A process for preparing one or more reaction products, in which a first methane-rich feed stream is subjected to a partial oxidation process and/or an autothermal reforming process and a second methane-rich feed stream is subjected to a steam reforming process, in which a first synthesis gas-containing output stream is formed from the first methane-rich feed stream and a second synthesis gas-containing output stream is formed from the second methane-rich feed stream and these synthesis gas streams are used to form a collective synthesis gas stream and fluid from the collective synthesis gas stream is subjected to a molecular weight-increasing reaction in a synthesis feed stream to obtain a synthesis output stream comprising carbon dioxide and the reaction product(s). At least one carbon dioxide-rich first recycle stream is formed from fluid from the synthesis output stream and fluid from the first recycle stream is subjected to the steam reforming process.