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Hydrogen transfer reaction is one of the valuable and potential solutions for selective hydrogenation. We report here that single-atom Pt supported by CeO2 could effectively catalyze the selective hydrogenation of nitroaromatics to corresponding amine through hydrogen transfer reaction. [ABSTRACT FROM AUTHOR]

In this work, the impregnation order of the second metal and the catalytic performance of low loaded Pd and Ni bimetallic catalysts were studied using different supports (γ-Al2O3, γ-Al2O3–Mg, CaCO3 and RX3). These catalysts were assessed in the selective hydrogenation of 1-pentyne and the purification of a mixture of 1-pentene/1-pentyne 70/30 vol%. The results showed that the synthesized catalysts were active and very selective (≥ 85%) for obtaining the desired product (1-pentene). Different adsorbed species (–C≡C– and –C=C–) were observed on the bimetallic surface using in situ DRIFT analysis, which can be responsible of the high selectivity reached. The order of impregnation of the metals modifies the electronic and geometric properties of the synthesized catalysts. The best catalytic performance was obtained when the Pd is impregnated in second place: Ni–Pd/Support. The results show that the synthesized bimetallic catalysts have favorable properties and are promising for olefin purification reactions. [ABSTRACT FROM AUTHOR]

Hierarchically porous materials offer the opportunity for catalyst development in regards to improving catalytic performances. In the present work, the combination of latex synthesis, sonochemical reduction and two-step catalysed sol-gel process has been demonstrated to be a versatile method for preparing supported catalysts with tailored hierarchical porosity. This method has been used to prepare porous Pt/SiO2 catalysts with mesopore and macropore size ranges as large as 2-15 nm and 90-400 nm, respectively. These hierarchically porous catalysts presented an excellent catalytic performance for the selective hydrogenation of p-chloronitrobenzene (p-CNB) to p-chloroaniline (p-CAN). Selectivity values up to 100% at 80% conversion of p-CNB and initial reaction rates up to 74.0 molCNB/min molPt were obtained, while a commercial catalyst exhibited both a lower selectivity of 90.8% and a lower initial reaction rate of 47.7 molCNB/min molPt. [ABSTRACT FROM AUTHOR]

The selective hydrogenation of acrolein has been studied on different pseudomorphic Pt/Ru(001) bimetallic surfaces with platinum coverages of 0.28, 1.1, and 3.7 ML, using temperature-programmed reaction spectroscopy (TPRS), reflection absorption infrared spectroscopy (RAIRS), and Auger electron spectroscopy (AES). The submonolayer (0.28 ML) Pt/Ru(001) surface was found to be inactive towards acrolein hydrogenation and behaves mostly like a clean Ru(001) surface with the platinum layers enhancing the decarbonylation and decomposition pathways. The multilayer (3.7 ML) Pt/Ru(001) surface behaved like a Pt(111) surface with the acrolein mostly decomposing to CO and surface carbon with no observable hydrogenation activity. However, the 1 ML Pt/Ru(001) pseudomorphic surface was found to display properties different from those of Ru(001) and Pt(111) surfaces with the desorption of propanal, the only hydrogenation product, around 330 K, and propylene around 370 K. A submonolayer (0.67 ML) PtRu/Ru(001) alloy system prepared to study the effect of surface mixing (with small amounts of subsurface platinum) gave results similar to those of surface platinum at submonolayer coverages. This suggests that, at submonolayer coverages, there is little difference in the properties of these surfaces with respect to the location of the platinum atoms in the Pt/Ru(001) system. [ABSTRACT FROM AUTHOR]

High metal loading NiCu-based catalyst of Picula™ series produced by sol-gel technique was applied to furfural hydrogenation in the presence of hydrogen. This reaction represents the stabilization of pyrolysis oil that involves the selective reduction of aldehydes and ketones to alcohols and unsaturated C-C double bonds of pyrolysis oils components. The catalysts were pre-reduced at 250 and 300 °C. According to XRD analysis results, copper is mainly in the metallic state, and Ni is mostly in the form of oxide and silicate. XPS measurements reveal that hydrogen treatment at 250 °C leads to the partial reduction of Ni to the metallic state (6 %) while further reduction at 300 °C leads to an increase in this proportion up to 39 %. A 100 % selectivity towards furfuryl alcohol was achieved at 130 °C and 5 MPa of hydrogen in a batch reactor using decyl alcohol as a solvent. In the experiments with i-propanol as a solvent at 110-170 °C the main product was furfuryl alcohol, but minor components traced back were tetrahydrofurfuryl alcohol, 2-methylfuran and isopropyl furfuryl ether. The lower catalyst reduction temperature promotes the formation of isopropyl ester, while a higher reduction temperature favors further furfuryl alcohol hydrogenation. [ABSTRACT FROM AUTHOR]

Encapsulation of metal nanoclusters in porous solid polymer materials is a promising approach to combine the outstanding properties of both, heterogeneous and homogeneous catalysts. We report heterogeneous nano-engineered catalysts containing Pd-nanoparticles (NPs) confined within highly-porous hollow polymeric framework of hyper cross-linked polystyrene (HPS). HPS with different surface functionalities (amine vs. sulfonate) were used for impregnation by Pd precursors of different nature and followed by a variety of catalyst post-treatments. The catalysts have been tested in two model key reactions for the synthesis of fine chemicals: selective hydrogenation of 2-methyl-3-butyne-2-ol to 2-methyl-3-butene-2-ol (MBE) and Suzuki cross-coupling of 4-bromoanisole with phenylboronic acid. Optimization of the Pd/HPS preparation and reaction conditions allowed attaining high selectivity (~99 %) to target MBE at close to full conversion. For Suzuki cross-coupling more than 90 % yield of coupling product was obtained under mild reaction conditions and the absence of phase transfer agent. Our results demonstrate the potential of HPS as a suitable support for tailoring metal NPs properties and circumvent undesirable metal leaching. Graphical Abstract: . [ABSTRACT FROM AUTHOR]

The gas phase hydrogenation of maleic anhydride (MA) to succinic anhydride (SA) and the subsequent hydrogenolysis to γ-butyrolactone (GBL) was studied on SiO-AlO-supported Ni catalysts modified with Cu and prepared by incipient wetness impregnation (Ni-I, CuNi-I) and coprecipitation-deposition (CuNi-PD) methods. The samples were characterized by N adsorption at −196 °C, X-ray diffraction, temperature-programmed reduction, transmission electron microscopy and H chemisorption. Catalytic tests were performed between 170 and 220 °C at atmospheric pressure in a fixed bed reactor. Crystalline NiO along with a Ni phase strongly interacting with the support was observed in the oxide precursors. The extent of the strongly interacting Ni phase diminishes according to the following pattern: CuNi-PD > CuNi-I > Ni-I, along with a proportional rise of the NiO phase. The proportion of small to large metal particles, formed after reduction, followed the same pattern as that observed for the extent of Ni phase. All catalysts were very active in the MA hydrogenation to SA, but displayed distinct performances with respect to the subsequent SA hydrogenolysis. Hydrogenolytic activity and GBL yield increased following the same pattern as that obtained for the extent of Ni phase. In addition, the effect of raising temperature on hydrogenolytic activity was more important in the case of Ni-I and CuNi-I than for CuNi-PD. Furthermore, CuNi-PD was more selective to GBL than CuNi-I. These results showed that there is an important effect of Cu addition and preparation method on both the structure and catalytic performance of the metal Ni phase. [ABSTRACT FROM AUTHOR]

Molybdenum carbide (Mo2C and Ni/Mo2C) catalysts were compared with Pd/SiO2 for the hydrogenation of several diene molecules, 1,3-butadiene, 1,3- and 1,4-cyclohexadiene (CHD). Compared to Pd/SiO2, Mo2C showed similar hydrogenation rate for 1,3-butadiene and 1,3-CHD and even higher rate for 1,4-CHD, but with significant deactivation rate for 1,3-CHD hydrogenation. However, the hydrogenation activity of Mo2C could be completely regenerated by H treatment at 723 K for the three molecules. The Ni modified Mo2C catalysts retained similar activity for 1,3-butadiene hydrogenation with significantly enhanced selectivity for 1-butene production. The 1-butene selectivity increased with increasing Ni loading below 15 %. Among the Ni modified Mo2C catalysts, 8.6 % Ni/Mo2C showed the highest selectivity to 1-butene, which was even higher selectivity than that over Pd/SiO. Compared to Pd/SiO2, both Mo2C and Ni/Mo2C showed combined advantages in hydrogenation activity and catalyst cost reduction, demonstrating the potential to use less expensive carbide catalysts to replace precious metals for hydrogenation reactions. [ABSTRACT FROM AUTHOR]

Modification of supported Pt catalysts with thiols has recently been shown to improve the hydrogenation selectivity of α,β-unsaturated aldehydes to unsaturated alcohols. Here, we apply a variety of organic thiol coatings to Pd/AlO catalysts that typically have a much lower intrinsic selectivity for desired product formation. Thiol monolayers were found to increase hydrogenation selectivity to cinnamyl alcohol; however, unlike with Pt catalysts, the increase was independent of the identity of the organic tail. [ABSTRACT FROM AUTHOR]

Monodisperse RhCu bimetallic nanoparticles (NPs) with various compositions were prepared by the co-reduction of Rh and Cu ions in the presence of poly( N-vinyl-2-pyrrolidone) (PVP). Powder X-ray diffraction analysis of the PVP-stabilized RhCu NPs revealed the formation of a novel solid-solution structure in which the Rh and Cu atoms are randomly distributed. The catalytic properties of the colloidal RhCu NPs were studied using hydrogenation of 4-nitrobenzaldehyde as a test reaction. We found that the RhCu NPs efficiently reduced 4-nitrobenzaldehyde using atmospheric hydrogen at room temperature and that the selectivity to 4-aminobenzaldehyde was enhanced from ~70 % with monometallic Rh NPs to ~97 % with RhCu NPs with a Cu content of 50 %. [ABSTRACT FROM AUTHOR]

Deep understanding of catalysis fundamentals allows the development of highly efficient catalysts of the newest generation. In this paper, the attention is given to studies of novel inorganic materials, like fiber glass textiles of silicate origin. In this case the nanostructured catalysts were prepared which reveal high performance in different catalytic reactions. Some applications of these materials in the production of petrochemicals are presented. [ABSTRACT FROM AUTHOR]

The catalytic action of MoN and Au/MoN has been assessed in the selective gas phase hydrogenation of p-chloronitrobenzene ( p-CNB) to p-chloroaniline ( p-CAN). The nitrides were synthesised via temperature programmed treatment of MoO in H + N and Au introduced by deposition-precipitation with urea. We have examined the influence of nitride crystallographic phase (tetragonal β-MoN vs. cubic γ-MoN) and surface area (7-66 m g) on the catalytic response. Catalyst activation by temperature programmed reduction has been monitored and the reduced catalysts characterised in terms of BET area/pore volume, H chemisorption/temperature programmed desorption (TPD), powder X-ray diffraction (XRD), elemental analysis, scanning (SEM) and transmission (TEM) electron microscopy and X-ray photoelectron spectroscopy (XPS) measurements. The formation of β- and γ-MoN was confirmed by XRD and TEM. γ-MoN exhibits a platelet morphology whereas β-MoN is characterised by an aggregation of small crystallites. Hydrogen chemisorption and TPD analysis have established a greater hydrogen uptake capacity (per unit area) for β-MoN relative to γ-MoN, which is associated with surface nitrogen deficiency, i.e. higher surface Mo/N for β-MoN. Incorporation of Au on both nitrides resulted in an increase in surface hydrogen. The Au phase takes the form of nano-scale particles with a mean size of 7 and 4 nm on β-MoN and γ-MoN, respectively. Both β-MoN and γ-MoN promoted the exclusive hydrogenation of p-CNB to p-CAN where the β-form delivered a higher specific (per m) rate; the specific rate for γ-MoN was independent of surface area. The inclusion of Au on both nitrides served to enhance p-CAN production. [ABSTRACT FROM AUTHOR]

In the field of catalysis by metals, a new insight for the nanodesign of supported heterogeneous catalysts is the tailoring of metallic nanoparticles. In this work, well-faceted monometallic nanoparticles (Pd, Pt, Ni) exposing mostly the {111} crystallographic facet are obtained in aqueous solution and are deposited on an alumina support. The involved mechanisms of nanoparticles formation are determined and are evidenced to be different as a function of the nature of the metal. In the case of palladium the mechanism consists in an oriented attachment of palladium nanoparticles leading to the energetically most favourable stacking of nanoparticles, at the origin of the early differentiation of the nanoparticles shapes and of the formation of the well-faceted palladium nanoparticles. In the case of platinum, the mechanism seems to be a combination of aggregation of already reduced nuclei and direct reduction depending on the experimental conditions. In the case of the less reductible metal, nickel, well-faceted nanoparticles are not obtained during the synthesis and only a thermal activation under hydrogen can engender their formation. The impact of the {111} crystallographic facet for platinum and nickel is very important and induces a drastic increase of selectivity towards olefins formation with a selectivity close to the one of a palladium catalyst which is the most selective metal for the selective hydrogenation of poly-unsaturated hydrocarbons. [ABSTRACT FROM AUTHOR]

An efficient copper catalyst for the one-pot one-step hydrogenation + esterification of unsaturated free fatty acids is described. The high selectivity in hydrogenation promoted by copper, combined with the high activity in esterification observed with solid mixed oxides allows one to directly obtain stabilized methyl esters. [ABSTRACT FROM AUTHOR]

This paper reports palladium nanoparticle formation and stabilization by hypercrosslinked polystyrene and the catalytic properties of the nanocomposites obtained. The nanocomposites were characterized using low-temperature nitrogen physisorption, X-ray photoelectron spectroscopy and transmission electron microscopy. The inorganic nanoparticle size was found to depend on the NaPdCl loading with the smallest nanoparticles formed at 0.1 wt% of Pd. The nanocomposites synthesized showed high activity [up to 27 mol/(mol Pd s)] and selectivity (up to 98.5 % at 100 % conversion) in selective hydrogenation of acetylene alcohols. [ABSTRACT FROM AUTHOR]

Aldol reactions of several aldehydes have been investigated over acidic and basic catalysts in supercritical carbon dioxide at 180 bar and 100 °C. Both acidic (Amberlyst-15, tungstosilicic acid (TSA) on SiO and MCM-41) and basic (hydrotalcite) materials showed interesting performance in this preliminary study under the entitled reaction conditions. Small and linear aldehydes, such as propanal, butanal, pentanal and hexanal, react more efficiently than the branched 3-methylbutanal, which is converted much slower. Whereas Amberlyst-15 showed the highest conversion based on the catalyst mass, tungstosilicic acid-based catalysts were significantly better if the rates were related to the number of acidic sites (>1000 h). The rate depends both on the dispersion and the kind of support. Strikingly, tungstosilicic acid (TSA) on MCM-41 was also an effective catalysts for the selective C=C double bond hydrogenation of 2-butenal and is therefore a potential catalyst for the 'one-pot' synthesis of 2-ethyl-2-hexenal and 2-ethylhexanal via combined hydrogenation and aldol reaction from 2-butenal. A number of characterisation techniques, such as temperature-programmed desorption of ammonia (NH-TPD), transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), etc. were used to get an insight into the catalyst structure, which support a high dispersion and strong acidity of the tungsten based species on silica and MCM-41. [ABSTRACT FROM AUTHOR]

Hydrogenation of citral over Ir/TiO and IrAu/TiO catalysts was studied. Catalysts were prepared by deposition-precipitation with urea (Ir/TiO) and sequential incorporation of the metals using a combined DPU-incipient wetness impregnation approach (IrAu/TiO). Samples were reduced in H at 573 K (LT) and 773 K (HT). These materials were characterized by transmission electron microscopy (HAADF), TPR and CO adsorption followed by DRIFT. The liquid phase hydrogenation of citral was studied in a Parr type batch reactor at 363 K and a H pressure of 0.62 MPa. An Ir/TiO catalyst prepared by wet impregnation was used as reference catalyst. High selectivity to unsaturated alcohols was found, the only reaction products were geraniol and nerol for Ir/TiO DPU and IrAu/TiO catalysts. The IrAu/TiO (HT) catalyst showed the higher conversion levels. [ABSTRACT FROM AUTHOR]

The development of new improved catalysts for the selective hydrogenation of aromatic nitrogroups is still a field of high interest for the chemical industry. Hydrogenation of aromatic nitrogroups to the corresponding aromatic amines is one of the most important applications for precious metal powder catalysts (PMPC). In this paper various commercial PMPC technologies such as palladium, platinum, platinum modified with copper and platinum modified with vanadium on activated carbon powder supports were compared to each other in regard to activity and selectivity for hydrogenation of 1-chloro-2-nitrobenzene. In this reaction, catalysts comprised of vanadium modified platinum on activated carbon showed excellent activities and selectivities towards 2-chloroaniline. Catalyst performance was affected by the ratio of platinum to vanadium and the properties of the carbon. The role of vanadium as an effective modifier to avoid accumulation of hazardous aromatic hydroxylamines was explained. [ABSTRACT FROM AUTHOR]

The effect of addition of Re to activated carbon-supported Ru and Pd catalysts in the hydrogenation of 15 wt% succinic acid aqueous solutions to 1,4-butanediol (BDO) was examined. The yield and selectivity were in the range 62–66% at 160 °C and 150 bar over the Re promoted catalysts. Bio-succinic acid from a fermentation process could be efficiently hydrogenated on 4 wt%Re–2 wt%Pd/C without significant loss of selectivity. [ABSTRACT FROM AUTHOR]

Supported Ionic Liquid Catalysts (SILCA) designed by immobilization of catalytic species residing in an ionic liquid layer, which in turn was immobilized on a solid support, were applied on the selective hydrogenation of citral in a batch reactor and in a continuous reactor. Different ionic liquids with and without addition of acid modificators were studied in terms of the catalyst activity and product selectivity. Consequently, mechanistic kinetic models describing the differences in the activity and selectivity of the catalysts consisting different ionic liquids, were developed. [ABSTRACT FROM AUTHOR]

Gold catalysts of the type made in kilogram quantities by Project AuTEK are being used to demonstrate their advantages over other precious metal catalysts in achieving selectivity in both liquid- and gas-phase reactions which have commercial potential. The high activity of gold catalysts under mild conditions is a valuable asset in achieving the high selectivities. [ABSTRACT FROM AUTHOR]

Advances in developing new heterogeneous catalysts which hydrogenate preferentially the C=O group of ά,β-unsaturated aldehydes to obtain the desired products, namely unsaturated alcohols, will be reviewed by considering the parameters which control the intramolecular selectivity: support material, nature and particle size of the individual metals, selective poisoning, presence of a second metal, preparation method or catalyst precursor, temperature of reduction, host-guest interactions in zeolites, substituents on the C=C bond and pressure effects. Recent attempts with bimetallic and silver catalysts to hydrogenate only the C=O group of other polyfunctional organic compounds in the gas phase without simultaneous hydrogenation of aromatic or furan rings will be shown. [ABSTRACT FROM AUTHOR]

Pt–Sn/ALa10 and Pt–Pb/ALa10 catalysts (10 wt% La2O3) were studied in the selective hydrogenation of crotonaldehyde. Oxidized Pt2+ and reduced Pt0 species were identified by XPS on the bimetallic catalysts. High selectivity to crotylalcohol was obtained on the Pt–Pb/ALa10 catalyst where an electron transfer effect from Pb to Pt was proposed. For the Pt–Sn/ALa10 catalyst the formation of Pt–SnO x–La2O3 complexes showing low activity and low selectivity was inferred. [ABSTRACT FROM AUTHOR]

The influence of the acid treatment on cyclohexanone selectivity of phenol hydrogenation over Pd on active carbon was studied in liquid phase reaction and by temperature-programmed desorption. Acid treatment of activated carbon led to an increased cyclohexanone/cyclohexanol ratio. Acid modification of the carbon support enriched the electron density of Pd, and enhanced the desorption of the phenoxy species, which resulted in improved cyclohexanone selectivity in phenol hydrogenation. [ABSTRACT FROM AUTHOR]