Photo-Fenton degradation of 17β-estradiol in presence of α-FeOOHR and H2O2

A novel photocatalyst, α-FeOOH-coated resin (α-FeOOHR), was prepared and applied for the photodegradation of natural estrogen 17β-estradiol (E2) in presence of H₂O₂ under the relatively weak UV irradiation. The continuing loading of ferric oxide on resin was achieved by in situ hydrolysis of Fe³⁺ in alkaline solution. The effects of initial pH, catalyst loading, oxidant concentration and iron leaching on the photodegradation of E2 were investigated. The batch photodegradation experiment showed that high removal efficiency of E2 and fairly good mechanic stability could be obtained by the spherical photocatalyst α-FeOOHR in aqueous solutions. The photodegradation efficiencies slightly decreased with the increase of initial pH in the wide pH range of 3–11. Increase of oxidant and catalyst will enhance photodegradation efficiencies thus lead to increase the Ferric leaching. Neglected iron leaching showed the stability of the loaded α-FeOOH withstanding the oxidation. X-ray photoelectron spectrum (XPS) shed light on the surface activity change of photocatalyst and heterogeneous catalytic essence of this process.     

Effects of the preparation methods on the performance of the Cu–Cr–Fe/γ-Al2O3 catalysts for the synthesis of 2-methylpiperazine

Co-precipitation, impregnation and ultrasonic sol–gel (USG) methods have been used to prepare Cu–Cr–Fe/γ-Al₂O₃ catalysts, which were further used to synthesize 2-methylpiperazine. The catalysts were characterized by XRD, XPS, TG/DSC, BET, TPR, AAS and TEM. It is found that preparation method can greatly impact the catalytic performance of the catalysts, the Cu–Cr–Fe/γ-Al₂O₃ catalyst prepared by the ultrasonic sol–gel method proved to be the most active and stable for this reaction. The dispersion and stabilization of Cu⁰ in the reduced catalysts are attributed to the existence of CuCr₂O₄ and Fe₂O₃. A surprising copper migration was detected by XPS analysis for the Cu–Cr–Fe/γ-Al₂O₃-USG catalyst after the calcination process, which may be crucial to the high activity and stability of this catalyst.     

A comparative study on the selective hydrogenation of α,β unsaturated aldehyde and ketone to unsaturated alcohols on Au supported catalysts

The hydrogenation of trans,4-phenyl,3-buten,2-one (benzalacetone) and trans,3-phenyl, propenal (cinnamaldehyde) was carried out on Au supported on iron oxides catalysts. Commercial goethite (FeOOH), maghemite (γFe₂O₃) and hematite (αFe₂O₃) were used as supports. The catalytic activity of Au/Fe₂O₃ reference catalyst, supplied by the World Gold Council, was also investigated. Gold catalysts and the parent supports were characterized by BET, X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption of ammonia (NH₃-TPD) and high resolution transmission electron microscopy (HRTEM).Among the catalysts investigated Au supported on FeOOH shows the highest activity and selectivity to UA in the hydrogenation of unsaturated carbonyl compounds whereas Au supported on αFe₂O₃ are the less active and selective catalysts.The catalytic activity and selectivity to unsaturated alcohols (UA) in the hydrogenation of benzalacetone and cinnamaldehyde are less influenced by the morphology of gold particles and are mainly influenced by the nature of the support.A correlation between the reducibility of the catalysts and the activity and selectivity to UA has been found. Increasing the reducibility of the catalysts both the activity and selectivity to UA increase. These results let us to argue that active and selective sites are formed by negative gold particles formed through the electron transfer from the reduced support to the metal.     

Performance of Pd catalysts supported on nanocrystalline α-Al2O3 and Ni-modified α-Al2O3 in selective hydrogenation of acetylene

Nanocrystalline α-Al₂O₃ and Ni-modified α-Al₂O₃ have been prepared by sol–gel and solvothermal methods and employed as supports for Pd catalysts. Regardless of the preparation method used, NiAl₂O₄ spinel was formed on the Ni-modified α-Al₂O₃ after calcination at 1150 °C. However, an addition of NiO peaks was also observed by X-ray diffraction for the solvothermal-made Ni-modified α-Al₂O₃ powder. Catalytic performances of the Pd catalysts supported on these nanocrystalline α-Al₂O₃ and Ni-modified α-Al₂O₃ in selective hydrogenation of acetylene were found to be superior to those of the commercial α-Al₂O₃ supported one. Ethylene selectivities were improved in the order: Pd/Ni-modified α-Al₂O₃–sol–gel > Pd/Ni-modified α-Al₂O₃-solvothermal ≈ Pd/α-Al₂O₃–sol–gel > Pd/α-Al₂O₃-solvothermal  Pd/α-Al₂O₃-commerical. As revealed by NH₃ temperature program desorption studies, incorporation of Ni atoms in α-Al₂O₃ resulted in a significant decrease of acid sites on the alumina supports. Moreover, XPS revealed a shift of Pd 3d binding energy for Pd catalyst supported on Ni-modified α-Al₂O₃–sol–gel where only NiAl₂O₄ was formed, suggesting that the electronic properties of Pd may be modified.     

Coral-like nanostructured α-Mn2O3 nanaocrystals for catalytic combustion of methane: Part I. Preparation and characterization

Coral-like nanostructured α-Mn₂O₃ nanocrystals were prepared by oxidative decomposition of MnCO₃, exhibiting tremendous activity in the catalytic combustion of methane. This prepared α-Mn₂O₃ nanocrystals showed ultra-high stability during reaction while the structure feature was unaffected. The ultra-stable structure of the α-Mn₂O₃ catalyst has been demonstrated by characterization of SEM, XPS, XRD, Raman spectroscopy. The performance of the α-Mn₂O₃ nanocrystals has proven reproducible and potentially to be an applied catalyst for methane combustion.     

Influence of water on fast hydrogenation reactions with monolithic and slurry catalysts

The influence of water on the hydrogenation of α-methyl styrene (AMS) with Ni–Al₂O₃ slurry and monolithic catalysts was investigated. Addition of water to this liquid-phase hydrogenation results in a four-phase system, as applied industrially for the partial hydrogenation of benzene. Addition of already a limited amount of water to AMS reaction mixture resulted in a strong decrease in activity. This could not be explained by a poisoning effect of water.It has been made plausible that the reaction changes from diffusion limited in hydrogen to diffusion limited in AMS in the presence of free water. The formation of a water layer around the catalyst introduces an external mass transfer resistance for AMS. Two mechanisms are proposed to explain the trend of decreasing activity upon increasing the amount of water. Both the slurry and the monolithic catalyst show the same behaviour. The water layer is formed on monoliths as easily as on slurry catalysts. As the formation of a water layer is a prerequisite for high selectivity in the partial hydrogenation of benzene, the application of monoliths in this reaction is promising.     

The functionalities of Pt/γ-Al2O3 catalysts in simultaneous HDS and HDA reactions

A Pt/γ-Al₂O₃ catalyst was tested in simultaneous hydrodesulfurization (HDS) of dibenzothiophene and hydrodearomatization (HDA) of naphthalene reactions. Samples of it were subjected to different pretreatments: reduction, reduction–sulfidation, sulfidation with pure H₂S and non-activation. The reduced catalyst presented the best performance, even comparable to that of Co(Ni)Mo catalysts. All catalyst samples were selective to the HDS reaction over HDA, and to the direct desulfurization pathway of dibenzothiophene HDS over the hydrogenation reaction pathway of HDS. The effect of H₂S partial pressure on the functionalities of the reduced Pt/γ-Al₂O₃ catalyst was studied. The results showed that an increase in H₂S partial pressure does not cause poisoning, but an inhibition effect, without changing the catalyst selectivity. Accordingly, the activity trends were ascribed to adsorption differences between the different reactive molecules over the same catalytic active site. TPR characterization along with a thermodynamics analysis showed that the active phase of reduced Pt/γ-Al₂O₃ is constituted by Pt⁰ particles. However, presulfidation of the catalyst leads to a mixture of PtS and Pt⁰ which has a negative effect on the catalytic performance without changing catalyst functionalities.     

Selective propylene dimerization to 2,3-dimethylbutenes by homogeneous catalysts prepared by oxidative addition of α-nitroketones to nickel(0) complexes in the presence of phosphine ligands and organoaluminium co-catalysts

Novel nickel catalysts, prepared in situ by oxidative addition of α-nitroketones to nickel(0) complexes, in the presence of a phophine ancillary ligand and activated by organoaluminium co-catalysts were investigated in propylene oligomerization with the aim to selectively obtain 2,3-dimethylbutenes (DMB). In particular, the effect of the nature of the α-nitroketonate ligand as well as of the basicity and bulkiness of the phosphine on catalyst performances were studied. Finally, the influence of the type of organoaluminium co-catalyst and reaction temperature were examined.In particular, when the Ni(cod)₂/tricyclohexylphosphine (PCy₃)/α-nitroacetophenone (naph)/methylalumoxane (MAO) catalytic system was employed, the highest up to now reported regioselectivity within C₆ cut (>90%) was achieved. Moreover, the use of balanced mixtures of MAO and Et₂AlCl allowed to optimize the catalyst performances up to an overall yield to DMB of almost 70%, a significant productivity being also achieved (TOF=4500 h⁻¹).     

Ultrasonic wave aided selective epoxidation of mixed styrene and α-pinene with air over nanosized Co3O4

Catalytic selective epoxidation of mixed biolefins with air over nanosized Co₃O₄ catalyst under mild ultrasonic conditions has been first reported. When the styrene/α-pinene molar ratio was 1:5, the highest conversions were, respectively, reached 81.8 mol% for styrene and 76.1 mol% for α-pinene, with the epoxidation selectivity of 84.1% (styrene oxide) and 94.6% (α-pinene oxide), notably higher than those of the conventional reactions under magnetic stirring. An intermolecular electron-transfer phenomenon between conjugated styrene and electron-rich α-pinene was revealed by UV–vis spectra, which was considerably important for the enhancement of reactivities of both olefinic molecules observed experimentally.     

Substantially enhancing enzymatic regioselective acylation of 1-β-d-arabinofuranosylcytosine with vinyl caprylate by using a co-solvent mixture of hexane and pyridine

Novozym 435-catalyzed regioselective acylation of 1-β-d-arabinofuranosylcytosine (ara-C) with vinyl caprylate for the preparation of its 5′-O-acyl derivative has been performed in six co-solvent mixtures and three pure polar solvents for the first time. Novozym 435 displayed low activity towards 1-β-d-arabinofuranosylcytosine in pure polar solvents, although those solvents can dissolve the nucleosides well. When a hexane–pyridine co-solvent system was adopted, both the initial rate and the substrate conversion were enhanced markedly. The most suitable co-solvent, initial water activity, reaction temperature and the molar ratio of vinyl caprylate to ara-C were hexane/pyridine (28/72, v/v), 0.03, 40 °C and 15, respectively. Under these conditions, the initial rate, the substrate conversion and the regioselectivity were as high as 99.0 mmol h⁻¹, 98% and >99%, respectively. The product of the Novozym 435-catalyzed reaction was characterized by ¹³C NMR and confirmed to be 5′-O-octanoyl 1-β-d-arabinofuranosylcytosine.     

β-MnO2 nanowires: A novel ozonation catalyst for water treatment

Using Mn(NO₃)₂ and ozone as raw materials, β-MnO₂ nanowires with diameters of about 6–12 nm, lengths of 2–5 μm and surface area of 73.54 m² g⁻¹ were synthesized by a simple hydrothermal process. The influences of synthesis conditions such as hydrothermal temperature, reaction time and ozone were investigated, and the growth process of β-MnO₂ nanowires was discussed. The catalytic properties of β-MnO₂ nanowires for the degradation of phenol were evaluated. β-MnO₂ nanowires revealed good separability and remarkable catalysis for the degradation of phenol.     

Bis(4′-phenyl-2,2′:6′,2″-terpyridine)ruthenium(II): Holding the {Ru(tpy)2} embraces at bay

The solid state structure of [Ru(Phtpy)₂][PF₆]₂ · 4MeCN has been determined (Phtpy = 4′-phenyl-2,2′:6′,2″-terpyridine); [Ru(Phtpy)₂]²⁺ cations pack into sheets by virtue of {M(tpy)₂}₂ embraces, and the MeCN solvent molecules are involved in NH–C interactions which prevent the efficient packing of adjacent sheets. Comparisons with related structures lead to some generalizations about packing motifs in salts containing [M(Phtpy)₂]²⁺ or [M(pytpy)₂]²⁺ cations (pytpy = 4′-pyridyl-2,2′:6′,2″-terpyridine).     

Wet 2,4,6-trichloro[1,3,5]triazine (TCT) an efficient catalyst for synthesis of -bis(substituted-benzylidene) cycloalkanones under solvent-free conditions

An array of aromatic aldehydes undergo crossed aldol condensation with ketones in the presence of catalytic amounts of wet-TCT under solvent-free conditions to afford the corresponding α,α^′-bis(substituted-benzylidene) cycloalkanones in excellent yields. Contrary to the existing methods, which use classical Lewis acids a new catalyst (TCT) is employed. This method is also general with respect to all types of aromatic aldehydes and is an eco friendly procedure.     

Preparation and characteristics of β-chitin and poly(vinyl alcohol) blend

Mechanical properties of blend films of β-chitin and poly(vinyl alcohol) (PVA) in dry and wet states were improved compared to those of homopolymers. Fourier transformed infra-red (FTi.r.) spectra of the blend showed the transition of hydroxyl and carbonyl stretching bands upon blending. The subtraction infra-red spectra of blend 70/30 indicated that the blend showed an intermolecular interaction and the reduction of crystallinity compared with those of pure β-chitin. Wide angle X-ray diffraction (WAXD) patterns of the blend also exhibited the loss of crystallinity of β-chitin and PVA upon blending. The blends, however, showed a mixed-crystal structure. Dielectric analysis of the blend showed the transition of α and β relaxation peaks of β-chitin upon blending, appeared at 182° and 97°, respectively. For blends, the temperature of the maximum loss (T_max) of β-chitin appeared at around 182° shifted to a lower temperature region. Differential scanning calorimetric analysis of the blend also showed the transition of melting endotherms of the blend. Transmission electron microscope (TEM) studies of blends using ruthenium tetraoxide as a staining agent were examined to reveal the micro-structure and miscibility of the blends. The TEM micrograph of blend 70/30 shows some microseparations, but it is still believed to be miscible in the blends.     

Ditopic, flexible hydrazone-based building blocks with pendant 2,2′:6′,2′′-terpyridine metal-binding domains

The synthesis and characterization of three new bis(2,2′:6′,2′-terpyridine) (tpy) ligands containing different hydrazone spacers between the metal-binding domains are described. Treatment of 1,4-benzenedicarbaldehyde bis(2,2′:6′,2′′-terpyridin-4′-ylhydrazone) (1) with [(tpy)RuCl₃] in the presence of N-ethylmorpholine results in the formation of [(tpy)Ru(μ-1)Ru(tpy)]⁴⁺. Single crystal X-ray diffraction data for [(tpy)Ru(μ-1)Ru(tpy)][PF₆]₄·8MeCN confirm the ability of the hydrazone-based ligand to bridge two ruthenium(II) centres, providing proof-of-principle for the application of this class of flexible ligand in the design of coordination polymers.     

Selective oxidation of propane and ethane on diluted Mo–V–Nb–Te mixed-oxide catalysts

Te-free and Te-containing Mo–V–Nb mixed oxide catalysts were diluted with several metal oxides (SiO₂, γ-Al₂O₃, α-Al₂O₃, Nb₂O₅, or ZrO₂), characterized, and tested in the oxidation of ethane and propane. Bulk and diluted Mo–V–Nb–Te catalysts exhibited high selectivity to ethylene (up to 96%) at ethane conversions <10%, whereas the corresponding Te-free catalysts exhibited lower selectivity to ethylene. The selectivity to ethylene decreased with the ethane conversion, with this effect depending strongly on the diluter and the catalyst composition. For propane oxidation, the presence of diluter exerted a negative effect on catalytic performance (decreasing the formation of acrylic acid), and α-Al₂O₃ can be considered only a relatively efficient diluter. The higher or lower interaction between diluter and active-phase precursors, promoting or hindering an unfavorable formation of the active and selective crystalline phase [i.e., Te₂M₂₀O₅₇ (M = Mo, V, and Nb)], determines the catalytic performance of these materials.     

Enantioselective hydrogenation of α-ketoesters using cinchona modified platinum catalysts and related systems: A review

The state of the art for the heterogeneous enantioselective hydrogenation of α-ketoesters using cinchona modified Pt catalysts and related systems is reviewed. The effect of the following elements of the catalytic system are well known: Catalyst. Supported Pt catalysts with relatively low dispersion (particle diameter >2 nm) are preferred for the hydrogenation of α-ketoacid derivatives, Pd catalysts for functionalized olefins. Most support materials are suitable. Substrate. The reacting function is preferentially a ketone or a C=C bond, a carbonyl group in a-position is necessary for good optical yields. Modifier. The minimal requirements for an efficient modifier for the hydrogenation of α-ketoesters is the presence of a basic nitrogen atom close to one or more stereogenic centers and connected to an extended aromatic system (preferentially quinolyl or naphthyl). The presence of an alcohol or ether in β-position to the basic nitrogen often gives better enantioselectivities. Solvent. Solvents with adielectric constant between 2 and 10 give best selectivities for a-ketoesters with best e.e.'s in acetic acid. For the hydrogenation of substrates with a free acid function aqueous polar solvents are preferred. The highest optical yields for the different substrate types: 95% e.e. for α-ketoesters, 85% for a-ketoacids and 70% for α,)-unsaturated acids. Practical problems for the use of the catalytic system are low e.e.'s at the start of the reaction, the instability of the modifier and some side reactions as well as the purity of the ethyl pyruvate. Mechanistic investigations have established interactions between substrate and modifier in solution and adsorption of the ethyl pyruvate and cinchonidine on the catalyst. The dependence of rate and e.e. on catalyst, cinchonidine, ethyl pyruvate and hydrogen concentration has been established for ethyl pyruvate hydrogenation using Pt/Al₂O₃-cinchona. A Langmuir-Hinshelwood scheme is well suited for explaining the observed kinetic results. Based on the kinetic results, the effect of modifier and substrate structure, and molecular modeling studies, the following mechanistic model has been developed: On the unmodified catalyst, the a-ketoester and hydrogen are reversibly adsorbed and the addition of the first hydrogen atom is rate determining. A modified active site is formed by adsorption of one cinchona molecule. It is postulated that a protonated adsorbed modifier interacts with the α-ketoester and forms a stabilized half hydrogenated intermediate. The rate determining step for the preferred enantiomer is the addition of the second hydrogen. The rate acceleration and the enantiodiscrimination is therefore due to the preferential stabilization of one of the two diastereomeric intermediates. Alternative mechanisms are discussed but considered to be less satisfying.     

A Comparison of Oxygen-vacancy Effect on Activity Behaviors of Carbon Dioxide and Steam Reforming of Methane over Supported Nickel Catalysts

Partial oxidative steaming reforming of methanol (POSRM) to produce hydrogen selectively for polymer electrolyte membrane fuel cell (PEMFC) powering vehicles was studied over Cu–ZnO/samaria-doped ceria (SDC) catalyst. Compared with Cu–ZnO/α-Al₂O₃ and Cu–ZnO/γ-Al₂O₃ catalysts, the Cu–ZnO/SDC catalyst exhibited higher activity for CH₃OH conversion and higher selectivity for H₂ production in the POSRM reaction. The higher catalytic performance of Cu–ZnO/SDC appears attributable to the support effect of SDC. Effects of reaction temperature, O₂/CH₃OH and H₂O/CH₃OH molar ratios on the catalytic performance of Cu–ZnO/SDC were investigated. It has been found that the partial-oxidation nature of the POSRM reaction is increased when O₂/CH₃OH ratio is increased, and the combustion of methanol and H₂ would occur insignificantly in the POSRM over the Cu–ZnO/SDC catalyst. A higher concentration of steam is beneficial to suppress CO formation over the Cu–ZnO/SDC catalyst. Under the experimental conditions of the present work, the O₂/CH₃OH and H₂O/CH₃OH molar ratios should be about 0.02 and 1.0–2.0, respectively, in order for Cu–ZnO/SDC to achieve an optimum catalytic performance.     

Effect of CO2 in the feed stream on the deactivation of Co/γ-Al2O3 Fischer–Tropsch catalyst

The influence of CO₂ on the deactivation of Co/γ-Al₂O₃ Fischer–Tropsch (FT) catalyst in CO hydrogenation has been investigated. The presence of CO₂ in the feed stream reveals a negative effect on catalyst stability and in the formation of heavy hydrocarbons. The CO₂ acts as a mild oxidizing agent on cobalt metal during Fischer–Tropsch synthesis. During FT synthesis on Co/γ-Al₂O₃ of 70 h, the CO conversion and C₅₊ selectivity in the presence of CO₂ decreased more significantly than in the absence of CO₂. CO₂ is found to be responsible for the partial oxidation of surface cobalt metal at FT synthesis environment with the co-existence of generated water.     

Synthesis of onion-like mesoporous silica from sodium silicate in the presence of α,ω-diamine surfactant

Mesoporous silicas with vesicular and onion-like morphologies were assembled through hydrogen-bonding pathway from sodium silicate as silica source and electrically neutral α,ω-diamine, Jeffamine D2000 surfactant (H₂NCH(CH₃)CH₂[OCH₂CH(CH₃)]₃₃NH₂) as template in aqueous media at different synthesis temperatures (25, 60 and 100 °C). Assembling the material at 100 °C afforded onion-like core shell mesoporous silica, while at relatively lower temperature, e.g. 25 and 60 °C, multilamellar vesicles were obtained. Mesoporous silica with onion-like morphology was also obtained by a two-step synthesis involving an aging period of 20 h at room temperature followed by a hydrothermal stage (1–12 h) at 100 °C. The heavily cross-linked (Q⁴/Q³ ratio of 4.43) onion-like mesophase silica exhibited high hydrothermal stability. The BET surface area, pore volume and KJS (Kruk-Jaroniec-Sayari) pore diameter of the onion-like mesoporous silica were found to be 464 m² g⁻¹, 1.16 m³ g⁻¹ and 7.2 nm, respectively.