The mass gain due to oxidation of reduced ni

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Unformatted text preview: s lost during the temperature programmed combustion (TPC) in air up to 1100°C in t he TG-MS a linear heating rate of 20°C/ min. The mass gain due to oxidation of reduced Ni particles, which overlapped with the combustion of the carbon deposits was taken into account by considering that all Ni particles reducible in the temperature programmed reduction were in the metallic state after the catalytic tests and oxidised to NiO during the temperature programmed combustion. The catalysts’ relative deactivation rate was measured as the relative decrease of the C3H8 conversion with time on stream divided by the time from the first to the last analysis. The relative decrease of the C3H8 conversion was calculated from the linear trend line using Microsoft Excel software. The C3H8 and O2 conversion values (X) were calculated according to: XC 3H 8 = XO 2 = FC 3H8 in - FC 3H8 out FC 3H8 in FO 2 in - FO 2 out FO 2 in 2. Experimental 67 Fi out = xi × Ftotalout where F is the flow (ml/min) measured at room temperature and atmospheric pressure and x is the volume fraction as calculated from the calibrated peak area The total outlet flow rate changed due to the reaction and was calculated from the helium balance: FHeout = FHein = 40 ml/min xHe out = 1 - å xiout i ¹He Ftotalout × xHeout = FoutHe = FHein = 40 ml / min Ftotalout = 40 ml / min 1 - å xiout i¹He Fi out = xi × Ftotalout The quantities of water formed were determined from the oxygen atom balance: FH 2 O = 2 × FO2 in - 2 × FO2 out - 2 × FCO2 out - FCO out The selectivities (S) were calculated as hydrogen selectivity for H2 and H2O and as carbon selectivity for all carbon containing products according to: 68 2. Experimental SH2 = 2 ⋅ FH2 ∑ (N Hi ⋅ Fi ) i S H 2O = 2 ⋅ FH2O ∑ (N Hi ⋅ Fi ) i S carbon containing product i = N C i ⋅ Fi ∑ (N Ci ⋅ Fi ) i where NHi is the number of hydrogen atoms of product molecule i and NCi is the number of carbon atoms of product molecule i The yield (Y) was calculated according to: Yi = X propane ⋅ Si 2.8.3. Modific...
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This document was uploaded on 10/07/2013.

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