Coupling Conversion of CO₂ and <i>n</i>-Butane Over Modified ZSM-5: Incorporation of the Carbon from CO₂ into Hydrocarbon Products

Abstract

The coupling reaction of CO 2 and n-butane was conducted over different metal-modified (Mn, Zr, Ni, Ti, Zn) ZSM-5 catalysts. A high CO 2 conversion of 26.5% and n-butane conversion of 100% with the aromatics selectivity of 69.1% was achieved at a CO 2 to n-butane ratio of 0.95 over Zn/ZSM-5. CO 2 addition promoted BTX & olefin selectivity, while it inhibited alkane & A 9+ formation. A detailed analysis showed that 13% of the carbon atoms from CO 2 were incorporated in the generation of aromatic hydrocarbons. Oxygenated intermediates, such as aliphatic alcohol, aliphatic ketones, and substituted cyclopentenones, were detected sequentially with the increase of the reaction temperature. In addition, reverse Boudouard reaction, water gas shift reaction, and dry reforming also participated in the formation of CO over Zn/ZSM-5. Based on these findings and the detailed characterization results, a plausible mechanism of direct and indirect incorporation of carbon from CO 2 into aromatics was proposed for the coupling reaction.