Formation of Hydrocarbons from the Reduction of Aqueous CO2 by Zero-Valent Iron

Abstract

The reduction of aqueous CO2 by zero-valent iron was studied in batch and column experiments. Ten hydrocarbons up to C5 were identified as products of the reduction process and were shown to have Anderson−Schulz−Flory (ASF) product distributions. A direct consequence of the ASF product distribution is that a significant mass of hydrophobic hydrocarbons may remain sorbed to the iron surface. Based on a reaction mechanism proposed for the electroreduction of aqueous CO2 with nickel electrodes, iron acts as both a reactant by corroding to supply electrons and as a catalyst by promoting the formation and growth of hydrocarbon chains. Water is also a reactant in the system. When iron is used to enhance the dechlorination of chlorinated organic compounds, the slow desorption of the hydrocarbon products may become the rate-limiting step in the reaction.