Search results for "SUPERCRITICAL CARBON DIOXIDE"

CO2 as a C1-Building Block for Dialkyl Carbonate Synthesis

2002

Carbon dioxide, one of the major man-made greenhouse gas, is a renewable resource of carbon which can be viewed as a C1 synthon to build valuable chemicals. The development of new applications is of major interest considering CO2 conversion and environmentally friendly reactions. As chemical catalysis offers interesting options, we are studying the molecular design of catalysts for the formation of dialkyl carbonates from alcohols and CO2. This paper reports results on the mechanistic approach for dialkyl carbonate formation with alkoxybutyl tin(IV) compounds. The insertion of CO2 into Sn-OR bonds (R = Me, 1Pr) occurs at atmospheric pressure and room temperature leading to alkylcarbonato ti…

ChemInform Abstract: Baeyer-Villiger Oxidation of Ketones with a Silica-Supported Peracid in Supercritical Carbon Dioxide under Flow Conditions.

2009

[2-Percarboxyethyl]-functionalized silica reacts with ketones in supercritical carbon dioxide at 250 bar and 40 °C under flow conditions to yield the corresponding esters and lactones. The solid reagent can be easily recycled through treatment with 70% hydrogen peroxide in the presence of an acid at 0 °C. This procedure not only simplifies the isolation of the reaction products, but has the advantage of using only water and carbon dioxide as solvents under mild conditions.

Dispersion polymerization of vinyl monomers in supercritical carbon dioxide in the presence of drug molecules: A one-pot route for the preparation of…

2008

Eumelanin Coating of Silica Aerogel by Supercritical Carbon Dioxide Deposition of a 5,6-Dihydroxyindole Thin Film

2018

Eumelanin integration in silica aerogel (SA) was achieved via supercritical adsorption of 5,6-dyhydroxyindole (DHI) from CO2. Notably, after the supercritical treatment, DHI evolved towards spontaneous polymerization, which resulted in uniform pigment development over the SA. The new material was characterized for its morphological and physicochemical properties, disclosing the formation of a eumelanin-like coating, as confirmed by UV&ndash

Modification of Poly(vinilydenefluoride) Porous Membranes by Grafting of Acrylic Acid Assisted by Supercritical Carbon Dioxide

2010

Aim of this work is to study the preparation of pH sensitive membranes for biomedical applications via thermally induced graft polymerization of acrylic acid (AA) on poly(vinilydenefluoride) (PVDF) assisted by supercritical carbon dioxide (scCO2). Using scCO2 as a solvent and swelling agent, the monomer and the initiator (benzoyl peroxide) could diffuse faster into the polymer matrix, distribute more uniformly and allows a better control of the final molecular architecture promoting grafting reactions rather than chain degradation processes. As polymer matrixes we are using commercial hydrophobic porous PVDF membranes. Grafted polymers are characterized by Fourier transform infrared spectro…

In Vitro and In Vivo Regulation of SRD5A mRNA Expression of Supercritical Carbon Dioxide Extract from Asparagus racemosus Willd. Root as Anti-Sebum a…

2022

Oily skin from overactive sebaceous glands affects self-confidence and personality. There is report of an association between steroid 5-alpha reductase gene (SRD5A) expression and facial sebum production. There is no study of the effect of Asparagus racemosus Willd. root extract on the regulation of SRD5A mRNA expression and anti-sebum efficacy. This study extracted A. racemosus using the supercritical carbon dioxide fluid technique with ethanol and investigated its biological compounds and activities. The A. racemosus root extract had a high content of polyphenolic compounds, including quercetin, naringenin, and p-coumaric acid, and DPPH scavenging activity comparable to that of the standa…

Modification of PVDF nanoparticles by controlled free radical graft copolymerization in supercritical carbon dioxide

2014

PVDF (polyvinylidenefluoride) membranes are widely used in microfiltration (MF) and ultrafiltration (UF) due to their excellent processability, chemical resistance, well-controlled porosity, and good thermal properties [1]. Moreover this polymer is also frequently adopted in bio-medical devices owing to its good biocompatibility [2]. On the other hand, the use of PVDF membranes in biomedical applications is limited to some extent by the hydrophobicity of their exposed area, which mainly arises from the nature of the pore surface. Prompted by these considerations in the present work we have studied the modification of PVDF nanoparticles with hydroxyethylmethacrylate (HEMA) thus obtaining a m…

Sterilization of three-dimensional tissue engineering scaffolds by supercritical carbon dioxide

2014

Medical devices, implants or patient-care equipment that will come into intimate contact with a patient must be effectively decontaminated to prevent infection or disease transmission. Non-sterile devices have significant ramifications for patient morbidity and mortality and two processes must be undertaken in order to make an item acceptable for use or implantation: cleaning and disinfection (or sterilization) [1]. Sterilization is the destruction of living organisms, and must be done without damaging the material surface and without compromising the bulk material strength or biocompatibility of implantable device. Common sterilization processes include steam autoclaving, gamma irradiation…

A one-pot method to enhance dissolution rate of low solubility drug molecules using dispersion polymerization in supercritical carbon dioxide

2009

Preparation of pH sensitive poly(vinilydenefluoride) porous membranes by grafting of acrylic acid assisted by supercritical carbon dioxide

2010

Aim of this work is to study the preparation of pH sensitive membranes for biomedical applications via thermal induced graft polymerization of acrylic acid (AA) on poly(vinilydenefluoride) (PVDF) assisted by supercritical carbon dioxide (scCO2). Using scCO2 as a solvent and swelling agent, the monomer and initiator (benzoyl peroxide) could diffuse faster and distribute more uniformly into the polymer matrix. A better control of the final molecular architecture should be achieved because bimolecular grafting reactions are accelerated with respect to chain degradation processes. Commercial hydrophobic PVDF porous matrixes were selected as model membranes. Grafted polymers were characterized b…