Insights into the Zn Promoter for Improvement of Ni/SiO2 Catalysts Prepared by the Ammonia Evaporation Method toward CO2 Methanation

Abstract

As a pure combustible gas with a high calorific value, methane has long been favored, and that is why the CO2 methanation reaction is attracting more and more attention. However, it is still challenging for this reaction due to the chemical inertness of CO2 molecules, poor reaction efficiency at low temperatures, catalyst sintering at high temperatures, and carbon monoxide toxicity. Herein, the ammonia evaporation method was utilized to synthesize a series of Zn-modified Ni/SiO2 catalysts with high surface area and high dispersity of active metals. The 80Ni-Zn/SiO2 catalyst with an appropriate Ni/Zn molar ratio of 80:1 exhibited a high-performance breakthrough with a CO2 conversion greater than 80% at 300 °C, good stability for 40 h at 310 °C, and a gas hourly space velocity of 18,000 mL·g–1·h–1. These catalysts were further characterized by using a series of methods like in situ diffuse reflectance infrared Fourier transform spectroscopy to investigate the structural properties and potential reaction pathways. The effect of the Zn promoter on the Ni/SiO2 catalyst for CO2 methanation has been well investigated, namely, improving Ni dispersion and enhancing the H2 adsorption. The findings demonstrate the broad availability, affordability, and remarkable high-performance practicability of the raw ingredients for the production of Ni-based catalysts for commercial applications.