A new method for converting carbon dioxide from exhaust to ethylene

Minish Singh and his team at University of Illinois Chicago She found a way to convert carbon dioxide extracted from industrial exhaust into ethylene, a critical ingredient in making plastics. The team published their findings in Cell Reports Physical Sciences.

Rohan Sartapy, an engineering student at the University of California College of Engineering, is with a company that churns out humidity-assisted immigration2 capture unit. Image Credit: Jim Young / UIC Engineering

The UIC team’s method is the first to achieve nearly 100% use of carbon dioxide in making hydrocarbons, although researchers have been researching the possibility of converting carbon dioxide into ethylene for more than a decade.

Using electrolysis, their method converts the collected carbon dioxide gas into high-purity ethylene, with byproducts of other carbon-based fuels and oxygen.

Almost all the carbon dioxide captured2 Through this process, up to six tons of carbon dioxide are converted into one ton of ethylene. The process can be carbon negative using renewable energy because the system runs on electricity.

Singh claims that by lowering the total amount of carbon dioxide produced by the industry, his team’s method outperforms the net carbon target of current carbon capture and conversion methods.

It is net negative. For every 1 ton of ethylene produced, you take 6 tons of CO2 From specific sources that would otherwise be released into the atmosphere.

Minch Singh, Assistant Professor, Chemical Engineering, University of Illinois Chicago

In the past, attempts to convert carbon dioxide to ethylene have relied on reactors that produce ethylene from the source stream for carbon dioxide emissions.

Under these conditions, only 10% of carbon dioxide2 Emissions are usually subject to ethylene conversion. Later, in an energy-intensive process that frequently uses fossil fuels, the ethylene must be separated from the carbon dioxide.

The UIC method involves passing an electric current through a cell divided in half, one half filled with collected carbon dioxide and the other with a water-based solution.

The electrocatalyst pulls the charged hydrogen atoms from the water molecules to the other side of the unit, divided by a membrane. It is mixed with charged carbon atoms of carbon dioxide molecules to form ethylene.

Ethylene is the world’s third-highest source of carbon dioxide among manufactured chemicals, after cement and ammonia. Ethylene is used to make chemicals for antifreeze, medical sterilizers, vinyl siding for homes, plastic products for the packaging, agricultural and automobile industries.

A procedure called steam cracking, which requires significant heat, is usually used to produce ethylene. For every ton of ethylene produced, cracking results in about 1.5 metric tons of carbon emissions.

More than 260 million tons of carbon dioxide are emitted annually globally due to the annual production of about 160 million tons of ethylene.

The electrolysis method allowed the UIC researchers to manufacture other carbon-rich compounds useful for industry in addition to ethylene. Significant solar energy conversion efficiency has also been achieved, with 10% of the energy from solar panels being diverted directly to the manufacture of carbon products.

This is much higher than the modern standard of 2%. The solar energy conversion efficiency of all the ethylene they produced was about 4%, about the same as the rate of photosynthesis.

Journal reference:

Prajapati, A.; et al. (2022) CO2– Free of high purity ethylene from electrocution of carbon dioxide2 4% from solar energy to ethylene and 10% from solar energy to carbon. Cell Reports Physical Science. doi: 10.1016/j.xcrp.2022.01053.