Unlocking Catalytic Reactions: The Role of NMR Spectroscopy in the Green Transition

Topsoe is a company focused on the green transition, where developing new renewable alternatives for fuel is an important goal. One important product at Topsoe are catalysts, which are used to drive the reactions when producing fuel, and here NMR is used to investigate the contents and understand the role of catalysts in chemical reactions. Michal Lutecki is a principal scientist at Topsoe. He is responsible for most of the NMR-related work at the company. Here, he uses special NMR methods such as low-field relaxometry to investigate catalysts and their properties.

In the rapidly evolving landscape of chemical research and industrial catalysis, there is a pressing need to unlock the secrets of molecular interactions, which are fundamental to the design of catalyst. This is of great importance as the demand for cleaner fuels to reduce CO2 emissions has increased in the world today. In the midst of this green transition stands Michal Lutecki, a scientist who has embarked on a journey to understand and enhance catalytic reactions. Michal was born in Poland and did his master’s in the southeast part of the city of Rzeszow. After his master’s, he spent a year in the Czech Republic as a research intern at the Czech Academy of Science before moving to Germany for his PhD.

During his PhD, he investigated heterogeneous catalysis and technical chemistry, a field he still contributes to and uses extensively in his position at Haldor Topsøe today. Although now proficient in NMR, it wasn’t until after his PhD that Michal started using NMR. In 2010, he moved to a group in the UK at the University of Cambridge at Department of Chemical Engineering and Biotechnologyled by Prof. Lynn Gladden, a group of experts heavily invested in NMR and MRI.

At Cambridge, he used NMR and MRI in novel ways, by imaging catalytical reactions inside a reactor while inserted into the MRI magnet. The reaction was then followed by sophisticated T1 and T2 diffusion NMR and imaging, and other more traditional spectroscopic studies of what exactly is going on with the reactants and products.

All the research conducted at Cambridge was carried out in operando mode, meaning it was conducted at actual temperatures and pressures, specifically at 50 Bar and 250 – 300 ºC. This approach is noteworthy in the field of NMR because temperature variations can significantly affect NMR results. The reactors used in standard heterogeneous catalytic processes are predominantly constructed from regular steel, but the reactor employed by Michal in Cambridge was made of silicon carbide, a ceramic material known for its

NMR transparency. This unique feature allowed them to run samples at these conditions effectively making them able to run samples closer to real world scenarios.

Work at Topsoe

In 2014, Michal moved to Denmark to work at Topsoe, a chemical technology company. He was employed as a principal scientist and a project manager in the R&D department. His main assignment was the development of catalysts for both renewable and fossil fuels, which are still very important despite the ongoing transition to renewables.

Catalysts are especially important for Topsoe as they facilitate and speed up the many chemical reactions needed for the processes that the company is developing without undergoing permanent changes themselves. NMR has never been the focus of Topsoe, but when Michal moved there, there was still some in house NMR magnets. Today, they have been removed so instead they rely on collaborations.

Currently, NMR spectroscopy at Topsoe has a narrower scope, with a particular emphasis on hydrogen NMR measurements. This focus originates from their analytical work involving various fuel types, both renewable and fossil. Here NMR proves invaluable in determining crucial factors like hydrogen content in liquid fuels, providing essential data for their projects aimed at sustainability and energy generation from diverse fuel sources.

In the past, Topsoe also engaged in more fundamental studies that delved into relaxometry. This entailed using benchtop magnets to measure critical parameters such as T1 and T2 relaxation times. These investigations aimed to understand how relaxometry properties change when a liquid medium is introduced into porous materials. This research was particularly significant given that Topsoe’s core focus often revolves around catalysts, which are typically composed of porous materials. The insights gained from relaxometry were invaluable for comprehending how these porous materials interacted with liquids, a vital aspect in catalyst development and performance evaluation.

Long-field NMR relaxometry

Michal frequently employs a specialized NMR technique known as ‘low-field NMR relaxometry.’ This approach involves studying relaxometry parameters such as T1 and T2 using low-field NMR magnets. Additionally, it includes an investigation of the diffusion coefficient, which provides valuable insights into how substances move within porous media.

T1 and T2 relaxometry is a concept developed back in the 80s, with the background from the oil extraction industry, where T1 and T2 relaxation parameters of oil are measured to get information about what happens in the reservoir of the oil, to find out what the oil consists of and if it’s pure or mixed with water. This is possible since the T1 and T2 parameters are very different depending on whether they are measured in oil or water.

“You can consider T1 and T2 as distinctive characteristics that reveal what’s inside the sediments found in oil reservoirs. Over time, relaxometry found application in catalytic studies, where researchers believed it could provide unique insights into how liquid reactants and products behave within porous catalysts, as well as how these substances interact with the surface of the porous material.”

T1 and T2 relaxometry parameters are therefore an indication of the interaction of liquids on the interface of liquid solids. When you measure the relaxometry parameters with NMR in a liquid, it will have certain T1s and T2s, which can vary from milliseconds to tens of seconds depending on what kind of liquid it is.

When it is in the restricted volume of a porous media, the T2s get much shorter because of the interaction at the surface, so the ratio between the T1 and T2 can reveal how strong the interaction between liquid and a catalyst, or the porous media is. From this, they can then get some information between products and reactants that are in the environment.

Products

Topsoe stands at the forefront of the catalyst production industry, and their contributions have been instrumental in transforming the refining of crude oil into cleaner gasoline and diesel products. This transformation, dating back to the 1970s and 1980s, was catalyzed by the establishment of stringent standards for impurity content, particularly sulfur and nitrogen levels. These standards have steadily evolved over the years, setting increasingly demanding limits.

Especially sulfur reduction has been an important achievement. Sulfur, which is a significant contributor to acid rain, has seen a substantial reduction in fuel products. Today’s gasoline and diesel are hundreds, if not thousands, of times cleaner in terms of sulfur content compared to previous decades.

NMR has emerged as a key player in driving this progress. By providing precise insights into the composition of fuels, NMR technology has aided in meeting and exceeding these strict standards, ensuring that the fuels we use are cleaner, more environmentally friendly, and compliant with ever-tightening regulations. So, while Topsoe focus more on renewable fuels today, they also produced those catalysts that were used for fossil fuels back then, which was also an important factor in improving the environment.

Something most people don’t think about is that refineries are huge structures with kilometers of equipment. Some of the reactors inside can hold as much as 500-700 cubic meters of catalyst that is loaded and used for purifying crude oil. What Haldor Topsøe develops is exactly those enormous amounts of catalysts.

Another large area for the company has been the ammonia industry and the production of fertilizers via ammonia synthesis, which is what Topsoe started with back in the day. Currently, they are on the forefront of developing different green electrification methods to produce hydrogen that can be used as a reactant for various products. They call the project “Power to X” because they produce power from green energy that can be transferred to anything, and they’re one of the very first to do it on large industrial scales.

Collaborations

In the NMR field, Topsoe has collaborated with many groups both in Denmark and internationally. This is spurred from the lack of in-house high field NMR at Topsoe a decision made as, especially maintaining the high-field NMR magnets is costly.

Therefore, Michal and Topsoe in general often relies on collaborations, in particular the University of Manchester has been an import one, who support them by studying liquid diffusion in porous materials. The samples are prepared by Topsoe, sent to Manchester for NMR analysis, and then subjected to additional examination, including absorption and Electron Microscopy. This partnership enhances our understanding of liquid behavior within porous materials.

Another of Topsoe’s longest collaborations has been with the University of Aarhus (AU) with Prof. Skibsted, where they have been investigating zeolites, which Topsoe uses in many of their products.

Together they wanted to understand how zeolites are synthesized and investigate problems with zeolites purity and silica-to-alumina ratio, for which Si NMR and Al NMR are very useful. Zeolites are crystalline silica-alumina materials that are made of silicon and aluminum atoms arranged in a very specific way. They are famous for their acidity since they are very strong solid acids.

Originally, zeolites were only for academic interest, but they became very popular back in the 70s and 80s for heterogeneous catalysis because of their use as catalyst for many acid-catalyzed reactions. For many years now, zeolites have been applied in the industry around the world.

One of the processes for which they use zeolites is in the production and purification of fuels like gasoline or jet fuel, but also in production of renewables, as, for example, from biomass. It is a very complex process to purify fuels, as it is not only about removing contaminants such as sulfur and nitrogen, but also to react the purified oil in a specific way, so it meets the specification of the exact product, whether it is diesel, jet fuel, or gasoline and for this, zeolites are crucial.

Strength of Danish NMR

“It’s a great strength that we have formed DANNMR that is linking all the universities and the industry stakeholders in NMR together. Although the more traditional companies like Topsoe are not the biggest contributors to DANNMR. Denmark is traditionally very focused on industrial bio applications and here NMR is a crucial tool for development of new drugs.”

“DANNMR is a perfect environment for industry to reach out to the universities, to form new collaborations and vice versa. If I need high-field spectroscopy, I will go to INano at AU. If I am interested in phosphorous applications, I will contact the Southern Danish University (SDU)” explains Michal.

“Everything in DANNMR is nicely organized and easy to access. Finally, Denmark is recognized as top level both in solid-state NMR and biochemical and biomedical NMR, so DANNMR is one of the world’s best at what it does compared to its size. Maybe Denmark’s strength doesn’t always align with Topsoe’s focus, but we know our strengths in Denmark, and we know what we are good at, which is important.”