Durán, P. Aragüés-Aldea, P. González-Pizarro, R. Mercader, V. D. Cazaña, F. Francés, E. Peña, J. A. Herguido, J. Biogas upgrading through CO2 methanation in a polytropic - distributed feed fixed bed reactor Catal. today 10.1016/j.cattod.2024.114849 2024 2024