Ippolito, Davide

Dette projekt omhandler fuldstændig oxidation af propen ved brug af en porøs, keramisk, elektrokemisk reaktor. To elektrode kompositter, La0.85Sr0.15MnO3±d/Ce0.9Gd0.1O1.95 (LSM/CGO og La0.85Sr0.15FeMnO3/Ce0.9Gd0.1O1.95 (LSF/CGO), blev testet i en cellestak-konfiguration bestående af 5 enkelt-celler, som herefter benævnes ”reaktoren”. Reaktoren blev i projektet infiltreret med materialer, som påvirkede dens elektrokemiske og katalytiske aktivitet. Reaktorens aktivitet og effekten af elektrisk polarisering på propen oxidation blev målt ved hjælp af gas analyse med en gas kromatograf, analysen blev lavet både under polarisering af reaktoren og ved forskellige temperaturer. Elektrokemisk impedans spektroskopi (EIS) blev brugt til at studere, hvordan infiltrering med elektroaktive materialer påvirkede elektroderne. Både gas kromatografi og EIS blev anvendt for at klarlægge forholdet mellem reaktorens katalytiske aktivitet under polarisering og reaktorens elektrokemiske egenskaber. Effekten af de infiltrerede materialers morfologi på den elektrokatalytiske aktivitet blev vurderet ud fra scanning elektron mikroskopi. Dette projekt har bidraget til forståelsen af, hvordan effekten af polarisation på propen omsætning er en kompleks funktion af en række variable: mikrostrukturen af de ikkeinfiltrerede elektroder, elektrodernes polarisations modstand - både under og uden polarisation, de elektriske og morfologiske egenskaber af de infiltrerede materialer og den specifikke reaktion, som selve propen oxidationen er.  Selvom både de ikke-infiltrerede LSM/CGO og LSF/CGO elektroder var i stand til at oxidere propen, var LSM/CGO bedst både i forhold til katalytisk aktivitet og Faradaisk effektivitet under propen oxidationen. Mens LSF/CGO blev ustabil under langvarig polarisation, udviste LSM/CGO en markant elektrode aktivering samt forbedring af den katalytiske aktivitet efter langvarig polarisation. Infiltrering af LSM/CGO elektroderne med Ce0.9Gd0.1O1.95 varmebehandlet ved lav temperatur, var det bedste kompromis i forhold til at opnå en høj propen omsætning uden polarisering kombineret med en stærk forbedring af reaktionshastighed forholdet og Faradaisk effektiviteten ved lave temperaturer (300-350 °C). På trods af, at stabilitetsproblemer påvirkede LSM/CGO elektroder infiltreret flere gange med Ce0.9Gd0.1O1.95, var den stærke aktivering under langvarig polarisation i stand til delvist at modvirke den manglende stabilitet af den infiltrede Ce0.9Gd0.1O1.95. Dette projekt demonstrerede muligheden for at øge propen oxidationen ved at polarisere en porøs, keramisk reaktor. Infiltreringen af forskellige aktive materialer medvirkede til at øge den katalytiske aktivitet uden polarisation, samt til at øge effekten af polarisation på propen oxidations hastigheden ved lav temperatur.  Den fremtidige udvikling af denne teknologi vil fokusere på infiltrering af en aktiv propen oxidations katalysator kombineret med infiltrering af en NOx lagrings forbindelse med det mål at opnå simultan oxidation af propen og reduktion af NOx med høj effektivitet.This study investigated the use of a ceramic porous electrochemical reactor for the deep oxidation of propene. Two electrode composites, La0.85Sr0.15MnO3±d/Ce0.9Gd0.1O1.95 (LSM/CGO) and La0.85Sr0.15FeMnO3/Ce0.9Gd0.1O1.95 (LSF/CGO), were produced in a 5 single cells stacked configuration and used as backbone for the infiltration of materials able to modify the electrochemical and catalytic activity of the reactor. The catalytic activity of the reactor and the effect of polarization on the propene oxidation have been studied by gas analysis with a gas chromatograph (GC), during the reactor polarization at different reaction temperatures. The study of the effect of the infiltration of different electroactive materials on the electrode behavior has been carried on by the use of electrochemical impedance spectroscopy (EIS). Both the methods have been employed to understand the relationship between the catalytic activity of the reactor under polarization and the reactor electrochemical behavior. The impact of the morphology of the infiltrated material on the electrocatalytic activity was assessed by scanning electron microscopy. This project helped to better understand how the effect of polarization on propene conversion was a complex function of multiple variables: the microstructure of the backbone, the polarization resistance of the electrodes, both at OCV and under polarization, the electrical and morphological properties of the infiltrated material and the specific reaction conditions like the propene conversion. Although both the LSM/CGO and LSF/CGO backbones have demonstrated the ability to oxidize propene, the LSM/CGO exhibited the best performance both in terms of catalytic activity and faradaic efficiency for the propene oxidation. While LSF/CGO showed instability due to prolonged polarization, the LSM/CGO exhibited a strong electrode activation and increase of catalytic activity after the application of prolonged polarization. The infiltration of LSM/CGO backbone with Ce0.9Gd0.1O1.95, heat treated at low temperature to form a continuous layer on the electrode, was the best compromise to obtain high propene conversion at open circuit voltage together high rate enhancement ratio and faradaic efficiency values at low temperatures (300-350 °C). Although some stability problems affected the performance of multiple infiltrated Ce0.9Gd0.1O1.95 on LSM/CGO backbone, the strong activation of LSM upon prolonged polarization was able to partially counteract the instability of the infiltrated Ce0.9Gd0.1O1.95. This project demonstrated the possibility to enhance the oxidation of propene by polarization in a porous ceramic reactor. The infiltration of different active materials helped to increase the catalytic activity at open circuit voltage and the effect of polarization on propene oxidation rate at low temperature. The future development of this technology will see the infiltration of an active catalyst towards propene oxidation together with a NOx storage compound for the simultaneous oxidation of propene and the reduction of NOx with high efficiency.</p

Online Research Database In Technology

Low temperature oxidation of hydrocarbons using an electrochemical reactor

http://orbit.dtu.dk/ws/files/77803556/Davide_Ippolito_PhD_thesis_April_2013..PDF

Low temperature oxidation of hydrocarbons using an electrochemical reactor

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Online Research Database In Technology