Ethylene is by far the most widely utilized hydrocarbon in chemical industry and is the building block of most commercially available polymers, fibers and plastics. Worldwide production of ethylene increases every year, exceeding 150 million tones in 2016. The chemical process used in today’s industry, steam cracking, requires hydrocarbons to be heated to very high temperatures, whereas at a smaller scale, acetylene semi-hydrogenation to ethylene has been achieved via Pd-based catalysts in combination with promoters such as lead or organic ligands. Because of the scarcity and steep price of Pd, energetically favorable alternatives based on non-precious metals have been sought for decades; however, most of the newly developed catalysts are either less active or suffer from selectivity losses, namely over-hydrogenation and oligomerization.<br/>Here we present a pioneer computational work by means of periodic Density Functional Theory (DFT) methods that proves the potential of the electrochemical selective hydrogenation of acetylene to ethylene as a sustainable and low energy intensive alternative for the production ethylene. Notably, we find that exergonic semi-hydrogenation of acetylene to ethylene can be achieved under ambient conditions via a concerted reaction mechanism on 2D-catalysts based only on Earth-abundant elements, requiring an applied potential of only –0.25V vs NHE. Importantly, we also show that the undesired over-hydrogenation of ethylene to ethane is unfavorable, rendering this 2D-material as an extremely selective hydrogenation catalyst.<br/>The utilization of eart-abundant elements and the possibility to carry out this reaction under ambient conditions open the way to synthesizing ethylene with a low energy cost or environmental damage bound to the available synthetic route. Furthermore, the nature of the catalyst opens the possibility to an optimization of the yield and improvements on the reaction selectivity. Our DFT study also highlights the importance of ab-initio calculations in the rational design of selective hydrogenation catalysts, with the aim of contributing to the future design of novel catalysts with an improved catalytic performance.

Computational study of the selective hydrogenation of alkynes to alkenes on 2D materials

2019 Spring National Meeting

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