Methane pyrolysis is considered an auspicious approach for large-scale hydrogen production and simultaneous carbon capture, hereby contributing to a decarbonization of the chemical industry. While commonly pure methane or natural gas serve as feedstock, the usage of biogas may allow to exploit the pyrolysis process as a carbon sink. In this context, the present study reports on biogas pyrolysis in a high-temperature reactor at temperatures between 1000 and 1600 °C, residence times between 1 and 7 s, and molar CH₄:CO₂ ratios in the biogas between 1:1 and 4:1. Among these conditions, high residence times, a high CH₄ content, and the introduction of a carbonaceous fixed bed in the reactor benefit high educt conversion, H₂ selectivity , and solid carbon yield. Reference measurements with pure CH₄ feeds allowed for a carbon fixation of up to 95%, whereas a carbon yield of 75% was found for biogas feeds. The analysis of the reaction product distribution uncovered a consumption of CO₂ via dry reforming, water gas shift, and Boudouard reactions, resulting in a maximum H₂:CO ratio of 3:1 in the effluent gas stream. Herewith, the study underscores that optimized reactor operation parameters allow for maximizing CH₄ and CO₂ conversion as well as for achieving CO:H₂ ratios that are viable for further industrial applications, along with an efficient deposition of solid carbon.

Dry reforming of CH₄, either by co-feeding CH₄ and CO₂ from waste streams or directly using biogas, has potential as a CO₂-sink. This study investigates entirely thermal, catalyst-free dry reforming in a tubular flow reactor, aiming for syngas production with concurrent carbon capture. Kinetic modelling couples an elementary step-based gas-phase mechanism with a carbon deposition model. One-dimensional numerical simulations of the flow reactor are compared with experimental measurements. For this, operating conditions are widely varied, in particular temperature (1273 K to 1873 K), residence time (1 to 7 seconds), and CH₄:CO₂ molar feed ratio (1 to 4). Two temperature regimes are identified, with varying dominance of the reverse water-gas shift and CH₄ pyrolysis reactions. Above 1673 K, CO₂ is fully consumed, independent of residence time and feed composition. Optimized operating parameters result in a H₂/CO ratio of 2 in the effluent gas stream, e.g. as commonly desired for methanol and oxo-alcohol synthesis. Notably, under such optimized conditions, only a minor share of carbonaceous species remains in the gas-phase as hydrocarbons, while 33 % of the CH₄-borne carbon are transformed into CO and 48 % of CH₄-borne carbon is captured as solid carbon.