Modelling the Sintering of Nickel Particles Supported on γ-Alumina under Hydrothermal Conditions

Abstract

Sintering of nickel particles is a well-known path of deactivation for Ni/Al2O3 catalysts. Considering the CO2 methanation in the context of Power-to-Gas, a sintering study for up to 300 h was performed in a controlled atmosphere between 450 and 600 °C. Since water is a product of the methanation reaction and is known to favor the particle sintering, the H2O:H2 molar ratio was varied in the range 0–3.2. Characterization of the post mortem samples showed sintering of both nickel and support particles. The absence of carbon oxides in the gas feed allows us to rule out other causes of deactivation such as carbon deposits. A sintering law is derived from the loss of metallic surface area with time-on-stream according to local temperature and H2O:H2 molar ratio. An excellent fit of the experimental data was obtained allowing the prediction of the metallic surface area within 15%.

A Short Review on Ni‐Catalyzed Methanation of CO2: Reaction Mechanism, Catalyst Deactivation, Dynamic Operation

“…For TEM images, the average metal particle size was obtained from several measurements in two orthogonal directions. A sample of 30 particles found a growth in average metal particle size from 6.5 nm for a sample aged for 20 h up to 10.5 nm for a sample aged for 100 h. [57] CO 2 conversions and CH 4 yields of catalysts after hydrothermal aging of different periods are shown in Fig. 3.…”

“…This confirms the general opinion that sintering of nickel particles is a major cause of deactivation for methanation catalysts. [57] Champon et al determined the loss of metal surface due to sintering of metal particles by measuring metal surfaces with hydrogen chemisorption and temperature-programmed desorption (H 2 -TPD). They adapted the GPLE previously proposed by Fuentes [51] taking into account that higher H 2 O/H 2 ratios promote sintering [57]:…”

“…Taking temperature and local atmosphere into account, the GPLE was able to describe the nickel particle sintering depending on TOS (for up to 300 h) for a Ni/Al 2 O 3 catalyst at temperatures between 450 and 600°C and H 2 O/H 2 ratios between 0 and 3.2 with an error of ±15 %. [57] In future studies, the group will further investigate the catalytic activity depending on the operating time under the reactive conditions of CO 2 methanation (H 2 /CO 2 = 4). The aim is to relate experimental deactivation results with modeled ones by coupling a kinetic model of CO 2 methanation [58] with the previously shown sintering law.…”

“…Figure 3. Measurements of CO 2 conversion and CH 4 yield at 350°C of fresh and post-mortem samples, which were previously hydrothermally aged, as a function of a) the hydrothermal aging time and b) the relative metallic surface., CO 2 conversion; ¢ , CH 4 yield [57]. …”

Hydrothermal Sintering and Oxidation of an Alumina-Supported Nickel Methanation Catalyst Studied Using In Situ Magnetometry

“…The authors also reported the formation of nickel aluminate (NiAl 2 O 4 ) and nickel oxide (NiO) at high temperatures and P H2O /P H2 . Champon et al [28] showed that an increase in the H 2 O/H 2 ratio results in increased sintering of Ni, which was successfully modelled by a generalised power-law expression.…”