1,721,059 research outputs found
CuO based catalysts on modified acidic silica supports tested in the de-NOx reduction
No full textA series of dispersed CuO catalysts supported on modified silica supports with Al2O3 (SA), TiO2 (ST), and ZrO2 (SZ) were prepared optimising the adsorption method of copper deposition assisted by ultrasound treatment, already reported in a previous paper (S. Bennici, A. Gervasini, V. Ragaini, Ultrason. Sonochem. 10 (2003) 61). The obtained catalysts were characterized in their bulk (atomic absorption, x-ray diffraction, temperature programmed reduction) and surface (N2 adsorption, x-ray photoelectron spectroscopy, scanning electron microscopy) properties. The morphology of the finished materials was not deeply modified compared with that of the relevant supports. The employed complemented techniques evidenced a well dispersed CuO phase with a copper-support interaction on the most acidic supports (SA and SZ).
The catalyst performances were studied in the reaction of selective catalytic reduction of NOx with ethene in oxidizing atmosphere in a flow apparatus under variable times (0.360-0.072 s) and temperatures (200-450°C). The catalysts prepared on the most acidic supports (SA and SZ) were the most active and selective towards N2 formation. They showed a particular interesting activity in the reaction of NO2 reduction besides that of NO reduction
Catalytic technology assisted with ionization/ozonization phase for the abatement of Volatile Organic Compounds
No full textThe catalytic combustion process of air-mixtures containing volatile organic compounds (VOCs) associated with an ionization/ozonization reactor (IOCC technique, ionization-ozonization-catalytic-combustion) has been utilized for the abatement of two very toxic industrial VOCs: acrylonitrile (ACN) and vinyl chloride (VCM). The pre-catalytic effects (electric discharge plus the action of ozone), the conventional and IOCC combustion tests were studied. Two different catalysts were used: oxide catalyst, copper-chromite (Cu-Cr), and Pt metal catalyst (0.5 wt.% Pt/γ-Al2O3). The abatement of ACN was markedly influenced by the pre-catalytic effects. Starting from 3 kV, an increasing abatement of ACN was observed with the voltage applied to the ionization reactor at any initial ACN concentration (500-1500 ppm). The ACN catalytic combustion, performed by the IOCC technique, led to 91 and 98% yield of CO2 on Cu-Cr and Pt catalysts, respectively, at 260°C. Complete absence of hazardous intermediates, such as hydrogen cyanide, was observed. The Cu-Cr catalyst, at 300°C, was able to abate 57 and 23% of VCM at 10 000 and 20 000 h-1, respectively. IOCC combustion led to improved conversion. At 200°C and 3300 h-1, 98% and only 49% of VCM abatement operating according to IOCC and classical combustion was obtained, respectively. The IOCC combustion runs, performed at different initial VCM concentrations (585 and 1170 ppm), indicated a superior abatement when low VCM concentration was fed, at a given catalyst temperature and contact time. This indicated a marked influence of the pre-catalytic effects on the abatement
Co/SiO2 for Fischer-Tropsch Synthesis: comparison among different preparation methods
No full textAn extensive sludy of different preparation methods for Co/SiO2 catalysis is reported in the present paper. In addition to the conventional impregnation, other more innovative methods are tested together with the sol-gel process, methods involving the use of ultrasound and of particular metal precursors or solvents. The prepared samples are fully characterized and tested in the CO hydrogenation
Choosing the best diluent for a fixed catalytic bed : The case of CO hydrogenation
Full text linkFixed bed reactors are frequently used for many catalytic reactions, but the difficult to remove the reaction heat in highly exothermic
reactions can bring to a bad performance of the catalyst or to its fast deactivation. A possible solution is to use diluents, i.e., inactive
ceramic bodies, tailored to mix intimately with the catalyst without affecting the fluid flow through the catalyst bed. The influence of the
use of diluent materials on Fischer–Tropsch synthesis catalyst activity is here fully discussed
The beneficial influence of ultrasound in the polymerization of ε-caprolactam to polyamide-6 (Nylon 6). Part I: Primary experimental results
No full textε-caprolactam (CL) polymerization to polyamide-6 (Nylon 6) was studied at different contents of water in CL (0.01-2 wt%), with or without ε-amino-caproic acid (ACA) as an activator, applying to the mixture an initial treatment of Ultrasound (US) (17.5-20 kHz) at low temperatures (70-110 °C) and for short times (max 10 min). It was verified that polymerization at 260 °C produces a polymer having a much higher molecular weight (MW) when US is applied with respect to silent (SIL) conditions i.e. without the use of ultrasound. This constitutes a "pre-sonication effect". The ratio (MW)US/(MW)SIL is inversely proportional to the initial content of water in CL. The action of US converts CL at very low temperatures (70-110 °C) and water content, in comparison with silent conditions where CL was unconverted. Optimized conditions are studied with respect to nature and pressure of gas inside the reactor, temperature, time and frequency of US irradiation, energy consumption and nature of activator
VOC Removal by synergic effect of combustion catalyst and ozone
No full textThe synergic effects of the combustion catalyst Ba-CuO-Cr2O3/Al2O3 and ozone, used as strong oxidant species in the combustion of various VOCs, were studied. The experiments were performed with five different methods by feeding the organics with air (1000 ppmV) before (methods 2 and 4) and after the ozone generator (methods 1, 3 and 5), they entered into the catalytic reactor (methods 1, 2 and 3) or were directly analyzed (methods 4 and 5). The concentration profiles of the organics were compared as a function of the reaction temperature (from 100 to 500°C) for the methods 1, 2 and 3 and as a function of the peak voltage of the ozone generator (2-10 kV), that is the ozone concentration (up to 2000 ppm) for methods 4 and 5. Ozone strongly reacted in the gas phase with aromatic molecules and organics having functional groups. Moreover, a positive ionizing effect produced by the corona discharge in the ozone generator on the destruction of the organics was found too
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