Zirconium Carbide Mediates Coke‐Resistant Methane Dry Reforming on Nickel‐Zirconium Catalysts

Abstract

Graphitic deposits anti-segregate into Ni 0 nanoparticles to provide restored CH 4 adsorption sites and near-surface/dissolved C atoms, which migrate to the Ni 0 /ZrO 2 interface and induce local Zr x C y formation. The resulting oxygen-deficient carbidic phase boundary sites assist in the kinetically enhanced CO 2 activation toward CO(g). This interface carbide mechanism allows for enhanced spillover of carbon to the ZrO 2 support, and represents an alternative catalyst regeneration pathway with respect to the reverse oxygen spillover on Ni-CeZr x O y catalysts. It is therefore rather likely on supports with limited oxygen storage/exchange kinetics but significant carbothermal reducibility.

Enhanced Dry Reforming of Methane Catalysis by Ni at Heterointerfaces between Thin MgAlOx and Bulk ZrO2

“…Recent works by Haug et al have also highlighted the beneficial contribution of support reducibility, basicity, and reactivity of oxygen vacancies coexisting at the phase boundary to promote CO 2 activation and conversion. [39] In addition, interfacial sites between Ni and basic supports have been documented to facilitate the dissociation of CH 4 to form CH x and H species, which react with the CO 2 adsorbed as bicarbonate rather than undergoing completed cleavage to form coke . [40] The latter mechanism is consistent with our observations of minor coke formation observed on our catalyst (vide infra).…”

CO2 Reforming of Ethanol over Ni/Al2O3-(Zr–Yb)O2 Catalysts: The Effect of Zr:Al Ratio on Nickel Activity and Carbon Formation

“…However, the increase in CO 2 conversion and the increase in CO yield at high temperatures on Ni/65AZ (Figure 1) may be related to the activation of the CO 2 molecule by active carbide forms of carbon. 71 The total amount of carbon deposition decreased with an increasing amount of Zr in the support. The suppressed coke deposition in Ni/35AZ could be due to the low acidity and high basicity of the sample compared with Ni/65AZ.…”

“…Thus, on the spent Ni/35AZ, surface amorphous carbon and carbides (around 40%) are equally presented, while on the spent Ni/65AZ, surface carbide forms are predominantly (62%) formed, and an equal amount of carbon (20% each) is attributed to sp2 and sp3 hybridization of C−C or C− H bonds. The significant amount of carbides formed during catalysis can be attributed to the carbon spillover effect, 71 which is prevailing on small nickel nanoparticles with high surface interaction. Figure 6 shows more carbide forms on the Al-rich sample, as well as smaller nickel nanoparticles (based on XRD data).…”

“…This correlates with the Ni-carbon interaction and the nature of carbon on the surface with irregular amorphous structure, which is more likely formed on Ni/35AZ does not lead to a decrease in catalytic stability and H 2 and CO yields and contributes less to the formation of carbides under the influence of the reaction environment. However, taking into account the significant amount of carbides on the surface of our spent catalysts and the data available for methane dry reforming, 71 the role of carbides in the EDR reaction on Ni/ AZ catalysts requires a more thorough investigation. Thus, the slow deactivation of CO 2 and EtOH conversion was not related to the sintering of Ni particles but rather to the amount and chemical composition of carbon deposits.…”

Emergent Ni catalysts induced by nitride-to-oxide transformation for coking and sintering resistant dry reforming of methane

“…Recently, zirconia has been widely studied as a support due to its excellent oxidation-reduction ability, thermal stability, and higher surface oxygen migration, making it a promising candidate for DRM. [42][43][44] However, the use of ZrO 2 as a support has been limited by the tendency of the catalyst to produce a large amount of coke in high-temperature reactions. 45 This issue is compounded by the sintering of Ni particles during the reaction process, which leads to reduced or even deactivated catalyst activity.…”