Preparation of SBA-15 supported Pt/Pd bimetallic catalysts using supercritical fluid reactive deposition: how do solvent effects during material synthesis affect catalytic properties?

2017 ◽  
Vol 19 (4) ◽  
pp. 977-986 ◽  
Author(s):  
Y. Qiao ◽  
N. Said ◽  
M. Rauser ◽  
K. Yan ◽  
F. Qin ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Fluid ◽  
Solvent Effects ◽  
Bimetallic Catalysts ◽  
Levulinic Acid ◽  
Catalytic Properties ◽  
Reaction Medium ◽  
Material Synthesis ◽  
Catalyst Synthesis ◽  
Reactive Deposition

Supercritical carbon dioxide is the preferred reaction medium for catalyst synthesis as exemplified for the hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL).

scholarly journals Spherical Silica Modified with Magnesium and Ruthenium—Synthesis, Characterization and Catalytic Properties

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7378
Author(s):  
Kalina Grzelak ◽  
Maciej Trejda
Keyword(s):  
Bimetallic Catalysts ◽  
Levulinic Acid ◽  
Catalytic Properties ◽  
Porous Silica ◽  
N2 Adsorption ◽  
Catalytic Activities ◽  
Spherical Silica ◽  
Cascade Processes ◽  
Adsorption Desorption ◽  
Positive Effect

The design of different bimetallic catalysts is an important area of catalytic research in the context of their possible applications in the cascade processes, meeting the requirements of the so-called green chemistry. In this study, such catalysts were obtained by the incorporation of magnesium species into spherical silica, which was in the next step covered with porous silica and modified with ruthenium species. The structure and chemical composition of the materials obtained were determined by XRD measurements, low temperature N2 adsorption/desorption, SEM, ICP-OES and XPS methods. The catalytic activities of materials obtained were tested in 2-propanol decomposition and hydrogenation of levulinic acid. The results obtained confirmed the successful coverage of nanospheres with porous silica. A much higher concentration of ruthenium species was found on the surface of the catalysts than in their bulk. The opposite relationship was observed for magnesium species. The modification of nanospheres with silica had a positive effect on the catalytic activity of the materials obtained. For the most active sample, i.e., Ru/NS/3Mg/NS, 49% of levulinic acid conversion in its hydrogenation process was reported with γ-valerolactone as the only product.

On the Calculation of Transition State Activity Coefficient and Solvent Effects on Chemical Reactions

1998 ◽  
Vol 63 (12) ◽  
pp. 1969-1976 ◽  
Author(s):  
Alvaro Domínguez ◽  
Rafael Jimenez ◽  
Pilar López-Cornejo ◽  
Pilar Pérez ◽  
Francisco Sánchez
Keyword(s):  
Activity Coefficient ◽  
Transition State ◽  
Chemical Reactions ◽  
Solvent Effects ◽  
Transition State Theory ◽  
Reaction Medium ◽  
State Theory ◽  
Precursor Complex ◽  
State Activity ◽  
Classical Transition

Solvent effects, when the classical transition state theory (TST) holds, can be interpreted following the Brønsted equation. However, when calculating the activity coefficient of the transition state, γ# it is important to take into account that this coefficient is different from that of the precursor complex, γPC. The activity coefficient of the latter is, in fact, that calculated in classical treatments of salt and solvent effects. In this paper it is shown how the quotients γ#/γPC change when the reaction medium changes. Therefore, the conclusions taken on the basis of classical treatments may be erroneous.

scholarly journals Supercritical Fluid Extraction of Pyrrolidine Alkaloid from Leaves of Piper amalago L.

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
V. S. Carrara ◽  
L. C. Filho ◽  
V. A. S. Garcia ◽  
V. S. Faiões ◽  
E. F. Cunha-Júnior ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Fluid Extraction ◽  
Supercritical Fluid ◽  
Orthogonal Array ◽  
Design Matrix ◽  
Supercritical Carbon Dioxide Extraction ◽  
Orthogonal Array Design ◽  
Fluid Extraction ◽  
Array Design ◽  
Carbon Dioxide Extraction

Supercritical fluid extraction was used to extract the alkaloid N-[7-(3′,4′-methylenedioxyphenyl)-2(Z),4(Z)-heptadienoyl]pyrrolidine from leaves of Piper amalago L. A three-level orthogonal array design matrix, OAD OA9(34), was used for optimization of the parameters of supercritical extraction of the alkaloid, employing supercritical carbon dioxide: extraction time (20, 40, and 60 min), temperature (40, 50, and 60°C), pressure (150, 200, and 250 bar), and the use of cosolvents (ethanol, methanol, and propyleneglycol). All parameters had significant effect on the alkaloid yield. The alkaloid yield after 60 min of extraction without cosolvents at 9 different conditions (32) in terms of temperature (40, 50, and 60°C) and pressure (150, 200, and 250 bar) was also evaluated. The optimal yield (≈3.8 mg g−1) was obtained with supercritical CO2 + methanol (5% v : v) at 40°C and 200 bar for 60 min of extraction.

Carbon dioxide supercritical fluid extracts from yarrow and rose hip herbal dust as valuable source of aromatic and lipophilic compounds

2021 ◽  
Vol 22 ◽  
pp. 100494
Author(s):  
Senka Vidović ◽  
Ana Vasić ◽  
Jelena Vladić ◽  
Stela Jokić ◽  
Krunoslav Aladić ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Fluid ◽  
Lipophilic Compounds ◽  
Valuable Source ◽  
Rose Hip
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