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kinetic model of the glycerol oxidation by using a silver-based catalyst
Authors
M. Capron
N. Diaz
+4 more
F. Dumeignil
P. Fongarland
J.-S. Girardon
S. Zaid
Publication date
27 September 2015
Publisher
HAL CCSD
Abstract
SSCI-VIDE+CDFA+DLJ:PFOInternational audienceThe depletion of fossil fuels has led to the development of alternative and environmentally-friendly energy carriers, such as biodiesel. The manufacture of biodiesel leads to glycerol (GLY) as the main by-product (10 wt.%), so that its valorization has become an important issue. GLY is a versatile polyol which can be used as a bio-building block of different add-value products.There are many GLY transformation pathways, and among them the oxidation in the liquid phase has gained a great interest. So far, Pt, Pd and Au have been used as active phases in this reaction. These metals are selective towards the formation of glyceric acid in basic media. On the other hand, the use of Ag in this reaction has been seldom studied. This metal has been proven to be selective to glycolic acid [1], which is used in food, cosmetics and textile industries.The aim of this work is to develop a kinetic model of the GLY oxidation in the liquid phase, by using the experimental results obtained with an Ag/CeO2 catalyst. The effect of the reaction temperature and NaOH concentration was taken into account. Moreover, experimental results revealed that the catalyst was somehow deactivated, so that thedeactivation kinetics has also been included in the proposed model.First of all, the reaction pathways were deduced from the experimental data. Only glyceric, glycolic and formic acid were observed as primary products, as observed in Figure 1. A power-law kinetic model was proposed, by considering first order reaction of all components and a carbon balance close to 100%. Deactivation kinetics was considered first-order ofactivity and zero-order of the species concentration. Parameter fitting was carried out by using Matlab.The parity plot and results of the parameter fitting, (Figure 2), revealed that the proposed kinetic model predicted well the experimental concentrations, whereas the fitted parameters were statistically significant. The obtained activation energies were practically the same for all reactions. However, reaction 2 displayed the highest k value at the referencetemperature, which confirmed the high selectivity of the Ag-based catalyst towards glycolic and formic acids. As for deactivation kinetic parameters, results revealed that the catalyst deactivation was significant, whereas the high activation energy suggested a strong dependence on the reaction temperature. Future work will be focused on two points: to develop a heterogeneous Langmuir-Hinshelwood model and to compare different deactivation kinetics.This work has been performed, in partnership with the SAS PIVERT, within the frame of the French Institute for the Energy Transition (Institut pour la Transition Energétique (ITE) P.I.V.E.R.T. www.institut-pivert.com) selected as an Investments for the Future (âInvestissements dâAvenirâ). This work was supported, as part of the Investments for the Future, by the French Government under the reference ANR-001-01
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Last time updated on 14/04/2021