Vapor-Phase Hydrodeoxygenation of Guaiacol to Aromatics over Pt/HBeta: Identification of the Role of Acid Sites and Metal Sites on the Reaction Pathway

ChemCatChem ◽  
2018 ◽  
Vol 10 (5) ◽  
pp. 1064-1074 ◽  
Author(s):  
Lei Nie ◽  
Bo Peng ◽  
Xinli Zhu
Keyword(s):  
Vapor Phase ◽  
Reaction Pathway ◽  
Acid Sites

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...

scholarly journals On the Role of Protonic Acid Sites in Cu Loaded FAU31 Zeolite as a Catalyst for the Catalytic Transformation of Furfural to Furan

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 2015
Author(s):  
Łukasz Kuterasiński ◽  
Małgorzata Smoliło-Utrata ◽  
Joanna Kaim ◽  
Wojciech Rojek ◽  
Jerzy Podobiński ◽  
...  
Keyword(s):  
Active Sites ◽  
Acid Sites ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Brønsted Acid Sites ◽  
Protonic Acid ◽  
Brönsted Acid ◽  
Brönsted Acid Sites ◽  
Bronsted Acid Sites

The aim of the present paper is to study the speciation and the role of different active site types (copper species and Brønsted acid sites) in the direct synthesis of furan from furfural catalyzed by copper-exchanged FAU31 zeolite. Four series of samples were prepared by using different conditions of post-synthesis treatment, which exhibit none, one or two types of active sites. The catalysts were characterized by XRD, low-temperature sorption of nitrogen, SEM, H2-TPR, NMR and by means of IR spectroscopy with ammonia and CO sorption as probe molecules to assess the types of active sites. All catalyst underwent catalytic tests. The performed experiments allowed to propose the relation between the kind of active centers (Cu or Brønsted acid sites) and the type of detected products (2-metylfuran and furan) obtained in the studied reaction. It was found that the production of 2-methylfuran (in trace amounts) is determined by the presence of the redox-type centers, while the protonic acid sites are mainly responsible for the furan production and catalytic activity in the whole temperature range. All studied catalysts revealed very high susceptibility to coking due to polymerization of furfural.

scholarly journals Oxidation of Ethanol in Cu-Faujasites Studied by IR Spectroscopy

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2669
Author(s):  
Łukasz Kuterasiński ◽  
Jerzy Podobiński ◽  
Jerzy Datka
Keyword(s):  
Ethanol Oxidation ◽  
Produced Water ◽  
Acid Sites ◽  
No Adsorption ◽  
Ir Studies ◽  
Oxygen Donor ◽  
Before And After ◽  
Acetate Formation ◽  
Back Donation

In this study, IR studies of the coadsorption of ethanol and CO on Cu+ cations evidenced the transfer of electrons from ethanol to Cu+, which caused the lowering of the frequency of the band attributed to CO bonded to the same Cu+ cation due to the more effective π back donation of d electrons of Cu to antibonding π* orbitals of CO. The reaction of ethanol with acid sites in zeolite HFAU above 370 K produced water and ethane, polymerizing to polyethylene. Ethanol adsorbed on zeolite Cu(2)HFAU containing acid sites and Cu+exch also produced ethene, but in this case, the ethene was bonded to Cu+ and did not polymerize. C=C stretching, which is IR non-active in the free ethene molecule, became IR active, and a weak IR band at 1538 cm−1 was present. The reaction of ethanol above 370 K in Cu(5)NaFAU zeolite (containing small amounts of Cu+exch and bigger amounts of Cu+ox, Cu2+exch and CuO) produced acetaldehyde, which was further oxidized to the acetate species (CH3COO-). As oxygen was not supplied, the donors of oxygen were the Cu species present in our zeolite. The CO and NO adsorption experiments performed in Cu-zeolite before and after ethanol reaction evidenced that both Cu+ox and Cu2+ (Cu2+exch and CuO) were consumed by the ethanol oxidation reaction. The studies of the considered reaction of bulk CuO and Cu2O as well as zeolites, in which the contribution of Cu+ox species was reduced by various treatments, suggest that ethanol was oxidized to acetaldehyde by Cu2+ox (the role of Cu+ox could not be elucidated), but Cu+ox was the oxygen donor in the acetate formation.

Role of Acid Sites on γ-Al2O3 Based Catalyst for CF4 Hydrolysis

2011 ◽  
Vol 37 (2) ◽  
pp. 175-180
Author(s):  
Takashi Sasaki ◽  
Shuichi Kanno
Keyword(s):  
Acid Sites

γ-Alumina and Amorphous Silica–Alumina: Structural Features, Acid Sites and the Role of Adsorbed Water

2017 ◽  
Vol 60 (19-20) ◽  
pp. 1554-1564 ◽  
Author(s):  
Vicente Sanchez Escribano ◽  
Gabriella Garbarino ◽  
Elisabetta Finocchio ◽  
Guido Busca
Keyword(s):  
Amorphous Silica ◽  
Adsorbed Water ◽  
Structural Features ◽  
Acid Sites ◽  
Silica Alumina

scholarly journals The role of HLA typing in rheumatic diseases

2020 ◽  
Vol 3 (1) ◽  
pp. 1-8
Author(s):  
Luca Mascaretti ◽  
Elena Bevilacqua
Keyword(s):  
Rheumatoid Arthritis ◽  
Juvenile Idiopathic Arthritis ◽  
Amino Acid ◽  
Ankylosing Spondylitis ◽  
Hla Class I ◽  
Acid Sites ◽  
Hla Typing ◽  
Erosive Disease ◽  
Complex Cases

Association between HLA-DR4 and rheumatoid arthritis (RA) has been known for 4 decades, and amino acid sites within HLA-DRB1 (11/13, 71, 74) are highly associated with RA. HLA is not useful for diagnosis or prognosis, but it may help predict severe and erosive disease. Since 90% of patients with ankylosing spondylitis (AS) and 50-70% of other spondyloarthritis (SpA) patients are HLA-B*27 positive, HLA is a stronghold of diagnostic algorithms. Genetic predisposition to juvenile idiopathic arthritis (JIA) is mainly due to HLA class II, and to a lesser extent to HLA class I. Although HLA plays a role in rheumatic disorders, its clinical relevance is not homogeneous. When classical biomarkers are lacking or in complex cases, HLA typing may provide support for the management of patients.

scholarly journals Thermodynamics of primary antioxidant action of flavonols in polar solvents

2019 ◽  
Vol 12 (1) ◽  
pp. 108-118 ◽  
Author(s):  
Martin Michalík ◽  
Ján Rimarčík ◽  
Vladimír Lukeš ◽  
Erik Klein
Keyword(s):  
Reaction Pathway ◽  
Hydrogen Atom Transfer ◽  
Antioxidant Effect ◽  
Antioxidant Action ◽  
Polar Solvents ◽  
Polar Media ◽  
Primary Antioxidant ◽  
Intramolecular Hydrogen

Abstract Very recently, a report on the antioxidant activity of flavonoids has appeared, where authors concluded that Hydrogen Atom Transfer mechanism represents the thermodynamically preferred mechanism in polar media (https://doi.org/10.1016/j.foodres.2018.11.018). Unfortunately, serious errors in the theoretical part of the paper led to incorrect conclusions. For six flavonols (galangin, kaempferol, quercetin, morin, myricetin, and fisetin), reaction enthalpies related to three mechanisms of the primary antioxidant action were computed. Based on the obtained results, the role of intramolecular hydrogen bonds (IHB) in the thermodynamics of the antioxidant effect is presented. Calculations and the role of solvation enthalpies of proton and electron in the determination of thermodynamically preferred mechanism is also briefly explained and discussed. The obtained results are in accordance with published works considering the Sequential Proton-Loss Electron-Transfer thermodynamically preferred reaction pathway.

Sign in / Sign up

Export Citation Format

Share Document