Abstract <p>The partial oxidation of three mixtures CH₄/CO₂/N₂/O₂/Ar = 4.05/2.70/0/3.24/90.0, 4.05/1.35/1.35/3.24/90.0, and 4.05/0/2.70/3.24/90.0 vol/vol was investigated in an adiabatic compression reactor. In these mixtures, the biogas component ratios of CH₄/CO₂/N₂ = 60/40/0, 60/20/20 and 60/0/40 vol/vol, respectively. The detailed composition of the reaction products is determined in a wide range of conversion values, and the yield dependences of the reaction products are obtained. It is found that there is a sharp increase in the temperature and conversion of O₂ and CH₄ during ignition in a narrow range of compression ratios. Three regimes were found for CO₂: an increase in its content in the product mixture compared to the initial mixture under conditions of partial oxidation without ignition, an increase in the content during ignition, and a decrease in the content with further temperature increase. Increasing the content of CO₂ in the initial mixture prevents ignition and expands the region of partial oxidation without ignition, leads to a decrease in the conversion of initial components and the maximum hydrocarbon content in the product mixture. The partial oxidation of model biogas mixtures with a CO₂ content of 20 and 40% at high temperatures resulted in a synthesis gas with an H₂/CO ratio of ≈1.</p>