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Layered double hydroxides (LDHs) of various compositions, i.e. Mg–Al, Mg–Mn–Al, are applied as the precursors of metal oxides for the preparation of N-doped carbon materials via chemical vapour deposition (CVD) with acetonitrile (as carbon and nitrogen source) at 600 and 700 °C. The use of Mn-containing LDHs for the preparation of the carbon materials is a novelty. The impact of transition metal species, i.e. MnxOy, in a blend of metal oxides derived from LDHs on the amount of carbon deposit and its composition, morphology, textural and capacitive properties is investigated. Mn-containing species occurring in a mixture of metal oxides enhance the quantity of carbonaceous product compared to those derived from Mg–Al LDHs. Thermally heated Mg–Mn–Al LDHs contain structural defects due to manganese oxides, which promote the formation of carbon deposit, especially higher production of amorphous carbons. The addition of Mn into Mg–Al LDHs matrix leads to carbon particles with increased N-doping and enhanced volume of mesopores. Furthermore, graphitic domains occurring in the carbon materials obtained with Mg–Mn–Al LDHs are thicker than those in the corresponding samples obtained with Mg–Al LDHs as Mn-containing species influence the concentration and location of N-containing groups in graphitic array. The specific capacitance of the carbon materials produced by CVD with the compounds derived from Mg–Al LDHs or Mg–Mn–Al LDHs is comparable (20–25 μF cm−2). The formation of electrical double layer at electrode/electrolyte interface is easier for the carbon materials prepared at 700 °C than for the carbon materials prepared at 600 °C. The maximum charge is stored either in the shallow parts of carbon particles for the former, as they contain bottleneck mesopores, or in the deep parts of carbon particles for the latter, as they contain slit-shaped mesopores. Graphical abstract

Differences in the activity of Pd/WO3 and Pd/MoO3 (Pd loading 0.4–4 wt%) catalysts in competitive hydrogenations of the C C and C O groups in polyfunctional reagents have been studied as a function of two effects: (1) the in situ formation of hydrogen bronzes, HxWO3 and HxMoO3, and (2) the electronic interaction between the supports and the metallic Pd. The cinnamaldehyde (CAL), furfural (FU) and 5-hydroxymethylfurfural (HMF) were hydrogenated under mild reaction conditions. The formation of hydrogen bronzes in Pd/WO3 and physical mixture of Pd/WO3 with supporting WO3 oxide upon exposure to H2 was also studied using the gas flow-through microcalorimetry. In both Pd/MoO3 and Pd/WO3 catalysts, the electronic interactions contributed to the promotion of selectivity toward the C O hydrogenation in CAL and FU, yet in Pd/MoO3 this effect was much more pronounced. On the other hand, apart from increasing the overall reaction rate, the formation of hydrogen bronzes remarkably enhances the C C hydrogenation in CAL, as well as the decarbonylation of FU to furan and hydrogenolysis of C–OH in HMF to 5-methylfurfural. The bronze effects are significantly stronger in HxWO3, compared to HxMoO3, which may be related to higher H-species mobility and weaker H-bonding in the W–O–H (54 kJ/mol H2) than in the Mo–O–H (100 kJ/mol H2). This may also explain very high tendency of Pd/WO3 to furan ring hydrogenation in FU and HMF as well as almost selective (>98%) hydrogenation of furfuryl alcohol to tetrahydrofurfuryl alcohol.

Poly(methylvinylsiloxane) (V3 polymer) obtained by kinetically controlled anionic ring-opening polymerization of 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane was cross-linked with various amounts of 1,3,5,7-tetramethylcyclotetrasiloxane (D4 H) in w/o high internal phase emulsions (HIPEs). PolyHIPEs thus prepared differed in the polymer cross-linking degree, which affected their porous morphology and total porosity. The obtained V3 polymer-based polyHIPEs were applied as matrices for the incorporation of Pd from the Pd(OAc)2 solution in tetrahydrofuran. This process involved the conversion of Si-H groups remaining in the polymer networks and resulted in the formation of crystalline, metallic Pd in the systems. Mean sizes of the generated Pd crystallites were lower in polyHIPEs of higher than in those of lower polymer cross-linking degrees and porosities (∼5 nm vs ∼8 nm, respectively). The Pd-containing polyHIPEs showed activity in catalytic hydrogenation of the triple carbon-carbon bond in phenylacetylene giving the unsaturated product, styrene with a selectivity of ca. 80%. To the best of our knowledge, this is the first work devoted to polysiloxane-based polyHIPEs with dispersed metallic particles.

The paper reports on the solvent and the substituent effects in hydrogenation of aromatic ketones (acetophenone and its derivatives) in the presence of Ru catalyst supported on functionalized gel-type methacrylate-styrene resin under very mild conditions (1 bar H2, 40 °C). The investigated solvents included methanol, 2-propanol, tetrahydrofuran, toluene, isooctane, and cyclohexane, with and without addition of water. The best catalytic activity was obtained in biphasic solvent system consisting of isooctane/water (1:1). In methanol and 2-propanol the beneficial role of water was observed. The effects are discussed in terms of solvent protic/aprotic and polar/apolar properties. The impact of substituents depended on their electron-donating/withdrawing character, and on the position on the aromatic ring of acetophenone. The presence of electron donating substituents tended to increase the reaction rate, and the electron withdrawing group slowed down the process. Steric effect was observed for methylacetophenone isomers with CH3 group at ortho, meta and para positions.

The hydrogenation of furfural (FU) under mild conditions (isopropyl alcohol, 35 °C, 6 bar) was studied over 2 wt% Pd supported on non-treated (Pd/C) and SO3H-modified carbon supports. The catalysts of similar metal particles size (5–6 nm) were prepared by the colloid-based microemulsion method. The products of the Pd-catalyzed FU hydrogenation as well as the acid-sites catalyzed reactions of FU acetalization and etherification were formed. The SO3H groups in the carbon supports influence reactivity of the Pd-sites due to the Pd-electron deficient species formation manifested by the enhanced promotion of furan ring hydrogenation producing tetrahydrofurfuryl alcohol and 2-methyltetrahydrofuran. Furfural diisopropyl acetal was formed even over the Pd/C catalyst of very low acid capacity and acetalization reaction was enhanced over the catalysts with SO3H groups. The furfural diisopropyl acetal content slowly decreased with furfural conversion, assisted by the growth of furfuryl isopropyl ether content. The capacity of acid sites did not strongly affect the process of ether formation evidenced by similar selectivity (10–15%) over all studied catalysts.

Two series of carbon-supported Pd100-XAuX catalysts of different Au contents have been synthesized by the “water-in-oil” microemulsion method (Triton X 114, cyclohexane) using precursor solutions of low (series L) and high concentration (series H). The metal nanoparticles are characterized by XRD, electron microscopy (SEM, HRTEM) and XPS to determine their crystal structure, particles size, composition and morphology. The electrochemical measurements provide data concerning surface properties of the PdAu particles, including surface fraction of Pd and Au and the reactivity towards hydrogen sorption/desorption processes. The metal particles of low bulk Au-content (Au/Pd 1), the particle size increases approaching almost the size of Au particles. An enrichment of Pd toward the surface of all the Pd100-XAuX particles occurs, much pronounced in the samples H series. The activity of catalysts (based on the current densities, and TOF values) in the electrooxidation of formic acid (FA) is correlated with the bulk and surface composition of the Pd100-XAuX particles. The high monodispersity of the metal particle size in the studied catalysts made it possible to observe relation between FA electrooxidation activity and surface composition of the PdAu particles. The catalytically active sites formed at the Au surface fraction ca. 0.1–0.12 (Pd 0.9–0.88) display 1.6-times higher activity (TOF) as compared to pure Pd, while higher surface Au fraction strongly reduces activity. The occurrence of electronic modification of Pd by Au in the Pd100-XAuX particles also results in a reduced hydrogen solubility, accompanied by weaker Pd H bonds, which might influence the poisoning ability by CO formed through electroreduction of CO2, the product of FA oxidation.

Heating PdAu nanoparticles deposited on silica in hydrogen results in palladium silicide(s) formation. The degree of palladium extraction by silicon species (ex-silica) is conversely correlated with the gold content in the PdAu alloys. In addition, the phase changes are less extensive than analogous transformations in a previously investigated PdCu-silica composite. Very high temperatures (>550 °C) are required to initiate the transformation of PdAu-SiO2 into respective bulk metal silicide(s), whereas for the PdCu-SiO2 (and Pd-SiO2) similar changes have already been observed at ≤450 °C. Based on existing literature data, it is considered that the reason for this difference is a relative availability of palladium-rich material at the Pd-IB alloy-silica phase boundary. In the case of PdAu, the segregation of gold at the surface is very pronounced, making this alloy more resistant against Pd extraction required for the silicide formation.

Molybdenum trioxide-supported palladium catalyst Pd/MoO3(SPD) is prepared by the sonophotodeposition procedure (SPD). This method combining sonication with ultraviolet irradiation is used at room temperature and atmospheric pressure and does not require the use of chemical reducing agent. For comparison, the Pd/MoO3 catalysts are also prepared by the ultrasound irradiation and traditional impregnation - H2 reduction methods. The Pd/MoO3 catalysts are characterized by X-ray diffraction (XRD), electron microscopy (SEM, TEM, HRTEM), energy dispersive (EDS, STEM) analysis and X-ray photoelectron spectroscopy (XPS). The SPD treatment improves the platelets-like morphology of the MoO3 oxide grains making more difficult formation of hydrogen bronzes HXMoO3 (x > 0.9) studied by microcalorimetric method. The “in situ” reduction of precursor ions during the SPD treatment generates much better dispersed Pd-nanoclusters than other preparation methods. It results in much higher activity of Pd/MoO3(SPD) catalyst for the cinnamaldehyde hydrogenation than its MoO3-supported counterparts and Pd/SiO2, a reference catalyst.

Pd-based bimetallic catalysts PdM-0.1/C where M = Au, Pt, Ru, Ir with total metal loading of 2 wt % and a Pd: M molar ratio of 10: 1 were synthesized by the “water-in-oil” microemulsion method. Metal particles are prepared by directly adding the reducing agent (NaBH 4 ) as a powder to the metal salts − containing microemulsion (water/Triton X-114/cyclohexane). The monometallic Pd/C, Pt/C, Au/C, Ru/C and Ir/C catalysts were prepared with the same procedure. Physicochemical (XRD, XPS, SEM, HRTEM, EDS) and electrochemical (cyclic voltammetry) methods were applied to characterize the structure, morphology and surface properties of the synthesized catalysts. The microscopic results show that the mono- and bimetallic particles are monodisperse and well distributed on the carbon support. It is suggested that nucleation processes are mainly responsible for the metal particle formation if one uses the single-microemulsion procedure. The average size of the monometallic particles increased from Ir to Au. The size of all bimetallic PdM particles is smaller than that of Pd and they differ in the extent of surface segregation. The segregation is most pronounced in the PdAu and PdPt systems, resulting in a surface enrichment with Pd and Pt, respectively, whereas the PdRu and PdIr systems, in contrast, exhibit practically homogeneous alloy microstructure. It has been shown that these microstucture-induced surface effects are related to the catalytic properties of the PdM-0.1/C samples in the cinnamaldehyde hydrogenation reaction.

Two series of nanostructured carbon replicas were synthesized through a hard-templating method using ordered SBA-15 or disordered mesoporous spherical silica gel as the templates and furfuryl alcohol or sucrose as the carbon source. They were explored to synthesize the Pd catalysts (ca. 1.5 wt% Pd loading) by the colloid-based microemulsion procedure which allowed preparing the catalysts of monodispersed Pd particles of similar size (4–5 nm). The palladium phase in the catalysts (e.g. the Pd particles distribution and extent of agglomeration) varied depending on the textural and surface characteristics of the carbon replicas. In the furfural hydrogenation studied as a probe reaction (2-propanol, 35 °C, 6 bar H2), furfuryl alcohol and tetrahydrofurfuryl alcohol were the major products formed. The catalytic reactivity has been related to the properties of the Pd phase including the surface Pd concentration and the extent of the Pd particles aggregation accompanied by the nearest palladium environment expressed by the surface O/Pd atomic ratio. At high O/Pd ratio the reaction slowed down because of a facilitated furfuryl alcohol adsorption resulting most probably in a blockage of the active sites. The SiO2 sucrose system provided the catalyst which was characterized by relatively low O/Pd ratio with well-dispersed Pd particles and the highest and stable activity for the furfural hydrogenation. The SBA-series catalysts, with lower O/Pd and more aggregated Pd particles, exhibited lower activity but somewhat higher tendency to the tetrahydrofurfuryl alcohol formation.

A microcalorimetric method has been combined with a potentiostatic method to measure simultaneously the rate of heat evolution and the electrical current in a powdered sample of palladium during thermokinetic oscillations accompanying the sorption of deuterium in the metal. Deterministic chaos has been confirmed in the temporal variations in current (of ca. 1-4 mA) on the onset of both the sorption and the desorption of deuterium from Pd. It has been found that the first derivative of the current in time, dI/dt, turns out to be correlated precisely with the periodicity of thermokinetic oscillations. The dI/dt curves consist of regularly timed outbursts of aperiodic, high frequency (HF) fluctuations, interlinked by calm periods. The calm periods correlate with the descending slopes of thermokinetic oscillations (i.e., with decrease in the rate of heat evolution) and their lengths depend on the frequency of thermokinetic oscillations. In turn, the outbursts of aperiodic HF fluctuations in the dI/dt derivatives correlate with the ascending slopes of thermokinetic oscillations (i.e., with increasing rate of heat production), but their length is practically constant, irrespective of the thermokinetic frequency. We propose a periodic mechanism of sorption including a collective action of adsorbed deuterium taking place on the Pd surface. The periodicity of this mechanism arises from the temporal separation of its two sub-processes. The sub-process (1) involves only the adsorption of molecular D2 on the Pd surface and proceeds with little heat evolution until a critical coverage of D2 is achieved. The sub-process (2) initiates the dissociation of the adsorbed D2 and the penetration of the dissociated atomic D species into the Pd lattice. It is the more energetic of the two, but it only begins after a threshold coverage of D2 on the Pd surface has been achieved. We suggest that these sub-processes occurring alternatingly may provide a kernel for the oscillatory behavior observed in Pd/H(D) systems.

Studies concentrated on the development of carbon supported PdxPty/C electrocatalysts for the oxygen reduction reaction (ORR). The application of the reverse ‘water-in-oil’ microemulsion method allowed to obtain a number of electrocatalysts with metal nanoparticles of ca. 5–6 nm in size. Catalysts with the constant metal loading of 10 wt% and various Pd:Pt atomic ratios were investigated. The textural features of the PdPt/C catalysts (surface area, morphology) as well as the PdPt phase (metal particle size, bulk composition) were characterized by a number of techniques. A particular attention was paid to the characterization of the surface properties of the PdPt particles using cyclic voltammetry technique. For all Pt contents (5 to 70 at%) a segregation of metal components (Pt, Pd) occurred leading to the Pt enrichment in the top layers. The observed Pt enrichment manifested especially strongly for PdPt catalysts with bulk Pt content below 20 at%. The surface fraction of Pt as high as 0.8 to 0.9 was attained regardless of nominal Pt content, starting from 30 at%. Among the catalysts, those with Pt content of 50 and 70 at% exhibited the highest activity towards ORR in terms of positively shifted half-wave potential, even surpassing that of Pt/C. Moreover, the obtained specific activity and turnover frequency values also suggested similar activities of catalysts with Pt content of 50 and 70 at%. A negligible formation of hydrogen peroxide on these two catalysts, indicated almost exclusively a desired four-electron process leading to water formation. The observed effect of Pt content on ORR activity is discussed in terms of surface properties of the PdPt nanoparticles.

The thermal effects and activity of silica and alumina supported bimetallic Pd-Au catalysts (of various Pd/Au ratio) in the exothermic H 2 and O 2 recombination reaction have been investigated in view of their potential use in the industrial passive autocatalytic recombiners (PAR). The catalysts were prepared by the colloid-based reverse “water-in-oil” microemulsion method which provided metal particles of size in a very narrow range (4–7 nm). In both SiO 2 and Al 2 O 3 − series catalysts the Pd-Au particles aggregated to some extent, especially strongly in alumina-series samples. The H 2 + O 2 reaction has been monitored using Microscal gas-flow through microcalorimeter at temperature of 22 °C and atmospheric pressure. The observed pattern of changes in both the heat evolution and the conversion of hydrogen seem to reflect the effect of water and/or other oxygen-containing surface species (like OH) on the activity/deactivation of catalysts. The nature of support and the composition of metal particles (Pd/Au ratio) played a role. Deactivation of alumina supported catalysts was stronger than silica supported counterparts. Among all studied catalysts, the best behavior was offered by low Au content-containing Pd-Au-0.1/SiO 2 (Pd 90 Au 10 ) catalyst. Its almost stable activity during the catalytic run may be attributed to relatively weak interactions with water molecules and/or other oxygen-containing species (like OH), intermediates formed in the hydrogen oxidation. It may be supposed that electronic modification of palladium sites by gold assisted by the surface composition of Pd-Au particles reflecting in “surface arrangement of Pd and Au-atoms” are decisive. This experimental observation seems to correlated with the DFT calculation indicating that besides the number of Au atoms, their location with respect to the Pd, e.g “surface arrangement of Au” is more important for the energy/strength of interaction with water molecules.

Liquid phase hydrogenation of cinnamaldehyde (CAL) is studied at mild conditions (50 °C, atmospheric pressure) on molybdena-supported Pd catalysts (0.5–4 wt% Pd) to elucidate an effect of hydrogen bronzes in controlling the selectivity to C C/C O hydrogenation. The Pd/SiO 2 catalyst is used as a reference, because SiO 2 is known to be an “inert” support. Additional information on the interaction of Pd/MoO 3 catalysts with hydrogen is provided by the microcalorimetric measurements. The impregnation of MoO 3 with palladium acetate followed by hydrogen reduction (250 °C) produces Pd/MoO 3 catalysts containing Pd particles ca. 8–10 nm, regardless of the metal loading. The XRD, XPS, SEM, TEM, and HRTEM techniques have been employed to characterize the catalysts. The metal particles are nearly monodispersed and well distributed at low Pd-loading, 0.5%Pd/MoO 3 . As the content of Pd increases the agglomeration of Pd particles occurs. All the Pd/MoO 3 catalysts display higher selectivity to C O hydrogenation compared to Pd/SiO 2 . The content of Pd has an impact on activity and selectivity. The activity normalized to the Pd mass decreases with growing Pd-loading in Pd/MoO 3 . The C C group of CAL was preferentially hydrogenated compared to the carbonyl (C O) group at low (0.5%Pd) and high (4%Pd) Pd content pointing out to an effect of optimum Pd-loading in the selectivity of CAL hydrogenation. The activity/selectivity behavior of Pd/MoO 3 catalysts is related to an effect of hydrogen bronzes existing during the catalytic tests. They could provide additional active sites efficient for the activation of CAL resulting in promotion of C C hydrogenation. Hydrogen species in the bronzes could also have a beneficial effect on palladium crystallites formation upon reduction of palladium ions. High mobility of hydrogen species in the bronzes structure assisted by easy migration of palladium ions facilitated by MoO 3 layered morphology and structural changes during the reduction could promote the Pd crystallites of tetrahedral shape.

Supported Pd/Ir bimetallic catalysts were synthesized by the “water-in-oil” microemulsion method at different precursor concentrations and characterized by XRD, XPS, SEM, TEM, and cyclic voltammetry. Depending on the preparation conditions, formation of bimetallic catalysts with different metal segregation and surface composition can be easily obtained, thus tuning the bimetallic structure of catalysts as well as their relative catalytic properties. Bimetallic Pd/Ir systems were efficiently tested in the hydrogenation of cinnamaldehyde showing a better performance than analogous monometallic catalysts.

The influence of the oxidized carbon moieties in the nanostructured carbon-supported Pd catalysts was studied for the furfural hydrogenation (2-propanol, 35 °C, 6 bar H2). The mesoporous carbon replicas synthesized using two systems: SBA-15-furfuryl alcohol or nanostructured SiO2-sucrose and oxidized with nitric acid or hydrogen peroxide were used as the supports. The catalysts (1.5–2 wt% Pd) of similar Pd particles size (ca. 4 nm) were synthesized by the “water-in-oil” microemulsion procedure. Although the carbon-supported Pd, Pt catalysts have been tested for the furfural hydrogenation, the effect of oxygenated carbon groups have not been yet investigated. Present results showed that the surface O/Pd atomic ratio influenced the rate and product distribution. Over initial carbon-supported Pd, the rate was high and apart from furfuryl alcohol and tetrahydrofurfuryl alcohol certain amount of “other” products was also observed. The oxidized carbon-supported catalysts were less active but more selective towards furan ring hydrogenation with almost completely inhibited “other” products formation reactions. The growing content of surface oxidized groups, in particular the carboxylic ones, corresponded well to the order of decreased activity. This effect has been related to a gradually reduced access of the regents to the Pd-surface sites because of the growing tendency to the hydrogen bonds formation with the participation of the oxygenated carbon groups – furfuryl alcohol – 2-propanol alcohol solvent.

Activity and deactivation of alkali (Li, Cs) doped 2%Pd/Al 2 O 3 catalyst in the exothermic H 2 and O 2 reaction have been studied in view of potential application in the passive autocatalytic recombiners (PAR), the safety devices applied in the nuclear plant containments to lower the explosion risk associated with hydrogen release. The catalysts have been prepared with impregnation method and characterized by BET, XPS, TEM and STEM techniques. The role of humidity in the H 2 /O 2 recombination reaction has been studied in a flow laboratory reactor using water saturated reaction mixture (0.5 vol% H 2 ). The time-on-stream behavior of catalyst in contact with reaction mixture of high H 2 concentration (7.2 vol%) has been studied using Microscal gas-flow through microcalorimeter. The thermal effects accompanying the H 2 conversion during slow deactivation of catalysts have been monitored. The pattern of changes in both the heat evolution and the H 2 conversion in the Pd-catalyzed H 2 /O 2 recombination reaction seem to reflect the inhibiting effect of humidity present in the reaction mixture and water molecules formed in the reaction. The presence of both Li and Cs enhanced deactivation of Pd/Al 2 O 3 catalyst and Cs-dopant displayed more pronounced effect. On the other hand, the alkali dopants do not essentially affect the amount of heat evolved during the recombination process ranging from 187 to 220 kJ/mol H 2 , e.g. being lower than the heat of water formation (246 kJ/mol). The detrimental effect of Li,Cs dopant has been attributed to higher affinity to water, promoting retention of water molecules/films on the catalyst surface and blockage of active sites due to enhanced adsorption of surface species, like H 2 O/OH.

Two series of carbon-supported Pd–Au catalysts were prepared by the reverse “water-in-oil, W/O” method, characterized by various techniques and investigated in the reaction of tetrachloromethane with hydrogen at 423 K. The synthesized nanoparticles were reasonably monodispersed having an average diameter of 4–6 nm (Pd/C and Pd–Au/C) and 9 nm (Au/C). Monometallic palladium catalysts quickly deactivated during the hydrodehalogenation of CCl4. Palladium–gold catalysts with molar ratio Pd:Au = 90:10 and 85:15 were stable and much more active than the monometallic palladium and Au-richer Pd–Au catalysts. The selectivity toward chlorine-free hydrocarbons (especially for C2+ hydrocarbons) was increased upon introducing small amounts of gold to palladium. Simultaneously, for the most active Pd–Au catalysts, the selectivity for undesired dimers C2HxCly, which are considered as coke precursors, was much lower than for monometallic Pd catalysts. Reasons for synergistic effects are discussed. During CCl4 hydrodechlorination the Pd/C and Pd–Au/C catalysts were subjected to bulk carbiding.

The thermal effects and activity of silica and alumina supported monometallic Pd, Pt and bimetallic Pd-Pt catalysts (of various Pd/Pt ratio) in the exothermic H 2 and O 2 recombination reaction have been investigated in view of their potential use in the industrial passive autocatalytic recombiners (PAR). The pattern of changes in both the heat evolution and the conversion of hydrogen observed in the H 2 /O 2 reaction seem to reflect the effect of water formation on the activity/deactivation of the studied catalysts. The catalysts have been prepared using the colloid-based reverse “water-in-oil” microemulsion method and characterized by XRD, XPS, SEM, EDS techniques. The recombination reaction of hydrogen and oxygen has been monitored using Microscal gas-flow through microcalorimeter as well as a laboratory flow microreactor. The humidity present in the reaction mixture and the water molecules formed in the recombination reaction both inhibited the activity of the tested catalysts. The nature of support and the type of metal played a role in such water-poisoning effect. Deactivation of alumina supported catalysts was stronger than silica supported counterparts and Pt was more prone to the water inhibition compared to Pd. The most promising catalysts exhibiting the lowest amount of evolved heat accompanied by high and stable activity are silica supported Pd-rich bimetallic Pd-Pt particles whereas alumina wash-coat-Pt is the catalyst of chose in the PAR reactors. The observed activity/water-poisoning relations found confirmation in the DFT calculations concerning the interactions between water molecules and mono-(Pd, Pt) as well as bi (Pd-Pt) metallic clusters as a function of cluster size and Pd/Pt compositions.

The hybrid catalysts derived from 12-molybdophosphoric acid (H 3 PMo 12 O 40 denoted as HPMo) and montmorillonite (Na, H-exchanged montmorillonites derived from Polish bentonite denoted as Na-Mt, H-Mt and commercially available K10 montmorillonite denoted as Mt-K10) were prepared by conventional and modified impregnation routes. Conventional procedure based on the incipient wetness impregnation method involved stirring of the aqueous dispersion of HPMo and montmorillonite, followed by drying at elevated temperature. Modified preparation method employed ultrasonication as a means of the dispersion homogenization, followed by freeze-drying. Such prepared catalysts were characterized by means of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen sorption, electron spin resonance (ESR), Fourier transform infrared (FT-IR), ultraviolet–visible (UV–vis) and 31 P solid-state magic-angle-spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. Acidic/redox properties of HPMo/montmorillonite systems were evaluated by catalytic conversion of ethanol and pyridine sorption. The hybrid catalysts consist of two catalytically active components. In contrast to montmorillonite, especially acid-treated montmorillonite, which has mainly acidic sites, HPMo species in the final hybrid catalysts may offer both acidic and redox catalytic functions. Spreading HPMo on the surface of montmorillonites results in enhancement in the redox reactivity as a consequence of exposing the redox sites (Mo-containing species). The use of Na-Mt leads to the catalysts with dominating redox function as the acidic sites (coming from HPMo) may be obscured by replacement of protons by sodium ions coming from Na-Mt. In addition, the catalyst prepared by modified impregnation shows higher redox reactivity than that prepared by conventional impregnation.

Polyaniline doped with methanosulfonic (MSA) or camphorosulfonic (CSA) acid was deposited on silica and carbon support during polymerization of appropriate aniline salt carried out in the presence of immersed carriers. The activity of obtained catalysts was examined in the transesterification of triglycerides (triacetin and castor oil) and esterification of ricinoleic acid with methanol. The textural (specific surface area, porosity, pore diameter), morphological and acid (concentration and strength of acid centers) properties of catalysts were studied by number of techniques. The activity of acid sites in the silica and carbon supported MSA- and CSA-polyaniline catalysts was observed to be distinctly higher than activity of their counterparts with alkyl-free sulfuric acid-polyaniline coatings. A role of the type of support (carbon, silica), textural characteristics (porous structure), morphology of the polymer coating and the type of organo-sulfonic acid was studied. An enhancement in catalytic performance (higher activity, lower active sites blockage) due to organic group in close proximity to the SO3H sites varied depending on the type of reaction, being the highest in reactions with bulky reactants such as triglycerides from castor oil and ricinoleic acid. Among all catalysts, silica coated with methanosulfonic acid-polyaniline (SiO2-pani-MSA) exhibits the best catalytic performance in all tested reactions.

Liquid phase hydrogenation of cinnamaldehyde was studied on carbon supported (Vulcan XC72) – PdAu catalysts with Au/Pd atomic ratio varying from 0.1 up to 2.1. Colloid-based method, namely the reverse “water-in-oil” microemulsion technique was used to prepare the catalysts. Accordingly, pre-formed metal nanoparticles of controlled size with a narrow size distribution were deposited on carbon support. The BET, XRD, XPS, SEM, TEM, and HRTEM techniques were employed to characterize PdAu/C catalysts and their monometallic 2%Pd/C and 2%Au/C counterparts. The metal particles were spherically shaped, nearly monodispersed and well distributed throughout the carbon support. The particles of low Au-content (Au/Pd C group of cinnamaldehyde was preferentially hydrogenated compared to the carbonyl (C O) group on the Pd/C catalyst. At Au/Pd O hydrogenation. The effect of Au manifested distinctly on Au-rich catalysts (Au/Pd > 1) giving strongly reduced activity to saturated aldehyde formation accompanied by the selectivity preference to the carbonyl group reduction. These activity/selectivity effects induced by the gold were discussed to be related with the microstructure of metal particles determining their surface composition. Moreover, both geometric and electronic modifications of Pd-sites due to the Pd–Au interactions should be also taken into account. These interactions may also provide new active sites which are able to activate the C O bond of CAL in the PdAu alloy particles-containing catalysts.

Background The catalytic performance of supported heteropolyacids in various liquid–solid and gas–solid heterogeneous reactions may be affected by the choice of support and/or the method of heteropolyacid deposition.

The aim of present work was to evaluate a role of the secondary structures of the K2HPW12O40 and K2.5H0.5PW12O40 salts in their catalytic activity for vapour-phase dehydration of ethanol. Particular attention was directed to the role of H3PW12O40 (HPW) existing as a self-organized surface layer, which covers partially or entirely the K3PW12O40 core. The results showed that both salts are much more active than bulk HPW. It turned out that the dehydrated protons present in the studied salts transform ethanol to ethylene much easier than the hydrated protons existing in the HPW. The ammonia sorption measurements demonstrated that the [N2H7]+ adducts were formed easier on the surface of the K2HPW12O40 salt whereas the formation of the N H 4 + cations dominated in the bulk HPW. The structures of potassium tungstophosphates after catalytic reaction were investigated by the FT-IR, XRD and N2-sorption methods. A self-organized surface layer of HPW in the K2HPW12O40 salt was unstable because it transformed to the crystalline HPW, due to the reaction temperature as well as to the presence of ethanol or water (dehydration product). However, the structure of the K2HPW12O40 salt can be partially restored after ageing for a month at ambient temperature in air with the relative humidity of 25%. In contrast, the secondary structure of the K2.5H0.5PW12O40 salt remained practically unchanged after catalytic reaction. It makes this salt a very promising catalyst for the ethanol dehydration, with the conversion of 99.4% and the selectivity to ethylene attaining ca. 100% at 448 K.

In the present work catalytic reactivity of polyaniline protonated with organo-sulfonic acids, namely methanosulfonic (MSA-Pani), camphorosulfonic (CSA-Pani) and lignosulfonic (LG-Pani) acids was evaluated for the transesterification of triglycerides (triacetin, castor oil) and esterification of fatty acid (ricinoleic) with methanol. Their reactivity was also compared with previously studied alkyl-free polyaniline-sulfate (S-Pani) catalyst. The textural and acid properties of the catalysts before and after catalytic tests were characterized by BET, FT-IR, XRD, SEM, thermogravimetric and ammonia sorption techniques. It was observed that acid characteristics, namely concentration and the strength of acid sites as well as chemical properties of the surface e.g. the type of organo-sulfonic acid played an important role in catalytic performance of studied samples. In all tested reactions, the MSA- and CSA-doped polyanilines exhibited the highest initial activity referred to the acid site capacity. However, too weak acid sites in these catalysts resulted in their partial blockage during methanolysis of triglycerides. This was not observed in the esterification reaction. Among all studied samples, the LG-Pani (commercial reagent) and MSA-Pani catalysts seem to be the most promising owing to their high activity and good stability in reaction mixture, in particular during methanolysis of triglycerides. In contrast to the MSA-Pani catalyst (thermally stable up to 260 °C), lower stability of LG-Pani catalyst (up to ca. 120 °C) may limit its application.

Present studies concentrated on the preparation, characterization, and electroactivity of palladium–polypyrrole (Pd/PPY) catalysts for oxygen reduction reaction. In particular, the effect of Nafion ionomer on their electroactivity was evaluated. In all catalysts prepared by “water-in-oil” microemulsion method, the Pd nanoparticles of ca. 7 nm in size appeared regardless of the Pd content (ranging from 2 to 20 wt.%). For comparison, carbon black-supported (Vulcan XC-72) catalyst (20 wt.% Pd) was also synthesized. Coating of the Pd/PPY samples with Nafion ionomer reduced their surface area and porosity. Chemical interaction due to Nafion acid functionalities affected the N-state of pyrrole as well as electron state of Pd in the Pd/PPY catalysts. As a result, the contribution of more oxidized palladium (Pdδ+) increased. These interactions played an essential role in the electroactivity of Pd/PPY for oxygen reduction reaction. The increased amount of Nafion relative to that of PPY reduced limiting current density whereas the half-wave potential shifted to a more positive value and the fraction of hydrogen peroxide remarkably decreased.

Application of a catalyst preparation method known as ‘water-in-oil’ microemulsion allowed to obtain a series of palladium/polypyrrole (Pd/PPY) electrocatalysts with various Pd contents (2–20 wt%) and Pd particle size within a narrow and similar range of 6–8 nm. The textural features of the samples (surface area, porosity) as well as the palladium phase (metal particle size, shape) were characterized by a number of techniques. Electrocatalytic activity of the prepared materials towards oxygen reduction reaction (ORR) was studied in 0.5 M H2SO4 using rotating ring disc electrode voltammetry (RRDE) and cyclic voltammetry techniques. All prepared Pd/PPY samples exhibited electrocatalytic activity towards ORR. At a constant palladium loading on the electrode, the polymer to Pd weight ratio was found to play a decisive role in the electrocatalytic performance of the samples. Their catalytic performance in terms of the increased reduction current and positively shifted half-wave potential (RRDE measurements) was improved when Pd content in polymer was grown from 2 to 12 wt% Pd. At the optimum Pd content, 10–12 wt%, the analysis of the RRDE data confirmed that molecular oxygen underwent mainly a desired four-electron reduction. By further increasing the Pd content and thus decreasing the PPY to Pd ratio, the selectivity to water continuously decreased while the fraction of undesired H2O2 product significantly increased. Therefore, a role of PPY to Pd weight ratio in the electrocatalytic performance of the investigated catalysts is discussed here.

The samples of Cs2HPW12O40 salt were precipitated with CsCl, CsBr or CsI reagent as well as with commonly used Cs2CO3. The use of cesium halides resulted in the Cs2HPW12O40 samples of mesoporous structure composed of relatively loosely aggregated primary particles. It was observed that the type of halogen ion influenced textural properties of the Cs2HPW12O40 samples. As the atomic size of halogen ion increased (from Cl to I), the specific surface area and microporosity decreased. The so-obtained samples exhibited textural and morphological features similar to those of Cs2.5H0.5PW12O40 salt. In the transformation of m-xylene, the pore-size sensitive reaction, the catalytic activity of the Cs2HPW12O40 samples prepared with CsBr and CsI reagents was about two-fold higher than that of Cs2.5H0.5PW12O40 salt. All these samples exhibited similar strength of acid sites. Therefore, high catalytic activity of the samples prepared with CsBr and CsI could be ascribed to their open pore structure, which allowed the accessibility of almost all active sites for m-xylene molecules.

Various mesoporous silica materials (FSM-16, HMS, SBA-15) aluminated via direct procedure or by a post-synthesis treatment, differing in the manner of Al distribution between the external surface and the mesoporous network, were employed for the immobilization of [(η 5 -MeC 5 H 4 )Ru(η 3 -DPVP)(η 1 -DPVP)] + (DPVP = PPh 2 CHCH 2 ) complex. The catalysts of similar loading (ca. 5 wt.%) of Ru-species were prepared by means of cation exchange. The samples were characterized with XRD, XPS, MAS NMR, N 2 adsorption/desorption techniques and quantum chemical calculations, and tested in the liquid phase hydrogenation of phenylacetylene. Two binding modes of Ru species were identified: (i) at the surface free of spatial constraints, with the participation of the hemilabile ligand in the electrostatic attraction and (ii) in the limited space of narrow mesopores, via peripheral areas of Ru coordination sphere, leaving hemilabile phosphine exposed to the reaction medium. It has been demonstrated that the latter location is a prerequisite of high catalytic activity of the supported system, while the former destroys the catalytic action.

The palladium particles pre-formed by “water-in-oil” microemulsion method were deposited onto carbon, silica and cellulose supports which differed in hydrophobic and textural properties. Microemulsions with anionic bis(2-ethylhexyl)sulfosuccinate (AOT) and non-ionic polyoxyethylene(7-8)octylphenyl ether (Triton-X 114) surfactants were used. Palladium particles of size with narrow range but various average sizes (ca. 8–9 and ca. 4 nm) were obtained using hydrazine hydrate or NaH 2 PO 2 as reducing agents. The results obtained by a number of techniques (XPS, XRD, SEM, TEM) showed that porosity of support and polarity of its surface determined the migration of Pd particles inside the pore structure as well as their aggregation in the final catalysts. Increased polarity of silica surface due to pre-treatment with water produced the most extensively aggregated particles. Pre-treatment of silica with non-polar cyclohexane, the solvent of bulk microemulsion, exhibited a very advantageous role because both processes migration and aggregation of primary Pd particles were almost completely inhibited. In the obtained 1%Pd/SiO 2 catalyst no aggregated particles appeared and it exhibited very high activity in liquid phase hydrogenation of styrene.

Present research concentrates on the role of alkali modifiers (Li, Na, K, Cs) in activity of 2%Pd/Al2O3 catalyst for 2-ethyl-9,10-anthraquinone (eAQ) hydrogenation. The catalysts with various content of alkali modifier (Me/Pd molar ratio ranges from 0.5 up to 4, Me-alkali metal) were prepared by impregnation of pre-reduced 2%Pd/Al2O3 catalyst with appropriate alkali metal carbonates. The XPS, EDS and TEM measurements show that alkali promoters are introduced into alumina matrix. The microcalorimertic experiments of CO adsorption prove the interaction of CO with catalysts leading to stronger bonding of carbon monoxide by alkali doped catalysts. The presence of alkali promoters in Pd/Al2O3 catalyst plays an essential role in the whole eAQ hydrogenation process. The nature of alkali promoter and its content (Me/Pd atomic ratio) in catalyst are of importance. As the alkalinity of promoter increases going from Li to Cs all the effects caused by their presence become stronger. In the presence of alkali doped catalysts the content of 2-ethyloxoanthrone (OXO, isomer of 2-ethyl-9,10-anthrahydroquinone) formed is higher than that on un-doped 2%Pd/Al2O3. On the other hand, reactions in the “deep hydrogenation” stage comprising the formation of 2-ethyl-5,6,7,8-tetrahydro-9,10-anthraquinone (H4eAQ) and the transformation of OXO to 2-ethylanthrone and other degradation products are remarkably inhibited. In particular, the formation of 2-ethylanthrone via hydrogenolysis of OXO isomer is strongly suppressed. The Cs-doped catalyst exhibits the highest activity to OXO among all the catalysts tested whereas the ability of Cs-doped catalysts to the formation of anthrone is most effectively inhibited. The role of alkali modifiers is considered to be associated with stronger interactions between the catalyst and quinone reagents, and in particular OXO isomer. Moreover, in the reagent adsorption the centres of support nearby the palladium particles may also participate by affecting the mode of reagents adsorption.

Present studies concentrated on a comparison of catalytic performance of number of solid acid catalysts, namely Amberlyst-15, Nafion-SAC-13, polyaniline-sulfate, silver and cesium salts of H 3 PW 12 O 40 in transesterifiaction of triglycerides with methanol. Reaction was studied for triacetin, the short triglyceride and for castor oil consisting of vegetable fatty acid esters under mild reaction conditions (atmospheric pressure, 50 °C). The catalysts were characterized by measuring textural (specific surface area, porosity, pore diameter) and acid (concentration and the strength of acid centers) properties. The affinity of catalyst to highly hydrophobic triglyceride reactant relative to that toward rather hydrophilic glycerol was also evaluated from the measurements of contact angles for droplets of triacetin, castor oil and glycerol on the surface of pressed tablet of catalyst. This affinity of catalysts was also evaluated from the drop of catalyst activity induced by glycerol added to the reaction mixture or by pre-treatment of catalyst with triacetin. Cs 2 HPW 12 O 40 salt was the most active catalyst, but it deactivated in the transesterification. The highest strength of acid sites and high affinity to glycerol was determined for this Cs salt. Thus, affinity of studied catalysts toward glycerol and the strength of acid sites seem to be decisive factors for their activity and in particular for deactivation due to polar reagents adsorption. Greater affinity toward glycerol and higher strength of acid sites, deactivation of catalysts would be easier.

Liquid phase hydrogenation of acetophenone (ACT) is studied over ruthenium catalysts (1-4 wt% Ru) supported on gel-type methacrylate-styrene resin (FCN) functionalized with C=O, –NH, and –NH2 groups. Microscopic studies (SEM, STEM) show that the nature of Ru particles depends on the level of Ru doping. At low Ru content (1–2 wt%) ruthenium nano-clusters are formed, while at 4 wt% Ru, metal crystallites of few nanometers in size are observed. Catalytic reactions are performed at mild conditions (atmospheric pressure of hydrogen, 40 °C) in biphasic isooctane-water (IO/H2O) solvent system, and, for comparison, in a single component solvent (isooctane or ethanol). The use of biphasic IO/H2O solvent system results in a dramatic improvement of selectivity. The hydrogenation of C=O in acetophenone dominates over the hydrogenation of aromatic ring, yielding 1-phenylethanol with ca. 80% selectivity. Ru/FCN catalysts exhibit higher selectivity than the reference Ru/Al2O3. This is tentatively assigned to the steric effects induced by the polymer network on migrating reactant molecules. Advantageous influence of biphasic IO/H2O solvent system has been attributed to the solvation of phenyl ring of acetophenone by non-polar isooctane, which facilitates the interaction with the catalyst surface via carbonyl group and leads to the preferential reduction to 1-phnenylethanol. Liquid phase hydrogenation of acetophenone was studied over ruthenium catalysts (1–4 wt% Ru) supported on diamine group functionalized gel-type polymer (FCN).

Methanolysis of natural oil, i.e. castor oil and triacetin, a model compound for the transesterification of triglycerides in biodiesel production was studied under atmospheric pressure at temperature of 50–60 °C. As-received zinc hydroxy nitrate Zn5(OH)8(NO3)2×2H2O (Zn-5) and samples obtained by thermal treatment of Zn-5 for 2 h in the temperature range of 105–300 °C were used as the catalysts. The catalysts were characterized by thermogravimetric (TG) analysis, X-ray powder diffraction (XRD), infrared spectroscopy (FTIR), nitrogen sorption (BET) and scanning electron microscopy (SEM). The effect of thermal treatment of Zn-5 salt on the activity and reusability in methanolysis of triglycerides was studied. During thermal treatment of as-received Zn-5 salt a gradual decomposition via various hydroxy nitrates intermediates such as Zn5(OH)8(NO3)2 and Zn3(OH)4(NO3)2 to ZnO occurred. This was accompanied by significant morphological and textural changes. Plate-like particles of Zn-5 salt reorganized into spherically shaped particles of ZnO. Moreover, decrease in specific surface area and porosity occurred. In methanolysis of both triglycerides, the activity of Zn-catalysts gradually decreased as the temperature of thermal treatment increased and the activity of ZnO, a final product of thermal decomposition was very low. The most active was as-received Zn-5 salt and its morphological/chemical properties did not change during methanolysis reaction performed at temperature of 50–60 °C. Moreover, the activity of original Zn-5 salt was fully restored after methanol/THF washing of spent catalysts. The activity of as-received Zn-5 catalyst was preserved under successive use in catalytic tests. The activity of thermally treated Zn-5 salt (at 140 °C) did not restore after methanol/THF washing and during subsequent use of Zn-5-140 catalyst its activity successively decreased.

A polymeric catalyst, polyaniline-sulfate, was studied in the transesterification of triglycerides (triacetin, castor oil) and esterification of fatty acid, ricinoleic acid with methanol at mild conditions (temperature of 50–60 °C). Polymer powder (PANI-S) and three samples of various contents of polymer deposited on carbon support were examined. The samples of catalysts, before and after catalytic tests were characterized by BET, FT-IR, XRD and SEM techniques. The acid capacity was also determined. All the samples were found to be active solid acid catalysts in both tested reactions. Catalytic performance of polyaniline-sulfate-based catalysts for methanolysis of triacetin (glycerol triacetate) the shortest triglyceride molecule differed from that for vegetable oil, castor oil, consisting of long chain triglycerides of ricinoleic acid. In transesterification of triacetin PANI-S powder was more active than carbon-supported catalysts. In methanolysis of vegetable oil the outermost surface of catalysts was mainly involved and much higher activity was exhibited by carbon-supported catalysts with deposited polymer, especially with low content of polymer (13.1 wt.%). The activity of polyaniline-sulfate-based catalysts was almost stable during recycling use in tested reactions. After five successive catalytic runs, their activities were found to be ca. 80–95% relative to the activities of fresh catalysts.

Present research concentrates on the process of anthraquinone degradation in the course of hydrogenation carried out in the presence of palladium catalyst. Hydrogenation experiments were carried out using agitated glass laboratory batch type reactor at atmospheric pressure of hydrogen and temperature of 55 °C. Catalytic tests were performed using solutions composed of 2-ethyl-9,10-anthraquinone (eAQ) and a mixture of eAQ and 2-ethyloxanthrone (OXO) with various proportions. Degradation of anthraquinone was studied and in particular, the role of reduced forms of quinone namely hydroquinone and its tautomer OXO is discussed. A difference in the course of reactions pathways: hydrogenation of aromatic rings to give 2-ethyl-5,6,7,8-tetrahydro-9,10-anthraquinone (active quinone) and hydrogenolysis reactions yielding degradation products was observed. Present research concentrates on the process of 2-ethyl-9,10-anthraquinone degradation on palladium catalyst. The role of reduced forms, hydroquinone-enol form and its keto-tautomer is discussed.

Gel-type resin with diamine functional groups, FCN, was used as a matrix for immobilization of ruthenium complexes. By reacting of RuCl 3 with swollen matrix of FCN polymer a series of Ru/FCN composites with various Ru loading (1%, 2%, and 4%) was prepared. All the characterization techniques (FT-IR, XRD, SEM, EDS, STEM, XPS, and DSC) proved the participation of functional groups in the coordination of Ru(III). These complexes contained both Cl- and N-ligands in various proportions depending on ruthenium loading in polymer. Taking into account the chelating character of N-ligands a hypothetical structure of octahedral Ru(III) complex coordinated to FCN polymer was proposed. 2%Ru/FCN when reduced by NaBH 4 exhibited catalytic activity in liquid phase hydrogenation of acetophenone. Higher selectivity in the presence of FCN supported Ru as compared to 2%Ru/Al 2 O 3 catalyst toward 1-phenylethanol was observed.

Present work is concerned with examination of catalytic properties of 12-tungstophosphoric acid and its silver salts AgxH3−xPW12O40 with Ag-content ranging from x = 0.5 up to x = 3 for transesterification of triglycerides with methanol to form methyl ester (biodiesel) under mild conditions (atmospheric pressure, temperature of 50–60 °C). Reaction was studied for triacetin, a model triglyceride and for vegetable oil, castor oil. Various techniques (BET, FTIR, XRD, XPS, laser diffraction, electron microscopy, SEM, and EDS) were used to characterize as-received Ag-salts and the samples separated after the catalytic tests. Because of the presence of methanol, which is the reactant, silver salts formed colloidal dispersion during the catalytic reaction. Under such conditions, all silver salts were active for transesterification of triglycerides. The conversion of triglycerides gradually decreases as the protons in heteropolyacid are replaced by Ag+ cations. However, due to the leaching of parent H3PW12O40 upon dissolving in methanol, the contribution of homogeneous catalysis was observed, especially in the presence of Ag-salts with low silver content such as Ag0.5H2.5PW12O40. Catalytic performance of Ag-salts in methanolysis of a short-chain triglyceride, triacetin, differs remarkably from that in castor oil comprising natural, long-chain triglycerides. After transesterification of castor oil, initially crystalline particles of Ag-salts partially rearrange to “gel-type” material making their further processing difficult. Although, no “gel-type” particles are formed after reaction of triacetin, the formation of “nanowires” due to partial reduction of some of Ag+ ions is observed.

Zinc hydroxy nitrate Zn5(OH)8(NO3)2 × 2 H2O (Zn-5) was proved to be active heterogeneous catalyst in the transesterification of triglycerides with methanol and it retained its activity in the next catalytic cycles. Systematic studies were performed to characterize catalytic performance of Zn-5 in methanolysis which was carried out under mild conditions (temperature 50−60 °C and atmospheric pressure). Reaction was studied for triacetin (glycerol triacetate), a model triglyceride molecule and for vegetable oil, castor oil {(triglyceride of 12-hydroxy-9-octadecenoic acid (ricinoleic acid)}. The homogeneously catalyzed reaction by KOH was performed for comparison as well. The effects of methanol to triglyceride molar ratio, catalysts loading, reaction temperature, and precontacting Zn-5 catalyst with reactants (methanol or triglycerides) were investigated. The influence of experimental variables on the course of triacetin methanolysis and in particular on the content of partial glycerides (diacetin, monoaceti...

Ruthenium (II) supported catalysts containing various amounts of [(η 5 -MeC 5 H 4 )Ru(η 3 -PPh 2 CHCH 2 )(η 1 -PPh 2 CHCH 2 )] + deposited on aluminated mesoporous silica of HMS type (Si/Al = 20 or 40) were synthesized by ion exchange method. The solids were characterized by XRD, 27 Al MAS NMR, FTIR and UV–vis spectroscopies. The textural properties were determined from nitrogen adsorption at 77 K. Textural analysis showed that increased loading of ruthenium complex onto support with high density of exchange sites (high Al content) eventually leads to overcrowding of active species in pore sections close to the pore mouth and hinders access to sites located deeper within the pore network. All HMS supported catalysts proved active and selective in phenylacetylene semihydrogenation under mild conditions (temperature 40 °C and H 2 pressure of 1 atm), their performance showing a complex pattern depending on the catalyst loading with the active phase and the degree of support alumination. Results indicate that the optimum catalytic performance requires high number of active sites within the catalytically active zone near the pore entrance, simultaneously avoiding blockage of the pore system and loss of the site isolation effect (controlled by Si/Al ratio and active phase content). Best heterogenized catalysts are more active than unsupported ruthenium complex in the homogeneous system. The supported catalysts are stable under reaction conditions and can be easily recovered and reused, without any loss of catalytic activity and selectivity.

The cesium salts Cs x H3−x PW12O40 of Cs content x = 2 up to x = 3 were tested as the catalysts in the gas and liquid phase reactions. Dehydration of ethanol and transesterification of triglycerides with methanol were selected as the catalytic reactions. Apart from the standard preparation, the catalysts were prepared by two-stage procedure with methanol or water as a solvent. The Cs-salts were characterized by FT-IR, XRD, scanning electron microscopy and energy dispersive X-ray techniques. In turn, the influence of Cs-salts composition on the pH and conductivity of their aqueous colloidal solutions was investigated. The results obtained by the latter techniques were also characteristic for acidity of surface layer of colloidal particles because of surface layer-solution equilibrium. It has been shown that the secondary structure of acidic cesium salts existing in crystalline samples (solid solution of H3PW12O40 in Cs3PW12O40) changes after contacting with polar medium to the system consisting most probably of Cs3PW12O40 core with epitaxial layer of heteropolyacid. This is result of the protons migration from bulk to surface layer of primary particles enhanced by polar medium. It strongly influences the surface acidity of primary particles as well as the activity of Cs-salts in transesterification of triglycerides with methanol. In such polar medium, Cs2HPW12O40 salt becomes the most active catalyst, more active than Cs2.5H0.5PW12O40. An accumulation of partial glycerides and in particular glycerol on the surface of primary particles of Cs-salts resulted in relatively low maximum conversion of triglycerides, most probably due to partial blockage of the catalytic centers. This effect and the almost constant activity of Cs-salts under recycling use in the transesterification experiments are considered to be experimental evidences that methanolysis over Cs-salts was accomplished with the participation of surface protons.

Platinum–polyaniline (2%Pt/PANI) composites are prepared using three precursor solutions of H 2 PtCl 6 differing in the pH and thus in the type of dominating chloro–aqua or chloro–hydroxo complexes of Pt(IV). Various characterization techniques (X-ray diffraction, FTIR and X-ray photoelectron spectroscopy, and electron microscopy; TEM, HRTEM) were employed in order to elucidate the role of platinum precursor composition in the state of Pt-species formed in the Pt/PANI composites. In all three as-received Pt/PANI composites, platinum in two valence states Pt(IV) and Pt(II) was observed thus showing redox reaction under preparation of composites. The reduction of Pt(IV) is much easier in the precursor solution of alkaline pH, i.e. when the Pt(IV) complexes comprising aqua and/or hydroxo ligands are the dominating ones. Under these conditions the content of Pt(II)-species is ca. 7× higher than that of Pt(IV) ones. Reduction of as-prepared composites by NaBH 4 gives 2%Pt/PANI catalysts of well-dispersed Pt-metal particles of size ranging from 1 nm up to 4 nm. The average diameters (2.24 nm) of Pt-particles was slightly smaller in 2%Pt/PANI catalyst prepared using H 2 PtCl 6 solution of acidic pH. Catalytic properties of Pt/PANI composites are tested in liquid phase hydrogenation of alkyne-type reactant, 2-butyne-1,4-diol (B3-D) and in gas-phase hydrodehalogenation of CCl 4 . In the former, a classical example of alkyne to alkene and finally alkane hydrogenation, a catalytic behavior of Pt/PANI composites in terms of activity and selectivity was found to be similar to that observed for typical inorganic carrier supported Pt-catalysts. CCl 4 hydrodehalogenation on Pt/PANI leads initially to the formation of chloroform, which is the desired reaction product. However, in the course of reaction liberation of HCl brings about large changes, both in overall activity, as well as the selectivity, giving large amounts of dimeric C 2 products, especially C 2 Cl 6 . It is speculated that these changes follow from reprotonation of PANI which acquires Bronsted acidity used in dimerization of CCl 3 radicals.

Platinum was introduced to poly(4-vinylpyridine) (P4VP) using aqueous H 2 PtCl 6 solution of pH 1.8. Several techniques (FTIR, Raman and X-ray photoelectron spectroscopy, extended X-ray absorption fine structure, X-ray diffraction, scanning electron microscopy) have been used to characterize the state of platinum species in Pt/P4VP composites. They showed incorporation of platinum mostly in the form of counterions, anionic complexes of Pt(IV) like [PtCl 6 ] 2− in which Cl − ligands predominated. Pyridinic-N of P4VP participates in the coordination of Pt(IV) species, however to definitively lower extent. Reduction of as-prepared Pt/P4VP composites by NaBH 4 produces Pt-nanoparticles appearing in the form of irregularly shaped aggregates. Catalytic performance of reduced Pt/P4VP composites in the hydrogenation of unsaturated carbon–carbon bonds in alkene (2-butene-1,4-diol, B2-D) and alkyne (2-butyne-1,4-diol, B3-D) substrates is similar to that of commonly used inorganic oxide supported Pt-catalysts. However, in the presence of Pt/P4VP catalysts the formation of by-products via hydrogenolysis reaction is strongly suppressed owing to a lack of acidic properties of P4VP matrix.

Palladium catalysts (0.125–0.5 wt.% Pd) supported by amine groups—functionalized gel-type resin (FCN) were studied in the hydrogenation of alkynes reagents, 2-butyne-1,4-diol and phenylacetylene. The catalysts were prepared by two routes. The first, “OAc” is based on the immobilization of Pd-precursor in the pre-swollen resin from THF solution of Pd(OAc) 2 , followed by chemical reduction of the Pd-centers. This method produces Pd particles of size in nano-scale. The second procedure, “aq” implies the deposition of Pd-species on dry resin beads using aqueous solution of PdCl 2 . Reduction of these Pd-species gives relatively large Pd particles, dominating are 30–50 nm in size. The SEM studies performed over the cross-section of catalysts grains showed location of Pd in outer shell of polymer beads in both “OAc” and “aq” catalysts; however, thinner layer of Pd appears in “aq” series catalysts. In the presence of all catalysts, prepared by “OAc” and “aq” methods the selectivity towards alkenes is high, above 90%. The catalysts of “aq’ series are much more active and more selective than “OAc” analogues giving selectivity to alkene ca. 94% at almost complete conversion of alkynes. Moreover, catalytic performance of “aq’ series catalyst is unchanged under recycling use. The catalyst was recovered and reused 4 times, maintaining its catalytic efficiency.

Gel-type resin (FCN) obtained as a result of copolymerization of glycidyl methacrylate (20 mol%), styrene (77 mol%) and ethylene glycol dimethacrylate (3 mol%) and functionalized by amine groups is studied as the support for Pd-catalysts (0.5–2 wt% Pd). Pd/FCN catalysts are characterized by number of techniques (FTIR, UV–Vis, XPS, SEM and HRTEM) and tested in the hydrogenation of alkynes, 2-butyne-1,4-diol (B3-D) and phenylacetylene (Phc). Catalysts are prepared by incorporation of palladium to the swollen particles of FCN resin using THF solution of Pd(OAc) 2 . In these conditions N and carbonyl groups of FCN polymer are involved in the bonding of Pd 2+ ions. This leads to decrease in swelling ability of polymer mass due to “crosslinking” of the polymer via Pd 2+ ions. Since the polymer-bound Pd species are only partially reduced under hydrazine treatment the reduced Pd/FCN samples swell less than pure FCN. In the reduced Pd/FCN samples, only at the lowest Pd-loading amounted to 0.5 wt% Pd, very well dispersed Pd-nanoclusters appear. At higher Pd content within the range 1–4 wt% Pd, the particles of Pd of size within the range 4–28 nm are formed and in all the samples the particles 8–16 nm in size predominate. In these catalysts, partial aggregation of Pd-nanoparticles proceeds, especially when the loading of Pd is higher than 1 wt%. The activity/selectivity behaviour of Pd/FCN catalysts is determined by the size of Pd-particles and swelling ability of polymer matrix under the catalytic run. In the presence of highly expanded catalysts with low Pd content, 0.5–1 wt% Pd, the alkynes substrates, B3-D or Phc are hydrogenated to alkene with selectivity 91–92% up to high alkynes conversion (90%). The suppression of alkene to alkane hydrogenation in the stage of alkynes is ascribed to high ability of Pd-centers to strong adsorption of alkyne substrate. It may also be related to steric hindrances of polymer in the vicinity of active Pd-centers caused by the swollen polymer network.

Methanolysis of castor oil to methyl esters, a key step in Biodiesel production, was studied with the use of KOH, H2SO4 and 12-tungstophosphoric acid (H3PW12O40, HPW) as the homogeneous catalysts. Reaction was also performed in the presence of solid salts of HPW, namely M x H3−x PW12O40, where M = K or Cs and x = 2, 2.5 and 3 (abbreviated as K2, K2.5, K3 and Cs2, Cs2.5, Cs3, respectively). The HPW salts were precipitated by K2CO3 and Cs2CO3 or CsCl. Their properties were characterized by BET, electron microscopy (SEM, EDS) and colloidal particles size distribution (laser diffraction technique). The potassium doped HPW samples, K2 and K2.5, prove to be much more active catalysts (ca. 3 times) than their Cs-containing analogues. Among the K, Cs salts, K2 salt was the most active catalyst. The activity of catalysts was found to depend on preparation stages such as the temperature of drying or annealing and aging of the samples. Microscopic studies evidenced colloidal form of Cs and K salts particles under the catalytic reaction. The size of colloidal particles was found to depend upon the type of cation, Cs+ or K+, as well as the “history” of catalysts preparation (temperature of drying). Based on the results obtained in this work, we concluded that activity was determined by the accessibility of the reactants to acid sites which is facilitated by the high surface area and open structure of the colloidal form. This may lead to better utilization of acid sites and higher activity of samples with lower content of K+ or Cs+ cations in the HPW.

The cationic ruthenium(II) complex [(η5-MeC5H4)Ru(η3-PPh2CHCH2)(η1-PPh2CHCH2)]+ (1) containing the hemilabile phosphaallyl ligand in two different coordination modes has been immobilized inside the pores of aluminated hexagonal mesoporous silica HMS(Si/Al = 40) by direct ion exchange method. This material was characterized by X-ray diffraction, thermogravimetric analysis, FTIR, solid state NMR (29Si, 27Al), UV–Vis, and X-ray photoelectron spectroscopies. The textural properties were determined from nitrogen adsorption at 77 K. (1)/HMS(Si/Al = 40) was shown to be active and selective in the catalytic hydrogenation of phenylacetylene.