Esterification of fatty acids with glycerol over Fe–Zn double-metal cyanide catalyst

Valorisation of crude glycerol to value-added products: Perspectives of process technology, economics and environmental issues

The enormous production of glycerol, a waste stream from biodiesel industries, as a low-value product has been causing a threat to both the environment and the economy. Therefore, it needs to be transformed effectively and efficiently into valued products for contributing positively towards the biodiesel economy. It can either be converted directly into competent chemicals or can be used as a feedstock/precursor for deriving valuable derivatives. In this review article, a technical evaluation has been stirred up, various factors and technologies used for producing value-added products from crude glycerol, Environmental and economic aspects of different conversion routes, cost factors and challenges of integration of the different routes for biorefinery have been reviewed and elaborated. There are tremendous environmental benefits in the conversion of crude glycerol via the biochemical route, the product and residue become eco-friendly. However, chemical conversions are faster processes, and economically viable if environmental aspects are partially ignored.

Esterification of Glycerol With Oleic Acid Over Hydrophobic Zirconia-Silica Acid Catalyst and Commercial Acid Catalyst: Optimization and Influence of Catalyst Acidity

Catalytic esterification of glycerol with oleic acid (OA) was optimized over hydrophobic mesoporous zirconia-silica heterogeneous acid catalyst (ZrO₂-SiO₂-Me&Et-PhSO₃H) and benchmarked with commercial catalysts (Aquivion and Amberlyst 15) in order to examine the effect of catalyst acidity on conversion, yield and product selectivity. The process optimisation results showed an 80% conversion with a 59.4% glycerol mono-oleate (GMO) and 34.6% glycerol dioleate (GDO) selectivities corresponding to a combined GMO and GDO selectivity of 94.8% at equimolar OA-to-glycerol ratio, 160°C reaction temperature, 5 wt% catalyst concentration with respect to the OA weight and 4 h reaction time. This work reveals that the hydrophobic and mild acidic ZrO₂-SiO₂-Me&Et-PhSO₃H catalyst outperformed Amberlyst 15 and Aquivion with a yield of 82% and GMO selectivity of 60%. It is found that catalyst acidity is a key parameter for catalytic activity and conversion rate. Nevertheless, high acidity/acid strength reduced the product yield in the glycerol esterification of OA.

Double metal cyanides as heterogeneous Lewis acid catalysts for nitrile synthesis via acid-nitrile exchange reactions

A series of transition metal-based double metal cyanides (DMCs) were studied as catalysts for the synthesis of nitriles via acid-nitrile exchange reaction.

Fatty Acid Esterification with Polyols over Acidic Montmorillonite

The production of fatty acid esters from stearic, oleic, and palmitic acids and polyols (ethylene glycol and glycerol) was investigated in this work. A series of montmorillonite-based clays catalysts (KSF, KSF/0, KP10, and K10), having different physicochemical properties, were used as acidic catalysts. The influence of the specific surface area and the acidity of the catalysts on the esterification rate were explored. The best catalytic activities were obtained with KSF catalyst. The optimization of various factors on the reaction was also studied, including catalyst concentration, reaction temperature and molar ratio (polyol / fatty acid). The yield rate reached 94% under the optimum conditions and the recovery rate maintained more than 96% after 5 batches.

Catalytic esterification of bioglycerol to value-added products

The inevitably low value of bioglycerol has led to extensive investigations on glycerol conversion to value-added chemicals. This review focuses on the industrially important catalytic esterification of glycerol with oleic acid attributable to its high commercial value. Conventionally, the catalytic esterification of long-chain fatty acids with glycerol is operated at extreme operating conditions (homogeneous acid catalyst, high temperature, and intensive vacuum system). Because of these, rational design of reliable solid acid catalysts for water-sensitive esterification process is needed in order to enhance existing process condition. Up until now, the recent development of efficient and environmentally benign catalysts for esterification of glycerol with oleic acid has not been captured in any review. Therefore, the current literatures of catalytic esterification of glycerol with oleic acid and their affecting parameters are primarily discussed in this review. This review has shown that the hydrophobicity surface of catalysts is vital to boost up the reaction activity of polar glycerol and immiscible phase behavior of reactants. In addition, the concluding remarks for catalyst selectivity of glycerol monooleate, dioleate, and trioleate synthesis are presented. The paper also highlights the research gaps and future direction of this important research field.

Improving the esterification activity of Pseudomonas fluorescens and Burkholderia cepacia lipases via cross-linked cyclodextrin immobilization

Improving activities: solid cross-linked β-cyclodextrin enzymes can remarkably improve thermal stability and enzyme activity as compared to commercial immobilized enzymes in esterification reactions (e.g., monostearin synthesis).