Jiří Pecha

A Review of Catalytic Systems for Glycerol Oxidation: Alternatives for Waste Valorization

Endeavours leading to the study of glycerol oxidation result from the imperative necessity for wise utilization of surplus glycerine generated as by-product from biodiesel manufacture. The oxidation of glycerol is one of the most promising reactions as it leads to the generation of valuable glycerol derivatives that find broad application in pharmaceutical, polymer, and food industries. This review highlights the processing alternatives for glycerol by means of biocatalyst-mediated, heterogeneous, homogeneous, and electrochemical oxidation. The current state of the art is evaluated and recommendations for further research and future directions are included.

Pilot-scale production of biodiesel from waste fats and oils using tetramethylammonium hydroxide.

Annually, a great amount of waste fats and oils not suitable for human consumption or which cannot be further treated are produced around the world. A potential way of utilizing this low-cost feedstock is its conversion into biodiesel. The majority of biodiesel production processes today are based on the utilization of inorganic alkali catalysts. However, it has been proved that an organic base - tetramethylammonium hydroxide - can be used as a very efficient transesterification catalyst. Furthermore, it can be employed for the esterification of free fatty acids - reducing even high free fatty acid contents to the required level in just one step. The work presented herein, is focused on biodiesel production from waste frying oils and animal fats using tetramethylammonium hydroxide at the pilot-plant level. The results showed that the process performance in the pilot unit - using methanol and TMAH as a catalyst, is comparable to the laboratory procedure, even when the biodiesel is produced from waste vegetable oils or animal fats with high free fatty acid content. The reaction conditions were set at: 1.5% w/w of TMAH, reaction temperature 65°C, the feedstock to methanol molar ratio to 1:6, and the reaction time to 120min. The conversion of triglycerides to FAME was approximately 98%. The cloud point of the biodiesel obtained from waste animal fat was also determined.

Simultaneous determination of main reaction components in the reaction mixture during biodiesel production.

The proposed analytical method allows for simultaneous determination by GC using a programed temperature vaporization injector and a flame ionization detector of the main reaction components (i.e. glycerol, methyl esters, mono-, di-, and triacylglycerols) in the reaction mixture during biodiesel production. The suggested method is convenient for the rapid and simple evaluation of the kinetic data gained during the transesterification reaction and, also partially serves as an indicator of the quality of biodiesel and mainly, as the indicator of the efficiency of the whole production process (i.e. the conversion of triacylglycerols to biodiesel and its time progress). The optimization of chromatographic conditions (e.g. the oven temperature program, injector setting, amount of derivatization reagent, and the derivatization reaction time) was performed. The method has been validated with crude samples of biodiesel made from waste-cooking oils in terms of linearity, precision, accuracy, sensitivity, and limits of detection and quantification. The results confirmed a satisfactory degree of accuracy and repeatability (the mean RSDs were usually below 2%) necessary for the reliable quantitative determination of all components in the considerable concentration range (e.g. 10-1100 μg/mL in case of methyl esters). Compound recoveries ranging from 96 to 104% were obtained.

DEVELOPMENT OF AN HPLC METHOD FOR THE DETERMINATION OF GLYCEROL OXIDATION PRODUCTS

An HPLC method for the separation of glycerol oxidation products, namely glyceraldehyde, dihydroxyacetone, mesoxalic, tartronic, and glycolic and glyceric acids on an ion-exchange 8% cross-linked calcium sulfonated divinylbenzene-styrene resin column was developed and validated. The conditions reported include temperature (70°C), flow rate (0.5 mL/min) and concentration of the mobile phase (3 mM H2SO4) using isocratic elution with ultraviolet and refractometric detectors. The effect of the mobile phase flow rate and concentration as well as column temperature on the resolution of peaks is described. Excellent correlation coefficient in the calibration model was observed for all analytes over the concentration range of 0.5 to 10 mg/mL. The method was also validated in terms of intra-day precision, sensitivity, accuracy, and detection and quantification limits. The method conditions were applied to the identification of products derived from the chemical oxidation of glycerol. Supplemental materials are available for this article. Go to the publishers online edition of the Journal of Liquid Chromatography & Related Technologies to view the supplemental file.