# Study on Organo-Silica-Derived Membranes Using a Robeson-like Plot

## TL;DR

This study evaluates organo-silica membranes for CO2 separation at high temperatures using a Robeson-like plot and provides insights into their performance and structure.

## Contribution

The paper introduces a standardized framework for comparing organo-silica membranes using a Robeson-like plot and a method for microstructure assessment.

## Key findings

- A microporous membrane layer was prepared using BTESE and characterized for CO2/N2 separation.
- Temperature-dependent permeances and driving forces were analyzed to distinguish permselectivity and separation factors.
- A method for microstructure assessment based on diffusion mechanisms was developed.

## Abstract

For industrial CO2 utilization, the supply of concentrated CO2 within a continuous, high-volume stream at high temperatures remains a substantial requirement. Membrane processes offer a simple and efficient method to provide CO2 in this form. While several organo-silica-based membranes have been developed for CO2/N2 separation under these conditions, there is no standardized framework guiding comparability and optimization. Therefore, we present these membranes in a Robeson-like plot across various temperatures. Utilizing a standard 1,2-bis(triethoxysilyl)-ethane (BTESE) precursor and a simplified sol–gel method, we prepared a microporous membrane layer and characterized it for an exemplary comparison. This characterization includes key parameters for mixed-gas applications: (1) temperature-dependent single- and mixed-gas permeances to observe interactions, (2) the impact of the driving forces in mixtures (vacuum and concentration) to distinguish between permselectivity and the separation factor clearly, and (3) influence of the support structure to enable permeability calculations at elevated temperatures. Furthermore, a quick interpretation method for assessing the membrane’s microstructure is presented. A qualitative microstructure assessment can be achieved by analyzing the temperature dependencies of the three major diffusion mechanisms that simultaneously occur—Knudsen, surface, and activated diffusion.