A comparative investigation of equimolar Ni-, Ru-, Rh- and Pt-based composite structured catalysts for energy-efficient methane reforming

Abstract

Hydrogen as an optimal fuel for mobile and local fuel cell-based power generators creates a request for effective on-board fossil fuel transformation to hydrogen-rich syngas. Structured catalysts based on carriers with high thermal conductivity can improve fuel conversion and decrease external heat input to a reformer through intensification of temperature distribution in the reforming processes. In this work, carriers of the structured catalysts were made from metal grids consisting of Fe, Cr, and Al alloy. Aiming to compare a catalytic activity per a one active metal atom four Me/Ce0.75Zr0.25O2/Al2O3/FeCrAlloy (Me = Ni, Ru, Pt, and Rh) catalysts with similar molar content of an active metal were prepared. The catalysts were characterized by transmission (TEM) and scanning electron microscopies (SEM), X-Ray diffraction analysis (XRD), and X-Ray photoelectron spectroscopy (XPS) before and after catalytic tests. Investigation of the catalysts’ effectivities in methane steam reforming (MSR) showed that the performances change in the order Rh > Ru > Pt > Ni. The Rh-based structured catalyst provided thermodynamic equilibrium product distribution of MSR products at a relatively low temperature of 600 °C and high flow rates. Hydrogen content in the syngas obtained in MSR over Rh-based structured catalyst was up to 70.3 vol% at the weight hour space velocity (WHSV) of 290 700 Nml⋅gacc−1⋅h−1. Investigation of methane autothermal reforming (MATR) over Pt- and Rh-based structured catalysts at 700 °C approved better performances of the Pt-based catalyst for this process. The syngas obtained in MATR over the Pt-based catalyst contained up to ∼ 40 vol% of H2 and 7.4 vol% of CO with a H2/CO molar ratio of ca. 5.5. The optimal conditions for MATR over the Pt-based catalyst were selected and the catalyst stability in long-term reforming was approved. The developed mathematical model for the description of MATR over Pt-based catalyst correlates well with the experimental data and can be used for scale-up of the process.