Breaking the Ni loading-reducibility-dispersion dependence achieved by solid-state co-grinding

Abstract

The loading-dispersion-reducibility dependence has always been one of the most critical issues in the development of high-performance supported metal catalysts. Herein, up to 40 wt % NiO over ordered mesoporous alumina (OMA) was prepared by co-grinding the hybrid of template-containing OMA and Ni(NO₃)₂·6H₂O. Characterization results confirmed that the OMA mesostructure was still preserved even after loading NiO at a content as high as 40 wt %. More importantly, the reduction extent, dispersion, and average particle size of the Ni/OMA catalysts were maintained at ⩾ 91.0%, ∼13.5%, and ∼4.0–5.0 nm, respectively, when the NiO loading was increased from 20 to 40 wt %. The catalysts were evaluated for the CO methanation as a model reaction, and the similarly high turnover frequency of 24.0 h⁻¹ was achieved at 300 °C for all of the Ni/OMA catalysts. For the catalyst with the highest NiO loading of 40 wt % (40Ni/OMA), the low-temperature activity at 300 °C indexed by the space-time yield of methane (over \(325.8\ \text{mol}_{\text{CH}_{4}}\cdot \ {\text{kg}_{\text{cat}}}^{-1}\cdot \mathrm{h}^{-1}\)) was achieved, while the catalyst was operated without an observable deactivation for a time on stream of 120 h under severe reaction conditions of 600 °C and a very high gas hourly space velocity of 240000 mL·g⁻¹·h⁻¹. With these significant results, this work paves the way for a rational and controllable design of supported Ni catalysts by breaking the loading-dispersion-reducibility dependence and stabilizing Ni nanoparticles under harsh reaction conditions.