- Sulfonic acid-functionalized organic knitted porous polyaromatic microspheres as heterogeneous catalysts for biodiesel production
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The use of renewable energy sources decreases the consequences of greenhouse gas emission from fossil fuels. Biodiesel, an easily burning and biodegradable fuel, is an alternative to conventional diesel fuel. The esterification of long-chain fatty acids and transesterification of triglycerides are two major reactions widely used to convert vegetable oils or animal fats into biodiesel. As solid acid catalysts are considered promising candidates for biodiesel production, we have synthesized a series of organic knitted porous polyaromatics (OPPs) using pyrene, anthracene, and naphthalene as monomers via Friedel-Crafts alkylation, followed by crosslinking reactions. The resultant polymers showed good surface morphology, stability and swelling property, high capacity for functionalization due to the unreacted bromomethyl groups on the surface, and excellent hydrophobicity. The sulfonated polymer microspheres obtained by the surface sulfonation showed good surface acidity; thus, they can be employed as heterogeneous solid acid catalysts for the esterification of long-chain fatty acids and transesterification of triglycerides, and they are reusable without any leaching of functional groups.
- Varyambath, Anuraj,Kim, Mi-Ra,Kim, Il
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- Use of Lecitase-Ultra immobilized on styrene-divinylbenzene beads as catalyst of esterification reactions: Effects of ultrasounds
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Abstract In this work it was evaluated for the first time, the ester synthesis catalyzed by the phospholipase Lecitase-Ultra immobilized styrene-divinylbenzene beads (MCI-Lecitase), comparing the mechanical stirring and the ultrasonic energy. It was studied the specificity of the enzyme using carboxylic acids from C4 to C18, as well as the effects of alcohol chain, organic solvents, biocatalyst content, reaction temperature and substrate concentration. Caprylic and myristic acids were those with the highest reaction rates and yields, using ethanol as substrate. The shorter the alcohol chain, the higher the enzyme activity. Regarding the secondary alcohols, while MCI-Lecitase had no activity versus isopropanol, using 2-pentanol the activity was similar to that with 1-pentanol. Comparing the agitation systems, MCI-Lecitase presented an initial reaction rate more than 2-times higher in the ultrasound-assisted reaction than under traditional mechanical stirring. Moreover, under ultrasonic energy the maximum rate was achieved using 0.5 M of substrates, while under mechanical stirring the maximum enzyme activity was reached at 0.3 M of substrates. Concerning the operational stability, MCI-Lecitase was quite unstable, losing its activity after 6 reaction cycles. By adding molecular sieves in the reaction medium, MCI-Lecitase retained 30% of its initial activity after 6 cycles.
- Alves, Joana S.,Garcia-Galan, Cristina,Danelli, Daiane,Paludo, Natália,Barbosa, Oveimar,Rodrigues, Rafael C.,Fernandez-Lafuente, Roberto
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- Design, synthesis, antibacterial, and QSAR studies of myristic acid derivatives
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A series of esters and amides of myristic acid was synthesized and tested in vitro for antibacterial activity against Gram-positive and Gram-negative bacteria. All the compounds showed activity comparable to that of the standard drug, ciprofloxacin. The structural characteristics governing antibacterial activity of myristic acid derivatives was studied using QSAR methodology. The results showed that the antibacterial activity could be modeled using the topological descriptor, valence molecular connectivity index. The predictive ability of the models was cross-validated by construction of a test set. The low residual activity and high cross-validated r2 values ( rcv2 ) observed indicated the predictive ability of the developed QSAR models.
- Narasimhan, Balasubramanian,Mourya, Vishnukant,Dhake, Avinash
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p. 3023 - 3029
(2008/09/20)
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