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Limited reserves of fossil fuels as well as the growing concern for the environment, has led to a worldwide search for renewable energy sources, among which biodiesel, a mixture of fatty acid methyl esters (FAME), is one of the most perspective alternative fuels since it is a non-toxic and can be produced from different renewable sources through simple cost-effective alcoholysis, while being compatible with existing infrastructures. Vegetable oils, as renewable in nature and environmentally friendly, with a possibility to be produced on a large scale, represent a promising feedstock for biodiesel production. In this chapter, a comprehensive review of different vegetable oils as a feedstock for biodiesel synthesis is reported, including edible and non-edible oils, as well as waste vegetable oils. Selection of feedstock for biodiesel production mainly depends on the specific conditions and circumstances in some region (climate, presence of certain crops, the economic development of a country, etc.). Various fatty acid compositions of triacylglycerols directly determine the quality and fulfillment of the standards of biodiesel. One of the crucial points which determine technology route for biodiesel synthesis is content of free fatty acids (FFA) which might be present in vegetable oils, as well as the presence of water and other compounds. Also, many analysis performed in the past have shown that the production cost of biodiesel is mainly determined by the price of used feedstock, which represents 70-80% of total production costs of biodiesel. Currently more than 95% of feedstock comes from edible oils since they are easily accessible, consists mainly of triacylglycerols, whereby the properties of biodiesel produced from these oils are suitable to be used as diesel fuel substitute. Most commonly used edible oils for biodiesel production are rapeseed, soybean, sunflower and palm. However, for economic and social reasons, in recent years research and development of biodiesel production has focused on other sources of triacylglycerols, in order to replace edible oils by lower-cost non-edible plant oils and the waste cooking oils, feedstocks that are unsuitable for human consumption. Properties of different oils and biodiesel obtained from them as well as the technologies suitable for biodiesel synthesis are compared in this chapter. The wellknown fact is that the conventional and to-day widely applied homogeneous method of biodiesel synthesis is sensitive to the presence of impurities in the oil, primarily the presence of FFA and water. Furthermore, biodiesel synthesis is followed by creation of large amount of wastewater produced during neutralization of catalyst and purification of final product. The drawbacks of a homogeneous process can be avoided by applying technologies based on utilization of heterogeneous catalyst or by application of the noncatalytic supercritical process of biodiesel synthesis. These technologies for biodiesel production were also analyzed and compared.

Increased environmental concern and awareness of limited reserves of fossil fuels gave a great importance to alternative and renewable energy sources over the past couple decades. An excellent substitute for mineral diesel fuels is biodiesel, a mixture of fatty acid methyl esters (FAME), made by alcoholysis of different triacylglycerols (TAG) from various renewable sources (vegetable oils or animal fats) in the presence of a homogeneous or heterogeneous catalyst. Drawbacks of homogeneously catalyzed alcoholysis, to-day the most commonly used commercial biodiesel production process, have shifted the research focus on technologies based on utilization of solid catalyst. Heterogeneously catalyzed alcoholysis is more environmentally friendly, offers simplified production and improved process efficiency, allowing the possibility of catalyst’s regeneration, too. This technology of biodiesel synthesis is also the base for the continuous process development. Although great attention has been paid to the development of a catalyst that will have good activity and stability, followed by cheap method of synthesis, this task is still a challenge and needs further intensive research. Solid base catalysts have been characterized by high activity under mild reaction conditions and short reaction times, however, due to their sensitivity to the presence of impurities in the oil, primary the presence of free fatty acids (FFA) and water, they were not suitable, according to results of many investigations, for transesterification of lower-cost feedstock, such as non-edible plant oils and the waste cooking oils. For these feedstocks heterogeneous biodiesel synthesis should be performed applying solid acid catalyst. Despite the generally lower activity compared to solid base catalysts and higher reaction temperatures required for transesterification of oils into biodiesel, the main advantage of solid acids is their ability to simultaneously carry out esterification of FFA and transesterification of TAG. It is the main reason why application of solid acids for biodiesel production became a growing field of research during the last few years. In the present chapter, a comprehensive review of different solid acids used for biodiesel synthesis is presented. The method of catalyst preparation, type of precursor and employed calcination temperature greatly affect the acid catalyst activity and its final properties. The concentration of catalytic sites along with other characteristics, like surface area and catalyst porosity, are of great importance for catalytic activity of solid acids. The solid acids synthesis procedures and main catalyst’s characteristics are also analyzed in details, as well as the activity of solid acid catalysts in transesterification of different feedstock, with the emphasis on the lower-quality materials with high FFA content. One of the problems associated with heterogeneous catalysts is their deactivation with time due to poisoning, sintering or leaching of the active components, thus the attention in this review is also devoted to this issue. Furthermore, the transesterification process kinetics, being fundamental to reactor design and optimization of operational conditions in order to achieve maximum yield and lower cost of the process, is discussed.

The kinetics of heterogeneous methanolysis of sunflower oil was studied at 60 °C using mechanochemically synthesized CaO·ZnO as catalyst. The influence of agitation speed, catalyst amount, and methanol-to-oil molar ratio on the rate of reaction was analyzed. The rate of the process depends on the two resistances - mass transfer of triglycerides to the catalyst surface and chemical reaction on the catalyst surface, which are defined as the values of the overall triglyceride volumetric mass transfer coefficient, kmt,TG, and the effective pseudo first-order reaction rate constant, k, respectively. These kinetic parameters actually determine the value of the apparent reaction rate constant, kapp, the time dependence of which is defined by the change of triglyceride (TG) conversion. A kinetic model is proposed and the model parameters are determined. Kinetika heterogene metanolize suncokretovog ulja je ispitivana na 60 °C korišćenjem CaO·ZnO katalizatora koji je sintetizovan mehanohemijskim putem. Analiziran je uticaj intenziteta mešanja, mase korišćenog katalizatora u sintezi i različitog molskog odnosa metanola i ulja na brzinu metanolize. Brzina procesa metanolize zavisi od dva otpora - otpora prenosu mase triglicerida do površine katalizatora i otpora brzini hemijske reakcije na površini katalizatora. Oba otpora određuju vrednost ukupnog zapreminskog koeficijenta prenosa mase triglicerida, kmt,TG, odnosno efektivne vrednosti konstante brzine hemijske reakcije pseudo-prvog reda, k. Ovi kinetički parametri određuju vrednost prividne konstante brzine procesa metanolize, kapp, koja se menja sa vremenom u zavisnosti od ostvareneog stepena konverzije triglicerida (TG). Predložen je odgovarajući model kojim je moguće definisati brzinu metanolize i određeni su odgovarajući parametri ovog modela.

The kinetics of heterogeneous methanolysis of sunflower oil and used vegetable oil were studied at different temperatures, ranging from 60 to 96 degrees C using CaO center dot ZnO as catalyst (2 wt% on the basis of oil) and methanol to oil molar ratio of 10:1. Heterogeneous CaO center dot ZnO catalyst was synthesized by mechanochemical treatment of CaO and ZnO powder mixture with the addition of water necessary for the formation of corresponding mixed hydroxides, and their calcination at 700 degrees C in air. It was shown that kinetics of overall process could be described as pseudo-first order reaction. For the sunflower oil methanolysis at 60 and 70 degrees C, the rate of process at the beginning of biodiesel synthesis was limited by triglycerides mass transfer to the catalyst surface, and after that it is governed by the rate of chemical reaction at catalyst surface. At higher temperatures the influence of mass transfer resistance is almost negligible implying that the rate of chemical reaction determines the overall kinetic of biodiesel synthesis. In the case of used vegetable oil, the influence of mass transfer resistance was not observed either at higher or lower temperature. The kinetic model that describes the whole process well was proposed, and it comprises both the triglycerides mass transfer and chemical reaction controlled regime. The overall volumetric mass transfer coefficient was defined, assuming that it depends on the conversion of triglycerides.

The transesterification of triglycerides (vegetable oil) with methanol using CaO center dot ZnO mixed oxides catalyst were conducted to produce FAME (Fatty Acid Methyl Esters, i.e. biodiesel). Catalyst was synthesized by ball milling of CaO and ZnO powder mixture (using molar ratio of CaO and ZnO of 1:2 and 1:4) with the addition of water, as well as solely by ball milling (molar ratio of 1:2) of mentioned powders and subsequent. After ball milling prepared mixtures were calcinatied at 700 degrees C in air atmosphere. The samples of formed catalysts were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The particle size distribution as well as the base strength using Hammett indicator was determined, too. CaO. ZnO catalysts were used in the methanolysis of sunflower oil, at 60 degrees C and 1 bar, using molar ratio of sunflower oil to methanol of 1:10 and with 2 wt% of catalyst based on oil weight. All catalysts exhibited good activity in the methanolysis of sunflower oil, with the yield of FAME above 90 % after 4 hours of reaction.

A large interest in research as well as dramatically increased number of scientific papers covering this topic evidently exists. This chapter covers the literature review of biodiesel production under specific conditions (high pressure and high temperature) indicating the permanent trend in the field of biodiesel technology development. It will focus on the following: 1. The problems in design and detailed analyses of energy consumption Until now there have been several papers with the same topic "design of biodiesel production". The first part of this chapter will focus on "design problems" which have not been well explained or analyzed in recently published papers. They will be summarized indicating the best solution for solving specific design problems (application of EOS, thermodynamic properties under high pressure and temperature, degree of conversion, products purity). 2. The best route for reducing the energy consumption On the basis of a realistic approach and performed analyses of energy consumption necessary for methanolysis of vegetable oil performed under different conditions, the best solution will be recommended in the second part of this chapter. 3. Techno-economical analysis of supercritical synthesis On the basis of techno-economical analysis, we will show that biodiesel production at supercritical condition of methanol represents the competitive technology to the homogeneous alkali catalysed alcoholysis today widely used in many industrial plants. Moreover, we will point out that biodiesel production at supercritical alcoholysis has significant advantages regarding impact to the environment because there is no formation of side products (salts, waste water). Furthermore, application of supercritical alcoholysis gives almost the pure products (biodiesel and glycerol) which can be easily separated in the final stage of synthesis which has the main influence on the techno-economical aspect of biodiesel production.

In this study, catalysts for fatty acid methyl esters (FAME or biodiesel) synthesis with K2CO3 as the active component on an alumina/silica support were synthesized using the sol-gel method, which was followed by drying the 'dense' wet gels with supercritical carbon dioxide to obtain the aerogels. The prepared catalysts were characterized by XRD analysis, FTIR spectroscopy and N2 physisorption at 77 K, and tested in the methanolysis of sunflower oil. The effects of reaction variables, such as reaction time, temperature and methanol to oil molar ratio, on the yield of FAME were investigated. The aerogel catalysts with K2CO3 as the active component on an alumina/silica support exhibited good activity in the methanolysis of sunflower oil. The leaching of potassium when the catalyst was in contact with pure methanol under the working conditions of methanolysis was also tested in this study, indicating that it occurred only at higher temperatures, while at lower ones, it was negligible. U ovom radu katalizator za sintezu metil estara masnih kiselina (MEMK ili biodizel) sa K2CO3 kao aktivnom komponentom na alumosilikatnom nosaču sintetizovan je sol-gel metodom nakon čega je dobijeni gel sušen uz prisustvo natkritičnog ugljen dioksida da bi se dobio aerogel. Za karakterizaciju sintetizovanih katalizatora korišćene su metode XRD, FTIR i N2 fizisorpcija na 77 K i katalizatori su testirani u reakciji metanolize suncokretovog ulja. Katalizator je testiran u reakciji metanolize suncekrotovog ulja i sintezi MEMK. Ispitan je uticaj različitih parametara kao što su vreme, temperatura i molarni odnos metanol : ulje na prinos MEMK. Aerogel katalizator sa K2CO3 kao aktivnom komponentom na alumosilikatnom nosaču pokazao je dobru katalitičku aktivnost u reakciji metanolize suncokretovog ulja. Izluživanje kalijuma u kontaktu sa metanolom na radnim uslovima metanolize takođe je testirano u ovom radu, pokazujući da ono postoji na višim temperaturama, dok je na nižim zanemarljivo.

Biodiesel, the most promising alternative to diesel fuel, is renewable, biodegradable, environmentally friendly and can be used in existing engines. Certain disadvantages of conventional processes of biodiesel, i.e. fatty acid methyl esters (FAME) synthesis could be avoided by applying new technologies which are based on using heterogeneous catalyst under moderate and high temperatures and pressures. Heterogeneous catalyst is easily removed from the products of reaction, making purification and neutralization process much simpler. Beside the fact that synthesis becomes less problematic for environment, it can also improve the economics of biodiesel production and lead to cheaper production costs. In this study a new type of heterogeneous catalyst with K2O as active component on alumina/silica support is synthesized. A starting step when producing catalyst (aerogel and xerogel) is a sol-gel synthesis, method that provides a possibility to add different catalyst constituents in only one step. It is followed by drying of the wet gel: drying at elevated temperature and atmospheric pressure to obtain xerogel and supercritical drying with supercritical carbon dioxide to obtain aerogel. Prepared catalysts were used in the methanolysis of sunflower oil at 200˚C and 37 bar with molar ratio methanol:oil 30:1 and 2 wt% of catalyst (based on oil). For the catalysts that showed better activity the possibility to optimize the process of FAME synthesis was investigated. The efficiency of process under different temperatures (80-200°C), reaction times (15min-8h) and molar ratios of methanol to oil (6:1-30:1) was analyzed. With the yield of FAME over 93% after 15 minutes, some catalysts showed very good activity and are promising catalysts for FAME synthesis. . Određeni nedostaci konvencionalnih načina sinteze biodizela, tj. metil estara masnih kiselina (MEMK) mogu se izbeći primenom novih tehnologija koje se baziraju na korišćenju heterogenih katalizatora. U ovom radu novi tip heterogenog katalizatora sa K2O kao aktivnom komponentom na alumosilikatnom nosaču je sintetizovan sol-gel postupkom. Dobijeni katalizatori korišćeni su u reakciji metanolize suncokretovog ulja. Ispitana je efikasnost procesa pri različitim temperaturama (80-200°C), vremenu trajanja reakcije (15min-8h) i molarnom odnosu metanol:ulje (6:1-30:1). Sa prinosom MEMK od preko 93% za 15 minuta, pojedini katalizatori pokazali su se kao veoma aktivni i efikasni katalizatori za proces sinteze MEMK. .

The publisher regrets the error in the title of this article. The correct title is printed above. Related to: [https://doi.org/10.1016/j.seppur.2005.09.012]

Certain disadvantages of conventional processes of biodiesel, e.g., fatty acid methyl esters (FAME) synthesis could be avoided by applying new technologies that are based on using heterogeneous catalyst. A new type of heterogeneous catalyst with potassium-oxide or zinc-oxide as active component on alumina/silica support was synthesized using sol-gel method which was followed by drying. Heterogeneous catalyst with potassium-oxide or zinc-oxide as active component on alumina/silica support exhibited good activity in the methanolysis of sunflower oil. Using catalyst with potassium-oxide as active component, the achieved conversion of vegetable oil to FAME was realized after 15 min of reaction. This type of catalyst could be potentially very good in heterogeneous biodiesel synthesis. This is an abstract of a paper presented at the 2007 AIChE Annual Meeting (Salt Lake City, UT 11/4-9/2007).

Certain disadvantages of conventional processes of biodiesel, i.e. fatty acid methyl esters (FAME) synthesis could be avoided by applying new technologies which are based on using heterogeneous catalyst. In this study a new type of heterogeneous catalyst with potassium-oxide or zinc-oxide as active component on alumina/silica support was synthesized using sol-gel method which was followed by drying: at elevated temperature and atmospheric pressure (xerogel) or with the supercritical carbon dioxide (aerogel). Prepared catalysts were used in the methanolysis of sunflower oil. The effects of various reaction variables such as reaction time, temperature and methanol to oil molar ratio on the yield of FAME were investigated. The catalysts were characterized with XRD, FTIR and BET surface area analysis. The results indicated that active component is the main reason for the catalytic activity towards the reaction. It has been determined that the temperature of 393 K and methanol:oil molar ratio of 15:1, are optimal conditions for fatty acid methyl esters synthesis with potassium-oxide as active component of the heterogeneous catalyst. At these conditions, after 15 min the yield of fatty acid methyl esters was above 92%.

In this study the compositions of Carrot fruit (Daucus carrota, cultivar Chanteney) essential oil obtained by hydrodistillation and its extract obtained by supercritical carbon dioxide extraction at 313 K and 10 MPa were examined. The qualitative and quantitative analyses of the essential oil and supercritical extract were performed using GC and GC/MS methods. Mathematical modeling of experimental results obtained by supercritical extraction at 313 K and 10 MPa with different particle size, as well as at 323 K and 9 MPa was also performed. GC/MS analysis showed that in the case of both, hydrodistillation and supercritical extraction, the main component of carrot oil was carotol. However, the composition, as well as the yield of obtained oil was different depending on applied technique of extraction/distillation. The yield of essential oil of 0.69 wt% was obtained by hydrodistillation, while extraction with CO2 under supercritical conditions (at 313 K and 10 MPa) gave yield of 1.17 wt%. The main reason for this difference was that heavier compounds like olerosines and waxes were also extracted by supercritical CO2 and not only the essential oil. Moreover, the lighter compounds like pinenes were not found in the supercritical extract. Obtained yields by supercritical fluid extraction were higher at higher pressures and lower temperatures. Results of supercritical extractions showed that particle size had no influence on the extraction yield. It seems that plant structure which contains secretory ducts as oil reservoirs, proved by SEM (Scanning Electron Microscopy) is responsible for such influence of particle size on the extraction yield. Mathematical modeling of supercritical extraction results included the application of a new model based on the secretory structure (MSS) of carrot fruit. Model showed good agreement with experimental results, and confirmed that particle size had no influence on the yield. This model had been previously used to predict similar behavior in the case of other plant materials with same structural characteristics.

General model for the supercritical carbon dioxide extraction of essential oils on the secretory structure scale (micro-scale) is presented in this study. The model containes Source and Transfer term which describes mass transfer from specific secretory structure. Modelling results for each specific type of secretory structure are presented. Mathematical modelling on the micro-scale and process simulation also pointed out how the process of supercritical fluid extraction should be conducted or which type of pretreatment should be performed, referred to the secretory structure behavior during the extraction. The advantage of mathematical modelling on the micro scale is that it reveals phenomena on the secretory structure scale and indicates possibilities for process optimization.

The main sources of oily waste water are oil- refineries, metal industry and food industry. Any technological process that uses emulsions has to take into consideration also the treatment of the used emulsions. The ultimate goal of emulsion treatment is to separate oil from water, and to attain maximum levels of cleanliness of both water and oil. The paper analyzes the possibility of emulsion separation with the use of the freeze/thaw (F/T) method, and the microwave radiation (MWR) assistance method. The F/T method and MWR are relatively new physical methods for de-emulsification, and they have the advantage of belonging to the group of green methods that are reagent-less and ecologically friendly. U radu je dat pregled metoda za prečišćavanje otpadnih voda. Predmet istraživanja rada je analiza i primena savremenih metoda za demulzifikaciju, odnosno uklanjanje ulja iz vode. Glavni izvori zauljenih otpadnih voda su rafinerije nafte, proizvodnja / obrada metala i proizvodnja hrane. U skladu sa ekološkim zahtevima svaki tehnološki proces u kome se koriste emulzije ulja u vodi mora da bude praćen odgovarajućom obradom otpadne ili iskorišćene emulzije. Cilj obrade je uklanjanje zagađivača (ulja) i dobijanje vode odgovarajuće čistoće. U ovom radu je istražena mogućnost prečišćavanja emulzija metodom naizmeničnog hlađenja / zagrevanja i metodom hlađenja praćenog mikrotalasnim zagrevanjem. Metode ispitane u ovom radu su nedestruktivne, pripadaju fizičkim metodama analize i primenjuju se bez dodavanja hemijskih reagenasa čime je ostvaren koncept ekološki prihvatljivih ("zelenih") metoda za obradu zauljenih otpadnih voda.

The performed investigations were directed toward the analysis of the performance and activity of the fresh and regenerated Cyanamid HDS 20C catalyst in a laboratory batch reactor (2 dm3) for the HDS of the diesel fraction (light gas oil, LGO). Testing of the regenerated catalyst was performed with light gas oil (LGO) of different characteristics. The determined values of the reaction rate constant were compared to some published data in the literature for the HDS of specific sulfur compounds as well as the values of the activation energy. The rates of deactivation of the fresh and regenerated catalyst actually existed compared to some other results recently published in the literature. However, such an observed differences were not sufficient to derive a relation which could be used for the determination of the rate of catalyst deactivation.

Sol-gel synthesis, and the resulting materials (xerogels and aerogels) are finding increasing application in the synthesis of catalysts, due to their unique characteristics. The most important features of the sol-gel process are: the ability to achieve homogeneity at the molecular level, the introduction of several species in only one step and the ability to stabilize metastable phases. The supercritical drying process produces aerogels with structural features quite different to conventional materials. Some of these characteristics of aerogels can make them very effective catalysts.

The most complex step in the production of aerogels is the supercritical drying step, and it is therefore important to study its dynamics using mathematical models. Alumina/silica aerogel was obtained using a one step sol-gel synthesis and subsequent drying with supercritical carbon dioxide. The wet gel weight change with time was monitored. The dry aerogel sample porous structure was determined using the BET method and nitrogen adsorption/desorption. Supercritical drying of the wet gel sample was represented as the unsteady and one dimensional diffusion of 1-butanol through aerogel pores filled with supercritical carbon dioxide. Different mathematical models describing supercritical drying of the wet gel cylindrical sample were developed. Shrinking core models used one value of the effective diffusivity for the whole material, and they failed to describe the drying experiment correctly. Parallel pore models used different effective diffusivity values for each pore size. The best simulation results were obtained using the parallel pore model with local porosity or tortuosity values for each pore size. Najsloženiji postupak u procesu dobijanja aerogelova predstavlja natkritično sušenje. U cilju ispitivanja dinamike i optimizacije procesa natkritičnog sušenja neophodno je proces opisati odgovarajućim matematičkim modelom i izvršiti njegovu simulaciju. Sintetizovan je alumosilikatni gel sa cink hloridom (katalizator za reakcije alkilacije) jednostepenim sol-gel postupkom. Eksperimentalna kriva sušenja mokrog gela sa natkritičnim ugljen dioksidom je dobijena merenjem promené mase gela sa vremenom u toku sušenja. Porozna struktura gela je karakterisana BET metodom i adsorpcijom/desorpcijom azota na 77 K. Razvijen je matematički model koji opisuje nestacionarnu jednodimenzionu difuziju rastvarača (1-butanola) kroz pore aerogela napunjene nadkritičnim ugljen dioksidom. Najvažniji parametar modela predstavlja efektivna difuzivnost. Na osnovu načina izračunavanja efektivne difuzivnosti dobijeno je nekoliko varijanti matematičkog modela. Prva dva modela su modeli sa neosušenim jezgrom, a koriste jednu vrednost efektivne difuzivnosti. Ovi modeli nisu dali dobro slaganje sa eksperimentalnim podacima. Zbog ove činjenice, kod modela sa paralelnim porama iskorišćeni su podaci o poroznoj strukturi aerogela tj. o raspodeli zapremine pora po veličini pora. Modeli sa paralelnim porama podrazumevaju da poroznu strukturu aerogela čine paralelne pore različitih dimenzija koje se istovremeno suše, ali imaju različite vrednosti za efektivne difuzivnosti u zavisnosti od dimenzija pora. Najbolje slaganje rezultata simulacije sa eksperimentalnim podacima nadkritičnog sušenja, dobijeno je sa modelom paralelnih pora kod koga su različite vrednosti efektivne difuzivnosti dobijene na osnovu različitih vrednosti za lokalne poroznosti ili lokalne izuvijanosti za pore različitih veličina.

Residual pyrolysis oil (RPO) produced as a by-product of naphtha steam pyrolysis was hydrogenated (160-280°C; 60 bar; trickle-bed reactor with Co-Mo/y-AlgOs) with the aim of suppressing the polymerization of the unsaturated compounds present in the oil (styrene, (-methylstyrene, 4-, 5- and 6- methyl-indene and others) which give a highly aromatic resin. The influence of temperature on the rate of hydrogenation was investigated at a constant liquid space velocity (LHSV) of 1 h-1 and hydrogen/oil ratio of 600 Nm3/m3, while the influence of liquid space velocity (1-3h-1) was analyzed at 200°C and 60 bar at the same hydrogen/oil ratio. GC and GC-MS analysis of the hydrogenated oil were carried out on the hydrogenated sample, as well as viscosity measurements, which showed that no polymerization occurred in the case of stabilized (hydrogenated) oil. The optimal hydrogenation temperature and LHSV values were 220°C and 1h-1 respectively. The result of the longterm hydrogenation test was used to study the kinetics of the catalyst deactivation process by determining the rate constants in the case of indene, 4-methyl-indene and 5- and 6-methyl-indene hydrogenation. Using the obtained rate constants, the conversion of the above compounds was mathematically simulated showing satisfactory agreement with the experimentally obtained values. Ispitivano je hidrogenovanje pirolitičkog ulja koje nastaje pri proizvodnji etilena (piroliza primarnog benzina, prinos 0,2 t/t). Ovo ulje ključa u intervalu temperatura 180-280°C a ima gustinu 1,05 g/cm3, i sadrži u najvećoj meri naftalen i njegove supstituisane derivate ali i druga jedinjenja stirenske, odnosno indenske strukture. Hidrogenovanjem se može sprečiti pojava polimerizacije prisutnih nezasićenih jedinjenja u ovom ulju kao što su stiren, a-metilstiren, 4-, 5- and 6- metil-inden pri čemu nastaju smole sa pretežno aromatskim strukturama. Pre nego što se pristupi izdvajanju naftalena iz pirolitičkog ulja, a u cilju sprečavanja njegove polimerizacije neophodno je ovo ulje stabilizati hidrogenovanjem. Ovo se postiže uz pomoć Co-Mo katalizatora na relativno niskim pritiscima i temperaturama (60 bar; 200-280°C). U ovom radu ispitivan je uticaj temperature i prostorne brzine na brzinu hidrogenovanja sa ciljem da se utvrde osnovni kinetički i hidrodinamički parametri pri korišćenju protočnog reaktora sa nepokretnim slojem katalizatora. Hidrogenovanje je u prvoj fazi ispitivano pri konstantnoj prostornoj brzini ulja (LHSV = 1 h~1) i odnosu vodonik/ulje (600 Nm3/m3) prated efekte na temperaturama od 160 do 280°C. Zatim je za izabranu temperaturu (200°C) i isti odnos vodo-ni/ulje ispitivan uticaj prostorne brzine (1, 1,5 i 3 h). Gasna hromatografija, GC-MS analiza i određivanje viskoziteta ulja su iskorišćeni za identifikaciju sastava pirolitičkog ulja i njegove promene tokom hidrogenovanja. Relativna stabilnost viskoziteta hidrogenovanog pirolitičkog ulja ukazuje u kojoj meri je ulje stabilizovano i sprečene neželjene reakcije polimerizacije nezasićenih aromatskih jedinjenja.

Glavni problem za širu primenu metil estara masnih kiselina (biodizela) je njihova visoka cena proizvodnje. Proizvodna cena biodizela bi mogla da se smanji kako smanjenjem cene sirovina (biljnih ulja, životinjskih masti, korišćenih ulja) tako i primenom efikasnijih tehnologija za njegovu proizvodnju. Da bi se tehnologija sinteze biodizela, koja se danas najviše primenjuje u industrijskim uslovima, poboljšala ili eventualno predložila nova, neophodno je da se sam reakcioni sistem jasno definiše. U ovom radu je analizirana sinteza u natkritičnim uslovima, definisana fazna ravnoteža sistema triglicerida i metanola, kao i njihovih proizvoda, metil estara, diglicerida, monoglicerida i glicerola. Metodom doprinosa grupa izračunati su kritični parametri i na osnovu eksperimentalnih podataka rastvorljivosti triglicerida u metanolu u natkritičnim uslovima i njihovom regresijom na više temperature i pritiske, definisan je termodinamički model, koji najbolje opisuje ponašanje analiziranog sistema. Simulacijom u programskom paketu ASPENplus analizirano je ponašanje ovako kompleksnog sistema, ravnoteža i broj faza tokom reakcije metanolize. U zavisnosti od reakcionih uslova, pritiska i temperature, kao i molskog odnosa metanol – ulje, predloženi su kinetički modeli i određeni kinetički parametri reakcije metanolize triglicerida u subkritičnim i natkritičnim uslovima. Ovako definisani kinetički modeli su potvrdili postojanje promene faza, odnosno broja faza u reakcionom sistemu u zavisnosti od temperature i pritiska. Sa definisanim termodinamičkim parametrima i kinetičkim modelom, izvršena je simulacija procesa natkritične proizvodnje biodizela i ovaj postupak sinteze upoređen sa homogeno katalizovanom metanolizom triglicerida. Dobijeni rezultati ukazuju da je proizvodnja biodizela u natkritičnim uslovima konkurentna i realno primenljiva u industrijskim uslovima. Na osnovu detaljne analize i simulacije procesa ukazani su nedostaci postojeće klasične tehnologije zasnovane na primeni alkalnog katalizatora. Takođe, ukazano je da če se buduća industrijska proizvodnja biodizela zasnivati na primeni heterogenog katalizatora. The main obstacle for wider application of biodiesel is its relatively high cost. This is still the truth, although the price gap between petroleum based diesel fuel and biodiesel is narrowing due to the recent increase of crude oil prices. The overall cost of biodiesel fuel could be reduced either by the reduction of raw material cost (vegetable oil, animal fat, used vegetable oil) or by the application of more efficient processing technology. For the further development of biodiesel production technology or application of some advance and new technology, it is necessary clearly defined the reaction system. In this study it was detailed defined the phase equilibria for the system triglycerides and methanol as well as for their products (methyl esters, diglycerides, monoglycerides and glycerol). It was calculated the new value for the critical parameters based on group contribution method. Regression of experimental data for solubility of triglycerides in methanol in subcritical conditions and simulation to higher temperature and pressure, it was define the thermodynamic model which truly describe such system (RK-Aspen equation of state). Simulation with ASPENplus software it was defined the behavior of such complex system during the reaction of methanolysis of triglycerides. The phase content and phase transition was clearly described, also. Kinetic model and kinetic parameters of methanolysis reaction in subcritical and supercritical conditions are proposed in dependenc of temperature and pressure and methanol to oil molar ratio. Such defined the kinetic model was matched and have explanation with the phase equilibria of analyzed system (the number of phases for subcritical and supercritical conditions for reaction). Furthermore, with defined therodinamic and kinetic data, it was performed the process design for the supercritical production of biodiesel. The obtained results are comperd with design’s data for the clasicaly production of biodiesel (alkali homgenious catalysed reaction). There are compared by process parameter and process unit as well as by energy consumption. The obtained result of such analyses showed that biodiesel production at supercritical methanol represents the competitive technology for biodiesel production, and not only competitive with classical one (homogeneous alkali catalysed alcoholysis) but even less energetic required, what have influence on biodiesel price. Based on this design it was pointed the unsufficiences of classic biodiesel technologu as well as their solutions. The end of this study is focused on determination the best route for reducing the energy consumption in biodiesel production at supercritical condition. It was shown that future technology must be mainly based on use of heterogeneous catalyst at moderate pressure and temperature as well as at optimal molar ratio of methanol and oil.

Cilj ove doktorske disertacije je postavljanjematematičkog modela složenog trofaznog reakcionogsistem za epoksidovanje sojinog ulja in situ formiranompersirćetnom kiselinom iz sirćetne kiseline i vodonikperoksida u prisustvu jonoizmenjivačke smole kaokatalizatora. Model uzima u obzir koncentracijereaktanata i produkata u vodenoj i uljnoj fazi. Poredosnovnih reakcija stvaranja persirćetne kiseline iepoksida, model obuhvata i sporednu reakciju otvaranjaepoksi prstena sa sirćetnom kiselinom. Za modelovanjereakcije formiranja persirćetne kiseline na površinikatalizatora primenjeni su Langmuir-Hinshelwood-Hougen-Watson i Rideal-Eley postulati. Postavljenitrofazni model predstavlja sistem običnih diferencijalnihjednačina prvog reda koji opisuje promenu broja molovakomponenata i funkcionalnih grupa sa vremenomizvođenja procesa epoksidovanja, i sadrži više parametararazvrstanih na kinetičke, termodinamičke i parametre kojise odnose na prenos mase. Parametri modela zavise oduslova izvođenja epoksidovanja i to svi od temperature, aneki i od sastava i inteziteta mešanja.Za konstantu hemijske ravnoteže reakcije nastajanjapersirćetne kiseline je izvedena semiteorijska zavisnostod temperature koja daje vrednosti istog reda veličine iistog smera promene sa temperaturom kao i većinapodataka objavljenih u literaturi.Za izračunavanje koeficijenta raspodele sirćetne kiselineizmeđu uljne i vodene faze potrebno je odrediti zavisnostkonstante fazne ravnoteže tečno-tečno sirćetne kiseline odsastava i temperature. Utvrđeno je da je UNIFAC modelgrupnih doprinosa za koeficijente aktivnosti nepogodanza predskazivanje ravnoteže tečno-tečno. Eksperimentalnipodaci za ovu konstantu ravnoteže su uspešno korelisaniUNIQUAC modelom za koeficijente aktivnosti.Parametri reparametrizovane Arrheniusove zavisnostikonstanti brzina reakcija i konstanti sorpcije učesnikareakcije stvaranja persirćetne kiseline od temperatureodređeni su simultano sa parametrima koji se odnose naprenos mase i sa odnosom koeficijenata raspodelepersirćetne i sirćetne kiseline između uljne i vodene faze,fitovanjem eksperimentalnih podataka epoksidovanjasojinog ulja, tj. minimizacijom sume kvadrata odstupanjaračunskih od eksperimentalno određenih vrednosti jodnogbroja i sadržaja epoksi kiseonika tokom epoksidovanja.Fitovanje je uspešno izvedeno primenom metodeMarquardta, dok su pomenute računske vrednostidobijene numeričkom integracijom sistemadiferencijalnih jednačina modela primenom Runge-Kuttametode IV reda., The objective of this doctoral thesis was development ofmathematical model for complex three-phase reactionsystem for soybean oil epoxidation with peracetic acidformed in situ from acetic acid and hydrogen peroxide in apresence of an ion exchange resin as catalyst. The localconcentrations of components in water and oil phases wereintroduced into the model. In addition to reactions of theperacetic acid and epoxy compound formation, modelconsiders the side reaction of epoxy ring cleavage withacetic acid. Approximate modeling of peracetic acidformation was based on Langmuir-Hinshelwood-Hougen-Watson and Rideal-Eley postulates. Established threephasemodel is a system of ordinary first order differentialequations which describes change of components andfunctional groups amounts with reaction time. Besideskinetic parameters, model comprises the thermodynamicones as well as parameters of mass transfer between the oiland water phase. All model parameters are dependent ontemperature and some additionally on composition andintensity of stirring.A semitheoretical temperature dependency of chemicalequilibrium constant for peracetic acid formation wasestablished. The order of magnitude and temperature trendof the calculated chemical equilibrium constant are inagreement with the most data given in a literature.For calculation of partition coefficient for acetic acidbetween oil and water phase, temperature and compositiondependency of liquid-liquid equilibrium constant for aceticacid is necessary. It was found that UNIFAC model ofgroup contribution was non-applicable for the predictionof the equilibrium constant. The experimental data for theequilibrium constant were, however, successfully fitted byUNIQUAC model.Temperature dependencies of the reaction rate constantsand sorption constants of reactants and products inperacetic acid formation reaction are expressed byreparameterized Arrhenius equation. The parameters ofsuch equation were determined simultaneously with masstransfer parameters and ratio of peracetic acid and aceticacid partition coefficients between oil and water phase byfitting the experimental data i.e. by minimization of leastsum of squares of deviation between the calculated andexperimentally determined iodine value and epoxy oxygencontent . Marquardt method was successfully used to fitthe experimental data. A fourth-ordered Runge-Kuttamethod was applied for integrating the system ofdifferential equations of the model.

The subject of this disertation is the swelling of plant material under the influence of supercritical carbon dioxide, as well as the effects of swelling on the process of supercritical fluid extraction (SFE). The results of experiments on the kinetics of the SFE processes were modeled using a mathematical model on the micro-scale and the Sovova’s model, which quantitatively express, through the parameters of the model, the changes that occur due to the swelling of plant material. The swelling of glandular trichomes of plants of the Lamiaceae family, swelling of hop in the form of ground particles of plant material and industrial granulates, and swelling of the particles of valerian root and rhizome of ginger were observed. The tests were conducted in order to examine the possibility of optimization the SFE process in respect to the consumption of supercritical fluids and energy. For the process of SFE of essential oils from glandular trichomes, a complex mathematical model which includes the cracking time distribution for glandular trichomes was developed. The new model describes the process of SFE with significantly higher accuracy than the existing mathematical models. For extraction at higher pressures the optimal pretreatment of plant material is defined with the goal to achieve significant savings of supercritical fluid. In the case of swelling of hops, the mass transport phenomena in granulates and cones exposed to supercritical fluid in various conditions were considered. The results explained phenomena that occur on industrial scale, especially undesirable hardening of the extraction cake. Process parameters (diffusion coefficients in the solid phase) are described by applying mathematical models to experimental results. In the case of swelling of valerian root and rhizome of ginger, significant savings of supercritical fluid consumption were achieved by choosing the optimal treatment. Process parameters (coefficients of mass transfer through the solid phase) are described by applying mathematical models to experimental results. Tema ove doktorske disertacije je ispitivanje bubrenja biljnog materijala pod uticajem natkritičnog ugljenik(IV)-oksida, kao i efekata koje bubrenje ima na proces natkritične ekstrakcije (NKE). Na rezultate eksperimenata u kojima je praćena kinetika procesa NKE primenjen je matematički model na nivou sekrecione strukture i model Sovove, kako bi se promene do kojih dolazi usled bubrenja biljnog materijala kvantitativno izrazile preko parametara modela. Ispitano je bubrenje glandularnih trihoma biljaka familije Lamiaceae, bubrenje hmelja u vidu mlevenih čestica biljnog materijala i industrijskih granulata, i bubrenje čestica korena odoljena i rizoma đumbira. Ispitivanja su vođena u pravcu optimizacije procesa NKE u odnosu na potrošnju natkritičnog fluida i energije. Za proces NKE etarskih ulja iz glandularnih trihoma razvijen je kompleksan matematički model koji uključuje raspodelu vremena pucanja glandularnih trihoma, koji opisuje proces NKE sa znatno većom tačnošću u odnosu na postojeće matematičke modele. Za ekstrakciju na višim pritiscima definisan je optimalan predtretman biljnog materijala kojim se postižu značajne uštede natkritičnog fluida. U slučaju bubrenja hmelja razmatrani su fenomeni prenosa mase u šišaricama i granulatima hmelja izloženim natkritičnom fluidu na različitim uslovima. Rezultati su objasnili pojave koje se dešavaju na industrijskom nivou, a pre svega nepoželjno očvršćavanje ekstrakcione pogače. Parametri procesa (koeficijenti difuzije kroz čvrstu fazu) opisani su primenom matematičkih modela na eksperimentalne rezultate. U slučaju bubrenja korena odoljena i rizoma đumbira, izborom optimalnog predtretmana ostvarene su značajne uštede natkritičnog fluida. Parametri procesa (koeficijenti prenosa mase kroz čvrstu fazu) opisani su primenom matematičkih modela na eksperimentaln rezultate.

U radu su prikazani eksperimentalni rezultati natkritične ekstrakcije etarskog ulja bobicakleke (Juniperus communis L.) i ulja iz semena uljane tikve golice (Cucurbita pepo L.). Ispitan je uticaj pritiska, temperature, stepena usitnjenosti čestica i protoka natkritičnogugljendioksida na promenu prinosa ulja sa vremenom. U cilju poređenja, usitnjeno seme uljane tikve ekstrahovano je i u ekstraktoru većih dimenzija, NOVA-SWISS, Highpressure extraction plant, kao i heksanom i petroletrom u ekstraktoru tipa Sokslet.Praćena je i promena kvaliteta ekstrakata sa vremenom: u etarskom ulju kleke, GC-FID i GC-MS metodama, određen je relativni sadržaj 50 terpenskih jedinjenja i sve komponente ulja su svrstane u 5 osnovnih grupa (monoterpene, seskviterpene, oksidovane monoterpene, oksidovane seskviterpene i ostale komponente). U tikvinom ulju ekstrahovanom natkritičnim ugljendioksidom određen je masnokiselinski sastav GC-MS analizom, sadržaj tokoferola HPLC analizom, sterola i skvalena GC-MS metodom. Određeni su uslovi koji favorizuju ekstrakciju ispitanih jedinjenja za obe sirovine. Dat je dateljan prikaz matematičkih modela koji se koriste za opisivanje natkritične ekstrakcije etarskih ulja i masnih ulja, počevši od najopštijeg modela koji uključuje diferencijalne bilanse mase za rastvorak u masi natkritičnog fluida, u fluidu unutar pora čestica usitnjenog matrijala i u čvrstoj fazi, koji se uvođenjem određenih pretpostavki pojednostavljuje i svodi na modele koji su izabrani da budu ispitani u okviru ovoga rada. Ispitani su modeli kreireni po analogiji sa hlađenjem vrele kugle u masi fluida, tj. modeli tipa jedne sfere i to: Model jedne sfere-1 (MJS-1), koji pored uticaja koeficijenta efektivne difuzije ulja u materijalu na brzinu prenosa mase uzima u obzir uticaj koeficijenta prenosa mase kroz film natkritičnog fluida oko čestice, pri čemu je njegova vrednost procenjena preko postojećih korelacija; MJS-1 (2 par), u kome je spoljašnji koeficijent prenosa mase uzet kao drugi prilagodljiv parametar modela; MJS-2, gde je koeficijent efektivne difuzije jedini prilagođeni parametar, Model karakterističnog vremena i prošireni model klipnog toka koji je predložila Sovová. Za modelovanje natkritične ekstrakcije ulja semena tikve korišćen je i kombinovani model Honga i sar. Softverskim paketima Mathcad 2001 Professional i Solver dodatka unutar Microsoft Excel 2003, određeni su parametri ispitanih modela u cilju najboljeg slaganja modela sa ekperimentalnim podacima. Za obe ispitane sirovine, među ispitanim modelima, izabrani su modeli koji najbolje opisuju njihovu ekstrakciju natkritičnim ugljendioksidom. Prošireni model klipnog toka koji je predložila Sovová pokazao se podjednako dobrim za modelovanje natkritične ekstrakcije obe sirovine i nešto bolji od ostalih primenjenih modela., This study provides results of supercritical carbon dioxide (SCCO2) extraction of juniper berries (Juniperus communis L.) and pumpkin seeds (Cucurbita pepo L. convar.citrullina) in a laboratorysupercritical fluid extraction apparatus. The influenceof pressure, temperature, particle size and carbon dioxide flow on the extraction kinetics of pumpkin seed oil and juniper berry essential oil was studied. Ground pumpkin seeds were also extracted with supercritical carbon dioxide in NOVA-SWISS, High Pressure Extraction Plant, and with hexane and petroleum ether in a laboratory Soxhlet extractor. This work was also aimed to investigate the evolution of the composition of juniper fruit supercritical CO2 extracts with time, at different extraction pressures and to emphasize the most favorable condition for the extraction of different terpene hydrocarbon groups, reporting the qualitative differences among extracts collected during successive extraction time periods. Juniper berry extracts were analyzed by capillary gas chromatography, using flame ionization (GC-FID) and mass spectrometric detection (GC-MS). More than 200 constituents were detected in the extracts and the contents of 50 compounds were reported in the work. Dependence of the percentage yields of monoterpene, sesquiterpene, oxygenated monoterpene and oxygenated sesquiterpene hydrocarbon groups on extraction time was investigated and conditions that favored the yielding of each terpene groups were emphasized. GC-MS analysis of FAME, prepared by transesterification of pumpkin seed oil with KOH in methanol, was performed. Fatty acid compositions of supercritical CO2 pumpkin seed extract fractions collected in successive time intervals over the course of the extraction were determined. The same fractions were analyzed by high pressure liquid chromatography (HPLC), using diode-array detector (DAD) in order to determine a- and g-tocopherol contents. Sterol and squalene contents were determined by GC-MS analysis, as well. Conditions that favored the yielding of tocopherols, squalene and sterols were emphasized. A general mass transfer model and its simlifications were analysed. Extraction curves were evaluated by “hot sphere” mathematical models SSM-1 (Single Sphere Model 1 – in which the external mass transfer coefficient also influences the extraction profile and film mass transfer coefficients were estimated by the correlations), SSM-1 (2 par) (film mass transfer coefficient is used as the second adjustable parameter), SSM-2 (only effective diffusivity influence is considered), Characteristic time model and by the extended Lack’s plug-flow model given by Sovová. A combined model of Hong et al. was also fitted to the experimental data for pumpkin seed oil SCCO2extractions. Relative merits of the models are demonstrated. Good agreement between the extended Lack’s plug-flow model and the experimental measurements was obtained.

The main obstacle for wider application of biodiesel is its relatively high cost. This is still the truth, although the price gap between petroleum based diesel fuel and biodiesel is narrowing due to the recent increase of crude oil prices. The overall cost of biodiesel fuel could be reduced either by the reduction of raw material cost (vegetable oil, animal fat, used vegetable oil) or by the application of more efficient processing technology. For the further development of biodiesel production technology or application of some advance and new technology, it is necessary clearly defined the reaction system. In this study it was detailed defined the phase equilibria for the system triglycerides and methanol as well as for their products (methyl esters, diglycerides, monoglycerides and glycerol). It was calculated the new value for the critical parameters based on group contribution method. Regression of experimental data for solubility of triglycerides in methanol in subcritical conditions and simulation to higher temperature and pressure, it was define the thermodynamic model which truly describe such system (RK-Aspen equation of state). Simulation with ASPENplus software it was defined the behavior of such complex system during the reaction of methanolysis of triglycerides. The phase content and phase transition was clearly described, also. Kinetic model and kinetic parameters of methanolysis reaction in subcritical and supercritical conditions are proposed in dependenc of temperature and pressure and methanol to oil molar ratio. Such defined the kinetic model was matched and have explanation with the phase equilibria of analyzed system (the number of phases for subcritical and supercritical conditions for reaction). Furthermore, with defined therodinamic and kinetic data, it was performed the process design for the supercritical production of biodiesel. The obtained results are comperd with design’s data for the clasicaly production of biodiesel (alkali homgenious catalysed reaction). There are compared by process parameter and process unit as well as by energy consumption. The obtained result of such analyses showed that biodiesel production at supercritical methanol represents the competitive technology for biodiesel production, and not only competitive with classical one (homogeneous alkali catalysed alcoholysis) but even less energetic required, what have influence on biodiesel price. Based on this design it was pointed the unsufficiences of classic biodiesel technologu as well as their solutions. The end of this study is focused on determination the best route for reducing the energy consumption in biodiesel production at supercritical condition. It was shown that future technology must be mainly based on use of heterogeneous catalyst at moderate pressure and temperature as well as at optimal molar ratio of methanol and oil. Glavni problem za širu primenu metil estara masnih kiselina (biodizela) je njihova visoka cena proizvodnje. Proizvodna cena biodizela bi mogla da se smanji kako smanjenjem cene sirovina (biljnih ulja, životinjskih masti, korišćenih ulja) tako i primenom efikasnijih tehnologija za njegovu proizvodnju. Da bi se tehnologija sinteze biodizela, koja se danas najviše primenjuje u industrijskim uslovima, poboljšala ili eventualno predložila nova, neophodno je da se sam reakcioni sistem jasno definiše. U ovom radu je analizirana sinteza u natkritičnim uslovima, definisana fazna ravnoteža sistema triglicerida i metanola, kao i njihovih proizvoda, metil estara, diglicerida, monoglicerida i glicerola. Metodom doprinosa grupa izračunati su kritični parametri i na osnovu eksperimentalnih podataka rastvorljivosti triglicerida u metanolu u natkritičnim uslovima i njihovom regresijom na više temperature i pritiske, definisan je termodinamički model, koji najbolje opisuje ponašanje analiziranog sistema. Simulacijom u programskom paketu ASPENplus analizirano je ponašanje ovako kompleksnog sistema, ravnoteža i broj faza tokom reakcije metanolize. U zavisnosti od reakcionih uslova, pritiska i temperature, kao i molskog odnosa metanol – ulje, predloženi su kinetički modeli i određeni kinetički parametri reakcije metanolize triglicerida u subkritičnim i natkritičnim uslovima. Ovako definisani kinetički modeli su potvrdili postojanje promene faza, odnosno broja faza u reakcionom sistemu u zavisnosti od temperature i pritiska. Sa definisanim termodinamičkim parametrima i kinetičkim modelom, izvršena je simulacija procesa natkritične proizvodnje biodizela i ovaj postupak sinteze upoređen sa homogeno katalizovanom metanolizom triglicerida. Dobijeni rezultati ukazuju da je proizvodnja biodizela u natkritičnim uslovima konkurentna i realno primenljiva u industrijskim uslovima. Na osnovu detaljne analize i simulacije procesa ukazani su nedostaci postojeće klasične tehnologije zasnovane na primeni alkalnog katalizatora. Takođe, ukazano je da če se buduća industrijska proizvodnja biodizela zasnivati na primeni heterogenog katalizatora.