scholarly journals Improvement of Solvent Exchange for Supercritical Dried Aerogels

2021 ◽  
Vol 8 ◽  
Author(s):  
Marina Schwan ◽  
Sarah Nefzger ◽  
Behdad Zoghi ◽  
Christina Oligschleger ◽  
Barbara Milow
Keyword(s):  
Carbon Dioxide ◽  
Solvent Extraction ◽  
Process Parameters ◽  
Supercritical Drying ◽  
Peristaltic Pump ◽  
Solvent Exchange ◽  
Karl Fischer Titration ◽  
Surface Areas ◽  
Organic Aerogels ◽  
Suitable System

The solvent exchange as one of the most important steps during the manufacturing process of organic aerogels was investigated. This step is crucial as a preparatory step for the supercritical drying, since the pore solvent must be soluble in supercritical carbon dioxide to enable solvent extraction. The development and subsequent optimization of a suitable system with a peristaltic pump for automatic solvent exchange proved to be a suitable approach. In addition, the influence of zeolites on the acceleration of the process was found to be beneficial. To investigate the process, the water content in acetone was determined at different times using Karl Fischer titration. The shrinkage, densities, as well as the surface areas of the aerogels were analyzed. Based on these, the influence of various process parameters on the final structure of the obtained aerogels was investigated and evaluated. Modeling on diffusion in porous materials completes this study.

scholarly journals Investigation of Aerogel Production Processes: Solvent Exchange under High Pressure Combined with Supercritical Drying in One Apparatus

Gels ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 4
Author(s):  
Artem Lebedev ◽  
Ekaterina Suslova ◽  
Aleksander Troyankin ◽  
Daria Lovskaya
Keyword(s):  
Carbon Dioxide ◽  
Phase Diagram ◽  
Experimental Study ◽  
Supercritical Drying ◽  
Solvent Exchange ◽  
Efficient Technology ◽  
Production Processes ◽  
Improve Production Technology ◽  
Homogeneous Regions ◽  
Organic Aerogels

This work aims to contribute to the theoretical and experimental research of supercritical processes for intensification and combination in one apparatus. Investigation is carried out to improve production technology of organic alginate aerogels. It is proposed within the investigation to carry out the solvent exchange stage, an important stage of organic aerogels production, under pressure in a carbon dioxide medium in the same apparatus used for supercritical drying. The phase behavior in the system “carbon dioxide–water–2-propanol”, which arises during such a solvent exchange stage, is studied theoretically. An experimental study of the process of step-by-step solvent exchange under pressure was carried out through multiphase and homogeneous regions of the phase diagram of such a system. As a result, new highly efficient technology for the production of organic aerogels was proposed, which can be implemented by combining the two main stages of the process.

Cellulose aerogels: Highly porous, ultra-lightweight materials

Holzforschung ◽  
2008 ◽  
Vol 62 (2) ◽  
pp. 129-135 ◽  
Author(s):  
Falk Liebner ◽  
Antje Potthast ◽  
Thomas Rosenau ◽  
Emmerich Haimer ◽  
Martin Wendland
Keyword(s):  
Carbon Dioxide ◽  
Solid State ◽  
Solution Structure ◽  
Supercritical Drying ◽  
Regenerated Cellulose ◽  
Solvent Exchange ◽  
New Materials ◽  
Surface Areas ◽  
Degradation Reactions ◽  
Highly Porous

Abstract Cellulosic aerogels are intriguing new materials produced by supercritical drying of regenerated cellulose obtained by solvent exchange of solid Lyocell moldings. From N-methylmorpholine-N-oxide (NMMO) solutions with cellulose contents between 1 and 12%, dimensionally stable cellulose bodies are produced, in which the solution structure of the cellulose is largely preserved and transferred into the solid state, the material having densities down to 0.05 g cm-3 and surface areas of up to 280 m2 g-1. In this study, several aspects of cellulosic aerogel production are communicated: the stabilization of the cellulose solutions against degradation reactions by agents suitable for later extraction and drying, a reliable extraction and drying procedure by supercritical carbon dioxide, the advantages of DMSO/NMMO in this procedure as a solvent/non-solvent pair, and some data on the physical properties of the materials.

scholarly journals Ultralight-Weight Cellulose Aerogels from NBnMO-Stabilized Lyocell Dopes

2007 ◽  
Vol 2007 ◽  
pp. 1-4 ◽  
Author(s):  
Falk Liebner ◽  
Antje Potthast ◽  
Thomas Rosenau ◽  
Emmerich Haimer ◽  
Martin Wendland
Keyword(s):  
Carbon Dioxide ◽  
Solid State ◽  
Solution Structure ◽  
Supercritical Drying ◽  
Regenerated Cellulose ◽  
Cellulose Content ◽  
Solvent Exchange ◽  
New Materials ◽  
Specific Density ◽  
Regeneration Procedure

Cellulose aerogels are intriguing new materials produced by supercritical drying of regenerated cellulose obtained by solvent exchange of solid Lyocell moldings. FromN-methylmorpholine-N-oxide solutions with cellulose contents between 1 and 12%, dimensionally stable cellulose bodies are produced, in which the solution structure of the cellulose is largely preserved and transferred into the solid state. The specific density and surface of the obtained aerogels range from 0.05 to 0.26 g/cm3and from 172 to 284m2/g, respectively, depending on the cellulose content of the Lyocell dopes and regeneration procedure. A reliable extraction and drying procedure using supercritical carbon dioxide, the advantageous use of NBnMO as stabilizer for the Lyocell dopes, and selected physical properties of the materials is communicated.

scholarly journals Gellan aerogel production applying supercritical technology

2019 ◽  
Author(s):  
Gabriela Fujita de Freitas ◽  
Julian Martinez ◽  
Juliane Viganó
Keyword(s):  
Carbon Dioxide ◽  
High Surface ◽  
High Surface Area ◽  
Supercritical Drying ◽  
Gelling Agent ◽  
Diffusion Method ◽  
Low Density ◽  
Solvent Exchange ◽  
Hydrogel Formulation ◽  
Pre Treatment

Aerogels are materials with an open porous, low density and high surface area, which make them an interesting material to carry target compounds. The proposal of this work was to produce gellan aerogels and to study the effect of the diffusion method and internal setting method, the temperature of the gellan pre-treatment, and the addition of inulin on the aerogel shrinkage during the process. The aerogels were produced through hydrogel formulation, solvent exchange to obtain alcogel, and supercritical drying with carbon dioxide. The addition of inulin has reduced the shrinkage, but gelling methods to avoid the inulin loss must be studied, as the oil containing the gelling agent.

scholarly journals Extraction of Triterpenic Acids and Phytosterols from Apple Pomace with Supercritical Carbon Dioxide: Impact of Process Parameters, Modelling of Kinetics, and Scaling-Up Study

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 2790 ◽  
Author(s):  
Łukasz Woźniak ◽  
Anna Szakiel ◽  
Cezary Pączkowski ◽  
Krystian Marszałek ◽  
Sylwia Skąpska ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Process Parameters ◽  
Binary Systems ◽  
Cell Model ◽  
Intact Cell ◽  
Selective Extraction ◽  
Apple Pomace ◽  
Extraction Curve ◽  
Hydrophobic Compounds ◽  
The Impact

Apple pomace, a byproduct of juice production, is a rich source of bioactive compounds and nutrients. Supercritical fluid extraction was proposed as a method for a fast and selective extraction of hydrophobic compounds with a pharmaceutical potential from this matrix. Chromatographic analysis showed that the pomace contained significant amounts of such substances, the most abundant of them were ursolic acid, oleanolic acid, and β-sitosterol. The solubility was chosen as a primary factor for a selection of the extraction conditions; the best results were acquired for a temperature of 80 °C and a pressure of 30 MPa. The equation proposed by Chrastil was applied for the description of the impact of the process parameters on the solubility of the analytes; the obtained values of coefficients of determination were satisfactory, despite the fact that the equation was developed for binary systems. The extraction curves obtained during the experiments were used for the description of the process kinetics using the Broken plus Intact Cell model. The impact of the temperature, pressure, and flow rate of carbon dioxide on the mass transfer phenomena was investigated. The data obtained allowed the prediction of the extraction curve for the process conducted on the larger scale.

A novel approach to alginate aerogels: carbon dioxide induced gelation

RSC Advances ◽  
2015 ◽  
Vol 5 (11) ◽  
pp. 7812-7818 ◽  
Author(s):  
P. Gurikov ◽  
S. P. Raman ◽  
D. Weinrich ◽  
M. Fricke ◽  
I. Smirnova
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Drying ◽  
Novel Approach

A novel process, carbon dioxide induced gelation, opens new pathways towards hydrogels and can be coupled with supercritical drying to produce aerogels.

Phase behavior and process parameters effects on the characteristics of precipitated theophylline using carbon dioxide as antisolvent

2008 ◽  
Vol 44 (1) ◽  
pp. 8-20 ◽  
Author(s):  
Elton Franceschi ◽  
Marcos H. Kunita ◽  
Marcus V. Tres ◽  
Adley F. Rubira ◽  
Edvani C. Muniz ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Phase Behavior ◽  
Process Parameters
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