The importance of pre-treatment of spent hydrotreating catalysts on metals recovery

This work describes a three-step pre-treatment route for processing spent commercial NiMo/Al2O3 catalysts. Extraction of soluble coke with n-hexane and/or leaching of foulant elements with oxalic acid were performed before burning insoluble coke under air. Oxidized catalysts were leached with 9 mol L-1 sulfuric acid. Iron was the only foulant element partially leached by oxalic acid. The amount of insoluble matter in sulfuric acid was drastically reduced when iron and/or soluble coke were previously removed. Losses of active phase metals (Ni, Mo) during leaching with oxalic acid were compensated by the increase of their recovery in the sulfuric acid leachate.

Preparation and thermal decomposition of solid state cinnamates of alkali earth metals, except beryllium and radium

Solid state compounds of general formula ML2.nH2O [where M is Mg, Ca, Sr or Ba; L is cinnamate (C6H5 -CH=CH-COO-) and n = 2, 4, 0.8, 3 respectively], have been synthetized. Thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC) and X-ray diffraction powder patterns have been used to characterize and to study the thermal stability and thermal decomposition of these compounds.

Thermal behavior studies of solid state compounds of 4-dimethylaminocinnamylidenepyruvate with alkali earth metals, except beryllium and radium

Solid state compounds of general formula M(DMCP)2.nH2O, where M represents Mg, Ca, Sr, Ba, and DMCP is 4-dimethylaminocinnamylidenepyruvate, and n = 1, except for Ca, where n = 2.5, have been prepared. Thermogravimetry, derivative thermogravimetry (TG, DTG), differential scanning calorimetry (DSC), X-ray diffraction powder patterns and complexometry were used to characterize and to study the thermal decomposition of these compounds.

Synthesis, characterization and thermal behaviour of solid state compounds of 2-chlorobenzylidenepyruvate with trivalent aluminium, gallium, indium and scandium metals

Solid state compounds M-2-Cl-BP, where 2-Cl-BP is 2-chlorobenzylidenepyruvate and M represents Al, Ga, In, and Sc were prepared. X-ray powder diffractometry, infrared spectroscopy and simultaneous thermogravimetry-differential thermal analysis (TG-DTA), have been used to characterize and to study the thermal behavior of these compounds. The results provided information concerning the stoichiometry, crystallinity, thermal stability and thermal decomposition of the compounds.

Study of mesoscopic tunnel junctions between two normal metals

The main purpose of this work was to study different kinds of metal-based tunnel junctions at low temperatures. The problem which had to be solved was creating a junction with appropriate properties at these temperatures. The materials for junctions were found experimentally. The goal was to find an alloy material that can provide a high quality tunnel junction, which remains in the normal conductive state at low temperatures without applying magnetic field. The fabrication technology of such a device, based on an alloy of aluminium and manganese, is described in detail. In this thesis theoretical properties of tunnel junctions are considered and results of experiments with tunnel junctions are described and quantitative properties of the junctions are analyzed based on the experimental data.

Catalytic transformations of fatty acid derivatives for food, oleochemicals and fuels over carbon supported platinum group metals

Växtoljor som utgör en förnybar naturresurs används som sådana eller i modifierade former i många industriella processer, som är av stor betydelse för vårt vardagliga liv. Växtoljor används i livsmedel, i kemiska och farmaceutiska produkter, i textilindustrin, för framställning av färgämnen och beläggningsmaterial samt som miljövänliga bränslekomponenter. Fetter och oljor hör till de äldsta kemiska komponenterna som utnyttjas av människan. De består huvudsakligen av glycerolestrar och fettsyror. Fetter och oljor har typiskt en kolkedja med kol-koldubbelbindningar samt karboxyl- och estergrupper, som kan genom hydrering eller dekarboxylering konverteras till nyttiga och miljövänliga produkter med hjälp av ädelmetallkatalysatorer. Aktivt kol (C) används som bärare på katalysatorerna. Väteaddition, d.v.s. hydrering av växtoljor har varit föremål för omfattande forskning i över hundra års tid. Hydreringen är en viktig process, för den tillämpas på produktion av fetter och margarin. Omättade fettsyror hydreras traditionellt på nickelbaserade heterogena katalysatorer. Samtidigt med en partiell hydrering av fettsyrorna och fettsyraestrarna som har två dubbelbindningar pågår också isomeringsreaktioner, vilka ger cis- och transisomerer av reaktantmolekylerna. Den största nackdelen med nickelkatalysatorerna är deras giftighet samt bildning av ohälsosamma transisomerer i reaktionsprodukterna. Dessutom deaktiveras nickelkatalysatorn snabbt p.g.a. att nickeltvålar bildas i reaktionsblandningen. Platinabaserade katalysatorer lider däremot inte av dessa begränsningar. Metaller i platinagruppen i det periodiska systemet studerades i detalj för att avslöja kinetiska effekter i hydreringen av cis-metyloleat. Palladium, rutenium, rhodium, platina och iridium användes som katalytiska metaller. Metallhalten på aktivkolbärare var 1 vikt-%. De olika platinametallerna undersöktes för att kartlägga konkurrerande hydrerings- och isomeringsrutter på metallerna. Det visade sig att metallerna i andra raden av det periodiska systemet (Ru, Rh, Pd) är aktivare i isomeringsprocesserna, medan metallerna i tredje raden (Ir, Pt) har en lägre aktivitet. Pd/C valdes bland platinametallerna, för att den är attraktiv ur ekonomisk synvinkel och den är mycket aktiv och selektiv, speciellt jämfört med nickel. Tyngdpunkten i arbetet var utvecklingen av en alternativ, palladiumbaserad hydreringsteknologi som skulle ersätta den traditionella teknologin som är baserad på användningen av nickelkatalysatorer. Palladiumbaserade katalysatorer kan återcirkuleras, de är aktivare och mera resistenta mot syror och de bildar mindre mängder av skadliga transisomerer. För att denna teknologi skall bli ekonomiskt hållbar och konkurrenskraftig, måste den basera sig på de bästa möjliga katalysatorerna, vilket innebär att en optimal kombination av hög aktivitet och selektivitet samt en lång livstid för katalysatorn krävs. Därför inkluderades teknologiska aspekter kraftigt i forskningen. Mycket arbete satsades på design av palladium på en mesoporös kolbärare och undersökning av korrelationerna mellan katalysatorns egenskaper och dess aktivitet i isomeriseringsreaktionerna och i hydreringen av kol-koldubbelbindningarna i reaktantmolekylen. Katalysatorerna karakteriserades med många fysikaliska och kemiska metoder (transmissionselektronmikroskopi (TEM), röntgendiffraktion (XRD), röntgenfotoelektronspektroskopi (XPS), temperaturprogrammerad reduktion (TPR), temperaturprogrammerad desorption (TPD) av kolmonoxid, kemisorption av kolmonoxid, fysisorption av kväve). Temperaturens, vätetryckets och katalysatorkoncentrationens inverkan på fettsyra- och isomersammansättningen hos de hydrerade oljorna bestämdes under kinetiska betingelser, i frånvaro av massöverföringseffekter. Syreavspjälkning genom fullständig dekarboxylering av karboxylgruppen i fettsyramolekylen är det hittills bästa sättet att framställa miljövänlig dieselolja, eftersom linjära paraffiner fås som reaktionsprodukter och en tillsats av dyr vätgas undviks. Deoxygeneringen undersöktes systematiskt på en Pd/C-katalysator (Sibunit) genom att använda mättade fettsyror C16-C20 och C22 som råvara. Produktmolekylen blev en dieselliknande kolvätemolekyl, med en kolatom färre än i utgångsmolekylen. Lika stora dekarboxyleringshastigheter observerades för rena, mättade fettsyror. En jämförelse av deoxygenereringshastigheterna för stearin-, olein- och linolsyra som råvara vid 300oC i närvaro av 1-volymprocent väte på mesoporös Pd/C (Sibunit) avslöjade att katalysatorns aktivitet och selektivitet ökade med en ökande mättningsgrad av reaktantmolekylen. Då stearinsyra användes som utgångsmolekyl, bestod huvudprodukterna av önskade C17-kolväten, medan mängden av aromatiska C17-komponenter ökade, då olein- och linolsyra användes som utgångsmolekyler. Katalysatordeaktiveringen var relativt påfallande vid deoxygeneringen av linolsyra så att endast 3% av fettsyrorna omsattes till produkter i 330 min. Deaktiveringen orsakades av aromatiska C17-komponenter samt av fettsyradimerer, som bildades via en Diels-Alderreaktion. Hydreringen av omättade fettsyror kan därför rekommenderas som ett primärt kemiskt steg i framställningen av miljövänliga dieselprodukter. Målet var också att öka förståelsen av palladiummetallernas roll i nanoskala, speciellt effekten av metallpartiklarna i katalytisk hydrering och deoxygenering. Pd/C-katalysatorer med lika stora halter av Pd syntetiserades och metallens dispersion på bärarmaterialet varierades systematiskt genom en kontrollerad uppväxt av palladiumnanopartiklar på aktiv kolbärare. Metalldispersionens effekt på hydrerings-hastigheten och cis-transförhållandet undersöktes i detalj. En optimal metalldispersion som gav den högsta dekarboxyleringshastigheten hittades. Massöverföringens inverkan på reaktionens hastighet studerades experimentellt och temperaturprogrammerad desorption av kolmonoxid från katalysatorytan undersöktes ingående. Hydrering av växtoljor genomfördes under satsvisa och kontinuerliga betingelser. Både finfördelat Pd/C och katalysatorgranulat användes i experimenten. Ett av målen med arbetet var uppskalningen av hydreringsprocesserna. Med tanke på stora produktionsvolymer var det logiskt att undersöka kontinuerliga hydrerings- och dekarboxyleringsteknologier. En kontinuerlig packad bäddreaktor studerades i laboratorieskala, vilket gav viktig information om katalysatorns långtidsstabilitet och deaktivering. Effekten av rena fettsyror och triglycerider som råvara samt metallpartikelstorleken och palladiumhalten studerades med hjälp av den kontinuerliga reaktorn. Produktionskapaciteten som erhölls med satsvis och kontinuerlig drift jämfördes. Dekarboxyleringen av stearinsyra undersöktes också i en kontinuerlig packad bädd. Omsättningsgraden blev 15% för en stabil katalysator.

EDTA- and DTPA-functionalized silica gel and chitosan adsorbents for the removal of heavy metals from aqueous solutions

Adsorbents functionalized with chelating agents are effective in removal of heavy metals from aqueous solutions. Important properties of such adsorbents are high binding affinity as well as regenerability. In this study, aminopolycarboxylic acid, EDTA and DTPA, were immobilized on the surface of silica gel, chitosan, and their hybrid materials to achieve chelating adsorbents for heavy metals such as Co(II), Ni(II), Cd(II), and Pb(II). New knowledge about the adsorption properties of EDTA- and DTPA-functionalizedadsorbents was obtained. Experimental work showed the effectiveness, regenerability, and stability of the studied adsorbents. Both advantages and disadvantages of the adsorbents were evaluated. For example, the EDTA-functionalized chitosan-silica hybrid materials combined the benefits of the silica gel and chitosan while at the same time diminishing their observed drawbacks. Modeling of adsorption kinetics and isotherms is an important step in design process. Therefore, several kinetic and isotherm models were introduced and applied in this work. Important aspects such as effect of error function, data range, initial guess values, and linearization were discussed and investigated. The selection of the most suitable model was conducted by comparing the experimental and simulated data as well as evaluating the correspondence between the theory behind the model and properties of the adsorbent. In addition, modeling of two-component data was conducted using various extended isotherms. Modeling results for both one- and twocomponent systems supported each other. Finally, application testing of EDTA- and DTPA-functionalized adsorbents was conducted. The most important result was the applicability of DTPA-functionalized silica gel and chitosan in the capturing of Co(II) from its aqueous EDTA-chelate. Moreover, these adsorbents were efficient in various solution matrices. In addition, separation of Ni(II) from Co(II) and Ni(II) and Pb(II) from Co(II) and Cd(II) was observed in two- and multimetal systems. Lastly, prior to their analysis, EDTA- and DTPA-functionalized silica gels were successfully used to preconcentrate metal ions from both pure and salty waters

Application of simulated annealing in simulation and optimization of drying process of Zea mays malt

Kinetic simulation and drying process optimization of corn malt by Simulated Annealing (SA) for estimation of temperature and time parameters in order to preserve maximum amylase activity in the obtained product are presented here. Germinated corn seeds were dried at 54-76 °C in a convective dryer, with occasional measurement of moisture content and enzymatic activity. The experimental data obtained were submitted to modeling. Simulation and optimization of the drying process were made by using the SA method, a randomized improvement algorithm, analogous to the simulated annealing process. Results showed that seeds were best dried between 3h and 5h. Among the models used in this work, the kinetic model of water diffusion into corn seeds showed the best fitting. Drying temperature and time showed a square influence on the enzymatic activity. Optimization through SA showed the best condition at 54 ºC and between 5.6h and 6.4h of drying. Values of specific activity in the corn malt were found between 5.26±0.06 SKB/mg and 15.69±0,10% of remaining moisture.

Utilization of non ferrous metals in boiler combustion environment

The made research is focused on possibility of application of non ferrous metals in boiler pressure parts as a substitute of currently used ferrous-base alloys. The main issue was to define resistive ability of some perspective non ferrous metals to chlorine induced corrosion. Experimental study was performed using simultaneous thermal analysis (STA) in the temperature range of 400-700 °C. The chloride induced corrosion was simulated by mixtures of metal samples with potassium chloride treated by synthetic air. The advantage of synergetic effect of non ferrous alloys compare to single metals is shown due to the obtained data from conducted thermal balance tests.

Use of simulated annealing in standardization and optimization of the acerola wine production

In this study, seven wine samples were prepared varying the amount of pulp of acerola fruits and the sugar content using the simulated annealing technique to obtain the optimal sensory qualities and cost for the wine produced. S. cerevisiae yeast was used in the fermentation process and the sensory attributes were evaluated using a hedonic scale. Acerola wines were classified as sweet, with 11°GL of alcohol concentration and with aroma, taste, and color characteristics of the acerola fruit. The simulated annealing experiments showed that the best conditions were found at mass ratio between 1/7.5-1/6 and total soluble solids between 28.6-29.0 °Brix, from which the sensory acceptance scores of 6.9, 6.8, and 8.8 were obtained for color, aroma, and flavor, respectively, with a production cost 43-45% lower than the cost of traditional wines commercialized in Brazil.

Phonon spectra and thermal properties of some fcc metals using embedded-atom potentials /

By employing the embedded-atom potentials of Mei et ai.[l], we have calculated the dynamical matrices and phonon dispersion curves for six fee metals (Cu,Ag,Au,Ni,Pd and Pt). We have also investigated, within the quasiharmonic approximation, some other thermal properties of these metals which depend on the phonon density of states, such as the temperature dependence of lattice constant, coefficient of linear thermal expansion, isothermal and adiabatic bulk moduli, heat capacities at constant volume and constant pressure, Griineisen parameter and Debye temperature. The computed results are compared with the experimental findings wherever possible. The comparison shows a generally good agreement between the theoretical values and experimental data for all properties except the discrepancies of phonon frequencies and Debye temperature for Pd, Pt and Au. Further, we modify the parameters of this model for Pd and Pt and obtain the phonon dispersion curves which is in good agreement with experimental data.

Application of [Lambda] to the fourth perturbation theory in calculating the equation of state of rare gas solids and fcc metals

We have calculated the thermodynamic properties of monatomic fcc crystals from the high temperature limit of the Helmholtz free energy. This equation of state included the static and vibrational energy components. The latter contribution was calculated to order A4 of perturbation theory, for a range of crystal volumes, in which a nearest neighbour central force model was used. We have calculated the lattice constant, the coefficient of volume expansion, the specific heat at constant volume and at constant pressure, the adiabatic and the isothermal bulk modulus, and the Gruneisen parameter, for two of the rare gas solids, Xe and Kr, and for the fcc metals Cu, Ag, Au, Al, and Pb. The LennardJones and the Morse potential were each used to represent the atomic interactions for the rare gas solids, and only the Morse potential was used for the fcc metals. The thermodynamic properties obtained from the A4 equation of state with the Lennard-Jones potential, seem to be in reasonable agreement with experiment for temperatures up to about threequarters of the melting temperature. However, for the higher temperatures, the results are less than satisfactory. For Xe and Kr, the thermodynamic properties calculated from the A2 equation of state with the Morse potential, are qualitatively similar to the A 2 results obtained with the Lennard-Jones potential, however, the properties obtained from the A4 equation of state are in good agreement with experiment, since the contribution from the A4 terms seem to be small. The lattice contribution to the thermal properties of the fcc metals was calculated from the A4 equation of state, and these results produced a slight improvement over the properties calculated from the A2 equation of state. In order to compare the calculated specific heats and bulk moduli results with experiment~ the electronic contribution to thermal properties was taken into account~ by using the free electron model. We found that the results varied significantly with the value chosen for the number of free electrons per atom.