Electrochemical-Thermochemical Cascade System for the Sustainable Conversion of Crude Acetylene to C6+ Esters.

Acetylene (C2H2), a critical chemical feedstock derived from natural gas or coal, faces sustainability challenges due to high CO₂ emissions from conventional production methods. These emissions not only contribute to carbon footprints but also hinder the upgrading of C2H2. Herein, a two-step electrochemical and thermochemical cascade system that directly converts CO₂-contaminated crude acetylene into C6+ esters is proposed. In the first step, CO₂ from crude acetylene is captured by hydroxide to form bicarbonate, which is subsequently released in situ at the cathode under electrolysis. Using a Ni single-atom catalyst, CO is efficiently generated with a Faradaic efficiency of 97.8 ± 0.84% at 100 mA cm-2. The generated CO then reacts with acetylene in the second step, where a Pd-based catalyst enables the production of dimethyl butenedioate at 7.83 ± 0.31 mmol L-1 h-1 and selective dimethyl maleate synthesis (>65% selectivity). Furthermore, replacing methanol with ethanol or butanol in the carbonylation step allows for tunable synthesis of diethyl or dibutyl butenedioate, demonstrating broad applicability. Techno-economic analysis indicates a 46.9% cost reduction compared to the traditional reverse water-gas shift system, attributed to lower energy demands and eliminated separation steps. This work provides a green strategy for valorizing low-value acetylene streams while mitigating CO₂ emissions.