Manganese coordination polymer separates xylene isomers

Researchers have developed an innovative, energy efficient process to purify the three xylene isomers – ortho-, meta- and para-xylene. The method makes use of manganese coordination polymers, a stable and low-cost material that selectively adsorbs, recognises and separates the three molecules, in both vapour and liquid phases.

The three xylene isomers ‘have very similar molecular size, shape and physical properties, including boiling points’, explains co-lead author Jing Li from Rutgers University, US. Therefore, separating them is usually extremely complicated. The boiling points of ortho-, meta- and para-xylene fit within a small range of temperatures – from 138.4 to 144.5°C – which makes distillation difficult and energy intensive. Adsorbents are also average at separation. The three isomers have ‘similar affinity towards conventional adsorbents like zeolites, leading to low selectivity’, adds Li. ‘Typical industrial [systems need] 24 separation columns to yield para-xylene with the required purity,’ she explains.