scholarly journals CHEMICAL TRANSFORMATIONS OF ARENES UNDER HYDRODYNAMIC CAVITATION ACTION OF AQUEOUS MEDIA ON ALUMINUM OXIDE

Author(s):  
Денис Владимирович Дудкин ◽  
Ирина Михайловна Федяева ◽  
Людмила Анатольевна Журавлева

На примере эталонного бензола исследованы химические превращения аренов в водной и водно-кислой среде при гидродинамическом кавитационном воздействии на оксиде алюминия. На основе газовой хроматографии и газовой хроматографии с масс-спектральным детектированием установлено, что ведение процесса на поверхности твёрдого катализатора приводит к образованию н-алканов, алкилзамещенных производных циклогексана, алкилзамещённых моноядерных аренов и полиядерных ароматических соединений. Образующиеся соединения имеют в два-три раза большую, в сравнении с исходным ареном, молекулярную массу. Образование из арена новых классов органических соединений обусловлено интенсивным течением реакций гидрирования, алкилирования и дегедроциклизации. Кислая реакция среды подавляет течение свободно-радикального образования н-алканов. Using the example of reference benzene, the chemical transformations of arenes in an aqueous and aqueous-acid medium under hydrodynamic cavitation action on aluminum oxide are studied. Based on gas chromatography and gas chromatography with mass spectral detection, it was found that conducting the process on the surface of a solid catalyst leads to the formation of n-alkanes, alkyl-substituted cyclohexane derivatives, alkyl-substituted mononuclear arenes and polynuclear aromatic compounds. The resulting compounds have two to three times the molecular weight compared to the initial arene. The formation of new classes of organic compounds from arenes is due to the intensive course of hydrogenation, alkylation and dehedrocyclization reactions. The acidic reaction of the medium suppresses the process of free radical formation of n-alkanes.

Author(s):  
Денис Владимирович Дудкин ◽  
Ирина Михайловна Федяева ◽  
Людмила Анатольевна Журавлева

На примере эталонного изооктана исследованы химические превращения изоалканов в водной и водно-кислой среде при гидродинамическом кавитационном воздействии на оксиде алюминия. На основании данных газовой хроматографии и газовой хроматографии с масс-спектральным детектированием установлено, что ведение процесса на поверхности твердого катализатора приводит к образованию н-алканов с большей и меньшей, в сравнении с изооктаном, молекулярной массой. Образующиеся в результате механохимического воздействия н-алканы подвержены дегидроциклизации с образованием циклоалканов, бензола и его алкилпроизводных, трансформирующихся далее в конденсированные полиядерные ароматические соединения. Кислая реакция среды подавляет течение свободно-радикального образование н-алканов, усиливает процессы гетеролитической деструкции образующихся н-алканов, характеризующихся образованием циклоалканов. The chemical transformations of isoalkanes in an aqueous and water-acidic environment under hydrodynamic cavitation action on aluminum oxide were studied using the example of a reference isooctane. Based on the data of gas chromatography and gas chromatography with mass spectral detection, it was found that the process on the surface of a solid catalyst leads to the formation of n-alkanes with a higher and lower molecular weight in comparison with isooctane. N-alkanes formed as a result of mechanochemical action are subject to dehydrocyclization with the formation of cycloalkanes, benzene and its alkyl derivatives, which are further transformed into condensed poly-nuclear aromatic compounds. The acidic reaction of the medium suppresses the free-radical formation of n-alkanes, increases the processes of heterolytic destruction of the formed n-alkanes, characterized by the formation of cycloalkanes.


1991 ◽  
Vol 4 (6) ◽  
pp. 687-691 ◽  
Author(s):  
Zora Djuric ◽  
Domenico A. Luongo ◽  
Dorcas A. Harper

2021 ◽  
Author(s):  
Tara Salter ◽  
Hunter Waite ◽  
Mark Sephton

<p>The inferred subsurface oceans of the icy moons of Jupiter and Saturn, in particular Europa and Enceladus, may contain conditions suitable for life. Plumes of material have been detected from Enceladus and may also be present on Europa. These plumes could contain molecular signs of habitability that could be detected by mass spectrometers on orbiting spacecrafts, such as the upcoming Europa Clipper mission. However, these molecular markers may have degraded between their production and detection, for example by possible hydrothermalism in the subsurface ocean or by UV irradiation once carried into space by the plume. It is important to look at how the biosignatures degrade under different conditions as degradation processes need to be taken into account when analysing the data from life detection missions. We investigate how these two processes affect the mass spectral signals of terrestrial bacteria.</p> <p>Two cyanobacteria samples, <em>Spirulina</em> and <em>Chlorella</em>, were subjected to hydrothermal processing and UV irradiation. Hydrous pyrolysis was used to simulate hydrothermal degradation. Experiments were carried out for 24 or 72 hours at temperatures between 200 and 300 °C. The pyrolyzed contents were subsequently extracted and analysed with gas chromatography-mass spectrometry (GC-MS). UV irradiation was carried out in a vacuum chamber (10<sup>-2</sup> mbar), using a 300 W short arc xenon lamp at UV to near infrared wavelengths (~250 – 800 nm). After UV irradiation, samples were analysed using pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS).</p> <p>Our results show that hydrothermal processing of cyanobacteria affects the compound classes in different ways. Carbohydrate and protein components from the cyanobacteria were significantly affected, with phenol and indole derivatives detected. However, some of the biological fingerprint, such as straight-chain even numbered saturated fatty acids from lipid fragments, remain even at the harshest experimental conditions used in our study. This provides confidence that these diagnostic molecules could be used as fingerprints of biological materials on icy moons.</p>


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