Chemie Ingenieur Technik最新文献

Reversible addition-fragmentation chain-transfer polymerization, or RAFT, is a method for the controlled synthesis of block copolymers and an alternative to living ionic polymerizations. Although it is less susceptible to impurities, oxygen leads to inhibition of the polymerization. In a previous study, a model was developed to describe the inhibition kinetics of the RAFT polymerization of styrene. Based on this model, a detailed sensitivity analysis is performed with respect to the kinetic coefficients. While the formation of polyperoxides by oxygen addition shows high reaction rates, their further reactions (growth and termination) could be identified as rate-determining steps. In addition, a proportional dependence of the duration of inhibition on the oxygen concentration was found. Based on the knowledge gained, a new initiation strategy with different thermal initiators to optimize polymerization was successfully tested using simulations.

Fiber composite materials are key components of numerous future technologies. This results in a strongly increased demand and also in increasing amounts of waste in the upcoming years. Thus, recycling of fiber composite materials has become an intensively researched topic. At 95 wt %, glass fiber-reinforced plastics make up the largest part. This review article will provide an overview of the state of the art of common recycling strategies and technologies, with particular focus on the advantages and challenges of glass fiber-reinforced polymer recycling.

Syntheses of alternative platform chemicals, such as 5-chloromethylfurfural (CMF), from bio-based starting materials are often associated with complicated kinetic schemes and mass transfer processes. Millistructured flow reactor concepts can help to elucidate kinetic schemes and determine rate constants which are of crucial importance for the design of respective technical processes. For the first time, the influence of proton concentration on the rate constants involved in the biphasic synthesis of CMF is systematically investigated. Results are discussed in terms of green chemistry metrics.

The effect of rare earth oxides as dopants on the Pt-governed oxidative coupling of methane (Pt-OCM) is investigated. The addition of 20 wt.-% of La-, Nd-, Sm-, and Pr-oxides to the support benefits the C₂ product selectivity and offers the potential to enhance the catalyst stability. Compared to the reference catalyst Pt/Al₂O₃, the addition of Sm₂O₃ increased the total selectivity by up to 23 %. Furthermore, La₂O₃ addition was found beneficial with respect to the (thermal) stability of the catalyst. Dopant content variations uncovered that the catalyst formulation with 20 wt.-% La₂O₃ represents an optimum regarding performance and stability.

High-throughput experimentation, a well-established and powerful tool in the field of heterogeneous catalysis screening, has been extended to the field of electrochemistry. A parallel and modular high-throughput screening platform was designed, involving the development of a new modular electrochemical flow cell by the Fraunhofer Institute for Microengineering and Microsystems (IMM) in cooperation with hte GmbH and IEK-9 / FZ Jülich GmbH. Here, this platform is introduced for alkaline water electrolysis, showing initial results that underline the flexibility, comparability, and accuracy of the experiments.

Fluid guiding elements (FGEs), additive manufactured inserts that enhance heat transfer, have shown the potential to reduce the size of pipe-in-pipe heat exchangers up to a factor of 20. Due to their unique design, the calculation of the geometrical parameters for a specific application remains challenging and was initially solved by computationally expensive computational fluid dynamics simulations. This work presents a simplified approach, which treats the fluid and the FGE as pseudo-homogeneous to enable the fast calculation of effective heat transfer coefficients. The approach is developed based on water in laminar flow state and subsequently tested with different fluids.

CFD-based compartment (CPT) models offer a promising modeling method and trade-off between computational effort and required accuracy. The models combine the relevant fluid dynamics from the computational expensive CFD and the incorporation of complex reaction mechanisms usually used in basic reactor models. However, one criticism is their reliance on specific operating points, rendering them invalid when boundary conditions change. This study explores using a CFD-based CPT model for static mixing elements across multiple operating points by making use of the creeping flow. The mean age theory facilitates a comprehensive comparison between CFD and CPT models. Results indicate that within this flow region, the CPT model can be extrapolated to other operating points via linear scaling.

It is becoming increasingly important to be able to recycle mass-produced products such as engine air filters. Different processes were tested to investigate whether it is possible to recycle the composite material. Thereby, comminution with cutting stress is particularly suitable for disintegration. Next on, the filter medium could be separated very well with the help of a zig-zag separator. The sorting of polyurethan foam and polypropylene hard plastic could be achieved with a dense media separation. It became clear that the pretreatment, which is intended to liberate the material, has a significant influence on the sorting result and the purity of the products.

Dear readers,

“Chemistry does not deserve its bad reputation!” – as the Swiss protein researcher and Nobel Prize winner Kurt Wüthrich put it in 2019, and indeed: the general public still has many negative associations with the topic of chemistry. Yet there is no doubt that chemistry is indispensable for a large number of industrial value chains and is one of the most important drivers of new product developments and innovations in a wide range of economic sectors. And yet: despite all past successes in terms of significant reductions in emissions, energy and resource consumption, the demands for a green, sustainable and efficient chemical industry are experiencing a new dynamic, despite the fact that the chemical industry has long been facing up to the challenging objectives of defossilising its production processes, establishing a circular materials and energy economy and achieving greenhouse gas neutrality.

It is also becoming increasingly clear that the promotion of green, efficient and sustainable chemistry is also worthwhile for economic and competitive reasons. The demand from the processing industry for green processes and primary products (»sustainable supply chain«) is constantly increasing and competitive advantages can be realised more and more easily by increasing efficiency or tapping into sustainable sources of raw materials and energy.

Providing targeted support for this new “green chemistry” dynamic with new research and development contributions is the central mission that nine Fraunhofer Institutes have been pursuing for three years now in a joint, interdisciplinary lighthouse project. Under the title “Shaping the Future of Green Chemistry by Process Intensification and Digitalisation (ShaPID)”, the Fraunhofer Gesellschaft is conducting independent applied preliminary research to show ways in which sustainable, green chemistry can succeed through practical technological innovations. The range of example processes is extremely broad. How do we get from CO₂ and biogenic raw material sources to new polymers? How can we successfully synthesise important monomer building blocks from non-fossil raw materials in an energy-efficient way? Or how can highly reactive species be utilised for the atom-efficient production of precursors? In the ShaPID lighthouse project, complementary technologies from various areas of synthesis, reaction and catalysis technology, electrochemistry, continuous process and process engineering, modelling, simulation and process optimisation as well as digitalisation and automation are being brought together in a suitable way. We are convinced that this interdisciplinarity is the key to achieving the necessary technological maturity of new green chemical processes. This also requires suitable “green metrics” concepts and tools in order to be able to describe the “greenness” of chemical processes as objectively, qualitatively and quantitatively as possibl