complex [Au(en)2]Cl3 via ion exchange with protons of surface functional groups. The temperature-programmed decomposition method showed the presence of two main types of functional groups on the ACF surface: the first type was associated with carboxylic groups easily decomposing to CO2 and the second one corresponded to more stable phenolic groups decomposing to CO. The concentration and the nature of surface functional groups was controlled using HNO3 pretreatment followed by either calcination in He (300–1273 K) or by iron oxide deposition. The phenolic groups are able to attach Au3+ ions, leading to the formation of small Au nanoparticles (9 nm) Au agglomerates after reduction by H2. These catalysts demonstrated lower activity as compared to the ones containing mostly small Au nanoparticles. Complete removal of surface functional groups rendered an inert support that would not interact with the Au precursor. The oxidation state of gold in the Au/ACF catalysts was controlled by X-ray photoelectron spectroscopy before and after the reduction in H2. The high-temperature reduction in H2 (673–773 K) was necessary to activate the catalyst, indicating that metallic gold nanoparticles are active during catalytic CO oxidation

Pd/SiO2 catalysts: synthesis of Pd nanoparticles with the controlled size in mesoporous silicas

Synthesis of Pd nanoparticles with controlled size (d(Pd) = 1-3.6 nm) was carried out within the pores of the mesoporous HMS and SBA-15 silicas. Pd was ion-exchanged on non-calcined silicas, prepared by solvent extraction of the templates. A high concentration of silanol groups on the mesopore surface allowed attaining Pd loading up to 4.4. wt.%. The Pd/HMS and Pd/SBA-15 were characterised by chemical analysis, XRD, N2 adsorption-desorption and transmission electron microscopy (TEM) methods. The materials possess a high SSA and narrow pore size distribution. Introduction of Pd nanoparticles in HMS resulted in a progressive loss of the regularity in the mesoporous structure. On the contrary, all Pd/SBA-15 composites retained the original well-ordered 2D hexagonal structure of SBA-15. The thick walls of the SBA-15 framework are accounted for the higher stability observed. The TEM investigations confirmed that the Pd nanocrystals were located within the SBA-15 mesoporous framework channels. The particle size did not exceed the mesopore diameter (2-6 nm) at Pd loading of 0.1-4.4wt.%. Pd clusters were found to be resistant against sintering during air-calcination (550 degreesC, 4h). The catalyst 2.1%Pd/SBA-15 used in methane combustion at 520 degreesC demonstrated stable activity during 6h on stream

Activated carbon fibers modified by metal oxide as effective structured adsorbents for acetaldehyde

Novel efficient adsorbents for acetaldehyde removal from diluted gas streams (similar to 1300 ppmv) have been developed. The adsorbents combine the properties of activated carbon fibers (ACF) and nanoparticles (NPs) of basic metal oxides (La2O3, CaO, MgO, ZnO, Al2O3). The adsorbents have been prepared by wetness impregnation of ACF using different precursors. The NPs are well dispersed and have average particle size below 2 nm. The ACFs-based adsorbents have an open regular macrostructure with low resistance to gas-flow (low pressure drop) and allow fast adsorption without any diffusion resistance. The NPs deposition provides up to 10-fold increase of acetaldehyde amount adsorbed as compared to non-modified ACF. The adsorption capacity increased with the basicity of metal oxides attaining 20 wt.% on La2O3/ACF. The materials are characterized by different techniques including temperature-programmed desorption (TPD) and high resolution scanning transmission electron microscopy (HRSTEM). (C) 2015 Elsevier B.V. All rights reserved