scholarly journals Role of transition metals on MoS2-based supported catalysts for hydrodeoxygenation (HDO) of propylguaiacol

2021 ◽  
Vol 5 (7) ◽  
pp. 2097-2113
Author(s):  
You Wayne Cheah ◽  
Muhammad Abdus Salam ◽  
Prakhar Arora ◽  
Olov Öhrman ◽  
Derek Creaser ◽  
...  
Keyword(s):  
Kinetic Model ◽  
Transition Metals ◽  
Supported Catalysts ◽  
Reaction Pathway

Role of transition metals (Ni, Cu, Fe, and Zn) on MoS2 supported alumina was studied for the HDO of propylguaiacol (PG) to produce aromatics, cycloalkanes, and phenolics. A kinetic model was proposed elucidating the reaction pathway for HDO of PG.

scholarly journals Modification of Gold Zeolitic Supports for Catalytic Oxidation of Glucose to Gluconic Acid

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5250
Author(s):  
Adrian Walkowiak ◽  
Joanna Wolska ◽  
Anna Wojtaszek-Gurdak ◽  
Izabela Sobczak ◽  
Lukasz Wolski ◽  
...  
Keyword(s):  
Catalytic Oxidation ◽  
Gluconic Acid ◽  
Supported Catalysts ◽  
Reaction Pathway ◽  
Three Dimensional ◽  
Au Nps ◽  
Zeolite Lattice ◽  
Zeolite Supports ◽  
Oxidation Of Glucose

Activity of gold supported catalysts strongly depends on the type and composition of support, which determine the size of Au nanoparticles (Au NPs), gold-support interaction influencing gold properties, interaction with the reactants and, in this way, the reaction pathway. The aim of this study was to use two types of zeolites: the three dimensional HBeta and the layered two-dimensional MCM-36 as supports for gold, and modification of their properties towards the achievement of different properties in oxidation of glucose to gluconic acid with molecular oxygen and hydrogen peroxide. Such an approach allowed establishment of relationships between the activity of gold catalysts and different parameters such as Au NPs size, electronic properties of gold, structure and acidity of the supports. The zeolites were modified with (3-aminopropyl)-trimethoxysilane (APMS), which affected the support features and Au NPs properties. Moreover, the modification of the zeolite lattice with boron was applied to change the strength of the zeolite acidity. All modifications resulted in changes in glucose conversion, while maintaining high selectivity to gluconic acid. The most important findings include the differences in the reaction steps limiting the reaction rate depending on the nature of the oxidant applied (oxygen vs. H2O2), the important role of porosity of the zeolite supports, and accumulation of negative charge on Au NPs in catalytic oxidation of glucose.

Kinetic Aspects of the Interplay of Cancer and the Immune System

2019 ◽  
Vol 14 (02) ◽  
pp. 101-114 ◽  
Author(s):  
Vladimir P. Zhdanov
Keyword(s):  
Stem Cells ◽  
Immune System ◽  
Kinetic Model ◽  
Human Population ◽  
Lifetime Risk ◽  
Risk Of Cancer

The understanding of the interplay between cancer and the immune system is still limited. Herein, I focus on two aspects of this interplay. First, I propose a kinetic model describing the likely role of the immune system in the lifetime risk of cancer at the level of the whole human population. For each tissue, the risk is predicted to be influenced by the heterogeneity of the population and to depend exponentially on time. The expression for the risk does not, however, depend explicitly on the total number of divisions of the corresponding stem cells. For this reason, the correlation with the latter number can only be indirect. Second, using another kinetic framework, I describe how the growth of a few tumors can depend on their interaction via the immune system. The analysis shows that depending on specific details, the tumors of different sizes tend either to reach the same size or remain to be of different sizes.

Ethanol conversion over Ga2O3-ZrO2 solid solution: empirical evidences of the reaction pathway, the surface acid–base property, and role of isolated gallium ion

2021 ◽  
Author(s):  
Takashi Yamamoto ◽  
Akihito Kurimoto ◽  
Riona Sato ◽  
Shoki Katada ◽  
Hirotaka Mine ◽  
...  
Keyword(s):  
Solid Solution ◽  
Reaction Pathway ◽  
Ethanol Conversion ◽  
Acid Base ◽  
Base Property ◽  
Temperature Range ◽  
Acid Base Property

Ethanol conversion by Ga2O3-ZrO2 solid solution was examined in the temperature range 573–773 K, and acetone/isobutene formation was confirmed under cofeeding of H2O vapor. The reaction pathway was empirically investigated...

Disclosing the role of Gold on Palladium ‐ Gold alloyed supported catalysts in formic acid decomposition

ChemCatChem ◽  
2021 ◽  
Author(s):  
Alberto Villa ◽  
Ilaria Barlocco ◽  
Sofia Capelli ◽  
Xiuyuan Lu ◽  
Silvio Bellomi ◽  
...  
Keyword(s):  
Formic Acid ◽  
Supported Catalysts ◽  
Acid Decomposition ◽  
Formic Acid Decomposition

scholarly journals A Phenomenological Study on the Synergistic Role of Precious Metals and the Support in the Steam Reforming of Logistic Fuels on Monometal Supported Catalysts

2010 ◽  
Vol 2010 ◽  
pp. 1-15 ◽  
Author(s):  
Abdul-Majeed Azad ◽  
Desikan Sundararajan
Keyword(s):  
Steam Reforming ◽  
High Efficiency ◽  
Phenomenological Study ◽  
Supported Catalysts ◽  
Precious Metals ◽  
Sulfur Poisoning ◽  
Jet Fuels ◽  
Hydrogen Yield ◽  
High Hydrogen

Clean power source utilizing vast logistic fuel reserves (jet fuels, diesel, and coal) would be the main driver in the 21st century for high efficiency. Fuel processors are required to convert these fuels into hydrogen-rich reformate for extended periods in the presence of sulfur, and deliver hydrogen with little or no sulfur to the fuel cell stack. However, the jet and other logistic fuels are invariably sulfur-laden. Sulfur poisons and deactivates the reforming catalyst and therefore, to facilitate continuous uninterrupted operation of logistic fuel processors, robust sulfur-tolerant catalysts ought to be developed. New noble metal-supported ceria-based sulfur-tolerant nanocatalysts were developed and thoroughly characterized. In this paper, the performance of single metal-supported catalysts in the steam-reforming of kerosene, with 260 ppm sulfur is highlighted. It was found that ruthenium-based formulation provided an excellent balance between hydrogen production and stability towards sulfur, while palladium-based catalyst exhibited rapid and steady deactivation due to the highest propensity to sulfur poisoning. The rhodium supported system was found to be most attractive in terms of high hydrogen yield and long-term stability. A mechanistic correlation between the role of the nature of the precious metal and the support for generating clean desulfurized -rich reformate is discussed.

Ion chemistry of transition metals in hydrocarbon flames. II. Cations of Sc, Ti, V, Cr, and Mn

1988 ◽  
Vol 66 (9) ◽  
pp. 2219-2228 ◽  
Author(s):  
John M. Goodings ◽  
Quang Tran ◽  
Nicholas S. Karellas
Keyword(s):  
Transition Metals ◽  
Metal Atom ◽  
Chemical Ionization ◽  
Metallic Ions ◽  
Ion Chemistry ◽  
Hydrocarbon Flames ◽  
Basic Series ◽  
First Time ◽  
Isomeric Structures

The same fuel-rich, premixed, conical, methane–oxygen flame at 2200 K and atmospheric pressure used for studies of Fe, Co, Ni, Cu, and Zn in Part I (1) is doped with the same concentration (~1 ppm) of Sc, Ti, V, Cr, and Mn to complete the first row of ten transition metals. Metallic ions of these metals and their compounds formed by chemical ionization reactions with H3O+ are observed by sampling the flame through a nozzle into a quadrupole mass spectrometer. Concentration profiles of individual and total cations are measured as a function of distance along the flame axis, and also mass spectra at a fixed point in the burnt gas. If A is the metal atom, the observed ions can be represented by four hydrate series including (a) A+•nH2O, (b) AOH+•nH2O, (c) AO+•nH2O, and (d) AO2H+•nH2O with n = 0–3 or 4, giving a maximum of four ligands around the metal atom. However, alternative isomeric structures are possible for each of the four basic series (e.g. AO+•2H2O ~ A(OH)2+•H2O ~ A(OH)3H+). The ions observed with Cr and Mn, in common with those of Fe, Co, Ni, and Cu, strongly favour series (a). On the other hand, Sc is completely different; the ions of series (c) are dominant. All four series are observed with each of Ti and V. Series (b) dominates for Ti and series (c) for V; ions from series (d) were observed for the first time. The ion chemistry of these metals is discussed in detail with emphasis on the probable chemical ionization reactions responsible for metallic ion formation. The pre-eminent role of proton transfer processes is apparent.

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