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TWI expertise in novel solvent development

Connect no.172


Ionic liquid pilot plant for polymer waste recovery

Increasingly stringent environmental legislation is leading to the rapid phasing out of many familiar solvents resulting in growing interest in alternatives for a range of industrial processes. Many novel classes of solvent have achieved significant popularity in the last decade, including:

  • Ionic liquids
  • Bio-derived solvents
  • Gas expanded liquids
  • Supercritical fluids
  • Water-based systems

Within TWI, a core competency is being developed in the design and selection of 'green' solvents as replacements for conventional VOCs and as novel media in their own right. A three-year Technology Strategy Board-funded project has just been completed aimed at developing novel solvents for the separation of pure polymers from mixed waste.

The HiPerPol process uses highly selective yet cost-effective and biodegradable solvents to specifically extract polyethylene and PVC from mixed waste streams, resulting in recycled polymers comparable in purity and performance to virgin material. This elevates the utility and value of the recycled plastic as well as reducing both levels of non-biodegradable waste going to landfill and pressure on non-sustainable oil-derived feedstocks for polymer manufacturing. A second, EU-funded project due to begin this year will extend the approach by developing new, specific solvents for the recycling of polystyrene and polycarbonate.

The key to the design and selection of the right solvent lies in matching the solvent properties as closely as possible to the process requirements. To achieve this, TWI has access to unique solvent selection software, which can rapidly and accurately screen large numbers of solvents against multiple predetermined criteria such as solubility, boiling point, viscosity, toxicity and cost. In situations where no commercially available solvent fits the criteria, SOLFIT can be used as a design tool, to build a new solvent at the molecular level around the specified requirements.

TWI is also involved in the development of novel media for a range of high-value applications, including carbon dioxide capture from post-combustion exhaust gases, mineral extraction, anti-icing formulations and cleaning fluids.

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