Dry Reforming of Methane (DRM) over Hydrotalcite-Based Ni-Ga/(Mg, Al)Ox Catalysts: Tailoring Ga Content for Improved Stability

Abstract

Dry reforming of methane (DRM) is a promising way to convert methane and carbon dioxide into syngas, which can be further utilized to synthesize value-added chemicals. One of the main challenges for the DRM process is finding catalysts that are highly active and stable. This study explores the potential use of Ni-based catalysts modified by Ga. Different Ni-Ga/(Mg, Al)Ox catalysts, with various Ga/Ni molar ratios (0, 0.1, 0.3, 0.5, and 1), were synthesized by the co-precipitation method. The catalysts were tested for the DRM reaction to evaluate their activity and stability. The Ni/(Mg, Al)Ox and its Ga-modified Ni-Ga/(Mg, Al)Ox were characterized by N2 adsorption–desorption, Fourier Transform Infrared Spectroscopy (FTIR), H2-temperature-programmed reduction (TPR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Raman techniques. The test of catalytic activity, at 700 °C, 1 atm, GHSV of 42,000 mL/h/g, and a CH4: CO2 ratio of 1, revealed that Ga incorporation effectively enhanced the catalyst stability. Particularly, the Ni-Ga/(Mg, Al)Ox catalyst with Ga/Ni ratio of 0.3 exhibited the best catalytic performance, with CH4 and CO2 conversions of 66% and 74%, respectively, and an H2/CO ratio of 0.92. Furthermore, the CH4 and CO2 conversions increased from 34% and 46%, respectively, when testing at 600 °C, to 94% and 96% when the catalytic activity was operated at 850 °C. The best catalyst’s 20 h stream performance demonstrated its great stability. DFT analysis revealed an alteration in the electronic properties of nickel upon Ga incorporation, the d-band center of the Ga modified catalyst (Ga/Ni ratio of 0.3) shifted closer to the Fermi level, and a charge transfer from Ga to Ni atoms was observed. This research provides valuable insights into the development of Ga-modified catalysts and emphasizes their potential for efficient conversion of greenhouse gases into syngas.