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Determination of analytical parameters of a solid state ammonium-selective electrode
No full textU ovom radu primjenom elektroanalitičkih tehnika određene su analitičke značajne čvrstofazne amonij-selektivne elektrode – osjetljivost, granica detekcije, linearno područje, vrijeme odziva, stabilnost i selektivnost. Uz navedene analitičke značajke ispitana je i reverzibilnost u linearnom području. Na poliimidnu podlogu inkjet ispisom naneseni su srebrni elektrodni supstrat i grafenski čvrsti kontakt. Nakon termičkog i fotonskog sinteriranja na pripremljenu elektrodu nakapana je polimerna amonij-selektivna membrana s nonaktinom kao ionoforom. Potenciometrijskim mjerenjima dobivene su baždarne i dinamičke krivulje u standardnim otopinama kloridnih soli primarnog iona (NH4+), iona interferenata (K+, Na+, Ca2+, Mg2+) i primarnog iona s konstantnom koncentracijom interferentnog iona. Osjetljivost, granica detekcije i linearno područje određeni su iz ovisnosti izmjerene elektromotorne sile o logaritmu aktiviteta NH4+ iona, dok je vrijeme odziva izračunato iz istovremeno određene dinamičke krivulje. Stabilnost naponskog odziva elektrode ispitana je testom na vodeni sloj. Potenciometrijski koeficijenti selektivnosti određeni su metodom odvojenih otopina i metodom miješanih otopina.Analytical parameters of an all-solid-state ammonium selective electrode – sensitivity, limit of detection, linear range, response time, stability and selectivity were determined by using electroanalytical methods. Reversibility in the linear range was also tested. Silver electrode substrate and graphene solid contact were inkjet printed on polyimide substrates. After thermal and photonic sintering, polymeric ammonium-selective membrane with nonactin as the ionophore was drop-cast on top of the prepared electrode. Calibration and dynamic potential curves were obtained via potentiometric measurements in the chloride solutions of the primary ion (NH4+), interferent ions (K+, Na+, Ca2+, Mg2+) and the primary ion with a constant background of interferent ion. Sensitivity, limit of detection and linear range were determined from the calibration curve recorded in primary ion solutions of varying activities, while the response time was determined from the dynamic potential response curve obtained simultaneously. Potential stability of the ammonium-selective electrode was explored through water layer test. Potentiometric selectivity coefficients were determined via separate solution method and fixed interference method
A review of the Chernobyl nuclear power plant
No full textTema ovog rada je nesreća koja se dogodila 26. travnja 1986. u nuklearnoj elektrani Černobil, uzrokovana manama u dizajnu reaktora, neupućenosti osoblja u navedene mane i ignoriranjem sigurnosnih mjera prilikom provođenja sigurnosnog testa na reaktoru 4. Objašnjen je proces fisije koji se događa u reaktorima nuklearnih elektrana koje koriste obogaćeni uranij kao gorivo. Prikazani su povijest nuklearnih elektrana i razvoj reaktora, s posebnim naglaskom na RBMK-1000 reaktor koji je korišten u nuklearnim elektranama u bivšem Sovjetskom Savezu, pa tako i u nuklearnoj elektrani Černobil. Opisan je i shematski prikazan princip rada RBMK-1000 reaktora i objašnjene su njegove najbitnije karakteristike – pozitivni koeficijent praznina, koji posebno dolazi do izražaja pri niskim snagama reaktora, i loš dizajn kontrolnih šipki, vrh kojih je načinjen od grafita koji ne usporava lančanu reakciju nego ju, naprotiv, pospješuje. Nesreća u nuklearnoj elektrani Černobil prikazana je u odlomcima kronološki, sa shematskim prikazima tijeka nesreće. Prikazani su ljudski napori i žrtve tijekom sanacija posljedica nesreće, kao i zdravstvene posljedice stanovnika okolnog područja, pogotovo djece kod kojih je stostruko porastao broj raka štitnjače.The topic of this thesis is the accident that occurred on April 26, 1986 at the Chernobyl nuclear power plant, caused by flaws in the design of the reactor, staff’s lack of information about the mentioned flaws and the ignoring of safety measures when conducting the safety test on reactor No. 4. The fission process that occurs in nuclear power plant reactors that use enriched uranium as fuel is explained. The history of nuclear power plants and the development of reactors are presented, with special emphasis on the RBMK-1000 reactor, which was used in nuclear power plants in the former Soviet Union, including in the Chernobyl nuclear power plant. The working principle of the RBMK-1000 reactor is described and shown schematically, and its most important characteristics are explained - the positive void coefficient, which is especially important at low reactor powers, and the poor design of the control rods, the end of which is made of graphite, which does not slow down the chain reaction but, on the contrary, it promotes it. The accident at the Chernobyl nuclear power plant is presented in paragraphs chronologically, with schematic representations of the course of the accident. The human efforts and sacrifices during the remediation of the consequences of the accident and the health consequences of the inhabitants of the surrounding area, especially of children, where the number of thyroid cancers has increased a hundredfold, are shown
Selection of solvents for separation of homogeneous azeotropes
No full textOsnovni cilj ovoga rada je usporediti učinkovitost različitih otapala za separaciju dvokomponentne azeotropne smjese etanola i vode procesom ekstrakcijske destilacije.
Za separaciju dvokomponentne azeotropne smjese kao pomoćna komponenta koristi se glicerol i niskotemperaturno eutektičko otapalo pripravljeno od kolin klorida i glicerola u molnom omjeru 1:2. Eksperimentalno je određena baždarna krivulja ovisnosti indeksa loma o koncentraciji etanola u smjesi s vodom koja se koristila za mjerenje koncentracije dvokomponentnih smjesa. Također se provela vakuum destilacija kako bi se odredio utjecaj tlaka na učinkovitost separacije smjese etanola i vode. Pri tlaku od 0,25 bara dobiven je destilat s najvećim udjelom etanola. Za približno jednaku učinkovitost procesa ekstrakcijske destilacije smjese etanola i vode potrebno je 5 % glicerola ili 15 % odabranog niskotemperaturnog eutektičkog otapala.The aim of this paper is to compare the effectiveness of different solvents for the separation of a binary azeotropic mixture of ethanol and water by extractive distillation. For the separation of the binary azeotropic mixture, glycerol and deep eutectic solvent prepared from choline chloride and glycerol in a molar ratio of 1:2 are used as an auxiliary component.
The calibration curve of the dependence of the refractive index on the concentration of ethanol in a mixture with water was experimentally determined, which was used to measure the concentration of binary mixtures. Vacuum distillation was carried out to determine the effect of pressure on the separation efficiency of the ethanol-water mixture. At a pressure of 0.25 bar, the distillate with the highest ethanol content was obtained. For an approximately equal efficiency of the extractive distillation process for the ethanol-water mixture,
5% glycerol or 15% of the selected deep eutectic solvent is required
Investigating possibilities of applying a luminescent dissolved oxygen sensor
No full textMjerenje otopljenog kisika u vodenim ekosustavima je ključno za ekološku ravnotežu i kvalitetu voda, a njegove karakteristike bit će prikazane kroz pregled iz kemijske, fizikalne i ekološke perspektive. Senzori su uređaji koji mjere fizikalne veličine i pretvaraju ih u električne signale za daljnju obradu, te se sve više koriste u različitim ljudskim aktivnostima te industrijskim sektorima, uključujući obradu vode. U ovome radu analizirani i sažeti principi, primjene, prednosti i nedostaci najčešće korištenih metoda detekcije otopljenog kisika s naglaskom na optičke senzore luminiscentnog tipa čija tehnologija je sve učestalija u različitim aspektima obrade voda. Svrha ovoga rada je objediniti postojeće znanje na sveobuhvatan i sažet način, pritom dajući sve potrebne informacije za razumijevanje luminiscentnog senzora s otopljenim kisikom.Measuring dissolved oxygen in aquatic ecosystems is crucial for ecological balance and water quality, and its characteristics will be presented through an overview from chemical, physical, and ecological perspectives. Sensors are devices that measure physical quantities and convert them into electrical signals for further processing, and they are increasingly being utilized in various human activities and industrial sectors, including water treatment. This paper systematically analyzes and summarizes the principles, applications, advantages, and disadvantages of the most commonly used dissolved oxygen detection methods, with a focus on optical sensors of the luminescent type, whose technology is becoming more prevalent in various aspects of water treatment. The purpose of this paper is to consolidate existing knowledge in a comprehensive and concise manner, providing all the necessary information for understanding luminescent dissolved oxygen sensors
Enzymatic hydrolysis of protein in shrimp waste
No full textEnzimi su biološki katalizatori koji pri definiranim uvjetima ubrzavaju biokemijske reakcije u živim stanicama i izvan njih. Proteaze su enzimi koji kataliziraju hidrolizu peptidne veze u proteinima. U eksperimentalnom dijelu ovog rada korištene su tri komercijalne proteaze: Alkalaza, Novozyme 37071 i Novo-Pro D, s ciljem hidrolize proteina u otpadu ljuski rakova. Navedeni proces je jedan od koraka izolacije hitina iz ove vrste otpada. Ova biološka metoda uklanjanja proteina ima brojne prednosti ispred kemijskih metoda. Rezultati pokazuju da su sve tri proteaze uspješne u reakciji hidrolize proteina iz otpada rakova, dok je najveći učinak pokazao Novo – Pro D.Enzymes are biological catalysts that, under defined conditions, accelerate biochemical reactions inside and outside living cells. Proteases are enzymes that catalyse the cleavage of peptide bonds in proteins. Three commercial proteases were used in this work: Alcalase, Novozyme 37071 and Novo – Pro D, with the aim of hydrolysing proteins in shrimp waste. The mentioned method is one of the steps in the isolation of chitin from this type of waste. This biological method of protein removal has more advantages than chemical methods. The results show that all three proteases are successful in the protein hydrolysis reaction from shrimp waste, while Novo – Pro D showed the greatest effect
Testing of properties od transparent resin based on epoxides used in 3D printing
No full textPolimeri su tvari građene od makromolekula koje nastaju povezivanjem velikog broja ponavljanih jedinica koje se nazivaju monomeri. Aditivna proizvodnja je dio proizvodnoga strojarstva koji se bavi izradbom predmeta nanošenjem materijala u tankim slojevima. U CAD programu se dizajnira željeni model te se ispisuje nekom od tehnologija 3D-ispisa. DLP je jedna od tehnologija aditivne proizvodnje koja se temelji na fotopolimerizaciji, prilikom ispisa se, projektorom valne duljine svijetlosti 405 nm, osvjetljava cijela površina sloja koji se očvršćuje. Ploča za ispis se pomiče vertikalno prema gore nakon svakog stvrdnutog sloj te nastaje model. Cilj ovog završnog rada je ispitati utjecaj kuta ispisa i naknadne obrade u komori za očvršćivanje sa izvorom elektromagnetskog zračenja na primjenska svojstva
3D-ispisanih modela izrađenih od smole Prima™ Creator value STANDARD CLEAR. Ispitat će se utječe li kut ispisa te dodatno očvršćivanje polimernog modela na mehanička, kemijska i toplinska svojstva materijala. Modeli epruveta za ispitivanje svojstava i pločica za bubrenje dizajnirani su korištenjem programa Fusion 360, te su ispisani na uređaju Anycubic Photon M3. Kut ispisa je bio 0°, 45° i 90° u odnosu na ploču za ispis, a vrijeme provedeno u 405 nm komori je bilo 0, 5 i 15 minuta. Mehanička svojstva ispitana su korištenjem mehaničke kidalice vlačnim testom. Kemijska svojstva ispitana su testom bubrenja u vodi, acetonu i metanolu te infracrvenom spektroskopijom. Toplinska svojstva ispitana su diferencijalnom pretražnom kalorimetrijom. Rezultati provedenih eksperimenata pokazali su da kut ispisa i dodatno očvršćivanje utječu na primjenska svojstva materijala. Naknadnim očvršćivanjem uzorci su postali krući, manje žilavi te su pokazivali niže vrijednosti istezanja pri lomu. Uzorci ispisani pod kutom od 0° pokazali su niže istezanje i veću čvrstoću od ostalih. Aceton i metanol su agresivna otapala koja izazivaju bubrenje kojim dolazi do degradacije uzoraka. Naknadnim očvršćivanjem smanjuje se intenzitet bubrenja. Infracrvena spektrometrija je pokazala promjenu strukture molekula očvršćivanjem koja se pratila intenzitetom signala epoksidnih skupina. Pomoću termograma dobivenih diferencijalnom pretražnom kalorimetrijom ne može se zaključiti da kut ispisa utječe na toplinska svojstva, a naknadno umrežavanje blago povisuje temperaturu staklastog prijelaza.Polymers are substances composed of macromolecules that form by linking a large number of repetitive units known as monomers. Additive manufacturing is a part of manufacturing engineering that involves creating objects by depositing materials in thin layers. In a CAD program, the desired model is designed and then printed using one of the 3D printing methods. DLP is one of the additive manufacturing technologies based on photopolymerization. During printing, the entire surface of the intended layer is illuminated by a light projector, causing it to solidify. The printing plate moves after each solidified layer, forming the model. The aim of thesis is to investigate the influence of the printing angle and curing, on the functional properties of 3D printed models made from Prima™ Creator Value STANDARD CLEAR resin. Hypotheses are that the angle of printing and curing of the sample after it has been formed affect the mechanical, chemical, and thermal properties of the material. Models of test specimens and swelling test plates were designed using a program Fusion 360 and printed on an Anycubic Photon M3 device. The printing angle was set at 0°, 45°, and 90° with respect to the printing plate, and the time spent in the 405 nm chamber for curing was 0, 5, and 15 minutes. Mechanical properties were assessed with a tensile strenght test. Chemical properties were examined through tests of swelling in water, acetone, and methanol, as well as with infrared spectroscopy. Thermal properties were investigated using differential scanning calorimetry. The results of the conducted experiments demonstrated that the printing angle and curing time influence the functional properties of the material. Subsequent curing made the samples stiffer, less tough, and exhibited lower values of elongation at break. Samples printed at a 0° angle displayed lower elongation and higher strength compared to others. Acetone and methanol, aggressive solvents, caused swelling leading to the breakdown of samples. Curing reduced the intensity of swelling. Infrared spectroscopy indicated a change in molecular structure due to curing, observed through the change of intensity of epoxy group signals. Thermal analysis by differential scanning calorimetry did not conclusively indicate an effect of the printing angle on thermal properties, while additional crosslinking slightly raised the glass transition temperature
Development and validation of an analytical method for the determination of impurities in the ceritinib active pharmaceutical substance
No full textCeritinib je farmaceutska tvar koja se koristi za liječenje odraslih bolesnika s uznapredovalim rakom pluća nemalih stanica. Ovaj lijek se koristi samo u slučajevima kada stanice raka imaju mutaciju uzrokovanu genom zvanim kinaza anaplastičnog limfoma, i u tom slučaju su osobe pozitivne na taj gen. Kako bismo mogli odvojiti naš farmaceutik od potencijalnih onečišćenja koja se u njemu nalaze potrebno je imati dobru kromatografsku metodu koju je zatim potrebno validirati. Validacija kromatografske metode je nužan korak u osiguravanju kvalitete proizvoda. To je postupak kojim se definiraju potrebni zahtjevi, provodi eksperimentalno ispitivanje izvedbenih karakteristika metode te daje potvrda o zadovoljenosti postavljenih zahtjeva. Cilj ovog rada bio je razviti i validirati metodu za određivanje poznatih onečišćenja u ceritinib aktivnoj farmaceutskoj tvari. Tekućinska kromatografija visoke djelotvornosti (HPLC) je tehnika korištena u ovom radu. Tijekom validacije ispitane su sljedeće izvedbene karakteristike metode: specifičnost/selektivnost, linearnost, radno područje, preciznost (ponovljivost), granica kvantifikacije, granica detekcije, stabilnost otopine te robusnost. Granica detekcije iznosi 105 ppm, dok granica kvantifikacije iznosi 350 ppm.Ceritinib is a pharmaceutical substance used to treat adult patients with advanced non-small cell lung cancer (NSCLC). This medicine is only used in cases where cancer cells have a mutation caused by gene called anaplastic lymphoma kinase (ALK), and in that case person is positive for that gene. In order to be able to separate our pharmaceutical from potential impurities found in it, it is necessary to have a good chromatographic method, which then needs to be validated. Validation of the chromatographic method is a necessary step in ensuring product quality. It is a procedure that defines the necessary requirements, conducts an experimental test of the performance characteristics of the method, and provides confirmation of the satisfaction of the set requirements. The aim of this study is to develop and validate a method for the determination of known impurities in the active pharmaceutical substance ceritinib. High performance liquid chromatography (HPLC) is the technique used in this work. During the validation, the following performance characteristics of the method were examined: specificity/selectivity, linearity, working range, precision (reproducibility), quantification limit, detection limit, solution stability and robustness
Determination of optimal ZnSO4 electrolyte concentration for graphene/zinc hybrid supercapacitor
No full textU ovom radu provedena je sinteza i ispitivanje reduciranog grafenovog oksida (rGO) i rGO modificiranog acetilenskim crnilom (AC) s ciljem izrade superkondenzatora i hibridnog superkondenzatora. Ispitivanje je provedeno u troelektrodnom sustavu korištenjem metode cikličke voltametrije (CV) i elektrokemijske impedancijske spektroskopije (EIS). Modificirane elektrode sadržavale su 10 % i 20 % acetilenskog crnila. Utvrđeno je da sve elektrode pokazuju dobra kapacitivna svojstva u otopini Na2SO4 i ZnSO4 te da je u otopini ZnSO4 moguće istaložiti cink. Korištene su tri različite koncentracije ZnSO4 elektrolita pri čemu je najbolja reverzibilnost postignuta u otopini najveće koncentracije. Površine elektroda su snimljene optičkim mikroskopom čime je utvrđeno da poroznost sloja raste s dodatkom AC. Osim modificiranih elektroda, u ovom radu je uspješno priređen i rGO papir modificiran s 20 % AC (rGO/20 % AC papir). Dobiveni rGO/20 % AC papir korišten je kao aktivni materijal u superkondenzatoru s 0,5 mol dm-3 Na2SO4 kao osnovnim elektrolitom i hibridnom superkondenzatoru s 1 mol dm-3 ZnSO4 kao osnovnim elektrolitom. Sastavljeni superkondenzatori testirani su metodom CV i EIS te su ispitani tijekom 1000 ciklusa punjenja/pražnjenja. Dobivene vrijednosti specifičnih kapaciteta u slučaju superkondenzatora iznose od 20,15 do 21,62 F g^-1, dok hibridni superkondenzator ima nešto veće vrijednosti, od 28,21 do 31,78 F g^-1. Veće vrijednosti specifičnih kapaciteta kod hibridnog superkondenzatora dokaz su da je on uspješno priređen.In this work, the synthesis and testing of reduced graphene oxide (rGO) and rGO modified with acetylene black (AC) was carried out with the aim of making a supercapacitor and a hybrid supercapacitor. The testing was conducted in a three electrode system using the method of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The modified electrodes contained 10 % and 20 % acetylene black. It was determined that all electrodes show good capacitive properties in Na2SO4 and ZnSO4 solutions. Also, it was possible to precipitate zinc in ZnSO4 solution. Three different concentrations of ZnSO4 electrolyte were used, whereby the best reversibility was achieved in the solution with the highest concentration. The surfaces of the electrodes were recorded with an optical microscope, which indicated that the porosity of the layer increases with the addition of AC. Except the modified electrodes, rGO paper modified with 20 % AC (rGO/20% AC paper) was also successfully prepared in this work. The obtained rGO/20 % AC paper was used as an active material in a supercapacitor containing 0.5 mol dm-3 Na2SO4 electrolyte and in a hybrid supercapacitor containing 1 mol dm-3 ZnSO4 as the base electrolyte. The assembled supercapacitors were tested using the CV and EIS methods. Additionally, they were tested during 1000 charge/discharge cycles. For the supercapacitor, the obtained values of specific capacitance range from 20.15 to 21.62 F g^-1, while the hybrid supercapacitor has slightly higher values, from 28.21 to 31.78 F g^-1. The higher values of the specific capacitance of the hybrid supercapacitor are proof that it has been successfully prepared
Advanced synthesis methods of nanocrystalline manganese-doped ceria
No full textU ovom radu pripravljeni su uzorci cerijeva(IV) oksida, CeO2, koristeći tri napredne metode sinteze: hidrotermalnu, sol-gel i mehanokemijsku sintezu. Pripravljeni uzorci karakterizirani su rendgenskom difrakcijskom analizom, termogravimetrijskom analizom, transmisijskom te pretražnom elektronskom mikroskopijom, rendgenskom fotoelektronskom spektroskopijom, adsorpcijsko desorpcijskim izotermama dušika i difuznom refleksijskom spektroskopijom. Pokazano je da se svakom od tri istraživane metode sinteze može pripraviti nanokristalinični cerijev(IV) oksid te da su sve tri metode pogodne za pripravu nanokristaliničnog cerijevog(IV) oksida dopiranog s manganom. Sol-gel metoda omogućuje ugradnju iona mangana u strukturu cerijeva(IV) oksida bez pojave novih faza, dok se u uzorcima pripravljenim hidrotermalnom i mehanokemijskom sintezom uz CeO2 u uzorcima pojavljuje dodatna faza s manganom, birnesit. Produkte sol-gel i mehanokemijske sinteze potrebno je naknadno termički obrađivati kako bi se dobio CeO2. Međutim, ukoliko su takvi produkti potencijalni katalizatori u procesima koji se provode pri povišenim temperaturama, potrebno ih je prethodno termički obraditi. Ulazak mangana u kristalnu strukturu CeO2 dokazan je smanjenjem parametra jedinične ćelije kubične kristalne rešetke cerijeva(IV) oksida za uzorke dobivene primjenom prethodno navedenih metoda. Zapažen je i pozitivan utjecaj mangana na termičku stabilnost CeO2 koji se očituje u manjim veličinama kristalita dopiranih uzoraka u odnosu na nedopirane. Iako su hidrotermalnom sintezom dobiveni kristaliti najmanje veličine, sol-gel sinteza pokazala se kao metoda čiji kristaliti pokazuju najmanji rast. Isto tako, iako uzorci pripravljeni hidrotermalnom sintezom imaju najveće specifične površine, nakon termičke obrade najveće površine pokazali su uzorci pripravljeni sol-gel sintezom. Kao prednost mehanokemijske sinteze može se navesti dobivanje najvećih količina uzoraka jednom sintezom. Katalitička aktivnost pripravljenih uzoraka testirana je u procesu oksidacije toluena ili smjese aromatskih spojeva (benzen, toluen, etilbenzen i ksilen, BTEX). Svi dopirani uzorci pokazali su značajno povećanje aktivnosti u odnosu na nedopirane. Za svaku od sinteza dopirani uzorci postigli su konverzije od 95 % pri nižim temperaturama u odnosu na nedopirane uzorke, međutim, čak i nedopirani uzorak pripravljen sol-gel sintezom pokazuje bolju katalitičku aktivnost od najuspješnijeg katalizatora iz serije dobivene mehanokemijskom sintezom. Povećanje katalitičke aktivnosti svih uzoraka u kojima je dio cerija zamijenjen manganom posljedica je ulaska iona nižeg oksidacijskog stanja (Mn3+) umjesto Ce4+ u kristalnu strukturu CeO2. Zbog toga dolazi do stvaranja vakancija kisika i površinskih aktivnih (nezasićenih) mjesta kojima se kompenzira negativan naboj. Također, dopirani uzorci su toplinski stabilniji te imaju manje čestice i veće specifične površine u odnosu na nedopirane.In this paper, ceria, CeO2, samples were prepared using three advanced synthesis methods: hydrothermal, sol-gel and mechanochemical synthesis. The prepared samples were characterized by X-ray diffraction analysis, thermogravimetric analysis, transmission and scanning electron microscopy, X-ray photoelectron spectroscopy, nitrogen adsorptiondesorption isotherms and diffuse reflection spectroscopy. It is shown that each of the three researched synthesis methods can be used to prepare nanocrystalline cerium (IV) oxide and that all three methods are suitable for the preparation of nanocrystalline cerium (IV) oxide doped with manganese. The sol-gel method enables the incorporation of manganese ions into the cerium (IV) oxide structure without presence of new phases, while in hydrothermally and mechanochemically derived samples, in addition to CeO2, birnessite, a phase with manganese also appears. The products of sol-gel and mechanochemical synthesis need to be subsequently thermally processed to obtain CeO2. However, if the products are intended for use in catalysis processes that occur at elevated temperatures, thermal treatment in necessary. The entry of manganese into the crystal structure of CeO2 was proven by the reduction of the unit cell parameter of the cubic crystal lattice of cerium (IV) oxide for the samples obtained by the three methods mentioned. A positive influence of manganese on the thermal stability of CeO2 was also observed, which is manifested in the smaller crystallite sizes of the doped samples compared to the non-doped ones. Although hydrothermal synthesis produced crystallites of the smallest size, sol-gel synthesis proved to be the method whose crystallites showed the smallest growth. Likewise, although the samples prepared by hydrothermal synthesis have the highest specific surfaces, after thermal treatment the samples prepared by sol-gel synthesis showed the highest surface area. One of the advantages of mechanochemical synthesis is obtaining the largest amount of product. The catalytic activity of the prepared samples was tested in the process of toluene or the aromatic (benzene, toluene, ethylbenzene and xylene, BTEX) gas mixture oxidation. All doped samples showed a significant increase in activity compared to non-doped ones. For each of the syntheses, doped samples achieved conversions of 95 % at a lower temperature compared to undoped samples, however, even the undoped sample prepared by sol-gel synthesis shows better catalytic activity than the most successful catalyst in the series obtained by mechanochemical synthesis. The increase in the catalytic activity of all samples in which part of the cerium is replaced by manganese is a consequence of the entry of ions of a lower oxidation state (Mn3+) instead of Ce4+ into the crystalline structure of CeO2. This results in the creation of oxygen vacancies and surface-active (unsaturated) sites that compensate for the negative charge. Also, doped samples are more thermally stable and have smaller particles and larger specific surfaces compared to non-doped ones
Quantum-chemical calculations of the reaction of ethylene oxide with water
No full textSvrha ovog rada je primijeniti kvantnokemijske izračune međudjelovanja molekula etilen – oksida i vode. U prvom dijelu rada prikazana su svojstva etilen – oksida i vode, kao i teorije poput Hartree – Fock i teorije funkcionala gustoće (DFT) koje ujedno predstavljaju najvažnije metode kvantnokemijskih izračuna. U drugom dijelu proveden je izračun pomoću programskog paketa 'GAUSSIAN 09'. Korištena je metoda funkcionala gustoće (DFT) i model B3LYP. Također, kvantnokemijskim izračunima određene su energije i duljine veza koje su uspoređene s literaturnim podacima.The aim of this paper is to utilize the quantum chemical calculations of molecular interactions between molecules of ethylene oxide and water. In the first part, the properties of ethylene oxide and water are shown as well as theories like Hartree – Fock and Density functional theory which are also the most important methodes of quantum chemical calculations. In the second part, the calculation is made by software package 'GAUSSIAN 09'. Density functional theory is used and B3LYP model. Additionaly the energies and bond lengths are determined by quantum chemical calculations and those are than compared with literture data