First Attempt of Glycidol-to-Monoalkyl Glyceryl Ethers Conversion by Acid Heterogeneous Catalysis: Synthesis and Simplified Sustainability Assessment.

The selective preparation of monoalkylglyceryl ethers (MAGEs) is a task for researchers owing to their broad range of applications. In this work, green feedstocks such as glycidol and alcohols were used to prepare MAGEs under mild reaction conditions (80 °C, 3 h, 0.5 mol % catalyst) in the presence of acid heterogeneous catalysts. Nafion shows the best performances in terms of conversion and selectivity to MAGES and also high stability. A comparison of the environmental performances with the most consolidated pathway from glycerol has shown that the usage of glycidol (recovered as a value-added product from Epicerol process) and Nafion leads to a lower impact on ecosystems. In addition, results achieved from a simplified socio-economic analysis show that the innovative route here proposed has potential (at the laboratory scale) of enhancing potential gains and of reducing the social implications resulting from externalities associated with environmental impacts (e.g., CO2 equivalents).

Heterogeneous photo-Fenton decolorization of Orange II over Al-pillared Fe-smectite: response surface approach, degradation pathway, and toxicity evaluation.

A ferric smectite clay material was synthesized and further intercalated with Al2O3 pillars for the first time with the aim of evaluating its ability to be used as heterogeneous catalyst for the photo-Fenton decolorization of azo dye Orange II. UV irradiation was found to enhance the activity of the catalyst in the heterogeneous photo-Fenton process. Catalyst loading of 0.5g/L and hydrogen peroxide concentration of 13.5mM yielded a remarkable color removal, accompanied by excellent catalyst stability. The decolorization of Orange II followed the pseudo-first-order kinetics for initial dye concentrations from 20 to 160mg/L. The central composite design (CCD) based on the response surface methodology (RSM) was applied to evaluate the effects of several operating parameters, namely initial pH, catalyst loading and hydrogen peroxide concentration, on the decolorization efficiency. The RSM model was derived and the response surface plots were developed based on the results. Moreover, the main intermediate products were separated and identified using gas chromatography-mass spectrometry (GC-MS) and a possible degradation pathway was proposed accordingly. The acute toxicity experiments illustrated that the Daphniamagna immobilization rate continuously decreased during 150min reaction, indicating that the effluent was suitable for sequential biological treatment.

Effect of microwave-assisted system on transesterification of castor oil with ethanol / Efecto de microondas en la transesterificación de aceite de higuerilla / Efeito microondas em transesterificação do óleo de rícino

A systematic study of microwave-assisted transesterification of castor oil was conducted in the presence of ethanol and of potassium hydroxide as catalyst. Effects of various reaction parameters such as reaction time, catalyst concentration, reaction temperature and ethanol-oil molar ratio were analyzed. Ethyl esters were successfully produced by microwave-assisted transesterification. The maximum yield was 80.1% at 60°C, 10:1 alcohol: oil molar ratio, 1.5% potassium hydroxide and 10 min. The results show that there was a reduction in reaction time for microwave-assisted transesterification as compared to conventional heating, yields were slightly affected by temperature from 40-70°C; this indicates a significant effect of microwaves even at low temperatures.

Se realizó un estudio sistemático del efecto de la radiación microondas en la transesterificación de aceite de higuerilla con etanol en presencia de hidróxido de potasio como catalizador. Diversos parámetros fueron analizados, entre ellos el tiempo de reacción, concentración de catalizador, temperatura y relación molar etanol-aceite. De acuerdo con los resultados, la transesterificación asistida por microondas resultó útil para la producción de etilésteres obteniéndose un rendimiento máximo de 80.1% a 60°C, una relación molar alcohol: aceite de 10:1, 1.5% de hidróxido de potasio y 10 min de reacción. Se observó una reducción en el tiempo de reacción para la transesterificación asistida por microondas comparada con el calentamiento convencional. Los resultados muestran que los rendimientos son ligeramente afectados por la temperatura en el rango 40-70°C lo que indica un efecto importante de las microondas incluso a bajas temperaturas.

O presente artigo, foi realizado um estudo sistemático da transesterificação assistida por irradiação de microondas com óleo de rícino na presença de etanol e de hidróxido de potássio como catalizador. Analisou-se os efeitos da variação alguns parâmetros da reação, tais como, tempo de reação, concentração de catalisador, temperatura de reação e proporção molar de óleo de etanol. De acordo com os resultados, os ésteres etílicos foram produzidos com êxito por transesterificação assistida por microondas, obtendo um rendimento máximo de 80.1% a 60 °C, razão molar de 10:1 álcool: óleo, 1.5% de hidróxido de potássio em 10 min. Houve uma redução no tempo de reação de transesterificação assistida por microondas, em relação ao aquecimento convencional. Os resultados mostram que os rendimentos são ligeiramente afetados pela temperatura, no intervalo de 40-70 °C, indicando um efeito significativo de microondas mesmo a baixas temperaturas.

Ultrasound-assisted removal of tetracycline from aqueous solution by mesoporous alumina.

This work describes the removal of tetracycline (TC) from aqueous solution using a mesoporous alumina (meso-Al2O3) as adsorbent in the presence of ultrasonic irradiation. Adsorption of TC was investigated under various operating conditions, including pH, adsorbent dosage, ultrasound power, and initial TC concentration. The results showed that the rate of TC sorption was enhanced with the assistance of ultrasound. The TC removal increased with the increase in sorbent dosage, pH and ultrasound power, but decreased with the increase in initial TC concentration. The adsorption isotherm data were fitted properly with the Freundlich model under ultrasonic irradiation, and the adsorption process followed a pseudo-second-order kinetic model.

Activation of microcrystalline cellulose in a CO(2)-based switchable system.

MCC Hammer: Microcrystalline cellulose (MCC) is dissolved and subsequently regenerated in a CO2 -based switchable solvent system, drastically reducing its crystallinity index and thereby its recalcitrance to hydrolysis. Among the investigated systems, based on cheap, widely available chemicals, is one capable of dissolving up to 15 wt % MCC within 1 h at room temperature. Break it down!

Intershell spacing changes in MWCNT induced by metal-CNT interactions.

The intershell spacing in different regions of a multi-walled carbon nanotube (MWCNT) was determined by analysis of high resolution transmission electron (HR-TEM) micrographs. Three general effects can be pointed out, (1) the regular intershell spacing of a CNT is bigger than that in a graphitic carbon because the curvature generates geometrical and electronic deformations which increase repulsion forces between the graphene sheets, (2) when an extra curvature appears, e.g. at the tip of a closed CNT or in a bamboo-like structure, the intershell spacing is expanded due to the extra repulsion caused by the combination of pentagonal and heptagonal rings imbibed in the hexagonal lattice, and (3) when a metal particle interacts with a CNT, the intershell spacing is compressed due to strong metal-CNT interactions.

Dehydration of highly concentrated solutions of fructose to 5-hydroxymethylfurfural in a cheap and sustainable choline chloride/carbon dioxide system.

Fête DES sciences: The dehydration of fructose and inulin to HMF is conveniently performed in a cheap and sustainable choline chloride/CO(2) deep eutectic solvent (DES) system. The medium is capable of converting high contents of fructose (>100 wt %) without affecting the yield of HMF (up to 72 %). The purity of the recovered HMF is >98%, and the reaction medium can be recycled.

Acid-catalyzed dehydration of fructose and inulin with glycerol or glycerol carbonate as renewably sourced co-solvent.

Ionic liquids (ILs) can be partially substituted by glycerol or glycerol carbonate as cheap, safe, and renewably sourced co-solvents in the acid-catalyzed dehydration of fructose and inulin to 5-hydroxymethylfurfural (HMF). In the particular case of glycerol, we found that HMF can be conveniently extracted from the IL/glycerol (65:35) mixture with methylisobutylketone, limiting the reactivity of glycerol with HMF and allowing the recovery of HMF with a high purity (95 %). Influences of the fructose content, temperature, and the nature of the ionic liquid are also discussed. The possible use of industrial-grade glycerin is also investigated. We demonstrate that by using glycerol carbonate, up to 90 wt % of the IL can be successfully substituted, decreasing the environmental costs of traditional IL-based processes.

Sulfonic acid functionalized crystal-like mesoporous benzene-silica as a remarkable water-tolerant catalyst.

Here we report that sulfonated crystal-like benzene-silica is much more robust and active than conventionally used periodic mesoporous silica for catalyzing aqueous organic reactions.

Rational design of solid catalysts for the selective use of glycerol as a natural organic building block.

Glycerol is the main co-product of the vegetable oils industry (especially biodiesel). With the rapid development of oleochemistry, the production of glycerol is rapidly increasing and chemists are trying to find new applications of glycerol to encourage a better industrial development of vegetable oils. In this Review, attention is focused on the selective use of glycerol as a safe organic building block for organic chemistry. An overview is given of the different heterogeneous catalytic routes developed by chemists for the successful and environmentally friendly use of glycerol in sustainable organic chemistry. In particular, the effects of different catalyst structural parameters are discussed to clearly highlight how catalysis can help organic chemists to overcome the drawbacks stemming from the use of glycerol as a safe organic building block. It is shown that heterogeneous catalysis offers efficient routes for bypassing the traditional use of highly toxic and expensive epichlorohydrin, 3-chloro-1,2-propanediol, or glycidol, which are usually used as a glyceryl donor in organic chemistry.

Selectivity enhancement of silica-supported sulfonic acid catalysts in water by coating of ionic liquid.

Coating of silica-supported sulfonic acid catalysts with hydrophobic ionic liquid leads to a significant improvement of catalyst selectivity. Many organic reactions, including Prins cyclization, cycloaddition of epoxide to aldehyde, and dehydrative etherification of secondary benzyl alcohols, proceed well in formalin or pure water. In particular, tandem dehydration/Prins cyclization reactions of tertiary and secondary alcohols with formaldehyde were developed for the first time.

Significant enhancement on selectivity in silica supported sulfonic acids catalyzed reactions.

Thanks to strong hydrophilic interactions between reaction products and the catalyst surface, mesoporous silica supported sulfonic sites were found to be much more selective than homogeneous and common solid acid catalysts.

Glycerol derivatives of cutin and suberin monomers: synthesis and self-assembly.

Glycerol derivatives of cutin and suberin monomers were synthesized by acid catalysis. Their dispersion in an aqueous solution was examined by phase contrast microscopy, neutron scattering, and solid state NMR. It is shown that the phase behavior strongly depends on the nature of the derivatives forming either lumps of aggregated membranes or well dispersed membranes.