scholarly journals H3PMo12O40 Immobilized on Amine Functionalized SBA-15 as a Catalyst for Aldose Epimerization

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 507
Author(s):  
Hui Wang ◽  
Meiyin Wang ◽  
Jining Shang ◽  
Yuanhang Ren ◽  
Bin Yue ◽  
...  
Keyword(s):  
Activation Energy ◽  
Aqueous Solution ◽  
Heterogeneous Catalysts ◽  
Phosphomolybdic Acid ◽  
Catalytic Performance ◽  
Catalytic Activities ◽  
Amine Functionalized

In this work various amount of phosphomolybdic acid (PMo) were immobilized on amine functionalized SBA-15 and used as heterogeneous catalysts in the epimerization of glucose in aqueous solution. 13.3PMo/NH2-SBA-15 exhibited the best catalytic performance with a glucose conversion of 34.8% and mannose selectivity of 85.6% within two hours at 120 °C. The activation energy of 80.1 ± 0.1 kJ·mol−1 was lower than that of 96 kJ·mol−1 over the homogeneous H3PMo12O40 catalyst. The catalytic activities of 13.3PMo/NH2-SBA-15 for the transformation of some other aldoses including mannose, arabinose and xylose were also investigated.

scholarly journals Ambient base-free glycerol oxidation over bimetallic PdFe/SiO2 by in situ generated active oxygen species

2021 ◽  
Author(s):  
Ricci Underhill ◽  
Mark Douthwaite ◽  
Richard J. Lewis ◽  
Peter J. Miedziak ◽  
Robert D. Armstrong ◽  
...  
Keyword(s):  
Heterogeneous Catalysts ◽  
Bimetallic Catalyst ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Active Oxygen Species ◽  
Catalytic Performance ◽  
Resonance Spectroscopy ◽  
Oxygen Species ◽  
Paramagnetic Resonance ◽  
Temperature Oxidation

AbstractLow temperature oxidation of alcohols over heterogeneous catalysts is exceptionally challenging, particularly under neutral conditions. Herein, we report on an efficient, base-free method to oxidise glycerol over a 0.5%Pd-0.5%Fe/SiO2 catalyst at ambient temperature in the presence of gaseous H2 and O2. The exceptional catalytic performance was attributed to the in situ formation of highly reactive surface-bound oxygenated species, which promote the dehydrogenation on the alcohol. The PdFe bimetallic catalyst was determined to be significantly more active than corresponding monometallic analogues, highlighting the important role both metals have in this oxidative transformation. Fe leaching was confirmed to occur over the course of the reaction but sequestering experiments, involving the addition of bare carbon to the reactions, confirmed that the reaction was predominantly heterogeneous in nature. Investigations with electron paramagnetic resonance spectroscopy suggested that the reactivity in the early stages was mediated by surface-bound reactive oxygen species; no homogeneous radical species were observed in solution. This theory was further evidenced by a direct H2O2 synthesis study, which confirmed that the presence of Fe in the bimetallic catalyst neither improved the synthesis of H2O2 nor promoted its decomposition over the PdFe/SiO2 catalyst.

scholarly journals Exploiting the Potential of Biosilica from Rice Husk as Porous Support for Catalytically Active Iron Oxide Nanoparticles

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1259
Author(s):  
Ana Franco ◽  
Rafael Luque ◽  
Carolina Carrillo-Carrión
Keyword(s):  
Iron Oxide ◽  
Iron Oxide Nanoparticles ◽  
Rice Husk ◽  
Heterogeneous Catalysts ◽  
Catalytic Performance ◽  
Added Value ◽  
Oxide Nanoparticles ◽  
Porous Support ◽  
Green Materials ◽  
Catalytically Active

Biomass-derived materials are put forward as eco-friendly alternatives to design heterogeneous catalysts. To contribute in this field, we explored the potential of mesoporous biogenic silica (RH-Silica) obtained from lignocellulosic waste, in particular from rice husk, as an inorganic support to prepare heterogenized iron oxide-based catalysts. Mechanochemistry, considered as a green and sustainable technique, was employed to synthetize iron oxide nanoparticles in pure hematite phase onto the biosilica (α-Fe2O3/RH-Silica), making this material a good candidate to perform catalyzed organic reactions. The obtained material was characterized by different techniques, and its catalytic activity was tested in the selective oxidation of styrene under microwave irradiation. α-Fe2O3/RH-Silica displayed a good catalytic performance, achieving a conversion of 45% under optimized conditions, and more importantly, with a total selectivity to benzaldehyde. Furthermore, a good reusability was achieved without decreasing its activity after multiple catalytic cycles. This work represents a good example of using sustainable approaches and green materials as alternatives to conventional methods in the production of high-added value products.

scholarly journals Removal of Chromium from Aqueous Solution Using Modified Pomegranate Peel:Mechanistic and Thermodynamic Studies

2009 ◽  
Vol 6 (s1) ◽  
pp. S153-S158 ◽  
Author(s):  
Tariq S. Najim ◽  
Suhad A. Yassin
Keyword(s):  
Activation Energy ◽  
Solid Solution ◽  
Aqueous Solution ◽  
Adsorption Process ◽  
Batch Process ◽  
The Other ◽  
Water Molecules ◽  
Pomegranate Peel ◽  
Solution Interface ◽  
Adsorbent Surface

Modified pomegranate peel (MPGP) and formaldehyde modified pomegranate peel (FMPGP) were prepared and used as adsorbent for removal of Cr(VI) ions from aqueous solution using batch process. The temperature variation study of adsorption on both adsorbents revealed that the adsorption process is endothermic, from the positive values of ∆H˚. These values lie in the range of physisorption. The negative values of ∆G˚ show the adsorption is favorable and spontaneous. On the other hand, these negative values increases with increase in temperature on both adsorbents, which indicate that the adsorption is preferable at higher temperatures. ∆S˚ values showed that the process is accompanied by increase in disorder and randomness at the solid solution interface due to the reorientation of water molecules and Cr(VI) ions around the adsorbent surface. The endothermic nature of the adsorption was also confirmed from the positive values of activation energy, Ea, the low values of Ea confirm the physisorption mechanism of adsorption. The sticking probability, S*, of Cr(VI) ion on surface of both adsorbents showed that the adsorption is preferable due to low values of S*(0< S*< 1 ), but S*values are lower for FMPGP indicating that the adsorption on FMPGP is more preferable .

THE OXIDATION OF NITRITE AND IODATE IONS BY HYPOCHLORITE IONS

1961 ◽  
Vol 39 (8) ◽  
pp. 1645-1651 ◽  
Author(s):  
M. W. Lister ◽  
P. Rosenblum
Keyword(s):  
Activation Energy ◽  
Aqueous Solution ◽  
Rate Constant ◽  
Hypochlorous Acid ◽  
Slow Stage ◽  
Iodate Ions

The oxidation of nitrite ions and of iodate ions by hypochlorite ions in aqueous solution has been examined. The oxidation of nitrite is really a reaction of hypochlorous acid, with the slow stage HOCl + NO2− + H2O → H3O+ + Cl− + NO3−. The rate constant is given by log k = 7.36−6450/RT (time in minutes, and the activation energy in calories). The oxidation of iodate is chiefly a reaction of hypochlorite ions, probably ClO− + IO3− → Cl− + IO4−, although the rate is somewhat increased by a higher concentration of hydroxide ions. The rate constant is given by log k = 16.15−26,100/RT. These results are compared with other oxidations by hypochlorite ions, to see if any general trends are apparent.

scholarly journals Chemocatalytic Production of Lactates from Biomass-Derived Sugars

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
Heng Zhang ◽  
Yulin Hu ◽  
Liying Qi ◽  
Jian He ◽  
Hu Li ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Heterogeneous Catalysts ◽  
Catalytic Performance ◽  
Green Solvents ◽  
Separation And Purification ◽  
Sustainable Resources ◽  
Base Catalysts ◽  
Heterogeneous Catalytic ◽  
Acid And Base ◽  
Relative Separation

In recent decades, a great deal of attention has been paid to the exploration of alternative and sustainable resources to produce biofuels and valuable chemicals, with aims of reducing the reliance on depleting confined fossil resources and alleviating serious economic and environmental issues. In line with this, lignocellulosic biomass-derived lactic acid (LA, 2-hydroxypropanoic acid), to be identified as an important biomass-derived commodity chemical, has found wide applications in food, pharmaceuticals, and cosmetics. In spite of the current fermentation of saccharides to produce lactic acid, sustainability issues such as environmental impact and high cost derived from the relative separation and purification process will be growing with the increasing demands of necessary orders. Alternatively, chemocatalytic approaches to manufacture LA from biomass (i.e., inedible cellulose) have attracted extensive attention, which may give rise to higher productivity and lower costs related to product work-up. This work presents a review of the state-of-the-art for the production of LA using homogeneous, heterogeneous acid, and base catalysts, from sugars and real biomass like rice straw, respectively. Furthermore, the corresponding bio-based esters lactate which could serve as green solvents, produced from biomass with chemocatalysis, is also discussed. Advantages of heterogeneous catalytic reaction systems are emphasized. Guidance is suggested to improve the catalytic performance of heterogeneous catalysts for the production of LA.

scholarly journals Things go better with coke: the beneficial role of carbonaceous deposits in heterogeneous catalysis

2016 ◽  
Vol 6 (2) ◽  
pp. 363-378 ◽  
Author(s):  
C. H. Collett ◽  
J. McGregor
Keyword(s):  
Heterogeneous Catalysis ◽  
Heterogeneous Catalysts ◽  
Catalyst Deactivation ◽  
Catalytic Performance ◽  
Fischer Tropsch ◽  
Carbonaceous Deposits ◽  
Beneficial Role ◽  
Catalytic Processes

Carbonaceous deposits on heterogeneous catalysts are traditionally associated with catalyst deactivation. However, they can play a beneficial role in many catalytic processes, e.g. dehydrogenation, hydrogenation, alkylation, isomerisation, Fischer–Tropsch, MTO etc. This review highlights the role and mechanism by which coke deposits can enhance catalytic performance.

Shell thickness controlled core–shell Fe3O4@CoO nanocrystals as efficient bifunctional catalysts for the oxygen reduction and evolution reactions

2019 ◽  
Vol 55 (4) ◽  
pp. 525-528 ◽  
Author(s):  
Lingshan Zhou ◽  
Binglu Deng ◽  
Zhongqing Jiang ◽  
Zhong-Jie Jiang
Keyword(s):  
Oxygen Reduction ◽  
Shell Thickness ◽  
Great Influence ◽  
Catalytic Performance ◽  
Core Shell ◽  
Bifunctional Catalysts ◽  
Catalytic Activities

Core–shell Fe3O4@CoO NCs have been demonstrated to be efficient catalysts for ORR and OER. The specific core/shell interaction can be ascribed to the main reason leading to their high catalytic performance. The shell thickness has a great influence on the catalytic activities.

Aqueous-phase synthesis of layered double hydroxide nanoplates as catalysts for the oxygen evolution reaction

2018 ◽  
Vol 47 (48) ◽  
pp. 17342-17348 ◽  
Author(s):  
Euiyoung Jung ◽  
Jae Kyeom Kim ◽  
Hyungsuk Choi ◽  
Min Hyung Lee ◽  
Taekyung Yu
Keyword(s):  
Aqueous Solution ◽  
Transition Metal ◽  
Oxygen Evolution ◽  
Layered Double Hydroxide ◽  
Aqueous Phase ◽  
Oxygen Evolution Reaction ◽  
Metal Salt ◽  
Catalytic Performance ◽  
Phase Synthesis ◽  
Double Hydroxide

Transition metal LDH nanoplates were synthesized by heating an aqueous solution containing a metal salt, PEG, and octylamine. The LDH nanoplates showed comparable electrochemical catalytic performance for the oxygen evolution reaction.

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