Performance Study of Ni/Si-MCM-41 Catalysts, Synthesized with Different Silica Sources, and their Application on Methane Dry Reform to Produce Green Hydrogen

Abstract

The present work carried out an extensive and deepened study regarding the physicochemical characteristics of two Si-MCM-41-type supports, synthesized employing two distinct silica precursors, tetraethyl orthosilicate (TEOS) and rice husk ash (RHS), with the dispersion of nickel on the surface of the catalytic support. The direct influence of the active phase dispersion was analyzed, making a relationship with the formation of coke and with its performance on methane dry reform (DRM). The catalysts were prepared with 5, 10, and 20% (m/m) of Ni by wet impregnation method (with excess solvent), calcined at 800 ºC for 6 h, and characterized by the techniques of scanning electron microscopy and energy dispersive spectroscopy (SEM/ EDS), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET)/Barret-JoyerHalenda (BJH), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), temperature-programmed ammonia desorption (TPD-NH3), and H2-temperature-programmed reduction (TPR). The DRM experiments were carried out at 800 °C for 24 h with a 1:1 CH4:CO2 molar ratio. Analyzes of gaseous products were performed in gas chromatography (GC) and the coke produced was estimated by temperature-programmed oxidation (TPO). The best reaction results were obtained for catalysts with 20% nickel, which were selective and stable within 24 h of reaction. Comparing the TEOS and RHS catalysts for 20% Ni, the DRM results were very similar. The catalysts on RHS support demonstrated a significant low formation of coke, which can be considered negligible in a 24 h reaction.