Ru/Al2O3 on Polymer-Derived SiC Foams as Structured Catalysts for CO2 Methanation (original) (raw)
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Ru/Ce/Ni Metal Foams as Structured Catalysts for the Methanation of CO2
Catalysts
The development of highly conductive structured catalysts with enhanced mass- and heat-transfer features is required for the intensification of the strongly exothermic catalytic hydrogenation of CO2 in which large temperature gradients should be avoided to prevent catalyst deactivation and to control selectivity. Therefore, in this work we set out to investigate the preparation of novel structured catalysts obtained from a commercial open cell Ni foam with high pore density (75 ppi) onto which a CeO2 layer was deposited via electroprecipitation, and, eventually, Ru was added by impregnation. Composite Ru/Ce/Ni foam catalysts, as well as simpler binary Ru/Ni and Ce/Ni catalysts were characterized by SEM-EDX, XRD, cyclic voltammetry, N2 physisorption, H2-temperature programmed reduction (TPR), and their CO2 methanation activity was assessed at atmospheric pressure in a fixed bed flow reactor via temperature programmed tests in the range from 200 to 450 °C. Thin porous CeO2 layers, uni...
Macroporous silicon carbide foams for porous burner applications and catalyst supports
Journal of Physics and Chemistry of Solids, 2007
Pre-ceramic polymer (MK-polymer)-based nitrogen-bounded silicon carbide (NBSiC) has been developed and the concept utilised to produce macroporous ceramic foam structures by a modified sponge replica technique. In order to increase the strut thickness and to fill up the hollow struts and thus increase the mechanical strength of the microporous structures, repeated re-infiltrations and pre-sintering steps are investigated. The double-ring bending strength could be increased with increasing polymer content and coating, respectively infiltration cycles up to a maximum value of 140 MPa for NBSiC discs, nitrided at 1400 1C. After a re-crystallisation process at 1850 1C, the influence of the polymer is negligible and the bending strength is only in the region of 50 MPa, as re-crystallised SiC (RSiC) is the dominant phase. The oxidation behaviour of NBSiC corresponds with the oxidation behaviour of commercial SiC. EDX analysis of samples nitrided at 1400 1C shows the composition containing grains of SiC, Si 3 N 4 and Si 2 N 2 O.
Applied Catalysis A: General, 2011
The Fischer-Tropsch synthesis was evaluated on cobalt based catalyst supported on a medium surface area SiC foam ceramic in a fixed-bed configuration. The catalytic results were compared with those obtained on a Co/Al 2 O 3 foam catalyst. At medium conversion (<50%) the two catalysts display similar C 5+ selectivity indicate that the intrinsic selectivity between the two catalysts is close from each other. However, when the CO conversion was increased to 70%, a significant difference in terms of the C 5+ selectivity was observed between the two catalysts, i.e. 80% on the Co/SiC and 54% on the Co/Al 2 O 3 , which indicate that under severe FTS reaction conditions the SiC seems to be more suitable support than alumina. It is also worth to note that under these reaction conditions the chain length probability,˛, obtained on the SiC-based catalyst was 0.91 and wax formation was especially favoured. The improvement of the C 5+ selectivity observed on the SiC catalyst was attributed to the high efficiency of the support to evacuate heat generated during the course of the reaction owing to it higher thermal conductivity and also to the presence of meso-and macro-porosity of the support. Additional catalytic test conducted on a hybrid support, i.e. Al 2 O 3 coated SiC foam, again confirms the high C 5+ selectivity under a similar severe reaction conditions in the presence of a SiC structure underneath of the alumina layer which play a role of heat disperser. In addition, the high chemical inertness of the SiC material also allows one to perform an easy recovery of both the active phase and the support by a simple acid washing. The recovered SiC support was further impregnated with a fresh cobalt phase and re-tested in the FTS and the catalytic results are compared with those of the former catalyst. The same product yield was obtained which confirms the potential of SiC to be employed as a re-usable support.
Annales de chimie Science des Matériaux, 2018
In this work, the Me/CeO2 (Me = Rh, Ni) catalytic phase was in-situ deposited by the Solution Combustion Synthesis (SCS) on commercial cordierite monolith (500 cpsi) and alumina open-cell foams (20,30,40 ppi). All the coated structures were characterized by SEM/EDX to analyze the morphological characteristics of the coated films; the mechanical stability was analyzed by ultrasound tests; pressure drops at different superficial velocities were derived. The catalytic activity and stability were investigated towards Steam Reforming (SR) and Oxy-Steam Reforming (OSR) of different fuels (CH4, biogas, n-dodecane) and CO2 methanation reaction. High catalytic activity was observed for both reforming and methanation processes, following the order 500 cpsi-monolith < 20 ppi-foam < 30 ppi-foam ≈ 40 ppi-foam. Excellent long-term stability was observed over 200 h of time-on-stream (TOS). RÉSUMÉ. Dans cet article, la phase catalytique Me/CeO2 (Me = Rh, Ni) a é té dé posé e in situ par la synthè se de combustion en solution (SCS, le sigle de « Solution Combustion Synthesis » en anglais) sur des monolithes de cordié rite (500 cpsi) et des mousses à cellules ouvertes d'alumine (20,30,40 ppi). Toutes les structures revê tues ont é té caracté risé es par SEM / EDX pour analyser les caracté ristiques morphologiques des films revê tus; la stabilité mé canique a é té analysé e par ultrasons; la permé abilité et le coefficient de forme ont é té dé rivé s des donné es de chute de pression. L'activité et la stabilité catalytique ont é té é tudié es pour les ré actions de reformage à la vapeur (SR, le sigle de « Steam Reforming » en anglais) et à l'oxy-vapeur (OSR, le sigle de « Oxy-Steam Reforming » en anglais) de diffé rents combustibles (CH4, biogaz, n-dodé cane) et la ré action de mé thanisation au CO2. Une activité catalytique é levé e a é té observé e à la fois pour les procé dé s de reformage et de mé thanation, suivant l'ordre de 500 cpsi-monolithe <20 ppi-mousse <30 ppi-mousse ≈ 40 ppi-mousse. Une excellente stabilité à long terme a é té observé e sur une pé riode de 200 heures d'utilisation (TOS, le sigle de « time-on-stream » en anglais).
CO2 methanation over Co-Ni/Al2O3 and Co-Ni/SiC catalysts
Bulgarian Chemical Communications, 2020
In this study, highly loaded 20 wt% (СоxNi100–x)/Al2O3 and (СоxNi100–x)/SiC catalysts, where x = 0, 20, 60, 80, and 100 wt%, were prepared by a three-stage method, which includes wet impregnation of Al2O3 and SiC with the metal nitrates, thermal decomposition of the loaded nitrates, and obtaining of the loaded metals by reducing their oxides with hydrogen at 350 °C. The prepared catalysts were examined by different methods and tested in the CO2 methanation. Scanning electron microscopy and X-ray powder diffraction studies showed a difference in the loaded particle dispersion and the phase composition of catalysts. The highly loaded 20 wt% Co–Ni/Al2O3 catalysts showed the highest catalytic activity. In the presence of 20 wt% Co60Ni40/Al2O3, 20 wt% Co80Ni20/Al2O3, and 20 wt% Co100/Al2O3 catalysts, 100% CO2 can be converted into CH4 at 300 °C. This temperature is lower by 100 °C than the temperature at the total conversion over 20 wt% (Co–Ni)/SiC catalysts. Thermal desorption mass spectroscopy revealed that the methanation of CO2 passed through the formation of CHO* intermediate over the most active 20 wt% Co80Ni20/Al2O3 and 20 wt% Co80Ni20/SiC catalysts.
Structured ZSM-5/SiC foam catalysts for bio-oils upgrading
Applied Catalysis A: General, 2020
ZSM-5 zeolite coating supported on SiC foams was prepared by a precursor dispersion-secondary growth method and the resulting structured ZSM-5/SiC foam catalyst was used for the proof-of-concept study of catalytic bio-oils upgrading (i.e. deoxygenation of the model compounds of methanol and anisole) in reference to ZSM-5 catalyst pellets. A layer of ZSM-5 coating with inter-crystal porosity on SiC foams was produced by curing the zeolite precursor thermally at 80°C. The use of SiC foam as the zeolite support significantly improved transport phenomena compared to the packed-bed using ZSM-5 pellets, explaining the comparatively good catalytic performance achieved by the structured ZSM-5/SiC foam catalyst. In comparison with the ZSM-5 pellets, the ZSM-5/ SiC foam catalyst showed 100.0% methanol conversion (at the weight hourly space velocity, WHSV, of 8 h-1) and 100.0% anisole conversion (at WHSV =5 h −1) at the initial stage of the processes, while only about 3% were obtained for the ZSM-5 pellets, under the same conditions. Based on the comparative analysis of the characterisation data on the fresh and spent catalysts, the deactivation mechanisms of the ZSM-5/SiC and the ZSM-5 pellet catalysts were explained. The process intensification using SiC foam to support ZSM-5 improved the global gas-to-solid mass transfer notably, and hence mitigating the pore blocking due to the carbon deposition on the external surface of supported ZSM-5.