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    Wyświetlanie 1-15 z 15
    Tytuł:
    Synteza i zastosowanie nowych katalizatorów metatezy olefin
    Synthesis and application of new olefin metathesis catalysts
    Autorzy:
    Hryniewicka, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/172521.pdf
    Data publikacji:
    2014
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    metateza olefin
    katalizatory rutenowe
    pochodne chromanu
    sole imidazolidyniowe
    glikokoniugaty
    olefin metathesis
    ruthenium catalysts
    chromane derivatives
    imidazolinium salts
    glycoconjugates
    Opis:
    Olefin metathesis has emerged as a powerful tool for the formation of carboncarbon double bonds. The success of this methodology has spurred the intense investigation of new catalysts showing a better application profile. The syntheses and the application profiles of the seven new ruthenium metathesis catalysts have been described. Five of them were modified in benzylidene part with 6-hydroxychromane- and 2H-3,4-chromenemethylidene moiety. In chromanol – α-tocopherol model compound, some specific stereoelectronic effects have been observed. Introduction of this ligand to the catalyst may provide new advantageous properties. The other new catalysts contained modified N-heterocyclic carbene ligand (NHC), in which N,N’-mesityl substituents of NHC system were linked with diethylene glycol chain as a “clamping ring”. This ring would contribute to a steric shield of the NHC and ruthenium coordination center. Probably it may inforce a proper orientation of substituents in metallacyclobutane (all-cis), leading to Z-olefin formation. The obtained catalysts were investigated in model reactions: ring closing metathesis, cross metathesis and enyne metathesis. The experiments proved they efficiency. In many reactions the catalysts showed activity comparable or superior to that of commercially available Grubbs and Hoveyda 2nd generation complexes. Stereochemistry Z/E of the cross-metathesis products obtained using new and known complexes were similar as well. The catalysts were applied in the synthesis of a new type of α-tocopherol glycoconjugates. An efficient method of the synthesis Hoveyda 2nd type complexes starting from ruthenium trichloride was developed. It is possible to circumvent using special laboratory equipment and expensive reagents. Hoveyda type complexes can be achieved with very good yield in gram scale. Keywords:
    Źródło:
    Wiadomości Chemiczne; 2014, 68, 11-12; 961-980
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Gold catalysts supported on zeolites
    Katalizatory złotowe osadzone na zeolitach
    Autorzy:
    Walkowiak, Adrian
    Powiązania:
    https://bibliotekanauki.pl/articles/2057912.pdf
    Data publikacji:
    2021
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    heterogeniczne katalizatory złotowe
    nanocząstki złota
    zeolity
    metody modyfikacji zeolitów złotem
    zastosowanie zeolitów modyfikowanych złotem
    proces katalityczny
    heterogeneous gold catalysts
    gold nanoparticles
    zeolites
    methods of zeolites modification with gold
    application of gold-modified zeolites
    catalytic process
    Opis:
    Heterogeneous gold catalysis is a relatively young but dynamically developing field of chemistry. At the end of the 1980s, Masatake Haruta and Graham Hutchings provided experimental evidence of high activity of supported gold catalysts in CO oxidation and acetylene hydrochlorination. Thus, these two researchers challenged the prevailing chemists’ belief that gold is almost completely chemically inert and catalytically inactive. Since then, gold catalysis has been constantly in the centre of attention of a wide array of scientists from around the world. However, there are still many questions about the nature of catalysts containing this noble metal, which inspires in-depth research in this field. From among various potential supports for gold heterogeneous catalysts, zeolites have drawn much attention thanks to several unique properties of this group of materials, among which the most important are high thermal stability and the presence of a system of pores of strictly defined sizes. Zeolites have extremely large surface area, which is desirable to obtain high dispersion of the active phase. The article provides a concise overview of the methods of gold nanoparticles deposition on zeolitic supports and catalytic applications of such materials. The first chapter sheds light on the properties of bulk and nano-sized Au and depicts the background of gold catalysis development. In the following part, a brief description of zeolites and their properties is delivered. The third chapter is devoted entirely to the description of several preparation methods of zeolite-supported gold catalysts and their applications in different catalytic processes. The following post-synthetic methods of zeolite modification with gold are described: impregnation, ion exchange, deposition-reduction, chemical vapour deposition, and grafting. The most important advantages and disadvantages of each method are summarized. The article concludes with a résumé of literature reports concerning the use of zeolitesupported gold catalysts in various processes. Special attention was paid to selective oxidation of alcohols and biomass-derived chemicals (e.g. glucose).
    Źródło:
    Wiadomości Chemiczne; 2021, 75, 11-12; 1259--1293
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Kwasy nukleinowe jako katalizatory reakcji chemicznych
    Nucleic acids as catalysts in chemical reactions
    Autorzy:
    Bukowiecka-Matusiak, M.
    Sobczak, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/172466.pdf
    Data publikacji:
    2012
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    DNA
    kataliza
    synteza asymetryczna
    catalysis
    asymmetric synthesis
    Opis:
    Nucleic acids, due to their specific structure, are effective and durable carriers of genetic information. They have also been used as catalysts in chemical reactions. The right-handed DNA double helix structure has become one of the icons of modern science, and its share in asymmetric catalysis is undeniable. In these reactions, DNA is a source of chirality and proximity between oligonucleotides and complexes of copper during catalysis, what allows a direct transfer of chirality from DNA to the reaction product. Almost complete regioselectivity and excellent enantioselectivity of the aforementioned reactions in water are the evidence of the potential of asymmetry based on DNA. Asymmetric catalysis used in organic synthesis, allows achieving high enantioselectivity. This strategy has been successfully used to create new C-C bonds in Diels- Alder cycloaddition, Friedel-Crafts alkylation and Michael addition using copper complexes with oligonucleotides as catalysts. The important factor to optimize the reaction of asymmetric catalysis in the presence of DNA constitutes its sequence. It has been shown that the use of the double helix DNA can provide the product with higher enantiomeric excess than using the single strand of DNA. In addition, the results of the study suggest that Friedel-Crafts alkylation is accelerated by DNA almost 30-fold. The same correlation is observed in Diels-Alder cycloaddition. Due to promising results, further testing directed at the possibility of using catalytic DNA is being conducted.
    Źródło:
    Wiadomości Chemiczne; 2012, 66, 1-2; 119-137
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Katalizatory wykorzystywane w syntezie biodiesla
    Catalysts used in biodiesel synthesis
    Autorzy:
    Pobłocki, Kacper
    Walczak, Juliusz
    Drzeżdżon, Joanna
    Jacewicz, Dagmara Elżbieta
    Powiązania:
    https://bibliotekanauki.pl/articles/2200588.pdf
    Data publikacji:
    2022
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    katalizator
    biodiesel
    synteza
    biopaliwa
    energia odnawialna
    catalyst
    synthesis
    biofuels
    renewable energy
    Opis:
    Rising prices of electricity, conventional fuels and heating require decisive steps in the further development of technologies based on renewable energy sources. These include geothermal- ; hydrothermal- ; aerothermal- ; and solar energy. Due to the fact that the petrochemical industry is one of the fastest growing branches of the economy, we would like to expand on the topic related to biofuels. Biodiesel is an alternative fuel similar to conventional diesel. It is usually made from animal fat, vegetable oil and waste cooking oil. Its biodegradability, nontoxicity and lack of sulfur and aroma content make it superior to conventional gasoline and diesel. During fuel consumption, it emits fewer air pollutants and greenhouse gases other than nitrogen oxides. In this literature review, we will discuss the latest trends in the world related to catalysts used in biodiesel synthesis.
    Źródło:
    Wiadomości Chemiczne; 2022, 76, 3-4; 129--144
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Zastosowanie spektroskopii w podczerwieni w adsorpcji i katalizie (I)
    Application of infrared spectroscopy in adsorption and catalysis (I)
    Autorzy:
    Sarbek, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/171796.pdf
    Data publikacji:
    2011
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    spektroskopia IR
    chemisorpcja
    adsorbenty
    katalizatory
    IR spectroscopy
    chemisorption
    adsorbents
    catalysts
    Opis:
    The review presents some key results of infrared investigations of adsorbents and catalysts, which were obtained in Laboratory of Adsorption and Catalysis at Adam Mickiewicz University – conducted under the author guidance. After short introduction, review is divided into seven parts. In the first chapter, there was described an application of infrared method devoted to examination of structure of different types of zeolites, such as A, X, Y and mordenite as well as alumina and fly ashes and their modifications. Moreover, some results were presented on cobalt–molybdena catalysts supported on alumina. In the next chapter chemisorption of pyridine and t-butylnitrile (TBN) molecules on the alumina and alumina modified with fluoride and sodium ions as well as Co(Ni)-Mo(W) catalysts supported on alumina were investigated. In the last case intensity of some spectra were correlated with catalytic activity for cumene cracking. Another set of experiments were devoted to transesterification on dealuminated mordenites containing cations of alkaline earths elements and correlation with infrared results. In the next part of review, chemisorption of ethanol was presented. It was concluded, that during chemisorption of ethanol different surface species were produced on alumina, silicaalumina and zeolites X and ZSM-5. In separate chapter, it was considered oligomerization of different alkenes on Phillips catalyst using IR methods. In the last chapter, ways of chemisorption of dihydrobenzenes on cobalt-molybdena catalyst were examined using IR reflectance spectra. It seems that above presented results based on infrared examination will help to better understand adsorbents and catalysts structure and their action during adsorption and catalytic reactions.
    Źródło:
    Wiadomości Chemiczne; 2011, 65, 5-6; 363-394
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Polimery z pamięcią kształtu i ich otrzymywanie
    Shape-memory polymers and their preparation
    Autorzy:
    Andrzejewski, Kewin
    Czyżów, Wiktor
    Jacewicz, Dagmara
    Drzeżdżon, Joanna
    Powiązania:
    https://bibliotekanauki.pl/articles/2086740.pdf
    Data publikacji:
    2022
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    polimery
    synteza
    katalizatory
    zielona chemia
    polymers
    synthesis
    catalysts
    green chemistry
    Opis:
    SMP (shape-memory polymers) is an innovative class of programmable materials responsive to various stimuli. They are attracting increasing attention regarding possible new inventions, industrial use, and overall polymer research. After a brief introduction, this article examines the conventional shape-memory effect, methods of fabrication of shape memory polymers, and molecular and structural requirements for SMP to function. The shape memory behavior of such polymers is thoroughly presented, with the focus being on the thermo- and photo-induced SME. The uses in biomedical and industrial areas are also discussed.
    Źródło:
    Wiadomości Chemiczne; 2022, 76, 3-4; 183--205
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Katalizatory metatezy olefin, modyfikacje liganda NHC
    Olefin metathesis catalysts, modifications on the NHC ligand
    Autorzy:
    Retajczyk, M.
    Wróblewska, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/172547.pdf
    Data publikacji:
    2017
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    metateza olefin
    ligand NHC
    katalizatory Grubbsa
    katalizator Hoveydy-Grubbsa
    olefin metathesis
    Grubbs catalyst
    Hoveyda-Grubbs catalyst
    Opis:
    Olefin metathesis is one of the most important synthetic tools, both in organic and olefin chemistry. Olefin metathesis allows to shorten production time of organic compounds and it is characterized by a smaller amount of by-products and waste in comparison with the classical ways of the synthesis of these compounds. Simultaneously, the conditions at which metathesis is performed are environmentally friendly. This method allows obtaining very valuable compounds, such as: anti-inflammatory agents, fungicides and many others. This causes that olefin metathesis has an important place in the organic synthesis and develops constantly. The first catalysts had undefined structure, therefore, it was difficult to predict the mechanism of their action. Big development metathesis came with the synthesis of catalysts with a clearly defined structure. This article explains what olefin metathesis is and shows applications of olefin metathesis. This work presents catalysts, which possess transition metal in the structure, such as: ruthenium, molybdenum or tungsten. It also shows the comparison of catalysts possess ruthenium (Grubbs catalyst first and second generation and Hoveyda-Grubbs catalyst) taking into account their structure and properties. This work describe carbenes, which improve thermal stability of catalysts compare with complexes containing phosphine. Researchers receive new compounds through modifications on the NHC ligand. In this work are presented modifications of the NHC ligand complexes of ruthenium described in the literature and their influence on such catalytic properties as: activity, selectivity, and efficiency. Modifications concern: heteroatoms, bulky groups and groups, which change electron density. Despite many studies and receiving large amounts of catalysts for this reaction, still a problem is the obtaining of an universal catalyst for all types transitions, that would have a high activity, high efficiency and which could be easily recovered after the reaction.
    Źródło:
    Wiadomości Chemiczne; 2017, 71, 5-6; 323-347
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Karbeny N-heterocykliczne : synteza i zastosowanie
    N-heterocyclic carbenes : synthesis and applications
    Autorzy:
    Malinowska, M.
    Hryniewicka, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/171528.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    karbeny N-heterocykliczne
    sole imidazolidyniowe
    katalizator metatezy
    organokataliza
    reakcja sprzęgania
    N-heterocyclic carbenes
    imidazolinium salts
    methatesis catalysts
    organocatalysis
    coupling reactions
    Opis:
    N-Heterocyclic carbenes (NHCs) are powerful tools in organic chemistry, with numerous applications in academic and industrial laboratories. They are usually defined as singlet carbenes, in which the divalent carbonic centre is connected directly to at least one nitrogen atom in the heterocycle [1]. They have played an important role in organic chemistry ever since the first evidence of their existence. The isolation of stable, free 1,3‑diadamantylimidazol-2-ylidene (IAd, Fig. 1) by Arduengo et al. in 1991 was a milestone in the chemistry of carbenes [2]. From the beginnings as academic curiosities, N‑heterocyclic carbenes today are very useful compounds in a variety of organic transformations (Fig. 13). NHCs are neutral σ-donors, which form very strong bonds with the majority of transition metals (stronger than phosphines). These compounds are easy-to-make ligands with great potential in homogeneous catalysis (mainly ruthenium and palladium complexes) for large number of reactions, including the coupling reactions (Heck, Negishi, Stille, Suzuki or Sonogashira reactions) and olefin metathesis [3]. Moreover, they are very useful as organocatalysts used in the benzoin condensation, the Stetter reaction and ring-opening polymerization (ROP) or transesterification [4]. In this review, we aim to give an overview of the properties and applications of NHCs, which we expect will be a useful introduction for chemists interested in studying and applying these important compounds. The first part of this review is devoted to the main synthetic routes to NHCs, their properties and reactivity. In the second part we describe the metal complexes with NHCs as homogeneous catalysts and their applications in various types of reactions. At the end of this part of the paper the use of NHCs as organocatalysts is presented.
    Źródło:
    Wiadomości Chemiczne; 2015, 69, 3-4; 227-253
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Zastosowanie spektroskopii w podczerwieni w adsorpcji i katalizie (II)
    Application of infrared spectroscopy in adsorption and catalysis (II)
    Autorzy:
    Sarbak, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/171816.pdf
    Data publikacji:
    2011
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    spektroskopia IR
    tlenek węgla
    chemisorpcja
    powierzchnia katalizatorów
    depozyt węglowy
    katalizatory
    FTIR
    carbon monoxide
    chemisorption
    catalyst surface
    coke deposition
    catalysts
    Opis:
    The review presents important results on infrared examination of adsorbents and catalysts, which were obtained in Laboratory of Adsorption and Catalysis in Environmental Protection at Adam Mickiewicz University – conducted under the author guidance. In the first chapter results on chemisorption of carbon monoxide on Pt and Pt–Sn catalysts supported on various carriers such as alumina with different specific surface area and silica were described. For these catalysts different amount of Pt or Pt and Sn were used. Besides, catalysts obtained by different preparation procedures were also investigated. Second chapter contains description of coke deposit on alumina and silica supports as well as on Pt and Pt–Sn catalysts supported on above mentioned carriers. Special attention was also devoted to coke deposition on aluminosilicate, zeolite type A, X and ZSM-5 and Pt–Cr, Pt-Mo and Pt-W catalysts supported on alumina. Moreover, coke deposition on alumina contained chloride ions and molybdena- (VI) ions on alumina activated by reduction and sulfidation were also investigated. It seems that above presented results based on infrared examination will help to better understand of adsorbents and catalysts structure and their action during adsorption and catalytic reactions.
    Źródło:
    Wiadomości Chemiczne; 2011, 65, 5-6; 395-426
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Kompozyty uporządkowanych krzemionkowych materiałów mezoporowatych z rodziny M41S
    Composites of ordered silica mesoporous materials from the M41S family
    Autorzy:
    Zabłocka, I.
    Wysocka-Żołopa, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/172593.pdf
    Data publikacji:
    2018
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    uporządkowana mezoporowata krzemionka
    kompozyty
    katalizatory
    sorbenty
    polimery
    ordered mesoporous silica
    composites
    catalysts
    sorbents
    polymers
    Opis:
    Report on the discovery of a new group of ordered mesoporous M41S molecular sieves initiated the extensive use of these materials in scientific research. There were 3 different pores differing in the pore system, generally called MCM (Mobil Composition of Matter): MCM-41 with hexagonal structure, MCM-48 with regular structure and MCM-50 with lamellar structure (Fig. 1). The first proposed synthesis of materials from the M41S group is based on the use of organic surfactants as matrices [4]. The applied modifications of the synthesis method allowed, among others for easy and fairly accurate control of morphology, change of physical properties of the obtained silicas and have an impact on time, cost and simplicity of execution [12, 16, 23–34]. They concerned the use of additional organic and inorganic substances [23–25], changes in reaction conditions [12, 16, 26–29], as well as the use of innovative surfactants [30–34]. Due to its porous structure, the mesoporous silica creates opportunities to improve the properties of many materials, which is why many composites have been synthesized with its used in catalysing, sorption or improving the properties of polymers. Mesoporous titanium catalysts (Ti-MCM-41) were used in the catalysis of the redox reaction or as photocatalysts [44–71]. In addition to titanium, other transition metals have also been introduced into the MCM-41 network, including vanadium, zirconium, niobium, iron, ruthenium, silver, nickel, tungsten [43, 72–98] used as catalysts in organic reactions or as catalysts in the ozonation process [ 99–111]. Polymer composites belong to hybrid materials made of an organic polymer matrix dispersed in inorganic silica. Conductive polymers such as polyaniline and polypyrrole are often used in mesoporous polymer composites due to the ability to conduct electric current [117–133]. The main use of composites with mesoporous silica in sorption processes is to use them to remove impurities from water and gases. MCM-48 composites with various amines were used in the carbon dioxide adsorption process, and composites with niobium and nickel in deodorization processes [141–155]. Synthesis of composites with organic compounds allows to obtain good adsorbents of heavy metals such as: lead, cadmium, arsenic, copper, nickel, zinc and mercury [146–152].
    Źródło:
    Wiadomości Chemiczne; 2018, 72, 11-12; 841-865
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Katalizatory palladowe immobilizowane w materiałach typu MOF aktywne w reakcjach uwodornienia
    Palladium catalysts immobilized in MOF materials active in hydrogenation reactions
    Autorzy:
    Augustyniak, Adam W.
    Trzeciak, Anna M.
    Powiązania:
    https://bibliotekanauki.pl/articles/172135.pdf
    Data publikacji:
    2019
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    sieci metaliczno-organiczne
    kataliza
    pallad
    uwodornienie
    selektywność
    metal-organic frameworks
    catalysis
    palladium
    hydrogenation
    reaction
    selectivity
    Opis:
    Palladium immobilized in metal-organic frameworks (MOF) exhibit promising catalytic properties in hydrogenation of different unsaturated substrates. Due to the specific porous and crystalline structure MOFs can contribute in bonding and activation of organic substrates, increasing catalytic efficiency of Pd@MOF composites. The superior tunability of MOFs structures enables to design highly selective catalysts for hydrogenation of different substrates, such as olefins, esters, ketones, alcohols or alkynes. Due to the synergistic effects of palladium and MOF not only high activity but also high selectivity can be achieved. The article presents representative examples of MOF-based palladium catalysts for hydrogenation to illustrate perspectives, also technological, of their application.
    Źródło:
    Wiadomości Chemiczne; 2019, 73, 3-4; 221-241
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Struktura i reaktywność związków alkoksy-cynkowych jako inicjatorów/katalizatorów polimeryzacji estrów cynicznych
    Structure and reactivity of alkoxy-zinc compounds as initiators/catalysts in the polymerization of cyclic esters
    Autorzy:
    Petrus, Rafał
    Utko, Józef
    Sobota, Piotr
    Powiązania:
    https://bibliotekanauki.pl/articles/1413188.pdf
    Data publikacji:
    2021
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    związki alkoksylowe cynku
    polilaktyd
    polimeryzacja
    laktyd
    kwas mlekowy
    zinc alkoxides
    polylactide
    polymerization
    lactide
    lactic acid
    Opis:
    This review focuses on advances in the synthesis and structural chemistry of zinc alkoxide compounds for use in the catalytic ring-opening polymerization (ROP) of lactides (LAs). This route was used for the preparation of lactic acid based polymers - referred to as polylactides (PLAs). These polyesters have ecofriendly properties such as renewability, biocompatibility, and biodegradability, and are therefore among the most promising green polymers. PLAs have found numerous specialty applications in the biomedical industry, such as biodegradable screws and sutures, scaffolds for tissue engineering, matrices for controlled drug delivery systems, and environmentally friendly food-packaging materials. In industry, PLAs were synthesized by bulk polymerization of LA using tin(II) alkoxides synthesized in situ from tin(II) 2-ethylhexanoate. The toxicity associated with most tin compounds is a considerable drawback in the case of biomedical applications. There has therefore been much research devoted to finding well- defined complexes of high activity containing biologically benign metals. In this context, zinc alkoxides are very attractive non-toxic initiators for the synthesis of polymers that could be used in medical and environmental fields. The most broadly applied representations of zinc initiators for ROP of LA are zinc carboxylates, ß-diketonates, ß-diketiminates, phenolates and bisphenolates, trispyrazolyl- and trisindazolyl-borates, heteroscorpionates, aminophenolates, Schiff base, and iminealkoxylates. The mentioned above initiators were classified and analyzed in the context of their coordination chemistry and revealed catalytic activity in the ROP of LA. The review contains only pioneering/groundbreaking works that allowed for setting new research paths for each of the described groups of initiators, showing how this theme has changed over the last several decades.
    Źródło:
    Wiadomości Chemiczne; 2021, 75, 3-4; 343-373
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Kataliza przeniesienia międzyfazowego jako nowoczesna technika w syntezie organicznej
    Phase-transfer catalysis as a modern technique in organic synthesis
    Autorzy:
    Siewniak, Agnieszka
    Chrobok, Anna
    Powiązania:
    https://bibliotekanauki.pl/articles/1853730.pdf
    Data publikacji:
    2021
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    kataliza przeniesienia międzyfazowego
    czwartorzędowe sole amoniowe
    poli glikole etylenowe
    katalizatory chiralne przeniesienia międzyfazowego
    phase-transfer catalysis
    quaternary ammonium salts
    polyethylene glycols
    chiral phase-transfer catalysts
    Opis:
    Phase-transfer catalysis (PTC) has been already known for 60 years and has an established position both on a laboratory and industrial scale. It is an energy-saving technique, ensuring high yields and selectivity under mild conditions. PTC is successfully used, among others, in the pharmaceutical, polymer, agrochemical industries, for the production of dyes, fragrances and flavors, to name a few. Currently, the development of phase-transfer catalysis is focused mainly on the search for active catalysts as well as extending the scope of its applications. In particular, catalysts immobilized on an insoluble carrier, which can be easily separated from the reaction mixture and recycled many times, are of great interest. The growing demand for chiral compounds has resulted in the development of phase-transfer catalysts which, while retaining the advantages of conventional PTC, will allow to obtain a product with high enantiomeric excess. This work characterizes the phase-transfer catalysis and presents examples of its applications in organic synthesis.
    Źródło:
    Wiadomości Chemiczne; 2021, 75, 9-10; 1297-1315
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Fotokatalityczna degradacja herbicydów : nowe katalizatory na bazie TiO2
    Photocatalytic degradation of herbicydes : new catalysts based on TiO2
    Autorzy:
    Ożóg, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/172094.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    tlenek tytanu
    TiO2
    degradacja fotokatalityczna
    kwas 2,4-dichlorofenoksyoctowy
    2,4-D
    kwas 2,4,5-trichlorofenoksyoctowy
    2,4,5-T
    4G-PHOTOCAT
    titanium dioxide
    photocatalytic degradation
    2,4-dichlorophenoxyacetic
    2,4,5-trichlorophenoxyacetic
    Opis:
    Over the past few decades a rapid increase in standard of living is observed. Rapid urbanization and development of new technologies, which are focused on the needs of a modern society, influence negatively the environment. The present policy of sustainable development is focused on the principles of rational use of scarce resources and raw materials. New technologies should comply with a number of requirements: efficiency, low costs and a low impact on the environment. Photocatalytic processes are the answer for these requirements. Photocatalysis can be used in many aspects of everyday life, offering self-cleaning surfaces, photo-drugs (e.g. for photodynamic therapy) and even photovoltaic devices. Photocatalytic degradation of pollutants in the presence of inorganic photocatalysts (e.g. TiO2 or ZnO) is one of the available methods of removing impurities from aqueous and gaseous phases. The main advantage of this process is the lack of wastes and formation of carbon dioxide, water and simple inorganic ions as end- -products. The aim of our work was to develop new TiO2-based photocatalysts doped with tungsten and molybdenum oxides. A series of materials with different content of the dopants, calcined at various temperatures, was prepared. The photocatalytic activity of the materials was determined following the degradation of two model herbicides: 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). These compounds are used for the control of weed growth on crop plantations, but in a high dosage they can lead to destruction of the plants. They are readily soluble in water, therefore their use is simple, but brings a great risk to aquatic organisms and people. Photocatalytic degradation of herbicides is the main goal of the 4G-PHOTOCAT project. The efforts are directed towards development of a low-cost photocatalytic paint, that could be used in reactors for groundwater purification. The active ingredient of the paint is a composite material based on TiO2 modified with other metal oxides.
    Źródło:
    Wiadomości Chemiczne; 2015, 69, 7-8; 606-616
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Metody badań niejednorodności energetycznej powierzchni katalizatorów i adsorbentów
    Methods of investigation energetical heterogeneity on the surface of catalysts and adsorbents
    Autorzy:
    Woszczyński, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/172199.pdf
    Data publikacji:
    2013
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    heterogeniczność
    niejednorodność energetyczna
    równanie Fredholma
    adsorpcja
    kalorymetria
    chromatografia
    odwrócona chromatografia gazowa
    chromatografia z odwróconym przepływem
    programowana termiczna desorpcja
    heterogeneity
    adsorbent
    catalyst
    Fredholm equation
    adsorption
    calorimetry
    chromatography
    inverse gas chromatography (IGC)
    IGC
    reverse-flow IGC (RF-IGC )
    programmed thermal desorption (TPD)
    TPD
    Opis:
    The knowledge of the properties and a surface structure of catalysts and adsorbents is of great importance in the selection of these materials to the relevant objectives. Interesting structural information can be obtained in many ways, for example: with the use of spectroscopic or microscopic techniques or in direct examination of the adsorption isotherms. This article focuses on these last-mentioned methods, which can be a source of information on energy heterogeneity of the catalyst or adsorbent surface. Heterogeneity is usually determined by measuring adsorption isotherms of a selected adsorbate on the examined adsorbent, which is dependent of adsorbate coverage on the adsorbent relative to the equilibrium pressure under isothermal conditions. Among the many mathematical models describing this relationship particularly interesting is the adsorption isotherm model described by generalized integral Fredholm equation. The solution of this equation is density function with the assumed local isotherm model. There are different ways to solve the Fredholm equation, depending on measurement methods of obtained adsorption isotherms. For example, an application of static techniques (gravimetric or volumetric) needs to use advanced, sophisticated numerical methods for directly solving integral equations, other techniques (e.g. such as calorimetric or chromatographic) provide specific values that simplify these calculations. The resulting energy density function allows to observe active centers as peaks or inflections of the curve on the energy spectrum graph.
    Źródło:
    Wiadomości Chemiczne; 2013, 67, 7-8; 635-664
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-15 z 15

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