9 to 45 h2he a calibration curve was fitted to the

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Unformatted text preview: behaviour in He, which was used as carrier gas, for the calibration of the H2 response signal 18 points were used ranging from 3.9 to 45% H2/He. A calibration curve was fitted to the experimental points by a polynomial function of the 6th degree using Microsoft Excel software. 2.8.2. Procedure The performance of the catalysts was tested in a standardised procedure to ensure to reproducibility and the comparability of the results. In each catalytic test 5 mg of catalyst were placed on a quartz wool bed in the quartz reactor. The catalyst was heated up to the reduction temperature in a flow of 40 ml/min He. This way adsorbed compounds like water and CO2 were desorbed prior to the reduction. The reduction of the catalysts was performed in-situ prior to the reaction at the desired temperature in a flow 40 ml/min of pure H2 for two hours. This rather high flow was used to ensure constantly high partial pressure of H2 and to remove any H2O formed during the reduction, which has been reported to be beneficial [59]. The reduction was started after the temperature was constant for at least 5 min. H2 was added and the He flow ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffyfffffffffffffffffffffffffffffffffffffffff 2. Experimental 65 fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff switched off after the H2 flow was stable. Changes in the temperature at the beginning of the reduction were compensated by changes of the heating power of the temperature controller. After 2 hours of reduction a flow of 40 ml He was added and the H2 flow switched off as soon as the He flow was stable. The reactor was purged with He and the temperature adjusted to the desired reaction temperature in the flow of He. The catalytic test was carried out by continuously passing the gaseous reaction mixture consisting of He, C3H8 and O2 over the catalyst. In order to avoid any oxidation of the catalyst...
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This document was uploaded on 10/07/2013.

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