Intensified processes for FAME production from waste cooking oil: a technological review

This article reviews the intensification of fatty acid methyl esters (FAME) production from waste cooking oil (WCO) using innovative process equipment. In particular, it addresses the intensification of WCO feedstock transformation by transesterification, esterification and hydrolysis reactions. It also discusses catalyst choice and product separation. FAME production can be intensified via the use of a number of process equipment types, including as cavitational reactors, oscillatory baffled reactors, microwave reactors, reactive distillation, static mixers and microstructured reactors. Furthermore, continuous flow equipment that integrate both reaction and separation steps appear to be the best means for intensifying FAME production. Heterogeneous catalysts have also shown to provide attractive results in terms of reaction performance in certain equipment, such as microwave reactors and reactive distillation

The effect of host structure on the selectivity and mechanism of supramolecular catalysis of Prins cyclizations.

The effect of host structure on the selectivity and mechanism of intramolecular Prins reactions is evaluated using K12Ga4L6 tetrahedral catalysts. The host structure was varied by modifying the structure of the chelating moieties and the size of the aromatic spacers. While variation in chelator substituents was generally observed to affect changes in rate but not selectivity, changing the host spacer afforded differences in efficiency and product diastereoselectivity. An extremely high number of turnovers (up to 840) was observed. Maximum rate accelerations were measured to be on the order of 105, which numbers among the largest magnitudes of transition state stabilization measured with a synthetic host-catalyst. Host/guest size effects were observed to play an important role in host-mediated enantioselectivity

Spiers Memorial Lecture: Interplay of theory and computation in chemistry—examples from on-water organic catalysis, enzyme catalysis, and single-molecule fluctuations

In this lecture, several examples are considered that illustrate the interplay of experiment, theory, and computations. The examples include on-water catalysis of organic reactions, enzymatic catalysis, single molecule fluctuations, and some much earlier work on electron transfer and atom or group transfer reactions. Computations have made a major impact on our understanding and in the comparisons with experiments. There are also major advantages of analytical theories that may capture in a single equation an entire field and relate experiments of one type to those of another. Such a theory has a generic quality. These topics are explored in the present lecture

Investigating nano-structured domains within ionic liquids: the effect of cation change on thermal equilibrium and relaxation of spiropyran and spirooxazine.

The established belief that ionic liquids (ILs) behave as homogenous solvents such as that observed in molecular solvents has been challenged.1, 2 Previous use of solvatochromic probe dyes has allowed for the traditional parameter of ‘polarity’ to be determined.3 These values were compared to the kinetics of the photochromic spirocyclic compounds spirooxazine (SO) and spiropyran (SP). The nature of SO substituents limit the ability of hydrogen bond formation and so relies primarily on electrostatic interactions with the solvent system. Such an increase in solute freedom would be expected to increase the ability of the molecules to dissociate and migrate within the solvent system. A polarity-kinetic relationship for spirocyclic compounds has been established in molecular solvents with increasing polarity exhibiting decreased rates of thermal relaxation from the coloured merocyanine (MC) form to the spiro (SO/SP) form.4 However, thermal relaxation of SO in ionic liquids fails to present a correlation between polarity and kinetics. Kinetic studies were further enhanced by analysis of the relaxation process using thermodynamic parameters of activation. Previous studies have (primarily molecular modelling) proposed that ionic liquids possess a structured in-homogenous structure containing distinct areas of polar and non-polar regions.5 The probe dyes used to examine parameters such as hydrogen bonding (Kamlet-Taft) and polarity (ET30) may only examine a particular region in the solvent. This means that the probe molecules may solvate in one region while compounds such as SO may interact in another region completely and therefore not allow for correlation of polarity to thermal relaxation rates observed. The closed form is a neutral compound exhibiting non-polar characteristics. MC, due to its zwitterionic nature, is in contrast highly polar. We believe that the size and ratio of polar to non-polar regions may be a critical factor in the process of SO thermal relaxation. Increasing non-polar regions may encourage the SO form by shifting equilibrium and encouraging migration and facilitate enhanced closure of MC within the solvent system. Thermal relaxation of SO may therefore allow for confirmation of the theory of IL structuring. Due to the large range of ILs possible, a correlation in structural effects and a quantifiable change may aid in a more detailed understanding of ILs and facilitate customisability of the liquids to meet specific polarity/solvation requirements

Construction of spirocarbocycles via gold-catalyzed intramolecular dearomatization of naphthols.

A highly efficient, gold-catalyzed intramolecular dearomatization reaction of naphthols via 5-endo-dig cyclization is described. This facile and direct approach furnishes spirocarbocycles in excellent yields under mild conditions

Effect of catalytic conditions on the synthesis of new aconitate esters

Sugar cane is a crop which generates large amounts of biomass and a juice rich in highvalue natural molecules. After extracting sugar from the juice, the recovering of various compounds such as organic acids contained in molasses could contribute to increase the competivity of the sugar industry. Therefore, according to the biorefinery approach, we propose to study the chemical conversion of one of these acids, the aconitic acid, by esterification reactions. A new series of aconitate esters have been synthesized by combining aconitic acid and alcohols from natural origin. The effects of experimental conditions have been investigated and have shown that the type of catalysis has a significant effect on the selectivity. Kinectics have thus been performed to determine the best conditions to synthetize enriched compositions in esters. Homogeneous catalysis generates the highest yield in triester. Heterogeneous catalysis(macroporous resins) is prefered for the production of monoesters while catalysis assisted by ionic liquid is adapted to prepare mainly diesters. Green indicators have been discussed according to the calculations performed. The resulting polyfunctional esters are totally biosourced molecules and have a great potential as bioproducts for different applications