(679k) Kinetic Study of the Hydroxylation of Epoxidized Palm Oil Using NIR Spectroscopy for Reaction Monitoring

Vegetables oils and animal fats are renewable raw materials mainly used in the food industry, in the production of biofuels and in the oleochemical industry, which has a wide variety of derivates including functional chemicals and raw materials for polymers. One of the most used oleochemical derivates to produce biobased polymers are fatty polyols, commercially known by NOP’s (Natural Oil Polyols). It is estimated that the annual world requirement of NOP’s is between 1 and 6.6 Mt. Additionally, Colombian market of polyols is about 7.000 tons per year, which are entirely petroleum derivate. The use of polyols in the industry is for the manufacture of polyurethanes

Colombia is a major producer of palm oil with a current annual production of around 1.6 million tons, which is mostly used in the food industry (58%) and in the manufacture of biodiesel (33%) via transesterification with methanol. However, during last years this agricultural sector has been suffering by large crop losses caused by the bud rot disease. As a result, growers associations started to develop and implement a more resistant hybrid specie obtained by crossing Elaeis guineensis y Elaeis oleifera. This hybrid exhibits a higher productivity, and the obtained vegetable oil has a higher content of oleic acid within the trialcyl glycerides. For this reason, the oil from this new hybrid is commercially refereed as high-oleic palm oil.

The higher content of unsaturated fatty acid chains confers this oil suitable properties for further valorization, other than biodiesel, in the oleochemical industry. High-oleic palm oil could be used as feedstock in the production of epoxides and polyols, which have a large demand in the manufacture of polymers and resins. In this regard, the aim of this work is to develop a kinetic study of the hydroxylation reaction of epoxidized high oleic palm oil focusing on the production of polyols.

The chemical pathway to produce polyols was the epoxidation of double bounds in the unsaturated fatty acid chains, followed by hydroxylation with a proton donor. The proton donor used to cleavage oxirane rings was ethylene glycol to produce two hydroxyl groups for each epoxy group and the catalyst was sulfuric acid. The kinetic model was a power law, experiments with different catalyst loading were done to verify the relation between the catalyst loading and reaction rate, the order of the reagents were checked by adding various molar ratio, finally, to compute the kinetic parameter a three-factor box Behnken design of experiments was carried out, then to adjust the parameters value a genetic algorithm was done.

The advance of the reaction in the different tests was carried out by measuring the epoxy number and the hydroxyl value. The hydroxyl value is measure by titration employing pyridine and anhydride acetic as reagents. Those chemicals are toxic, and its handling is dangerous, additionally this technique takes 2-3 hours to perform. That is why the measurement of the hydroxyl value was done by NIR spectroscopy. Before measuring the hydroxyl value, a calibration was made, which was carried out by taking the absorbance of known hydroxyl value samples and correlate this absorbance with the value using PLS regression (partial least square).

In a subsequent stage, and to assess the main characteristics of natural oil polyols (molecular weight, viscosity at room temperature, functionality), different ring opening agents were used during hydroxylation, namely diethylene glycol, propylene glycol and glycerol.