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A novel route to prepare monodispersed 1–2 nm gold nanoparticles (NPs), based on the use of extremely small SiO2 NPs (2–4 nm) as a support and increasing their metal-support interaction with surface modifier oxides is presented. The influence of modifier (La, Ce and Fe oxides) and modification method (impregnation (i) or direct synthesis (s)) on the formation of ultra-small Au NPs and their structural and electronic properties was studied. The samples were characterized by N2 adsorption (BET), FTIR of adsorbed CO, XRD and HR-TEM methods, and tested for the catalytic selective oxidation of 1-octanol. Preparation of monodispersed Au NPs with 1 nm diameter was successfully achieved for all the modified samples studied, with exception of Au/Ce/SiO2-i, where CeO2 was not homogeneously distributed. The Au NPs have high degree of monodispersity and are stable when treated in H2 up to 300 °C. Formation of these Au NPs depended on the strong interactions between the cationic gold complex precursor and the surface of modified SiO2 NPs. Modifiers changed electronic properties of supported gold; favoring the formation and stabilization of Auδ+ states, which are probable gold active sites of selective liquid-phase oxidation of alcohols in redox catalytic processes. 1-octanol oxidation was used as a model reaction for oxidation of fatty alcohols obtained during biomass transformation. The best performance for 1-octanol oxidation was found for gold nanoparticles supported on the ultra-small SiO2 modified cerium oxide by impregnation method. The relative order of activity was: AuCeSiO2-i > AuFeSiO2-i ≫ AuLaSiO2-i ≈ AuLaSiO2-s > AuSiO2 > AuFeSiO2-s≫ AuCeSiO2-s. The obtained results open the possibility of further development of high-performance catalysts for conversion of secondary products of biomass processing into valuable chemicals.

Influence of modification with metals Au and Ag, oxides of Fe, Mg and Ce and their combinations on amorphization of widely used commercial nanosized TiO2 (Degussa P25) was studied with SR-XRD and EXAFS methods. These systems were chosen taking into account their potential on catalytic properties for biomass to biodiesel transformation, as it was shown in model reaction of liquid phase n-octanol oxidation as well as low-temperature CO oxidation for “cold start” of the neutralizers of car exhaust gases. Instability of rutile, the most stable TiO2 phase, in the presence of the additives was found. Application of EXAFS method, rarely used for crystalline structure transfer studies, led to elucidation of this apparent effect, which was explained by higher level of amorphization of rutile than anatase. Literature data indicate that bulky TiO2 doping leads to either increase of rutile/anatase ratio complete inhibition of anatase to rutile transformation. Dissimilar phase composition changes, revealed in this work for modified nanodispersed TiO2, was attributed to size effect.

Silver supported on the ZSM-5 (ratio Si/Al = 50) were prepared by impregnation method and characterized by means of numerous analytical techniques: high resolution transmission electron microscopy (HRTEM), Fourier transformed infrared spectroscopy (FTIR) and diffuse reflectance UV–vis spectroscopy (DRS). Catalytic activities of the materials were evaluated in CO oxidation. It was shown that catalytic performance of x Ag/ZSM-5 ( x = 1, 3, 5, 7 wt.% Ag) depends strongly on Ag loading, among which 7%Ag/ZSM-5 displayed the best properties for the studied reactions. The studies revealed a strong influence of the redox pretreatment temperature on the catalytic activity of the samples. The experiments showed that Ag/ZSM-5 catalyst has a good reproducibility and stability in CO oxidation. Comparison of results of catalytic, structural and spectroscopic measurements allows suggesting Ag + ions inside zeolite or on the external support surface as well as charged clusters Ag n δ+ to be active states of silver in the studied process. The obtained results were compared with previous data for formation of active gold clusters Au n δ+ in zeolites. It is important for synthesis of catalytically stable bimetal Au–Ag systems.

The influence of pretreatments with He, O 2 and H 2 on the physicochemical and catalytic properties of gold supported on hexagonal mesoporous silica (HMS) has been studied by a variety of methods including: XPS, TPR, N 2 sorption, UV–visible spectroscopy, FTIR and catalytic testing. The investigations show supported gold to form different states under redox treatments: Au 3+ and Au + ions, neutral and partly charged gold clusters and metal nanoparticles of different sizes. Reducing pretreatments increase the catalytic activity of the samples; while oxidative treatments deactivate the catalyst. Catalytic tests show several regions of the reduced samples with various catalytic behaviours: 20–200 °C, 200–400 °C and >400 °C; this situation is explained by the co-existence of gold active sites of different types. A comparative analysis among spectroscopic and catalytic data allows suggesting Au n δ + clusters to be responsible for the activity in the low-temperature region ( n clusters are active in the range 200–400 °C; and gold nanoparticles may catalyze high-temperature CO oxidation. Au 3+ ions are inactive in this process.

Role of small and big gold particles in CO oxidation and methanol selective oxidation to formaldehyde has been studied by the methods of diffuse reflectance electron spectroscopy, XRD, XPS, HRTEM and catalytic testing. By comparison of catalytic and spectroscopic data it was concluded that states Auδ+ with certain effective charge (δ < 1) are active sites in low-temperature CO oxidation as well as in alcohol partial oxidation. These states can be formed under the action of different factors, such as metal–support interaction, redox treatments, and modifying additives. Modifiers stabilizing the ionic states of gold (Ce and Zr oxides) increase the selectivity of the catalyst in alcohol partial oxidation, whereas electron-releasing additions (La and Cs oxides) impair the catalyst properties.