Scientists at the Georgia Institute of Technology and ExxonMobil, the world’s largest publicly traded international oil and gas company, have developed a plastic manufacturing process that could reduce energy costs by $2 billion (£1.55 billion) and carbon dioxide emissions by as much as 45 million tons (US).[1]

Molecular-level filtration

Currently, the industrial plastic manufacturing process separates out para-xylene, the starting chemical of plastics and polymers, from complex hydrocarbons using either high-energy crystallisation or adsorption with distillation.

The new process presses the source material – generally derived from fossil fuels[2] – through a membrane that has molecular-sized holes. The membrane sieves out all the useless chemical compounds (which are known as aromatics) and separates out the para-xylene.

A microscopic membrane

The membrane is the key component of the new process, and is capable of dividing chemicals that are no larger than a nanometer.

The scientists at ExxonMobil and Georgia Tech then integrated the membrane into a new ‘organic solvent reverse osmosis process’, according to the ExxonMobil website.

“In effect, we’d be using a filter with microscopic holes to do what an enormous amount of heat and energy currently does in a chemical process similar to that found in oil refining,” said Mike Kerby, corporate strategic research manager at ExxonMobil.

What is reverse osmosis?

For anyone who did GCSE or O Level biology, osmosis is a term that may trigger a few memories.

In fact, GCSE students are still learning about it today, as evidenced by the BBC Bitesize website.[3] According to its Biology resource pages:

“Osmosis is the special case of diffusion involving water molecules. Water molecules move from areas of high water concentration to areas of low water concentration through a selectively permeable membrane.”

Reverse osmosis, in that case, is when molecules (it doesn’t have to be water) move from an area of low concentration to an area of high concentration, through a selectively permeable membrane.

Reverse osmosis is already used to desalinate seawater, but the ExxonMobil and Georgia Tech team believe that this is the first case where liquid hydrocarbons have taken the place of water in the process.

“By applying pressure at room temperature, the membrane is able to concentrate para-xylene from a mixture at high rates and low energy consumption relative to state-of-the-art membranes,” said Ryan Lively, an assistant professor in Georgia Tech’s School of Chemical & Biomolecular Engineering and the lead researcher. “This mixture could then be fed into a conventional thermal process for finishing, which would dramatically reduce total energy input.”

Energy efficient and ecological

Although the new process is not yet ready for commercialisation, if adopted, it could save the plastic manufacturing industry £1.55 billion a year in energy costs, and reduce annual C02 output by 45 million tons (US) – which, according to ExxonMobil’s website, is how much C02 is produced annually by around five million US homes.

[1] http://news.exxonmobil.com/press-release/exxonmobil-and-georgia-tech-innovation-could-lead-significant-cuts-chemical-manufactur

[2] https://www.plasticsmakeitpossible.com/about-plastics/types-of-plastics/what-are-plastics/

[3] http://www.bbc.co.uk/bitesize/standard/biology/investigating_cells/cells_and_diffusion/revision/4/

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