Optimising nanoporous absorbents for hydrogen purification

Project: Project at a former HEI


Hydrogen is considered a promising alternative automotive fuel, as the only combustion products are carbon dioxide and water. In the petrochemical industry, hydrogen is a by-product which can be found in many process streams and which is sometimes burnt as waste. This project aimed at designing porous materials that can recover and purify hydrogen for industrial gas streams. The different molecules present in a process stream interact differently with the internal surface of the porous solids (this process is called adsorption) and can therefore be selectively removed. For this project, we assessed using metal-organic frameworks (MOFs), materials synthesised in a building-block approach from corner units and linkers. The properties of MOFs can be changed by using different building blocks, offerering the possibility to fine tune the interactions between the gas molecules and the surface.

In this project we have studied MOFs tailored to hydrogen purification. For this, we used an integrated approach that combined skills from chemistry and chemical engineering, including the computer simulation of the synthesis of MOFs and of their adsorption performance, the actual synthesis of the materials, and the evaluation of their structure and their performance under industrially relevant conditions.

In addition to the technical objectives of the project, two researchers were trained who are now capable of carrying out research at the important interface between chemistry and chemical engineering. The researchers have learnt how chemistry and chemical engineering research is integrated effectively and therefore are able to work effectively in mixed teams of scientists and engineers.

Key findings

1) Developed methodology to predict what MOF structure forms under different synthesis conditions.
2) We showed that the ideal adsorbed solution theory (IAST) is generally accurate for MOFs. Where we find IAST is less accurate, deviations result from both mixture effects, in the form of nonidealities in the adsorbed phase, and characteristics of the adsorbent structures. In terms of the MOF structure, departures from IAST are a consequence of heterogeneities both on the scale of the unit cell and on shorter length scales, whereby competition for adsorption sites has a strong influence.
3) We integrated molecular simulation results into the process simulation of a pressure swing in a multi-scale approach. Our results show that only looking at equilibrium properties to assess MOFs is not enough but that break-through curves need to be considered as well to identify promising structures.
Short title£306,131.00
Effective start/end date1/06/0831/05/12