A mesoporous ZSM-5 supported Ni catalyst for enhanced dry reforming of methane: New insights into improved textural properties, surface basicity and reducibility

This work investigates the dry reforming of methane (DRM) over a 10 w/w% Ni-loaded hierarchical ZSM-5 support (Ni/ZSM-5-S catalyst), synthesized via a seed-assisted hydrothermal method. The Ni/ZSM-5-S catalyst exhibited remarkable physicochemical advantages compared to 10 w/w% Ni-loaded commercial ZSM-5 (Ni/ZSM-5-C catalyst), including a significantly higher BET surface area (589 m² g⁻¹ vs. 402 m² g⁻¹), a large mesopore volume (0.72 cm³ g⁻¹), and enhanced surface basicity. These features promoted strong metal–support interactions and facilitated the formation of highly dispersed NiO nanoparticles with an average crystallite size of 12.9 nm. Catalytic performance tests revealed outstanding activity and stability. At 700 °C, Ni/ZSM-5-S achieved steady conversions of CH₄ (80.0%) and CO₂ (82.5%) over 24 h, while at elevated temperatures (800–1000 °C), near-complete conversions (90–100%) were observed. The hierarchical architecture significantly mitigated deactivation; thermogravimetric analysis quantified carbon deposition at only 70 mg C·g_cat⁻¹ (7% mass loss), compared to 311 mg C·g_cat⁻¹ for the commercial counterpart. Raman spectroscopy confirmed that the deposited carbon was predominantly amorphous (I_D/I_G = 2.30), which is easily oxidizable and thus favorable for regeneration. Mechanistic insights from in-situ DRIFTS demonstrated that syngas formation proceeds via a Langmuir–Hinshelwood pathway, involving co-adsorption and surface reaction of CH₄ and CO₂ on adjacent Ni and zeolite sites. Collectively, these findings establish Ni/ZSM-5-S as a robust, coke-resistant catalyst with superior structural integrity and long-term stability, offering a promising route for sustainable syngas production through the simultaneous utilization of two major greenhouse gases.