Chemical engineer helps to ’greenify’ the chemical industry

Serena Agnolin. Photo: Angeline Swinkels
Serena Agnolin. Photo: Angeline Swinkels
TU/e-researcher Serena Agnolin researched effective ways to make often-used chemical reactors more efficient as a PhD, driven by her passion for making her own industry more sustainable.

Alternatives for the current energy-intensive separation processes in the chemical industry could significantly decrease both the sector’s CO2 footprint and its energy consumption. In the PhD project she conducted in the Sustainable Process Engineering group, Serena Agnolin developed novel membranes for the production of hydrogen in a more sustainable way. She defended her thesis cum laude on 7 May at the Department of Chemical Engineering and Chemistry.

The chemical industry is one of the main contributors to CO2 emissions from industrial processes. Most chemical reactions yield not one product, but rather a mixture of different compounds, from which the intended molecule must be separated.

The most commonly used separation technique is distillation, which is based on the different boiling points of the various components of the mixture, requiring heat and thus energy. Distillation is one of the most energy-intensive parts of the chemical plant, contributing significantly to CO2 emissions.

Separating valuable products in a different way can thus lower CO2 emissions and reduce energy consumption at the same time.

In her PhD research, Italian-born Serena Agnolin focused on so-called membrane reactors to produce hydrogen, which can either be used as a chemical compound or as a fuel. In these types of reactors, membranes are used to separate the hydrogen directly in the production vessel from the rest of the reaction products. This avoids the use of other large, energy-intensive separation components later on in the process.

Hydrogen production

"My research was part of a larger scale European project called MACBETH," Agnolin says. "This project was aimed at developing a catalytic membrane reactor for four different chemical processes. I was working on the membranes for hydrogen production from natural gas."

Agnolin focused on membranes made from palladium, since this material has a high selectivity for hydrogen. Traditionally, palladium membranes are supported by a substrate made from ceramics. "However, ceramics are fragile, and tend to fail or break. Our idea was to recreate these membranes on a metal tube instead, to make them stronger."

Filling the pores

Though this might sound rather straightforward, realizing this idea in practice turned out to be challenging, Agnolin says. "It was impossible to deposit a vast, defect free layer of palladium on top of the metal, no matter how much I polished it. Plus, the metal travelled into the palladium at high temperature. I even developed a dedicated interlayer, but still I wasn’t able to close the holes in the metal tube."

The breakthrough came when one day, the PhD researcher decided to fill the holes of the metal tube with ceramics. "That finally rendered the sought after stable membranes with high hydrogen selectivity."

Agnolin tested her membranes in a fixed bed reactor that combines methane with water vapor to produce hydrogen, carbon dioxide, and carbon monoxide. "With our membranes, we managed to efficiently separate the hydrogen from the other reaction products. And by removing the hydrogen during the reaction, more of the methane was converted into hydrogen."

Passing the ultimate test

Besides on the methane steam reforming reaction, Agnolin also tried out her membranes on a different reaction, namely the production of hydrogen by cracking ammonia. "Since this reaction can be used to produce hydrogen for fuel cells, the hydrogen produced must be very pure, and thus the selectivity of the membranes has to be even higher for this application."

To her great satisfaction, Agnolin’s membranes also passed this even harder test. With her thesis defense, Agnolin’s involvement in the development of the palladium membranes ended.

Currently, she is working as a postdoc in the same group on another type of membranes: carbon molecular sieve membranes that are used in gas separation. "The week after my defense, I just came back to the office. There still is enough work to be done," she smiles.

Productie van palladiummembranen

Together with her colleagues, Serena Agnolin made an instruction video for producing metallic supported palladium membranes.

Craving for creative processes

Though she is not sure yet whether she’ll stay in academia or transition toward industry at some point in her career, the Italian chemical engineer knows very well what she is looking for in a job.

"I like to develop new things from scratch, and I love writing papers. I am probably one of the few PhD researchers who actually enjoyed writing a thesis. Writing is a creative process, like art and drawing. And creating new things, whether that is in writing or in technology, is what I love most."

Serena Agnolin defended het thesis " Development of metallic supported Pd-based membranes for H2 separation: Design and application in membrane reactors " at the Department of Chemical Engineering and Chemistry on May 7th, 2024.

Supervisors: Fausto Galucci and John van der Schaaf