scholarly journals Screening of Supports for the Immobilization of β-Glucosidase

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Joelise de Alencar Figueira ◽  
Fernanda Furlan Gonçalves Dias ◽  
Hélia Harumi Sato ◽  
Pedro Fernandes
Keyword(s):  
Catalytic Activity ◽  
Polyvinyl Alcohol ◽  
Sol Gel ◽  
Ph Stability ◽  
Activity Profile ◽  
Michaelis Constant ◽  
Diffusion Limitations ◽  
Two Systems ◽  
Selection Of

A set of supports were screened for the immobilization of a partially purified extract of β-glucosidase from Aspergillus sp. These supports, namely, Eupergit, Amberlite, alginate, gelatin, polyvinyl alcohol- (PVA-) based matrices (Lentikats), and sol-gel, have proved effective for the implementation of some other enzyme-based processes. The initial criterion for selection of promising supports prior to further characterization relied on the retention of the catalytic activity following immobilization. Based on such criterion, where immobilization in sol-gel and in Lentikats outmatched the remaining approaches, those two systems were further characterized. Immobilization did not alter the pH/activity profile, whereas the temperature/activity profile was improved when sol-gel support was assayed. Both thermal and pH stability were improved as a result of immobilization. An increase in the apparent KM (Michaelis constant) was observed following immobilization, suggesting diffusion limitations.

Nickel (II) and oxovanadium (IV) complexes supported on MCM-41 mesoporous and their application in catalytic selective sulfide and thiol oxidation

2020 ◽  
Vol 23 ◽  
Author(s):  
Mohsen Nikoorazm ◽  
Maryam Khanmoradi ◽  
Masoumeh Sayadian
Keyword(s):  
Catalytic Activity ◽  
Room Temperature ◽  
Sol Gel ◽  
Reaction Times ◽  
Significant Loss ◽  
Spectral Studies ◽  
High Catalytic Activity ◽  
Catalytic Systems ◽  
Solvent Free Conditions ◽  
Mcm 41

Introduction:: MCM-41 was synthesized using the sol-gel method. Then two new transition metal complexes of Nickel (II) and Vanadium (IV), were synthesized by immobilization of adenine (6-aminopurine) into MCM-41 mesoporous. The compounds have been characterized by XRD, TGA, SEM, AAS and FT-IR spectral studies. Using these catalysts provided an efficient and enantioselective procedure for oxidation of sulfides to sulfoxides and oxidative coupling of thiols to their corresponding disulfides using hydrogen peroxide at room temperature. Materials and Methods:: To a solution of sulfide or thiol (1 mmol) and H2O2 (5 mmol), a determined amount of the catalyst was added. The reaction mixture was stirred at room temperature for the specific time under solvent free conditions. The progress of the reaction was monitored by TLC using n-hexane: acetone (8:2). Afterwards, the catalyst was removed from the reaction mixture by centrifugation and, then, washed with dichloromethane in order to give the pure products. Results:: All the products were obtained in excellent yields and short reaction times indicating the high activity of the synthesized catalysts. Besides, the catalysts can be recovered and reused for several runs without significant loss in their catalytic activity. Conclusion:: These catalytic systems furnish the products very quickly with excellent yields and VO-6AP-MCM-41 shows high catalytic activity compared to Ni-6AP-MCM-41.

Monodisperse-porous cerium oxide microspheres as a new support with appreciable catalytic activity for a composite catalyst in benzyl alcohol oxidation

2021 ◽  
Author(s):  
Kadriye Özlem Hamaloğlu ◽  
Rukiye Babacan Tosun ◽  
Serap Ulu ◽  
Hakan Kayi ◽  
Cengiz Kavaklı ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Benzyl Alcohol ◽  
Cerium Oxide ◽  
Sol Gel ◽  
Alcohol Oxidation ◽  
Pd Nanoparticles ◽  
Composite Catalyst ◽  
Benzyl Alcohol Oxidation ◽  
Supported Pd

A synergistic catalyst in the form of monodisperse-porous CeO2 microspheres supported Pd nanoparticles (Pd NPs) was synthesized. CeO2 microspheres 4 μm in size were obtained by a newly developed “sol-gel...

scholarly journals Diffusion Limitations in Root Uptake of Cadmium and Zinc, But Not Nickel, and Resulting Bias in the Michaelis Constant

2012 ◽  
Vol 160 (2) ◽  
pp. 1097-1109 ◽  
Author(s):  
Fien Degryse ◽  
Afsaneh Shahbazi ◽  
Liesbeth Verheyen ◽  
Erik Smolders
Keyword(s):  
Root Uptake ◽  
Michaelis Constant ◽  
Diffusion Limitations

Immobilization of Nano-TiO2 on Expanded Perlite for Photocatalytic Degradation of Rhodamine B

2011 ◽  
Vol 110-116 ◽  
pp. 3795-3800 ◽  
Author(s):  
Xiao Zhi Wang ◽  
Wei Wei Yong ◽  
Wei Qin Yin ◽  
Ke Feng ◽  
Rong Guo
Keyword(s):  
Catalytic Activity ◽  
Photocatalytic Degradation ◽  
Rhodamine B ◽  
Degradation Kinetics ◽  
Irradiation Time ◽  
Sol Gel ◽  
Polluted Water ◽  
Order Kinetic ◽  
Expanded Perlite ◽  
Initial Concentration

Expanded perlite (EP) modified titanium dioxide (TiO2) with different loading times were prepared by Sol-Gel method. Photocatalytic degradation kinetics of Rhodamine B (RhB) in polluted water by the materials (EP-nanoTiO2), as well as the effects of different loading times and the initial concentration of RhB on photocatalysis rate were examined. The catalytic activity of the regenerated photocatalyst was also tested. The results showed that photocatalyst modified three times with TiO2had the highest catalytic activity. Degradation ratio of RhB by EP-nanoTiO2(modified three times) under irradiation for 6 h were 98.0%, 75.6% and 63.2% for 10 mg/L, 20 mg/L and 30 mg/L, respectively.The photocatalyst activity has little change after the five times recycling, and the degradation rate of RhB decreased less than 8%. The reaction of photocatalysis for RhB with irradiation time can be expressed as first-order kinetic mode within the initial concentration range of RhB between 10mg/L and 30 mg/L. EP-nanoTiO2photocatalyst has a higher activity and stability to degrade RhB in aqueous solution.

Effect of Complexing Agent on Morphology and Crystal Structure of La1-xCexCoO3 (x=0, 0.2, and 0.4) Perovskite-Type Mixed Oxides Catalyst Prepared by Sol-Gel Method

2010 ◽  
Vol 658 ◽  
pp. 29-32 ◽  
Author(s):  
Kanit Soongprasit ◽  
Duangdao Aht-Ong ◽  
Viboon Sricharoenchaikul ◽  
Duangduen Atong
Keyword(s):  
Crystal Structure ◽  
Polyvinyl Alcohol ◽  
Mixed Oxides ◽  
Sol Gel ◽  
Value Added ◽  
Molar Ratio ◽  
Complexing Agent ◽  
Nitrate Hexahydrate ◽  
Mixed Oxide Catalysts ◽  
Perovskite Type

. La1-xCexCoO3 (x=0, 0.2, and 0.4) perovskite-type mixed oxides using polyvinyl alcohol (PVA) as complexing agent at two molar ratio of metal ion to PVA (1:1 and 1:2) were successfully prepared by sol-gel process. The precursor included lanthanum (II) nitrate hexahydrate, cerium (II) nitrate hexahydrate, and cobalt (II) nitrate hexahydrate where polyvinyl alcohol was added as complexing agent. The suitable condition of Cerium (Ce) substitution and PVA molar ratio were established for further application in hydrocarbon conversion to high value added products. TGA thermogram of as-prepared precursor showed that PVA absolutely decomposed at temperature higher than 500°C. XRD patterns of calcined catalyst showed both LaCoO3 rhombohedral and CeO2 cubic structures that confirmed the formation of mixed crystal structure. Nevertheless, Co3O4 slightly appeared with low peak intensity which came from the oxidation reaction of as-prepared catalyst during calcinations. XRD showed that PVA did not effect to crystal structure of synthesized catalyst. Higher PVA content added in the precursor cause the reduction of crystal growth of catalyst in calcinations step. In contrast, morphology of catalyst is directly related with PVA content such that the spongy and sheet-like structure were formed with increasing PVA content which prevented the agglomeration of particles. The results showed that PVA content play an important role in morphology of perovskite-type mixed oxide catalysts but did not affected to their crystal structures.

Catalytic activity of Co-åkermanite and Co-pyroxene in oxidation reactions

2011 ◽  
Vol 89 (8) ◽  
pp. 939-947 ◽  
Author(s):  
Irena Mihailova ◽  
Dimitar Mehandjiev
Keyword(s):  
Catalytic Activity ◽  
Solid Phase ◽  
Sol Gel ◽  
Cobalt Content ◽  
Octahedral Coordination ◽  
Tetrahedral Coordination ◽  
Oxidation Reactions ◽  
Oxidation Of Co ◽  
Phase Synthesis ◽  
Catalytically Active

Two calcium–cobalt silicates were synthesized in which cobalt occupies different structural positions. The crystal phases belong to two main structural silicate types. In the Co-åkermanite structure (Ca2CoSi2O7), cobalt cations take tetrahedral coordination toward oxygen atoms. In the Co-pyroxene structure of CaCoSi2O6, cobalt displays octahedral coordination. Ca2CoSi2O7 was prepared by solid-phase synthesis and CaCoSi2O6 was prepared by sol–gel method. The synthesis of the phases was confirmed by XRD, FTIR, and EPR data. On the basis of the XPS analysis, it can be concluded that Co2+ cations exist in the studied silicates. Thus, it is possible to study the catalytic activity of two silicate phases containing Co2+ cations in different coordinations: tetrahedral and octahedral. It was found that cobalt silicates with crystal structures corresponding to pyroxene and åkermanite possess catalytic activity in the reactions of complete oxidation of CO and toluene. Co-pyroxene exhibits higher catalytic activity than Co-åkermanite, but the higher cobalt content on the surface of Co-pyroxene should also be taken into account. Then, it turns out that catalytically active complexes with Со2+ ions in tetrahedral coordination are more efficient than those with such ions in octahedral coordination when equal concentrations of cobalt were used on the surface of the catalysts.

Enhancement of Catalytic Activity and Selectivity for the Gaseous Electroreduction of CO 2 to CO: Guidelines for the Selection of Carbon Supports

2021 ◽  
pp. 2100216
Author(s):  
Chulwan Lim ◽  
Woong Hee Lee ◽  
Jong Ho Won ◽  
Young‐Jin Ko ◽  
Sangkuk Kim ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Carbon Supports ◽  
Selection Of

Ultra-precision grinding of 4H-SiC wafer by PAV/PF composite sol-gel diamond wheel

2021 ◽  
Vol 13 (9) ◽  
pp. 168781402110449
Author(s):  
Kaiping Feng ◽  
Tianchen Zhao ◽  
Binghai Lyu ◽  
Zhaozhong Zhou
Keyword(s):  
Surface Roughness ◽  
Low Temperature ◽  
Polyvinyl Alcohol ◽  
Feed Rate ◽  
Hot Pressing ◽  
Phenolic Resin ◽  
Sol Gel ◽  
Diamond Wheel ◽  
Sic Wafer ◽  
Better Than

To eliminate the deep scratches on the 4H-SiC wafer surface in the grinding process, a PVA/PF composite sol-gel diamond wheel was proposed. Diamond and fillers are sheared and dispersed in the polyvinyl alcohol-phenolic resin composite sol glue, repeatedly frozen at a low temperature of −20°C to gel, then 180°C sintering to obtain the diamond wheel. Study shows that the molecular chain of polyvinyl alcohol-phenolic resin is physically cross-linked to form gel under low-temperature conditions. Tested by mechanical property testing machines, microhardness tester, and SEM. The results show that micromorphology is more uniform, the strength of the sol-gel diamond wheel is higher, the hardness uniformity is better than that of the hot pressing diamond wheel. Grinding experiments of 4H-SiC wafer were carried out with the prepared sol-gel diamond wheel. The influence of grinding speed, feed rate, and grinding depth on the surface roughness was investigated. The results showed that by using the sol-gel diamond wheel, the surface quality of 4H-SiC wafer with an average surface roughness Ra 6.42 nm was obtained under grinding wheel speed 7000 r/min, grinding feed rate 6 µm/min, and grinding depth 15 µm, the surface quality was better than that of using hot pressing diamond wheel.

Synthesis by sol–gel process, characterization and catalytic activity of vanadia–silica mixed oxides

2005 ◽  
Vol 351 (46-48) ◽  
pp. 3624-3629 ◽  
Author(s):  
Mariza Alves Figueiredo ◽  
André Luiz de Faria ◽  
Marilda das Dores Assis ◽  
Herenilton Paulino Oliveira
Keyword(s):  
Catalytic Activity ◽  
Mixed Oxides ◽  
Sol Gel ◽  
Process Characterization ◽  
Sol Gel Process

scholarly journals Study Structural properties of Nanocomposite (polyvinyl Alcohol\ (CdO/NiO) via Sol-Gel Method

2021 ◽  
Author(s):  
Amatalkareem Mohammed Al-Jezbi
Keyword(s):  
Polyvinyl Alcohol ◽  
Structural Properties ◽  
Sol Gel ◽  
Cadmium Oxide ◽  
Antibacterial Activities ◽  
Oxide Mixture ◽  
Gel Method ◽  
Sol Gel Method ◽  
Diffraction Patterns ◽  
Cracking Process

Abstract This study deals with the synthesis of some physical properties of (CdO/NiO) nanocomposite via Sol-Gel method and their antibacterial activities. The NiO and CdO nanoxides as well as the CdO/NiO oxide mixture were prepared in five samples with different concentrations where the ratio of CdO/NiO was [(1: 0), (3: 1), (1: 1), (1: 3), (0: 1)], by using the gel solution by means of a polyvinyl alcohol solution ( PVA ). The samples were platelimb at (500̊C) for three hours. The structural properties of the prepared oxides resulting from the cracking process were studied. The XRD results showed the presence of pure cadmium oxide diffraction patterns in the sample (S 1 ) as well as pure nickel oxide in the sample (S 5 ), and confirmed the presence of the CdO / NiO oxide mixture in the samples (S 2 , S 3 , S 4 ). The results of XRD also showed, through calculations, that the specific surface area increased with increasing granular size and decreased with decreasing granular size. XRD calculations also showed that the intensity of eruptions decreased as the granular volume increased and, inversely, increased with decreasing granular size.

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