Iliana Kyriazidou has developed ultra-thin zeolite membranes capable of separating gas mixtures with high precision – a step toward cleaner and more energy-efficient production of biogas and natural gas.
20 November 2025
Zeolite membranes make gases cleaner and greener – new doctoral thesis supports improved biogas and natural gas upgrading
Gas mixtures, such as carbon dioxide and methane, are difficult to separate, but new research at Luleå University of Technology shows how ultra-thin zeolite membranes can make the process more efficient. In her doctoral thesis, Iliana Kyriazidou presents new insights that could lead to cleaner biogas and natural gas production.
In her research, Iliana investigates the potential of small-pore zeolite membranes – specifically CHA and DDR types – for separating gas mixtures, such as CO2/CH4, H2/CH4, and synthetic natural gas with many more heavy hydrocarbon components apart from CO2, CH4, and N2. These membranes have a unique crystal structure with tiny, uniform pores that allow certain gas molecules to pass through while blocking others.
“Small-pore zeolites offer unique opportunities for selective gas separation because of their precise pore structures and high stability. My research aims to deepen the understanding of how these materials behave and how they can be optimised for real-world use,” says Iliana Kyriazidou, who recently defended her doctoral thesis in Chemical Engineering at Luleå University of Technology.
Membrane pores with atomic precision
The membranes with molecular-level pore size Iliana studied are only a few hundred nanometers thick, supported on porous ceramic support, and they can handle strong pressure differences and high temperatures. This makes them suitable for demanding industrial applications, such as upgrading biogas to higher purity by removing CO2 or removing carbon dioxide and other impurities from natural gas.
Through laboratory experiments she has shown how small differences in pore size and structure affect the selectivity and permeability of gases. Her work also contributes to a deeper understanding of how molecules move and interact within zeolite channels – knowledge that can be applied to other types of separations and to designing other types of functional zeolite materials in the future.
“By studying the behaviour of different gases inside the zeolite structure, we can tailor membranes that perform better and last longer in real systems,” says Iliana Kyriazidou.
Cleaner energy through better separation
The findings are relevant for both energy production and environmental technology. Efficient gas separation is a key step in producing biogas with low emissions and high energy content. Zeolite membranes can also help reduce the need for other separation methods, which are often energy-intensive.
“I hope that this research can contribute to more efficient and sustainable ways of cleaning and upgrading gas streams. These membranes have the potential to make industrial processes cleaner and more energy-efficient,” says Iliana Kyriazidou.
Facts
Zeolite membranes
Zeolites are porous crystalline materials made of silicon, aluminum, and oxygen. They act as molecular sieves – some gas molecules can pass through the tiny pores while others are blocked. Zeolite membranes are used to separate gas mixtures efficiently and with low energy use.
CHA and DDR
CHA (chabazite) and DDR (Deca-Dodecasil 3 Rhombohedral) are two types of zeolite structures with very small and uniform pores, particularly suitable for separating small gas molecules.
Chemical symbols
- CO₂ = carbon dioxide
- CH₄ = methane
- H₂ = hydrogen
- N₂ = nitrogen
Permeability
Permeability describes how easily gas molecules can pass through a membrane – in other words, its ability to let certain gases through while blocking others.
Contact
Iliana Kyriazidou
- Doctoral Student
- 0920-491324
- iliana.kyriazidou@ltu.se
- Iliana Kyriazidou
Published:
Updated: