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The focus of our study is the development of novel ceria-based materials that can be successfully used as catalysts in various environmentally friendly processes due to a significant improvement of ceria intrinsic characteristics. In particular, the combination of ceria with low-dimensional carbon materials such as graphene oxide (GO) and nanodiamond (ND) appears as a very promising approach. Actually, the decrease of ceria crystallite sizes deep in the nanoscale have been found to convert them into highly effective destructive adsorbent materials owing to their high surface area, strong adsorbability, and large number of highly reactive sites. Besides, the addition of a nanostructured carbon containing component (nanodiamond or graphene oxide) contributes to both mechanical and catalytic properties of the obtained nanocomposite hybrids. The results show that the novel ceria and ceria-based composite materials significantly outperform the hydrothermally obtained ceria catalyst used for comparison in both activity and selectivity to CO and hydrogen in the methanol decomposition reaction, and in the process of total oxidation of ethyl acetate due to their significantly improved redox behaviour and textural characteristics.

Refuse-derived fuel (RDF) is a mixed industrial waste, which often contains combustible materials (cellulose, polymers, rubber, biomass, etc.). The RDF waste precursor is subjected to thermo-oxidation treatment at 300℃, followed by carbonizations at 600℃, and high temperature hydropyrolysis at 800℃. The obtained nanoporous carbon material was subjected to detailed characterization by low temperature nitrogen sorption, elemental analysis, etc. Carbon derived from RDF is distinguished by micro/mesoporous texture and moderately high surface area (650 m2 g-1). The catalyst obtained is tested in the process of methanol decomposition, leading to production of hydrogen as a fuel. The influence of the physico-chemical characteristics of the synthesized carbon on the catalytic activity of carbon-based cobalt catalyst is studied.

Manganese oxide-based (MnOx) catalysts have received increasing attention due to their low cost, low toxicity, and the ability to degrade organic molecules under mild conditions. In this work, several nanostructured MnOx-based catalysts were prepared via redox reactions of manganese compounds in an aqueous solution and alkaline precipitation with aqueous ammonia. A wide arsenal of analytical techniques, including nitrogen physisorption (BJH and BET), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), and Raman spectroscopy were applied for their characterization. The nanostructured MnOx exhibited high catalytic activity in hydrolysis of phosphate diester-based substrate bis(4-nitrophenyl)phosphate (BNPP) at 328 K. Furthermore, MnOx specimens were also studied in decomposition of methanol to carbon monoxide and hydrogen as a potential alternative fuel. The results show high dependency of the materials catalytic properties on the synthesis method. It was found that the varying fractions of redox-active Mn2+/Mn3+/Mn4+ surface sites and the high proportion of oxygen species (such as O2− or O−) together with the particle dispersion and morphology are important for high catalytic activity of MnOx in both investigated catalytic reactions. Based on the experimental data, possible mechanisms of BNPP hydrolysis and methanol decomposition were proposed and discussed in detail.

Surface catalyzed reactions can be a convenient way to deactivate toxic chemical warfare agents (CWAs) and remove them from the contaminated environment. In this study, pure titanium oxide, magnesium hydroxide, and their composites TiO2/Mg(OH2) were prepared by thermal decomposition and precipitation of the titanium peroxo-complex and/or magnesium nitrate in an aqueous solution. The as-prepared composites were examined by XRD, XPS, HRTEM, and nitrogen physisorption. Their decontamination ability was tested on CWA surrogates and determined by high-performance liquid chromatography (HPLC) and gas chromatography coupled with mass spectrometry (GC-MS). Dimethyl methyl phosphonate (DMMP) was used as a G simulant for the nerve agents sarin (GB) and soman (GD) while 2-chloroethyl ethyl sulfide (2-CEES) and 2-chloroethyl phenyl sulfide (2-CEPS) were used as surrogates of sulfur mustard (HD). The activity of the as-prepared composites was correlated with acid–base properties determined by potentiometric titrations and pyridine adsorption studied by in situ DRIFTS. The mixing of Ti and Mg led to an increase of the surface area and the amount of surface –OH groups (with an increasing amount of Ti) that caused improved degradation of DMMP.

This study is aimed at the development of intelligent approach for clean energy production via valorization of industrial waste by-products. The proposed scheme is based on the preparation of activated carbon based catalysts for methanol decomposition as a source of hydrogen. Peach stones from the canning industry and by-products from low-rank coals treatment, all of them widely available in the Balkan region, are used as activated carbon precursors. The specific effect of carbon support on the formation of the loaded active NixZn1-xFe2O4 (x = 0; 0.2; 0.8; 1) ferrite phase are studied by nitrogen physisorption, XRD, HRTEM, FTIR, Moessbauer spectroscopy, TPR with hydrogen and Boehm method. To precise the discussion, analogues KIT-6 silica modifications are used as reference samples. It was found that the hosted in the activated carbon metal containing phase represents a complex mixture of Ni and/or Zn substituted magnetite, NiFe alloys, metallic Fe and ZnO. Its composition and dispersion is controlled by the variation of the Ni/Zn ratio and the texture peculiarities of the carbon support, the latter being easily tuned by the waste precursor used. The NixZn1-xFe2O4 modified activated carbons obtained from peach stones and coal treatment by-products possess a significant potential for sustainable environmental protection as cheap and effective catalysts for hydrogen production.

A series of titania-tin oxide binary nanosized mesoporous materials with various composition were successfully obtained by template assisted hydrothermal technique. They were characterized by nitrogen physisorption, XRD, TEM, XPS, UV-Vis, FTIR of adsorbed pyridine and Raman spectroscopes. The reduction properties of the composites were studied by TPR with hydrogen. Two environmental feasible processes, such as total oxidation of ethyl acetate as representative VOCs and decomposition of methanol as hydrogen source, which are also sensitive both to the surface and redox properties of the solids, were used as catalytic tests. On the base of detailed analyses of the data from the complex physicochemical study and comparison with the reference samples, obtained by homogeneous precipitation with urea, a possible mechanism of the formation of TiO2-SnO2 binary materials was proposed and discussed in a view of catalyst design control.

This work is focused on the preparation of Ni0.5M0.5Fe2O4 mixed ferrites (M = Zn or Cu), supported on nanoporous carbons materials. The carbon supports are obtained from various waste residues, such as peach stones from the canning industry and by-products from the low rank coals pyrolysis. X-ray diffraction (XRD), nitrogen physisorption, high-resolution transmission electron microscopy (HRTEM), Moessbauer spectroscopy and temperature programmed reduction (TPR) analyses as well as mesoporous silica with tridimensional structure type KIT-6 silica based reference samples are used for detail characterization of the obtained materials. It was established that the loaded on the carbon supports phase is a complex mixture of finely dispersed ferrite, substituted magnetite, metal (Cu, Fe, FeNi alloy) and ZnO particles. Their dispersion and composition depend on the texture characteristics of the carbon support, which could be easily controlled by the waste precursor used. The existence of mesoporosity in the carbon host matrix provokes the formation of more finely dispersed and easily reducible spinel particles, which ensures higher initial catalytic activity, but fast deactivation of the catalysts. The formation of activated carbon mesoporosity is facilitated by the presence of cellulose and hemicellulose in the biomass or the addition of furfural to the coal tar pitch precursor. The Ni0.5Zn0.5Fe2O4 modifications demonstrate higher potential as catalysts for hydrogen production via methanol decomposition.

A series of mesoporous cerium–iron binary oxides was prepared by a hydrothermal technique using CTAB as a template. The influence of the Fe/Ce ratio and the variations in the preparation techniques such as the type of solvent and the precipitation agent, the approach of the template release, and the temperature of calcination on the phase composition, textural, structural, surface, and redox properties of the obtained materials was studied in details by XRD, nitrogen physisorption, TPR, FTIR, UV–vis, XPS, Raman, and Moessbauer spectroscopies. The materials were tested as catalysts in methanol decomposition and total oxidation of ethyl acetate. It was assumed that the binary materials represented a complex mixture of differently substituted ceria- and hematite-like phases. Critical assessment of their formation on the base of a common mechanism scheme was proposed. This scheme declares the key role of the formation of shared Ce–O–Fe structures by insertion of Fe3+ in the ceria lattice and further competitive compensation of the lattice charge balance by the existing in the system ions, which could be controlled by the Fe/Ce ratio and the hydrothermal synthesis procedure used. This mechanism provides proper understanding and regulation of the catalytic behavior of cerium–iron oxide composites in methanol decomposition with a potential for hydrogen production and total oxidation of ethyl acetate as a model of VOCs.

Surface catalyzed reactions can be a convenient way to deactivate toxic chemical warfare agents (CWAs) and remove them from the contaminated environment. In this study, pure titanium oxide, magnesium hydroxide, and their composites TiO

Template assisted hydrothermal and homogeneous precipitation with urea techniques were used for the preparation of TiO2-ZrO2 binary oxides with wide range variation of their composition. Low temperature nitrogen physisorption, XRD, SEM, HRTEM, XPS, UV–vis, FTIR, FTIR of adsorbed pyridine and Raman spectroscopy were used for the characterization of the obtained samples. Their catalytic properties were tested in total oxidation of ethyl acetate as a representative VOCs and methanol decomposition as hydrogen carrier. It was established that the template assisted hydrothermal technique provoked preparation of materials with good crystallinity, high BET surface area and well developed mesoporous structure, while the homogeneous precipitation with urea method facilitated the formation of more highly dispersed in wide Zr/Ti region samples. The degree of incorporation of Zr4+ ions into titania lattice could be controlled by the samples composition and the preparation method used, which revealed good opportunity for effective and simple regulation of their catalytic properties.

High surface area mesoporous ceria-titania binary materials with high Lewis acidity and improved reduction properties were synthesized using template assisted hydrothermal technique. The obtained materials were characterized by low temperature nitrogen physisorption, XRD, SEM, TEM, Raman, UV–vis, XPS, FTIR, FTIR of adsorbed pyridine and thermo-programmed reduction with hydrogen. Their catalytic activity was tested in total oxidation of ethyl acetate and methanol decomposition to CO and hydrogen with a potential application in VOCs elimination and alternative fuels, respectively. The structural changes in the binary materials, which could be tuned by the variation in the Ce/Ti ratio and the temperature of hydrothermal treatment, provoked significant changes in their textural, surface and redox properties, which is in close relation to the catalytic activity and selectivity in various catalytic processes. The intimate contact between the individual oxides results in the formation of different catalytic active sites and their role in the studied catalytic reactions was discussed in details.

Hydrothermally obtained mesoporous ceria-titania mixed oxides with different composition are modified with copper using incipient wetness impregnation and “chemisorption-hydrolysis” techniques. Their catalytic properties in methanol decomposition as a source of hydrogen and total oxidation of ethyl acetate as representative volatile organic pollutant are investigated. The effect of support composition and modification method on the formation of catalytic active sites is studied. The obtained results show that the catalytic behavior is determined by the activity of finely dispersed CuO crystallites and facile electron transfer in the “conjugated” Ti Ce Cu redox centres in the interface layer. The mechanism of the formation of the interface layer and the growth of CuO crystallites during different modification procedures are discussed in details. The mesoporous Cu Ce Ti oxides demonstrate excellent catalytic activity in total oxidation of ethyl acetate. Their catalytic behavior in methanol decomposition is strongly influenced by the reductive transformations, which are provoked by the reaction medium.

Agriculture residues (grape seeds, peach, apricot and olive stones) were used as a precursor of activated carbons with tunable textural characteristics and relatively low surface functionalities (predominantly carbonyl and hydroxyl groups). Thus obtained activated carbons were modified with iron species and tested as catalysts in methanol decomposition. Nitrogen physisorption, XRD, UV–Vis, FTIR, Moessbauer spectroscopy, TPR with hydrogen and Boehm method were applied for complex characterization of the initial activated carbon supports, their iron modifications and the transformations during the catalytic process. The final phase composition and the related with this catalytic activity and selectivity of these materials was considered as a result of complex transformations of active phase by the influence of activated carbon support and reaction medium and this is in close relation with the dispersion and location of iron species into the porous matrix. The decisive role of activated carbon texture characteristics, which is much more significant than the surface functionalities, on the formation of iron catalytic sites is established, and the variation in the nature of the agriculture precursor is assumed as a simple approach for tailoring their properties.

Ordered mesoporous silica of SBA-15 type and activated carbon, prepared from waste biomass (peach stones), are used as host matrix of nanosized iron and cobalt particles. The effect of preparation procedure on the state of loaded nanoparticles is in the focus of investigation. The obtained materials are characterized by Boehm method, low temperature physisorption of nitrogen, XRD, UV–Vis, FTIR, Mossbauer spectroscopy and temperature programmed reduction with hydrogen. The catalytic behaviour of the samples is tested in methanol decomposition. The dispersion, oxidative state and catalytic behaviour of loaded cobalt and iron nanoparticles are successfully tuned both by the nature of porous support and the metal precursor used during the samples preparation. Facile effect of active phase deposition from aqueous solution of nitrate precursors is assumed for activated carbon support. For the silica based materials the catalytic activity could be significantly improved when cobalt acetylacetonate is used during the modification. The complex effect of pore topology and surface functionality of different supports on the active phase formation is discussed.

Activated carbons (AC) from various waste agriculture precursors with different texture and surface characteristics were obtained by different preparation procedures. These AC were used as a host matrix of mono- and bi-component copper and cobalt nanoparticles. The effect of carbon properties on the formation of copper/cobalt phases was studied by Boehm method, XRD, nitrogen physisorption, UV–Vis, FTIR, TPR–TG analysis and methanol decomposition as a catalytic test. The elucidation of activated carbons from waste biomass as catalyst support was based on the comparative study with similar materials supported on mesoporous silica KIT-6. It was demonstrated that contrary to KIT-6, the reduction properties of AC support hinders the formation of spinel CuCo2O4 phase in the bi-component materials, but provides formation of mixture of finely dispersed and highly active and selective in methanol decomposition Cu2O and CoO nanoparticles.

Copper, iron and cobalt supported on activated carbon materials are compared as catalysts in methanol decomposition in view of their potential application as intelligent carriers of hydrogen. The activated carbon supports were obtained from renewable agriculture waste (peach shell) or coal treatment by-products (coal tar pitch). The parent activated carbons and their transition metal modifications were characterized by nitrogen physisorption, XRD, UV–Vis, FTIR, Mossbauer spectroscopy and TPR in hydrogen, and the surface functional groups were determined by the Bohm method. It was assumed that the formation of transition metal modified activated carbon catalysts is a complex process which proceeds during the preparation procedure with the activity of the support and also during the catalysis by the influence of the reaction medium. The decisive effect of carbon basal planes over the texture and surface functionality of the support on the formation of transition metals active phase was assumed. Among the studied materials, cobalt modifications exhibited excellent catalytic activity and selectivity in methanol decomposition to H2 and CO despite the nature of the activated carbons used.

A series of copper and manganese oxides modified SBA-15 mesoporous silicas with different composition was prepared by incipient wetness impregnation with the corresponding nitrate precursors and compared with the analogous materials supported on conventional SiO2. Nitrogen physisorption, XDR, FTIR, UV–Vis and temperature programmed reduction with hydrogen were used for samples characterization. Their catalytic activity was tested in ethyl acetate oxidation and methanol decomposition. The ordered porous structure of the support facilitates the interaction between different metal oxide nanoparticles and increases their dispersion due to the formation of mixed oxide phase. The ethyl acetate oxidation on SBA-15 binary materials is suppressed due to the lower accessibility of the metal oxide particles, located deeply into the micro-meso pores of the support. The reaction medium which forms during the methanol decomposition provides the reduction/decomposition transformations with the mixed oxide phase. The final phase composition of finely dispersed Cu/CuO and MnOx particles stabilizes in a highly dispersed state into the porous matrix of SBA-15 support and increases the catalytic activity in methanol decomposition due to the appearance of synergistic effect between them.

[EN] Copper and cerium oxide bi-component materials with different Cu/Ce ratio were prepared using ordered SBA-15 silica as a support and compared with their bulk analogs. The samples were characterized by nitrogen physisorption, XRD, UV-Vis, FTIR, XPS, Raman spectroscopy and TPR with hydrogen. Cyclohexanol conversion was used as a catalytic test to obtain more information for the surface properties of the supported materials. The catalytic properties of the samples were studied in VOCs oxidation using toluene and ethyl acetate as probe molecules. A strong effect of mesoporous silica support and samples composition on the formation of catalytic sites was established. (C) 2012 Elsevier B.V. All rights reserved., Financial support of Bulgarian Academy of Science and National Scientific Fond of Ministry of Education Projects DTK 02/64 and ДНTC/Киtай 01/8, financial support from DGICYT in Spain (Project CTQ-2009-14495) and bilateral project Bulgarian-Spain Inter-academic Exchange Agreement (Project 2009BG0002) are acknowledged.

[EN] Copper and cerium bi-component modifications of KIT-6 were prepared by wetness impregnation technique from the corresponding nitrate precursors. Nitrogen physisorption, XRD, FTIR of adsorbed CO, UV-Vis, XPS and TPR were used for their characterization. The catalytic activity of the obtained materials was tested in ethyl acetate oxidation and compared to those achieved over SBA-15-supported catalysts. It was established that the interaction between copper and ceria species results in the formation of finely dispersed CuO nanoparticles on the ceria ones, which are stabilized by an interface layer of penetrated into the ceria lattice copper ions in different oxidative state. This process seems to be facilitated in the more opened 3D-structure of KIT-6, which provides better catalytic activity even at high Cu/Ce ratio than those observed for the SBA-15 modifications. (C) 2013 Elsevier Inc. All rights reserved., Financial support of projects BG051PO001-3.3.05-0001 "Hay kappa a (sic) O(sic)(sic)iiec", (sic)HTC/kappa(sic)Ta(sic) 01/8, CTQ2012-37925-0O3-01 (DGCYT, Spain) and bi-lateral project Bulgarian-Spain Inter-academic Exchange Agreement (Project 2009BG0002) are acknowledged.

[EN] The formation of active sites in the silica supported copper and cerium oxide hi-component catalysts for total oxidation of ethyl acetate was studied by Nitrogen physisorption, XRD, XPS, UV-Vis, Raman, FTIR of adsorbed CO spectroscopies and TPR. It was found that the interaction between the copper oxide nano-particles and the supported on the silica ceria ones is realized with the formation of interface layer of penetrated into ceria lattice copper ions in different oxidative state. This type of interaction improves the dispersion of copper oxide particles and provides higher accessibility of the reactants to the copper active sites even at low copper amount. (C) 2013 Elsevier Inc. All rights reserved., The paper is published with the support of Project No. BG051PO001-3.3-05/0001. Financial support of BAS, FNI of Bulgarian Ministry of Education, Project (sic)HTC/(sic)01/8, DGICYT in Spain (Project CTQ2012-37925-C03-01) and bilateral project Bulgarian Spain Inter-academic Exchange Agreement (Project 2009BG0002) are also acknowledged.