Science

Scientists convert plastics into useful chemicals using sunlight

New research by chemists at the Nanyang Technological University, Singapore,  have discovered this novel solution by mixing plastics with a catalyst within a solvent, which can then harness light from sunlight and convert them into formic acid, useful in producing electricity.

The catalyst that they used was Vanadium, commonly used in steel alloys for vehicles and aluminum alloys for aircrafts, reported NTU Assistant Professor Soo Han Sen from the school of physical and mathematical sciences.

Their study was published in Advanced Science.

They found that the Vanadium based catalyst is efficient in breaking down the carbon-carbon bonds in plastics like polyethylene in about 6 days, leading to the creation of formic acid, a naturally occurring preservative and antibacterial agent, which can also be used to generate energy.

Soo Han Sen reported that this was the first ever process that can completely break down plastics using just sunlight and a catalyst which does not contain any heavy metals.

The existing mechanism for the disposal of plastic consists of incinerating them which would produce greenhouse gases and the residual ash being transported to a landfill in Semakau, which is reckoned to run out of space by 2035.

Developing efficient means of energy with zero waste by turning them into reusable energy is a part of NTU Smart Campus’ vision.

This Vanadium based catalyst is called a photocatalyst, as it uses light to drive the chemical reactions as opposed to other catalysts that require copious amounts of heat to drive the chemical reactions, which is usually produced by burning fossil fuels, contributing to the amount of CO2 in the atmosphere.

With the existing panoply of catalysts made from expensive and toxic metals such as platinum, palladium and others, vanadium offers many advantages as it’s low cost and environment friendly.

While this is not the first endeavor to convert waste plastic into usable energy, the others are marred by complex steps in between involving too much of reagents and being impracticable to scale up.

One such approach being the use of Cadmium as a catalyst to convert plastic into energy by combining it with water and sunlight in a process called photoreforming, however the toxicity of the catalyst used is a concern. Also, other methods involve treating plastic with harsh chemical reagents that are unsafe to handle.

Most non-biodegradable plastics require high temperatures for the Carbon-Carbon bonds to be broken down however the new Vanadium based catalyst bonds with an alcohol group and with the energy from sunlight, is able to unravel the molecule thus breaking it down without the need for higher temperatures.

The actual experiment consists of dissolving plastic at 85 degree Celsius in a solvent before the catalyst, in a powdered form, is dissolved and then the solution is exposed to sunlight for a few days where they were able to observe their photocatalyst breaking down the robust Carbon-Carbon bonds in over 30 different compounds which clearly demonstrates the usefulness of the low cost and environment friendly catalyst.

The research team is now scaling up the process that would allow the plastics to be broken down into other chemicals like Hydrogen gas, which could also be used as fuel.

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