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Nickel catalyzed cross coupling

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Researchers have now discovered a special property of nickel as a catalyst. This metal catalyzes the linkage of aromatic hydrocarbons as a nickelate, a negative ion. In this ion, the two metals lithium and nickel are in an unusual relationship, according to the publication in the journal Angewandte Chemie.

When building carbon skeletons, chemists:inside like to rely on catalysts made of the noble metal palladium. Its parade reaction is cross-coupling, in which two hydrocarbon fragments are joined together to form a larger unit. However, some substrates resist the reaction. Then detours must be taken or the substrates must first be activated for such coupling reactions by certain tricks.

In some cases, nickel could provide a remedy as an alternative catalyst, write Eva Hevia and Andryj M. Borys of the University of Bern. They showed that under certain conditions, nickel forms a negatively charged intermediate that also causes otherwise rather sluggish substrates to react.

For example, a nickel catalyst catalyzes the cross-coupling of aryl ethers, which are found in tar and other petroleum products and are basic materials for many specialty chemicals. Such substances are not very reactive, so they often have to be laboriously activated for reactions. Hevia and Borys now studied the reaction of phenyllithium (activated benzene) with beta-naphthymethyl ether, a simple aryl ether. They used a nickel catalyst consisting of one nickel atom and two molecules of cyclooctadiene, abbreviated as Ni(COD)2.

The researchers discovered that the negatively charged ion, or nickelate, formed in the very first reaction step. Two molecules of phenyllithium transferred their negatively charged phenyl radical to the neutral nickel atom. This was only possible, the team said, because the lithium ions and coordinated solvent molecules stabilized the buildup of the nickelate.

As the reaction progressed, the nickelate catalyst initiated the cleavage of the difficult ether bond between carbon and oxygen, after which the product, phyenylnaphthalene, could form. The authors identified the stabilizing solvent and the cooperation between lithium and nickel as instrumental in the success of the reaction.

The anionic reaction pathway offers an interesting alternative to the commonly used palladium-catalyzed cross-couplings. However, as Borys’ and Hevia’s work shows, this reaction pathway depends on how well the catalyst forms and how stable it is.

“The insights into the reaction mechanism made in this study will allow further development of nickel catalysis for sustainable syntheses.”

– Eva Hevia

Chemicals

Evonik and LIKAT discover new type of hydroformylation

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A research team involving Evonik and the Leibniz Institute for Catalysis (LIKAT) has made another breakthrough in the field of hydroformylation. Hydroformylation is one of the most important reactions in industrial organic chemistry. Unsaturated compounds are converted into aldehydes and alcohols using synthesis gas.

 

Until recently, the scientific consensus was that this reaction, if catalyzed with cobalt, could only be carried out under high pressure conditions without the catalyst decomposing. This was disproved by Professor Dr. Robert Franke, head of hydroformylation research at Evonik, together with research partners from LIKAT, Dr. Baoxin Zhang and Dr. Christoph Kubis.

 

 “With this discovery, we have identified new process options for hydroformylation,” says Franke, who is also a professor of chemistry at Ruhr University in Bochum. “In the future, it may be possible to make this large-scale reaction much more economical and environmentally friendly. Developing these processes will be our task for the next few years.”

 

The researchers succeeded in demonstrating, for the first time, that cobalt carbonyls – very inexpensive compounds for the catalysis of hydroformylation – are active and stable even at low pressures. The key to this discovery was the development of special spectroscopic measurement methods and associated mathematical tools for data evaluation.

 

High-pressure processes that use cobalt carbonyls as catalysts could be replaced in the future by new processes with lower pressures. These new processes would then be more cost-effective, energy-efficient and thus more sustainable. At Evonik, this would have an impact on the production of long-chain alcohols such as the oxo alcohol isononanol (INA), which is used, among other things, to manufacture plasticizers.

 

Due to the particular importance of this discovery, the renowned journal Science published the results of the project. This is Professor Dr. Robert Franke’s second appearance in Science on carbonylation reactions. In 2020, Franke succeeded in a so-called ‘dream reaction’: the direct carbonylation of 1,3-butadiene. This discovery was also worthy of publication in the journal.

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Further measures for the digitization of processes

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Chemical company Röhm has digitized its processes with the help of Shiftconnector, software from global software provider eschbach, achieving sustainable improvements in safety, quality and productivity.

Röhm is a leading global supplier of methacrylate products – including the Plexiglas brand. With 15 production sites on four continents, the company supplies important future markets such as automotive, the electronics industry and medical technology – and has recently started relying on Shiftconnector, the software solution from eschbach.

Digitally supported shift transfer for more safety and productivity

Shiftconnector is a Plant Process Management (PPM) software solution developed specifically for the chemical industry. It networks the workforce of production plants working in a 24/7 shift system with each other and ensures smooth communication, as well as transparency and traceability, especially during critical shift handovers.

“After the spin-off from the Evonik Group in 2019, we pushed ahead with digitization in our company.”

– Dr. Hans-Peter Hauck, COO

For the digitization projects in the production area, the plants were surveyed to determine the actual needs. In addition, a market analysis was carried out with the help of a consultant and Shiftconnector from eschbach was introduced at Röhm worldwide.

The PPM software from eschbach offers companies a central platform on which all production-relevant and process-related information converges. With interfaces to both the plants and the employees in production, Shiftconnector succeeds in bringing together process data and information statuses of employees as well as their know-how centrally, so that all levels – from management to plant and shift management to plant operators – have relevant information at their disposal at all times.

Decentralized implementation successfully carried out globally

The implementation of Shiftconnector was not controlled centrally from headquarters, but placed in the hands of local project management, which proved to be a particularly efficient approach. In addition, the entire rollout could be carried out online, which contributed significantly to the fast and sustainable success. Where individual employees in production used to travel around with pen, paper and camera, a tablet is now sufficient to transfer entries from shift rounds to the PPM system with just a few clicks, for example.

The feedback from the end users is consistently positive: “Shiftconnector is also very helpful when analyzing anomalies and problems in ongoing production,” says plant manager Dr. Sibylle Strandt. “The orderly merging of process data from the plant with the information provided by the employees makes root cause research and problem solving much easier.” And Hauck adds, “Platform has made a significant contribution to improving the quality, safety and productivity of our processes.”

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Fusion processes can be triggered by pulsed electric fields

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Pulsed electric fields caused by lightning strikes make themselves felt as voltage spikes and represent a destructive hazard for electronic components. They cause considerable damage. A team from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has now discovered that such voltage spikes can have quite useful properties. In the journal Physical Review Research (DOI: 10.1103/PhysRevResearch.3.033153), the scientists report how, for example, nuclear fusion processes can be significantly enhanced by extremely strong and fast pulsed electric fields. Nuclear fusions, such as those that take place in the sun, are made possible by the quantum mechanical tunnel effect.

“One consequence of the tunnel effect is that similarly charged particles can overcome their mutual repulsion, even if their energy is not actually sufficient to do so – at least not according to the laws of classical mechanics. We can observe something like this, for example, in the fusion of two light atomic nuclei: The closer one nucleus approaches the other, the greater the repulsion, which we can imagine figuratively as a mountain piling up in front of the nucleus, the so-called potential barrier. Instead of taking the more energy-consuming path over the top, the laws of quantum mechanics allow the nucleus to penetrate or ‘tunnel’ straight through this mountain in a much more energetically favorable way – and finally to fuse.”

– Prof. Ralf Schützhold, Head of the Department of Theoretical Physics

Although the tunneling effect plays an important role in many areas of physics and was first described nearly one hundred years ago, our understanding of the process is still incomplete today. “Various facets of the influence of electric fields on tunneling processes were already known. For example, electric fields can additionally accelerate particles, helping them to gain more energy. They can also deform the potential barrier and increase the tunneling probability in this way,” says Dr. Christian Kohlfürst, outlining the situation at the beginning of their research.

His colleague Dr. Friedemann Queisser briefly sums up their results: “Our calculations now show for the first time a special feature of pulsed electric fields that change rapidly in time: they can ensure that the particles are pushed out of the potential barrier, figuratively speaking, and thus tunnel more easily.” The calculations of the HZDR team show this quite concretely in various examples, including a fusion reaction of interest for possible energy generation: the fusion of a proton with the isotope boron-11.

Fusion reaction with advantages

It is interesting primarily because of the relatively readily available fuel. Three alpha particles, each with a double positive charge, are produced in the process. What is remarkable about this reaction is that the energy is released in the form of charged particles and not as neutron radiation as in the most well-known fusion reactions at present. This has advantages: For one thing, the problems associated with neutron flux would be significantly reduced, such as the dangers of dealing with ionizing radiation. For another, the energy of charged particles can be converted directly, and thus much more easily, into electricity.

However, the conditions required to use the reaction are even more extreme than those of the deuterium-tritium fusion favored in the current ITER fusion reactor experiment. Igniting the proton-boron reaction is more difficult by comparison, and scientists are still searching for viable ways to do so. Schützhold’s team now points to one possibility: “According to our calculations, a sufficiently fast and strong pulsed electric field can significantly enhance not only deuterium-tritium fusion but also the proton-boron reaction.”

However, generating such fields is very difficult. “In principle, we can think of it as being like a thunderstorm, where the energy stored in huge cloud formations is discharged in the form of a lightning strike in a very short time and in a very confined space. Facilities are being built or planned around the world that are intended to concentrate ever higher energies into ever shorter periods of time and ever smaller spatial areas,” says Schützhold. Unfortunately, the facilities available today are not yet quite capable of generating such fast and powerful “artificial lightning.”

But there is a possible way out: The electric field of an alpha particle flying fast and, above all, close to the proton can act like such a pulsed electric field and strike so strongly that the proton can tunnel through the potential barrier of boron-11 and trigger the fusion reaction. Alpha particles with the necessary pulse energy are actually generated in the proton-boron reaction, but they can also be injected from outside.

 

 

 

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