Acetylene hydrogenation to ethylene (AHE) in combination with acetylene production from coal pyrolysis is considered as a promising alternative to the traditional petroleum-based ethylene production route. However, thermocatalytic AHE (T-AHE) process often suffers from high temperatures (100-300 ℃) and high consumption of molecular hydrogen (H2).
Recently, a research group led by Prof. DENG Dehui and Assoc. Prof. YU Liang from the State Key Laboratory of Catalysis realized a new process of acetylene hydrogenation to ethylene by directly using water as hydrogen source (WAHE) and low-cost CO as oxygen acceptor over a Au/α-MoC catalyst.
This study was published in Nature Catalysis on September 28.
Acetylene hydrogenation to ethylene by water at low temperature on a Au/α-MoC catalyst (Image by HUANG Rui)
The hydrogenation of acetylene can proceed by a H2-based thermocatalytic route or H2O-based electrocatalytic route. The thermocatalytic AHE is energy
demanding due to the requirement of relatively high temperature and H2 consumption, since H2 is also industrially produced by energy-intensive processes such as steam methane reforming (SMR) and water gas shift (WGS) reaction.
The electrochemical AHE (E-AHE) process is advantageous as it directly uses electrochemically-generated active hydrogen species from water to hydrogenate acetylene without involving the unnecessary formation of H2.
The WAHE process delivered over 99% acetylene conversion and high ethylene selectivity of 83% at 80 ℃.
Mechanistic studies revealed that in-situ generated hydroxyl species from water dissociation at the boundary of Au and α-MoC, serving as mild reductants, enabled the selective semi-hydrogenation reaction with residual O removed by CO. This process circumvents H2 consumption in the classical route and opens avenues for energy-efficient acetylene hydrogenation by water at low temperature.
This work was supported by the National Key R&D Program of China, the National Natural Science Foundation of China and the Strategic Priority Research Program of CAS.
