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Supercritical fluids(SCFs) offer the possibility for obtaining and designing of new environmentally friendly and sustainable products with special characteristics. Recently, SCFs have been applied for polymer processing,polymer extraction and purification, preparation of optical materials, supercritical blending of additives into polymers,as a foaming agent for microcellular materials, impregnation, fractionation, purification and formation of powdered polymers. This review is focused on some applications of supercritical fluids with special emphasis on their properties of supercritical fluids in water and carbon-dioxide green industrial chemical processes.

Naraščajoče povpraševanje po varnih industrijskih procesih je pripeljalo do razvoja in uporabe okolju prijaznih trdnih katalizatorjev, namenjenih za uporabo pri kislinsko kataliziranih reakcijah z dodano vrednostjo. Kislinska kataliza je eden najpogostejših procesov v kemični industriji. Industrijsko pomembne organske trasformacije vključujejo esterifikacije in transesterifikacije, eterifikacije, dehidracije, oksidacije, acetilacije, sililacije, sintezo biodizla [1,2]. Trdni kislinski katalizatorji, znani kot "zeleni katalizatorji", se uporabljajo kot nadomestek za homogene kislinske katalizatorje. Vsebujejo več okolju prijaznih komponent, hkrati pa zagotavljajo večjo aktivnost in selektivnost v primerjavi z obstoječimi homogenimi katalizatorji [3]. Primer heterogenega katalizatorja je mezoporozna silika - modificiran SBA-15, ki se uporablja za številne organske reakcije. V tej študiji smo se osredotočili na sintezo trdnega kislinskega katalizatorja na osnovi mezoporoznega silike SBA-15 z inkorporiranim kovinskim Al. Z ujetjem kovine v silikatno matrico se katalizatorju izboljšata aktivnost in selektivnost, postane bolj temperaturno obstojen in pridobi večje možnosti za ponovno uporabo. Sintetiziran katalizator smo karakterizirali z adsorpcijo-desorpcijo dušika (BET), živosrebrno porozimetrijo, Fourierjevo transformacijsko infrardečo spektroskopijo (FTIR), vrstično elektronsko mikroskopijo (SEM), dinamičnim svetlobnim sipanjem (DLS), rentgensko difrakcijo (XRD), difuzno refleksno spektroskopijo, termogravimetrično analizo (TGA), temperaturno programirano desorpcijo (TPD) in temperaturno programirano redukcijo (TPR). Nadalje smo z uporabo tega katalizatorja izvedli vrsto reakcij esterifikacij oleinske kisline v metanolu s proizvodnjo metil estra oleinske kisline. Vse eksperimente smo izvedli v laboratorijskem šaržnem reaktorju. Preučevali smo vpliv reakcijske temperature (55, 60, in 64,5) °C in mase katalizatorja m (0,2, 0,4 in 0,6) g na presnovo reakcije. Učinkovitost reakcije smo spremljali z določanjem koncentracije oleinske kisline in metil oleata z uporabo GC-FID. Preverili smo ohranjanje aktivnosti katalizatorja po večkratni zaporedni uporabi. Študijo smo nadgradili z določitvijo kinetičnih parametrov izvedene reakcije.

Starting from the main relation for closed thermodynamic systems for maximum work of reverse processes, a general model for determining the minimum volume of the tank containing compressed ideal gases, nitrogen and oxygen, as the main constituent components of the air has been developed. In addition to thermal and mechanical, in the observed complex system there is a concentration imbalance. In this way, the analyzed isolated system fulfills the conditions for obtaining work. In determining the model, it is assumed that the initial parameters of the gas in the tank, the state of the environment and the necessary energy (maximum work) to be obtained from the given gas are known. Thermal and mechanical imbalance is realized through an isentropic and isothermal state change, while the problem of concentration imbalance, considering the observed gases, is solved on the basis of the relation for the volume fraction of the component in the gas mixture, i.e. the partial pressure of the observed gas in the environment. In addition to the analytical, in order to control the obtained results, a graphical solution of the observed problem was given using the p-v i.e. T-s diagram. At the end of the work, the application of the model is illustrated on a practical example from practice, where the minimum volumes of the tank for nitrogen and oxygen as characteristic gases, were defined. In order to compare the results, the volume of the tank in which the air is located is determined under the same initial conditions, i.e. the same parameters of the environment. The obtained results can be used in practice for dimensioning or estimating the actual volume of the reservoirs for technical gases, since the actual processes are generally irreversible from the thermodynamic aspect. Polazeći od glavne relacije za zatvorene termodinamičke sisteme za maksimalan rad povratnih procesa, u radu je izveden opšti model za određivanje minimalne zapremine rezervoara u kome se nalaze komprimovani idealni gasovi azot i kiseonik koji su glavne sastavne komponente vazduha. Pored termičke i mehaničke neravnoteže, u posmatranom kompleksnom sistemu postoji i koncentraciona neravnoteža. Na taj način u analiziranom izolovanom sistemu su ispunjeni uslovi za dobijanje rada. Pri određivanju modela, pošlo se od pretpostavke da su poznati početni parametri gasa u rezervoaru, stanje okoline kao i neophodna energija (maksimalni rad) koji treba dobiti od datog gasa. Termička i mehanička neravnoteža ostvarena je preko izentropske i izotermske promene stanja dok je problem koncentracione neravnoteže, s obzirom na posmatrane gasove, rešen na bazi relacije za zapreminski udeo komponente u mešavini gasova odnosno parcijalni pritisak posmatranog gasa u okolini. Pored analitičkog rešenja, radi kontrole dobijenih rezultata dato je i grafičko rešenje posmatranog problema korišćenjem p-v odnosno T-s dijagrama. Na kraju rada primena modela ilustrovana je na jednom primeru iz prakse gde su određene minimalne zapremine rezervoara za azot i kiseonik, kao posmatrane karakteristične gasove. Radi poređenja rezultata određena je i zapremina rezervoara u kome se nalazi vazduh pod istim početnim uslovima odnosno istim parametrima okoline. Dobijeni rezultati u praksi mogu poslužiti za dimenzionisanje odnosno procenu stvarne zapremine rezervoara za tehničke gasove s obzirom da su stvarni procesi sa termodinamičkog aspekta uglavnom nepovratni.

Hydrogen could be the important energy sources of the next period provided that its production, transportation, and storage are solved. In this paper review of the production of hydrogen from lignocellulosic feedstock is given. The process is analyzed in all its phases and alternative solutions. Two different, alternative biomass gasification process - direct and indirect, and two different, alternative reforming model - partial oxidation and steam reforming are described. Gas cleaning is also provided with two different, alternative concepts - cold and hot cleaning. Conversion of the working gas and the separation of hydrogen from CO2 and other impurities are still used as a method in the tubular membrane reactor - all in one place which significantly reduced the cost of 1 kg of hydrogen. In all these processes is especially taken into consideration on the integration of energy in the process, which is also significantly contributed to the better price of hydrogen. Vodonik bi u narednom periodu mogao postati značajan izvor energije jer su njegova proizvodnja, transport i skladištenje uglavnom riješeni. U ovom radu se daje pregled proizvodnje vodonika iz lignoceluloznih obnovljivih izvora. Proces je obrađen u svim njegovim fazama i alternativnim rješenjima. Tako su obrađene dva različita, alternativna, procesa gasifikacije biomase - direktna i indirektna i dva različita, alternativna, reforming modela - parcijalna oksidacija i reformiranje vodenom parom. Prečišćavanje gasa je, takođe, dato sa dvije različite, alternativne, koncepcije - hladno i toplo prečišćavanje gasa. Konverzija radnog gasa i razdvajanje vodonika od CO2 i drugih primjesa se danas radi u membranskom cijevnom reaktoru - sve na jednom mjestu što je znatno smanjilo cijenu koštanja 1 kg vodonika. U svim ovim procesima je posebno vođeno računa o integraciji energije u procesu što je takođe znatno doprinijelo ekonomski povoljnijoj cijeni vodonika.

Phenol is a major pollutant in the wastewater because of its presence in the effluent of major processing and refining plants. It has severe effect on human being, both short term and long term. Various methods are used for removal of the phenol from wastewater such as adsorption, photodecomposition, volatilization and other various biological and non-biological methods. In the present study attempt is done to present the survey of the research on the phenol removal by various methods. The methods such as polymerization, electrocoagulation, extraction, photodecomposition, advanced oxidation and ion exchange were used effectively by various investigators. These methods are reported to be efficient for the phenol removal. Suitable method for phenol removal can be selected based on availability of the material, extent of separation required and properties of phenolic effluent. Fenol je jedan od glavnih polutanata u otpadnoj industrijskoj vodi. Utiče na zdravlje ljidi i taj uticaj se ispoljava kako posle kraćeg tako i posle dužeg prisustva. Za uklanjanje fenola iz otpadne vode koriste se metode kao što su adsorpcija, fotorazgradnja, isparavanje (volatilizacija) kao i biološke i nebiološke metode. U ovom radu daje se prikaz istraživanja o uklanjanju fenola različitim metodama kao što su polimerizacija, elektrokoagulacija, fotorazgradnja, unapređena oksidacija i jonska izmena. Izbor metode za uklanjanje fenola može biti učinjen na osnovu raspoloživog materijala, zahtevanog intenziteta prečišćavanja i osobina fenolnog efluenta.

The analysis and sizing of the distillation column for the separation of n-heptane-n-octane mixture were conducted using a traditional method for modeling and describing distillation systems, combined with modern software systems. Basic parameters were obtained by using rigorous separation and calculation procedures for the separation of the mixture used. These parameters describe distillation process, as well as basic dimensions and physical and hydro-dynamic parameters of the distillation column. Analytical and numerical methods were used for the analysis, modeling, sizing and operation control of the system. The previously used calculation methods were verified by developing the program for the case of the binary mixture. The values, obtained in this program were used for further description of the system, as well as sizing and determining basic physical and hydro-dynamic properties such as column diameter, and pressure drop. The key parameters describing this system are optimal reflux, minimum reflux, number of theoretical stages and minimum number of theoretical stages. Changes of the number of stages, reflux and column diameter were monitored as a function of mixture composition, as well as flow of the mixture at entrance of the column. Key words: distillation of binary mixture, rigorous calculation procedures, design methods, distillation columns Tradicionalne metode modelovanja i opisivanja destilacionih sistema, u kombinovanju sa savremenim softverskim paketima, poslužile su za analizu rada i dimenzionisanje destilacione kolone za razdvajanje binarne smješe nheptan-n-oktan. Primjenom rigoroznih postupaka razdvajanja i proračuna za razdvajanje smješe, praćeni su osnovni parametri, koji opisuju tok destilacije, kao i osnovne dimenzije destilacione kolone sa ventilskim podovima i osnovne fizičke i hidro-dinamičke parametre (dijametar kolone i pad pritiska). Za analizu, modelovanje, dimenzionisanje i kontrolu rada ovog sistema korišćene su grafičke, analitičke i numeričke metode. Razvijanjem programa verifikovane su ranije korišćene metode proračuna, a vrijednosti dobijene proračunom su poslužile za dimenzionisanje kolone. Ključni parametri koji opisuju ovaj destilacioni sistem su radni refluksni odnos i minimalni refluksni odnos, broj teorijskih podova i minimalni broj teorijskih podova. Promjene navedenih veličina praćene su u funkciji sastava smješe, kao i protoka smješe na ulazu u destilacionu kolonu.

Tehnološki postupak u kome se dobija energija obuhvata osnovne procese i operacije, kao na primer faznu ravnotežu, kinetiku reakcije, sintezu tehnološke šeme, projektovanje postrojenja i ostale faze sve do dobijanja energije iz sirovina. Povezanost superkritičnih fluida sa energijom je ostvarena nekada samo u jednom koraku procesa a nekada u cijelom procesu. Ovi procesi uključuju procesuiranje obnovljivih materijala, fosilnih goriva i drugih. Povezanost procesa sa primjenom superkritičnih fluida zasniva se na korišćenju specifičnih osobina superkritičnih fluida. Ovo znači i promjenljivost osobina superkritičnih fluida i njihovu interakciju sa procesnim materijalima. I do sada su superkritični fluidi korišćeni u raznim procesima koji se odnose na proizvodnju energije većinom u laboratoriji. Korišćenje superkritičnih fluida u tehnološkim procesima zahtijeva odgovaraju u opremu. Ključno za budući uspjeh je jednostavnost projektovanja, jednostavnost rada, visoka efikasnost i temeljna spoznaja o specifičnim sposobnostima superkritičnih fluida. Process technology comprises the application of fundamentals to processes and operations, as for example phase equilibria, reaction kinetics, synthesis flow diagram, design of process plant to produce energy from raw materials. Sometimes related of supercritical fluids to energy is single process steps although it is sometimes whole processes. These processes include processing of renewable materials, fossil materials and other materials. In general, process related to the application of supercritical fluids is based on the exploitation of the speciifc properties of supercritical fluids. This includes the varying properties of supercritical fluids and the interactions of supercritical fluids with the processes materials. Earlier the supercritical fluids have been used in number of processes related to production of energy, mostly in laboratory. Using supercritical fluids in process technology requires adequate equipment. Keys to future success will be: simple design, simple operation, high efficiency and fundamental knowledge of the specific abilities of supercritical fluids.

U ovom radu prikazani su suštinski aspekti metodologije projektovanja hemijsko-tehnološkog procesa proizvodnje polietera kao jedne od osnovnih komponenata u proizvodnji poliuretana. Osnovni koncept procesa, u kojima se polieteri dobijaju od petrohemijskih sirovina ili od obnovljivih sirovina, zbog svoje kompleksnosti, zasniva se na razmatranju procesa preko četiri nivoa. Svaki nivo procesa objedinjavanja podvrgnut je definisanju odgovarajućih matematičkih modela koji ga opisuju na odogovarajući način. Takođe, predložena je tehnološka šema fleksibilnog polušaržnog procesa za proizvodnju polietera. In this study, the essential aspects of technological processes design for polyether production are presented. The basic concept of the process, in which the polyethers obtained by synthesis from petrochemical raw materials or from renewable resorces, was integrated from four basic levels. Each level of reactive process was defined and the appropriate mathematical models were developed. Also, technological scheme of semibatch flexible process for the production of polyether is given.

Using cheap renewable raw materials such as lignocellulosic feedstock for hydrogen production by fermentation has great significance and potential to give a major contribution to future clean energy. Using hydrogen as a promising alternative energy source for fossil fuels is increasing. Hydrogen is clean, renewable high energy fuel that does not contribute the greenhouse gas effect. The main challenges in developing hydrogen production are the low hydrogen yields due to poor efficiency on a direct microbial assimilation of cellulosic materials. From this reason, in the world today occurs considerable research efforts to improve the pretreatment and hydrolysis of lignocellulosic materials. The development of effective cellulase enzymes, optimization and improvement of the fermentation process as well as engineering approaches to application processes are the basis of the increased popularity of the lignocellulosic feedstock. Research on the genomic combined with genetic engineering offers a wide range of opportunities to improve the performance of using cellulosic raw materials in the production of hydrogen. This paper provides an overview of key technologies in the world today that research and development biohydrogen from lignocellulosic feedstocks.

The parameters of foam preparation, such as addition of fillers, have a significant effect on the properties of polyurethane foams. The goal of this work was to study the effect of the cement addition on the thermo-mechanical properties of rigid polyurethane foams. Isocyanate component was based on polymeric diphenylmethane diisocyanate, and polyol component was polyether type, with addition of castor oil as polyol. It was estimated that the addition of cement increased the values of foam compressive strength and permanent deformation. Compressive strength increased even more than 90% with 20 wt% of cement. Further increase of the cement loading deteriorates the mechanical properties of foamed material because it distorts cellular structures of obtained materials. Addition of cement increased the value of the glass transition temperature of polyurethane foam. The highest increase in the value of glass transition temperature, for 7.5ºC, was achieved by the addition of 20 wt% of cement.

The paper shows an example of performed optimization of sizes in terms of welding costs in a characteristic loaded welded joint. Hence, in the first stage, the variables and constant parameters are defined, and mathematical shape of the optimization function is determined. The following stage of the procedure defines and places the most important constraint functions that limit the design of structures, that the technologist and the designer should take into account. Subsequently, a mathematical optimization model of the problem is derived, that is efficiently solved by a proposed method of geometric programming. Further, a mathematically based thorough optimization algorithm is developed of the proposed method, with a main set of equations defining the problem that are valid under certain conditions. Thus, the primary task of optimization is reduced to the dual task through a corresponding function, which is easier to solve than the primary task of the optimized objective function. The main reason for this is a derived set of linear equations. Apparently, a correlation is used between the optimal primary vector that minimizes the objective function and the dual vector that maximizes the dual function. The method is illustrated on a computational practical example with a different number of constraint functions. It is shown that for the case of a lower level of complexity, a solution is reached through an appropriate maximization of the dual function by mathematical analysis and differential calculus. U radu je, na primeru jednog karakterističnog opterećenog zavarenog sklopa, izvršena optimizacije njegovih dimenzija sa aspekta troškova zavarivanja. Pri ovome, u prvoj fazi definisane su promenljive i nepromenljive veličine i postavljen matematički oblik funkcije optimizacije. U sledećoj etapi procedure, definisan je i postavljen sistem najvažnijih funkcija ograničenja koji se pri projektovanju konstrukcije moraju uzeti u obzir i tehnolog i konstruktor. Na taj način, dobijen je matematički model optimizacije posmatranog problema za čije je efikasno rešavanje predložen metod geometrijskog programiranja. U nastavku, polazeći od matematičke osnove, detaljno je razrađen algoritam optimizacije predložene metode pri čemu su postavljene glavne jednačine problema, a koje važe uz određene uslove. Na taj način, optimizacioni ili primarni zadatak sveo se na dualni zadatak preko odgovarajuće funkcije, koji se znatno lakše rešava u odnosu na primarni zadatak optimizacije funkcije cilja. Glavni razlog za ovo je dobijeni sistem linearnih jednačina. Pri ovome iskorištena je korelacija između optimalnog primarnog vektora koji minimizira funkciju cilja i dualnog vektora koji maksimizira dualnu funkciju. Metoda je ilustrovana na jednom računskom praktičnom primeru sa različitim brojem funkcija ograničenja. Pokazano je da se za slučaj manjeg stepena složenosti, do rešenja može doći maksimizacijom odgovarajuće dualne funkcije, primenom matematičke analize odnosno diferencijalnog računa.

Cilj ovog rada je ukazivanje na mogućnost primene superkritične ekstrakcije sa ugljendioksidom na dekontaminaciju zemljišta zagađenih pesticidima (u ovom slučaju atrazinom). Analizirani rezultati ukazuju da se ova metoda veoma uspešno može koristiti za ostvarivanje istaknutog cilja. The aim of this paper is to study the applicability of supercritical extraction with carbon dioxide to the decontamination of soils containing pesticides (in this case with atrazine). The analyzed results indicate that this method can be successfully used for the realization of prominent purpose.