ARTICLE | doi:10.20944/preprints202206.0055.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Sulfonated silica catalyst (SiO2-SO3H); methyl salicylate; green chemistry; methylating agent; deacetylation (acyl nucleophilic substitution); solid acid catalyst
Online: 6 June 2022 (03:45:09 CEST)
SiO2-SO3H, with a surface area of 115 m2/g, pore volume of 0.38 cm3g-1 and 1.32 mmol H+/g, was used as a 20% w/w catalyst for the preparation of methyl salicylate (Wintergreen oil or MS) from acetylsalicylic acid (ASA). A 94% conversion was achieved in a microwave reactor during 40.0 minutes at 120 oC in MeOH. The resulting crude product was purified by flash chromatography. The catalyst could be re-used three times.
ARTICLE | doi:10.20944/preprints202304.0293.v1
Subject: Chemistry And Materials Science, Applied Chemistry Keywords: Environment friendly processes; Bayer residue; waste management; bauxite; contaminants; quality control; fatty acid methyl ester
Online: 13 April 2023 (03:42:31 CEST)
Red mud (RM) is a residue obtained from the production of alumina. It contains a high concentration of metal oxides and waste concentrated sodium hydroxide solution (pH = 13). To increase the value of RM, an environmentally friendly process of transesterification using waste cooking oil (WCO), MeOH and concentrated sodium hydroxide solution (CSHS) from aluminum production was proposed. Triglycerides of WCO reacted with MeOH at 60 oC to yield mixtures of fatty acid methyl esters (FAMEs) in the presence of 2.03% (w/w) CSHS/WCO using the CSHS (0.204 mol L-1, predetermined by potentiometric titration) from aluminum production by the Bayer process or with the addition of 0.68% (w/w) fabric softener (3% w/w cetyltrimethylammonium chloride in solution) as a phase transfer (PTA) agent. The addition of PTA to the catalyst resulted in a better yield of the products (greater than 98% yield). A simplified mechanism is presented to account for the experimental results.
ARTICLE | doi:10.20944/preprints202305.0377.v1
Subject: Chemistry And Materials Science, Applied Chemistry Keywords: Environmentally friendly processes; Bayer residue; waste management; basic catalyst, contaminants, red mud, fatty acid methyl ester
Online: 6 May 2023 (05:00:47 CEST)
Red mud (RM) is composed of a waste alkaline solution (pH = 13.3) obtained from the production of alumina. It contains high concentrations of soluble hematite (Fe2O3), goetite (FeOOH), gibisite [Al(OH)3], a boemite (AlOOH), anatase (Tetragonal - TiO2), rutile (Ditetragonal dipyramidal - TiO2), hydrogarnets [Ca3Al2(SiO4)3−x(OH)4x], and perovskite (CaTiO3). It was shown to be an excellent catalytic mixture for biodiesel production. To demonstrate the value of RM, an environmentally friendly process of transesterification in aqueous medium using waste cooking oil (WCO), MeOH and waste alkaline solution (WAS) obtained from aluminum production was proposed. Triglycerides of WCO reacted with MeOH at 60 oC to yield mixtures of fatty acid methyl esters (FAMEs) in the presence of 0.019% (w/w) WAS/WCO using the WAS (0.204 mol L-1, predetermined by potentiometric titration) from aluminum production by the Bayer process. The use of the new catalyst (WAS) resulted in a high yield of the products (greater than 99% yield).
ARTICLE | doi:10.20944/preprints202303.0537.v1
Subject: Business, Economics And Management, Accounting And Taxation Keywords: metals oxides; surface hydrophilicity; alcoholic beverage; contaminants; quality control; mesoporous materials
Online: 31 March 2023 (03:13:00 CEST)
The presence of copper in distilled sugar cane spirits, especially cachaça produced in alembics, has impeded the marketing of this product. Red mud (RM) is a residue obtained from alumina production. It contains a high concentration of metal oxides and is very alkaline. The RM was dried at 100 oC and sifted through a 150-micron sieve. The sample was characterized by B.E.T. nitrogen adsorption, scanning electron microscopy-energy-dispersive X-ray (SEM-EDX) and Atomic Absorption Spectrometry (A.A.S.). The textural parameters indicate that the total surface area (S.T.) was 21.9 m2g-1, and the total volume pore (V.T.) was 0.09 cm3g-1. The RM (1 g) was stirred for two hours with a 1.0 L cachaça sample containing 9.39 mg of copper L-1 and filtered under atmospheric pressure. The concentration of copper ions detected in the filtrate was 0.00 mg L-1. No copper ions were retained when the cachaça was filtered through the RM under high pressure without stirring prior to filtration.
ARTICLE | doi:10.20944/preprints202201.0013.v1
Subject: Chemistry And Materials Science, Applied Chemistry Keywords: hydrophilic sulfonated silica catalyst; Aliquat 336; tetrabutylammonium tetrafluoroborate; transesterification; fatty acid methyl esters, DMSO.
Online: 4 January 2022 (15:24:55 CET)
Triglycerides of waste cooking oil reacted with methanol in refluxing toluene to yield mixtures of diglycerides, monoglycerides and fatty acid methyl esters (FAMEs) in the presence of 20% (w/w) catalyst/oil using the hydrophilic sulfonated silica (SiO2-SO3H) catalyst alone or with the addition of 10% (w/w) co-catalyst/oil [(Bun4N)](BF4) or Aliquat 336]. The addition of the ammonium salts to the catalyst lead to a decrease in the amounts of diglycerides in the products, but the concentrations of monoglycerides increased. Mixtures of [(Bun4N)](BF4)/catalyst were superior to catalyst alone or Aliquat 336/catalyst for promoting the production of mixtures with high concentrations of FAMEs. The same experiments were repeated using DMSO as the solvent. The use of the more polar solvent resulted in excellent conversion of the triglycerides to FAME esters with all three-catalyst media. A simplified mechanism is presented to account for the experimental results.
ARTICLE | doi:10.20944/preprints202305.0545.v1
Subject: Chemistry And Materials Science, Applied Chemistry Keywords: Wintergreen oil; niobium pentachloride; sequential reactions; antimicrobial activity; cytotoxicity; S. aureus
Online: 8 May 2023 (14:51:06 CEST)
Methyl Salicylate (MS), the principal constituent of Wintergreen oil (WO) was obtained from acetyl salicylic acid (ASA) by sequential transesterification-esterification reaction promoted by NbCl5for the first time. The reagents were added simultaneously, and the reaction process involved the transesterification and esterification reactions, which were accompanied by thin layer chromatography and gas chromatography. The conversion rate via GC was 100%, and the MS yield was 94%. A cytotoxicity of 50% and 64% for cultured S. aureus and metastatic melanoma cells, respectively, was observed for a concentration of 0.6 mg/mL, whereas no cytotoxicity for non-tumor cells was observed for this concentration, and it is considered to be the optimum concentration.