Thermal Stability of Pt Nanoparticles Supported on WOx/Al2O3 for n-Heptane Hydroconversion

2010 ◽  
Vol 1279 ◽  
Author(s):  
J. L. Contreras ◽  
G.A. Fuentes ◽  
J. Salmones ◽  
B. Zeifert
Keyword(s):  
Thermal Stability ◽  
Bimetallic Catalysts ◽  
Pt Nanoparticles ◽  
Thermal Stabilization ◽  
Reaction Rates ◽  
Atomic Ratio ◽  
Impregnation Method ◽  
Reduction Temperature ◽  
Sequential Samples ◽  
Thermal Stability Of

AbstractThe thermal stabilization of γ-Al2O3 using W+6 ions has been found useful to the synthesis of Pt/Al2O3 catalysts. The sequential impregnation method was used to study the effect of W6+ upon Pt/ γ-Al2O3 reducibility, Pt dispersion, Raman spectroscopy and n-heptane hydroconversion. The W/Pt atomic ratios varied from 3.28 to 75. We found that the W6+ ions delayed reduction of a fraction of Pt+4 atoms beyond 773 K. At the same time, W6+inhibited sintering of the metallic crystallites once they were formed on the surface. For the sample with a W/Pt atomic ratio of 3.28, W6+ did not inhibit the H2 reduction of Pt oxides even below of 773 K, the Pt oxides were reduced completely, however, the Pt dispersion decreased for this sample with respect to the Pt/γ-Al2O3 catalyst. After reduction at 1073 K, sequential samples impregnating Pt on WOx/γAl2O3 were more active and stable during n-heptane hydroconversion than monometallic Pt/γAl2O3 catalyst. Selectivities for dehydrocyclization, isomerization and Hydrocracking changed significantly when the W/Pt atomic ratio and reduction temperature increased. Initial and final reaction rates were more sensitive to reduction temperature. W6+ ions promoted high thermal stability of Pt crystallites when sequential catalysts were reduced at 1073 K and deactivation of bimetallic catalysts reduced at 773 K and 1073 K was less than the deactivation of Pt/Al2O3 catalyst.

Calcium phosphate apatites with variable Ca/P atomic ratio I. Synthesis, characterisation and thermal stability of powders

Biomaterials ◽  
2002 ◽  
Vol 23 (4) ◽  
pp. 1065-1072 ◽  
Author(s):  
S. Raynaud ◽  
E. Champion ◽  
D. Bernache-Assollant ◽  
P. Thomas
Keyword(s):  
Thermal Stability ◽  
Calcium Phosphate ◽  
Atomic Ratio ◽  
Thermal Stability Of

The role of glycosylation and domain interactions in the thermal stability of human angiotensin-converting enzyme

2008 ◽  
Vol 389 (9) ◽  
Author(s):  
Hester G. O'Neill ◽  
Pierre Redelinghuys ◽  
Sylva L.U. Schwager ◽  
Edward D. Sturrock
Keyword(s):  
Thermal Stability ◽  
Angiotensin Converting Enzyme ◽  
Physicochemical Properties ◽  
Mammalian Cells ◽  
Insect Cells ◽  
Thermal Stabilization ◽  
Site Directed Mutagenesis ◽  
Converting Enzyme ◽  
Complex Glycans ◽  
Thermal Stability Of

Abstract The N and C domains of somatic angiotensin-converting enzyme (sACE) differ in terms of their substrate specificity, inhibitor profiling, chloride dependency and thermal stability. The C domain is thermally less stable than sACE or the N domain. Since both domains are heavily glycosylated, the effect of glycosylation on their thermal stability was investigated by assessing their catalytic and physicochemical properties. Testis ACE (tACE) expressed in mammalian cells, mammalian cells in the presence of a glucosidase inhibitor and insect cells yielded proteins with altered catalytic and physicochemical properties, indicating that the more complex glycans confer greater thermal stabilization. Furthermore, a decrease in tACE and N-domain N-glycans using site-directed mutagenesis decreased their thermal stability, suggesting that certain N-glycans have an important effect on the protein's thermodynamic properties. Evaluation of the thermal stability of sACE domain swopover and domain duplication mutants, together with sACE expressed in insect cells, showed that the C domain contained in sACE is less dependent on glycosylation for thermal stabilization than a single C domain, indicating that stabilizing interactions between the two domains contribute to the thermal stability of sACE and are decreased in a C-domain-duplicating mutant.

Grain Growth Behaviour Of Nanocrystalline Nickel

1991 ◽  
Vol 238 ◽  
Author(s):  
A. M. El-Sherik ◽  
K. Boylan ◽  
U. Erb ◽  
G. Palumbo ◽  
K. T. Aust
Keyword(s):  
Electron Microscopy ◽  
Thermal Stability ◽  
Grain Size ◽  
Grain Boundary ◽  
Grain Growth ◽  
Thermal Stabilization ◽  
Growth Behaviour ◽  
In Situ Electron Microscopy ◽  
Thermal Stability Of

ABSTRACTThe thermal stability of electrodeposited nanocrystalline Ni-1.2%P and Ni-0.12%S alloys is evaluated by in-situ electron microscopy studies. Isothermal grain size versus annealing time curves at 573K and 623K show an unexpected thermal stabilization in form of a transition from rapid initial grain growth to negligible grain growth. This behaviour is discussed in terms of the various grain boundary drag mechanisms which may be operative in these alloys.

scholarly journals In situ study of the thermal stability of supported Pt nanoparticles and their stabilization via atomic layer deposition overcoating

Nanoscale ◽  
2020 ◽  
Vol 12 (21) ◽  
pp. 11684-11693
Author(s):  
Eduardo Solano ◽  
Jolien Dendooven ◽  
Ji-Yu Feng ◽  
Philipp Brüner ◽  
Matthias M. Minjauw ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Atomic Layer Deposition ◽  
Pt Nanoparticles ◽  
Atomic Layer ◽  
Pt Nanoparticle ◽  
In Situ Study ◽  
Layer Deposition ◽  
Nanoparticle Stabilization ◽  
Thermal Stability Of

Supported Pt nanoparticle stabilization via Atomic Layer Deposition overcoating with Al2O3 has been proved to prevent particle coarsening during thermal annealing for widely spaced nanoparticles while ensuring surface accessibility for applications.

Thermal Stability of DNA Interacting with Furazolidone and Cu(II) Ions

1983 ◽  
Vol 38 (3-4) ◽  
pp. 290-293 ◽  
Keyword(s):  
Thermal Stability ◽  
Transition Temperature ◽  
Thermal Stabilization ◽  
Dna Complex ◽  
Thermal Stability Of

Furazolidone, on complexing with DNA, led to its thermal stabilization. The increase in transition temperature of DNA (ΔTm) increased linearly with % A - T content. Increasing concentration of Cu(II) ions progressively lowered the transition tem perature of DNA, but Cu(II) ions were not equally effective in lowering the transition temperature of furazolidone-DNA complex. When equimolar amounts of Cu(II) ions and furazolidone were used, the stabilisation effects of furazolidone prevailed over the destabilisation effect of Cu(II) ions

scholarly journals Enhanced Adsorption of Carbon Dioxide from Simulated Biogas on PEI/MEA-Functionalized Silica

2020 ◽  
Vol 17 (4) ◽  
pp. 1452
Author(s):  
Yankun Sun ◽  
Wanzhen Liu ◽  
Xinzhong Wang ◽  
Haiyan Yang ◽  
Jun Liu
Keyword(s):  
Thermal Stability ◽  
Adsorption Capacity ◽  
Co2 Adsorption ◽  
Weight Ratio ◽  
Diffusion Resistance ◽  
Impregnation Method ◽  
Adsorption Activity ◽  
Adsorption Performance ◽  
Co2 Adsorption Capacity ◽  
Thermal Stability Of

A series of efficient adsorbents were prepared by a wet-impregnation method for CO2 separation from simulated biogas. A type of commercially available silica, named as FNG-II silica (FS), was selected as supports. FS was modified with a mixture of polyethyleneimine (PEI) and ethanolamine (MEA) to improve the initial CO2 adsorption capacity and thermal stability of the adsorbents. The influence of different adsorbents on CO2 adsorption performance was investigated by breakthrough experiments. Scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), and N2 adsorption–desorption isotherm were used to characterize the silica before and after impregnating amine. Additionally, the thermal stability of adsorbents was measured by differential thermal analysis (TDA). Silica impregnated with mixtures of MEA and PEI showed increased CO2 adsorption performance and high thermal stability compared with those obtained from silica impregnated solely with MEA or PEI. With a simulated biogas flow rate of 100 mL/min at 0.2 MPa and 25 °C, FS-10%MEA-10%PEI exhibited a CO2 adsorption capacity of ca. 64.68 mg/g which increased by 81 % in comparison to FS-20%PEI. The thermal stability of FS-10%MEA-10%PEI was evidently higher than that of FS-20%MEA, and a further improvement of thermal stability was achieved with the increasing value of PEI/MEA weight ratio. It was showed that MEA was able to impose a synergistic effect on the dispersion of PEI in the support, reduce the CO2 diffusion resistance and thus increase CO2 adsorption performance. Additionally, if the total percentage of amine was the same, FS impregnated by different ratios of PEI to MEA did not exhibit an obvious difference in CO2 adsorption performance. FS-15%PEI-5%MEA could be regenerated under mild conditions without obvious loss of CO2 adsorption activity.

scholarly journals Protein thermal stabilization in aqueous solutions of osmolytes.

2015 ◽  
Vol 63 (1) ◽  
Author(s):  
Piotr Bruździak ◽  
Aneta Panuszko ◽  
Muriel Jourdan ◽  
Janusz Stangret
Keyword(s):  
Thermal Stability ◽  
Aqueous Solutions ◽  
Theoretical Calculations ◽  
Thermal Stabilization ◽  
Protein Stabilization ◽  
Hen Egg White Lysozyme ◽  
Egg White Lysozyme ◽  
Hen Egg White ◽  
Thermal Stability Of ◽  
Distinctive Role

Proteins' thermal stabilization is a significant problem in various biomedical, biotechnological, and technological applications. We investigated thermal stability of hen egg white lysozyme in aqueous solutions of the following stabilizing osmolytes: Glycine (GLY), N-methylglycine (NMG), N,N-dimethylglycine (DMG), N,N,N-trimethylglycine (TMG), and trimethyl-N-oxide (TMAO). Results of CD-UV spectroscopic investigation were compared with FTIR hydration studies' results. Selected osmolytes increased lysozyme's thermal stability in the following order: Gly>NMG>TMAO≈DMG>TMG. Theoretical calculations (DFT) showed clearly that osmolytes' amino group protons and water molecules interacting with them played a distinctive role in protein thermal stabilization. The results brought us a step closer to the exact mechanism of protein stabilization by osmolytes.

Comparative Study Based on Activation Procedure Using Air and Nitrogen Gas to Synthesis Nanoparticles Cu/Al2O3 Catalyst

2015 ◽  
Vol 1107 ◽  
pp. 96-100
Author(s):  
Arvyvie Abie Jamil ◽  
I. Rubia ◽  
Jahimin A. Asik ◽  
Brian Brandon Bernard ◽  
Bryan Gindana ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Crystal Size ◽  
Active Phase ◽  
Impregnation Method ◽  
Nitrogen Flow ◽  
Cu Nanoparticles ◽  
Catalyst Activation ◽  
Activation Procedure ◽  
Cu Catalyst ◽  
Thermal Stability Of

Cu nanoparticles on Al2O3 catalyst were prepared via impregnation method and two different activation conditions were examined. The morphology of the catalyst has been characterized by using scanning electron microscopy (SEM); while, the crystallography was determined by using powder X-ray diffraction (XRD). The thermal stability of the catalyst was analysed by using thermogravimetry and differential thermal analysis (TG-DTA). Overall, from the XRD pattern, it was revealed that the nanoparticles Cu catalyst produced in air and nitrogen conditions is CuO and Cu active phase. At 400°C under air condition, the crystal size of CuO produced are in between 23.57 and 23.61 nm, while in nitrogen condition the crystal size was 30.24 to 30.31 nm. These results indicate that the size of the Cu nanoparticles catalyst produced under nitrogen flow was slightly bigger compared to air conditions. The results were further confirmed using SEM image in which catalyst activation under nitrogen flow has produced abundance microcrystal structure than under air condition. Meanwhile, the thermal stability of the nano-Cu catalyst shows that the both activation procedure was a single stage of thermal degradation at 260°C.

Sign in / Sign up

Export Citation Format

Share Document