Enhanced dry reforming of methane over nickel catalysts supported on zirconia coated mesoporous silica

Abstract

Dry reforming of methane (DRM) offers a sustainable route to convert CH₄ and CO₂ into syngas, addressing both greenhouse gas emissions and energy demand. However, catalyst deactivation due to sintering and coking limits practical applications. In this work, we developed a mesoporous Ni-based catalyst (Ni/ZrSBA-15-OH) featuring abundant Ni-ZrO₂ interfaces and small Ni nanoparticles (5.6 nm) confined within a stable silica framework. This catalyst showed excellent performance, achieving 80% CH₄ and 87% CO₂ conversions at 750°C, with minimal coke formation (0.4 mg g_cat ^-1 h^-1) and high durability (1.3% CH₄ conversion loss over 20 h). Advanced characterizations (X-ray absorption spectroscopy [XAS], transmission electron microscopy [TEM], H₂-temperature programmed reduction [H₂-TPR], and temperature-programmed surface reaction [TPSR]) revealed that the metal-oxide interface enhances the activation of reactants and stabilizes active sites. Density functional theory (DFT) calculations confirmed that the Ni-ZrO₂ interface increases the energy barrier for CH∗ dehydrogenation, effectively suppressing carbon deposition. This study provides a rational strategy for designing structurally robust and coke-resistant Ni-based catalysts for efficient DRM.

Keywords: Chemistry; Materials chemistry; Materials science.

Graphical abstract

Figure 1

Structural characterization of fresh catalysts (A–C) (A) LAXRD patterns, (B) WAXRD patterns, (C) nitrogen adsorption-desorption isotherms and corresponding pore size distribution plots (insert) of Ni/SBA-15-OH and Ni/ZrSBA-15-OH catalysts. (D) TEM image of Ni/ZrSBA-15-OH, with NiO particle size distribution shown in the insert. (E–L) (E) High-resolution TEM image, (F) Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) image, (G) Scanning transmission electron microscopy (STEM) image, and (H–L) Energy-dispersive X-ray spectroscopy (EDX) elemental mappings of the Ni/ZrSBA-15-OH catalyst. The white dashed line in (f) represents the heterogeneous interfaces between NiO particle and ZrO₂ support.

Figure 2

Catalytic performances of Ni-based catalysts in the DRM reaction (A and B) (A) CH₄ conversion and (B) CO₂ conversion over Ni-based supported catalysts. Reaction conditions: CH₄:CO₂:N₂ = 2:2:1, weight hourly space velocity (WHSV) = 30,000 mL g_cat⁻¹ h⁻¹. (C) Comparison of mass-specific activity between Ni/ZrSBA-15-OH and other typical catalysts used in the DRM reaction. (D) Kinetic studies and calculated activation energy (E_a) for CH₄ over Ni/ZrSBA-15-OH and Ni/SBA-15-OH. (E and F) (E) CH₄ and (F) CO₂ conversion of Ni-based catalysts as a function of time on stream at 750°C under reaction conditions. (G and H) (G) H₂/CO ratio and (H) carbon balance over the Ni-based supported catalysts.

Figure 3

Characterization of Ni-ZrO₂ Interactions (A) Normalized Ni K-edge XANES spectra of Ni/ZrSBA-15-OH, Ni foil, and NiO. (B) Fourier transform (FT)-EXAFS spectra of Ni/ZrSBA-15-OH compared with Ni foil and NiO. (C–H) (C) k³-weighted Fourier transformed EXAFS spectra of Ni foil, NiO, and Ni/ZrSBA-15-OH. Wavelet transform (WT) results of the EXAFS signals for (D) Ni foil, (E) NiO, and (F) Ni/ZrSBA-15-OH. XPS analysis of (G and H) Ni/ZrSBA-15-OH and Ni/SBA-15-OH after H₂ reduction for 2 h at 500°C. (I) H₂-TPR profiles of Ni/ZrSBA-15-OH and Ni/SBA-15-OH under a heating rate of 10 °C min⁻¹ and an H₂ flow rate of 50 mL min⁻¹.

Figure 4

Structural characterization of spent catalysts (A and B) (A) WAXRD patterns, (B) nitrogen adsorption-desorption isotherms and corresponding pore size distribution plots (insert) of Ni/SBA-15-OH-used and Ni/ZrSBA-15-OH-used catalysts. (C and D) (C) TEM image and (D) HR-TEM images of Ni/SBA-15-OH-used. (E–J) (E) STEM image and (F–J) corresponding EDX mappings of Ni/ZrSBA-15-OH-used. (K and L) (K) TGA curves with corresponding DSC profiles (insert) and (L) Raman spectra of Ni/SBA-15-OH-used, Ni/ZrSBA-15-OH-used, Ni/SCO-Zr and Ni/Commercial ZrO₂ catalysts.

Figure 5

TPSR-MS and in-situ DRIFTS analysis of DRM mechanisms TPSR-MS profiles of Ni/SBA-15-OH (A) and Ni/ZrSBA-15-OH (C) after CH₄ introduction. TPSR-MS signals of Ni/SBA-15-OH (B) and Ni/ZrSBA-15-OH (D) after CO₂ introduction following CH₄ treatment. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of Ni/SBA-15-OH (E) and Ni/ZrSBA-15-OH (F) under a CH₄ atmosphere.

Figure 6

Reaction energy profiles for CH₄ activation on different interfaces Energy diagrams for CH₄∗ → CH₃∗ + H∗, CH₃∗ → CH₂∗ + H∗, CH₂∗→ CH∗ + H∗ and CH∗ → C∗ + H∗ on Ni/ZrSBA-15-OH (Ni-ZrO₂ interface) and Ni/SBA-15-OH (Ni-SiO₂ interface).