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Wyszukujesz frazę "catalysis" wg kryterium: Temat


Tytuł:
Theoretical model explaining the relationship between the molecular mass and the activation energy of the enzyme revealed by a large-scale analysis of bioinformatics data
Autorzy:
Pawlowski, Piotr
Zielenkiewicz, Piotr
Powiązania:
https://bibliotekanauki.pl/articles/1039585.pdf
Data publikacji:
2013
Wydawca:
Polskie Towarzystwo Biochemiczne
Tematy:
statistics
catalysis
turnover
enzyme
molecular mass
Opis:
A general dependence of the enzyme catalytic rate on its mass was revealed when a statistical analysis of 17065 records from the EMP database was performed. The estimated activation energy of the catalytic process decreases asymptotically with the enzyme molecular mass increase. The proposed theoretical model postulates the existence of an intermediate complex of the enzyme and the departing product. It allows for the explanation of the discovered mass-energy relationship, as an effect of the global enzyme-product interactions during complex dissociation. Fitted parameters of the model seem to be in agreement with those widely accepted for the van der Waals energy of molecular interactions. Their values also agree with the picture of the hydrogen bonding in the catalytic process and suggest that surface walk can be the favorable way of the product departure.
Źródło:
Acta Biochimica Polonica; 2013, 60, 2; 239-247
0001-527X
Pojawia się w:
Acta Biochimica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mild Method to Synthesize TATB by Amination of 1,3,5-Trialkoxy-2,4,6-Trinitrobenzene under Phase Transfer Catalysis Conditions
Autorzy:
Chang, T.
Li, B.
Chen, L.
Ge, L.
Lu, M.
Powiązania:
https://bibliotekanauki.pl/articles/358103.pdf
Data publikacji:
2017
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
TATB
phase transfer catalysis
atmospheric amination reaction
Opis:
Nucleophilic amination, as a vital step in the synthesis of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) using 1,3,5-trialkoxy-2,4,6-trinitrobenzene (TORTNB) and aqueous ammonia as the starting materials and catalyzed by phase transfer catalysis (PTCs) under mild conditions is described. Various phase transfer catalysts, such as crown ethers, tertiary amines, quaternary ammonium salts, poly ethers and cyclodextrin, and various experimental parameters, such as no. of equivalents of PTC, mole ratio of ammonium hydroxide to the starting material, reaction time, reaction temperature and cycle times of the organic phase were investigated. The crown ethers, especially 18-crown-6, show good catalytic activity and re-usability for the amination of 1,3,5-triethoxy-2,4,6-trinitrobenzene giving a yield of 96.52%. This makes for a safe process and suitable for scale-up, because the reactions are carried out under atmospheric conditions. The material synthesised by the new system was characterized by DSC, SEM and LPS.
Źródło:
Central European Journal of Energetic Materials; 2017, 14, 1; 47-59
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
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:
Screening of the catalytic activity of pd0 and pd2+- supported on chitosan beads and cryogels
Autorzy:
Pestov, Aleksandr
Mekhaev, Aleksandr
Privar, Yuliya
Prokuda, Natalya
Modin, Evgeniy
Bratskaya, Svetlana
Powiązania:
https://bibliotekanauki.pl/articles/1034532.pdf
Data publikacji:
2018
Wydawca:
Sieć Badawcza Łukasiewicz - Polskie Towarzystwo Chitynowe
Tematy:
Heck reaction
catalysis
chitosan
cryogel
hydrodechlorination
hydrogenation
Opis:
Here, we report the results of screening of the catalytic activity of Pd-containing chitosan beads and cryogels in the cross-coupling reaction, hydrogenation of alkenes, nitro-, and carbonyl compounds and the hydrodechlorination of chlorophenols. Pd0-containing chitosan beads and cryogels show moderate catalytic activity in the reduction of alkenes and nitroaromatics. The conversion of nitroaromatics decreases for substrates with electron-withdrawing substituents, while the conversion of alkenes increases with the activation of carbon-carbon double bonds. For several substrates, a significant difference in kinetics and conversion degrees was observed for Pd nanoparticles supported on chitosan beads and cryogels. It was found that conversion in the hydrodechlorination reaction depends on substrate structure, being higher for substrates containing substituents with a positive mesomeric effect. Pd2+-chitosan catalysts showed high catalytic activity in cross-coupling (Heck reaction) offering the following advantages over known catalytic systems: lower reaction temperature, the selective functionalisation of C-I bonds, and the possibility to perform reactions with iodobenzene without base addition.
Źródło:
Progress on Chemistry and Application of Chitin and its Derivatives; 2018, 23; 149-158
1896-5644
Pojawia się w:
Progress on Chemistry and Application of Chitin and its Derivatives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Adam Bielański (1912-2016)
Autorzy:
Witko, Małgorzata
Powiązania:
https://bibliotekanauki.pl/articles/703985.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Adam Bielański
chemistry
inorganic chemistry
catalysis
surface chemistry
Opis:
On September 4, died at the age of 100 Adam Bielański, Professor of Chemistry, an outstanding scientist, widely recognized authority in the field of inorganic chemistry, catalysis and surface chemistry.
Źródło:
Nauka; 2016, 4
1231-8515
Pojawia się w:
Nauka
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Combining laccase with Cu(salen) catalysts for oxidation of kraft lignin
Autorzy:
Zhou, X.-F.
Tang, K.
Powiązania:
https://bibliotekanauki.pl/articles/52753.pdf
Data publikacji:
2016
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Technologii Drewna
Tematy:
laccase
catalysis
oxidation
kraft lignin
monomeric aromatic chemical
Źródło:
Drewno. Prace Naukowe. Doniesienia. Komunikaty; 2016, 59, 198
1644-3985
Pojawia się w:
Drewno. Prace Naukowe. Doniesienia. Komunikaty
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modelling of regeneration and filtration mechanism in diesel particulate filter for development of composite regeneration emission control system
Autorzy:
Kurien, C.
Srivastava, A. K.
Naudin, J.
Powiązania:
https://bibliotekanauki.pl/articles/140328.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
catalysis
filtration
regeneration
soot
katalizator
filtracja
regeneracja
sadza
Opis:
Pre-treatment techniques employed for exhaust emission control of compression ignition engines were found to reduce the emission levels by small percentage only, failing to meet the required emission regulations. Post-treatment technique including diesel particulate filtration, diesel oxidation catalysis and selective catalytic reduction is found to be an effective solution. While the fuel-based regeneration of diesel particulate filter leads to uncontrolled combustion affecting the durability of the filter. Development of an effective regeneration system is one of the major technical challenges faced by automotive industry for meeting emission norms. A composite regeneration system with the application of microwave energy is proposed in this paper. As an initial phase, a three-dimensional model of the system is developed and its flow analysisis carried out by considering the case of single channel flow. Simulation of the regeneration process is also done by developing a Simulink model. The results of simulation showed that an engine running continuously for a period of 24 hours would require three regenerations.
Źródło:
Archive of Mechanical Engineering; 2018, LXV, 2; 277-290
0004-0738
Pojawia się w:
Archive of Mechanical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Titanium compounds and their impact on the transformation of air pollutants
Autorzy:
Bok, A.
Bożym, M.
Powiązania:
https://bibliotekanauki.pl/articles/184203.pdf
Data publikacji:
2015
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
titanium
TiO2
photo-catalysis process
wear
pollutant
catalyst
Opis:
Titanium, as a transition metal, demonstrates a high mechanical strength. It is light and corrosion resistant. The estimation of the environmental impact of the use of machine parts that grains are freed from and contact the surface of titanium alloys by wear is buffing. Due to its catalytic action, TiO2 is nowadays added to asphalt, concrete, exterior paints for elevation, self-cleaning glass and protective coatings. It is also present in clothes, food (E171), cosmetics (CI 77891) and textiles. The research on the toxicity of titanium and its compounds points towards their neutral character, however an adverse impact is also observed in nature. TiO2 may affect air quality. It promotes free radicals and ozone origination. The properties and direction of the use of titanium compounds and their inf luence on the circulation of pollutants are described below.
Źródło:
Geology, Geophysics and Environment; 2015, 41, 3; 213-222
2299-8004
2353-0790
Pojawia się w:
Geology, Geophysics and Environment
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental Insight into the Catalytic Mechanism of MFe2O4 (M = Ni, Zn and Co) on the Thermal Decomposition of TKX-50
Autorzy:
Hou, Xiaoting
Zhang, Ming
Zhao, Fengqi
Yang, Yanjing
An, Ting
Li, Hui
Pan, Qing
Wang, Xiaohong
Zhang, Kun
Powiązania:
https://bibliotekanauki.pl/articles/27788010.pdf
Data publikacji:
2021
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
bimetallic iron oxide
thermal decomposition
TKX-50
catalysis
mechanism
Opis:
Synthesized dihydroxylammonium 5,5’-bistetrazole-1,1’-diolate (TKX-50) owes its outstanding application prospects in the field of insensitive solid propellants not only to its high energetic performance but also to its low mechanical sensitivity. Based on the excellent catalytic activity of bimetallic iron oxides for the thermal decomposition of TKX-50, the catalytic mechanism of bimetallic iron oxides (NiFe2O4, ZnFe2O4 and CoFe2O4) for TKX-50 pyrolysis has been explored. For this study, the decomposition process of TKX-50, before and after mixing with the bimetallic iron oxides NiFe2O4, ZnFe2O4 and CoFe2O4 was monitored by in-situ FTIR and gas-phase MS-FTIR instruments. Of the different catalysts, ZnFe2O4 gave the best result for reducing the initial decomposition temperature of TKX-50. Additionally, the activation energy of functional group cleavage of TKX-50, before and after mixing with ZnFe2O4, was also calculated for mechanism analysis from the results of the in-situ FTIR measurements. The results showed that the condensate and the gas-phase decomposition products of TKX-50 remained unchanged after mixing with different catalysts, while the activation energy of tetrazole ring cleavage was significantly reduced. The results of this study will be helpful for the rational design of insensitive solid propellant formulations containing TKX-50, and for understanding the pyrolysis mechanisms of TKX-50 before and after mixing with the efficient catalyst ZnFe2O4.
Źródło:
Central European Journal of Energetic Materials; 2021, 18, 2; 223--244
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ribozymes of the hepatitis delta virus: Recent findings on their structure, mechanism of catalysis and possible applications.
Autorzy:
Ciesiołka, Jerzy
Wrzesinski, Jan
Łęgiewicz, Michał
Smólska, Barbara
Dutkiewicz, Mariola
Powiązania:
https://bibliotekanauki.pl/articles/1044131.pdf
Data publikacji:
2001
Wydawca:
Polskie Towarzystwo Biochemiczne
Tematy:
RNA structure
RNA catalysis
HDV
hepatitis delta virus
ribozyme
Opis:
Although the delta ribozymes have been studied for more than ten years the most important information concerning their structure and mechanism of catalysis were only obtained very recently. The crystal structure of the genomic delta ribozyme turns out to be an excellent example of the extraordinary properties of RNA molecules to fold into uniquely compact structures. Details of the X-ray structure have greatly stimulated further studies on the folding of the ribozymes into functionally active molecules as well as on the mechanism of RNA catalysis. The ability of the delta ribozymes to carry out general acid-base catalysis by nucleotide side chains has been assumed in two proposed mechanisms of self-cleavage. Recently, considerable progress has been also made in characterizing the catalytic properties of trans-acting ribozyme variants that are potentially attractive tools in the strategy of directed RNA degradation.
Źródło:
Acta Biochimica Polonica; 2001, 48, 2; 409-418
0001-527X
Pojawia się w:
Acta Biochimica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Montmorillonite as the catalyst in oxidation of limonene with hydrogen peroxide and in isomerization of limonene
Autorzy:
Malko, M.
Antosik, A. K.
Wróblewska, A.
Czech, Z.
Wilpiszewska, K.
Miądlicki, P.
Michalkiewicz, B.
Powiązania:
https://bibliotekanauki.pl/articles/779496.pdf
Data publikacji:
2017
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
montmorillonite
R-(+)-limonene
oxidation
isomerization
hydrogen peroxide
heterogeneous catalysis
Opis:
In our studies montmorillonite (MMT) was used as the heterogeneous, natural catalyst. This material was previously prepared by bentonite purification with help of the sedimentation method. The obtained catalyst was characterized by: XRD, SEM, BET and EDX. Catalytic tests with montmorillonite as the catalyst were performed with the natural terpene – R-(+)-limonene. This compound was oxidized with hydrogen peroxide and, moreover, in the separate process it was also isomerized. As the main products of limonene oxidation were detected: (1,2-8,9)-diepoxide, perillyl alcohol, carvone, carveol, 1,2-epoxylimonene and 1,2-epoxylimonene diol. In the isomerization of R-(+)-limonene were formed: terpinenes, terpinolene and p-cymene. Conversions of limonene in these processes reached 70–80%. The application of montmorillonite (the natural of origin) in the studied processes (oxidation and isomerization) is environmentally friendly, it allows to reduce the cost of the studied processes. The resulting products of the processes of oxidation and isomerization of R-(+)-limonene have many applications.
Źródło:
Polish Journal of Chemical Technology; 2017, 19, 4; 50-58
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Biomasa - źródło cennych związków organicznych
Biomass a source of valuable organic compounds
Autorzy:
Retajczyk, J.
Wróblewska, A.
Powiązania:
https://bibliotekanauki.pl/articles/172682.pdf
Data publikacji:
2017
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
biomasa
glukoza
glicerol
uwodornienie
kataliza
glucose
glycerol
monoterpenes
hydrogenation
catalysis
Opis:
So far, much attention was paid to processes which allow to obtain biofuels from biomass and less important was receiving from biomass valuable chemical compounds. Biomass is a source of a variety of compounds, such as: hydrocarbons, triglycerides, glycerol, hydroksymetylofurfural, cellulose, hemicellulose and pentoses, lignin and lignocellulose. Taking into account the application of the mentioned above compounds, a large number of articles describing catalytic conversion of biomass to valuable chemical compounds has been written during last 10 years. The articles presented specific types of reactions for compounds contained in biomass, such as: hydrolysis, hydrogenation or isomerization, which allow to obtain valuable products. The reactions are catalyzed among others by: metals deposited on the activated carbon, metal oxides, alloys and zeolites. Researchers still improve processes, adapting them to the structure of highly functionalized particles contained in biomass and process needs. At the same time, scientist focused on cost reduction. Renewable raw materials are converted to the intermediates in physical, chemical and physicochemical processes. Next, obtained intermediates are used for receiving valuable chemicals, such as: lubricants, solvents and products that were previously obtained from petroleum. This work presents the conversion of biomass to compounds which have been already prepared by conventional synthetic methods. Besides chemical pure compounds, catalytic reactions with using metals, lead to obtain mixtures of compounds which can be used for the large volume production: additives for paper, paints, resins, foams, surfactants, lubricants and plasticizers. In the chemical industry for many years it has been placed emphasis on processes that are environmentally friendly. Scientists have also focused on improving the activity of used catalysts and the selectivity of products.
Źródło:
Wiadomości Chemiczne; 2017, 71, 3-4; 241-262
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kataliza heterogeniczna
Autorzy:
Rachwalik, R.
Ogonowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/273835.pdf
Data publikacji:
2010
Wydawca:
Roble
Tematy:
kataliza heterogeniczna
katalizatory heterogeniczne
jonon
heterogeneous catalysis
heterogeneous catalysts
ionium
Źródło:
LAB Laboratoria, Aparatura, Badania; 2010, 15, 2; 19-26
1427-5619
Pojawia się w:
LAB Laboratoria, Aparatura, Badania
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Improving the environmental performance of the internal combustion engine by the use of in-cylinder catalyst
Autorzy:
Andrych-Zalewska, M.
Powiązania:
https://bibliotekanauki.pl/articles/133717.pdf
Data publikacji:
2017
Wydawca:
Polskie Towarzystwo Naukowe Silników Spalinowych
Tematy:
IC engine
catalyst
in-cylinder catalysis
silnik spalinowy
katalizator
kataliza
Opis:
The problems of using the inner surfaces of a combustion chamber as catalytic converters in order to reduce the harmful exhaust emissions were discussed in this paper. The proper choice of the catalyst is one of the most important issues. The interaction between the burned mixture and the catalyst is not limited by the kinetics of the chemical reactions but depends primarily on the flow rate of the reactants to the catalyst surface during combustion. The lifespan of a catalytic layer is determined by the application technique, where plasma spraying is the most popular and most accessible method. However, when it comes to the catalytic coating durability, it is not an efficient option, as ion implantation is indicated shows greater potential in this respect. In this research the coating of aluminum titanium and chromium-nickel have been applied to the engine head and the piston crown. Then the modified catalytic parts were used in a CI combustion engine and the obtained emission results were compared with the reference results. Another set of tests was performed for an SI engine, powered with gasoline and methane, where the piston crown was covered with a thermal layer of zirconium oxide and a catalytic layer of platinum. The beneficial effects of these in-cylinder catalysts on exhaust emissions and the possible problems in the wide spread use of such solutions have been presented.
Źródło:
Combustion Engines; 2017, 56, 1; 129-132
2300-9896
2658-1442
Pojawia się w:
Combustion Engines
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Efficient method for Knoevenagel condensation in aqueous solution of amino acid ionic liquids (AAILs)
Autorzy:
Ossowicz, P.
Rozwadowski, Z.
Gano, M.
Janus, E.
Powiązania:
https://bibliotekanauki.pl/articles/779648.pdf
Data publikacji:
2016
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
recycling
catalysis in water
amino acid ionic liquids
Knoevenagel reaction
Opis:
This work reports on the use of the amino acid ionic liquids (AAILs) which have been used as catalysts in Knoevenagel condensation of various aldehydes with malononitrile. For research we use tetrabutylammonium ionic liquids based on eight natural amino acids. The reaction was carried out in an aqueous medium. Using water as solvent provided efficient and simple method of isolation of pure product with high yield. Moreover, amino acid ionic liquid dissolved in water could be reused many times without any loss of its catalytic activity. The influence of the anion was studied. Moreover the effect of technological parameters such as: the temperature, the catalyst content, and the reaction time on yield of reaction were investigated.
Źródło:
Polish Journal of Chemical Technology; 2016, 18, 4; 90-95
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł

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