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Pressure-induced deactivation of core-shell nanomaterials for catalyst assisted chemical looping

Jiawei Hu (UGent) , Vladimir Galvita (UGent) , Hilde Poelman (UGent) , Christophe Detavernier (UGent) and Guy Marin (UGent)
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Abstract
Catalyst-assisted chemical looping dry reforming is a promising technology for CO-rich syngas production with maximized CO2 utilization, especially when performed auto-thermally, over core-shell nanomaterials in a double-zone reactor bed with first a Fe/Zr@Zr-Ni@Zr bifunctional catalyst and next a Fe/Zr@Zr oxygen storage material. Understanding the origin of the material deactivation under high-pressure conditions is essential to advance this technology towards industrial application. Therefore, pressure-induced material deactivation was studied through a series of on-site assessments (steady-state CH4 reforming and prolonged redox cycling at 750 degrees C and 1-10 bar) and ex-situ characterization (STEM-EDX, XRD and N-2 adsorption-desorption). At high pressure, both Fe/Zr@Zr-Ni@Zr and Fe/Zr@Zr show reaction-related deactivation, the origin of which can be ascribed to carbon deposition and particle sintering, respectively. During regular catalyst-assisted dry reforming over Fe/Zr@Zr-Ni@Zr, the rise of pressure decreases CH4 conversion and increases carbon deposition on the Ni surface. Rapidly growing carbon filaments destroy the core-shell structure, resulting in segregation of the Ni-based particles from the catalyst bulk with concomitant severe sintering. During H-2/CO2 redox cycling of Fe/Zr@Zr, an increased pressure decreases the time-averaged space-time yield of CO. In the reduction half-cycle, high pressure prolongs the existence of the FeO intermediate phase in the transformation of Fe/Zr@ Zr, which decreases the material's melting point, leading to fast sintering. Adding a small amount of O-2 makes the chemical looping dry reforming process auto-thermal, which is advantageous in eliminating carbon. Nevertheless, deactivation of the double-zone reactor bed still occurs and is mainly ascribed to particle sintering, following similar principles as mentioned above. For both regular and auto-thermal catalyst-assisted chemical looping dry reforming, the decreasing ability for CO2 utilization is naturally due to the deactivation of the oxygen storage material, but also controlled by the stability of the bifunctional catalyst. The latter determines the reduction capacity of the gas product mixture in the reduction half-cycle, thereby affecting the achievable reduction degree of the oxygen storage material.
Keywords
CARBON-DIOXIDE SEPARATION, PACKED-BED REACTORS, OXYGEN CARRIERS, REDOX, CHEMISTRY, CO2 CONVERSION, NI CATALYSTS, METHANE, PERFORMANCE, STABILITY, HYDROGEN, Bifunctional catalyst, CO2 utilization, Auto-thermal reforming, Methane

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Chicago
Hu, Jiawei, Vladimir Galvita, Hilde Poelman, Christophe Detavernier, and Guy Marin. 2019. “Pressure-induced Deactivation of Core-shell Nanomaterials for Catalyst Assisted Chemical Looping.” Applied Catalysis B-environmental 247: 86–99.
APA
Hu, Jiawei, Galvita, V., Poelman, H., Detavernier, C., & Marin, G. (2019). Pressure-induced deactivation of core-shell nanomaterials for catalyst assisted chemical looping. APPLIED CATALYSIS B-ENVIRONMENTAL, 247, 86–99.
Vancouver
1.
Hu J, Galvita V, Poelman H, Detavernier C, Marin G. Pressure-induced deactivation of core-shell nanomaterials for catalyst assisted chemical looping. APPLIED CATALYSIS B-ENVIRONMENTAL. 2019;247:86–99.
MLA
Hu, Jiawei et al. “Pressure-induced Deactivation of Core-shell Nanomaterials for Catalyst Assisted Chemical Looping.” APPLIED CATALYSIS B-ENVIRONMENTAL 247 (2019): 86–99. Print.
@article{8609291,
  abstract     = {Catalyst-assisted chemical looping dry reforming is a promising technology for CO-rich syngas production with maximized CO2 utilization, especially when performed auto-thermally, over core-shell nanomaterials in a double-zone reactor bed with first a Fe/Zr@Zr-Ni@Zr bifunctional catalyst and next a Fe/Zr@Zr oxygen storage material. Understanding the origin of the material deactivation under high-pressure conditions is essential to advance this technology towards industrial application. Therefore, pressure-induced material deactivation was studied through a series of on-site assessments (steady-state CH4 reforming and prolonged redox cycling at 750 degrees C and 1-10 bar) and ex-situ characterization (STEM-EDX, XRD and N-2 adsorption-desorption). 
At high pressure, both Fe/Zr@Zr-Ni@Zr and Fe/Zr@Zr show reaction-related deactivation, the origin of which can be ascribed to carbon deposition and particle sintering, respectively. During regular catalyst-assisted dry reforming over Fe/Zr@Zr-Ni@Zr, the rise of pressure decreases CH4 conversion and increases carbon deposition on the Ni surface. Rapidly growing carbon filaments destroy the core-shell structure, resulting in segregation of the Ni-based particles from the catalyst bulk with concomitant severe sintering. During H-2/CO2 redox cycling of Fe/Zr@Zr, an increased pressure decreases the time-averaged space-time yield of CO. In the reduction half-cycle, high pressure prolongs the existence of the FeO intermediate phase in the transformation of Fe/Zr@ Zr, which decreases the material's melting point, leading to fast sintering. Adding a small amount of O-2 makes the chemical looping dry reforming process auto-thermal, which is advantageous in eliminating carbon. Nevertheless, deactivation of the double-zone reactor bed still occurs and is mainly ascribed to particle sintering, following similar principles as mentioned above. 
For both regular and auto-thermal catalyst-assisted chemical looping dry reforming, the decreasing ability for CO2 utilization is naturally due to the deactivation of the oxygen storage material, but also controlled by the stability of the bifunctional catalyst. The latter determines the reduction capacity of the gas product mixture in the reduction half-cycle, thereby affecting the achievable reduction degree of the oxygen storage material.},
  author       = {Hu, Jiawei and Galvita, Vladimir and Poelman, Hilde and Detavernier, Christophe and Marin, Guy},
  issn         = {0926-3373},
  journal      = {APPLIED CATALYSIS B-ENVIRONMENTAL},
  language     = {eng},
  pages        = {86--99},
  title        = {Pressure-induced deactivation of core-shell nanomaterials for catalyst assisted chemical looping},
  url          = {http://dx.doi.org/10.1016/j.apcatb.2019.01.084},
  volume       = {247},
  year         = {2019},
}

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