Stabilization of Pt in SiO2–Al2O3 Microspheres at High Mechanical Resistance, Promoted with W Oxides for the Combustion of CO

This study shows the development of a combustion promoter for the oil-refining process called fluid catalytic cracking (FCC). The investigation of a catalyst prepared for the combustion of CO composed of 0.05 wt% Pt supported on SiO2–Al2O3–0.5 wt% W microspheres with high mechanical resistance, promoted with tungsten oxides (WOx) that can inhibit the sintering of Pt, is reported. The addition of WOx in SiO2–Al2O3 inhibited the decrease in the specific area when calcined from 550 °C to 950 °C. SiO2–Al2O3 support in the form of calcined microspheres with average diameters between 70–105 µm were produced by spray drying, using two atomization discs with vanes of different geometry: a straight rectangular blade disc (DAR) and a curved rectangular vanes disc (DAC). The DAR disk produced whole microspheres, while the DAC had hollow and broken microspheres. The microspheres were characterized by XRD, SEM, optical microscopy, N2 physisorption (BET area) and fracture resistance tests. The Pt catalysts were evaluated by TPR, H2 chemisorption and CO combustion. The catalyst of 0.05 wt% Pt/SiO2–Al2O3–0.5 wt% turned out to be the most stable. A thermal stabilization effect was observed at contents lower than 1 wt% W that allowed it to inhibit the sintering of the Pt catalyst.

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Influence of the Reduction Temperature and the Nature of the Support on the Performance of Zirconia and Alumina-Supported Pt Catalysts for n-Dodecane Hydroisomerization

Catalysts ◽

10.3390/catal11010088 ◽

2021 ◽

Vol 11 (1) ◽

pp. 88

Author(s):

Diana García-Pérez ◽

Maria Consuelo Alvarez-Galvan ◽

Jose M. Campos-Martin ◽

Jose L. G. Fierro

Keyword(s):

Catalytic Activity ◽

Surface Area ◽

Catalytic Properties ◽

Catalytic Performance ◽

Major Influence ◽

Pt Catalysts ◽

Reduction Temperature ◽

Metal Dispersion ◽

Tungsten Oxides ◽

Supported Pt Catalysts

Catalysts based on zirconia- and alumina-supported tungsten oxides (15 wt % W) with a small loading of platinum (0.3 wt % Pt) were selected to study the influence of the reduction temperature and the nature of the support on the hydroisomerization of n-dodecane. The reduction temperature has a major influence on metal dispersion, which impacts the catalytic activity. In addition, alumina and zirconia supports show different catalytic properties (mainly acid site strength and surface area), which play an important role in the conversion. The NH3-TPD profiles indicate that the acidity in alumina-based catalysts is clearly higher than that in their zirconia counterparts; this acidity can be attributed to a stronger interaction of the WOx species with alumina. The PtW/Al catalyst was found to exhibit the best catalytic performance for the hydroisomerization of n-dodecane based on its higher acidity, which was ascribed to its larger surface area relative to that of its zirconia counterparts. The selectivity for different hydrocarbons (C7–10, C11 and i-C12) was very similar for all the catalysts studied, with branched C12 hydrocarbons being the main products obtained (~80%). The temperature of 350 °C was clearly the best reduction temperature for all the catalysts studied in a trickled-bed-mode reactor.

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Stabilization of a G-Quadruplex from Unfolding by Replication Protein A Using Potassium and the Porphyrin TMPyP4

Journal of Nucleic Acids ◽

10.4061/2011/529828 ◽

2011 ◽

Vol 2011 ◽

pp. 1-13 ◽

Cited By ~ 5

Author(s):

Aishwarya Prakash ◽

Fabien Kieken ◽

Luis A. Marky ◽

Gloria E. O. Borgstahl

Keyword(s):

Dna Replication ◽

Protein A ◽

Thermal Stabilization ◽

Replication Protein A ◽

Replication Protein ◽

Unique Problem ◽

Ssdna Binding ◽

Binding Domains ◽

G Quadruplex ◽

Stabilization Effect

Replication protein A (RPA) plays an essential role in DNA replication by binding and unfolding non-canonical single-stranded DNA (ssDNA) structures. Of the six RPA ssDNA binding domains (labeled A-F), RPA-CDE selectively binds a G-quadruplex forming sequence (5′-TAGGGGAAGGGTTGGAGTGGGTT-3′called Gq23). In K+, Gq23 forms a mixed parallel/antiparallel conformation, and in Na+Gq23 has a less stable (TMlowered by ∼20∘C), antiparallel conformation. Gq23 is intramolecular and 1D NMR confirms a stable G-quadruplex structure in K+. Full-length RPA and RPA-CDE-core can bind and unfold the Na+form of Gq23 very efficiently, but complete unfolding is not observed with the K+form. Studies with G-quadruplex ligands, indicate that TMPyP4 has a thermal stabilization effect on Gq23 in K+, and inhibits complete unfolding by RPA and RPA-CDE-core. Overall these data indicate that G-quadruplexes present a unique problem for RPA to unfold and ligands, such as TMPyP4, could possibly hinder DNA replication by blocking unfolding by RPA.

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Nanomechanics combined with HDX reveal allosteric drug binding sites of CFTR NBD1

10.1101/2021.08.20.457065 ◽

2021 ◽

Author(s):

Rita Padanyi ◽

Bianka Farkas ◽

Hedvig Tordai ◽

Balint Kiss ◽

Helmut Grubmuller ◽

...

Keyword(s):

Binding Sites ◽

Thermal Stabilization ◽

Drug Efficacy ◽

Md Simulations ◽

Drug Binding ◽

Structural Defects ◽

Mechanical Resistance ◽

Atomic Force ◽

Δf508 Cftr ◽

Hydrogen Deuterium

Cystic fibrosis is most frequently caused by the deletion of F508 (ΔF508) in CFTR's nucleotide binding domain 1 (NBD1), thereby compromising CFTR folding, stability and domain assembly. Limitation to develop a successful therapy has been attributed to the lack of molecules that synergistically facilitate folding by targeting distinct structural defects of ΔF508-CFTR. To improve drug efficacy by targeting the ΔF508-NBD1 folding and stability, and to study potential ΔF508-NBD1 allosteric corrector binding sites at the atomic level, we combined molecular dynamics (MD) simulations, atomic force spectroscopy (AFM) and hydrogen-deuterium exchange (HDX) experiments to elucidate the mechanical and thermal stabilization mechanisms of ΔF508-NBD1 by 5-bromoindole-3-acetic acid (BIA). MD and AFM allowed us to describe unfolding intermediates and forces acting during NBD1 mechanical unfolding. Application of the low-potency corrector BIA increased the mechanical resistance of the ΔF508-NBD1 α-subdomain, which was confirmed as a binding site by computational modeling and HDX experiments. Our results underline the complementarity of MD and AFM despite their different pulling speeds and provide a possible strategy to improve folding correctors.

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Thermal stabilization effect of some 3,5-di-t-butyl-4-hydroxy derivatives of ethane and ethene

Polymer Testing ◽

10.1016/s0142-9418(01)00096-4 ◽

2002 ◽

Vol 21 (3) ◽

pp. 353-361 ◽

Cited By ~ 2

Author(s):

S. Jipa ◽

T. Zaharescu ◽

R. Setnescu ◽

T. Setnescu ◽

J. Herdan ◽

...

Keyword(s):

Thermal Stabilization ◽

Stabilization Effect ◽

Derivatives Of

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The Thermal Stabilization Effect of Biphenol Monoacrylate on Polyoxymethylene

Journal of Thermoplastic Composite Materials ◽

10.1177/0892705709345943 ◽

2009 ◽

Vol 23 (4) ◽

pp. 543-559 ◽

Cited By ~ 3

Author(s):

Lu Gan ◽

Lin Ye

Keyword(s):

Thermal Stabilization ◽

Stabilization Effect

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The TiO2 topotactic transformation assisted trapping of an atomically dispersed Pt catalyst for low temperature CO oxidation

RSC Advances ◽

10.1039/c9ra02739d ◽

2019 ◽

Vol 9 (29) ◽

pp. 16774-16778

Author(s):

Yunping He ◽

Xue-Zhi Song ◽

Feng Ding ◽

Xiaolan Kang ◽

Feifei Sun ◽

...

Keyword(s):

Low Temperature ◽

Co Oxidation ◽

Rough Surface ◽

Pt Catalyst ◽

Pt Catalysts ◽

Low Temperature Co Oxidation ◽

Topotactic Transformation

Atomically dispersed Pt catalysts are deposited on the rough surface of TiO2, which is synthesized via topotactic transformation from a NH4TiOF3 mesocrystal.

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A Single Turnover (STO) Characterization of Supported Palladium Catalysts

MRS Proceedings ◽

10.1557/proc-111-453 ◽

1987 ◽

Vol 111 ◽

Author(s):

Robert L. Augustine ◽

David R. Baum

Keyword(s):

Palladium Catalysts ◽

Active Sites ◽

Pt Catalyst ◽

Catalyst Characterization ◽

Pt Catalysts ◽

Ambient Conditions ◽

Reaction Conditions ◽

Pd Catalysts ◽

Supported Pt Catalysts

AbstractWhile the STO catalyst characterization procedure has been applied to a variety of supported Pt catalysts, application of this technique to the characterization of supported Pd catalysts showed that there were several significant differences between the Pt and the Pd catalysts. Under STO reaction conditions each surface site on a Pt catalyst reacts only once so there is a 1:1 relationship between the product composition and the densities of the various types of active sites present. With Pd catalysts under these same conditions, alkene isomerization takes place so readily that the amount of isomerized product formed depends on the contact time of the reactant pulse with the catalyst so there is no direct relationship between the amount of isomerization and the number of isomerization sites present. On Pt there are some direct saturation sites present on which H2 is rather weakly held. Such sites are not present on Pd catalysts. The reactive surface of supported Pt catalysts remains constant on long exposure to air. With Pd catalysts exposure to air results in a decrease in saturation site densities which can be reversed by re-reduction of the surface with H2 under ambient conditions but not completely under what can be termed “reaction conditions” where the extent of surface re-reduction decreases with catalyst age.

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