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Applied Catalysis A, General (v.429-430, #)
Hydroisomerization of saturated hydrocarbons with novel MCM-41 immobilized Re(V) complex catalysts by Gopal S. Mishra; Anil Kumar (pp. 1-8).
Display Omitted► Single site anchored tricarbonyl Re(V) complexes into modified MCM-41 as supported hybrid catalysts. ► Application in n-alkanes hydro-reformation. ► High TONs from 2100 to 3300 with selectivity 85% for n-hexane and 91% for n-heptane. ► Thermally stable (up to 200°C) and recyclable.The hetero-functionalized phosphines HPN2, H2PNO and HPN-Pip containing tricarbonyl Re(V) complexes, i.e. [Re(CO)3(κ3-PN2)] (I), [Re(CO)3Br(κ2-H2PNO)] (II) and [Re(CO)3Br(κ2-HPN-Pip)] (III) were covalently bonded to modified and MCM-41 to obtain novel supported hybrid catalysts. Remarkable high catalytic effects were observed with these catalysts in the hydroisomerization of n-alkanes at low temperature. The catalystII/MCM-41 provided the highest TONs 3.32×103 with 37% yield for n-hexane and 3.18×103 with 30% yield for n-heptane. Under optimized condition, good selectivities for n-hexane (85%) and for n-heptane (91%) were obtained. The TGA was used to evaluate the stability of catalysts and reusable for several cycles. A possible carbenium-based mechanism been used to explain product formation.
Keywords: Modified MCM-41; Re-complex; Immobilization; Hydroisomerization; n; -Alkane
Study on the influence of channel structure properties in the dehydration of glycerol to acrolein over H-zeolite catalysts by Yunlei Gu; Naiyun Cui; Qingjun Yu; Chunyi Li; Qiukai Cui (pp. 9-16).
Display Omitted► H-zeolites with smaller channels favored glycerol dehydration to acrolein. ► HZSM-11 exhibited superior catalytic performance than HZSM-5. ► The introduction of carrier gas could improve catalytic performance of H-zeolites. ► Coke was initially deposited at channel intersections of H-zeolites. ► External surface of H-zeolites supplied room for coke deposition during reaction.Systematic studies have been conducted over several selected H-zeolites, namely HZSM-5, H-Beta, HY, nano HZSM-5, HZSM-11 and nano HZSM-11, aimed to investigate influence of the channel structure on catalytic performance for gas phase dehydration of glycerol to acrolein. Compared to H-Beta and HY, improved catalytic performance was discovered over HZSM-5, which demonstrated that H-zeolites with smaller channels, the ones marginally larger than the molecular diameter of glycerol, were preferential for the reaction. HZSM-11, with lower channel complexity, was more likely to obtain superior catalytic performance due to enhanced diffusion. Nano HZSM-11 (300–500nm) exhibited excellent catalytic performance with 81.6mol% glycerol conversion and 74.9mol% acrolein selectivity at GHSV as high as 873h−1 (TOS=8h). BET and TEM experiment results indicated that coke was initially deposited at channel intersections of H-zeolites, and when the channel blockage came up to a certain extent, there arrived the onset of coke deposition on the external surface.
Keywords: Glycerol; Acrolein; Dehydration; Channel structure property; HZSM-11
A highly active and chemoselective assembled Pt/C(Fe) catalyst for hydrogenation of o-chloronitrobenzene by Xiangsheng Xu; Xiaoqing Li; Huizi Gu; Zhongbin Huang; Xinhuan Yan (pp. 17-23).
Display Omitted► A novel absorption protocol for synthesis of assembled Pt nanocomposite catalyst has been established. ► The hydrogenation TOF was 78s−1 when the selectivity of 99.5% to o-CAN was obtained at a complete conversion. ► The catalyst exhibited remarkable activity for five consecutive recycles. ► The absorption protocol and the modification of AC by Fe both play decisive roles on the catalytic properties of the catalyst.A highly active and chemoselective assembled Pt/C(Fe) catalyst was prepared by an adsorption protocol. Pt nanoparticles (∼2.4nm) in a Pt colloid solution obtained from the decomposition of Pt2(dba)3 (dba=dibenzalacetone) were utilized as Pt precursors and adsorbed by Fe-modified active carbon (AC). The adsorption method makes Pt nanoparticles enriched on the surface of the catalyst, and the enrichment was further enhanced due to the presence of Fe in the active carbon, leading to the formation of more active sites exposed on the surface. XPS analysis revealed that a much more electron-deficient state of the Pt nanoparticles was existed due to the electron transfer between Pt nanoparticles and Fe2O3. This catalyst was used for the liquid phase hydrogenation of o-chloronitrobenzene ( o-CNB) to o-chloroaniline ( o-CAN) with the highest turnover frequencies (TOF) of 78 (mol o-CNB/(molPts)) and a selectivity of 99.5% at complete conversion of o-CNB. The catalyst was also recycled for five times and the total turnover number was more than 625,000 (mol o-CNB/molPt).
Keywords: Pt nanoparticles; o; -Chloronitrobenzene; Liquid phase hydrogenation; Adsorption
Microwave calcination of Cu/Mg/Al hydrotalcite catalyst precursor by H.E. Cross; G. Parkes; D.R. Brown (pp. 24-30).
Display Omitted► Catalyst properties tuned using microwave calcination under feedback-control. ► Microwave calcination: power controlled by feedback from sample temperature. ► Enhanced basic and catalytic properties of oxides generated by microwave calcination.A copper-substituted hydrotalcite (Cu1.4Mg4.4Al2.2(CO3)1.1(OH)16) has been subjected to calcination under feedback-controlled microwave heating, in which microwave power is continuously modulated to generate a defined sample temperature programme or constant sample temperature. The results show that microwave calcination results in enhanced crystallinity of the resultant oxides and spinel phase formed at high temperature, compared to conventional calcination. In addition, an additional phase, Cu2MgO3, is detected following microwave calcination, at a bulk temperature very much lower than previously reported for copper-containing hydrotalcite. The concentrations and strengths of surface basic sites are significantly higher for materials calcined using microwaves than using conventional heating. Catalytic activities in the base-catalysed transesterification of glyceryl tributyrate with methanol are also higher. We suggest that microwave calcination under feedback-control, while allowing control of material bulk temperature during calcination and preventing major temperature excursions, may allow quite large but highly localised temperature variation, for instance as water is released during dehydroxylation, which are beneficial in developing surface defects and surface basicity.
Keywords: Catalyst; Catalysis; Calcination; Microwave; Feedback-control; Hydrotalcite; Layered double hydroxide; Mixed metal oxides; Calorimetry; Solid base
Photocatalytic reduction of CO2 over noble metal-loaded and nitrogen-doped mesoporous TiO2 by Xiukai Li; Zongjin Zhuang; Wei Li; Huiqi Pan (pp. 31-38).
Display Omitted► Nitrogen-doped mesoporous TiO2 samples are active for CO2 photoreduction. ► Molecularly chemisorbed nitrogen species contribute to the visible light sensitivity. ► Noble metals loading generally improved the photocatalytic activity. ► Pt showed the best promotion effect.Nitrogen-doped mesoporous TiO2 photocatalysts were developed for CO2 photoreduction by water in gas phase. The effects of nitrogen doping and noble metal loading were investigated in detail. The characteristics of samples were investigated by techniques, such as XRD, FT-IR, TEM, XPS, nitrogen adsorption–desorption, and UV–vis diffuse reflectance spectroscopy. The loading of noble metals (i.e., Pt, Au, and Ag) generally improved the photocatalytic activity, and the efficiency follows the order: Pt>Au>Ag. It was found that the loading of Pt also promoted the transformation of catalyst associated carbon residues to methane. With unique properties, such as the mesoporous structure, light absorption, and the electron transfer character, the nitrogen-doped mesoporous TiO2 samples showed good activity for CO2 photoreduction to methane under visible light. The optimum loading amount of Pt was 0.2wt.%, and the optimum doping amount of N was 0.84% on the basis of the lattice oxygen atoms. Aspects such as the origination of visible light sensitivity in terms of nitrogen doping, the effect of noble metal loading, and the reaction mechanism were also discussed.
Keywords: Mesoporous TiO; 2; CO; 2; photoreduction; Nitrogen doping; Noble metal; Visible light
The promotional effect of Ni on bimetallic PtNi/C catalysts for glycerol electrooxidation by Seonhwa Lee; Hyung Ju Kim; Sung Mook Choi; Min Ho Seo; Won Bae Kim (pp. 39-47).
Display Omitted► Addition of Ni with a Pt catalyst yields a bimetallic PtNi catalyst. ► The catalytic activity is influenced by the structural and electronic modification. ► The oxidation activity for glycerol is highly improved over the Pt2Ni1/C.The electrocatalytic oxidation of glycerol was studied using carbon-supported 20wt.% PtNi (PtNi/C) catalysts, which were prepared with different Pt:Ni atomic ratios from 3:1 to 1:1 using a colloidal method combined with a freeze-drying procedure. The bimetallic PtNi/C catalysts were characterized by various physicochemical analyses, including X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) measurements indicated that the addition of Ni with a Pt catalyst significantly improved the electrocatalytic activity for glycerol electrooxidation. Among the tested catalysts, the Pt2Ni1/C catalyst had approximately 61% higher mass activity than the Pt/C catalyst. Structural modification via lattice parameter change and electronic modification in the unfilled d band states for Pt atoms may kinetically facilitate the electrooxidation of glycerol with an increased exchange current density over the PtNi/C catalysts.
Keywords: PtNi catalysts; Electrocatalytic oxidations; Glycerol; Fuel cells; Biomass
Catalytic conversion of syngas to mixed alcohols over Zn-Mn promoted Cu-Fe based catalyst by Yongwu Lu; Fei Yu; Jin Hu; Jian Liu (pp. 48-58).
.Display Omitted► Zn-Mn promoted Cu-Fe based catalyst had high catalytic activity and selectivity. ► The state of proposed catalyst was firstly identified to determine the active sites. ► Cu (111) was the active site for mixed alcohols synthesis. ► Fe2C (101) was the active site for olefin and paraffin synthesis. ► The reaction mechanism was proposed for mixed alcohols synthesis from this catalyst.Zn-Mn promoted Cu-Fe based catalyst was synthesized by the co-precipitation method. Mixed alcohols synthesis from syngas was studied in a half-inch tubular reactor system after the catalyst was reduced. Zn-Mn promoted Cu-Fe based catalyst was characterized by SEM-EDS, TEM, XRD, and XPS. The liquid phase products (alcohol phase and hydrocarbon phase) were analyzed by GC–MS and the gas phase products were analyzed by GC. The results showed that Zn-Mn promoted Cu-Fe based catalyst had high catalytic activity and high alcohol selectivity. The maximal CO conversion rate was 72%, and the yield of alcohol and hydrocarbons were also very high. Cu (111) was the active site for mixed alcohols synthesis, Fe2C (101) was the active site for olefin and paraffin synthesis. The reaction mechanism of mixed alcohols synthesis from syngas over Zn-Mn promoted Cu-Fe based catalyst was proposed. Zn-Mn promoted Cu-Fe based catalyst can be regarded as a potential candidate for catalytic conversion of biomass-derived syngas to mixed alcohols.
Keywords: Mixed alcohols synthesis; Syngas; Zn-Mn promoted Cu-Fe based catalyst; Co-precipitation
Effect of lanthanide promoters on zirconia-based isosynthesis catalysts prepared by surfactant-assisted coprecipitation by Nicholas E. McGuire; Narasimharao Kondamudi; Lucia M. Petkovic; Daniel M. Ginosar (pp. 59-66).
Display Omitted► Surfactant-assisted coprecipitation yields high surface area zirconias for isosynthesis. ► Lanthanide promoters reduce acidity of high surface area zirconia. ► Promotion of zirconia with ceria reduces yields of heavy hydrocarbons during isosynthesis.This work examines the characteristics and performance of lanthanide-promoted zirconia catalysts for synthesis of isobutene from syngas (isosynthesis). Several mixed-metal-oxide catalysts employing a range of modifier species are considered. The catalysts examined include lanthana-promoted zirconia (La-ZrO2), ceria-promoted zirconia (Ce-ZrO2) and lanthana–ceria–zirconia (LaCe–ZrO2). The addition of metal promoters to zirconia is known to have an effect on the physicochemical properties of the catalyst which in turn affects catalytic performance for isosynthesis. In this work, catalyst properties are characterized via a number of diagnostic techniques including N2 physisorption, X-ray diffraction, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis following pyridine chemisorption. Isosynthesis activity is evaluated in a packed bed reactor configuration and the results are analyzed in terms of the physicochemical characteristics of the catalysts. Catalyst activity test results indicate that such modifiers have a strong effect on carbon monoxide conversion and selectivity to isobutene.
Keywords: Isosynthesis; Isobutene; Syngas
Ionic liquids grafted on carbon nanotubes as highly efficient heterogeneous catalysts for the synthesis of cyclic carbonates by Lina Han; Haiqing Li; Soo-Jin Choi; Moon-Seok Park; Seon-Myong Lee; Yu-Jin Kim; Dae-Won Park (pp. 67-72).
Display Omitted► Imidazolium-based ionic liquids were grafted onto carbon nanotube nanohybrids. ► They showed enhanced catalytic performance in the cycloaddition reaction of CO2 and epoxides. ► Tunable catalytic activity can be achieved depending on the molecular structure of the immobilized ionic liquids. ► Reaction conditions have significant effects on the catalytic performance of the heterogeneous catalysts.A variety of multi-walled carbon nanotubes grafted with immidazolium-based ionic liquids (CNT-ILs) were synthesized and utilized as highly efficient heterogeneous catalysts for the production of cyclic carbonates via cylcoaddition reactions of epoxides and CO2. In comparison with conventional heterogeneous catalysts that employ porous silica and polymer supports, CNT-ILs exhibited significantly enhanced catalytic reactivity towards the cycloaddition reactions. The effects of the IL molecular structure (alkyl chain length and counter anions) and the reaction parameters (temperature, CO2 pressure, and time) on the catalytic performance of the corresponding heterogeneous catalysts were also systematically investigated.
Keywords: Carbon dioxide; Carbon nanotube; Cyclic carbonate; Cycloaddition reaction; Heterogeneous catalysts; Ionic liquids
A highly efficient and reusable heterogeneous catalyst for the one-pot synthesis of tetrasubstituted imidazoles by Ali Mohammadi; Hossein Keshvari; Reza Sandaroos; Behrooz Maleki; Hamed Rouhi; Hassanali Moradi; Zeinalabedin Sepehr; Saman Damavandi (pp. 73-78).
Display Omitted► Poly(AMPS-co-AA) was synthesized according to the literature. ► Poly(AMPS-co-AA) was used as a catalyst for synthesis of tetrasubstituted imidazoles. ► This polymer is an efficient and reusable catalyst for this process.An efficient synthesis of 1,2,4,5-tetrasubstituted imidazoles is achieved by four component cyclocondensation of benzil or benzoin, aniline or benzyl amine, aldehyde and ammonium acetate by using novel polymeric catalyst [poly(AMPS-co-AA)] under solvent-free conditions. The key advantages of this process are high yields, shorter reaction times, easy work-up, purification of products by non-chromatographic method and the reusability of the catalyst.
Keywords: 1,2,4,5-Tetrasubstituted imidazoles; Solvent-free synthesis; Multicomponent reaction; Poly(AMPS-co-AA); Heterogeneous catalysts
Kinetics of esterification of acetic acid with 1-octanol in the presence of Amberlyst 36 by Sema Akyalçın; Mehmet Rıza Altıokka (pp. 79-84).
Display Omitted► 1-Octanol and acetic acid reaction catalyzed by Amberlyst 36 was investigated. ► Kinetic model was developed. ► Reaction follows the Eley–Rideal mechanism.Kinetic data on the esterification of acetic acid with 1-octanol were obtained from both uncatalyzed and heterogeneously catalyzed reactions using a stirred batch reactor in toluene. The equilibrium constant, Kc, which is independent of temperature ranging from 333 to 358K, was found to be 60.7. The uncatalyzed reaction was proved to be a second-order reversible reaction. In the presence of Amberlyst 36, the reaction was found to follow the Eley–Rideal mechanism, and the surface reaction is a rate-limiting step. From this model, the reaction rate can be given by the expression:−rA=k(m/V)(CACB−(CECW/KC))(1+KACA+KWCW).The temperature dependencies of the constants appearing in the rate expressions were also calculated to be:k(L2/g dry resin⋅mol⋅min)=exp1.07−2991T,KA(L/mol)=exp12954T−38.28,andKW(L/mol)=exp25427T−76.15,where T is the absolute temperature in Kelvin.
Keywords: Esterification; Reaction kinetics; n; -Octylacetate; Amberlyst 36; Eley–Rideal mechanism
Preparation of amine-immobilized solid base catalysts by plasma polymerization of 1,2-diaminocyclohexane by Sun-Jung Song; Kyoung Woon Jung; Myung Duck Cho; Eun Ju Yang; Hye Jeong Sim; Mi-Young Kim; Hoi-Gu Jang; Gon Seo; Dong Lyun Cho (pp. 85-91).
Display Omitted► A novel approach for the preparation of solid base catalyst was investigated. ► Amine incorporated solid base catalyst was prepared by plasma deposition of DACH. ► Amine incorporated solid base catalyst showed good base catalytic activity. ► They can be repeated use for 3 times without loss of activity.Thin films were deposited onto silica–alumina powders by plasma polymerization of 1,2-diaminocyclohexane to prepare amine-immobilized solid base catalysts. The existence of amine moieties in the films was confirmed by solid-state13C NMR, FT/IR, and XPS analyses. The silica–alumina powders deposited with the films showed strong base catalytic activity when evaluated based on the adsorption/desorption pattern of acidic gases (NO2 and CO2) and the conversion of benzaldehyde in Knoevenagel condensation reaction between benzaldehyde and ethylcynoacetate. Adsorbed acidic gases still remained even at 400°C due to strong chemisorptions. When the plasma polymerization was carried out by a two-step process, the conversion was as high as 91.2% and adhesion of the films could be improved. The conversion was 82.0% even after the repeated use for 3 times when the films were deposited by the two-step process.
Keywords: Plasma polymerization; 1,2-Diaminocyclohexane; Amine-immobilized; Solid base catalysts
Curved nanostructures of unsupported and Al2O3-supported MoS2 catalysts: Synthesis and HDS catalytic properties by Anabela Nogueira; Raja Znaiguia; Denis Uzio; Pavel Afanasiev; Gilles Berhault (pp. 92-105).
Display Omitted► Use of (NH4)2Mo2S12·2H2O leads to fullerene-like MoS2 after N2 treatment at 750°C. ► Formation of fullerene-like MoS2 leads to the weakening of the Mo–S bond strength. ► Bending MoS2 slabs modifies HDS properties creating active sites on curved layers. ► Cobalt promotion of fullerene-like MoS2 possible. ► Suppression of the olefin hydrogenation if not activated by H2S.The active phase of hydrodesulfurization (HDS) catalysts is usually composed of MoS2 slabs promoted by cobalt and/or nickel. Because of the anisotropic structure of molybdenum disulfide, the active sites are believed to be present only on the edges of the slabs, exhibiting dangling bonds. However, slabs of MoS2-based industrial catalysts often exhibit disordered bent morphology which might generate strain effects creating new active sites. In order to evaluate a possible effect of bending MoS2 slabs on HDS catalytic properties, synthesis of well-defined curved morphologies was carried out in the present study. Two different strategies were evaluated herein: acidification of ammonium tetrathiomolybdate, (NH4)2MoS4 (ATM) in the presence of polyethyleneglycol or decomposition of ammonium thiodimolybdate, (NH4)2Mo2S12 (ATDM). The resulting amorphous sulfides, deposited or not on γ-Al2O3, were then post-treated at 400°C or 750°C under N2 or H2 in the presence or not of H2S. Cobalt promotion was also attempted on the final post-treated solids. The results show that the nature of the sulfur-containing precursor strongly influences the final morphology. Using ATM, the as-obtained nanospheres are formed of bundles of slabs while using ATDM, fullerenic-like MoS2 particles are obtained after post-treatment at 750°C. These fullerenic-like particles exhibit non constant radius of curvature with flat regions separated by strongly localized distorted zones suggesting the formation of defect sites on basal planes. The possibility of promoting these systems by Co sustains the presence of such surface sites. XPS and TPR results also show a marked weakening of the metal–sulfur bond strength when compared to flat crystals. Finally, catalytic activities determined for the HDS of thiophene and the simultaneous hydrogenation (HYD) of toluene and isomerization of cyclohexane are rather noticeable despite the absence of conventional edge sites. Bending MoS2 slabs therefore seems to lead to the creation of new active sites on basal planes with original catalytic properties.
Keywords: Hydrodesulfurization; MoS; 2; Bending; Hydrogenation; Fullerene-like
Erratum to “Reactivity characteristics of Pt-encapsulated zeolite catalysts for hydrogenation and hydrodesulphurization” [Appl. Catal. A 415–416C (2012) 70–79]
by Song Chen; Jinwen Chen; Rafal Gieleciak; Craig Fairbridge (pp. 106-106).