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

[Display omitted] •Catalyst-assisted chemical looping dry reforming is a promising technology for syngas production.•Pressure-induced collapse of the core-shell structure is reaction-related.•Increase pressure promotes carbon filaments on Ni particles and extends the presence of the low-melting-poin...

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Vydáno v:Applied catalysis. B, Environmental Ročník 247; s. 86 - 99
Hlavní autoři: Hu, Jiawei, Galvita, Vladimir V., Poelman, Hilde, Detavernier, Christophe, Marin, Guy B.
Médium: Journal Article
Jazyk:angličtina
Vydáno: Amsterdam Elsevier B.V 15.06.2019
Elsevier BV
Témata:
Auto-thermal reforming
Bifunctional catalyst
Carbon
Carbon dioxide
Catalysis
Catalysts
CO2 utilization
Control stability
Core-shell structure
Cycles
Deactivation
Deposition
Filaments
High pressure
Industrial applications
Iron
Melting point
Melting points
Methane
Nanomaterials
Nanotechnology
Nickel
Organic chemistry
Oxygen
Phase transitions
Pressure
Reactors
Redox properties
Reduction
Reforming
Sintering
Synthesis gas
Zirconium
Methane
CO2 utilization
Bifunctional catalyst
Auto-thermal reforming
ISSN:0926-3373, 1873-3883
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Shrnutí:[Display omitted] •Catalyst-assisted chemical looping dry reforming is a promising technology for syngas production.•Pressure-induced collapse of the core-shell structure is reaction-related.•Increase pressure promotes carbon filaments on Ni particles and extends the presence of the low-melting-point FeO phase.•Adding a small amount of O2 makes the process auto-thermal, which is advantageous in eliminating carbon. 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 °C and 1–10 bar) and ex-situ characterization (STEM-EDX, XRD and N2 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 H2/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 O2 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.
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ISSN:0926-3373
1873-3883
DOI:10.1016/j.apcatb.2019.01.084