| Abstract | Klimatske promjene i globalno zatopljenje teme su brojnih rasprava koje se u zadnjem desetljeću vode unutar znanstvene zajednice, ali i cijelog društva. Jedan od čimbenika koji je imao značajan utjecaj na količinu ugljičnog dioksida u atmosferi je i prekomjerno korištenje fosilnih goriva. Zbog toga se sve više javlja potreba za pronalaskom alternativnih i po okoliš neutralnih izvora energije. Jedan od takvih energenata je i biodizel koji se dobiva iz prirodnih izvora te se stoga smatra obnovljivim izvorom energije. U odnosu na dizel fosilnog podrijetla, emisije neizgorjelih ugljikovodika nastalih primjenom biodizela u motorima s unutarnjim izgaranje su niže za 75-90%. Također, metilni esteri koji su osnovna sastavnica biodizela poboljšavaju svojstvo mazivosti što smanjuje trošenje dizelskih motora i produljuje njihov vijek trajanja. Biodizel se najčešće proizvodi procesom transesterifikacije, u kojem kemijskom reakcijom biljnog ili životinjskog ulja/masti s alkoholom uz prisustvo katalizatora, kao produkti nastaju biodizel i glicerol. Osim glicerola, biodizel proizveden transesterifikacijom sadržava tragove alkohola, sapuna, katalizatora, vodu, metale, ulje i gliceride koje je potrebno ukloniti da bi biodizel bio pogodan za korištenje u motorima s unutarnjim izgaranjem. Najčešće korištena industrijska metoda za pročišćavanje biodizela je mokro pranje. Osnovni nedostatak ove metode je u tome što se za proizvodnju 1 L pročišćenog biodizela troši približno 10 L vode, što je ekonomski i ekološki neprihvatljivo, jer je uz velik utrošak vode, otpadnu vodu koja u ovom procesu nastaje potrebno pročistiti prije ispuštanja u okoliš. Kao jedna od tehnika pročišćavanja biodizela koja ne uključuje upotrebu vode (suho pranje biodizela) sve više se koristi membranska separacija koja podrazumijeva primjenu različitih polupropusnih membrana. U ovom radu je pročišćavanje biodizela provedeno membranskom ultrafiltracijom. Biodizel je proizveden u mikroreaktoru, procesom transesterifikacije katalizirane enzimom lipaza podrijetlom iz Thermomyces lanuginosus. Analizirana su četiri potpuno integrirana sustava za proizvodnju i pročišćavanje biodizela koja su se sastojala od serijski spojenog mikroreaktora i membranskog separatora. Pri optimalnim uvjetima provedbe procesa postignuti su iskorištenje biodizela od 90,7% i maseni udio glicerola u pročišćenom biodizelu od 0,025% za vrijeme zadržavanja od 20 minuta. Na ovaj način proizvedeni biodizel ne udovoljava pokazateljima norme EN 14213:2013 koja propisuje kvalitetu biodizela te su potrebna daljnja istraživanja kako bi ovaj potpuno integrirani proces unaprijedio. |
| Abstract (english) | Climate change and global warming have been the subject of numerous debates in the last decade within the scientific community and society as a whole. One of the factors that has a significant impact on the amount of carbon dioxide in the atmosphere is the excessive use of fossil fuels. As a result, there is a growing need to find alternative and environmentally neutral energy sources. One of such energy sources is biodiesel, which is obtained from natural raw materials and is therefore considered a renewable energy source. Compared to diesel of fossil origin, emissions of unburned hydrocarbons generated by the use of biodiesel in internal combustion engines are lower by 75-90%. Also, methyl esters, which are a basic component of biodiesel, improve the lubricity, which reduces the wear of diesel engines and prolongs their service life. Biodiesel is most often produced by a transesterification process, in which the chemical reaction of vegetable or animal oil / fat with alcohol in the presence of a catalyst results with biodiesel and glycerol as products. In addition to glycerol, biodiesel produced by transesterification contains traces of alcohol, soap, catalysts, water, metals, oil and glycerides that need to be removed to make biodiesel suitable for use in internal combustion engines. The most commonly used industrial method for purifying biodiesel is wet washing. The main disadvantage of this method is that the production of 1 L of purified biodiesel needs approximately 10 L of water, which is economically and environmentally unacceptable, because with high water consumption, wastewater generated in this process must be treated before discharge in environment. As one of the biodiesel purification techniques that does not involve the use of water (dry washing of biodiesel), membrane separation is increasingly used, which involves the use of different semi-permeable membranes. In this paper, the purification of biodiesel was performed by membrane ultrafiltration. Biodiesel was produced in a microreactor, a process of transesterification catalyzed by the enzyme lipase originating from Thermomyces lanuginosus. Four fully integrated biodiesel production and purification systems consisting of a microreactor and a membrane separator serially connected were analyzed. Under optimal process conditions, the biodiesel yield of 90.7% and the glycerol mass fraction in purified biodiesel of 0.025% for the retention time of 20 minutes were achieved. The biodiesel produced in this way does not meet the criteria of the standard EN 14213:2013, which prescribes the quality of biodiesel. Therefore, further research is needed to improve this fully integrated process. |
