The aim of this study was to get insight into the pathway of the acetaldehyde formation from ethanol (the rate-limiting step in the production of 1,3-butadiene) on Cu-SBA-15 and Cu-MnSBA-15 mesoporous molecular sieves. Physicochemical properties of the catalysts were investigated by XRD, N2 ads/des, Uv-vis, XPS, EPR, pyridine adsorption combined with FTIR, 2-propanol decomposition and 2,5-hexanedione cyclization and dehydration test reactions. Ethanol dehydrogenation to acetaldehyde (without and with oxygen) was studied in a flow system using the FTIR technique. In particular, the effect of Lewis acid and basic (Lewis and BrØnsted) sites, and the oxygen presence in the gas reaction mixture with ethanol on the activity and selectivity of copper catalysts, was assessed and discussed. Two different reaction pathways have been proposed depending on the reaction temperature and the presence or absence of oxygen in the flow of the reagents (via ethoxy intermediate way at 593 K, in ethanol flow, or ethoxide intermediate way at 473 K in the presence of ethanol and oxygen in the reaction mixture).

Bifunctional catalysts-e.g., those with acidic and redox sites-are of particular importance, especially in the cascade processes, including the one-pot transformation of glycerol to acrylic acid. In this study, we explore one aspect of the preparation of a vanadium-containing catalyst, which can be further modified with 3-(trihydroxysilyl)-1-propanesulfonic acid (TPS). The state of vanadium species loaded on mesoporous ordered silica of SBA-15 type was investigated before and after treatment with TPS, which can also be applied for the generation of acidic centers. Two vanadium sources, i.e., ammonium metavanadate and vanadium(IV) oxide sulfate, were applied to generate redox sites on SBA-15. The structure of materials obtained was analyzed using N-2 adsorption/desorption and XRD measurements. For the estimation of the amount of vanadium and characterization of its state, the following techniques were applied: ICP, UV-Vis, XPS, ESR and FTIR combined with pyridine adsorption. The treatment of vanadium containing SBA-15 with TPS was found to lead to the oxidation of V4+ to V5+ and the partial removal of vanadium species, leading to a decrease in the number of penta-coordinated vanadium species. These features should be taken into account in the design of bifunctional catalysts with vanadium-active centers and SO3H acidic sites coming from TPS.

•Location of Nb and Ce species on MCF was influenced by modification methods.•Step by step modification led to Nb sited in MCF skeleton and CeO2 surrounded NbO−.•One pot modification caused formation of Nb and Ce oxides interacting synergistically.•Acidity and basicity of catalysts strongly depended on metals location in MCF.

The goal of this work was to use ZnO as a support for gold and copper (Au-Cu system) or gold and silver (Au-Ag system) and comparison of the effect of copper and silver on the properties of gold and its activity in glycerol oxidation with oxygen in the liquid phase. The samples prepared were fully characterized by XRD, TEM techniques and UV-vis, XPS, ESR spectroscopic methods. It was found that the introduction of copper and silver changed the electronic state of gold loaded on ZnO by the electron transfer between metals. Three different metallic gold species were identified in calcined catalysts: (Au degrees)(delta-) (Au-ZnO), (Au degrees)(eta) (AuCu-ZnO) and (Au degrees)(gamma) (AuAg-ZnO), where delta, eta, gamma indicate a different partial negative charge on metallic gold and gamma > delta > eta. The results showed that (Au degrees)eta centers (metallic gold with the lowest negative charge) formed on AuCu-ZnO were the most active in glycerol oxidation. The increase in the negative charge on metallic gold loaded on AuAg-ZnO reduced the gold activity in silver containing sample. The glyceric acid adsorption and desorption rate influenced the selectivity of the catalysts. (C) 2018 Elsevier B.V. All rights reserved.

A mixture of antiferromagnetic Cu1.4Mn1.6O4 and Cu0.5Zn0.5Mn2O4 or/ and ZnMn2O4 spinels was prepared. Dealuminated HY zeolite and silica were doped by these Cu-Mn-Zn spinels. The materials were investigated by X-ray diffraction, the Fourier transform infrared spectroscopy and EPR spectroscopy. Additionally, all the samples were tested for their activity for isopropyl alcohol dehydration/dehydrogenation. Three EPR signals were observed for Cu-Mn-Zn/dealuminated HY and Cu-Mn-Zn/SiO2 samples at 293 K. In contrast to the spectra recorded at 293 K, only one broad line attributed to Cu-Mn-Zn spinels was visible at 77 K. The EPR signal from pure Cu-Mn-Zn spinels consists only of a single broad line when recorded at 293 K, whereas at 77 K the line is narrower. For all samples subjected to evacuation at high vacuum up to 573 K, the Cu-Mn-Zn spinels were stable. The evacuation at 673 K resulted in a rapid lowering of the intensity of EPR spectrum.

MCF (Mesostructured Cellular Foams) and Zn/MCF were used as supports for gold and copper. The effect of zinc and copper on the surface properties, activity and selectivity of gold catalysts in the methanol oxidation was studied. The catalysts were characterized in detail by XRD, TEM, UV–Vis, XPS, ESR and FTIR-NO. The results showed that zinc oxide species play the role of a structural promoter which protects against agglomeration of gold species and an electronic promoter, decreasing reducibility of copper cations by the strong copper-zinc interaction. These interactions result in the incorporation of copper into the crystal structure of zinc oxide and lead to changes in the surrounding of gold in bimetallic (Au-Cu) catalysts compared to materials without zinc. The composition of the catalysts determines their activity and selectivity in methanol oxidation. Bimetallic (Au-Cu) catalysts, irrespective of the nature of the support (MCF vs Zn/MCF), are much more active than monometallic (Au) samples as a result of synergistic interactions between Au and Cu species. The samples containing zinc are highly selective to formaldehyde due to Au-Zn and/or Cu-Zn interaction, which weakens the adsorption of formaldehyde.

The aim of this study is the application of electron magnetic resonance (EMR) spectroscopy to determine the interactions between NaY and HY zeolites and Cu-Mn-Zn spinels loaded onto the zeolite surfaces. The materials were characterized using XRD and IR spectroscopies. Four types of EMR lines were observed for Cu-Mn-Zn/NaY, Cu-Mn-Zn/HY samples. The difference between the EMR spectra recorded at 77 and 293 K has been shown. The spectra recorded at 77 K allowed us to distinguish between the species formed on NaY and HY zeolites. The EMR spectrum of Cu-Mn-Zn/NaY recorded at 77 K showed only one line attributed to antiferromagnetic spinels Cu1.4Mn1.6O4 and ZnMn2O4 or/and Cu0.5Zn0.5Mn2O4. The spinels appeared to be more stable (more strongly attached) on HY zeolite than on NaY one. It was proved that different strength of interactions between the zeolites and Cu-Mn-Zn spinels was caused by differences in the acidity of NaY and HY zeolites.

Commercial silica (Ultrasil - BET surface area 158 m(2)/g) was modified with platinum and/or silver. Before metal loading, the silica was functionalized with one of the following organosilanes, 3-aminopropyltrimethoxysilane (APTMS) and 2-mercaptopropyltrimethoxysilane (MPTMS) or both of them. It was proved that the nature of organosilane (MPTMS or APTMS) used for functionalization of silica before silver and platinum loading, played an important role in the anchoring of Pt and Ag species and affected the kinds of bimetallic particles formed. The creation of alloy-like bimetallic structure depends oil a combination of two parameters, the nature of organosilane and the method of modification by platinum and silver. If the one-pot method of modification was used, the functionalization of silica by MPTMS favoured alloy formation (PtAg/Si-M and PtAg/Si-AM samples). APTMS functionalization promoted alloy formation if the step-by-step modification was applied, independently of the sequence of metals loading. Core-shell structure was formed only if MPTMS functionalization of silica was used and silver species were loaded first (1Ag2Pt/Si-M sample). Bimetallic particles were not formed in two samples, PtAg/Si-A and 1Pt2Ag/Si-M. The presented results have proved that selectivity of bimetallic catalysts in methanol oxidation depends on metals loading and dispersion, whereas their activity is influenced by the interaction between platinum and silver in bimetallic particles. The highest selectivity to methyl formate (84%) for 100% conversion of methanol was reached over PtAg/Si-M at 373 K. (C) 2015 Elsevier B.V. All rights reserved.

The reactive oxygen intermediates generated on surface of amorphous Nb2O5 and Ta2O5 upon interaction with aqueous H2O2 were identified. The role of dehydroxylation of the surface, pH of H2O2 solution, and the presence or absence of oxygen in gas phase were studied in depth by UV-Vis, FTIR, Raman, and EPR techniques. The study revealed high ability of the amorphous Nb2O5 to form peroxo, superoxo, and radical hydroxyl species upon contact with hydrogen peroxide. This process depends on the level of surface hydroxylation which is lower for amorphous Ta2O5 than amorphous Nb2O5. The relationship between the formation of superoxo and peroxo species and pH of the H2O2/H2O solution was proved. Superoxo species interact with the excess of H2O2 towards hydroxyl radicals, which are the most active species in catalytic oxidation. The role of pH was evident in the oxidation of glycerol. NaOH and link of superoxo species to niobium enhance the reaction rate by increase of hydroxyl radicals number. The hydroxyl radicals are also the active species in the formation of hydroxylated cyclohexene and finally cyclohexenediol in cyclohexene oxidation. (C) 2014 Elsevier B.V. All rights reserved.

The goal of this work was to use MCM-22 zeolites for preparation of monometallic (Cu or Au) and bimetallic (Cu and Au) catalysts for oxidation reactions. The focus was on precise determination of the nature of gold and copper species and their activity in the oxidation processes. For that purpose several characterization techniques were applied (XRD, N-2 adsorption/desorption, TEM, SEM, UV-vis, H-2-TPR, Al-27 MAS NMR, FT-IR with the adsorption of pyridine, NO, and CO, ESR spectroscopy). They allowed us to define the following species formed on MCM-22 surface: metallic gold particles (XRD, UV vis), isolated Cu2+ with octahedral coordination (UV-vis, ESR), square planar Cu2+ cations (ESR, IR), Cu+ species (ESR+NO, FTIR+CO, and FTIR+NO), and oligonuclear clusters (UV-vis) as well as CuO-like species (H-2-TPR). The presence of gold on the MCM-22 surface modified further by copper species caused the interaction between two modifiers leading to much easier reduction of CuO-like species and higher mobility of oxygen-promoting oxidative properties. The bimetallic catalyst was highly active in total oxidation of methanol and CO in the temperature range 523-623 K. Cu/Au-MCM-22 zeolite appeared useful for simultaneous removal of CO and methanol (by total oxidation) from gases emitted from automotive devices and during a variety of industrial process operations.

Amorphous and crystalline niobium(V) and tantalum(V) oxides were treated with hydrogen peroxide and studied by XRD, UV–vis, FTIR and ESR techniques to identify changes on their surface upon interaction with hydrogen peroxide. Differences between amorphous and crystalline materials in the interaction with H2O2 depending on the hydroxylation of the surface and the nature of OH groups were evident. The type of radical species formed on hydroxylated amorphous materials treated with H2O2 depended on the nature of metal oxide. It was proved that peroxo radical species formed in the interaction of H2O2 with amorphous Nb2O5 were the active intermediates in the oxidation of glycerol to glycolic acid with hydrogen peroxide. The radicals formed on amorphous Ta2O5 surface treated with hydrogen peroxide were poorly active in the oxidation of glycerol. Detailed study of the above mentioned radicals is in progress and will be a subject of a separate paper.

This study deals with the influence of preparation method of SbVOx binary oxides and modification with niobium on the catalytic properties in the oxidation of methanol. The samples were prepared in the presence of a template by two different procedures with and without the template (Pluronic 123). The template-assisted synthesis leads to higher surface area and pore volume as well as smaller size particles of different shapes than those in the materials synthesised without the template. The rutile SbVO4 phase dominates in all the catalysts studied. The preparation procedure determines the formation of the additives (V2O5 or Sb2O4) and the concentration of oxovanadium species on the catalyst surface. The presence of a small amount of Sb2O4 acting as an electronic promoter in the oxidation of methanol is found when template-assisted synthesis is applied. Such a synthesis involves the formation of reducible oxovanadium species containing nucleophilic oxygen, playing an important role in the oxidation of methanol. Niobium loaded changes the selectivity towards DMM production. It has been found that by using different procedures of synthesis of binary SbVOx oxides and modification with niobium species, it is possible to obtain catalysts useful for the selective production of desired products (FA or MF or DMM) of methanol oxidation.

Silicate, niobosilicate and aluminosilicate mesoporous sieves of SBA-3 type with hexagonal arrangement of pores were synthesised and modified by the wetness impregnation with copper (1wt% loading). The physicochemical properties of the samples were investigated by XRD, N2 adsorption–desorption, XRF, ICP, H2-TPR, ESR, UV–vis, XPS techniques and in acid-basic test reactions—acetonyloacetone cyclisation, 2-propanol reaction as well as by pyridine adsorption combined with FTIR measurements. The oxidative/dehydrogenation catalytic activity of prepared catalysts was examined in the methanol oxidation reaction. Depending on the chemical composition of the SBA-3 support, various copper species were found to be formed and a range of catalytic activities could be achieved. On SBA-3, AlSBA-3 and NbSBA-3 the following copper species were found dominant: bulk CuO, oligonuclear [Cuδ+⋯Oδ−⋯Cuδ+]n clusters and isolated copper cationic species, respectively. Migration of niobium species from the inert part of walls onto the surface after copper loading was observed. The Si/Nb ratio in the support was established to determine the activity and selectivity of Cu modified samples. By the proper combination of the content of Nb and Cu on the surface of SBA-3 materials it can be possible to obtain the catalysts selective to the desired products in oxidation of methanol. The highest production of formaldehyde from methanol was obtained on Cu/NbSBA-3-64 (Si/Nb=57 in bulk and 43 on the surface, Nb/Cu=0.8 on the surface).

Niobosilica material (NbSiOx) prepared by a simple method without the use of organic template was applied as a support for SbVOx phases with high Sb and V contents. In this paper we describe the preparation of VSb/NbSiOx catalysts, their structural/textural characterisation (studied by XRD, N2 adsorption, UV–vis, ESR) and surface catalytic properties (estimated from pyridine adsorption, test reactions: acetonylacetone cyclisation and methanol oxidation). It was found that vanadium–antimony binary oxide phase interacts with acidic hydroxyls on NbSiOx surface. Such interaction leads to the formation of Sb0.95V0.95O4 rutile phase and new OH groups exhibiting basic properties. As the strength of interaction of Sb0.95V0.95O4 phase with niobium species in NbSiOx support increases with increasing calcination temperature, the particle sizes of rutile phase are smaller for higher calcination temperatures. High calcination temperatures cause that more vanadium species are present at the +4 oxidation state, whereas after low-calcination temperatures and at high vanadium content VO species are formed and they are well visible in UV–vis spectra of the catalysts. The presence and role of different active centres on VSb/NbSiOx catalysts are discussed on the basis of results obtained in the oxidation of methanol.

This paper is devoted to the role of niobium, located in crystalline and amorphous catalysts, in catalytic oxidation reactions. Bulk niobium(V) oxides (crystalline and amorphous), NbMCM-41, NbSBA-3, NbSBA-15 and NbY materials were used as catalysts in gas phase oxidation of methanol with oxygen, liquid phase oxidation of glycerol with oxygen and liquid phase oxidation of cyclohexene with hydrogen peroxide. When H2O2 was applied as an oxidation agent the amorphous materials containing niobium species were the most effective catalysts because Nb in such catalysts strongly interacts with H2O2 resulting in the formation of active ONb(V)O2 radicals. It was not the case for crystalline catalysts containing niobium. The results obtained for Nb-containing materials used as supports for copper, gold and binary Sb–V–Ox oxides indicated that niobium species promotes stabilization of the active species loaded. Moreover, it was shown that gold loaded on crystalline niobia increases the catalytic activity in dehydrogenation of methanol and glycerol, which is the first step of their oxidation with oxygen.

In this paper, the influence of the proton forms of beta, Y and ferrierite zeolites and their iron modified counterparts during upgrading of pine wood pyrolysis vapours under nitrogen atmosphere was investigated. A dual-fluidized bed reactor was used where in the first bed pyrolysis of pine wood occurred, and in the second upgrading of the pyrolysis vapours over zeolites was conducted. The temperature for pyrolysis and upgrading was 400 and 450 °C, respectively. De-oxygenation reactions over the proton form and iron modified zeolites increased compared to the non-catalytic pyrolysis. The increased selectivity towards organic compounds through de-oxygenation could be noticed as a higher water yield and CO formation.

SbVOx binary oxides were loaded on MCM-41 matrices of various chemical compositions: silicate (MCM-41), Nb-silicate (NbMCM-41), and Al-silicate (AlMCM-41). Vanadium and antimony were introduced by the post synthesis wetness impregnation carried out step by step (first V next Sb). The materials were characterised by N2 adsorption/desorption, XRD, UV–vis, ESR, H2-TPR, FT-IR combined with pyridine adsorption, and test reaction–hydrosulphurisation of methanol. SbVOx dispersion was much higher when the support contained transition metal (NbMCM-41). Tetrahedrally coordinated vanadium(IV) species were deduced on all prepared samples from UV–vis spectra and were the only registered species on SbV/NbMCM-41 and SbV/AlMCM-41, whereas octahedrally ones were also present on SbV/MCM-41 and SbV/SiO2. In bulk SbVOx octahedral coordination dominated. The chemical composition of mesoporous support determined acidic–basic properties of SbVOx catalysts and influenced the activity and selectivity in methanol hydrosulphurisation. The presence of Lewis acid–base pairs in the SbV/AlMCM-41 and SbV/NbMCM-41 catalysts strongly activated thiol formation in the reaction between methanol and hydrogen sulphide, whereas bulk binary oxides and SbVOx loaded on silicate MCM-41 were less active and exhibited different selectivity.

Three kinds of mesoporous silicas with hexagonal arrangement of mesopores, i.e. MCM-41, SBA-3 and SBA-15, were synthesised and characterised by XRD, N2 adsorption, FTIR, UV–vis and ESR techniques. A choice of these silicas was determined by the use of various siliceous precursors, templates and synthesis conditions. Their catalytic activity was estimated in the oxidation of methanol (gas phase) and cyclohexene (liquid phase) as well as in acid-basic test reactions (propanol–2 decomposition and acetonylacetone (AcAc) cyclisation). It was evidenced that the sources of siliceous, nature of templates and the preparation conditions (pH) play a crucial role in the formation of active species. The E′ and NBOHC (Si–O) and iron and chloride impurities were estimated as active centres for both oxidation reactions.

This paper reviews a series of studies published recently on silicate, aluminosilicate, and niobosilicate micro- and mesoporous molecular sieves modified with transition metals (Cu, Fe, V). These metals were incorporated during the synthesis or in the post-synthesis procedures (impregnation, ion exchange, chemical vapour deposition, immobilisation of organic complex). In case of niobosilicate matrix, the strong interaction between the included metal and niobium species was detected by electron spin resonance spectroscopy (ESR) investigation. The reducibility of metal species in relation to the structure and composition of matrix is discussed. The results of the adsorption of probe molecules (NO, CO, SO2) are shown and discussed.

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