scholarly journals The Influence of the Gold Particle Size on the Catalytic Oxidation of 5-(Hydroxymethyl)furfural

Catalysts ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 342 ◽  
Author(s):  
Oliver Schade ◽  
Paolo Dolcet ◽  
Alexei Nefedov ◽  
Xiaohui Huang ◽  
Erisa Saraçi ◽  
...  
Keyword(s):  
Particle Size ◽  
Functional Groups ◽  
Chemical Reduction ◽  
Large Fraction ◽  
Particle Sizes ◽  
Mean Particle Size ◽  
Hydroxymethyl Furfural ◽  
Highly Active ◽  
Surface Steps ◽  
Aldehyde Oxidation

For the production of chemicals from biomass, new selective processes are required. The selective oxidation of 5-(Hydroxymethyl)furfural (HMF), a promising platform molecule in fine chemistry, to 2,5-furandicarboxylic acid (FDCA) is considered a promising approach and requires the oxidation of two functional groups. In this study, Au/ZrO2 catalysts with different mean particle sizes were prepared by a chemical reduction method using tetrakis(hydroxymethyl)phosphonium chloride (THPC) and tested in HMF oxidation. The catalyst with the smallest mean particle size (2.1 nm) and the narrowest particle size distribution was highly active in the oxidation of the aldehyde moiety of HMF, but less active in alcohol oxidation. On the other hand, increased activity in FDCA synthesis up to 92% yield was observed over catalysts with a larger mean particle size (2.7 nm), which had a large fraction of small and some larger particles. A decreasing FDCA yield over the catalyst with the largest mean particle size (2.9 nm) indicates that the oxidation of both functional groups require different particle sizes and hint at the presence of an optimal particle size for both oxidation steps. The activity of Au particles seems to be influenced by surface steps and H bonding strength, the latter particularly in aldehyde oxidation. Therefore, the presence of both small and some larger Au particles seem to give catalysts with the highest catalytic activity.

Chemical reduction of chlorpyrifos driven by flavin mononucleotide functionalized titanium (IV) dioxide

2020 ◽  
Vol 5 (11) ◽  
Author(s):  
Stephanie Santos Díaz ◽  
Hazim Al-Zubaidi ◽  
Amir C. Ross-Obare ◽  
Sherine O. Obare
Keyword(s):  
Functional Groups ◽  
Organic Contaminants ◽  
Chemical Reduction ◽  
Flavin Mononucleotide ◽  
Reaction Conditions ◽  
Organophosphate Compounds ◽  
Biological Molecule ◽  
Highly Active ◽  
New Directions ◽  
Detrimental Impact

AbstractFor many decades, organohalide and organophosphate compounds have shown significant detrimental impact on the environment. Consequently, strategies for their remediation continue to be an area of emerging need. The reduction of the chlorpyrifos pesticide, a molecule that bears both organohalide and organophosphate functional groups, is an important area of investigation due to it toxic nature. In this report, we demonstrate the effectiveness of the biological molecule, flavin mononucleotide (FMN) toward chemically reducing chlorpyrifos. The FMN was found to be highly active when anchored to nanocrystalline TiO2 surfaces. The results show new directions toward the remediation of organic contaminants under mild reaction conditions.

An initial test of a method for the estimation of real mean particle size from shadowed samples

1985 ◽  
Vol 31 (7) ◽  
pp. 604-607
Author(s):  
J. H. M. Willison
Keyword(s):  
Particle Size ◽  
Present Method ◽  
Particle Sizes ◽  
Initial Test ◽  
Small Particles ◽  
Mean Particle Size ◽  
Sample Rotation ◽  
Mean Diameter ◽  
The Mean

During shadowing, a "cap" of metal develops on small particles. This cap increases, apparent particle width (measured normal to the shadowing direction) by an extent which cannot be predetermined. The extent of this increase in particle size (here defined as the "cap," X) is estimated in the present method by using opposite (180° sample rotation) bidirectional shadowing. It is argued that the bidirectional cap is the sum of the two unidirectional caps, and therefore that X = 2A − (B + C), where A is the mean bidirectionally shadowed particle size, and B and C are the two mean unidirectionally shadowed particle sizes. As a validation of the method, the mean diameter of air-dried ferritin was estimated and the results appear to confirm the hypothesis (mean diameter by present method, 10.7 ± 0.2 nm; mean diameter by previous methods, 10.89 nm).

Spatial and Temporal Patterns in Macrobenthic Stream Diversity

1976 ◽  
Vol 33 (6) ◽  
pp. 1261-1270 ◽  
Author(s):  
Brigitte G. E. de March
Keyword(s):  
Particle Size ◽  
Related Species ◽  
High Variability ◽  
Particle Sizes ◽  
Spatial And Temporal Patterns ◽  
Mean Particle Size ◽  
Faunal Assemblages ◽  
Number Of Species ◽  
Stream Community ◽  
The Relationship

The relationship between the characteristics of a stream community and sediments were studied for 1 yr in a small unpolluted river with a morainal substrate. Recognizable faunal assemblages were associated with silt or silt fill, sand or sand fill, and large boulders. The fauna in sediments of mean particle sizes coarser than sand but finer than boulders was characterized by a high variability due largely to temporal successions of morphologically related species. It was found that the number of species was directly proportional to mean particle size (in [Formula: see text] units) in spring when the sediments were well sorted, but the relationship broke down as the sediment interstices filled in. In late fall when the sediments were badly sorted, the number of species is perhaps more related to the sorting coefficient of the sediments. The relevance of these findings to studies of pollution is discussed.

scholarly journals Synthesis of the platinum particle with the pH variation for the particle size control

2021 ◽  
Vol 2145 (1) ◽  
pp. 012038
Author(s):  
P Thongnopkun ◽  
W Kitprapot
Keyword(s):  
Particle Size ◽  
Chemical Reduction ◽  
Intrinsic Value ◽  
Size Control ◽  
Spherical Shape ◽  
Platinum Particle ◽  
Particle Sizes ◽  
Sem Images ◽  
Ph Variation ◽  
Reduction Methods

Abstract Platinum is a precious metal widely used in the jewelry industry due to its property and intrinsic value. The different particle sizes of platinum can be applied in various applications, especially for jewelry production. In the present article, submicron, and nano-sized platinum particle sizes were synthesized through simple chemical reduction methods and the effect of pH variation was revealed. The scanning electron microscope (SEM) images showed that the pH variations give rise to significant changes of the obtained particle size. The size of platinum particle was decreased from submicron to nanoscale while the pH was increased. The UV-Vis spectra indicated the maximum absorption at 220 nm confirming the spherical shape of the platinum particle. The FT-IR spectroscopy was used to analyze the residuals from the synthesis. The result showed that there is no indication of residual in the synthesized particle. Additionally, this synthesis can provide stability in terms of size and shape, as well as high production yield.

scholarly journals The Effect of Gasification Conditions on the Surface Properties of Biochar Produced in a Top-Lit Updraft Gasifier

2020 ◽  
Vol 10 (2) ◽  
pp. 688 ◽  
Author(s):  
Arthur M. James R. ◽  
Wenqiao Yuan ◽  
Duo Wang ◽  
Donghai Wang ◽  
Ajay Kumar
Keyword(s):  
Particle Size ◽  
Moisture Content ◽  
Surface Properties ◽  
Functional Groups ◽  
Cation Exchange Capacity ◽  
Functional Group ◽  
Exchange Capacity ◽  
Low Ph ◽  
Airflow Rate ◽  
Particle Sizes

The effect of airflow rate, biomass moisture content, particle size, and compactness on the surface properties of biochar produced in a top-lit updraft gasifier was investigated. Pine woodchips were studied as the feedstock. The carbonization airflow rates from 8 to 20 L/min were found to produce basic biochars (pH > 7.0) that contained basic functional groups. No acid functional groups were presented when the airflow increased. The surface charge of biochar at varying airflow rates showed that the cation exchange capacity increased with airflow. The increase in biomass moisture content from 10 to 14% caused decrease in the pH from 12 to 7.43, but the smallest or largest particle sizes resulted in low pH; therefore, the carboxylic functional groups increased. Similarly, the biomass compactness exhibited a negative correlation with the pH that reduced with increasing compactness level. Thus, the carboxylic acid functional groups of biochar increased from 0 to 0.016 mmol g−1, and the basic functional group decreased from 0.115 to 0.073 mmol g−1 when biomass compactness force increased from 0 to 3 kg. BET (Brunauer-Emmett-Teller) surface area of biochar was greater at higher airflow and smaller particle size, lower moisture content, and less compactness of the biomass.

Surface energy of cellulosic materials: The effect of particle morphology, particle size, and hydroxyl number

TAPPI Journal ◽  
2015 ◽  
Vol 14 (9) ◽  
pp. 565-576 ◽  
Author(s):  
YUCHENG PENG ◽  
DOUGLAS J. GARDNER
Keyword(s):  
Particle Size ◽  
Surface Energy ◽  
Particle Morphology ◽  
Nanofibrillated Cellulose ◽  
Particle Sizes ◽  
Hydroxyl Number ◽  
Small Individual ◽  
Dispersion Component ◽  
Commercial Applications ◽  
Lower Temperature

Understanding the surface properties of cellulose materials is important for proper commercial applications. The effect of particle size, particle morphology, and hydroxyl number on the surface energy of three microcrystalline cellulose (MCC) preparations and one nanofibrillated cellulose (NFC) preparation were investigated using inverse gas chromatography at column temperatures ranging from 30ºC to 60ºC. The mean particle sizes for the three MCC samples and the NFC sample were 120.1, 62.3, 13.9, and 9.3 μm. The corresponding dispersion components of surface energy at 30°C were 55.7 ± 0.1, 59.7 ± 1.3, 71.7 ± 1.0, and 57.4 ± 0.3 mJ/m2. MCC samples are agglomerates of small individual cellulose particles. The different particle sizes and morphologies of the three MCC samples resulted in various hydroxyl numbers, which in turn affected their dispersion component of surface energy. Cellulose samples exhibiting a higher hydroxyl number have a higher dispersion component of surface energy. The dispersion component of surface energy of all the cellulose samples decreased linearly with increasing temperature. MCC samples with larger agglomerates had a lower temperature coefficient of dispersion component of surface energy.

Application of Plakett-Burman Screening Design in Optimization of Process Parameters for Formulation of Canaglifozin Nanosuspension

2020 ◽  
Vol 13 (6) ◽  
pp. 5208-5216
Author(s):  
Nisha Patel ◽  
Hitesh A Patel
Keyword(s):  
Particle Size ◽  
Particle Diameter ◽  
Spherical Shape ◽  
Water Soluble ◽  
Pareto Chart ◽  
Independent Variables ◽  
Mean Particle Size ◽  
Screening Design ◽  
Stirring Time ◽  
Response Variables

In this study, we sought to improve the dissolution characteristics of a poorly water-soluble BCS class IV drug canaglifozin, by preparing nanosuspension using media milling method. A Plackett–Burman screening design was employed to screen the significant formulation and process variables. A total of 12 experiment were generated by design expert trial version 12 for screening 5 independent variables namely the amount of stabilizer in mg (X1), stirring time in hr (X2), amt of Zirconium oxide beads in gm (X3), amount of drug in mg (X4) and stirring speed in rpm (X5) while mean particle size in nm (Y1) and drug release in 10 min. were selected as the response variables. All the regression models yielded a good fit with high determination coefficient and F value. The Pareto chart depicted that all the independent variables except the amount of canaglifozin had a significant effect (p<0.001) on the response variables. The mathematical model for mean particle size generated from the regression analysis was given by mean particle size = +636.48889 -1.28267 amt of stabilizer(X1) -4.20417 stirring time (X2) -7.58333 amt of ZrO2 beads(X3) -0.105556 amt of drug(X4) -0.245167 stirring speed(X5) (R2=0.9484, F ratio=22.07, p<0.001). Prepared canaglifozin nanosuspension exemplified a significant improvement (p<0.05) in the release as compared to pure canaglifozin and marketed tablet with the optimum formulation releasing almost 80% drug within first 10min. Optimized nanosuspension showed spherical shape with surface oriented stabilizer molecules and a mean particle diameter of 120.5 nm. There was no change in crystalline nature after formulation and it was found to be chemically stable with high drug content.

scholarly journals Effect of particle size on phytochemical composition and antioxidant properties of Sargassum cristaefolium ethanol extract

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
E. S. Prasedya ◽  
A. Frediansyah ◽  
N. W. R. Martyasari ◽  
B. K. Ilhami ◽  
A. S. Abidin ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Particle Size ◽  
Antioxidant Activities ◽  
Antioxidant Properties ◽  
Ethanol Extract ◽  
Total Phenolic ◽  
Particle Sizes ◽  
Epicatechin Gallate ◽  
Particle Size Reduction ◽  
Phytochemical Composition

AbstractSample particle size is an important parameter in the solid–liquid extraction system of natural products for obtaining their bioactive compounds. This study evaluates the effect of sample particle size on the phytochemical composition and antioxidant activity of brown macroalgae Sargassum cristaefolium. The crude ethanol extract was extracted from dried powders of S.cristeafolium with various particle sizes (> 4000 µm, > 250 µm, > 125 µm, > 45 µm, and < 45 µm). The ethanolic extracts of S.cristaefolium were analysed for Total Phenolic Content (TPC), Total Flavonoid Content (TFC), phenolic compound concentration and antioxidant activities. The extract yield and phytochemical composition were more abundant in smaller particle sizes. Furthermore, the TPC (14.19 ± 2.08 mg GAE/g extract to 43.27 ± 2.56 mg GAE/g extract) and TFC (9.6 ± 1.8 mg QE/g extract to 70.27 ± 3.59 mg QE/g extract) values also significantly increased as particle sizes decreased. In addition, phenolic compounds epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), and Epigallocatechin gallate (EGCG) concentration were frequently increased in samples of smaller particle sizes based on two-way ANOVA and Tukey’s multiple comparison analysis. These results correlate with the significantly stronger antioxidant activity in samples with smaller particle sizes. The smallest particle size (< 45 µm) demonstrated the strongest antioxidant activity based on DPPH, ABTS, hydroxyl assay and FRAP. In addition, ramp function graph evaluates the desired particle size for maximum phytochemical composition and antioxidant activity is 44 µm. In conclusion, current results show the importance of particle size reduction of macroalgae samples to increase the effectivity of its biological activity.

scholarly journals Experimental Analysis of the Mechanical Properties and Resistivity of Tectonic Coal Samples with Different Particle Sizes

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2303
Author(s):  
Congyu Zhong ◽  
Liwen Cao ◽  
Jishi Geng ◽  
Zhihao Jiang ◽  
Shuai Zhang
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Uniaxial Compressive Strength ◽  
Coalbed Methane ◽  
Coal Sample ◽  
Fine Particles ◽  
Particle Sizes ◽  
Tectonic Coal

Because of its weak cementation and abundant pores and cracks, it is difficult to obtain suitable samples of tectonic coal to test its mechanical properties. Therefore, the research and development of coalbed methane drilling and mining technology are restricted. In this study, tectonic coal samples are remodeled with different particle sizes to test the mechanical parameters and loading resistivity. The research results show that the particle size and gradation of tectonic coal significantly impact its uniaxial compressive strength and elastic modulus and affect changes in resistivity. As the converted particle size increases, the uniaxial compressive strength and elastic modulus decrease first and then tend to remain unchanged. The strength of the single-particle gradation coal sample decreases from 0.867 to 0.433 MPa and the elastic modulus decreases from 59.28 to 41.63 MPa with increasing particle size. The change in resistivity of the coal sample increases with increasing particle size, and the degree of resistivity variation decreases during the coal sample failure stage. In composite-particle gradation, the proportion of fine particles in the tectonic coal sample increases from 33% to 80%. Its strength and elastic modulus increase from 0.996 to 1.31 MPa and 83.96 to 125.4 MPa, respectively, and the resistivity change degree decreases. The proportion of medium particles or coarse particles increases, and the sample strength, elastic modulus, and resistivity changes all decrease.

scholarly journals Investigation of the kinetics of spontaneous combustion of the major coal seam in Dahuangshan mining area of the Southern Junggar coalfield, Xinjiang, China

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Li Shen ◽  
Qiang Zeng
Keyword(s):  
Particle Size ◽  
High Temperature ◽  
Coal Seam ◽  
Spontaneous Combustion ◽  
Heating Temperature ◽  
Characteristic Temperature ◽  
Mining Area ◽  
Particle Sizes ◽  
Coal Oxidation ◽  
Increasing Temperature

AbstractIn the present paper, with using diverse methods (including the SEM, the XRD, the TPO, the FTIR, and the TGA) , the authors analysed samples of the major coal seam in Dahuangshan Mining area with different particle sizes and with different heated temperatures (from 50 to 800 °C at regular intervals of 50 °C). The results from SEM and XRD showed that high temperature and high number of pores, fissures, and hierarchical structures in the coal samples could facilitate oxidation reactions and spontaneous combustion. A higher degree of graphitization and much greater number of aromatic microcrystalline structures facilitated spontaneous combustion. The results from TPO showed that the oxygen consumption rate of the coal samples increased exponentially with increasing temperature. The generation rates of different gases indicated that temperatures of 90 °C or 130 °C could accelerate coal oxidation. With increasing temperature, the coal oxidation rate increased, and the release of gaseous products was accelerated. The FTIR results showed that the amount of hydroxide radicals and oxygen-containing functional groups increased with the decline in particle size, indicating that a smaller particle size may facilitate the oxidation reaction and spontaneous combustion of coal. The absorbance and the functional group areas at different particle sizes were consistent with those of the heated coal samples, which decreased as the temperature rose. The results from TGA showed that the characteristic temperature T3 declined with decreasing particle size. After the sample with 0.15–0.18 mm particle size was heated, its carbon content decreased, and its mineral content increased, inhibiting coal oxidation. This result also shows that the activation energy of the heated samples tended to increase at the stage of high-temperature combustion with increasing heating temperature.

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