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In the presented research, Ni-based catalysts were synthesized. Reticulated α-Al2O3 based foams were impregnated with ultrasonically aerosolized NiCl2 and NiCl2-PdCl2 aqueous solutions, dried at 473 K for 1 h and then reduced by hydrogen at 533 and 633 K for 90 min. Ni loading was 5 wt.%. Modified catalyst contained 0.1 wt.% of added Pd. Reduction of Ni-Pd/Al2O3 sample was almost completed at 533 K. The calcination step was avoided and lower reduction temperature was utilized. Proposed method enables formation of submicron-sized metallic particles and offers a possibility of economical and technological benefits in the catalysts production process.

In the present investigation, nanostructured Ni/Al2O3 catalyst supported on reticulated alumina-mullite foam was synthesized by aerosol assisted coating. The synthesis process was optimized from the technological and economic aspect. Ultrasonically generated NiCl2 water solutions were applied to α-Al2O3-mullite foam in a tubular quartz reactor. The first procedure involved calcination at 773 K for 1 h in order to obtain NiO/Al2O3 precursor. The second procedure involved drying at 473 K for 1 h without oxidation. The activation step involved hydrogen reduction at 633 K. The effectiveness of the low-temperature hydrogen reduction was compared for those systems. It was determined that the samples were reduced in a high degree at 633 K for 90 minutes and the hydrogen flow rate of 20L/h. However, SEM of calcined sample shows presence of agglomerates. The samples reduced from NiCl2 had no agglomerates and the metallic phase was homogeneously dispersed compared to the samples obtained by NiO reduction. The most probable reason for the effective low-temperature reduction was the formation of thin coatings consisted of oxide and chloride precursors for the catalytically active components. XRD analyse of the samples after the reduction at 633 K for 90 minutes showed only metallic nickel, alumina and mullite phases. Residual phases of NiO and NiCl2, as well as NiAl2O4, were not detected. The production process can be simplified and economically more favourable by avoiding the calcination step.

Considering that nanostructural materials are expected to have special physical and mechanical properties, in the recent years the examinations of synthesis and characterization of the nanocomposite system attracts even greater scientific interest. This paper presents production of sintered contacts materials produced from nanocomposite powders obtained by combination of thermochemical synthesis of Cu-Al2O3 powder and mechanical alloying of atomized copper powder with previously sinthetized Cu-Al2O3 powder. Produced powders were characterized by X-ray diffraction and Analytical Electron Microscopy. Characterization of sintered samples included Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometry (EDS), measurement of hardness and specific electrical conductivity. By thermochemical method of Cu-Al2O3 nanocomposite synthesis, i.e. deposition from aqueous solutions, in combination with mechanical alloying, significant effects of reinforcement were achieved as a result of homogenous distribution of alumina in the nanocomposite system. In combination with conventional methods, thermochemical process of nanocomposite powders synthesis could be successfully applied for synthesis of new nanocomposite catalysts, which are characterized by a high degree of dispersion of the catalytically active component, respectively the catalyst with high activity and selectivity. The high degree of dispersion is the result of uniform distribution of the catalytically active component into alumina suspension, realized during the thermochemical treatment in the synthesis of nanocomposite catalysts. In accordance with this, the paper shows the synthesis of Ni/Al2O3 and Ni-Pd/Al2O3 nanocomposite catalysts with homogeneously dispersed Ni particles, as catalytically active component, and Pd, as activity modifier, supported on ceramic Al2O3 based foam. Namely, the previous synthesized monolith was soaked in a mixed alumina suspension with NiCl2, PdCl2 and appropriate organic additives in order to obtain a nanocomposite catalysts with homogeneous distribution of catalytically active components. Characterization of obtained Al2O3 foam, as the active catalytic components primary carrier, and synthesized nanocomposite catalysts included SEM, EDS, gas permeability and mechanical properties. Synthesis of nanocomposite materials with homogeneous distribution of particles on the nanometer level may lead to formation of new materials with improved or even unexpected properties.

This PhD thesis presents investigations on possibilities of development of synthesis method for monolythic catalytic materials based on Ni-Pd/Al2O3 system, where the calcination step is eliminated. Catalytic properties of Ni-Pd/Al2O3 catalysts were investigated in the process of dry methane reforming. The catalysts were synthesized by an innovative method that included a combination of thermochemical process and ultrasonically generated aerosols utilization. In the initial phase of research, the comparative kinetic analysis of the NiO and NiCl2 reduction by hydrogen during an induction period was conducted. Obtained results show that activation energy of NiCl2 reduction process (28 kJ/mol) was slightly lower in comparison with activation energy of NiO reduction (29 KJ/mol). On the basis of those results, it was concluded that the chloride precursor for Ni can be used in the catalyst synthesis process. By using chlorides, calcination step can be eliminated during the process of catalysts production, which contributes to the process simplification and energy savings. In the further course of this research, it was proven that modification with additives 0.1 % Pd, 1.0 % Cu and 1.0 % Fe (wt. %) results in increased NiCl2 reduction degree in hydrogen atmosphere at low temperatures (533-653 K). The addition of Pd exhibits the most pronounced effect due to the splitting of molecular hydrogen to atoms: 58.2 wt. % of NiCl2 is reduced for 24 minutes at 653 K. The resulting value is considerably higher than the reduction degree of NiCl2 without additives under the same conditions (5.0 wt. %). Synthesis of the catalysts is carried out in three basic stages. In the first stage, monolithic ceramic foams based on alumina (α-Al2O3) are prepared by using a polymer network/model replication. Obtained ceramic foams serve as the carriers i.e. bases for the catalytically active particles. The second and third stage involve deposition of catalytically active layer to the ceramic foams and the hydrogen reduction, respectively. Presented method of catalyst synthesis was developed in order to obtain catalysts with enhanced properties and achieve simplification and energy savings, compared to conventional methods. During the research, optimization of relevant parameters of each phase of the catalyst synthesis process was carried out. In the presented research, optimal process parameters of each synthesis process stage were determined. During production of α-Al2O3 based foams, characterization of the following materials was carried out: powders for the preparation of aqueous ceramic suspensions (SEM), ceramic suspensions (viscosity, specific mass), polymer models and green bodies (stereo microscopy, quantification of visual information) and sintered foams (linear shrinkage degree, volume porosity, SEM, mechanical properties). In the catalyst... U doktorskoj disertaciji su prikazana ispitivanja mogućnosti razvoja postupka sinteze monolitnih katalitičkih materijala na bazi sistema Ni-Pd/Al2O3 uz eliminaciju koraka ņarenja. Upotrebna svojstva Ni-Pd/Al2O3 katalizatora ispitana su u procesu suvog reformiranja metana. Katalizatori su sintetisani inovativnom metodom koja podrazumeva kombinaciju termohemijskog postupka i korińćenje ultrazvučno generisanih aerosola. U početnoj fazi rada, izvrńena je uporedna analiza kinetike redukcije NiO i NiCl2 vodonikom tokom indukcionog perioda. UtvrĎeno je da je energija aktivacije procesa redukcije NiCl2 (28 kJ/mol) neńto niņa u odnosu na energiju aktivacije redukcije NiO (29 KJ/mol), na osnovu čega je zaključeno da se u postupku sinteze katalizatora moņe koristiti hloridni prekursor za Ni. Korińćenjem hlorida se u postupku proizvodnje katalizatora eliminińe korak ņarenja, ńto doprinosi pojednostavljenju postupka i uńtedama energije. U daljem toku istraņivanja, dokazano je da se modifikovanjem dodacima 0,1 % Pd, 1,0 % Cu i 1,0 % Fe (mas. %) postiņe povećanje stepena redukcije NiCl2 vodonikom na niskim temperaturama (533-653 K). Dodatkom Pd se postiņe najizraņeniji efekat usled razdvajanja vodonika na atome: za 24 minuta se na 653 K redukuje 58,2 mas.% NiCl2. Ova vrednost je mnogo veća u odnosu na stepen redukcije NiCl2 bez dodataka u istim uslovima (5,0 mas.%). Sinteza katalizatora se odvija kroz tri osnovne faze. U prvoj fazi vrńi se priprema monolitnih keramičkih pena na bazi korunda (α-Al2O3) metodom replikacije polimerne mreņe/modela. Keramičke pene predstavljaju nosač odnosno osnovu za katalitički aktivne čestice. Druga i treća faza podrazumevaju nanońenje katalitički aktivnog sloja na keramičke pene i redukciju vodonikom, respektivno. Predstavljena metoda sinteze katalizatora je razvijena u cilju dobijanja katalizatora poboljńanih svojstava, uz pojednostavljenja i uńteda energije u odnosu na konvencionalne metode. U toku rada, izvrńena je optimizacija relevantnih parametara svake faze procesa sinteze katalizatora. Tokom sinteze pena na bazi α-Al2O3, izvrńena je karakterizacija sledećih materijala: prahova za pripremu vodenih suspenzija keramike (SEM), keramičkih suspenzija (viskoznost, specifična teņina), polimernih modela i zelenih tela (stereo mikroskopija, kvantifikacija vizuelnih informacija) i sinterovanih pena (stepen linearnog skupljanja, zapreminski udeo poroznosti, SEM, ispitivanje mehaničkih svojstava). Tokom sinteze i ispitivanja upotrebnih svojstava katalizatora, izvrńena je karakterizacija meĎuproizvoda i krajnjih proizvoda različitim instrumentalnim metodama (SEM, XRD, stepen redukcije vodo...