Journal
REACTION KINETICS MECHANISMS AND CATALYSIS
Volume 119, Issue 1, Pages 179-193Publisher
SPRINGER
DOI: 10.1007/s11144-016-1032-7
Keywords
CO2 activation; Perovskite; Ni/La2O3; TGA-MS; Kinetic compensation effect
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Funding
- ECOS-Nord program [C08P01]
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The thermo-catalytic CO2 activation was studied over supported nickel catalyst (Ni/La2O3) obtained by reduction of the perovskite LaNiO3. At temperatures lower than 700 A degrees C, a superficial CO2 activation over the catalyst was observed and a partial structural change of the support to lanthanum oxycarbonate was determined by in situ XRD. The oxycarbonate species decomposed at around 750 A degrees C, regenerating the original support La2O3 and producing CO2 (determined by TGA-MS). Above 750 A degrees C, CO2 consumption accompanied by CO production and a weight increase were observed by TGA-MS. These observations suggest the oxidation of metallic nickel to NiO. The oxidation process finished at around 1180 A degrees C, the phases obtained were NiO/La2NiO4. The mechanism of oxidized species formation was proposed according to the kinetic parameters obtained by TGA-MS under CO2 atmosphere. Activation energies and pre-exponential factors were calculated for the different steps of the mechanism proposed. Additionally, a kinetic compensation effect was observed for the activation of CO2 on NiO/La2O3 catalyst. This compensation effect exhibited a slope change at around 850 A degrees C, which suggested a modification of the mechanism at this temperature.
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