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Photosynthesis-inspired process makes raw materials chemicals: New strategy is cheaper, less energy-intensive than current industrial processes

Northwestern University chemists have drawn inspiration from plants to revolutionize how an important industrial chemical is manufactured.

In a first for the field, the Northwestern team used light and water to convert acetylene to ethylene, a widely used, very valuable chemical that is a key ingredient in plastics.

Although this conversion usually requires high temperatures and pressures, flammable hydrogen and expensive metals to drive the reaction, Northwestern’s photosynthesis-like process is much cheaper and less energy intensive. The new process is not only environmentally friendly, it also works incredibly well – successfully converts almost 100% of acetylene to ethylene.

“In industry, this method requires energy-intensive processes that require high temperatures, an external supply of flammable hydrogen gas and materials containing precious metals, which are expensive and difficult to obtain,” said Francesca Arcudi of Northwestern, co-author of the study. . “Our new strategy solves all these problems at once. It uses light and water instead of high temperatures and hydrogen. And instead of expensive metals, we naturally use abundant, inexpensive materials.”

The resulting strategy worked shockingly well. While the current industrial process results in 90% selectivity for ethylene, the northwestern method has 99% selectivity for ethylene.

“This is important because it is a raw material chemical with high economic value,” said Northwestern Luka Ðorđević, co-author of the study. “The more you can produce without waste, the better.”

The study will be published on Thursday (June 9) in the journal Natural chemistry. It is the first report of researchers using light to convert acetylene to ethylene.

This article is the result of a collaboration between Emily Weiss and Samuel I. Stupp and their joint effort as part of the Center for Bio-Inspired Energy Science (CBES) at Northwestern. Weiss, a professor of chemistry at Northwestern’s Weinberg College of Arts and Sciences, is the paper’s corresponding author. Arcudi is a postdoctoral fellow at Weiss’s laboratory. Ðorđević is a postdoctoral fellow at Stupp’s laboratory. Stupp is a board professor of materials science and technology, chemistry, medicine and biomedical technology at Northwestern, with appointments at Weinberg College, McCormick School of Engineering and Northwestern University Feinberg School of Medicine.

“At CBES, we strive to meet fundamental challenges by drawing inspiration from nature,” says Stupp, head of CBES. “Vitamin B12, one of the few naturally occurring organometallic cofactors, was used in this document as a source of inspiration to design our catalyst.”

As a precursor to 50-60% of all the world’s plastics, ethylene is a hot commodity. To meet the ever-increasing demand for the valuable chemical, the industry produces more than 200 million tons of ethylene per year.

To generate ethylene, chemists use steam cracking, an industrial method that uses hot steam to break down ethane into smaller molecules, which are then distilled into ethylene. However, the resulting chemical contains a small amount of acetylene, a contaminant that inactivates catalysts to prevent ethylene from being converted to plastic. Before the ethylene can be converted to plastic, the acetylene must be removed or converted to ethylene.

“The removal or conversion of acetylene to obtain pure ethylene is a process well known in the industry,” said Weiss. “The process has many problems, which is why the research world has tried to propose an alternative to this process. Producing polymer grade ethylene from carbon dioxide raw material is a desirable alternative, but this path is not sufficiently developed yet. Our strategy is a first and great step towards producing this important raw material chemical with the lowest possible energy footprint. “

In particular, an incredible amount of energy is required to reach the high temperatures and pressures required for a successful chemical reaction. It also requires expensive catalysts made of precious metals, such as palladium. And because the process is dependent on protons from hydrogen, which are produced from fossil fuels, it generates enormous amounts of carbon dioxide.

Northwestern’s strategy bypasses all of these issues. To convert acetylene to ethylene, Northwestern chemists replaced the palladium catalyst with cobalt, a cheaper, more abundant alternative. They also used room temperature and ambient pressure. Instead of heat, they used visible light. And finally, they replaced hydrogen with ordinary water as a source of protons.

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