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1.
ChemSusChem ; 13(4): 707-714, 2020 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-31912979

RESUMO

Biomass-derived surfactants with very good surface tension and critical micellar concentration properties were obtained by conversion of methyl levulinate into methyl 4-alkoxypentanoates through reductive etherification with aliphatic alcohols. Among different bifunctional acid/metal catalysts best results were obtained with Pd on carbon bearing acid sites. The reaction occurred through the formation of an enol ether intermediate followed by hydrogenation. Pd in high-density planes was the active hydrogenation species, and an optimum crystal size was found to be approximately 10 nm. The reductive etherification with aliphatic alcohols was extended to other aliphatic and cyclic ketones and aldehydes obtained from biomass, and excellent results were obtained on supported Pd catalysts with the reaction route and experimental conditions described in this work.

2.
ChemSusChem ; 13(7): 1864-1875, 2020 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-31944622

RESUMO

Biobased plasticizers, as substitutes for phthalates, have been synthesized from 5-hydroxymethylfurfural (HMF) and carboxylic acids (or esters) through a chemoenzymatic cascade process that involves as its first step the reduction of 5-hydroxymethylfurfural into 2,5-bis(hydroxymethyl)furan (BHMF), followed by the esterification of BHMF with carboxylic acids (or esters) by using a supported lipase (Novozym 435). The reduction of HMF into BHMF is performed by using monodisperse metallic Co nanoparticles with a thin carbon shell (Co@C) with high activity and selectivity. After optimization of reaction conditions (temperature, hydrogen pressure, and solvent), it is possible to achieve 97 % conversion of HMF with 99 % selectivity to BHMF after 2 h reaction time. The reduction of HMF and esterification of BHMF using carboxylic acids or vinyl esters as acyl donors by lipase are optimized separately in batch and in fixed-bed continuous reactors. The coupling of two flow reactors (for reduction and subsequent esterification) working under optimized reaction conditions affords the diesters of BHMF in roughly 90 % yield with no loss of activity during 60 h of operation.

3.
ChemSusChem ; 11(17): 2870-2880, 2018 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-29975011

RESUMO

A new type of biomass-derived non-ionic surfactants has been obtained by reacting hydroxymethylfurfural (HMF), glycerol, and fatty alcohols. For instance, 5-(octyloxymethyl)furfural glyceryl acetal can be obtained in a one-pot process by etherification of HMF with fatty alcohols followed by acetalization with glycerol. For a successful solid catalyst, acidity and polarity have to be optimized to improve conversion, selectivity, and catalyst deactivation owing to the different adsorption characteristics of the reactant molecules. Accordingly, Beta zeolite with a high Si/Al ratio and practically free of connectivity defects showed good results when dealing with these biomass derivatives, which include a highly polar reactant such as glycerol. The scope of the reaction is good and a variety of new stable surfactant molecules can be obtained that present hydrophilic-lipophilic balance (HLB ) values in the range 4.9 to 6.6, which are of interest for water in oil emulsions.

4.
ChemSusChem ; 7(1): 210-20, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24106062

RESUMO

A new class of biodegradable anionic surfactants with structures based on 5-alkoxymethylfuroate was prepared starting from 5-hydroxymethylfurfural (HMF), through a one-pot-two-steps process which involves the selective etherification of HMF with fatty alcohols using heterogeneous solid acid, followed by a highly selective oxidation of the formyl group with a gold catalyst. The etherification step was optimized using aluminosilicates as acid catalysts with different pore topologies (H-Beta, HY, Mordenite, ZSM-5, ITQ-2, and MCM-41), different active sites (Bronsted or Lewis) and different adsorption properties. It was shown that highly hydrophobic defect-free H-Beta zeolites with Si/Al ratios higher than 25 are excellent acid catalysts to perform the selective etherification of HMF with fatty alcohols, avoiding the competitive self-etherification of HMF. Moreover, the 5-alkoxymethylfurfural derivatives obtained can be selectively oxidized to the corresponding furoic salts in excellent yield using Au/CeO2 as catalyst and air as oxidant, at moderated temperatures. Both H-Beta zeolite and Au/CeO2 could be reused several times without loss of activity.


Assuntos
Silicatos de Alumínio/química , Éteres/química , Furaldeído/análogos & derivados , Dióxido de Silício/química , Tensoativos/química , Biomassa , Catálise , Cério/química , Furaldeído/química , Ouro/química
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