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Wyszukujesz frazę "supercritical" wg kryterium: Temat


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Tytuł:
Zastosowanie zielonych rozpuszczalników w syntezie nienasyconych związków boro- i krzemoorganicznych na drodze reakcji hydrometalacji i sprzęgania Marcińca
Application of green solvents in the synthesis of unsaturated organoboron and organosilicon compounds via catalytic hydrosilylation and Marciniec coupling reactions
Autorzy:
Walkowiak, Jędrzej
Powiązania:
https://bibliotekanauki.pl/articles/1413280.pdf
Data publikacji:
2021
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
hydrometalacja
reakcja sprzęgania
CO2 w stanie nadkrytycznym
ciecze jonowe
poli(glikol etylenowy)
PEG
kataliza homogeniczna
hydrometallation
coupling reaction
supercritical CO2
ionic liquids
poly(ethylene glycol)
homogeneous catalysis
Opis:
Unsaturated organoboron and organosilicon compounds constitute an important class of organometallic compounds, which due to the presence of silyl- or boryl- group attached to Csp2 atoms, their simple and straightforward transformations in coupling and demetallation reactions, found a broad range of applications in the synthesis of fine chemicals or new materials with tailored properties. Such compounds might be synthesized in many transformations but two of them: hydrometallation and Marciniec coupling reactions permitted to obtain compounds with high effectivity, selectivity, and in the case of hydrometallation reactions with excellent atom economy. Most of these processes occur in a homogeneous phase, which ensures excellent yields and stereo- and regioselectivity. On the other hand, such conditions generate problems with catalyst reuse, product separation, and substantial consumption of toxic, volatile organic solvents. According to the assumptions of sustainable development in chemistry, the new procedures, which allow to intensify the process in terms of its efficiency, according to green chemistry rules are of prior importance in modern chemical industry. In this manuscript, the newest achievements in the application of green solvents (ionic liquids, liquid polymers, and supercritical CO2) in catalytic hydrometallation of alkynes and coupling of vinylmetalloids with olefins are discussed. Such an approach builds a new strategy for effective catalyst immobilization and its reuse, the increase of process productivity by the application of repetitive batch processes, and elimination of organic solvents, typically used in these transformations. Selected contributions in this field of chemistry are presented within this review.
Źródło:
Wiadomości Chemiczne; 2021, 75, 1-2; 111-136
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Niekonwencjonalne metody ekstrakcji : ekstrakcja ekologiczna
Unconventional methods of extractions : green extraction
Autorzy:
Nowosad, Karolina
Sujka, Monika
Powiązania:
https://bibliotekanauki.pl/articles/972309.pdf
Data publikacji:
2019
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
ekstrakcja ekologiczna
ekstrakcja płynem nadkrytycznym
ekstrakcja za pomocą ultradźwięków
ekstrakcja za pomocą pulsacyjnego pola elektrycznego
ekstrakcja za pomocą enzymów
green extraction
extraction with supercritical fluid
extraction using ultrasound
extraction using a pulsed electric field
extraction using enzymes
Opis:
Extraction is a method of extracting a chemical from a solution or mixture of solid substances. Conventional methods of extraction, for example, Soxhlet method, require the use of hazardous solvents, are time-consuming and cause degradation of the extracted compounds. Green extraction is characterized by the speed, it gives a quantitative recovery of the extract and does not cause degradation of the components. It takes place at a lower energy consumption than conventional extraction. A number of novel alternatives to conventional extraction techniques have been proposed, including ultrasonic assisted extraction (UAE), supercritical fluid extraction (SFE), enzyme extraction or pulsed electric field. These techniques allow to reduce or eliminate the use of toxic solvents, improve process efficiency and extract quality. The temperature of the above-mentioned processes is low, which affects the behavior of temperature-sensitive substances. The widely used "green extraction" is SFE - extraction with supercritical fluid. The solvent is a supercritical fluid, most often carbon dioxide. Ultrasonic extraction is environmentally friendly, easy to use, versatile and relatively cheap compared to other innovative techniques. This technique can be used to extract, for example, polysaccharides, essential oils, proteins, peptides, dyes, pigments and bioactive substances. Extraction with the use of pulsed electric field is used to extract mainly polyphenols and other bioactive components. Extraction with enzymes (mainly pectinases, cellulases and hemicellulases) is widely used in the food industry, eg for clarifying beer and juices. The extraction yield depends on the solvent system, temperature, enzyme function, substrate availability and pH.
Źródło:
Wiadomości Chemiczne; 2019, 73, 9-10; 465-479
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
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