Biogas upgrading through CO2 methanation in a polytropic - distributed feed fixed bed reactor

• Published in: Catalysis today 2024-10, Vol.440, p.114849, Article 114849
• Main Authors: Durán, P., Aragüés-Aldea, P., González-Pizarro, R., Mercader, V.D., Cazaña, F., Francés, E., Peña, J.A., Herguido, J.
• Format: Article
• Language: English
• Subjects: Biogas upgrading; CO2 methanation; Distributed feeding; Improved selectivity; Ni-Mn catalyst; Power to gas
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2024.114849

Methanation of the CO2 contained in a biogas stream has been experimentally analyzed in a fixed bed reactor with a Ni-Mn catalyst, evaluating the effect of feeding reactants distributed throughout the bed. The performance of different feeding configurations (conventional cofeeding and others implying a lateral distribution of one of the reactive streams) has been analyzed for different nominal temperatures T (250–400 ºC) and weight-related space velocities WHSV (47.71–6.63 gCO2 gcat-1 h-1), always keeping a H2: CO2 ratio of 4:1, and a CH4:CO2 ratio of 7:3. For identical WHSV, the lateral biogas distribution (Poly-Biogas feeding configuration) always showed the best results in terms of activity (higher conversion at the same temperature) and selectivity (lower selectivity to CO in iso-conversion). These better results agree with what was observed in a previous work in methanation of CO2 (i.e., without methane in the feed). In that work, CO2 was distributed along the catalytic bed by several lateral feeds (Poly-CO2). When T was kept constant and WHSV was varied, the reactor fed with distributed biogas (Poly-Biogas), again confirmed its higher efficiency and better selectivity for biogas upgrading (i.e., higher CH4 content). Furthermore, by adopting a Poly-Biogas (or poly-CO2) feeding configuration, a more homogeneous temperature profile was achieved along the bed avoiding the severity of hot spots appearance. In contrast, the lateral distribution of hydrogen (Poly-H2) always led to similar or worse results than those for the conventional co-feeding configuration. [Display omitted] •An alternate way, besides catalysts, to boost performance of CO2 methanation reactors•Proven beneficial influence of side distributed feed on biogas upgrading process•Side feeding of biogas results in enhanced CO2 conversions and selectivities to CH4•Thermal gradients along the bed length can be reduced by distributed feeding