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CeO promoted with either 1 wt% Pt or 1 wt% Pd was evaluated as a model system for passive NO adsorber applications. According to NO storage experiments conducted over the temperature range 80-160 °C, promotion with Pt resulted in higher NO storage efficiencies than for the Pd-promoted material. However, for NO storage at 80 and 120 °C, the latter released more NO below 350 °C during temperature-programmed desorption in relative and absolute terms, the Pt analog releasing most of its stored NO above 350 °C. DRIFT spectra showed that the use of Pd leads to preferential adsorption of NO in the form of nitrites, while predominately nitrate formation is observed over the Pt promoted material. Overall, the use of Pd promoted CeO is preferred for low temperature NO storage and release due to its ability to store NO as thermally labile nitrites. Graphical Abstract: [ABSTRACT FROM AUTHOR]

A group of new polymolybdates was synthesized and tested in the catalytic oxidation of cycloalkanes. Investigated compounds exhibit broad structural diversity including polymolybdates with isolated anionic clusters (0-dim), polymeric anions (1-dim), Mo-O layers (2-dim) as well as hexagonal and orthorhombic molybdenum oxides (3-dim). All studied molybdenum complexes were found to be active in the reaction conditions yielding ketones and alcohols as main products. In the case of layered compounds (2-dim), dicarboxylic acid was detected in the mixture of reaction products. The structure of investigated molybdenum compounds was shown to have influence on yields and selectivities of the investigated reactions. Anionic layers separation (in 2-dim materials) as well as type and charge of organic cations present in the compounds are prime examples of structural factors influencing the oxidation reactions efficiencies. On the basis of obtained results and literature reports a mechanism for the oxidation of cycloalkanes by polymolybdates has been proposed. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Density functional theory (DFT), employing semilocal approximations to describe electron exchange and correlation effects, tremendously advanced the research in the realm of computational catalysis. It allows to calculate atomic and electronic structure details of extended systems like bulk solids, surfaces or nanoparticles with reasonable accuracy at moderate computational cost. However, semilocal approximations suffer from shortcomings such as self-interaction errors (SIEs). This work discusses results obtained using two established and related approaches, namely DFT + U and orbital-dependent hybrid density functionals. Both methods partially alleviate some of the problems incurred by SIEs and are widely used in the computational community. We discuss four case studies involving reducible oxide materials: (i) the oxidative dehydrogenation of methanol at small vanadium oxide clusters supported on the CeO(111) surface, (ii) the adsorption of Au atoms on the reduced CeO(111) surface, (iii) stabilities of various terminations of the VO(0001) surface, and (iv) the adsorption of water on the FeO(111) surface. Compared with semilocal functionals including DFT + U, we report substantial improvements in band gaps, defect formation energies, as well as activation barriers and emphasize the important role of state-of-the-art experiments for assessing DFT. Limitations of hybrid functionals due to the imposed computational workload and inherent functional approximations are discussed. To overcome these limitations, alternatives in terms of generalized RPA and embedded wavefunction-based methods are suggested. Graphical Abstract: [ABSTRACT FROM AUTHOR]

This report has described three environmentally acceptable Brønsted acidic catalytic systems ( p-toluene sulfonic acid, sulfamic acid and 1,3-disulfoimidazolium trifluoroacetate [DSIM][CFCOO] ionic liquid) for the preparation of complex library of anti-diastereomer of 2,3-dihydro-1,2,3-trisubstituted-1 H-naphth [1,2-e][1,3]oxazines 4 from the three components reaction of 2-naphthol, p-substituted aromatic aldehydes and primary amines in 25 % aqueous ethanol at room temperature or in neat conditions at 80 °C. The reactions utilized 15 mol% of the two conventional acids to produce 82-97 % of naphthoxazines during 10-30 min. The same reactions could also be performed satisfactorily within 8-20 min employing 10 mol% of task specific acidic 1,3-disulfoimidazolium trifluoroacetate [DSIM][CFCOO] as catalyst. The three catalysts were recycled for four runs in aqueous ethanol with excellent catalytic activity. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Zirconia-palladium (ZrO-Pd) core-shell nanoparticles were synthesized by two different methods, namely, hydrothermal and common precipitation method. A non-ionic surfactant polyvinylpyrrolidone was used as dispersant while ammonia solution as precipitator to fabricate the zirconia core particles, on which the palladium shell was subsequently forming by reducing palladium nitrate with an eco-friendly reductant-ascorbic acid. A mechanical blending method was applied to fabricate the three-way catalysts (TWCs). The physicochemical properties of ZrO-Pd nanoparticles and catalytic performance of each catalyst were systematically studied and compared. The scanning electron microscopy, transmission electron microscopy-energy diffraction X-ray, BET, X-ray diffraction of the ZrO or the ZrO-Pd nanoparticles results clarified that ZrO-Pd core-shell nanoparticles with high dispersion and surface area were successfully prepared through hydrothermal method. A higher content of Pd was obtained in catalysts fabricated by hydrothermal method according to the inductively coupled plasma atomic emission spectrometry results. The CO pulse adsorption, H-temperature-programmed reduction results and catalytic tests indicated that the aged catalysts (calcined at 1000 °C) possessed the higher active component dispersion, lower reduction temperature and performed the higher catalytic activity than the fresh catalysts (calcined at 550 °C), especially for that with ZrO-Pd core-shell nanoparticles synthesized through hydrothermal method. Thus, the ZrO-Pd core-shell structure can significantly enhance the thermal stability of TWCs. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Pd-Cu/APT catalysts were prepared by an impregnation method (PC-IM) and an evaporation ammonia method (PC-AE), respectively. Their catalytic activities for low-temperature CO oxidation were studied. It is found that PC-AE shows much higher catalytic activity. Characterizations results suggest that Cu species exist as the Cu(OH)Cl phase with nanoplatelet morphology in PC-AE. In addition, PC-AE possesses high specific surface area and enhanced reducibility, which may contribute to the excellent catalytic ability. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Liquid-phase hydrodechlorination of chlorotrifluoroethylene (CTFE) to trifluoroethylene (TrFE) with molecular hydrogen was studied over palladium-supported catalysts. BaSO4, Al2O3 and activated carbon (AC) were used as supports, respectively. The results showed that the Pd/AC catalysts exhibit higher activity than Pd/BaSO4 and Pd/Al2O3. The treatment of activated carbon with HNO3 led to a considerable increase of surface functional groups containing oxygen atoms, which resulted in a higher dispersion of palladium on the supports and enhancement of catalytic activity. The stability of the catalyst was investigated, one reason for the inhibition was the accumulation of NaCl on the surface of Pd/AC that blocks the pores of carbon support. The activity of Pd/AC could partially recovered by washing with water. The other irreversible deactivation of the catalyst are from the change of particle size and the pore structure, leaching of Pd, a decrease of BET surface area and Pd surface area of Pd/AC catalyst. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Poisoning of platinum catalysts by sulphur compounds is a significant problem that prevents their application in untreated gas streams. We introduce a novel concept to circumvent the poisoning problem by encapsulating individual platinum nano-particles with silica layers that act as selective membranes. Greatly enhanced sulfur tolerance for sufficiently dense illustrates the potential of our approach to design noble metal catalysts that survive in sulphur containing gas streams. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Dodecanethiol-protected gold nanoparticles were deposited onto fumed SiO2 (Cab-O-Sil) via colloidal deposition. The catalyst was treated with a strongly oxidative KMnO4 or K2MnO4 solution. Low-temperature conversion in catalytic CO oxidation increased dramatically following the oxidative treatment and subsequent thermal activation at 300 °C to burn off residual organic species. On the other hand, the treatment with Fenton’s reagent did not lead to any positive effect. The influences of the average sizes of pre-synthesized gold particles (1.8, 2.1, 3.9, 9.9 nm) and the choice of different supports (SiO2, TiO2, C) were investigated, and relevant characterization using TG/DTG, XRD, TEM, EDX, and HAADF was conducted. The catalyst stability as a function of time on stream was also surveyed. This work establishes the beneficial effect of treating dodecanethiol-capped gold catalysts by KMnO4 or K2MnO4. Dodecanethiol-capped gold nanoparticles were deposited onto SiO2, TiO2, or carbon support, and the resulting catalysts were treated by aqueous KMnO4 or K2MnO4 followed by treatment in O2–He at 300 °C. The catalytic activity in low-temperature CO oxidation was increased due to the creation of Au–MnO x interfaces.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Dodecanethiol-protected gold nanoparticles were deposited onto fumed SiO2 (Cab-O-Sil) via colloidal deposition. The catalyst was treated with a strongly oxidative KMnO4 or K2MnO4 solution. Low-temperature conversion in catalytic CO oxidation increased dramatically following the oxidative treatment and subsequent thermal activation at 300 °C to burn off residual organic species. On the other hand, the treatment with Fenton’s reagent did not lead to any positive effect. The influences of the average sizes of pre-synthesized gold particles (1.8, 2.1, 3.9, 9.9 nm) and the choice of different supports (SiO2, TiO2, C) were investigated, and relevant characterization using TG/DTG, XRD, TEM, EDX, and HAADF was conducted. The catalyst stability as a function of time on stream was also surveyed. This work establishes the beneficial effect of treating dodecanethiol-capped gold catalysts by KMnO4 or K2MnO4. Dodecanethiol-capped gold nanoparticles were deposited onto SiO2, TiO2, or carbon support, and the resulting catalysts were treated by aqueous KMnO4 or K2MnO4 followed by treatment in O2–He at 300 °C. The catalytic activity in low-temperature CO oxidation was increased due to the creation of Au–MnO x interfaces.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Our group recently developed a series of Au/M xO y/TiO2 catalysts for CO oxidation, and demonstrated that some of these catalysts are still active after high-temperature treatment whereas Au/TiO2 deactivates significantly due to the sintering of gold nanoparticles at elevated temperatures (Ma Z, Overbury SH, Dai S (2007) J Mol Catal A 273:97). In the current work, the performance of Au/M xO y/TiO2 (M = Al, Ca, Fe, Zn, Ga, Y, Zr, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb) catalysts in water-gas shift (WGS) reaction was evaluated. The influences of different metal oxide (M xO y) additives and pretreatment temperatures were investigated, and the catalyst stability as a function of reaction time on stream was tested. Some of these novel gold catalysts, with high activity and stability in water-gas shift, furnish new possibilities for further fundamental research and industrial development. [ABSTRACT FROM AUTHOR]

Partially fluorinated metal oxides were studied for manufacturing dichloropentafluoropropanes (CF3CF2CHCl2 and CCl2FCF2CHClF) and controlling the selectivity of their isomers. When activated by elemental fluorine or dichlorodifluoromethane, metal oxides such as TiO2, HfO2, Al2O3, and ZrO2, exhibited catalytic activity in the reaction of dichlorofluoromethane with tetrafluoroethylene. In the case of the TiO2 catalyst, the more fluorine incorporated, the higher the selectivity was for the CCl2FCF2CHClF formation. The fluorine-activated TiO2 catalyst was identified by XRD and XPS as a mixture of TiO2 and partially fluorinated TiO2 including TiOF2. [ABSTRACT FROM AUTHOR]

This study deals with diesel DeNOx catalysis by physically mixed Pd/TiO2/Al2O3 and water–gas-shift-reaction (WGSR) catalysts under CO-rich conditions at a CO/NOx ratio of 16. In the post-Euro IV era, many diesel engines are expected to produce CO-rich exhaust emissions due to the trend toward emission regulation and limitations in related technologies. Under these circumstances, the passive DeNOx strategy utilizing CO as a single reductant can be considered appropriate. The Pd/TiO2/Al2O3 catalyst is well known for its high DeNOx performance when CO and H2 are available as NOx reductants. However, when CO is used as a single reductant, the catalyst shows poor DeNOx activity, even if the CO concentration is exceptionally high (CO/NOx = 16). In this study, the DeNOx activity of Pd/TiO2/Al2O3 was noticeably improved by physically mixing it with a proper WGSR catalyst (Cu/ZnO/Al2O3), which is capable of producing H2 and feeding it to Pd/TiO2/Al2O3 successfully even in the presence of O2. The NOx conversion exceeded 70% at 400–450 °C using a Pd/TiO2/Al2O3 + Cu/ZnO/Al2O3 catalyst mixture at a weight ratio of 33:67. The reaction gas consisted of 500 ppm NO, 8000 ppm CO, 8 vol.% O2, 5 vol.% CO2 and 10 vol.% H2O and w/f was 0.1 g s/cm3. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A catalytic conversion of ethanol to propylene was carried out by use of H-ZSM-5 with Si/Al2 ratio of 280. In H-ZSM-5 modified at a molar ratio of La to Al2 of 2.2, the propylene selectivity was 31% at 0.1 MPa, 550 °C and was higher than those of non-modified and other metal modified catalysts. In the La-modified H-ZSM-5, a rapid increase in ethylene formation was also depressed and the propylene selectivity was still high (24%) even after 28 h-reaction. A catalytic conversion of ethanol to propylene was carried out by use of H-ZSM-5 with Si/Al2 ratio of 280. In H-ZSM-5 modified at a molar ratio of La to Al2 of 2.2, the propylene selectivity was 31% at 0.1 MPa, 550 °C and was higher than those of non-modified and other metal modified catalysts. In the La-modified H-ZSM-5, a rapid increase in ethylene formation was also depressed and the propylene selectivity was still high (24%) even after 28 h-reaction.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Nitrogen containing nano-structured carbon catalysts were grown on Fe/Al2O3 and Ni/Al2O3 supports using acetonitrile pyrolysis. The post-pyrolysis samples were tested for activity in the oxygen reduction reaction (ORR) and oxidative dehydrogenation (ODH) reaction. Samples were characterized using BET, XPS and TEM. The samples grown over iron containing supports gave the highest activity in both reactions. There was a strong correlation between ODH and ORR activity suggesting the possibility of a common active site between reactions with the quinone/hydroquinone group being a possible candidate. XPS analysis supported this hypothesis showing that catalysts with a higher percentage of oxygen in the form of quinones tend to have the highest ORR and ODH activity. XPS analysis also demonstrated that samples with higher pyridinic nitrogen content, which is a marker for edge plane exposure and may be a part of the ORR active site, gave higher ORR and ODH activity. TEM images confirm that samples with high pyridinic nitrogen content tend to form structures with higher edge plane exposure. Because the active site, regardless of its identity, likely lies on the graphitic edge plane, this leaves the possibility that a common active site is not necessary to explain the correlation between ODH and ORR activity. Nitrogen containing, nano-structured carbon catalysts were shown to exhibit a correlation between the activities of oxidative dehydrogenation and electrocatalytic oxygen reduction reactions.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Vanadium phosphate oxide (VPO) catalysts derived from VOHPO4·0.5H2O and VO(H2PO4)2 precursors showed improved rates in the catalysed liquid phase oxidation of p-cymene. Both catalysts showed high performance with conversions of up to 30% achieved within 3 h with a selectivity towards the tertiary cymene hydroperoxide (TCHP) of 75–80% when compared to lower conversions and poorer TCHP selectivity in the non-catalysed industrial oxidation processes that takes about 8–12 h reaction time. The temperature dependent structural changes during activation within the catalysts were studied by in situ XRD and TGA-MS. The in situ XRD showed that the VO(H2PO4)2 form mainly an amorphous phase at temperature up to 600 °C while above 650–750 °C a stable VO(PO3)2 phase was obtained. The in situ XRD studies of the (VO)2P2O7 phase derived from VOHPO4·0.5H2O showed to became more crystalline with increasing temperature from 400 to 750 °C. No formation of VOPO4 phases were observed in the activated (VO)2P2O7 catalyst even at high temperature under the in situ XRD conditions. VPO catalysts derived from VOHPO4·0.5H2O and VO(H2PO4)2 precursors improve oxidation rates and improved tert-cymene hydroperoxide selectivity during the liquid-phase oxidation of p-cymene compared to non-catalyzed oxidations. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A series of Ce1− xCu xO2 (0 ≤ x ≤ 0.1) nanostructured oxide systems was prepared using a modified reverse microemulsion method. The thermal decomposition of the carbonate and hydroxide precursors into oxides systems was studied using thermal analysis methods (EGA-TGA/DTG/SDTA). The morphology and the structure of the samples were characterized by XRD and BET analysis as well as visualized by scanning electron microscopy (SEM). The morphology of the obtained nanoparticles depended on a kind of the precursors used. The copper substituted CeO2 materials formed mono phase solid solutions, which were catalytically active in the incineration of various VOC molecules (ethylene, methanol, acetone). The correlation between activity of the studied catalysts and copper content has been found. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The facile two-step preparation procedure of a novel magnetic nano-solid acid catalyst is described, which includes grafting an ionic liquid onto Fe3O4 nanoparticles, followed by the sulfonation of phenyl groups in the ionic liquid. The catalytic performance of this novel material has been systematically studied in the acetal formation of benzaldehyde and ethylene glycol. The experimental results testify this catalyst possesses high catalytic activity with a yield of 97% under mild reaction conditions. Furthermore, the catalyst is readily separated using a permanent magnet and it is reusable without any significant decrease in catalytic activity. [ABSTRACT FROM AUTHOR]

Microporous silicoaluminophosphates SAPO-5, SAPO-11 and SAPO-40 have been tested as solid acid catalysts in the dehydration of xylose into furfural (FUR) under biphasic aqueous-organic conditions, at 170 °C. For all materials, no decrease in catalytic activity is observed after three consecutive recycling runs. Furfural yields at 4 h using SAPO-11 (34–38%) are comparable with that for HMOR zeolite with Si/Al ~ 6 (34%), under similar reaction conditions, while H2SO4 (0.03 M) gives 2% FUR. Complete xylose conversion is reached within 16–24 h, with furfural yields of up to 65%. Brønsted and Lewis acidity of the silicoaluminophosphates was determined through FTIR analysis of adsorbed pyridine, and tentatively correlated with the catalytic performances. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A novel generation of homogeneous catalysts for the epoxidation of geraniol, in the presence of tert-butyl hydroperoxide oxidant is reported. Oxidovanadium(IV) complexes of 3-hydroxy-4-pyrone and 3-hydroxy-4-pyridinone ligands exhibit excellent activity and selectivity towards the 2,3-epoxygeraniol product, only differing in the reaction times and turnover frequencies. The pyrone based complexes are the most efficient catalysts showing performances similar to that of the well known oxidovanadium(IV) acetylacetonate catalyst. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Aromatization of isobutene was investigated using zeolite H-ZSM-5 (Si/Al = 30) as well as physical mixtures of H-ZSM-5 with metal oxides (Ga2O3, ZnO and CuO). The study was aimed at determining the effect on the selectivity to aromatic products by introducing an oxide/zeolite interface. Of the three oxides, ZnO was found to enhance the yield of aromatic products with the highest aromatic selectivity being attained with ZnO/H-ZSM-5 (1:2 weight ratio). The addition of Ga2O3 had very little effect and the addition of CuO was not found to be beneficial. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In this work, we have investigated a novel one-step fabrication of Ag-deposited Fe2O3 nanoparticles and their application for the catalytic reduction of 4-nitrophenol to 4-aminophenol by NaBH4. To deposit Ag onto them, Fe2O3 particles were dispersed in a reaction mixture consisting of ethanolic AgNO3 and butylamine, and then the reaction mixture was incubated and shaken for 40 min at 45 °C. With this simple and surfactant-free fabrication of Ag-deposited Fe2O3 nanoparticles, we can avoid contamination in the final product, which makes them suitable for further catalytic applications. Since the magnetic particles are readily recovered from the solution phase without centrifugation and/or filtering, the Ag-deposited Fe2O3 nanoparticles prepared in this work have been exploited as solid phase catalysts for the reduction of 4-nitrophenol in the presence of NaBH4. At the end of the reaction, the Ag-deposited Fe2O3 catalyst particles still remain active. They can thus be separated from the product, 4-aminophenol, simply using a neodium magnet and can be recycled a number of times. [ABSTRACT FROM AUTHOR]

Nanocrystalline TiO2 with average crystallite sizes 7 and 15 nm were synthesized by the solvothermal method using titanium n-butoxide and 1,4-butanediol as titanium precursor and solvent, respectively. Four transition metals (Ag, Co, Ni, Pt) were supported on the TiO2 supports by incipient wetness impregnation with metal loadings 1 and 25 atomic%. For any metal type, metal dispersion and CO oxidation activities were higher when the catalysts were prepared on the larger crystallite size TiO2 for both high and low metal loadings, despite their lower surface areas. The presence of higher amount of Ti3+ on the larger crystallite size TiO2 probably stabilized small metal particles during impregnation, calcination, and reduction steps via stronger metal-support interaction; hence higher CO oxidation activities and lower light-off temperature were obtained. [ABSTRACT FROM AUTHOR]

Irradiation with light (UV–vis and visible) was shown to increase the rate of the Heck reaction at 90–140 °C using both heterogeneous and homogeneous catalysts. The photoreduction of Pd(II) is most likely the reason for the higher activity under irradiation with light. This was demonstrated by the addition of sodium formate. [ABSTRACT FROM AUTHOR]

The work mainly reported that CeO2–ZrO2–La2O3 mixed oxide was synthesized by deposition–precipitation method and used as support of Rh catalyst. The physicochemical properties of the resultant CeO2–ZrO2–La2O3 mixed oxides were characterized by X-ray powder diffraction (XRD), Vis-Raman, N2 adsorption, transmission electron microscopy, temperature-programmed reduction, and oxygen storage capacity and the catalytic activities of Rh-loaded CeO2–ZrO2–La2O3 catalysts were evaluated by the reduction reaction of NO by CO. The combination of XRD and Raman results demonstrates that the resultant CeO2–ZrO2–La2O3 mixed oxides have a mixed phase comprised mainly of m-phase, c-phase, and t-phase. Compared with the counterpart prepared by co-precipitation method, Rh-loaded CeO2–ZrO2–La2O3 catalysts prepared by the deposition–precipitation method exhibited higher heat tolerance and better catalytic activity for the reduction of NO by CO as well as more uniform and discrete nanoparticles. The structural and textural characteristics caused by synthesis technique and the high dispersity of Rh on the materials are dominant contributors to the improvement of catalytic performance. [ABSTRACT FROM AUTHOR]

Esterification of acetic acid with n-butanol catalyzed by supported heteropoly acid dodecatungstophosphoric acid, H3PW12O40 (DTP), on acid modified Montmorillonite clay (AT-Mont) matrix were carried out. Among different catalysts, 20% DTP supported onto AT-Mont (15 min) showed the highest catalytic activity with 88% conversion having nearly 100% selectivity towards n-butyl acetate. [ABSTRACT FROM AUTHOR]

Heterogeneous Pd(0) catalysts were synthesized using bayberry tannin-grafted silica beads (BT-SiO2) as the supports, in which bayberry tannin acts as a stabilizer to prevent Pd(0) nanoparticles from aggregation as well as an antioxidant for keeping Pd(0) nanoparticles from oxidation. The main physical and chemical properties of the catalysts were characterized by Ultraviolet diffusion reflection spectra, X-ray diffraction, Transmission microscopy, and X-ray photoelectron spectroscopy. Experimental results indicated that Pd(0) nanoparticles stabilized by BT-SiO2 were highly active, selective and reusable in liquid-hydrogenation of unsaturated organic compounds. [ABSTRACT FROM AUTHOR]

A series of Al–Zr mixed oxides with different molar ratios was prepared by coprecipitation method and characterized by N2 physiorption, XRD, NH3-TPD and CO2-TPD. Solid solution is formed in the mixed oxides. And the composition of the mixed oxides has significant influence on their acid–base properties. The catalysts were examined with glucose reaction in hot compressed water at 180 °C. The prepared oxides exhibit very good catalytic activity and glucose conversion can be increased from 46.6 to 85%. The products distribution is related with the acid–base property of the oxide. [ABSTRACT FROM AUTHOR]

NHTS x with different noble-metal contents, were new bi-functional titanosilicates with hollow structure used in one-pot process, their catalytic performances of propylene direct epoxidation were investigated extensively. The results show that with the increase of reaction temperature and reaction time, propylene conversion and the yield of propylene oxide increase, while the selectivity to propylene oxide decreases; meanwhile, L acidity and surface acidity are also concerned with their catalytic performance. NHTS x with hollow structure and noble-metal combined, are fine catalysts for application in the propylene direct epoxidation process. [ABSTRACT FROM AUTHOR]

The effects of Co loading and calcination temperatures on the catalytic activity of Co/Al2O3 for selective catalytic reduction (SCR) of NO with ethylene in excess oxygen were investigated. Co/Al2O3 showed high and low activities when calcined at high (800 °C) and low (350 °C) temperatures, respectively. The formation and dispersion of cobalt species for catalysts calcined at 350 and 800 °C as well as for Al2O3 were studied by XRD, UV–vis and FTIR spectra. Combined with DRIFTS results of ad-species and reaction experiments, it allowed us to correlate the catalytic activity with active sites of Co/Al2O3, and the catalytic functions of active cobalt species and support were clarified. Co3O4 species contributed to the oxidation of NO to various nitrates and of C2H4 to reactive formate species, even in the absence of O2, whereas the side reaction of ethylene combustion occurred simultaneously when excess oxygen was present. Tetrahedral Co2+ ions in CoAl2O4, which acted as the active sites, were responsible for the reaction between formate and nitrate species to form organic nitro compound. [ABSTRACT FROM AUTHOR]

Cellulose samples with different crystallinities (33–85%) were prepared by treating a commercial cellulose (crystalline, 85%) with phosphoric acid under different conditions. Supported Fe, Co, Ni, Pd, Pt, Rh, Ru, Ir, Ag, and Au catalysts were examined for the conversion of cellulose with a crystallinity of 33% in water medium in the presence of hydrogen, and Ru was found to be the most effective catalyst for the formation of sorbitol. We demonstrated that carbon nanotubes (CNTs) were the most efficient support of Ru for cellulose conversion, and the mean size of Ru nanoparticles over CNT was ~8.8 nm. NH3-TPD and H2-TPD characterizations suggest that plenty of acid sites and unique hydrogen species over the Ru/CNT are important for sorbitol formation through hydrolysis and hydrogenation of cellulose. A 40% yield of hexitols (including 36% of sorbitol) could be achieved over the Ru/CNT catalyst for the conversion of the commercial cellulose (crystalline, 85%), and this yield was the highest one reported to date for the direct conversion of cellulose into sugar alcohols. [ABSTRACT FROM AUTHOR]

Metal (IV) phosphates of tin, zirconium and titanium were used as catalysts for selective dehydration of sorbitol to isosorbide. Tin phosphate showed the highest selectivity to isosorbide with a moderate conversion. The deactivation rates of catalysts were fitted by an empirical Voorhies equation and the results showed tin phosphate had the lowest deactivation rate with the least values of m and n. Thermal analysis showed deactivation rate was in accordance with coke deposition. The acidity caused by functional groups of the catalysts was the direct factor for catalyst lifetime, which was evidenced by NH3-TPD, XRD, IR and Raman characterizations. [ABSTRACT FROM AUTHOR]

Sulfated zirconia (SO4 2−/ZrO2) was proved as an efficient catalyst for the esterification of fatty acids and alcohols, the alkyl esters of long chain fatty acids are wildly used in industry and daily life. In this paper, the esterification of long chain fatty acid (both saturated and unsaturated) with simple alcohol catalyzed by SZ catalyst was presented. It is found that the degree of esterification reaction of the fatty acids with 1-butanol has a close relationship with the length and unsaturation degree of the chain. The longer the carbon chain is, the more difficult it is to react; the higher the unsaturation level is, the more difficult it is to respond. The related regulation will be confirmed and serve as the dictator for other reactions within this system. [ABSTRACT FROM AUTHOR]

We assess heat and mass transfer limitations in in situ studies of model catalysts with a first-principles based multiscale modeling approach that integrates a detailed description of the surface reaction chemistry and the macro-scale flow structures. Using the CO oxidation at RuO2(110) as a prototypical example we demonstrate that factors like a suppressed heat conduction at the backside of the thin single-crystal, and the build-up of a product boundary layer above the flat-faced surface play a significant role. [ABSTRACT FROM AUTHOR]

The Direct Synthesis, or Rochow Synthesis, involves the reaction of methyl chloride, CH3Cl (MeCl), with Cu–Si contact masses (promoted with 1–2% of Zn, Sn, and P) to form methylchlorosilanes. Flow reactor studies (1 bar MeCl at 300 °C) showed that contact masses promoted with Zn, Sn, and P (triply promoted) demonstrated the highest Si and MeCl conversion at early reaction times. In situ infrared spectroscopy suggested that in contrast to the doubly promoted catalysts (where CH3 groups were primarily bound to Si), surface CH3 showed appreciable binding to the copper component of the triply promoted contact mass. This change in surface composition ultimately led to a drop in reactivity and selectivity of the triply promoted catalyst. [ABSTRACT FROM AUTHOR]

The effects of Co loading and calcination temperatures on the catalytic activity of Co/Al2O3 for selective catalytic reduction (SCR) of NO with ethylene in excess oxygen were investigated. Co/Al2O3 showed high and low activities when calcined at high (800 °C) and low (350 °C) temperatures, respectively. The formation and dispersion of cobalt species for catalysts calcined at 350 and 800 °C as well as for Al2O3 were studied by XRD, UV–vis and FTIR spectra. Combined with DRIFTS results of ad-species and reaction experiments, it allowed us to correlate the catalytic activity with active sites of Co/Al2O3, and the catalytic functions of active cobalt species and support were clarified. Co3O4 species contributed to the oxidation of NO to various nitrates and of C2H4 to reactive formate species, even in the absence of O2, whereas the side reaction of ethylene combustion occurred simultaneously when excess oxygen was present. Tetrahedral Co2+ ions in CoAl2O4, which acted as the active sites, were responsible for the reaction between formate and nitrate species to form organic nitro compound. [ABSTRACT FROM AUTHOR]

Cu–Mg–Al mixed oxide catalysts were prepared from calcination of hydrotalcite-like compounds. XRD patterns showed formation of CuO and MgO phases, where aluminum oxides are well dispersed. The Cu–Mg–Al catalysts exhibited high stability during 40 h with time on stream for the shift reaction at 250 °C, which can be related to the major presence of metallic copper, confirmed by in situ XRD reaction measurements, and no change of the mean crystallite size, suggesting high resistance to sintering. DRIFTS results confirmed the major presence of metallic Cu particles at the catalyst surface but also an insignificant amount of cationic copper species. [ABSTRACT FROM AUTHOR]

OMS-2 (2 × 2 type octahedral molecular sieve) and cerium doped OMS-2 were synthesized by refluxing method. The platinum doped on both samples was prepared by impregnation method for catalytic oxidation of formaldehyde. These catalysts were characterized by BET, XRD, SEM, H2-TPR and Laser Raman. Results show that OMS-2 formed needle-shape nanocrystal structure. The addition of Ce before the formation of the OMS-2 structure obstructs the process due to mismatch of the cation size. Rather than into the framework of the structure, the addition of Pt after the formation of the OMS-2 structure was loaded on the surface of catalysts, which strongly influenced the bonding of the Mn–O lattice of OMS-2. The properties of the catalyst structure determine the temperature of complete oxidation of HCHO while Pt promotes this reaction at a lower temperature range due to active surface oxygen species and lattice defects. [ABSTRACT FROM AUTHOR]

Mo–V–Te–P mixed oxide catalysts, prepared by a dry-up method at various pHs (in the range of about 1.0–9.0), have been tested in the partial oxidation of isobutane. The best catalytic performance was achieved over a catalyst prepared at a pH about 7.0. In this case, high selectivity to methacrolein (37.0%) at an isobutane conversion of 12.7% has been obtained at 380 °C. The surface V4+/V5+ ratios of the calcined samples were strongly influenced by the pH in the synthesized solution, which is one of the key factors in the catalytic performance for selective oxidation of isobutane. [ABSTRACT FROM AUTHOR]

γ-Bi2MoO6 catalysts prepared by a co-precipitation method were calcined at various temperatures (425–675 °C), and were applied to the oxidative dehydrogenation of n-butene to 1,3-butadiene in a continuous flow fixed-bed reactor. Conversion of n-butene and yield for 1,3-butadiene were high at low calcination temperature (425–475 °C), but were decreased with increasing calcination temperature (525–675 °C). Temperature-programmed reoxidation (TPRO) measurements revealed that the catalytic performance of γ-Bi2MoO6 was well correlated with the oxygen mobility of the catalyst. Yield for 1,3-butadiene was increased with increasing oxygen mobility of γ-Bi2MoO6 catalyst. Among the catalysts tested, γ-Bi2MoO6 catalyst calcined at 475 °C showed the best catalytic performance due to its facile oxygen mobility. [ABSTRACT FROM AUTHOR]

Catalytic epoxidation of α-H-containing olefins with air over nanosized metal oxides under mild conditions has been first reported. Nanosized Co3O4 was considerably active for the epoxidation of α-pinene and cinnamyl chloride with air at atmospheric pressure. A substrate α-pinene conversion of 70.75 mol% with an epoxide selectivity of 87.68% was achieved at 363 K over Co3O4. Once Co3O4 was further modified with metal oxides or ammonium salts through a simple procedure consisting of ultrasonic agitation, drying and calcination, thus-prepared catalysts presented lower catalytic activity and higher epoxide selectivity than cobalt oxide itself. Over Co3O4 modified with surfactants, the conversion of α-pinene was somewhat reduced to 48.86–63.76 mol%, but the epoxide selectivity was increased to 92.12–94.83%. However, the composite oxide CoO x–SnO x (10:1) catalyzed 48.21 mol% of α-pinene conversion with 85.82% of epoxide selectivity. For the substrate cinnamyl chloride, the best result was 40.76 mol% of conversion and 87.17% of epoxide selectivity achieved by CoO x–ZnO (5:1). It is noteworthy that the use of TBHP in small amounts initiated the reaction efficiently, and the lack of TBHP would lead to a low conversion and selectivity. Catalytic epoxidation of α-H-containing olefins with dry air over nanosized metal oxides under mild conditions was first reported. Co3O4 and Co3O4 modified with surfactants could catalytically convert 48.86–70.75 mol% of α-pinene, with the epoxide selectivity high up to 87.68–94.83%. The best result of cinnamyl chloride catalyzed by 5:1 CoO x–ZnO was 40.76 mol% of conversion with 87.17% of selectivity to epoxide. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Successively impregnated Pt–Mo/Al2O3 and Pt–Fe/Al2O3 catalysts exhibited large enhancement effect in H2 formation rate of liquid phase methanol reforming. Added Mo oxide forms monolayer on Al2O3 and facilitates the higher dispersion of Pt particles. In the case of Fe, formation of some surface bimetallic clusters between Pt and Fe was confirmed by XAS analysis, which causes the enhancement effect of H2 formation in MeOH–H2O reaction. [ABSTRACT FROM AUTHOR]

Three-component hybrid catalyst comprised of Co/SiO2, Pd/β-zeolite and CuO/ZnO/Al2O3 with different configurations was applied for the effective production of gasoline-range iso-paraffins from synthesis gas. In the case of the powdery mixture, a killing effect of CuO/ZnO/Al2O3 on Co/SiO2 for the Fischer-Tropsch reaction was observed. On the contrary, individual functions of the above-mentioned components were successfully achieved when the hybrid catalyst with the same composition was prepared in a granular form. The reason is tentatively explained as the feasibility for the interfacial migration of the zinc component from CuO/ZnO/Al2O3 to Co/SiO2. [ABSTRACT FROM AUTHOR]

ZnMeIIIFeO4 catalysts with different trivalent metal (MeIII = Fe, Al, Cr, Mn, and Co) were prepared by a co-precipitation method, and were applied to the oxidative dehydrogenation of n-butene to 1,3-butadiene. Successful formation of ZnMeIIIFeO4 catalysts was confirmed by XRD and ICP-AES analyses. Catalytic performance of ZnMeIIIFeO4 catalysts in the oxidative dehydrogenation of n-butene strongly depended on the identity of trivalent metal (MeIII). Acid properties of ZnMeIIIFeO4 catalysts were measured by NH3-TPD experiments, with an aim of correlating the catalytic performance with the surface acid property of the catalysts. It was revealed that yield for 1,3-butadiene increased with increasing surface weak-acid density of ZnMeIIIFeO4 catalyst. Among the catalysts tested, ZnFeFeO4 catalyst with the largest surface weak-acid density showed the best catalytic performance in the oxidative dehydrogenation of n-butene. [ABSTRACT FROM AUTHOR]

A comparison of different catalyst systems (Fe–Mo, Co–Mo or Ni–Mo nanoparticles supported on calcium carbonate) has been performed in order to optimize the carbon nanotube (CNT) growth. The influences of the reaction temperature, metal loading and carbon source on the synthesis of CNTs were investigated. Dense CNT networks have been synthesized by thermal chemical vapor deposition (CVD) of acetylene at 720 °C using the Co–Mo/CaCO3 catalyst. The dependence of the CNT growth on the most important parameters was discussed exemplarily on the Co catalyst system. Based on the experimental observations, a phenomenological growth model for CVD synthesis of CNTs was proposed. The synergy effect of Mo and active metals was also discussed. [ABSTRACT FROM AUTHOR]

A new class of hybrid organic/inorganic molecular catalysts with high, local catalyst concentrations is demonstrated by supporting organic and organometallic catalysts on magnetic nanoparticle based polymer brushes (MPB). Poly(styrene) brushes containing Co(III)-salen or piperazine side chains are prepared via atom-transfer radical polymerization (ATRP) from Fe3O4 nanoparticles modified with appropriate initiator molecules. The polymer brush architecture promotes the cooperative interactions required for Co-salen catalyzed ring-opening of epoxides as demonstrated in the hydrolytic kinetic resolution of rac-epichlorohydrin. In addition, the piperazine functionalized MPB catalyst contains the high catalyst concentration that is required for promoting the Knoevenagel condensation of benzaldehyde and malononitrile with this type of amine catalyst. All the MPB catalysts were easily removed from solution via application of a magnetic field, allowing straightforward recovery and reuse. The versatile MPB architecture can be used to create a variety of recoverable supported organic or organometallic catalysts. [ABSTRACT FROM AUTHOR]

An efficient method to enhance the catalytic properties of Zn-ferrite catalyst in the oxidative dehydrogenation of n-butene to 1,3-butadiene is proposed. The incorporation of phosphorous compound in Zn-ferrite is very effective to improve the catalytic activity as well as to maintain extremely long useful lives at high oxygen to n-butene ratio. It is found that the amount of phosphorous is critical and the presence of appropriate amount of phosphorous in catalyst may contribute the catalyst stabilization by which unfavorable reduction of Fe3+ sites to Fe2+ is effectively suppressed. This suggests that the oxygen mobility is maintained as high as the redox mechanism keeps constantly working. On the other hand, the effort to increase the population of mobile oxygen species by the introduction of external oxygen donor phase is found to be rather ineffective regardless of the external donor oxides used. [ABSTRACT FROM AUTHOR]

A series of Ru/Al2O3/cordierite monolithic catalysts were prepared and characterized by BET, XRD, TPR, TEM and SEM-EDAX. The catalytic performances in selective hydrogenation of benzene to cyclohexene were investigated in a continuous fixed-bed reactor. The preparation conditions significantly influence morphology, particle size, and surface area of the catalyst, subsequently affecting the catalytic performances. It was found that higher calcination temperature of the Ru-based monolithic catalyst led to the conglomeration and crystallite growth of the t-RuO2, which will decrease the catalytic activity. The lower thickness and the larger pore size of the alumina washcoating layer are the preferential choices to obtain higher cyclohexene selectivity due to the improved internal mass transfer of cyclohexene. It was also found that high ruthenium loading resulted in deep hydrogenation of cyclohexene. Moreover, the reduction temperature was optimized to 473 K and excess high temperature led to the deterioration of both activity and cyclohexene selectivity. [ABSTRACT FROM AUTHOR]

The Cu/ZrO2 catalysts prepared by the co-precipitation with NaOH–Na2C2O4 mixture solution exhibited high activity and stability in the hydrogen production through partial oxidation of methanol. The methanol conversion and the selectivity to hydrogen can be up to 100 and 92% at 533 K with molar ratio of O2/CH3OH at 0.5, respectively. Characterization results indicated that CuO were well dispersed into the ZrO2 lattices which induced the strong Cu–Zr interaction as well as good stability and lower valance of Cu species were supposed as the activate sites. The good catalytic performance and long-term stability of the novel Cu/ZrO2 catalysts could be attributed to the high copper species dispersion on zirconium components and high active specific copper surface area with a much strong Cu–Zr interaction as well as a beneficial synergy of ZrO2 promotion. [ABSTRACT FROM AUTHOR]

Polyethylene glycol based diphosphinite ligands and their Wilkinson type Rh-polymeric carbonyl complexes were prepared for homogeneous hydroformylation of styrenes. The effect of reaction variables such as temperature, pressure, P/Rh ratio, Substrate/Rh ratio, phosphine and phosphinite ligands on the activity and selectivity performance were discussed in detail. The catalyst showed a high rate of reaction, TON and tunable regioselectivity depending upon reaction conditions as compared to conventional Rh-phosphine based catalysts. [ABSTRACT FROM AUTHOR]