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Тhe MnCO3/Na silicate (Mn/Na/Si mole ratio of 4.65:1:1.65) catalyst in the form of solid particles with diameter of 0.99–1.99 mm was used as a catalyst for transesterification of soybean oil in batch autoclave at different conditions: 388–468 K, methanol-to-oil mole ratio 12:1–30:1, catalyst amount based on the mass of oil 0–12.5 %. The complete triacylglycerols (TAG) conversion and high yield of fatty acid methyl ester (FAME) was obtained after 1 h at 458 K, methanol-to-oil mole ratio 30:1 and 10 % of catalyst. Kinetics of transesterification process was analyzed by three models: the simple first order irreversible reaction rate, as well as two more complex models recently reported in literature. The catalyst reuse in transesterification process was tested and the average values of 99.0 % of TAG conversion and 97.5 % of FAME yield were obtained after 8 consecutive runs. Different techniques were used to characterize fresh and used MnCO3/Na silicate catalyst. The determined amounts of leached Na (<500 ppm) and Mn (<20 ppm) in biodiesel phase implied that the homogeneous-heterogeneous process influences the catalyst selectivity, whereby leached Na enables the complete transformation of TAG to FAME.

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.

The essential oil of common juniper (Juniperus communis L., from the southern part of Serbia) and its fractions of different composition, as well as commercial antibiotics were used for testing their antimicrobial activity against bacteria, yeast and fungi. The essential oil was produced by hydro-distillation in a pilot plant (130 dm3) and then fractionated by distillation over a column, with 36 theoretical stages, under vacuum (26-66 mbar). The essential oil was also fractionated using pure CO2 or CO2 and methanol as co-solvent under supercritical conditions. The native oil showed weak antimicrobial activity, while the fractions with a high content of α-pinene, and mixture of α-pinene and sabinene showed the highest antimicrobial activity, especially against fungi. In comparison to the commercial antibiotics, the oil fractions showed more extensive spectra of antimicrobial activity, as well as wider inhibition zones. ., Etarsko ulje ploda kleke (Juniperus communis L. iz južnog dela Srbije) dobijeno je hidrodestilacijom u pilot postrojenju (130 dm3) a zatim frakcionisano u destilacionoj koloni, sa 36 teoretskih podova, pod vakuumom (26-66 mbar). Etarsko ulje je takođe frakcionisano korišćenjem čistog CO2 i smeše CO2 i metanola kao kosolventa pod natkritičnim uslovima. Devet različitih uzoraka (etarsko ulje i njegove frakcije različitih sastava) kao i komercijalni antibiotici korišćeni su u testiranju antimikrobne aktivnosti i inhibitornog uticaja na razvoj nekih bakterija, kvasaca i gljivica. Etarsko ulje kleke je pokazalo slabu antimikrobnu aktivnost na svim sojevima a frakcije sa čistim α-pinenom i smešom α-pinena i sabinena naročito na rast gljivica. U poređenju sa komercijalnim antibioticima frakcije etarskog ulja kleke pokazuju širok spektar delovanja kao i veće zone inhibicije. .

The non-catalytic synthesis of biodiesel (fatty acids methyl esters) from triglycerides and methanol proceeds at elevated pressures above 100 bar and temperatures above 523 K. Kinetic investigations of the system revealed an unusual behavior of the reaction rate constant with increasing temperature and pressure. In order to explain this phenomenon, the phase behavior of the triglycerides-methanol mixture was investigated. The phase equilibria of the binary system sunflower oil-methanol were measured at different temperatures between 473 and 503 K, and a range of pressures between 10 and 56 bar. The experimental data were correlated using the Peng-Robinson, Soave-Redlich-Kwong and Redlich-Kwong-Aspen equations of state and different mixing rules. The best results were obtained with the RK-ASPEN equation of state and the Van der Waals mixing rule (VdW), which were then used to calculate the distribution of the phases at pressures and temperatures usual for the non-catalytic synthesis of biodiesel under high pressures. The obtained data indicated a strong influence of the phase equilibria on the reaction kinetics., Sinteza biodizela (metil-estara viših masnih kiselina) iz triglicerida i metanola se odvija bez prisustva katalizatora na uslovima povišenog pritiska, iznad 100 bar, i temperature iznad 523 K. Kinetička ispitivanja ove reakcije su ukazala na neobično ponašanje konstante brzine hemijske reakcije sa porastom temperature i pritiska. U cilju objašnjenja ove pojave ispitivana je fazna ravnoteža sistema trigliceridi-metanol na povišenom pritisku i temperaturi. Ravnoteža faza binarnog sistema suncokretovo ulje-metanol je ispitivana na temperaturama od 473 do 523 K i pritiscima od 10 do 56 bar. Eksperimentalni podaci su korelisani korišćenjem Peng-Robinson, Soave-Redlich-Kwong i Redlich-Kwong-Aspen jednačina stanja uz primenu različitih pravila mešanja. Najbolji rezultati korelisanja eksperimentalnih podataka su dobijeni primenom RK-ASPEN jednačine stanja i Van der Waals-ovog pravila mešanja. RK-ASPEN jednačina stanja je zatim iskorišćena za izračunavanje fazne ravnoteže za binarni sistem trigliceridi-metanol na povišenim pritiscima i temperaturama, koji su uobičajeni za reakciju sinteze biodizela bez prisustva katalizatora. Dobijeni rezultati su ukazali na značajnu zavisnost kinetike reakcije od fazne ravnoteže posmatranog binarnog sistema.

Thermogravimetry, TG, of lipids is an appropriate analytical method, commonly used to correlate the kinetic parameters of the thermal degradation of lipids and their composition. Thus, samples of total lipids extracted from the raw fatty tissue of fallow deer were subjected to non-oxidative and oxidative TG analysis. The samples were previously stored for nine months at +4 °C and -18°C. The material stability was investigated in order to establish the most favorable conditions for the production and storage of different foods. The total lipids were extracted according to the Folch method. The identification and quantitative analysis of the methyl esters of the fatty acids of the total lipids were performed by capillary gas chromatography. Based on the non-oxidative and oxidative TG results, the activation energies of the thermal degradation and oxidation of the total lipids extracted from different samples of fatty tissue were determined. The Doyle-Gorbachev method was used for the calculations., Termogravimetrijska (TG) analiza lipida je pogodna analitička metoda na osnovu čijih podataka se mogu korelisati kinetički parametri procesa termičke degradacije lipida sa njihovim sastavom. S obzirom na ovu vrstu primene, izvedena je neoksidativna i oksidativna TG analiza na uzorcima ukupnih lipida ekstrahovanim iz svežeg masnog tkiva jelena lopatara. Uzorci ukupnih lipida su prethodno čuvani devet meseci na temperaturi +4°C i -18°C. Ovom metodom se utvrđuje stabilnost različitih materijala, što pomaže da se utvrde najpovoljniji uslovi proizvodnje i skladištenja raznih životnih namirnica. Prethodno određen masno-kiselinski sastav ukupnih lipida jelena lopatara (Cervus Dama dama L.) je doprineo tumačenju efekata uočenih pri TG. Ukupni lipidi su ekstrahovani metodom po Folhu (Folch). Identifikacija i kvantitativna analiza metil-estara masnih kiselina ukupnih lipida izvedena je na kapilarnom gasnom hromatografu. Na osnovu rezultata neoksidativne i oksidativne TG analize, primenom metode Dojl-Gorbačova (Doyle-Gorbachev ) određena je energija aktivacije procesa termičke razgradnje i termičke oksidacije ukupnih lipida ekstrahovanih iz različitih uzoraka masnog tkiva.

Thermogravimetry, TG, of lipids is an appropriate analytical method, commonly used to correlate the kinetic parameters of the thermal degradation of lipids and their composition. Thus, samples of total lipids extracted from the raw fatty tissue of fallow deer were subjected to non-oxidative and oxidative TG analysis. The samples were previously stored for nine months at +4 degrees C and -18 degrees C. The material stability was investigated in order to establish the most favorable conditions for the production and storage of different foods. The total lipids were extracted according to the Folch method. The identification and quantitative analysis of the methyl esters of the fatty acids of the total lipids were performed by capillary gas chromatography. Based on the non-oxidative and oxidative TG results, the activation energies of the thermal degradation and oxidation of the total lipids extracted from different samples of fatty tissue were determined. The Doyle-Gorbachev method was used for the calculations.

Mathematical models of alumina/silica gel supercritical drying with carbon dioxide were studied using supercritical drying experimental data. An alumina/silica gel with zinc chloride was synthesized and dried with superciritical carbon dioxide, and its weight change was monitored as a function of drying time. The pore size distribution of the obtained aerogel was determined using the BET method and nitrogen adsorption/ desorption. The mathematical model of the supercritical drying of the wet gel was represented as unsteady and one-dimensional diffusion of solvent through the aerogel pores filled with supercitical carbon dioxide. Parallel pore model and pores in series model were developed on the basis of the measured porous structure of the aerogel. It was found that these models which use different effective diffusivity value for each pore size were in much better agreement with the experimental data than models which use an overall effective diffusivity. The local effective diffusivity coefficients were calculated using different tortuosity values for each pore size, and they were distributed according to the pore size distribution data. Model simulations of the superciritical drying with carbon dioxide confirmed that the drying temperature and gel particle diameter have a significant influence on the drying time., U ovom radu su ispitani matematički modeli sušenja alumosilikatnog gela sa natkritičnim ugljen-dioksidom na osnovu eksperimentalnih podataka natkritičnog sušenja. Sintetizovani alumosilikatni gel sa cink-hloridom je sušen sa natkritičnim ugljen dioksidom, pri čemu je praćena njegova promena mase sa vremenom. Raspodela veličina pora aerogela je određena BET metodom i adsorpcijom/desorpcijom azota. Matematički model natkritičnog sušenja je prikazan kao nestacionarna jednodimenziona difuzija rastvarača kroz pore aerogela ispunjene natkritičnim ugljen- dioksidom. Model paralelnih pora i model redno vezanih pora su razvijeni na osnovu izmerene porozne strukture dobijenog aerogela. Rezultati ukazuju da je slaganje modela paralelnih pora i modela redno vezanih pora sa različitim vrednostima efektivne difuzivnosti za pore različitih veličina i eksperimentalnih podataka, znatno bolje nego u slučaju modela koji koriste jednu vrednost efektivne difuzivnosti. Koeficiejenti efektivne difuzivnosti su dobijeni korišćenjem različitih vrednosti lokalnih izuvijanosti pora za svaku dimenziju pora, pri čemu su ovi koeficijenti efektivne difuzivnosti distribuirani na osnovu podataka o raspodeli veličina pora. Simulacijom natkritičnog sušenja je potvrđeno da temperatura sušenja i dimenzije gela imaju značajan uticaj na vreme sušenja.

The alumina/silica with zinc chloride aerogel alkylation catalyst was obtained using a one step sol-gel synthesis, and subsequent drying with supercritical carbon dioxide. The aerogel catalyst activity was found to be higher compared to the corresponding xerogel catalyst, as a result of the higher aerogel surface area, total pore volume and favourable pore size distribution. Mixed Al-O-Si bonds were present in both gel catalyst types. Activation by thermal treatment in air was needed prior to catalytic alkylation, due to the presence of residual organic groups on the aerogel surface. The optimal activation temperature was found to be in the range 185-225 ºC, while higher temperatures resulted in the removal of zinc chloride from the surface of the aerogel catalyst with a consequential decrease in the catalytic activity. On varying the zinc chloride content, the catalytic activity of the aerogel catalyst exhibited a maximum. High zinc chloride contents decreased the catalytic activity of the aerogel catalyst as the result of the pores of the catalyst being plugged with this compound, and the separation of the alumina/silica support into Al-rich and Si-rich phases. The surface area, total pore volume, pore size distribution and zinc chloride content had a similar influence on the activity of the aerogel catalyst as was the case of xerogel catalyst and supported zinc chloride catalysts., Alumosilikatni aerogel sa cink-hloridomkao katalizator za reakcije alkilovanja, dobijen je jednostepenim sol-gel postupkom i naknadnim sušenjem sa natkritičnim ugljen-dioksidom. Utvrđeno je da je katalitička aktivnost aerogel - katalizatora viša od katalitičke aktivnosti odgovarajućeg kserogel - katalizatora, zbog veće specifične površine i ukupne zapremina pora aerogel - katalizatora, kao i povoljnije raspodele veličina pora. Oba tipa gel - katalizatora poseduju mešovite Al-O-Si veze u strukturi alumosilikatnog nosača. Zbog prisustva zaostalih organskih grupa na površini aerogel katalizatora, pre katalitičkog alkilovanja neophodna je aktivacija katalizatora zagrevanjem na povišenoj temperaturi u atmosferi vazduha. Optimalna temperatura aktivacije je u opsegu 185-225 ºC, dok je viša temperatura aktivacije rezultirala uklanjanjem cink-hlorida sa površine katalizatora i značajnim smanjenjem katalitičke aktivnosti. Zavisnost katalitičke aktivnosti od sadržajacink-hlorida je pokazala maksimum. Visoki sadržaj cink-hlorida je doveo do pada katalitičke aktivnosti usled zapunjavanja pora katalizatora ovim jedinjenjem i separacije alumosilikatnog nosača na faze bogate aluminijumom i silicijumom. Utvrđeno je da specifična površina, ukupna zapremina pora, raspodela veličina pora i sadržaj cink-hlorida, imaju sličan uticaj na aktivnost aerogel-katalizatora kao i na aktivnost kserogel-katalizatora i katalizatora dobijenih nanošenjem cink-hlorida na različite nosače.