Scheme 2.

Fossil carbon can be converted to oxalic acid via four pathways: (a) naphtha can be converted to ethylene glycol (via ethylene), which can be oxidized to oxalic acid; (b) propylene is obtained from naphtha cracking and can be converted to oxalic acid; (c) fossil carbon is converted to CO in a gasification process, which can be converted to oxalic acid via the dialkyl oxalate process; and alternatively (d) CO can be converted to formate, which is turned into oxalic acid using formate coupling followed by an acidification step.