Hydrogen Production through Distinctive C−C Cleavage during Acetic Acid Reforming at Low Temperature

A water-induced process for C−C bond cleavage during acetic acid reforming is reported in this research, which make acetic acid convert into methanol and formic acid (CH₃COOH+H₂O→CH₃OH+HCOOH) with high selectivity. This process could sharply reduce carbon monoxide and methane production from C−C bond direct cleavage during acetic acid reforming.

Abstract

Acetic acid reforming is a green method for sustainable hydrogen production owing to its renewable source from biomass conversion. However, conventional acetic acid reforming would produce various byproducts, including CO, CH₄ and so on. Here, we develop a distinctive method for selective hydrogen production from C−C directional cleavage during acetic acid reforming. Completely different from conventional acetic acid reforming process, acetic acid would react with water over organoruthenium catalyst during its C−C cleavage at low temperature, then produce methanol and formic acid (CH₃COOH+H₂O→CH₃OH+HCOOH). Lastly, methanol and formic acid could further decompose into hydrogen and carbon dioxide over organoruthenium selectively. As a result, there is little CO and CH₄ produced in the first step of C−C bond cleavage during acetic acid reforming at 100 °C. Hydrogen production rate is up to 26.8 mol_H2/(h⁻¹*mol⁻¹ _Ru) at 150 °C through a tandem catalysis. A mechanism for C−C cleavage of acetic acid is proposed based on intermediate product analysis and density functional theory (DFT) calculation. Firstly, the C−C single bond was transformed into C=C double bond by dropping one H atom to organoruthenium. Then the coming H₂O molecule reacted with the C=C bond by an addition reaction, forming methanol and formic acid. This research not only proposes distinctive reaction pathway for hydrogen production from acetic acid reforming, but also provides some inspiration for selective C−C bond cleavage during ethanol reforming.

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