scholarly journals Ultralow Surface Tension Solvents Enable Facile COF Activation with Reduced Pore Collapse

2020 ◽  
Author(s):  
Dongyang Zhu ◽  
Rafael Verduzco
Keyword(s):  
Surface Tension ◽  
Membrane Filtration ◽  
High Surface ◽  
Nitrogen Adsorption ◽  
Activation Process ◽  
Strong Impact ◽  
Pore Collapse ◽  
Surface Areas ◽  
Accessible Surface ◽  
The Impact

<p>Covalent Organic Frameworks (COFs) are organic, crystalline, highly porous materials attractive for applications such as gas storage, gas separations, catalysis, contaminant adsorption and membrane filtration. Activation of COFs removes adsorbed solvents and impurities, but common methods for COF activation can result in collapse of porous structure and loss of accessible surface areas. Here, we present a study of the impact of solvent surface tension on the activation process and demonstrate that activation using the ultralow surface tension solvent perfluorohexane (PFH) is simple and effective for a range of COF materials. We synthesized six different imine-based COFs through imine condensation reactions between tris(4-aminophenyl) benzene (TAPB) or 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and multi-functional di- and tri-benzaldehydes with different aromatic substituents. For each COF, we performed a solvent wash followed by vacuum drying using six solvents varying in surface tension from 11.9 – 72.8 mN m<sup>-1</sup>. Through powder X-ray diffraction (PXRD) measurements combined with nitrogen adsorption and desorption analysis, we found that some COF chemistries readily lost their porosity during activation with higher surface tension solvents while others were more robust. However, all COFs could be effectively activated using PFH to produce materials with excellent crystallinity and high surface areas, comparable to those for samples activated using supercritical CO<sub>2</sub>. This work demonstrates that the solvent surface tension used during activation has a strong impact on potential pore collapse, and activation using PFH provides a simple and effective activation method to produce COFs with excellent crystallinities and pore structures.</p>

scholarly journals Ultralow Surface Tension Solvents Enable Facile COF Activation with Reduced Pore Collapse

2020 ◽  
Author(s):  
Dongyang Zhu ◽  
Rafael Verduzco
Keyword(s):  
Surface Tension ◽  
Membrane Filtration ◽  
High Surface ◽  
Nitrogen Adsorption ◽  
Activation Process ◽  
Strong Impact ◽  
Pore Collapse ◽  
Surface Areas ◽  
Accessible Surface ◽  
The Impact

<p>Covalent Organic Frameworks (COFs) are organic, crystalline, highly porous materials attractive for applications such as gas storage, gas separations, catalysis, contaminant adsorption and membrane filtration. Activation of COFs removes adsorbed solvents and impurities, but common methods for COF activation can result in collapse of porous structure and loss of accessible surface areas. Here, we present a study of the impact of solvent surface tension on the activation process and demonstrate that activation using the ultralow surface tension solvent perfluorohexane (PFH) is simple and effective for a range of COF materials. We synthesized six different imine-based COFs through imine condensation reactions between tris(4-aminophenyl) benzene (TAPB) or 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and multi-functional di- and tri-benzaldehydes with different aromatic substituents. For each COF, we performed a solvent wash followed by vacuum drying using six solvents varying in surface tension from 11.9 – 72.8 mN m<sup>-1</sup>. Through powder X-ray diffraction (PXRD) measurements combined with nitrogen adsorption and desorption analysis, we found that some COF chemistries readily lost their porosity during activation with higher surface tension solvents while others were more robust. However, all COFs could be effectively activated using PFH to produce materials with excellent crystallinity and high surface areas, comparable to those for samples activated using supercritical CO<sub>2</sub>. This work demonstrates that the solvent surface tension used during activation has a strong impact on potential pore collapse, and activation using PFH provides a simple and effective activation method to produce COFs with excellent crystallinities and pore structures.</p>

Ejecta evolution during cone impact

2014 ◽  
Vol 752 ◽  
pp. 410-438 ◽  
Author(s):  
J. O. Marston ◽  
S. T. Thoroddsen
Keyword(s):  
Surface Tension ◽  
High Surface ◽  
Air Entrainment ◽  
High Impact ◽  
Self Similarity ◽  
Spatiotemporal Evolution ◽  
Solid Cone ◽  
High Surface Tension ◽  
Liquid Pools ◽  
The Impact

AbstractWe present findings from an experimental investigation into the impact of solid cone-shaped bodies onto liquid pools. Using a variety of cone angles and liquid physical properties, we show that the ejecta formed during the impact exhibits self-similarity for all impact speeds for very low surface tension liquids, whilst for high-surface tension liquids similarity is only achieved at high impact speeds. We find that the ejecta tip can detach from the cone and that this phenomenon can be attributed to the air entrainment phenomenon. We analyse of a range of cone angles, including some ogive cones, and impact speeds in terms of the spatiotemporal evolution of the ejecta tip. Using superhydrophobic cones, we also examine the entry of cones which entrain an air layer.

Study of the catalytic activity of Al-Fe pillared clays in the Baeyer–Villiger oxidation

Clay Minerals ◽  
2012 ◽  
Vol 47 (2) ◽  
pp. 275-284 ◽  
Author(s):  
L. S. Belaroui ◽  
A. Bengueddach
Keyword(s):  
Textural Properties ◽  
Nitrogen Adsorption ◽  
Pillared Clays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dissolved Iron ◽  
Surface Areas ◽  
Accessible Surface ◽  
Adsorption Desorption ◽  
Villiger Oxidation

AbstractThree types of AlFePILCs pillared clays have been prepared from Algerian clay precursors. They have been characterized and tested in the Baeyer–Villiger oxidation of cyclohexanone to caprolactone using benzaldehyde and oxygen as oxidant at room temperature. The structural and textural properties of the catalyst have been determined by X-ray diffraction, nitrogen adsorption-desorption isotherms and Mössbauer spectroscopy.The different activities of the clays have been related to their Fe contents and accessible surface areas. The induction period observed before the reaction started has been attributed to the dissolution of a portion of the Fe3+ cations, mediated by either the perbenzoic acid intermediate or the benzoic acid co-product. The reaction was indeed catalysed by a few ppm of dissolved iron cations and the catalysis of the Baeyer–Villiger oxidation reaction should mechanistically be considered as homogeneous.

A COMPARISON OF THE X-RAY DIFFRACTION AND NITROGEN ADSORPTION SURFACE AREAS OF CARBON BLACKS AND CHARCOALS

1948 ◽  
Vol 26a (4) ◽  
pp. 236-242 ◽  
Author(s):  
J. C. Arnell ◽  
W. M. Barss
Keyword(s):  
Carbonaceous Material ◽  
Nitrogen Adsorption ◽  
Activation Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Carbon Blacks ◽  
Surface Areas ◽  
Crystallite Surface ◽  
Adsorption Surface ◽  
Order Of Magnitude

The surface areas, as determined from X-ray diffraction and low temperature nitrogen adsorption data, were compared for a number of carbon blacks and activated charcoals. Comparative data were also obtained on samples of charcoal at various stages of activation and after calcination. The X-ray diffraction data indicated that all the samples examined were composed of small graphitelike crystallites of the same order of magnitude, which had specific surfaces of about 2500 to 3000 sq. m. per cc. The nitrogen adsorption surface of a highly activated charcoal was found to be about equal to the X-ray surface. It is suggested that the crystallite surface represents the potential adsorption surface of a carbonaceous material and, providing that crystal growth does not occur during activation, the activation process makes these surfaces available to external adsorbate.

scholarly journals Sulfidization of ferrihydrite in the presence of organic ligands

2021 ◽  
Author(s):  
Laurel K. ThomasArrigo ◽  
Sylvain Bouchet ◽  
Ralf Kaegi ◽  
Ruben Kretzschmar
Keyword(s):  
Trace Elements ◽  
High Surface ◽  
Organic Ligand ◽  
Organic Ligands ◽  
Molar Ratios ◽  
Iron Mineral ◽  
Surface Areas ◽  
Secondary Reactions ◽  
Mineral Components ◽  
The Impact

&lt;p&gt;In soils and sediments, short-range order (SRO) iron minerals constitute one of the most abundant and reactive mineral components. With high surface areas and points of zero charge near pH 7-8, SRO minerals like ferrihydrite (Fe&lt;sub&gt;10&lt;/sub&gt;O&lt;sub&gt;14&lt;/sub&gt;(OH)&lt;sub&gt;2&lt;/sub&gt;+mH&lt;sub&gt;2&lt;/sub&gt;O) are often linked to high adsorption of nutrients (C, N, P, S) and trace elements (e.g. As, Zn). However, under oxygen-limiting conditions, microbially derived sulfide (S(&amp;#8722;II)) may cause the rapid reductive dissolution of ferrihydrite and the release of associated nutrients and trace elements, thus influencing the biogeochemical cycling of trace elements and nutrients, particularly in redox dynamic environments.&lt;/p&gt;&lt;p&gt;Sulfidization of ferrihydrite occurs rapidly, whereby electron transfer between surface complexed sulfide and the ferrihydrite surface results in (partially) oxidized sulfur species and Fe(II). Depending on the S(-II):Fe molar ratios, secondary reactions then lead to mackinawite (FeS) or pyrite (FeS&lt;sub&gt;2&lt;/sub&gt;) precipitation. In nature, however, ferrihydrite is often found associated with natural organic matter (NOM). Because coprecipitation of ferrihydrite with NOM decreases particle size, alters the surface charge, and may block surface sorption sites, we speculated that kinetics and pathways of sulfidization of organic-associated ferrihydrite may differ from those of the pure mineral. Therefore, in this study, we followed iron mineral transformations and sulfur speciation during sulfidization of a pure ferrihydrite over one year and compared this to ferrihydrite coprecipitated with model organic ligands (polygalacturonic acid, galacturonic acid, and citric acid). Using a combination of solid- and aqueous phase Fe and S speciation techniques, we show that the impact of OM on ferrihydrite sulfidization kinetics and pathways varies with the chemical structure of the organic ligand, and that secondary reactions continue well past the initial rapid consumption of S(-II).&lt;/p&gt;

scholarly journals Impact of Graphite Materials on the Lifetime of NMC811/Graphite Pouch Cells: Part I. Material Properties, ARC Safety Tests, Gas Generation, and Room Temperature Cycling

2021 ◽  
Author(s):  
Ahmed Eldesoky ◽  
Michael Bauer ◽  
Saad Azam ◽  
Eniko zsoldos ◽  
Wentao Song ◽  
...  
Keyword(s):  
Room Temperature ◽  
Temperature Cycling ◽  
Cell Swelling ◽  
Bet Surface Area ◽  
Gas Generation ◽  
Capacity Retention ◽  
Surface Areas ◽  
Li Ion ◽  
Accessible Surface ◽  
The Impact

Abstract The impact of graphite materials on capacity retention in Li-ion cells is important to understand since Li inventory loss due to SEI formation, and cross-talk reactions between the positive and negative electrodes, are important cell failure mechanisms in Li-ion cells. Here, we investigate the impact of five graphite materials from reputable suppliers on the performance of NMC811/graphite cells. We show that natural graphites (NG) here have a mixture of 3R and 2H phases, while artificial graphites (AG) were 2H only. We find that there are differences between the N2 BET surface area and the electrochemically-accessible area where redox reactions can take place and it is the latter that is most important when optimizing graphite-containing cells. Part I of this 2-part series investigates physical and electrochemical differences between the graphite materials of interest here, as well as room temperature cycling to probe improvements in capacity retention. We demonstrate that advanced AG materials with small accessible surface areas can improve safety, 1st cycle efficiency (FCE) and long-term cycling. Part II of this work examines elevated temperature cycling, cell swelling, and makes lifetime predictions for the best NMC811/graphite cells.

scholarly journals Immobilization of lipase onto mesoporous silica KIT-6 and montmorillonite K10 for enzymatic hydrolysis of tributyrin

2016 ◽  
Vol 12 (1) ◽  
Author(s):  
Noorulsyahidaini Golbaha ◽  
Zainab Ramli ◽  
Salasiah Endud
Keyword(s):  
Mesoporous Silica ◽  
Incubation Temperature ◽  
Physical Adsorption ◽  
Immobilized Lipase ◽  
High Surface ◽  
Candida Rugosa ◽  
High Surface Area ◽  
Nitrogen Adsorption ◽  
Surface Areas ◽  
Hydrolysis Of

Mesoporous silica KIT-6 and montmorillonite (MMT) K-10 clay were prepared and used for immobilization of the enzyme, Candida rugosa lipases (CRL), aiming at their use as biocatalysts for the hydrolysis of tributyrin. Immobilization of the enzymes onto the supports was performed by physical adsorption using 0.1 M phosphate buffer solutions (pH 7) as the dispersion medium. The activity of the immobilized CRL for tributyrin hydrolysis was investigated at incubation temperature of 40 °C during 120 min and different concentration of the lipase solution for both the supports. Characterization by XRD showed that the long-ranged ordering in the KIT-6 and crystallinity of the MMT K-10 material were affected slightly by the lipase immobilization. This result gives an indication to the present of lipase-support interaction in the immobilized lipase system. Additionally, the results of FTIR spectroscopy verified the presence of silanols on the surfaces of MMT K-10 and KIT-6 materials, while the nitrogen adsorption data showed the resulting immobilized enzyme catalysts were rendered porous, with the KIT-6 giving higher specific surface areas and higher pore diameters in a narrow distribution of sizes ranging from 4 to 12 nm. The immobilization of CRL on KIT-6 and MMT K-10 through hydrogen bonding with the silanol groups, led to an increase in the hydrolysis activity compared to that of free lipase. However, the activity of KIT-6 immobilized CRL was higher than was observed on MMT K-10 immobilized CRL. Furthermore, lipase immobilized on mesoporous silica KIT-6 was shown to be recyclable up to 5 times in aqueous medium. The high surface area and the unique pore system of the mesoporous silica KIT-6, having may be the crucial factors that play an important role in retaining the enzyme in the support, and consequently, improving the lipase activity and stability. 

Synthesis and Characterization of Molecular Sieve SBA-15 and Catalysts Co/SBA-15 and Ru/Co/SBA-15

2014 ◽  
Vol 798-799 ◽  
pp. 100-105 ◽  
Author(s):  
Jocielys Jovelino Rodrigues ◽  
Liliane Andrade Lima ◽  
Gustavo Medeiros de Paula ◽  
Meiry Glaúcia Freire Rodrigues
Keyword(s):  
Molecular Sieve ◽  
High Surface ◽  
Nitrogen Adsorption ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Surface Areas ◽  
Bet Method ◽  
Superficial Area

A series of mesoporous materials have been synthesized in an acid medium, with various structures, such as SBA-15. These materials have many properties which make them potential catalysts. Among these we highlight their high surface areas and pore walls relatively thick, resulting in a greater hydrothermal stability. This work aims at the synthesis and characterization of molecular sieve SBA-15 with molar composition: 1.0 TEOS: 0.017 P123: 5.7 HCl: 193 H2O and Co/SBA-15 and catalysts for the reaction of Ru/Co/SBA-15 Fischer Tropsch process. The materials were characterized by the techniques of X-ray diffraction (XRD), chemical analysis by X-ray spectrometry, energy dispersive (EDX) and Nitrogen adsorption (BET method). X-ray diffraction showed that the calcined cobalt catalyst did not modify the structure of SBA-15 and that Co was present under the form of Co3O4 in the catalyst. The addition of cobalt in the SBA-15 decreased the specific superficial area of the molecular sieve.

scholarly journals Lignin Based Activated Carbon Using H3PO4 Activation

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2829
Author(s):  
Zhongzhi Yang ◽  
Roland Gleisner ◽  
Doreen H. Mann ◽  
Junming Xu ◽  
Jianchun Jiang ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Surface Area ◽  
Low Cost ◽  
High Surface ◽  
High Surface Area ◽  
Dye Adsorption ◽  
Nitrogen Adsorption ◽  
Bet Surface Area ◽  
Surface Areas ◽  
Adsorption Desorption

Activated carbon (AC) with a very high surface area of over 2000 m2/g was produced from low sulfur acid hydrotropic lignin (AHL) from poplar wood using H3PO4 at a moderate temperature of 450 °C (AHL-AC6). ACs with similar surface areas were also obtained under the same activation condition from commercial hardwood alkali lignin and lignosulfonate. Initial evaluation of AC performance was carried out using nitrogen adsorption-desorption and dye adsorption. AHL-AC6 exhibited the best specific surface area and dye adsorption performance. Furthermore, the adsorption results of congo red (CR) and methylene blue (MB) showed AHL-AC6 had greater adsorption capacity than those reported in literature. The dye adsorption data fit to the Langmuir model well. The fitting parameter suggests the adsorption is nearly strong and near irreversible, especially for MB. The present study for the first time provided a procedure for producing AC from lignin with Brunauer–Emmett–Teller (BET) surface area >2000 m2/g using low cost and low environmental impact H3PO4 at moderate temperatures.

scholarly journals Enhanced Surface Area and Reduced Pore Collapse of Methylated, Imine-Linked Covalent Organic Frameworks

Nanoscale ◽  
2021 ◽  
Author(s):  
Ellen Dautzenberg ◽  
Milena Lam ◽  
Guanna Li ◽  
Louis de Smet
Keyword(s):  
Energy Storage ◽  
Surface Area ◽  
Gas Separation ◽  
High Surface ◽  
Nanoporous Materials ◽  
Covalent Organic Frameworks ◽  
Pore Collapse ◽  
Surface Areas ◽  
Enhanced Surface

Covalent Organic Frameworks (COFs) are thermally and chemically stable, nanoporous materials with high surface areas, making them interesting for a large variety of applications including energy storage, gas separation, catalysis...

Sign in / Sign up

Export Citation Format

Share Document