scholarly journals Organic acid catalyzed carbon aerogels with freeze-drying

2017 ◽  
Vol 231 ◽  
pp. 012113
Author(s):  
Yuelong Xu ◽  
Meifang Yan ◽  
Zhenfa Liu
Keyword(s):  
Organic Acid ◽  
Freeze Drying ◽  
Carbon Aerogels ◽  
Acid Catalyzed

scholarly journals Environmentally Friendly and Multifunctional Shaddock Peel-Based Carbon Aerogel for Thermal-Insulation and Microwave Absorption

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Weihua Gu ◽  
Jiaqi Sheng ◽  
Qianqian Huang ◽  
Gehuan Wang ◽  
Jiabin Chen ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Thermal Insulation ◽  
Freeze Drying ◽  
Thermal Infrared ◽  
Carbon Aerogel ◽  
Carbon Aerogels ◽  
List Type ◽  
Drying Method ◽  
Cross Sectional ◽  
Compression Resistance

Highlights The eco-friendly shaddock peel-derived carbon aerogels were prepared by a freeze-drying method. Multiple functions such as thermal insulation, compression resistance and microwave absorption can be integrated into one material-carbon aerogel. Novel computer simulation technology strategy was selected to simulate significant radar cross-sectional reduction values under real far field condition. . Abstract Eco-friendly electromagnetic wave absorbing materials with excellent thermal infrared stealth property, heat-insulating ability and compression resistance are highly attractive in practical applications. Meeting the aforesaid requirements simultaneously is a formidable challenge. Herein, ultra-light carbon aerogels were fabricated via fresh shaddock peel by facile freeze-drying method and calcination process, forming porous network architecture. With the heating platform temperature of 70 °C, the upper surface temperatures of the as-prepared carbon aerogel present a slow upward trend. The color of the sample surface in thermal infrared images is similar to that of the surroundings. With the maximum compressive stress of 2.435 kPa, the carbon aerogels can provide favorable endurance. The shaddock peel-based carbon aerogels possess the minimum reflection loss value (RLmin) of − 29.50 dB in X band. Meanwhile, the effective absorption bandwidth covers 5.80 GHz at a relatively thin thickness of only 1.7 mm. With the detection theta of 0°, the maximum radar cross-sectional (RCS) reduction values of 16.28 dB m2 can be achieved. Theoretical simulations of RCS have aroused extensive interest owing to their ingenious design and time-saving feature. This work paves the way for preparing multi-functional microwave absorbers derived from biomass raw materials under the guidance of RCS simulations.

Trash into Treasure: stiff, thermally insulating and highly conductive carbon aerogels from leather wastes for high-performance electromagnetic interference shielding

2021 ◽  
Author(s):  
Bin Yuan ◽  
Shuangxin Lai ◽  
Jianjun Li ◽  
Li Li ◽  
Shibing Bai
Keyword(s):  
Electromagnetic Interference ◽  
High Performance ◽  
Freeze Drying ◽  
Carbon Aerogels ◽  
Urgent Problem ◽  
Electromagnetic Interference Shielding ◽  
Leather Wastes

Humans have used animal leather materials for thousands of years. Nowadays, the disposal of Cr-containing leather wastes (LWs) has become an urgent problem. Herein, by adopting simultaneously conventional freeze-drying and...

scholarly journals A sustainable strategy for production and functionalization of nanocelluloses

2019 ◽  
Vol 91 (5) ◽  
pp. 865-874 ◽  
Author(s):  
Armando Córdova ◽  
Samson Afewerki ◽  
Rana Alimohammadzadeh ◽  
Italo Sanhueza ◽  
Cheuk-Wai Tai ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Metal Ions ◽  
Organic Acid ◽  
Surface Functionalization ◽  
Fluorescent Probes ◽  
Organic Molecules ◽  
Cross Coupling ◽  
Palladium Nanoparticle ◽  
Acid Catalyzed ◽  
Nanoparticle Catalyst

Abstract A sustainable strategy for the neat production and surface functionalization of nanocellulose from wood pulp is disclosed. It is based on the combination of organocatalysis and click chemistry (“organoclick” chemistry) and starts with nanocellulose production by organic acid catalyzed hydrolysis and esterification of the pulp under neat conditions followed by homogenization. This nanocellulose fabrication route is scalable, reduces energy consumption and the organic acid can be efficiently recycled. Next, the surface is catalytically engineered by “organoclick” chemistry, which allows for selective and versatile attachment of different organic molecules (e.g. fluorescent probes, catalyst and pharmaceuticals). It also enables binding of metal ions and nanoparticles. This was exemplified by the fabrication of a heterogeneous nanocellulose-palladium nanoparticle catalyst, which is used for Suzuki cross-coupling transformations in water. The disclosed surface functionalization methodology is broad in scope and applicable to different nanocelluloses and cellulose based materials as well.

Hydrogen Generation From Acetic Acid Catalyzed Magnesium Hydride Using an On-Demand Hydrogen Reactor

2016 ◽  
Author(s):  
Tien-Chien Jen ◽  
Joshua Adeniran ◽  
Esther Akinlabi ◽  
Chung-Hsing Chao ◽  
Yen-Hsi Ho ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Organic Acid ◽  
Hydrogen Generation ◽  
Magnesium Hydride ◽  
Hydrolysis Reaction ◽  
Hydrogen Yield ◽  
Acetic Acid Concentration ◽  
External Temperature ◽  
On Demand ◽  
Acid Catalyzed

This study reports an acetic acid catalyzed hydrolysis reaction for hydrogen generation from magnesium hydride (MgH2) using an on-demand hydrogen reactor. Acetic acid, a weak and benign organic acid, has been reported as a single catalyst in hydrolysis reaction for hydrogen generation using other substrates, but this is the first study where acetic acid has been employed as a catalyst in a magnesium hydride hydrolysis reaction for hydrogen generation. In this study, the effects of MgH2 weight, acetic acid concentration and external temperature on hydrogen generation from MgH2 were examined. The results of the hydrolysis reaction indicated that the weight of MgH2 was the major factor influencing hydrogen generation, followed by the concentration of acetic acid while the effect of external temperature was insignificant. Similarly, hydrogen yield was proportional to the weight of MgH2 with a reported maximum hydrogen yield at each weight been: 0.4g (∼ 0.07 L); 0.8 g (∼ 0.125 L) and 1.2 g (∼1.285 L). The successful use of acetic acid in the study reinforced the versatility of the on-demand hydrogen reactor and as a scalable technology for hydrogen generation.

scholarly journals Organic Acid-Catalyzed Subcritical Water Hydrolysis of Immature Citrus unshiu Pomace

Foods ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 18
Author(s):  
Sang-Bin Lim
Keyword(s):  
Citric Acid ◽  
Organic Acid ◽  
Acid Concentration ◽  
Subcritical Water ◽  
Biological Activities ◽  
Citrus Unshiu ◽  
Citric Acid Concentration ◽  
Acid Catalyzed ◽  
Inhibitory Activities ◽  
Hydrolysis Of

Immature Citrus unshiu pomace (ICUP) was hydrolyzed under organic acid-catalyzed, subcritical water (SW) conditions to produce flavonoid monoglucosides (hesperetin-7-O-glycoside and prunin) and aglycons (hesperetin and naringenin) with high biological activities. The results of single-factor experiments showed that with 8 h of hydrolysis and an increasing citric acid concentration, the yield of flavonoid monoglucosides (hesperetin-7-O-glycoside and prunin) increased from 0 to 7% citric acid. Afterward, the hesperetin-7-O-glycoside yield remained constant (from 7 to 19% citric acid) while the pruning yield decreased with 19% of citric acid, whereas the aglycon yield increased continuously. In response surface methodology analysis, a citric acid concentration and hydrolysis duration of 13.34% and 7.94 h were predicted to produce the highest monoglucoside yield of 15.41 mg/g, while 18.48% citric acid and a 9.65 h hydrolysis duration produced the highest aglycon yield of 10.00 mg/g. The inhibitory activities of the SW hydrolysates against pancreatic lipase (PL) and xanthine oxidase (XO) were greatly affected by citric acid concentration and hydrolysis duration, respectively. PL and α-glucosidase inhibition rates of 88.2% and 62.7%, respectively, were achieved with 18.48% citric acid and an 8 h hydrolysis duration, compared to 72.8% for XO with 16% citric acid and 12 h of hydrolysis. This study confirms the potential of citric acid-catalyzed SW hydrolysis of ICUP for producing flavonoid monoglucosides and aglycons with enhanced enzyme inhibitory activities.

scholarly journals Fabrication Of Carbon Aerogels From Coir For Oil Adsorption

2022 ◽  
Vol 964 (1) ◽  
pp. 012033
Author(s):  
Hieu M Nguyen ◽  
Khoi A Tran ◽  
Tram T N Nguyen ◽  
Nga N H Do ◽  
Kien A Le ◽  
...  
Keyword(s):  
Freeze Drying ◽  
Oil Spills ◽  
Sol Gel ◽  
Urea Solution ◽  
Carbon Aerogels ◽  
Low Density ◽  
High Porosity ◽  
Motor Oil ◽  
Sol Gel Process ◽  
Oil Adsorption

Abstract Coir, known as coconut fibers, are an abundant cellulosic source in Vietnam, which are mostly discarded when copra and coconut water are taken, causing environmental pollution and waste of potential biomass. In this research, carbon aerogels from chemically pretreated coir were successfully synthesized via simple sol-gel process with NaOH-urea solution, economical freeze-drying, and carbonization. The samples, including pretreated coir, coir aerogels, and carbon aerogels, are characterized using FTIR spectroscopy, SEM, XRD spectroscopy, and TGA. The carbon aerogels exhibit low density (0.034–0.047 g/cm3), high porosity (97.63–98.32 %), and comparable motor oil sorption capacity (22.71 g/g). The properties of carbon aerogels are compared with those of coir aerogels, indicating such better values than those of coir aerogels. Coir-derived carbon aerogels is a potential replacement for the hydrophobically-coated cellulose aerogels in term of treating oil spills.

Kinetics and Mechanism of Acid-Catalyzed Decomposition of 1,3-Bis(4-methylphenyl)triazene in Hexane-Organic Acid Medium

1996 ◽  
Vol 61 (3) ◽  
pp. 355-363 ◽  
Author(s):  
Miroslav Ludwig ◽  
Miriam Kabíčková
Keyword(s):  
Kinetic Model ◽  
Organic Acid ◽  
Acid Medium ◽  
Rate Constant ◽  
Fourth Order ◽  
Kinetics And Mechanism ◽  
Acid Catalyzed ◽  
Kinetics Of

The kinetics of acid-catalyzed decomposition of 1,3-bis(4-methylphenyl)triazene have been studied in mixtures of hexane and organic acid of various ratios using acetic, isovaleric, and pivalic acids as the catalysts. In all the cases, a monotonously increasing dependence of the observed rate constant upon mol fraction of the acid has been found. The results obtained are discussed with the help of the classic third- and fourth-order functions by Margules and the respective kinetic model. The main catalyzing particle appears to be the dimer of the respective acid, the reaction probably going via a complex formed by two molecules of acid and one molecule of the triazene.

Salt-assisted organic-acid-catalyzed depolymerization of cellulose

2010 ◽  
Vol 12 (10) ◽  
pp. 1844 ◽  
Author(s):  
Thorsten vom Stein ◽  
Philipp Grande ◽  
Fabrizio Sibilla ◽  
Ulrich Commandeur ◽  
Rainer Fischer ◽  
...  
Keyword(s):  
Organic Acid ◽  
Acid Catalyzed
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