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Catalysts ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 39
Author(s):  
Hassan H. Hammud ◽  
Hassan Traboulsi ◽  
Ranjith Kumar Karnati ◽  
Syed Ghazanfar Hussain ◽  
Esam M. Bakir

Cobalt hierarchical graphitic carbon nanoparticles (Co@HGC) (1), (2), and (3) were prepared by simple pyrolysis of a cobalt phenanthroline complex in the presence of anthracene at different temperatures and heating times, under a nitrogen atmosphere. The samples were used for the catalytic hydrogenation of 2,4-dinitrophenol. Samples (1) and (3) were prepared by heating at 600 °C and 800 °C respectively, while (2) was prepared by heating at 600 °C with an additional intermediate stage at 300 °C. This work revealed that graphitization was catalyzed by cobalt nanoparticles and occurred readily at temperatures of 600 °C and above. The nanocatalysts were characterized by Scanning Electron Microscopy SEM, energy dispersive X-ray analysis EDX, Raman, Xrd, and XPS. The analysis revealed the presence of cobalt and cobalt oxide species as well as graphitized carbon, while TEM analysis indicated that the nanocatalyst contains mainly cobalt nanoparticles of 3–20 nm in size embedded in a lighter graphitic web. Some bamboo-like multiwall carbon nanotubes and graphitic onion-like nanostructures were observed in (3). The structures and chemical properties of the three catalysts were correlated with their catalytic activities. The apparent rate constants kapp (min−1) of the 2,4-dinitrophenol reductions were 0.34 for (2), 0.17 for (3), 0.04 for (1), 0.005 (no catalyst). Among the three studied catalysts, the highest rate constant was obtained for (2), while the highest conversion yield was achieved by (3). Our data show that an increase in agglomeration of the cobalt species reduces the catalytic activity, while an increase in pyrolysis temperature improves the conversion yield. The nanocatalyst enhances hydrogen generation in the presence of sodium borohydride and reduces 2,4-dinitrophenol to p-diamino phenol. The best nanocatalyst (3) was prepared at 800 °C. It consisted of uniformly distributed cobalt nanoparticles sheltered by hierarchical graphitic carbon. The nanocatalyst is easily separated and recycled from the reaction system and proved to be degradation resistant, to have robust stability, and high activity towards the reduction reaction of nitrophenols.


Reactions ◽  
2021 ◽  
Vol 2 (4) ◽  
pp. 499-513
Author(s):  
Eleni-Stavroula Vastaroucha ◽  
Sofia Maina ◽  
Savvoula Michou ◽  
Ourania Kalantzi ◽  
Chrysanthi Pateraki ◽  
...  

The utilization of crude glycerol, generated as a by-product from the biodiesel production process, for the production of high value-added products represents an opportunity to overcome the negative impact of low glycerol prices in the biodiesel industry. In this study, the biochemical behavior of Yarrowia lipolytica strains FMCC Y-74 and FMCC Y-75 was investigated using glycerol as a carbon source. Initially, the effect of pH value (3.0–7.0) was examined to produce polyols, intracellular lipids, and polysaccharides. At low pH values (initial pH 3.0–5.0), significant mannitol production was recorded. The highest mannitol production (19.64 g L−1) was obtained by Y. lipolytica FMCC Y-74 at pH = 3.0. At pH values ranging between 5.0 and 6.0, intracellular polysaccharides synthesis was favored, while polyols production was suppressed. Subsequently, the effect of crude glycerol and its concentration on polyols production was studied. Y. lipolytica FMCC Y-74 showed high tolerance to impurities of crude glycerol. Initial substrate concentrations influence polyols production and distribution with a metabolic shift toward erythritol production being observed when the initial glycerol concentration (Gly0) increased. The highest total polyols production (=56.64 g L−1) was obtained at Gly0 adjusted to ≈120 g L−1. The highest polyols conversion yield (0.59 g g−1) and productivity (4.36 g L−1 d−1) were reached at Gly0 = 80 g L−1. In fed-batch intermittent fermentation with glycerol concentration remaining ≤60 g L−1, the metabolism was shifted toward mannitol biosynthesis, which was the main polyol produced in significant quantities (=36.84 g L−1) with a corresponding conversion yield of 0.51 g g−1.


Molecules ◽  
2021 ◽  
Vol 26 (23) ◽  
pp. 7172
Author(s):  
Jakub Frątczak ◽  
Héctor de Paz Carmona ◽  
Zdeněk Tišler ◽  
José M. Hidalgo Herrador ◽  
Zahra Gholami

The Fischer–Tropsch heavy fraction is a potential feedstock for transport-fuels production through co-processing with fossil fuel fraction. However, there is still the need of developing new and green catalytic materials able to process this feedstock into valuable outputs. The present work studies the co-hydrocracking of the Fisher–Tropsch heavy fraction (FT-res.) with vacuum gas oil (VGO) at different ratios (FT-res. 9:1 VGO, FT-res. 7:3 VGO, and FT-res. 5:5 VGO) using phonolite-based catalysts (5Ni10W/Ph, 5Ni10Mo/Ph, and 5Co10Mo/Ph), paying attention to the overall conversion, yield, and selectivity of the products and properties. The co-processing experiments were carried out in an autoclave reactor at 450 °C, under 50 bars for 1 and 2 h. The phonolite-based catalysts were active in the hydrocracking of FT-res.:VGO mixtures, presenting different yields to gasoline, diesel, and jet fuel fractions, depending on the time of reaction and type of catalyst. Our results enable us to define the most suitable metal transition composition for the phonolite-based support as a hydrocracking catalyst.


2021 ◽  
Author(s):  
Ebru Tunç ◽  
Emir Zafer Hoşgün ◽  
Halit L. Hoşgün ◽  
Berrin Bozan

Abstract In this study, transition metal doped montmorillonite catalyts (Cr-MMT, Cu-MMT, Fe-MMT and Zn-MMT) were successfully synthesized by hydrothermal method and evaluated for the conversion of cellulose to 5-HMF in the water media. Metal-MMT catalysts were characterized by XRD, BET, Ammonia-TPD and pyridine-FTIR to investigate the properties of the samples. Using Cr-MMT, an efficient conversion of cellulose to 5-HMF was achieved in the water system, affording a conversion yield 93.47% and 5-HMF yield 9.07% within 6 h at 200oC.


Catalysts ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1126
Author(s):  
Qingman Li ◽  
Qihua Jiang ◽  
Pengcheng Gu ◽  
Lianju Ma ◽  
Yiwu Wang

Ni2+-NTA-boosted magnetic porous silica nanoparticles (Ni@MSN) to serve as ideal support for bi-functional enzyme were fabricated for the first time. The versatility of this support was validated by one-step purification and immobilization of bi-functional enzyme MLG consisting of 3-Quinuclidinone reductase and glucose dehydrogenase, which can simultaneously catalyze both carbonyl reduction and cofactor regeneration, to fabricate an artificial bi-functional nanobiocatalyst (namely, MLG-Ni@MSN). The enzyme loading of 71.7 mg/g support and 92.7% immobilization efficiency were obtained. Moreover, the immobilized MLG showed wider pH and temperature tolerance and greater storage stability than free MLG under the same conditions. The nanosystem was employed as biocatalyst to accomplish the 3-quinuclidinone (70 g/L) to (R)-3-quinuclidinol biotransformation in 100% conversion yield with >99% selectivity within 6 h and simultaneous cofactor regeneration. Furthermore, the immobilized MLG retained up to 80.3% (carbonyl reduction) and 78.0% (cofactor regeneration) of the initial activity after being recycled eight times. In addition, the MLG-Ni@MSN system exhibited almost no enzyme leaching during biotransformation and recycling. Therefore, we have reason to believe that the Ni@MSN support gave great promise for constructing a new biocatalytic nanosystem with multifunctional enzymes to achieve some other complex bioconversions.


Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3258
Author(s):  
Hamed M. Alshammari ◽  
Mohammad Hayal Alotaibi ◽  
Obaid F. Aldosari ◽  
Abdulellah S. Alsolami ◽  
Nuha A. Alotaibi ◽  
...  

The present study investigates a process for the selective production of hydrogen from the catalytic decomposition of formic acid in the presence of iridium and iridium–palladium nanoparticles under various conditions. It was found that a loading of 1 wt.% of 2% palladium in the presence of 1% iridium over activated charcoal led to a 43% conversion of formic acid to hydrogen at room temperature after 4 h. Increasing the temperature to 60 °C led to further decomposition and an improvement in conversion yield to 63%. Dilution of formic acid from 0.5 to 0.2 M improved the decomposition, reaching conversion to 81%. The reported process could potentially be used in commercial applications.


Author(s):  
Winda Rahmalia ◽  
Imelda H. Silalahi ◽  
Thamrin Usman ◽  
Jean-François Fabre ◽  
Zéphirin Mouloungui ◽  
...  

AbstractIn this research, treated metakaolinite (TMK) was introduced into the TiO2 photoelectrode to fabricated dye-sensitized solar cells (DSSCs). The photovoltaic cells have four main natural components, i.e., a photosensitizer (carotenoid bixin), photoelectrode (TiO2/kaolinite), electrolyte (glycerine carbonate derivative), and counter-electrode (carbon). Their stability, reusability, and equivalent circuit were studied. The presence of 5% of TMK in anatase TiO2 paste decreased the TiO2 band gap from 3.21 to 3.16 eV. The result showed that the presence of 5% of TMK in TiO2 paste was more favorable to obtain higher energy conversion efficiency. Under a light intensity of 200 W/m2, it produced an energy conversion yield of 0.086%. The combination of the electrolyte and the TMK demonstrated a synergistic effect to improve the electrical properties of the DSSC. The energy storage function worked well until the third day of analysis. The DSSC based on TiO2/TMK photoelectrode exhibited 16 times better stability than pure TiO2-based photoelectrode. The Faraday charge transfer processes showed that the TiO2/TMK photoelectrode is not in direct contact with the carbon counter-electrode.


2021 ◽  
Author(s):  
Afsaneh Alishahi ◽  
MEHRDAD NIAKOUSARI ◽  
Mohammad Taghi Golmakani

Abstract The ohmic-assisted esterification method was compared and contrasted with the conventional esterification method for biodiesel (fatty acid methyl esters) production from vegetable oil refinery waste containing high free fatty acids. The reaction variables were free fatty acid:methanol molar ratio (1:1, 1:5, 1:10, and 1:15), catalyst concentration (1%, 2%, and 3%) and reaction time (5, 30, and 60 min). By increasing the conversion yield of free fatty acids to fatty acid methyl esters, density increased while viscosity and refractive index decreased. Optimum reaction conditions were a molar ratio of 1:10 and a catalyst concentration of 3% after 60 min of esterification reaction, while having a 95.74% conversion yield. There was no significant difference between fatty acid methyl esters produced with ohmic-assisted esterification and conventional esterification methods in terms of fatty acid profile, physicochemical and heating properties. Meanwhile, energy consumption by the conventional esterification method was about 25% higher than that of ohmic-assisted esterification. In fact, ohmic-assisted esterification can be considered as a green, cost-effective alternative method for the production of biodiesel from vegetable oil refinery waste.


PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0250513
Author(s):  
Gerard Masdeu ◽  
Luis Miguel Vázquez ◽  
Josep López-Santín ◽  
Gloria Caminal ◽  
Slavko Kralj ◽  
...  

Fructose-6-phosphate aldolase (FSA) is an important enzyme for the C-C bond-forming reactions in organic synthesis. The present work is focused on the synthesis of a precursor of D-fagomine catalyzed by a mutant FSA. The biocatalyst has been immobilized onto several supports: magnetic nanoparticle clusters (mNC), cobalt-chelated agarose (Co-IDA), amino-functionalized agarose (MANA-agarose) and glyoxal-agarose, obtaining a 29.0%, 93.8%, 89.7% and 53.9% of retained activity, respectively. Glyoxal-agarose FSA derivative stood up as the best option for the synthesis of the precursor of D-fagomine due to the high reaction rate, conversion, yield and operational stability achieved. FSA immobilized in glyoxal-agarose could be reused up to 6 reaction cycles reaching a 4-fold improvement in biocatalyst yield compared to the non-immobilized enzyme.


2021 ◽  
Author(s):  
Hassan H. Hammud ◽  
Mohammed A Alkhalifah ◽  
Hassan Traboulsi ◽  
Ranjith Kumar Karnati ◽  
Syed Ghazanfar Hussain ◽  
...  

Abstract Cobalt carbon nanoparticles CoCNPs were prepared by pyrolysis of cobalt phenanthroline complex at different pyrolysis temperature and time of pyrolysis and used for the catalytic hydrogenation of 2,4-dinitrophenol. CoCNPs (1) and (3) were prepared by heating at 600 ºC and 800 °C respectively, while (2) was prepared by heating at 600 °C with an additional intermediate stage at 300 °C. The structures and chemical properties of the three catalysts were correlated with their catalytic activities. Among the three studied catalysts, the highest rate constant was obtained for (2) while the highest conversion was achieved by (3). Our data show that an increase in oxygen content of the cobalt carbon nano-catalyst reduces the catalytic activity, while an increase in pyrolysis temperature improves the conversion yield.


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