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Unipd Study Discovers How to Convert Acetylene into Ethylene Using Sunlight

13.11.2024

In the photo: Photocatalytic mixtures illuminated by visible light in the Unipd laboratories of Arcudi and Luka Ðorđević. One molecule acts as a photosensitizer by absorbing light and, in doing so, promotes the chemical reaction carried out by another molecule that acts as a catalyst.

In the study titled "Photocatalytic Semi-Hydrogenation of Acetylene to Polymer-Grade Ethylene with Molecular and Metal–Organic Framework Cobaloximes" published in the prestigious journal "Advanced Materials," the international research team coordinated by Francesca Arcudi and Luka Ðorđević from the Department of Chemical Sciences at the University of Padua and Joe Hupp from Northwestern University (Illinois, USA) reported an efficient strategy to convert acetylene into ethylene using sunlight, representing a sustainable alternative to the process used in industry.

"We discovered that a class of cobalt-based molecules, a non-noble metal, can reduce acetylene to ethylene using light as an energy source. With our system, compared to the one used in industry, it is possible to perform this important chemical transformation at room temperature using inexpensive materials," explains Francesca Arcudi, corresponding author of the study and professor at the Department of Chemical Sciences at the University of Padua.

The team found that the formation of a particular species of cobalt is responsible for the high performance of their systems.

"Thanks to the use of light, we have generated highly reactive and selective cobalt hydrides for this reaction. Moreover, it is important to emphasize that we have been able to develop materials that can also be recycled," adds Anna Fortunato, research fellow at the Department of Chemical Sciences and co-first author of the article.
Ethylene is the most important organic chemical in modern industry: with an annual production reaching 200 million tons, its applications range from the production of about 60% of all plastics to agricultural management, and the synthesis of numerous chemical products and organic compounds. Today, ethylene is mainly produced through the petrochemical pyrolysis of hydrocarbons, an industrial process that introduces acetylene impurities that limit the direct use of the produced ethylene. For this reason, in industry, ethylene must first be purified from acetylene in a transformation process that currently presents significant sustainability issues as it requires high temperatures and noble metals – expensive and difficult to source – as catalysts. Despite the progress made, these traditional strategies for acetylene conversion to ethylene still have relatively low selectivity (i.e., acetylene is not only converted to the desired ethylene, but part of it is also converted to undesired products).

Francesca Arcudi and Luka Ðorđević were the first, in 2022, to demonstrate a sustainable alternative to this industrial reaction using light, and the newly published study represents a significant step forward in terms of efficiency and selectivity towards the real industrial implementation of this revolutionary light-driven process. The system reported by the group of young researchers from Padua has shown surprising results: compared to traditional processes that achieve a selectivity of about 85% for ethylene with a 90% conversion of acetylene, this new system using light reaches a selectivity of over 99.9% for ethylene with complete acetylene conversion. Such efficiencies and selectivity were achieved in less than an hour of irradiation.

"The high efficiencies reported in this study, in addition to making our system a sustainable alternative to the current ethylene purification process, also open new perspectives for producing pure ethylene directly from acetylene using sunlight, a clean, inexhaustible, and renewable energy source," explains Luka Ðorđević, corresponding author of the study and professor at the Department of Chemical Sciences at the University of Padua.
The search for new molecules and materials is crucial to facilitating the transition to a more sustainable chemical industry.