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  Subjects -> MATHEMATICS (Total: 966 journals)
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    - MATHEMATICS (711 journals)
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MATHEMATICS (711 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 538 Journals sorted alphabetically
Abakós     Open Access   (Followers: 4)
Abhandlungen aus dem Mathematischen Seminar der Universitat Hamburg     Hybrid Journal   (Followers: 4)
Academic Voices : A Multidisciplinary Journal     Open Access   (Followers: 2)
Accounting Perspectives     Full-text available via subscription   (Followers: 7)
ACM Transactions on Algorithms (TALG)     Hybrid Journal   (Followers: 15)
ACM Transactions on Computational Logic (TOCL)     Hybrid Journal   (Followers: 3)
ACM Transactions on Mathematical Software (TOMS)     Hybrid Journal   (Followers: 6)
ACS Applied Materials & Interfaces     Full-text available via subscription   (Followers: 29)
Acta Applicandae Mathematicae     Hybrid Journal   (Followers: 1)
Acta Mathematica     Hybrid Journal   (Followers: 12)
Acta Mathematica Hungarica     Hybrid Journal   (Followers: 2)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5)
Acta Mathematica Sinica, English Series     Hybrid Journal   (Followers: 6)
Acta Mathematica Vietnamica     Hybrid Journal  
Acta Mathematicae Applicatae Sinica, English Series     Hybrid Journal  
Advanced Science Letters     Full-text available via subscription   (Followers: 10)
Advances in Applied Clifford Algebras     Hybrid Journal   (Followers: 4)
Advances in Calculus of Variations     Hybrid Journal   (Followers: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5)
Advances in Complex Systems     Hybrid Journal   (Followers: 7)
Advances in Computational Mathematics     Hybrid Journal   (Followers: 19)
Advances in Decision Sciences     Open Access   (Followers: 3)
Advances in Difference Equations     Open Access   (Followers: 3)
Advances in Fixed Point Theory     Open Access   (Followers: 5)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 13)
Advances in Linear Algebra & Matrix Theory     Open Access   (Followers: 3)
Advances in Materials Sciences     Open Access   (Followers: 14)
Advances in Mathematical Physics     Open Access   (Followers: 4)
Advances in Mathematics     Full-text available via subscription   (Followers: 11)
Advances in Numerical Analysis     Open Access   (Followers: 5)
Advances in Operations Research     Open Access   (Followers: 12)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Pure and Applied Mathematics     Hybrid Journal   (Followers: 6)
Advances in Pure Mathematics     Open Access   (Followers: 6)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Aequationes Mathematicae     Hybrid Journal   (Followers: 2)
African Journal of Educational Studies in Mathematics and Sciences     Full-text available via subscription   (Followers: 5)
African Journal of Mathematics and Computer Science Research     Open Access   (Followers: 4)
Afrika Matematika     Hybrid Journal   (Followers: 1)
Air, Soil & Water Research     Open Access   (Followers: 11)
AKSIOMA Journal of Mathematics Education     Open Access   (Followers: 1)
Al-Jabar : Jurnal Pendidikan Matematika     Open Access   (Followers: 1)
Algebra and Logic     Hybrid Journal   (Followers: 5)
Algebra Colloquium     Hybrid Journal   (Followers: 4)
Algebra Universalis     Hybrid Journal   (Followers: 2)
Algorithmic Operations Research     Full-text available via subscription   (Followers: 5)
Algorithms     Open Access   (Followers: 11)
Algorithms Research     Open Access   (Followers: 1)
American Journal of Computational and Applied Mathematics     Open Access   (Followers: 5)
American Journal of Mathematical Analysis     Open Access  
American Journal of Mathematics     Full-text available via subscription   (Followers: 6)
American Journal of Operations Research     Open Access   (Followers: 5)
An International Journal of Optimization and Control: Theories & Applications     Open Access   (Followers: 8)
Analele Universitatii Ovidius Constanta - Seria Matematica     Open Access   (Followers: 1)
Analysis     Hybrid Journal   (Followers: 2)
Analysis and Applications     Hybrid Journal   (Followers: 1)
Analysis and Mathematical Physics     Hybrid Journal   (Followers: 5)
Analysis Mathematica     Full-text available via subscription  
Annales Mathematicae Silesianae     Open Access  
Annales mathématiques du Québec     Hybrid Journal   (Followers: 4)
Annales UMCS, Mathematica     Open Access   (Followers: 1)
Annales Universitatis Paedagogicae Cracoviensis. Studia Mathematica     Open Access  
Annali di Matematica Pura ed Applicata     Hybrid Journal   (Followers: 1)
Annals of Combinatorics     Hybrid Journal   (Followers: 4)
Annals of Data Science     Hybrid Journal   (Followers: 11)
Annals of Discrete Mathematics     Full-text available via subscription   (Followers: 6)
Annals of Mathematics     Full-text available via subscription   (Followers: 1)
Annals of Mathematics and Artificial Intelligence     Hybrid Journal   (Followers: 12)
Annals of Pure and Applied Logic     Open Access   (Followers: 2)
Annals of the Alexandru Ioan Cuza University - Mathematics     Open Access  
Annals of the Institute of Statistical Mathematics     Hybrid Journal   (Followers: 1)
Annals of West University of Timisoara - Mathematics     Open Access  
Annuaire du Collège de France     Open Access   (Followers: 5)
ANZIAM Journal     Open Access   (Followers: 1)
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applications of Mathematics     Hybrid Journal   (Followers: 2)
Applied Categorical Structures     Hybrid Journal   (Followers: 2)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 11)
Applied Mathematics     Open Access   (Followers: 3)
Applied Mathematics     Open Access   (Followers: 7)
Applied Mathematics & Optimization     Hybrid Journal   (Followers: 6)
Applied Mathematics - A Journal of Chinese Universities     Hybrid Journal  
Applied Mathematics Letters     Full-text available via subscription   (Followers: 2)
Applied Mathematics Research eXpress     Hybrid Journal   (Followers: 1)
Applied Network Science     Open Access   (Followers: 3)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 4)
Arab Journal of Mathematical Sciences     Open Access   (Followers: 3)
Arabian Journal of Mathematics     Open Access   (Followers: 2)
Archive for Mathematical Logic     Hybrid Journal   (Followers: 2)
Archive of Applied Mechanics     Hybrid Journal   (Followers: 5)
Archive of Numerical Software     Open Access  
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 5)
Arkiv för Matematik     Hybrid Journal   (Followers: 1)
Armenian Journal of Mathematics     Open Access  
Arnold Mathematical Journal     Hybrid Journal   (Followers: 1)
Artificial Satellites : The Journal of Space Research Centre of Polish Academy of Sciences     Open Access   (Followers: 20)
Asia-Pacific Journal of Operational Research     Hybrid Journal   (Followers: 3)
Asian Journal of Algebra     Open Access   (Followers: 1)
Asian Journal of Current Engineering & Maths     Open Access  
Asian-European Journal of Mathematics     Hybrid Journal   (Followers: 2)
Australian Mathematics Teacher, The     Full-text available via subscription   (Followers: 6)
Australian Primary Mathematics Classroom     Full-text available via subscription   (Followers: 4)
Australian Senior Mathematics Journal     Full-text available via subscription   (Followers: 1)
Automatic Documentation and Mathematical Linguistics     Hybrid Journal   (Followers: 5)
Axioms     Open Access   (Followers: 1)
Baltic International Yearbook of Cognition, Logic and Communication     Open Access   (Followers: 1)
Basin Research     Hybrid Journal   (Followers: 5)
BIBECHANA     Open Access   (Followers: 2)
BIT Numerical Mathematics     Hybrid Journal  
BoEM - Boletim online de Educação Matemática     Open Access  
Boletim Cearense de Educação e História da Matemática     Open Access  
Boletim de Educação Matemática     Open Access  
Boletín de la Sociedad Matemática Mexicana     Hybrid Journal  
Bollettino dell'Unione Matematica Italiana     Full-text available via subscription   (Followers: 1)
British Journal of Mathematical and Statistical Psychology     Full-text available via subscription   (Followers: 20)
Bruno Pini Mathematical Analysis Seminar     Open Access  
Buletinul Academiei de Stiinte a Republicii Moldova. Matematica     Open Access   (Followers: 12)
Bulletin des Sciences Mathamatiques     Full-text available via subscription   (Followers: 4)
Bulletin of Dnipropetrovsk University. Series : Communications in Mathematical Modeling and Differential Equations Theory     Open Access   (Followers: 1)
Bulletin of Mathematical Sciences     Open Access   (Followers: 1)
Bulletin of Symbolic Logic     Full-text available via subscription   (Followers: 2)
Bulletin of the Australian Mathematical Society     Full-text available via subscription   (Followers: 1)
Bulletin of the Brazilian Mathematical Society, New Series     Hybrid Journal  
Bulletin of the London Mathematical Society     Hybrid Journal   (Followers: 4)
Bulletin of the Malaysian Mathematical Sciences Society     Hybrid Journal  
Calculus of Variations and Partial Differential Equations     Hybrid Journal  
Canadian Journal of Science, Mathematics and Technology Education     Hybrid Journal   (Followers: 18)
Carpathian Mathematical Publications     Open Access   (Followers: 1)
Catalysis in Industry     Hybrid Journal   (Followers: 1)
CEAS Space Journal     Hybrid Journal   (Followers: 2)
CHANCE     Hybrid Journal   (Followers: 5)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
ChemSusChem     Hybrid Journal   (Followers: 7)
Chinese Annals of Mathematics, Series B     Hybrid Journal  
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
Chinese Journal of Mathematics     Open Access  
Clean Air Journal     Full-text available via subscription   (Followers: 1)
Cogent Mathematics     Open Access   (Followers: 2)
Cognitive Computation     Hybrid Journal   (Followers: 4)
Collectanea Mathematica     Hybrid Journal  
COMBINATORICA     Hybrid Journal  
Combinatorics, Probability and Computing     Hybrid Journal   (Followers: 4)
Combustion Theory and Modelling     Hybrid Journal   (Followers: 14)
Commentarii Mathematici Helvetici     Hybrid Journal   (Followers: 1)
Communications in Combinatorics and Optimization     Open Access  
Communications in Contemporary Mathematics     Hybrid Journal  
Communications in Mathematical Physics     Hybrid Journal   (Followers: 2)
Communications On Pure & Applied Mathematics     Hybrid Journal   (Followers: 3)
Complex Analysis and its Synergies     Open Access   (Followers: 2)
Complex Variables and Elliptic Equations: An International Journal     Hybrid Journal  
Complexus     Full-text available via subscription  
Composite Materials Series     Full-text available via subscription   (Followers: 8)
Compositio Mathematica     Full-text available via subscription   (Followers: 1)
Comptes Rendus Mathematique     Full-text available via subscription   (Followers: 1)
Computational and Applied Mathematics     Hybrid Journal   (Followers: 2)
Computational and Mathematical Methods in Medicine     Open Access   (Followers: 2)
Computational and Mathematical Organization Theory     Hybrid Journal   (Followers: 2)
Computational Complexity     Hybrid Journal   (Followers: 4)
Computational Mathematics and Modeling     Hybrid Journal   (Followers: 8)
Computational Mechanics     Hybrid Journal   (Followers: 5)
Computational Methods and Function Theory     Hybrid Journal  
Computational Optimization and Applications     Hybrid Journal   (Followers: 7)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 8)
Concrete Operators     Open Access   (Followers: 5)
Confluentes Mathematici     Hybrid Journal  
Contributions to Game Theory and Management     Open Access  
COSMOS     Hybrid Journal  
Cryptography and Communications     Hybrid Journal   (Followers: 13)
Cuadernos de Investigación y Formación en Educación Matemática     Open Access  
Cubo. A Mathematical Journal     Open Access  
Current Research in Biostatistics     Open Access   (Followers: 9)
Czechoslovak Mathematical Journal     Hybrid Journal   (Followers: 1)
Demographic Research     Open Access   (Followers: 11)
Demonstratio Mathematica     Open Access  
Dependence Modeling     Open Access  
Design Journal : An International Journal for All Aspects of Design     Hybrid Journal   (Followers: 29)
Developments in Clay Science     Full-text available via subscription   (Followers: 1)
Developments in Mineral Processing     Full-text available via subscription   (Followers: 3)
Dhaka University Journal of Science     Open Access  
Differential Equations and Dynamical Systems     Hybrid Journal   (Followers: 3)
Differentsial'nye Uravneniya     Open Access  
Discrete Mathematics     Hybrid Journal   (Followers: 8)
Discrete Mathematics & Theoretical Computer Science     Open Access  
Discrete Mathematics, Algorithms and Applications     Hybrid Journal   (Followers: 2)
Discussiones Mathematicae - General Algebra and Applications     Open Access  
Discussiones Mathematicae Graph Theory     Open Access   (Followers: 1)
Diskretnaya Matematika     Full-text available via subscription  
Dnipropetrovsk University Mathematics Bulletin     Open Access  
Doklady Akademii Nauk     Open Access  
Doklady Mathematics     Hybrid Journal  
Duke Mathematical Journal     Full-text available via subscription   (Followers: 1)
Eco Matemático     Open Access  
Edited Series on Advances in Nonlinear Science and Complexity     Full-text available via subscription  
Electronic Journal of Combinatorics     Open Access  
Electronic Journal of Differential Equations     Open Access  
Electronic Journal of Graph Theory and Applications     Open Access   (Followers: 2)
Electronic Notes in Discrete Mathematics     Full-text available via subscription   (Followers: 2)
Elemente der Mathematik     Full-text available via subscription   (Followers: 4)
Energy for Sustainable Development     Hybrid Journal   (Followers: 9)

        1 2 3 4 | Last

Journal Cover Catalysis in Industry
  Journal Prestige (SJR): 0.182
  Citation Impact (citeScore): 7
  Number of Followers: 1  
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 2070-0555 - ISSN (Online) 2070-0504
   Published by Springer-Verlag Homepage  [2350 journals]
  • Low-Temperature Conversion of ortho -Hydrogen into Liquid para -Hydrogen:
           Process and Catalysts. Review
    • Abstract: The present review is devoted to some problems of the production of liquid para-hydrogen by catalytic ortho-para conversion (OPC) of molecular hydrogen at cryogenic temperatures, the catalysts of this process, and catalyst operation in hydrogen liquefiers. The methods of evaluating the catalyst activity in OPC and calculations of the performance of hydrogen liquefiers are given. The most important papers that deal with the use of catalysts of OPC under the conditions of hydrogen liquefiers were considered. A procedure for processing the experimental data on catalyst activity was presented for calculations of the laboratory and industrial hydrogen liquefiers working at different temperature levels based on these data.
      PubDate: 2018-01-01
      DOI: 10.1134/S2070050418010117
       
  • Sodium Methoxide Catalyzed Depolymerization of Waste Polyethylene
           Terephthalate Under Microwave Irradiation
    • Abstract: Chemical recycling of polyethylene terephthalate (PET) to produce terephthalic acid (TPA) was studied using in situ hydrolysis with sodium methoxide in methanol and dimethyl sulfoxide (DMSO) as solvent under microwave irradiation. The microwave-assisted reaction was carried out at different temperatures, and reaction time between 5 to 30 min. High degrees of depolymerization were examined at temperature near 70°C at microwave power 300 W. The reaction was carried out in a sealed microwave reactor in which the time and temperature were controlled and recorded. The products were mainly monomers such as TPA and ethylene glycol (EG) which were isolated and purified for further analysis. Monomethyl terephthalate, dimethyl terephthalate, and terephthalic acid were formed initially then converted to TPA as a single monomer product. Purified, TPA was analyzed and identified by NMR, TGA, DSC and FTIR. It was observed that the reaction greatly depends on the amount of sodium methoxide, the volume of methanol and DMSO used, the reaction time, and temperature. Compared to conventional heating methods, the time needed to achieve complete degradation of PET was significantly reduced to 5 min by using microwave irradiation and sodium methoxide catalyst. This has led to substantial saving in energy and cost supporting the conclusion that this proposed recycling process is very beneficial for the recycling of PET wastes.
      PubDate: 2018-01-01
      DOI: 10.1134/S2070050418010087
       
  • Theoretical Optimization of the Shape and Size of Adsorbent Grains for
           Associated Petroleum Gas Drying
    • Abstract: The shape of adsorbent grains used for drying hydrocarbon gas flows at a reduced hydraulic resistance of their beds are theoretically optimized. A two-velocity model of gas flow in fixed beds consisting of differently shaped holed particles is used for calculations at typical parameters of the associated petroleum gas drying process. It is shown that the optimum shape of a grain is a four-spoke ring. At an equivalent diameter of 3 mm, such a grain is 6.154 × 6.154 mm in size, and its walls and baffles are 1.026 mm thick.
      PubDate: 2018-01-01
      DOI: 10.1134/S2070050418010129
       
  • Preferential CO Oxidation on Bimetallic Pt 0.5 M 0.5 Catalysts (M = Fe,
           Co, Ni) Prepared from Double Complex Salts
    • Abstract: Properties of Pt0.5M0.5 nanopowders (M = Fe, Co, Ni) of alloys obtained via the decomposition of double complex salts [Pt(NH3)5Cl][Fe(C2O4)3] ∙ 4H2O, [Pt(NH3)4][Co(C2O4)2(H2O)2] ∙ 2H2O, and [Pt(NH3)4][Ni(C2O4)2(H2O)2] ∙ 2H2O, respectively, are studied in the reaction of preferential CO oxidation. It is shown that bimetallic Pt0.5M0.5 catalysts (M = Fe, Co, Ni) are much more active in the low temperature range than Pt nanopowder. The activity of the catalysts decreases in the order Pt0.5M0.5 ≥ Pt0.5M0.5 > Pt0.5M0.5 @ Pt. The higher activity of bimetallic Pt0.5M0.5 catalysts in the reaction of preferential CO oxidation in the low-temperature range under conditions of dense Pt surface coverage by adsorbed CO molecules is most likely caused by the activation of CO on Pt atoms, the activation of O2 on atoms of the second metal (Fe, Co, Ni), and the reaction that occurs at the sites of contact between the atoms of platinum and the atoms of the second metal on the surfaces of the alloy’s nanoparticles. The bimetallic systems investigated in this work can be used to improve catalysts of practically important preferential CO oxidation reaction. These systems have considerable potential in the afterburning reactions of CO and hydrocarbons; hydrogenation reactions; electrochemical reactions; and many others. The means used in the preparation of bimetallic nanopowders based on the decomposition of double complex salts is simple, does not require the use of expensive or complex reagents, and can be easily adapted to produce supported catalysts containing Pt0.5M0.5 metal alloys (M = Fe, Co, Ni).
      PubDate: 2018-01-01
      DOI: 10.1134/S2070050418010099
       
  • Mathematical Simulating the Biokatalytic Transformation of Methyl Phenyl
           Sulfide into ( R )-Sulfoxide
    • Abstract: A mathematical model is proposed for describing the biotransformation of methyl phenyl sulfide to (R)-methyl phenyl sulfoxide by immobilized Gordonia terrae IEGM 136 cells. Kinetic patterns of the biotransformation of methyl phenyl sulfide are determined using experimental data on the initial concentration of sulfide and the amount of biocatalyst. The experimental data are compared to simulations of sulfide biotransformation scaling in a laboratory bioreactor. A mathematical model is developed for describing the biotransformation of methyl phenyl sulfide with repeated use of the biocatalyst. The resulting data can be used for optimizing the biotransformation of a wide range of organic aryl alkyl sulfides to optically active sulfoxides.
      PubDate: 2018-01-01
      DOI: 10.1134/S2070050418010051
       
  • Hydrogen Sulfide-Resistant Bifunctional Catalysts for the Steam Reforming
           of Methane: Activity and Structural Evolution
    • Abstract: Results are presented from studying an iron–nickel catalyst for the steam reforming of methane, synthesized by epitaxial coating on the surface of spherical pellets of commercial γ-Al2O3. It is shown the catalyst is resistant to the presence of hydrogen sulfide in a steam–gas mixture. The degree of conversion of methane during reforming is close to equilibrium at a pressure of 2.0 MPa, a temperature of 800°C, a ratio of Н2О: СН4 = 2: 1, a feedstock hourly space velocity (FHSV) of 6000 h−1, and a H2S concentration of 30 ppm. The structural evolution and phase state of the active components of the system are studied via X-ray diffraction analysis, transmission electron microscopy (TEM), and Mössbauer spectroscopy. The formation of paramagnetic iron oxide clusters tightly bound to the structure of the support, and of FeNi3 iron–nickel alloy particles on the surface of the catalyst, is responsible for the polyfunctional properties of the catalyst, which displays high activity in both the steam reforming of methane and the oxidative decomposition of hydrogen sulfide to elemental sulfur.
      PubDate: 2018-01-01
      DOI: 10.1134/S2070050418010063
       
  • Hydrocracking of Vacuum Gasoil on NiMoW/AAS-Al 2 O 3 Trimetallic
           Catalysts: Effect of the W : Mo Ratio
    • Abstract: The effect of the W: (W + Mo) atomic ratio in NiMoW trimetallic catalysts on their catalytic and physicochemical properties is studied. The catalysts are prepared by impregnating a carrier containing amorphous aluminosilicate (AAS) and aluminium oxide with an aqueous solution containing Ni, Mo, W compounds, and citric acid. They are studied via XRF, TEM, NH3 TPD, and low-temperature nitrogen adsorption and are tested in the hydrocracking of vacuum gasoil (VGO). The average length of a sulfide active component layer shrinks as the amount of Mo increases and the amount of W in the catalyst is reduced. XPS data indicate that the degree of sulfidation of tungsten in NiMoW trimetallic catalysts is lower than in NiW catalyst. Testing of the catalysts in hydrocracking of a straight-line VGO at 390–420°C, 16 MPa, a feedstock hourly space velocity (FHSV) of 0.71 h−1, and a H2: VGO ratio of 1200 L/L shows the activities of hydrodesulfurization, hydrodenitrogenation, hydrogenation, and hydrocracking grow along with the W: (W + Mo) ratio. When the process pressure is high and the amount of sulfur in the NiW feedstock is low, the catalysts have higher activity in the target reactions of VGO hydrocracking than NiMo catalyst.
      PubDate: 2018-01-01
      DOI: 10.1134/S2070050418010026
       
  • A New n -Alkane Hydroisomerization Catalyst Modified with Nanosized
           Molybdenum Carbides and Its Catalytic Properties in Diesel Fraction
           Hydroisomerization. Part III: Comparison of the Catalytic Properties of
           Bifunctional SAPO-31 and SAPO-11 Based Catalysts
    • Abstract: Part III of this work continues the study of the catalytic properties of new molybdenum carbide based hydroisomerization catalysts, which are resistant to sulfur compounds and allow the synthesis of waxy diesel fuels with the same quality characteristics as those of platinum-containing catalysts. The catalytic properties of such bifunctional catalysts as 7%Mo2C/SAPO-31 (LCCH-2) and 7%Mo2C/SAPO-11 (LCCH-2-2) in diesel fraction hydroisomerization in the temperature range of 320–400°C are compared. It is shown that LCCH-2 ensures a higher yield of the hydroisomerized diesel fraction with a lower freezing point as compared to LCCH-2-2 at temperatures above 320°C. The ratio between mono- and di-isomers in reaction products is analyzed. It is concluded that SAPO-31 based catalyst is more selective to the formation of terminal monosubstituted alkanes than SAPO-11 based catalyst. The resistance of both catalysts to deactivation with coke deposits (tests over 100 h at 320 and 360°C in hydroisomerization) is studied. It is established that LCCH-2-2 is less resistant to deactivation than LCCH-2. These findings are due to differences in acidity, the degree of uniformity in the distribution of acidic hydrogenating/dehydrogenating sites in the catalysts, and the structural type of their acidic supports.
      PubDate: 2018-01-01
      DOI: 10.1134/S207005041801004X
       
  • Using an Inducible Promoter of the Glucoamylase Gene to Construct New
           Multienzyme Complexes from Penicillium verruculosum
    • Abstract: New recombinant strains of Penicillium verruculosum are created using a new plasmid construct based on an inducible promoter of glucoamylase gene (gla1) that secretes heterologous xylanase E (XylE) from P. canescens. New biocatalysts are produced that contain cellulolytic enzyme preparations (EPs) enriched with XylE. The amount of XylE in the recombinant EPs varies in the optimum range of 11–24% of the total protein while generally preserving the P. verruculosum cellulose complex. The hydrolytic activity of the new EPs with respect to polymeric plant-derived substrates exceeds that of EPs produced using other expression systems and commercial preparations. The new EP glaX-17 surpasses in particular a control EP based on the recipient strain by 13% in the efficiency of hydrolyzing aspen wood and is 20% more efficient than the commercial EP Accelerase Duet. The new EP glaX-17 displays 25% greater efficiency (35–43%) during the hydrolysis of wheat bran than the commercial EP Accelease Duet. The effectiveness is demonstrated of using the new gla1 promoter for the production of EPs (biocatalysts) while preserving the balanced cellulose complex of the strain and optimum yield of heterologous XylE required for the deep hydrolysis of xylan-containing plant biomass.
      PubDate: 2018-01-01
      DOI: 10.1134/S2070050418010105
       
  • Biocatalytic Heterogeneous Processes of the Esterification of Saturated
           Fatty Acids with Aliphatic Alcohols
    • Abstract: Heterogeneous biocatalysts prepared by immobilizing a recombinant lipase from Thermomyces lanuginosus on mesoporous inorganic supports—silica (SiO2), alumina (Al2O3), and titania (TiO2)—are comparatively studied in the esterification of fatty acids with aliphatic alcohols. It is found that the T. lanuginosus lipase adsorbed on silica has the highest esterifying activity, while the lipase adsorbed on titania is completely inactivated. SiO2-based catalysts have high activity and stability in the esterification of saturated fatty acids containing 4–18 carbon atoms (C4–C18) with aliphatic alcohols (C5–C16) in organic solvents (hexane and diethyl ether). The catalysts operate in this reaction for several tens of reaction cycles (>40) without loss of activity. The recombinant rPichia/lip lipase immobilized on silica exhibits the most pronounced specificity for its first substrate, a fatty acid. For instance, the rate of synthesis for esters of low molecular weight acids (С4–С6) is three to four times slower than for the esters of acids with more than seven carbon atoms. The catalyst has a relatively broad specificity for the second substrate, an aliphatic alcohol. It is found that the ester of enanthic acid (C7:0) and butanol (C4) is synthesized at the maximum rate.
      PubDate: 2018-01-01
      DOI: 10.1134/S2070050418010075
       
  • Hydrocracking of Vacuum Gasoil on NiMo/AAS-Al 2 O 3 Catalysts Prepared
           from Citric Acid: Effect of the Catalyst Heat Treatment Temperature
    • Abstract: Ni-Mo bimetallic catalysts are prepared by impregnating a carrier containing amorphous aluminosilicate (AAS) and aluminum oxide using a solution with Ni, Mo, and citric acid. The temperature of the catalysts ranges from 120 to 550°С. The physicochemical properties of the catalysts are studied via XPS, TEM, and HCNS analysis, and they are tested in hydrocracking of vacuum gasoil. The particles of the sulfide active component (NiMoS phase) are localized predominantly on surfaces of aluminum oxide, and only some are on surfaces of AAS. When the temperature of catalyst calcination is raised, the average number of the layers in particles of the NiMoS phase grows as well, due to the removal of citric acid. This indicates strengthening of the interaction between the sulfide active component and aluminum oxide. The content of Ni-Mo massive sulfide particles also grows along with the temperature of calcination. The morphological characteristics of the sulfide active component affect the activity of the catalysts in hydrodesulfurization and hydrodenitrogenation, but not in hydrocracking. The optimum heat treatment temperature for NiMo/AAS-Al2O3 catalysts prepared with citric acid is 120°C. Recommendations are given for the heat treatment of catalysts under industrial conditions.
      PubDate: 2018-01-01
      DOI: 10.1134/S2070050418010038
       
  • Methane pyrolysis on deposited resistive MeO x /carborundum catalysts,
           where MeO x is MgO, CaO, MgO/Al 2 O 3 , MgO/ZrO 2 , CaO/Al 2 O 3 , and
           CaO/ZrO 2
    • Authors: S. S. Sigaeva; V. L. Temerev; N. V. Kuznetsova; P. G. Tsyrul’nikov
      Pages: 277 - 282
      Abstract: Thermostable oxide catalysts (Al2O3, ZrO2, MgO, and CaO) deposited onto a resistive support (carborundum) are investigated for oxygen-free methane pyrolysis. Adding MgO, ZrO2, and Al2O3 to pure carborundum considerably improves methane conversion and selectivity toward acetylene. In contrast, the deposition of СаO reduces the total activity of deposited catalysts. The maximum selectivity toward acetylene (23.6%) is achieved on MgO/SiC catalyst with methane conversion of 68% at T = 1290°C. Examination of the MgO/SiC sample shows that the catalyst retains its catalytic characteristics without decomposition (methane conversion, ≈69%; selectivity toward acetylene, ≈22%) for more than 4 h of operating in methane pyrolysis (15% СН4 in nitrogen) at a temperature of 1300°С as a result of there being no carbon corrosion of the carborundum resistive support, in comparison to the metal catalysts.
      PubDate: 2017-10-01
      DOI: 10.1134/s2070050417040080
      Issue No: Vol. 9, No. 4 (2017)
       
  • Hydrodeoxygenation of methyl-substituted ketones using the composite
           loading of hydrogenation and dehydration catalysts
    • Authors: D. P. Ivanov; A. S. Kharitonov; L. V. Pirutko; A. S. Noskov; P. A. Abrashenkov; V. A. Golovachev; D. O. Kondrashev; A. V. Kleimenov
      Pages: 299 - 307
      Abstract: The hydrogenation/hydrodeoxygenation of methyl-substituted carbonyl compounds to preserve the isomeric structure of a product is one way of controlling its amount of oxygen and improving the chemical stability of motor fuel components. The integration of hydrogenation and dehydration catalysts in one reaction space is an bright example of processes that proceed on these catalysts and positively affect each other. In comparison with the hydrogenation Ni-catalyst, the transformation of 2,4-dimethyl-3-pentanone into 2,4-dimethylpentane over the same catalyst loaded jointly with a zeolite is accompanied by a several-fold increase in hydrogenation rate and operational stability. In the process, the complete hydrodeoxygenation of the parent ketone is observed. Such composite loading can be used to replace bifunctional catalysts.
      PubDate: 2017-10-01
      DOI: 10.1134/s2070050417040043
      Issue No: Vol. 9, No. 4 (2017)
       
  • Hydrooligomerization of unsaturated hydrocarbons as a basis of new
           technologies for the production of motor fuel compounds
    • Authors: T. R. Karpova; E. A. Buluchevskii; A. V. Lavrenov
      Pages: 308 - 316
      Abstract: A brief analysis is performed for the current state of processes for the production of motor fuels based on the consecutive oligomerization and hydrogenation reactions of unsaturated hydrocarbons. Some new butene hydrooligomerization catalysts based on the bifunctional NiO/В2O3–Al2O3, PdO/В2O3–Al2O3, and MoO3/В2O3–Al2O3 systems are considered. It is shown that the best process performance parameters (a 67 wt % yield of liquid С5+ products at a butene conversion of more than 90%) are achieved with PdO/В2O3–Al2O3 catalyst prereduced in a hydrogen medium. The possibility of acetylene hydrooligomerization on NiO/B2O3–Al2O3 catalyst is demonstrated in principle. It is established that the presence of nickel(II) cations chemically bonded to the surface of a support is of fundamental importance for both acetylene hydrooligomerization and ethylene oligomerization.
      PubDate: 2017-10-01
      DOI: 10.1134/s2070050417040055
      Issue No: Vol. 9, No. 4 (2017)
       
  • Characteristics and catalytic activity of platinum reforming catalysts
           based on aluminum oxide modified by organic acids
    • Authors: V. Yu. Tregubenko; I. E. Udras; T. I. Gulyaeva; A. S. Belyi
      Pages: 317 - 322
      Abstract: The effect of treating aluminum oxide with organic acids (acetic acid, oxalic acid) on the dispersity, composition, and catalytic properties of the platinum sites of reforming catalysts is investigated. It is established that due to the high number of support defects, a Pt/О х -Al2O3 sample prepared on the basis of aluminum oxide treated with oxalic acid solution has the the highest activity. The role the acid modification of a support plays in the formation of charged atoms of platinum, resulting in an increase of catalytic activity, is established.
      PubDate: 2017-10-01
      DOI: 10.1134/s2070050417040110
      Issue No: Vol. 9, No. 4 (2017)
       
  • A new n -alkane hydroisomerization catalyst modified with nanosized
           molybdenum carbides and its catalytic properties in diesel fraction
           hydroisomerization. I. Synthesis and physicochemical properties of
           different acidic supports for hydroisomerization catalysts
    • Authors: G. V. Echevskii; A. V. Toktarev; D. G. Aksenov; E. G. Kodenev
      Pages: 323 - 330
      Abstract: Hydroisomerization catalysts based on nanosized molybdenum carbides are developed. Such catalysts are resistant to sulfur compounds and can be used for the synthesis of waxy diesel fuels with the same characteristics as on platinum-containing catalysts. In the first part of this work, acidic supports with different types of porous structure and concentrations and strengths of Brønsted acidic sites (e.g., silicoaluminophosphate SAPO-31, zeolite ZSM-12, modified zeolite Beta, and desiliconized zeolite ZSM-5) are synthesized for a new type of catalysts. Their physicochemical properties are studied by means of adsorption, temperature- programmed desorption of ammonia (TPD-NH3), nuclear magnetic resonance (NMR) spectroscopy, and scanning electron microscopy (SEM).
      PubDate: 2017-10-01
      DOI: 10.1134/s2070050417040031
      Issue No: Vol. 9, No. 4 (2017)
       
  • Bacterial degradation of ecotoxic dehydroabietic acid
    • Authors: K. M. Cheremnykh; V. V. Grishko; I. B. Ivshin
      Pages: 331 - 338
      Abstract: The possibility of biodegrading dehydroabietic acid (С20Н28О2, САS: 1740-19-8, abieta-8,11,13- trien-18-oic acid) (DAA), a toxic tricyclic diterpenoid, accumulated in the waste waters of the pulp and paper industry is studied using actinobacterial strain Dietzia maris IEGM 55Т. Cells of the strain Dietzia maris IEGM 55Т are shown to be resistant to DAA (MIC, 390 mg/L). The strain is not able to use DAA as its sole source of carbon and energy. DAA (500 mg/L) decays almost completely in 7 days when the bacteria are preliminarily grown with n-hexadecane. The DAA effect on the viability and respiratory activity of the bacteria is studied. Analysis of the antimicrobial activity shows that extracts of the obtained metabolites are not toxic, in contrast to the initial substrate. The resulting data expands our views on the catalytic activity of actinobacteria and their impact in decontaminating natural ecosystems that contain ecotoxicants.
      PubDate: 2017-10-01
      DOI: 10.1134/s207005041704002x
      Issue No: Vol. 9, No. 4 (2017)
       
  • Biocatalytic production of extracellular exopolysaccharide dextran
           synthesized by cells of Leuconostoc mesenteroides
    • Authors: N. A. Stepanov; O. V. Senko; E. N. Efremenko
      Pages: 339 - 343
      Abstract: Results are presented from studies and a comparative analysis of the production of the commercially important product dextran from sucrose using fed-batch cultivated cells of the Leuconostoc mesenteroides subsp. dextranicum B-5481 bacterium either immobilized in a polyvinyl alcohol (PVA) cryogel or in the form of a suspension. It is shown that under identical process conditions, the concentration of dextran is 1.2 times higher when using immobilized cells instead of free cells. The high productivity of dextran formation (4.2 g/(L h)) under the conditions of fed-batch cultivation of the immobilized cells and the ability of these cells to function without losing their metabolic activity for at least five operating cycles are demonstrated. The productivity of the developed biocatalyst is 5 times higher than that of Weissella confusa cells immobilized in a calcium alginate gel and 34 times higher than that of Leuconostoc mesenteroides KIBGE HA1 cells immobilized in a polyacrylamide gel. The molecular weight of the dextran samples produced by the immobilized L. mesenteroides B-5481 cells is half that of the polymer produced by the free cells, expanding the range of possible applications of the polysaccharide with no additional hydrolysis.
      PubDate: 2017-10-01
      DOI: 10.1134/s2070050417040109
      Issue No: Vol. 9, No. 4 (2017)
       
  • Highly concentrated populations of Aureobasidium pullulans cells in
           biocatalytic pullulan production processes
    • Authors: O. V. Senko; E. N. Efremenko
      Pages: 344 - 348
      Abstract: Results are presented from studies and a comparative analysis of highly concentrated populations of free and immobilized Aureobasidium pullulans Y-4137 cells in the biocatalytic processes of pullulan production in glucose-containing media. The possibility of effectively using the developed biocatalyst in the form of immobilized cells is demonstrated. The process characteristics are determined for pullulan production from hydrolysates of various sources of renewable feedstocks (Jerusalem artichoke tubers, aspen wood, Chlorella vulgaris microalgal biomass, and potato pulp) under the action of the catalyst. It is established that A. pullulans cells immobilized in a polyvinyl alcohol (PVA) cryogel consume glucose 1.5 times faster and accumulate a 1.7 times higher concentration of the target polysaccharide in the medium than free cells. The immobilized cells can function for at least 15 operating cycles with a slight (no more than 10%) reduction in their metabolic activity. Analysis of the obtained data confirms that cell immobilization in a PVA gel for the production of pullulan allows us to shorten the duration of operating cycles in similar processes by a factor of 1.4 while reaching a comparable yield of the target product.
      PubDate: 2017-10-01
      DOI: 10.1134/s2070050417040079
      Issue No: Vol. 9, No. 4 (2017)
       
  • Preparation and properties of new biocatalysts for the degradation of
           nonstarch plant polysaccharides
    • Authors: A. P. Sinitsyn; E. A. Rubtsova; I. A. Shashkov; A. M. Rozhkova; O. A. Sinitsyna; E. G. Kondrat’eva; I. N. Zorov; D. A. Merzlov; D. O. Osipov; V. Yu. Matys
      Pages: 349 - 356
      Abstract: Recombinant strains of Penicillium verruculosum are developed that produce the homologous endoglucanase 2 (Eg2) and the P. canescens heterologous xylanase E (XylE). The recombinant strains are used to obtain new biocatalysts, i.e., enzyme preparations (EPs) that are substantially enriched with Eg2 and XylE. These preparations are highly active with respect to nonstarch plant polysaccharides (NPSes): cellulose, β-glucan, and xylan. The qualitative and quantitative compositions of the new EPs are studied by protein chromatography. It was shown that the EPs contained (in terms of total protein content) ~16–17% Eg2, 48–63% XylE, and 17–30% cellobiohydrolases, while the EP obtained using the recipient strain contained 1.4% Eg2, ~60% cellobiohydrolase and no XylE. The optimum pH values for cellulase (with respect to carboxymethylcellulose, CMC) and the xylanase activity of the EPs are 4.0 and 5.5, respectively. The EPs exhibit the abovementioned activities within a wide range of pH (3 to 7). The EPs exhibit CMC-ase and xylanase activities in the temperature range of 20–80°С with maxima at 60 and 70°C, respectively. The xylanase activity of the new EPs is virtually uninhibited by protein inhibitors of rye.
      PubDate: 2017-10-01
      DOI: 10.1134/s2070050417040092
      Issue No: Vol. 9, No. 4 (2017)
       
 
 
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