Conversion of substances

DFG approves second funding period of the CRC 1316

Plasmas for the Systems for material conversion are an important component in the utilization and storage of decentrally generated renewable energies. The Collaborative Research Center 1316 (CRC 1316) "Transient Atmospheric Pressure Plasmas - from Plasma to Liquids to Solids" is dedicated to combining atmospheric pressure plasmas with catalysis to develop the most flexible solutions possible for this material conversion. "They should be scalable, controllable and robust against external influences, such as impurities in the starting materials," explains Prof. Dr. Achim von Keudell, spokesman of the CRC. 

The first funding period of the CRC 1316 was dedicated to the elucidation of transient phenomena in atmospheric pressure plasmas as well as interfacial processes at the surface of catalysts. Here, the focus was on three systems: the plasma-catalytic conversion of gases, the combination of plasmas with electrolysis at the interface between liquid and solid, and plasma-assisted biocatalysis, in which enzymes very selectively produce new molecules. The researchers were able to make great progress in these areas: For example, they achieved precise control of the formation of reactive particles in these plasmas. They were also able to gain a deeper understanding of the atomic and molecular surface processes in these systems. 

In the second funding period, these findings will be brought together to make the best possible use of the interplay between a plasma with its reactive particles and a catalytically active surface. There are many further questions in this regard, since in traditional catalysis, for example, stable molecules are essentially reaction partners, whereas in plasma catalysis, reactive particles or highly excited species can accelerate or suppress a specific reaction path. On this basis, the first prototype plants for plasma catalysis, plasma electrolysis and plasma biocatalysis are to be developed. 

In addition to the RUB as the host university, researchers from the University of Ulm, the Jülich Research Center and the Fritz Haber Institute in Berlin are involved in the CRC.

Conference

Japan Workshop

A workshop between CRC1316 and Japanese universities/research institutions will take part between November 29th and December 3rd, 2021. The organizers are Prof. Czarnetzki, Satoshi Hamaguchi, Jan Kuhfeld and two PhD students from Nagoya University. Further information can be found here.

Please note that the deadline is already October 27. Active participation is by invitation only, but passive participation is completely open. Participants must register in any case.

Insights into the SFB 1316

Virtual public 360° tour of the SFB 1316

Insights into the projects and laboratories, the opportunity to take a look at the various experiments and diagnostics and ask live questions about them - this opportunity is available to everyone on 27.10.2021 at 4 pm during a virtual 360° tour. The tour is aimed at the general public and thus offers not only researchers and students but also interested persons outside of university the opportunity to experience research interactively and get to know the projects better.

PUBLIC RELATIONS

Plasmas for all

A great many everyday technologies would not exist without plasmas. The teams of the Collaborative Research Centres want to share knowledge about their relevance with the public.

adapted from Julia Weiler, RUB

DIAGNOSTICS

Plasmas as chemistry labs

The smaller a plasma, the larger the experimental setup needed to study it. It is worth the effort, because the reaction conditions found in cubic-millimetre-sized plasmas are very much unique. Even though plasmas at atmospheric pressure are often only a few cubic millimetres in size, they pack quite a punch. This is because special non-equilibrium states can be set up in them, which facilitate physical and chemical processes that are not possible in any other environment. The plasma thus becomes a special kind of laboratory, where atoms and molecules can be excited without their surroundings heating up. “Such excitations could theoretically also be generated in a gas, but to do so we would have to heat it to several thousand degrees Kelvin. As a result, the molecules would decompose,” explains Professor Uwe Czarnetzki, Head of the Chair of Plasma and Atomic Physics at the Faculty of Physics and Astronomy. For many years, he and his team have been developing methods to explore the processes inside plasmas and to characterise the plasmas. Plasmas boast a unique feature: electric fields can be used to supply energy to the electrons in the plasma; the electrons in turn interact with molecules such as nitrogen or carbon dioxide while transferring the energy to them. The molecules are excited, and this happens without the environment heating up in the process, as would be the case in a gas. The molecules that are excited to vibrate have a much higher reactivity than those in the ground state. Plasma can therefore change chemistry or even enable certain chemical processes in the first place. Consequently, plasma provides basic researchers with a unique opportunity to study the excitation of molecules and the associated chemistry beyond thermodynamic equilibrium. Uwe Czarnetzki is therefore primarily interested in the vibrational states of molecules in plasmas.

MGK Colloquium

Virtual MGK Colloquium

The scientific exchange among the CRC members and the group of Early Career Researcher occurred continuously during the three yearly project meetings and in the workshops organized by the CRC 1316 since it starting in 01/2018. However, it is very important that the ECR have also a platform to interact in a conference setting without the impact of their adviser to stimulate the discussions among the ECR. Instead, the CRC 1316 decided to organize an MGK Colloquium on its own by inviting the ECR from the CRC 1316 and from the SFB-TR 87. This meeting was organized by the ECRs J. Kuhfeld and P. Preissing in a virtual format on 21/04/2021. Prominent invited speakers at this event were Prof. A. Bogaerts (university Antwerp), Dr. S. Iseni (GREMI, Orléans) and Dr. T.L. Chng (LPP Paris). Beside presentations within a zoom meeting, virtual poster sessions were performed, enhancing the interaction between the ECR.

Honour of research of project A5

Project A5 on the Inside Front Cover of Plasma Processes and Polymers

The current issue (April 2021) of Plasma Processes and Polymers features work from project A5 of the CRC 1316 on the topic of "positive and negative streamer propagation in volume dielectric barrier discharges with planar and porous electrodes" on its inside front cover.

The scientists have found that the discharge characteristics of negative surface streamers differ significantly from those of positive surface streamers. While negative streamers develop along the dielectric surface, allowing them to propagate into much smaller dielectric pores, positive streamers floatingly develop above the dielectric.

Project A7 - Catalysis

Catalytic carbon monoxide oxidation over potassium-doped manganese dioxide nanoparticles synthesized by spray drying

One of the major objectives of the CRC 1316 is the investigation and understanding of the complex interactions between a non-thermal plasma and heterogeneous catalysts. The first results of project A7 describing the thermocatalytic oxidation of CO over MnO2 catalysts were recently published in Emission Control Science and Technology. Particularly, the effect of the incorporated alkali ions on K+ and Na+ on the structural properties and the catalytic performance was emphasized to derive structure-activity correlations.

The MnO2 catalysts were synthesized by a semi-continuous spray drying procedure based on the comproportionation reaction of Mn(NO3)2 and KMnO4. Solutions of both compounds were continuously mixed in a micromixer and the emerging suspension was rapidly quenched by spray drying to inhibit further particle growth. In order to exchange the K+ ions by Na+ ions, NaMnO4 was used instead of KMnO4 during the synthesis. After washing and drying of the catalysts a fine brown powder was obtained, which was used as prepared or calcined at 450°C or 500°C for 4 h in synthetic air.

As shown by the XPS results and TPO profiles Mn (IV) is the predominant oxidation state of all samples prior to calcination proving that all catalysts consist of MnO2. However, the XRD patterns of the uncalcined catalysts reveal an X-ray amorphous structure preventing a more in-depth phase identification. After calcination the phase structure strongly depends on the type and amount of the incorporated alkali ion. The presence of K+ promotes the formation of crystalline alpha-MnO2 and stabilizes its tunnel structure up to temperatures of 500°C. Lower amounts of K+ or the exchange with Na+ lead to less crystalline phases after calcination at 450°C and to the formation of crystalline alpha-Mn2O3 after calcination at 500°C.

The catalytic CO oxidation was performed in a microreactor set up equipped with a non-dispersive IR detector. All uncalcined catalysts revealed a similar catalytic performance regardless of the type or amount of the incorporated alkali ion. Even though the specific surface area of the catalyst decreased from 77 m2/g to 37 m2/g during calcination the pure alpha-MnO2 phase exhibited a superior catalytic activity. Over alpha-MnO2 the temperature at which full conversion was achieved was shifted towards lower temperatures by more than 100°C. In contrast the catalyst containing alpha-Mn2O3 show a catalytic activity similar to the uncalcined catalysts indicating that not only the higher degree of crystallinity but also the structural properties of alpha-MnO2 cause its high catalytic activity. The incorporation of K+ ions is required to stabilize the tunnel structure of alpha-MnO2