Pivotal Role of Ni/ZrO2 Phase Boundaries for Coke-Resistant Methane Dry Reforming Catalysts

Abstract

To identify the synergistic action of differently prepared Ni-ZrO2 phase boundaries in methane dry reforming, we compared an “inverse” near-surface intermetallic NiZr catalyst precursor with the respective bulk-intermetallic NixZry material and a supported Ni-ZrO2 catalyst. In all three cases, stable and high methane dry reforming activity with enhanced anticoking properties can be assigned to the presence of extended Ni-ZrO2 phase boundaries, which result from in situ activation of the intermetallic Ni-Zr model catalyst systems under DRM conditions. All three catalysts operate bifunctionally; methane is essentially decomposed to carbon at the metallic Ni0 surface sites, whereas CO2 reacts to CO at reduced Zr centers induced by a spillover of carbon to the phase boundaries. On pure bulk Ni0, dissolved carbon accumulates in surface-near regions, leading to a sufficiently supersaturated state for completely surface-blocking graphitic carbon segregation. In strong contrast, surface-ZrO2 modified bulk Ni0 exhibits virtually the best decoking and carbon conversion conditions due to the presence of highly dispersed ZrO2 islands with a particularly large contribution of interfacial Ni0-ZrO2 sites and short C-diffusion pathways to the latter.

Recent Advances in Coke Management for Dry Reforming of Methane over Ni-Based Catalysts

“…This method involves depositing oxide islands on top of the active metal substrate to create a structurally "mirrored" system. This catalyst exhibits stable and high DRM activity, along with an enhanced resistance to coking [87]. The coke resistance of the catalysts strongly depended on the size of the Ni nanoparticles.…”

“…This anti-segregation process creates a carbophobic and oxophilic cial zone at the Ni/ZrO2 interface, which protects the catalyst from coke formatio they used a novel "reverse" chemical vapor deposition method to design a NiZ catalyst, which is completely opposite to the preparation of traditional cataly method involves depositing oxide islands on top of the active metal substrate to structurally "mirrored" system. This catalyst exhibits stable and high DRM activi with an enhanced resistance to coking [87]. The coke resistance of the catalysts depended on the size of the Ni nanoparticles.…”

Research Progress on Stability Control on Ni-Based Catalysts for Methane Dry Reforming

“…Ni-based DRM catalysts generally use porous oxides as supports, such as metal oxides γ-Al 2 O 3 [12,41], SiO 2 [40,42], MgO [43], ZrO 2 [11,44], CeO 2 [45] with rich acidic/alkali sites or good reducibility [46]. The structure, acidity, and alkalinity of the support, defects, and the use of the new catalyst support will affect the carbon deposition [40,42,47,48].…”

“…Recently, some research teams innovatively constructed nanostructured oxides the surface of metals to form reverse oxide-on-metal catalysts [44,64]. Due to the inter tion between the oxide and the metal, the oxide formed on the metal surface is a sing layer dispersed, metastable structure, and metal active centers with coordination unsa rated are formed at the oxide-metal boundary, which can efficiently activate O2, H2O, a other molecules, and can be successfully used in low-temperature catalytic oxidation, e Another group has successfully grown nano-ZrO2 films on Pt, Cu, Pd, and Ni, denoted ZrO2@M (M = Ni, Pt, Cu, Pd), using chemical vapor deposition and applying them to t DRM reaction.…”

“…Graphitic deposits are anti-segregated into Ni 0 nanoparticles to provide restored CH 4 adsorption sites and near-surface/dissolved C atoms, which migrate toward the Ni 0 /ZrO 2 interface and induce local Zr x C y formation. The resulting oxygen-deficient carbidic phase boundary sites assist in kinetically enhanced CO 2 activation toward CO [44,64].…”