Thermodynamic Control of Product Formation During the Reaction Between CH 4 and Pt Promoted Ceria-zirconia Solid Solutio
- PDF / 702,848 Bytes
- 7 Pages / 595.276 x 790.866 pts Page_size
- 29 Downloads / 164 Views
Thermodynamic Control of Product Formation During the Reaction Between CH4 and Pt Promoted Ceria-zirconia Solid Solutions Federica Mudu • Bjørnar Arstad • Helmer Fjellva˚g Unni Olsbye
•
Received: 30 June 2010 / Accepted: 20 August 2010 / Published online: 17 September 2010 Ó The Author(s) 2010. This article is published with open access at Springerlink.com
Abstract The reaction between CH4 and framework oxygen of Pt promoted CexZr1-xO2 (x = 0.25, 0.5, 0.75, 1) solid solutions was studied at 873 K for syngas (CO ? H2) production. The homogeneity and cubic/tetragonal structure of the solid solutions were confirmed by powder X-ray diffraction. The thermodynamic properties of the solid solutions, connected with Ce4?/Ce3? redox reactions, were measured by titrating the oxygen content of the oxides after equilibration in flowing mixtures of H2 and CO2 with 10-31 \ pO2 \ 10-22 atm. The transient reactions between the oxides and discrete pulses of CH4, as well as of isotopically labeled 13CH4 ? 12CO mixtures (limited to the material with x = 0.25) were investigated and reactivity, conversion and selectivity were measured. A strong correlation between the thermodynamic properties of the oxides and the syngas selectivity was found. The 13C scrambling in CO and CO2 during co-feed experiments
Electronic supplementary material The online version of this article (doi:10.1007/s10562-010-0441-x) contains supplementary material, which is available to authorized users. F. Mudu H. Fjellva˚g U. Olsbye (&) Centre of Material Science and Nanotechnology, Department of Chemistry, University of Oslo, P.O. Box 1126, Blindern, Oslo 0318, Norway e-mail: [email protected] B. Arstad SINTEF Materials and Chemistry, Forskningsveien 1, 0314 Blindern, Oslo, Norway B. Arstad H. Fjellva˚g U. Olsbye Department of Chemistry, inGAP Centre of Research-Based Innovation, University of Oslo, P.O. Box 1126, Blindern, Oslo 0318, Norway
123
confirmed equilibration of these molecules with the oxides surfaces. Keywords Cerium oxide Methane partial oxidation Degree of reduction
1 Introduction Ceria based oxides have a great potential for catalytic applications, and have during the last years been investigated for processes like water gas shift, supports for reforming catalysts, VOCs catalytic combustion, CO preferential oxidation and conversion of emission gases [1–10]. The behavior of ceria based oxides in catalysis is typically connected with the redox couple Ce4?/Ce3? and the consequent reversible oxygen storage capacity. One reaction where the reducibility of cerium oxide plays a central role is the conversion of CH4 to syngas (CO and H2) by framework oxygen (Eq. 1 below), and subsequent regeneration of the CeO2 with air (Eq. 2). This approach to methane conversion might become particularly relevant in gas to liquids (GTL) offshore units, where the direct hightemperature reaction of CH4 with O2 (or air) has technological and risk challenges. yCH4 þ MOx ¼ yCO þ 2yH2 þ MOxy
ð1Þ
1 MOxy þ yO2 ¼ MOx 2
ð2Þ
The use of cerium oxide in th
Data Loading...
