| Abstract | Kroz posljednjih nekoliko desetljeća znanost se intenzivnije posvetila razvoju biogoriva s ciljem smanjenja onečišćenja okoliša uzrokovanog izgaranjem fosilnih goriva. Isto tako, porast broja svjetske populacije, brza industrijalizacija, urbanizacija, samo su neki od čimbenika koji uzrokuju rastuću potražnju za energijom i time potiču sve veću upotrebu fosilnih goriva. Kako su fosilna goriva neobnovljivi izvori energije, istraživanja su usmjerena na gorivo koje bi potjecalo isključivo od obnovljivih izvora. Kao dobra alternativa pokazao se biodizel zbog svoje ekološki prihvatljive prirode. Dobiva se katalitičkom transesterifikacijom – reakcijom biosirovine (biljnih ulja i životinjskih masti) s alkoholom uz prisutnost katalizatora. Sastavni dio masti i ulja su trigliceridi – esteri alkohola glicerola i viših masnih kiselina koji sudjeluju u reakciji transesterifikacije s alkoholom. Nastaju smjese alkilnih estera masnih kiselina (biodizel) i alkohol glicerol kao sporedni produkt. U ovom je radu biodizel sintetiziran transesterifikacijom iz palminog ulja kao glavne biosirovine te odabranih ravnolančanih alkohola: 1-propanola, 1-butanola, 1-pentanola, 1-heksanola, 1-oktanola uz prisutnost baznog katalizatora - kalijeva hidroksida (KOH), budući da svojstva primjene biodizela ovise o strukturi reaktanata korištenih u sintezi. Praćeni su utjecaji određenih parametara na reakciju sinteze, a to su: reakcijsko vrijeme (5, 15, 60 minuta), temperatura
(60 °C), molarni omjer alkohola i ulja (5:1 i 10:1) i maseni udio katalizatora (1 mas.% KOH i 3 mas.% KOH). Osim utjecaja navedenih parametara, praćen je i utjecaj molekulske mase alkohola na iskorištenje reakcije. S obzirom na navedene alkohole, u reakciji sinteze biodizela nastaju propilni, butilni, pentilni, heksilni i oktilni esteri masnih kiselina. Dobiveni rezultati pokazuju da reakcijsko vrijeme ima vrlo malo ili nimalo utjecaja na iskorištenje. Povećanje masenog udjela katalizatora i molarnog omjera alkohola i ulja generalno dovodi do većeg iskorištenja sinteze biodizela. S povećanjem molekulske mase alkohola pada polaritet alkohola, a u konačnici i alkoksidnog aniona koji ima glavnu ulogu u mehanizmu bazne transesterifikacije. Padom polariteta alkoksidnog aniona pada i njegov afinitet prema esterskoj skupini triglicerida i time se iskorištenje reakcije smanjuje. |
| Abstract (english) | Over the past few decades, science has devoted itself more intensively to the development of biofuels with the aim of reducing environmental pollution caused by the burning of fossil fuels. Likewise, the increase in the number of the world's population, rapid industrialization, urbanization, are just some of the factors that cause the growing demand for energy and thus encourage the ever-increasing use of fossil fuels. As fossil fuels are non-renewable sources of energy, researches aimed for fuel that would come exclusively from renewable sources. Biodiesel proved to be a good alternative due to its environmentally friendly nature. It is obtained by catalytic transesterification - the reaction of feedstocks (vegetable oils and animal fats) with an alcohol in the presence of a catalyst. An integral part of fats and oils are triglycerides - esters of glycerol and fatty acids that participate in the transesterification reaction with an alcohol. Therefore, fatty acid alkyl esters (biodiesel) and also alcohol glycerol as a by-product are produced. In this work, biodiesel was synthesized by base – catalyzed transesterification from palm oil as the main feedstock and selected straight-chain alcohols: 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-octanol, in the presence of a base catalyst - potassium hydroxide (KOH), since the application properties of biodiesel depend on the structure of the reactants used in the synthesis. The effects of certain parameters on the synthesis reaction were monitored: reaction time (5, 15, 60 minutes), temperature
(60 °C), molar ratio of alcohol and oil (5:1 and 10:1) and mass fraction of catalyst
(1 wt.% KOH and 3 wt.% KOH). In addition to the influence of the mentioned parameters, the influence of the molecular weight of alcohol on the reaction conversion was investigated, as well. With regard to the mentioned alcohols in the biodiesel synthesis reaction, fatty acid propyl, butyl, pentyl, hexyl and octyl esters were produced. The obtained results show that the reaction time has very little or no influence on the reaction conversion. Increasing the mass fraction of the catalyst and the molar ratio of alcohol to oil generally leads to a higher reaction conversion. As the molecular weight of the alcohol increases, the polarity of the alcohol decreases, and ultimately of the alkoxide anion, which plays a major role in the base transesterification mechanism. As the polarity of the alkoxide anion decreases, its affinity towards the ester group of triglycerides also decreases, and thus the conversion of the reaction decreases. |
