The regularities of sunflower, rapeseed and flaxseed oils’ triglycerides transesterification by the head fraction of ethyl alcohol in the presence of various catalysts have been investigated. The cation exchange resin KU-2-8 in H+-form and cation exchange resin KU-2-8 containing an immobilized Cu2+-ions (untreated and treated by 0,1 M sodium hydroxide solution for 90 min and for 7 days) were used as catalyst. It was shown that the all investigated catalysts except the untreated cation exchange resin KU-2-8 containing an immobilized Cu2+-ions allow to achieve of triglycerides conversion over 90 % under the reaction conditions. It was found that the catalyst KU-2-8 containing an immobilized Cu2+-ions treated by 0.1 M sodium hydroxide solution for 90 min shows the highest activity. Also it was found that this catalyst allows to achieve triglyceride conversion all of studied vegetable oils over 99.5% in 180 min of reaction. Simultaneously it was found that the highest rate of transesterification reaction in its presence is observed. The influence of these catalysts on the esterification reaction of free fatty acids, present in vegetable oils, by ethyl alcohol, present in the head fraction, was studied. It was established that the influence of the investigated catalysts on the esterification reaction is different. It was shown that cation exchange resin KU-2-8 containing an immobilized Cu2+-ions treated by 0.1 M sodium hydroxide solution for 90 min catalyzes the esterification reaction of free fatty acids of all investigated oils. Their conversion is from 21.6 % (in sunflower oil) up to 74.1 % (in rapeseed oil). At the same time, it was found that long-term treatment of cation exchange resin KU-2-8 containing an immobilized Cu2+-ions by sodium hydroxide solution leads to a sharp decrease or loss of catalyst activity in the esterification reaction of free fatty acids by ethyl alcohol. It was shown that the use of this catalyst for the transesterification of rapeseed and sunflower oils’ triglycerides even increases the acid number of the reaction mixture, namely to the partial hydrolysis of triglycerides. The obtained results show that the short-term treatment the cation exchange resin KU-2-8 containing an immobilized Cu2+-ions by 0.1 M alkali solution is one of the ways that allow to increase its catalytic activity in the transesterification process of vegetable oils by head fraction of ethyl alcohol. It is assumed that such treatment affects the catalytic activity of Cu2+-ions due to changes in the electron density on the catalyst cation caused the coordination of part of the OH–-anions. The long-term treatment of the cation exchange resin containing an immobilized Cu2+-ions by alkali solution causes a maximum saturation of the cation coordination sphere. This obviously creates steric problem of a reagents access to the catalyst and reduces the catalytic activity cation exchange resin.

The research was aimed at determining the dependences of sustainability indicators on the parameters of the sunflower oil transesterification with ethyl, propyl, and butyl alcohol catalyzed by anion exchange resin AV-17-8 with OH– ions or cation exchange resin KU-2-8 with H+ or immobilized Zn2+, Sn2+, Ni2+, Co2+, and Cu2+ ions. Such sustainability indicators as the E-factor, atomic efficiency, mass intensity and mass productivity, reaction mass efficiency, stoichiometric factor, etc., have been determined. We established that sustainability indicators of transesterification catalyzed by ion exchange resins depend on the yield of higher fatty acid esters that can be achieved by immobilized metal ions. The unreacted alcohol regeneration significantly reduces the E-factor value and increases the reaction mass efficiency. During the sunflower oil ethanolysis, the minimum E-factor value is achieved at the ethyl alcohol:triglyceride molar ratio corresponding to the maximum yield of higher fatty acid esters. The reaction mass efficiency calculated without considering the unreacted alcohol regeneration is one of the criteria for determining its regeneration expediency. The sustainability indicators are the additional criteria for selecting optimal conditions of the sunflower oil transesterification with aliphatic alcohols catalyzed by ion exchange resins. The calculated sustainability indicators indicate that the investigated ion exchange resins as heterogeneous transesterification catalysts provide a high yield of higher fatty acid esters. Using the researched catalysts ensures a low E-factor, making the process environmentally friendly.

Transesterification of sunflower oil triglycerides by C1-C4 aliphatic alcohols in the presence of cation exchange resin KU-2-8 with immobilized divalent metal ions has been studied. It was found that the reaction occurs at a high initial rate and the conversion of triglycerides for 180 min in presence aliphatic alcohols C1– C3 is 88.4-99.8 %. It is shown that under these conditions the rate of transesterification reaction of triglycerides with butan-1-ol is significantly lower and the conversion achieved in 180 min does not exceed 52.3 %.

Transesterification of sunflower oil triglycerides with propan-2-ol catalyzed by sulfuric acid has been studied. The effect of the homogeneous acid catalyst content and the triglycerides of sunflower oil : propan-2-ol molar ratio on the reagents conversion, selectivity of diisopropyl ether formation, the acid number and the color of reactions products on the iodine scale was determined. It was established that an increase in the sulfuric acid content from 1 wt. % up to 3 wt. % leads to a slight increase in the triglycerides conversion and a significant increase in the propan-2-ol conversion. A further increase in the acid catalyst content causes a decrease in the conversion of both triglycerides and alcohol. Comparison of the obtained results with the data on the reaction products composition allowed us to conclude that a significant increase in the propan-2-ol conversion with an increase in the sulfuric acid content to 3–4 wt. % due to the increase in the diisopropyl ether selectivity formation from 5% by an acid catalyst content of 1 wt. % to almost 65% by a sulfuric acid content of 4 wt. %. It is shown that an increase in the sulfuric acid content in the reaction mixture also leads to a significant increase in the reaction product's color according to the iodine scale - almost 5 times, which also indicates the course of side condensation reactions with the double bonds of higher fatty acids participation, which are part of triglycerides composition. It is established that the reaction product's acid number regularly increases with an increase in the acid catalyst content in the reaction mixture. It is shown that the reaction products acid number value is determined by the amount of acid catalyst used. It is established that the activity of the sulfuric acid in the sunflower oil triglycerides transesterification reaction is slightly lower than the activity of cation exchange resin KU-2-8. The cation exchange resin under the same conditions provides more than 15% higher triglycerides conversion with a lower reaction product's color on the iodine scale value and the absence of a diisopropyl ether formation side reaction. It is concluded that using sulfuric acid as a catalyst for triglyceride transesterification by propan-2-ol is entirely possible.

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