The influence of the feedstock type and reaction parameters on the synthesis of fatty acid pentyl and hexyl esters

Reakcijom transesterifikacije u kojoj trigliceridi iz ulja/masti reagiraju s alkoholom u prisutnosti katalizatora dolazi do nastajanja alkilnih estera masnih kiselina, odnosno biodizela. Budući da se dobiva iz obnovljivih izvora, biodizel se dodaje u određenim omjerima u dizelsko gorivo, čime se smanjuje utjecaj na okoliš. Metanol se u odnosu na ostale alkohole najviše upotrebljava u proizvodnji biodizela, međutim biodizel se također može proizvoditi iz viših alkohola čija je prednost što se mogu dobiti iz obnovljivih izvora za razliku od metanola. U ovom radu provedena je sinteza biodizela bazično kataliziranom transesterifikacijom, u prisutnosti kalijeva hidroksida, s različitim biosirovinama (suncokretovo, repičino, kokosovo, otpadno jestivo ulje i životinjska mast) te upotrebom alkohola 1-pentanola ili 1-heksanola. Istražen je utjecaj različitih reakcijskih uvjeta na iskorištenje reakcije transesterifikacije. Uvjeti koji su se mijenjali bili su: molarni omjer alkohola i ulja/masti (5:1 i 12:1), vrijeme reakcije (2, 5, 15 i 30 minuta) te maseni udio katalizatora (1 i 3 %). Dobiveni rezultati ukazuju da molarni omjer alkohola i ulja/masti ima najveći utjecaj na iskorištenje reakcije transesterifikacije. Veliki utjecaj na iskorištenje ima i udio katalizatora, dok vrsta biosirovine i vrijeme provedbe reakcije ne utječu značajno na iskorištenje. Iskorištenja dobivena sintezom biodizela iz 1-pentanola i 1-heksanola pri istim uvjetima reakcije imaju slične vrijednosti, ali uočeno je da se povećanjem duljine alkilnog dijela lanca smanjuje iskorištenje korištenjem suncokretovog i repičinog ulja pri omjeru 5:1 s 3 mas.% KOH. Isto tako, vidljivo je da veći udio zasićenih masnih kiselina u sirovini pridonosi višem iskorištenju reakcije. Zadovoljavajuća iskorištenja dobivena su pri molarnom omjeru alkohola i ulja/masti 12:1 i 1 mas.% KOH sintezom iz suncokretovog, repičinog i otpadnog jestivog ulja te životinjske masti, dok su kod kokosovog ulja zadovoljavajuća iskorištenja postignuta korištenjem 5:1 molarnog omjera i 3 mas.% KOH.The transesterification reaction in which triglycerides from oils/fats react with alcohol in the presence of a catalyst leads to the formation of alkyl esters of fatty acids, i.e. biodiesel. Since it is obtained from renewable sources, biodiesel is added in certain proportions to diesel fuel, which reduces the impact on the environment. Compared to other alcohols, methanol is mostly used in the production of biodiesel, but it can also be produced from higher alcohols, the advantage of which is that they can be obtained from renewable sources, unlike methanol. In this work, the synthesis of biodiesel was carried out by base-catalyzed transesterification, in the presence of potassium hydroxide, with different feedstocks (sunflower, rapeseed, coconut, waste cooking oil and animal fat) and using the alcohol 1-pentanol or 1-hexanol. In addition, the influence of different reaction conditions on the yield of the transesterification reaction was investigated. The conditions that were varied were: the molar ratio of alcohol and oil/fat (5:1 and 12:1), the reaction time (2, 5, 15 i 30 minute) and the mass fraction of the catalyst (1 and 3 %). The obtained results indicate that the molar ratio of alcohol and oil/fat has the greatest influence on the utilization of the transesterification reaction. The mass fraction of the catalyst also has a great influence on the conversion, while the type of feedstock and the reaction time do not significantly affect the conversion. The yields obtained by the synthesis of biodiesel from 1-pentanol and 1-hexanol under the same reaction conditions have similar values, but it was observed that increasing the length of the alkyl chain decreases the yield using sunflower and rapeseed oil at a ratio of 5:1 with 3 wt% KOH. Also, it is evident that a higher amount of saturated fatty acids in the feedstock contributes to a higher conversion of the reaction. Satisfactory conversions were obtained at a molar ratio of alcohol and oil/fat of 12:1 and 1 wt% KOH synthesis from sunflower, rapeseed and waste cooking oil and animal fat, while with coconut oil sufficient conversions were achieved using a 5:1 molar ratio and 3 wt% KOH