Oxidation processes in combustion engines and in the atmosphere take the same routes
Efficient autoxidation chain reactions demonstrated for the substance group of saturated hydrocarbons
(Press-News.org) Thuwal/Helsinki/Leipzig. Alkanes, an important component of fuels for combustion engines and an important class of urban trace gases, react via another reaction pathways than previously thought. These hydrocarbons, formerly called paraffins, thus produce large amounts of highly oxygenated compounds that can contribute to organic aerosol and thus to air pollution in cities. An international research team has now been able to prove this through laboratory experiments with state-of-the-art measurement technology at the University of Helsinki and the Leibniz Institute for Tropospheric Research (TROPOS) in Leipzig.
The results of this interdisciplinary work provide crucial information about oxidation processes both in combustion engines and in the atmosphere - with direct implications for engine efficiency and the formation of aerosols, especially in cities, the research team writes in the journal Communications Chemistry, an open-access journal published by the Springer-Nature publishing group.
Oxidation processes play a major role both in the atmosphere and in combustion. A chain reaction called autoxidation is enabled by high engine temperatures. But it also acts as an important source of highly oxygenated compounds in the atmosphere that form organic aerosol, as researchers from Finland, Germany and the USA demonstrated in 2014. Autoxidation is one reason for ageing processes of organic compounds by oxygen from the air. It contributes to the spoilage of food and wine.
This chain reaction is initiated by the formation of peroxy radicals (RO2). The propensity of organic compounds to undergo such multistep autoxidation determines the ignition timing of fuels in engines and, on the other hand, the potential for the formation of low-volatility condensable vapours and consequently organic aerosol in the atmosphere. The extent to which multistep autoxidation takes place depends on the molecular structure of the organic compounds and the reaction conditions. Determining the different reaction pathways of peroxy radicals, which are important intermediates in all oxidation reactions, is crucial for the formation of the different reaction products and their key properties, which can ultimately affect both human health and the climate.
Since peroxy radicals are very reactive, their chemical reactions take place very quickly and individual reaction steps were thus overlooked for a long time. The discovery of highly oxygenated organic molecules (HOMs) seven years ago was only possible due to advances in measurement techniques. A special mass spectrometer (Chemical Ionisation - Atmospheric Pressure Interface - Time of Flight (CI-APi-TOF) mass spectrometer), that can monitor the very short-lived compounds, was used now to measure the radicals and oxidation products of alkanes. "Until now, there have been no studies on HOM formation from alkanes because it was assumed that their structure would be unfavourable for autoxidation," reports Dr. Torsten Berndt from TROPOS. Methane, an important greenhouse gas, belongs to the group of alkanes. But the most important fossil fuels of the world economy from crude oil and natural gas also consist of alkanes: these include propane, butane, pentane, hexane, heptane and octane. New findings about the oxidation behaviour of this group of substances therefore have great relevance in many areas.
To gain a deeper insight into alkane autoxidation, experiments were carried out in the free-jet flow reactor at TROPOS in Leipzig in addition to experiments in Helsinki. The experimental set-up is optimised so that the gases do not come into contact with the walls during the reaction in order to exclude interferences of the results by wall processes. During the experiments, almost all reactive intermediates, RO2 radicals and their reaction products could be directly monitored. The interdisciplinary cooperation of researchers from combustion chemistry and atmospheric chemistry proved to be very useful, because in the combustion processes analogous processes take place as in the atmosphere, only at a higher temperature. "As a result, it became visible that not only isomerisation reactions of RO2 radicals but also of RO radicals are responsible for the build-up of higher oxidised products. The study made it possible to identify with the alkanes the last and perhaps most surprising group of organic compounds for which autoxidation is important", Torsten Berndt concludes.
Even at high concentrations of nitrogen oxides, which otherwise quickly terminate autoxidation reactions, the alkanes apparently produce considerable amounts of highly oxidised compounds in the air. The new findings allow for a deeper understanding of autoxidation processes and give rise to further investigations on isomerisation reactions of RO radicals.
[Attachments] See images for this press release:
ELSE PRESS RELEASES FROM THIS DATE:
LOS ALAMOS, N.M., February 23, 2021--A revolutionary machine-learning (ML) approach to simulate the motions of atoms in materials such as aluminum is described in this week's Nature Communications journal. This automated approach to "interatomic potential development" could transform the field of computational materials discovery.
"This approach promises to be an important building block for the study of materials damage and aging from first principles," said project lead Justin Smith of Los Alamos National Laboratory. "Simulating the dynamics of interacting atoms is a cornerstone of understanding and developing new materials. Machine learning methods are providing computational scientists new tools to accurately and efficiently conduct these atomistic ...
Neuroblastoma is a cancer that develops in nerve tissue, most commonly in the glands around the kidneys. The gene MYCN is overexpressed in 20-25% of neuroblastoma, and MYCN-amplified neuroblastoma contributes to a considerable percentage of pediatric cancer-related deaths.
Anthony Faber, Ph.D., and a team of researchers at VCU Massey Cancer Center were awarded a grant from the American Cancer Society to study how MYCN and an abundance of iron can drive cancer cell death in neuroblastoma and potentially be targeted with novel treatments. This award is the first part of a potential two-stage grant worth a combined total of $600,000.
"Iron is a double-edged sword in a cancer cell. It can help the cancer grow and survive, but it also creates ...
Schizophrenia, a chronic, neurological brain disorder, affects millions of people around the world. It causes a fracture between a person's thoughts, feelings and behavior. Symptoms include delusions, hallucinations, difficulty processing thoughts and an overall lack of motivation. Schizophrenia patients have a higher suicide rate and more health problems than the general population, and a lower life expectancy.
There is no cure for schizophrenia, but the key to treating it more effectively is to better understand how it arises. And that, according to Ryuta Mizutani, professor of applied biochemistry at Tokai University in Japan, means studying the structure of brain tissue. Specifically, it means comparing the brain tissues of schizophrenia patients with those ...
Even as more people are logging onto popular video chat platforms to connect with colleagues, family and friends during the COVID-19 pandemic, Stanford researchers have a warning for you: Those video calls are likely tiring you out.
Prompted by the recent boom in videoconferencing, communication Professor Jeremy Bailenson, founding director of the Stanford Virtual Human Interaction Lab (VHIL), examined the psychological consequences of spending hours per day on these platforms. Just as "Googling" is something akin to any web search, the term "Zooming" has become ubiquitous and a generic verb to replace videoconferencing. Virtual meetings have skyrocketed, with hundreds of millions happening daily, as social distancing protocols have kept people apart physically.
Biologically active compounds from the marine fungus Penicillium dimorphosporum protect cells from paraquat, the highly toxic herbicide with no remedy, and might enhance the action of some drugs. The fungus was isolated from soft coral collected in the South China Sea during an expedition on the Akademik Oparin research vessel. Scientists of Far Eastern Federal University (FEFU) and G. B. Elyakov Pacific Institute of Bioorganic Chemistry reported the results in Marine Drugs.
Paraquat a herbicide compound highly toxic for animals and humans. About a hundred countries, including the United States, apply it for crop cultivation and weed control. Dozens of countries, including Russia, have banned the ...
A new research study out of the University of Nevada, Reno's School of Community Health Sciences has just been published by the American Journal of Public Health and addresses state preemption of local sugar-sweetened beverage (SSB) taxes, issuing an emerging public health threat. Assistant Professor Eric Crosbie examines commercial determinants of health and public health policy, specifically in industries like tobacco and food and beverage.
"The beverage industry is aggressively attempting to preempt sugar-sweetened beverage taxes at the state level to prevent the diffusion of progressive policies at the local level throughout the United States," Crosbie, an affiliate of the University's Ozmen Institute for Global Studies, said. "Once preemption laws are enacted, ...
There is growing evidence that ketone bodies may be beneficial to heart disease patients regardless of the method of delivery used to increase ketone delivery to the heart. A Journal of the American College of Cardiology review paper examines emerging evidence regarding ketone bodies' effects on the heart and the potential for ketone therapy as a cardiovascular intervention in heart disease patients.
In recent years ketone bodies entered the popular lexicon through the "keto diet," which consists of a very low carbohydrate and high fat diet that endeavors to force the body into ketosis. This is a metabolic ...
A randomized, placebo-controlled Phase 1 clinical trial of two monoclonal antibodies (mAbs) directed against the coronavirus that causes Middle East respiratory syndrome (MERS) found that they were well tolerated and generally safe when administered simultaneously to healthy adults. The experimental mAbs, REGN3048 and REGN3051, target the MERS coronavirus (MERS CoV) spike protein used by the virus to attach to and infect target cells. The mAbs were discovered and developed by scientists at the biopharmaceutical company Regeneron, located in Tarrytown, New York. The trial was sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.
The trial was the first to test the experimental antibodies
Hyperlink Code ...
Inflammatory lung diseases such as asthma, COPD and, most recently, COVID-19, have proven difficult to treat. Current therapies reduce symptoms and do little to stop such diseases from continuing to damage the lungs. Much research into treating chronic inflammatory diseases has focused on blocking chemicals called cytokines, which trigger cascades of molecular events that fuel damaging inflammation.
Now, scientists at Washington University School of Medicine in St. Louis have found that such cytokines can drive inflammation in more ways than previously understood, perhaps revealing new routes ...
Using the symmetries of the systems, people can define various topological invariants to describe different topological states. The topological materials can be accurately discovered by calculating the topological invariants. Recently, researchers found that irreducible representations and compatibility relationships can be used to determine whether a material is topological nontrivial/trivial insulator (satisfying the compatibility relations) or topological semimetal (violating the compatibility relations), which leads to a large number of topological materials predicted by theoretical calculations. However, Weyl semimetals go beyond this paradigm because the existence of Weyl fermions does not need any symmetry protections (except for lattice translation symmetries). At present, ...
LAST 30 PRESS RELEASES:
[Press-News.org] Oxidation processes in combustion engines and in the atmosphere take the same routes
Efficient autoxidation chain reactions demonstrated for the substance group of saturated hydrocarbons