Three Phase Electro-catalysis: a Step Forward for Polymer-grade Ethylene Purification (Chemistry)

In a study published online in Nature Catalysis, Prof. ZHANG Tierui from the Technical Institute of Physics and Chemistry (TIPC) of the Chinese Academy of Sciences, Prof. WANG Haotian from Rice University, and the collaborators, achieved high performance electrochemical acetylene reduction at room temperature. Their strategy shows special advantages in energy and atomic economics when compared with conventional thermal hydrogenation strategy.  

Ethylene is crucial to petrochemistry industry. Industrial ethylene is from the cracking of hydrocarbons such as naphtha. Cracking products inevitably contain 0.5-2.0% acetylene impurities, which will poison Ziegler Natta catalyst used for ethylene polymerization and affect the quality of polymer products. Therefore, it is necessary to reduce the concentration of acetylene impurities to parts per million (ppm) before polymerization. 

The acetylene thermal hydrogenation is widely used to the acetylene selective conversion for the production of polymer-grade ethylene. However, it requires more than 100℃ of operational temperature and excessive hydrogen. Ethylene will be over-hydrogenated to ethane. 

The researchers in this study developed a ‘gas-solid-liquid’ three phase electro-catalytic acetylene reduction (EAR) system. Nanomaterial such as Cu/Cu2O derived from layered double hydroxides can be used as catalyst to realize the selective reduction of acetylene in ethylene rich feed gas at room temperature. 

The conversion rate of acetylene reached 99.9%, and the ethylene selectivity is over 90%. Acetylene concentration was reduced from 5000 ppm to less than 1 ppm. Core indexes (acetylene conversion, ethylene selectivity, hydrogen volume, reaction temperature and specific rate) of the EAR system outperform most of thermal hydrogenation investigations. 

The three phase electro-catalytic system only needs an electricity cost equals to 0.5% of the market price of ethylene. It is highly possible to become an alternative to existing acetylene conversion technologies for the production of polymer-grade ethylene.

Reference: Shi, R., Wang, Z., Zhao, Y. et al. Room-temperature electrochemical acetylene reduction to ethylene with high conversion and selectivity. Nat Catal (2021).

Provided by Chinese Academy of Sciences

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