Metal Organic Framework separates acetylene from ethylene

New adsorbent material holds great potential for industrial separations

4 June 2015

A new microporous metal-organic framework (MOF) holds a promise for the industrially relevant removal of acetylene from acetylene/ethylene mixtures. Professor Rajamani Krishna of the Van 't Hoff Institute for Molecular Sciences (HIMS) contributed to an international study on the novel MOF, published this week in Nature Communications. The publication follows two recent review articles by Krishna in the field of diffusion and separation.

Ethylene is an essential raw chemical, widely used to produce polymers and other useful chemicals. When produced it gets contaminated with a small amount of acetylene (about 1%). This should be reduced since acetylene has a deleterious effect on end products of ethylene. It can for instance poison a polymerization catalyst and decrease the quality of the resulting polyethylene.

Current acetylene removal methods are energy consuming and costly, but the emerging microporous metal-organic frameworks (MOFs) could provide an interesting alternative.MOFs consist of metal ions combined with organic linker molecules to form highly structured porous molecular architectures. The pores can be straightforwardly and rationally tuned to enforce their size selective sieving effects. Furthermore the pore surfaces can be readily functionalized to induce preferential interactions with specific molecules.

International team

All this makes MOFs an important gas separation tool, which has already been explored in numerous studies. The ethylene/acetylene separation, however, has not yet been fully explored. An international research team with contributors from China, Saudi Arabia, The Netherlands and the USA, coordinated by Banglin Chen of the University of Texas at San Antonio, now presents a new type of MOF that holds great promise for precisely this application.

UTSA-100 Metal Organic Framework

UTSA-100 Metal Organic Framework for removal of acetylene from ethylene/acetylene mixtures. At the left the sieving channel structure is shown, where the channels have a diameter of about 0,43 nanometer. At right the molecular structure of the 'cages' in between the channels is shown. These cages have a diameter of 0,4 nanometer and an are able to take up acetylene molecules through an 'entrance' of 0,33 nanometer.

The pores of this so called UTSA-100 MOF take up much more acetylene than ethylene and functional amine groups on the pore surface further enforce the interactions with acetylene molecules. The excellent acetylene removal performance of the new MOF has been established by means of experiments, analysis and molecular simulation studies. HIMS professor Rajamani Krishna contributed with the mathematical modelling of the separation performance.

Review articles

Krishna's contribution to metal-organic framework research follows from his continuous focus on improving technologies related to reaction and separation. He is an internationally recognized expert in the investigation of physico-chemical phenomena at the molecular and microscopic levels. His unifying concepts in these fields have led to significant improvements in various chemical process technologies.

Recently Krishna published two important reviews articles in renowned scientific chemistry journals. In Chemical Society Reviews he reported on "Uphill diffusion in multicomponent mixtures". The journal Physical Chemistry Chemical Physics published his perspective on "Separating mixtures by exploiting molecular packing effects in microporous materials"

Publications

Tong-Liang Hu, Hailong Wang , Bin Li, Rajamani Krishna et.al.: Microporous metal-organic framework with dual functionalities for highly efficient removal of acetylene from ethylene/acetylene mixtures. Nature Communications Published online 4 June 2015 DOI: 10.1038/ncomms8328

Rajamani Krishna: Uphill diffusion in multicomponent mixtures, Chem. Soc. Rev., 2015,44, 2812-2836 DOI: 10.1039/C4CS00440J

Rajamani Krishna: Separating mixtures by exploiting molecular packing effects in microporous materials, Phys. Chem. Chem. Phys., 2015,17, 39-59 DOI:10.1039/C4CP03939D

Published by  HIMS