Nickel Catalysts on Porous Ceramic Supports for the Reaction of Partial Oxidation of Propane to CO and H2

In this paper synthesis, textural and structural properties as well as selectivity of Ni based catalysts for partial oxidation of propane to CO and H2 are given. The influence of aluminosilicate and magnesia based porous ceramic supports on catalyst performance is emphasized. The influence of concentration of impregnation solution, number of successive impregnations and nature of modifier was investigated. The catalytic test was performed in order to define the catalyst with the highest selectivity toward CO and H2 while the presence of side-products like CO2, CH4, and coke as well as unreacted C3H8 are reduced to minimum. All synthesized catalysts samples were dominantly macroporous. The selectivity of catalysts increased with presence of modifiers in the following order: CaO < MgO < Al2O3. The selectivity of studied catalysts is governed mainly by two structural parameters: nickel loading and nickel crystallite size. The comparison of the best performing aluminosilicate and magnesia supported catalysts with Al as modifier revealed that the latter express somewhat lower selectivity particularly toward CO

SOME NEW IDENTITIES FOR THE SECOND COVARIANT DERIVATIVE OF THE CURVATURE TENSOR

In this paper we study the second covariant derivative of Riemannian curvature tensor. Some new identities for the second covariant derivative are given. Namely, identities obtained by cyclic sum with respect to three indices are given. In the first case, two curvature tensor indices and one covariant derivative index participate in the cyclic sum, while in the second case one curvature tensor index and two covariant derivative indices participate in the cyclic sum

Synthesis, characterization and selectivity of catalysts for hydrogenation of vegetable oils

U ovom radu proučavani su višekomponentni katalitički sistemi u kojima su aktivna komponenta (metalni Ni) i pogodni metali (Mg, Ag i Cu) naneseni na pripremljeni nosač (aktivirani dijatomit), kao i njihova primena u svojstvu katalizatora u procesu parcijalne hidrogenizacije jestivih biljnih ulja. Polazni materijal korišćen za sintezu nosača katalizatora predstavljao je sirovi dijatomit domaćeg porekla (ležište dijatomita Baroševac, istočni deo Kolubarskog ugljenog basena). Modifikacijom svojstava sirovog dijatomita hemijskom i termičkom obradom dobijen je nosač katalizatora sa visokim sadržajem silicijum dioksida. Ispitivanja teksturalnih svojstava i granulometrijskog sastava su pokazala da dijatomitni nosač ima makroporoznu strukturu i povoljan granulometrijski sastav, odgovarajući za dobijanje nikl katalizatora koji se koriste u procesima parcijalne hidrogenizacije biljnih ulja. Izvršena je sinteza nekoliko uzoraka katalizatora precipitacijom jedinjenja nikla i odgovarajućih metala iz vodenih rastvora njihovih nitratnih soli na pripremljeni dijatomitni nosač korišćenjem natrijum karbonata (PDI katalizatori) i uree (DPU katalizatori) u svojstvu precipitanta. Obavljeni su obimni eksperimenti koji su obuhvatili ispitivanja uticaja uslova sinteze prekursora PDI- i DPUNi/ D katalizatora na stepen redukcije. Proučavanjem uticaja SiO2/Ni molskog odnosa i brzine zagrevanja na stepen redukcije prekursora PDI-Ni/D katalizatora utvrđeno je da manji SiO2/Ni m.o. i manje brzine zagrevanja povećavaju stepen redukcije. Ispitivanja uticaja DP vremena na stepen redukcije prekursora DPU-Ni/D katalizatora su pokazala da kraća DP vremena omogućavaju veći stepen redukcije. Fizičko-hemijska svojstva prekursora PDI- i DPU-Ni/D katalizatora okarakterisana su primenom sledećih metoda: (1) standardna kvantitativna hemijska analiza; (2) rendgenostrukturna (XRD) i infracrvena (IR) spektroskopija; (3) Hg-porozimetrija i N2-fizisorpcija; (4) temperaturno-programirana redukcija (TPR); (5) H2-hemisorpcija; (6) skenirajuća elektronska mikroskopija (SEM) i energo disperziona spektroskopija (EDS); (7) difuziono-refleksiona spektroskopija ultravioletne i vidljive oblasti (DR UV-Vis); i (8) fotoelektronska spektroskopija X-zraka (XPS). Rezultati rendgenostrukturnih (XRD) ispitivanja neredukovanih prekursora PDI- i DPU-Ni/D katalizatora su pokazali da se pored Ni2+ faze baznog nikl karbonata (PDI-Ni/D prekursori) i turbostratičnog nikl hidroksida (DPU-Ni/D prekursori) u prekursorima nalaze i Ni hidrosilikati nastali interakcijom aktivnog metala i nosača. Analizom XRD difraktograma redukovano-pasiviziranih prekursora, kao i in situ XRD-H2 difraktograma određene su veličine kristalita aktivnog metalnog nikla i metala modifikatora (Ag). Utvrđeno je da su veličine kristalita nikla manje od veličine kristalita srebra. Rezultati ispitivanja neredukovanih prekursora Ni/D katalizatora infracrvenom spektroskopijom (IR) su potvrdili prisustvo Ni2+ faza baznog karbonata i hidrosilikata i ukazali da je distribucija obrazovane Ni2+ faze više usmerena prema Ni hidrosilikatima nego prema baznom Ni karbonatu (PDI-Ni/D prekursori). Pokazano je da kod DPU-Ni/D prekursora priroda DP Ni2+ faze zavisi od DP vremena. Rezultati ispitivanja porozne strukture neredukovanih prekursora katalizatora metodom Hg-porozimetrije su pokazali da su ukupna intruziona zapremina pora, zapremina makropora, srednji prečnik pora i ukupna poroznost prekursora manji nego kod dijatomitnog nosača usled popunjavanja pora nosača metalnim solima aktivnog metala i odgovarajućih metala modifikatora. Utvrđeno je da sa porastom sadržaja srebra dolazi do povećanja zapremine makropora...Multicomponent catalytic systems consisting of active component (metallic Ni) and appropriate metals (Mg, Ag, Cu) deposited onto a prepared support (activated diatomite) were investigated, as well as their application as catalysts in the process of partial hydrogenation of edible oils. Starting material used for the synthesis of the catalyst support was raw diatomite from domestic sources (Baroševac diatomite deposit, eastern zone of the Kolubara coal basin). Raw diatomite properties were modified through chemical and thermal treatment resulting in a catalyst support with high silicon oxide content. Investigation of the textural properties and granulometric composition showed that the obtained catalyst support has macroporous structure and convenient granulometric composition appropriate for the obtention of Ni containing catalysts for the partial hydrogenation of vegetable oils. Synthesis of several catalyst samples was performed by the precipitation of Ni compounds and appropriate metals from aqueous solutions of their nitrate salts onto the prepared diatomite support, using sodium carbonate (PDI catalysts) and urea (DPU catalysts) as precipitants. Thorough experiments were carried out in order to investigate the influence of the PDI- and DPU-Ni/D catalyst precursor synthesis conditions on the degree of reduction. Investigation of the influence of the SiO2/Ni molar ratio and heating rate on the degree of reduction of the PDI-Ni/D catalyst precursor showed that lower SiO2/Ni molar ratio and lower heating rate increase the reduction degree. Investigation of the dependence of the degree of reduction on the DP time indicated that shorter DP times enable higher reduction degree. Physico - chemical characterization of the PDI- and DPU-Ni/D catalyst precursors was performed using the following methods: (1) standard quantitative chemical analysis; (2) X-ray diffraction (XRD) and infrared (IR) spectroscopy; (3) Hg-porosimetry and N2-physisorption (4) temperature-programmed reduction (TPR); (5) H2-chemisorption; (6) scanning electron microscopy (SEM) and energy dispersed spectroscopy (EDS); (7) diffuse reflectance UV-Vis spectroscopy (DR UV-Vis); and (8) X-ray photoelectron spectroscopy (XPS). Results of the XRD analysis of non-reduced PDI- and DPU-Ni/D catalyst precursors showed that, beside Ni2+ phases in the form of basic nickel carbonate (PDI-Ni/D precursors) and turbostratic nickel hydroxide (DPU-Ni/D precursors), there are also Ni hydrosilicates, originating in the interaction between the active metal and catalyst support. Analysis of XRD diffractograms of the reduced and passivated precursors and in situ XRD-H2 diffractograms was used for the size determination of metallic nickel and modifier metal (Ag) crystallites. Results of the investigation of non-reduced precursors of the Ni/D catalysts using IR spectroscopy confirmed the presence of Ni2+ phases of basic carbonate and hydrosilicates and indicated that the Ni hydrosilicate phase prevail comparing to that of Ni carbonate (PDI-Ni/D precursors). It was shown that in the DPU-Ni/D catalyst precursors the nature of Ni2+ phase depends on the DP time..

Buckling behaviour of dented aluminium alloy cylindrical shell subjected to uniform axial compression

Tankozide cilindrične strukture imaju veoma visoku primenu u industriji. Pošto su obično opterećene na aksijalni pritisak, najčešći uzrok njihovog otkaza je pojava izvijanja. U ovom članku se prikazuje numerička analiza izvijanja tankozide cilindrične strukture izrađene od legure aluminijuma sa imperfekcijom u vidu udubljenja na sredini strukture i eksperimentalna verifikacija rezultata dobijenih tom analizom. Numerička analiza je odrađena pomoću softvera ANSYS 16.2, a eksperimentalna ispitivanja pomoću hidraulične prese Armavir, PSU-50, na kojoj je uzorak podvrgnut aksijalnom pritisku čiji se intenzitet postepeno povećavao do pojave izvijanja. Poređenjem rezultata eksperimenta uočeno je značajno smanjenje vrednosti kritičnog napona na izvijanje između epruveta bez imperfekcije i epruveta sa imperfekcijom od 2 mm, dok su vrednosti kritičnog napona za epruvete sa imperfekcijama od 2 mm i 4 mm približne.Thin-walled cylindrical shells are commonly used in numerous branches of industry. Since they are subjected to axial load, the most common cause of their failure is buckling. This paper provides numerical analysis and experimental verification of the buckling of the thin-walled aluminium alloy cylindrical shell with special regard to the influence of dent, positioned in the middle of the shell. Numerical simulation was performed using ANSYS 16.2, and experimental verification was performed by means of hydraulic press Armavir, PSU-50, which was used to subject the specimen to the increasing axial load until the occurrence of buckling. Comparing the results it was concluded that there is significant decrease of the buckling resistance if compared the values of the specimen with no dent, and the specimen with 2 mm deep dent. On the contrary, resistance of the 2 mm and 4 mm dented specimen is quite similar. Position and shape of the deformations occurred due to buckling are matching if experimental and numerical results are compared

Preparation of Ni/diatomite hydrogenation catalyst precursors: Effect of counter ions on textural characteristics

Diatomite supported nickel catalyst precursors (Ni/D) were prepared by the precipitation-deposition (PD) method using different nickel salts such as nitrate, chloride, acetate and formate. The effect of counter ions (NO3-, Cl-, CH3COO-, and HCOO-) on the texture of prepared samples was studied. For determination of the textural characteristics mercury intrusion porosimetry (MIP) and N2 physisorption techniques were used. MIP and physisorption data (pore volume, pore size distribution, porosity as well as N2 adsorptiondesorption isotherms and BET surface area) showed that counter ions were found to have a profound effect on the microstructure and porosity characteristics of Ni/D precursors. An order of the counter ions effect on the textural characteristics of prepared precursors was determined

Calcium oxide on coal fly ash cancrinite-type zeolite as a catalyst for biodiesel production

This paper discloses the synthesis of new supported catalyst in which the main components of the catalyst, catalyst support and active component, derived from waste material, and its catalytic properties tested in the reaction of the production of biodiesel. Cancrinite-type zeolite catalyst support was synthesized from coal fly ash using hydrothermal technique with NaOH as the activation reagent in a rotating PTFE autoclave reactor. The active component, CaO, was derived from waste chicken eggshells by calcination at 900 °C. Supported catalytic material was synthesized by impregnation. The content of CaO in the prepared catalysts was varied from 5 to 20 wt%. The catalysts were characterized using XRD, FT-IR, SEM, N2-physisorption, and Hg-porosimetry. The methanolysis of sunflower oil was carried out in a batch reactor at 60 °C, with methanol to oil molar ratio of 12:1, and catalyst concentration of 4 wt.%. The fatty acid methyl ester content (% FAME) was analyzed using HPLC method. Structural information related to phase identification and vibration of chemical bonds in molecular units indicates that a multiphase zeolitic structure was obtained. The structure of cancrinite-type zeolite was found to be dominantly present. It was found that the catalyst impregnated with 20% of CaO gave the highest FAME percentage of 96.46 for the reaction time of 2 h

Preparation and characterization of clay and diatomaceous earth based porous ceramics with boric acid as additive

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Suzbijanje kukuruzove zlatice Diabrotica virgifera virgifera

Western corn rootworm (WCR) was registered for the first time in Europe near the Surčin international airport in Serbia in 1992. The spread of WCR on the territory of Serbia and its population density increased fast. The Serbian territory was entirely populated in the following few years, while major damages occurred on corn grown for two or more years in the same field. Data on damages caused to over 140,000 ha under corn until 1999 were collected by organized monitoring. After 2000 and 2003, population abundance of D.v. virgifera, as well as the number of damaged corn fields, significantly decreased due to drought and application of crop rotation. Corn rootworm has one generation per year. It overwinters in the egg stage. Under the climatic conditions of Serbia larvae hatching starts around May 15th. The highest number of larvae on root is observed around June 20th when feeding is most intensive and plants become lodged as they lose roots. First adults emerge by the end of June. Their abundance increases during July and reaches maximum by the end of the month. From the second decade of August the abundance decreases. Adults are present in the field until the first frosts. Larvae are much more harmful and significant than adults. Larvae feed on roots or into roots by boring. Roots can be entirely destroyed under heavy attack and the host plants lodged already at the end of June. Under our climatic and agrotechnical conditions, adults are sporadic pests. Adults are a threat only when sowing is done after the optimal sowing date or in case of stubble corn sowing. Crop rotation is an efficient and most widespread means of WCR control. No damage on corn grown in crop rotation has been registered in Serbia for now. In the first year of production corn does not require protection from Diabrotica virgifera virgifera LeConte larvae. Several insecticides have performed high efficacy by application at sowing and have been registered for commercial use. On the other hand, soil insecticides have never been applied on a significant area in Serbia.Kukuruzova zlatica je prvi put registrovana 1992. godine pored međunarodnog aerodroma Surčin. Širenje zlatice po teritoriji Srbije i porast gustine njene populacije je bilo brzo. Celokupna teritorija Srbije je naseljena u narednih nekoliko godina, pri čemu su se značajne štete javile na kukuruzu u ponovljenoj setvi. Sakupljeni su podaci o štetama na preko 140.000 ha kukuruza u periodu do 1999. godine. Posle 2000. i 2003. godine brojnost popualcije D.v. virgifera kao i broj oštećenih kukuruzovih polja je značajno smanjen zbog suše i masovne primene plodoreda. Kukuruzova zlatica ima jednu generaciju godišnje. Prezimljava u stadijumu jajeta. U klimatskim uslovima Srbije piljenje larvi počinje oko 15. maja. Najveći broj larvi se nalazi na korenu kukuruza oko 20. juna kada je ishrana larvi najintenzivnija. Zbog gubitka korena dolazi do poleganja biljaka. Odrasli insekti se javljaju krajem juna. Njihova brojnost raste tokom jula i dostiže maksimum krajem tog meseca. Od druge dekade avgusta brojnost imaga opada. Odrasli insekti se mogu naći u polju sve do prvih mrazeva. Larve se hrane na korenu ili se ubušuju u njega. U slučaju velikog napada koren može biti potpuno uništen i takve biljke već krajem juna poležu. U našim klimatskim i agrotehničkim uslovima odrasli insekti su sporadične štetočine. Oni mogu biti štetni u slučajevima kasnije setve ili postrne setve. Plodored je efikasan i najrasprostranjeniji način suzbijanja kukuruzove zlatice. Do sada se u Srbiji nisu javile štete na kukuruzu u plodoredu. Stoga se u kukuruzu u plodoredu ne primenjuju zaštitne mere. Više insekticida pokazuje dobre rezultate u suzbijanju kukuruzove zlatice kada se primenjuju sa setvom i imaju dozvolu za primenu u Srbiji. Međutim, zemljišni insekticidi nisu nikada do sada primenjeni na većim površinama za suzbijanje kukuruzove zlatice

Review of the past, present, and future of the hydrometallurgical production of nickel and cobalt from lateritic ores

Laterite ores are becoming the most important global source of nickel and cobalt. Pyrometallurgical processing of the laterites is still a dominant technology, but the share of nickel and cobalt produced by the application of various hydrometallurgical technologies is increasing. Hydrometallurgy is a less energy-demanding process, resulting in lower operational costs and environmental impacts. This review covers past technologies for hydrometallurgical processing of nickel and cobalt (Caron), current technologies (high-pressure acid leaching, atmospheric leaching, heap leaching), developing technologies (Direct nickel, Neomet) as well as prospective biotechnologies (Ferredox process)

Deactivation Aspects of Methanolysis Catalyst Based on CaO Loaded on Mesoporous Carrier

With the depletion of fossil fuels as a source for fuels and energy, the share of energy supplied by renewable resources such as biomass can be expected to increase in the anticipated future. Biodiesel, composed of fatty acid methyl esters (FAME), is one of the renewable alternative to fosil fuels which is most common obtained in catalyzed transesterification reaction of triacylglycerols (TAG). Naydays, the most promicing process is considered continuous basic heterogeneously-catalyzed methanolysis of sustainable sources of TAG. Heterogeneouslycatalyzed process has numerus advantages, but some drowbacks also exists. One of the main concern is catalyst stability and durability. The aim of this study is catalyst durability investigation and determination of the deactivation mechanisms on the case of CaO loaded onto mesoporous neutral carrier. The experiments were carried out in continuous packed bed tubular reactor (PBR) under mild reaction conditions. The CaO-based catalyst showed high activity in continuos reaction conditions during the first 30 h of operation, the FAME content was higher then 91.5%. After 30 h the catalyst activity began to decrease, so that after 36 h the FAME content was only 36%. The analysis of the morphology and the present functional groups on the surface of the catalyst before and after the reaction clearly showed a massive deposition of organic molecules from the reaction mixture on the surface of the catalyst. Since the loss of the active species by leaching was negligible, the sheltering of the catalytic active sites by such massive deposition of the organic molecule resulted in a decrease in the activity of the used CaO-based catalyst