Applied Catalysis A, General (v.503, #C)
Editorial Board (IFC).
Catalytic cracking of bio-oils improved by the formation of mesopores by means of Y zeolite desilication by Juan Rafael García; Melisa Bertero; Marisa Falco; Ulises Sedran (1-8).
Y zeolite was desilicated by means of alkaline treatments (NaOH 0.05, 0.10 and 0.20 M) during 15 min to produce varying mesoporosity over it. Catalysts were made with a SiO2 matrix and a binder. Pine sawdust bio-oil was produced by pyrolysis and immediately upgraded, without intermediate condensation, on a downstream bed of the compound catalysts. The experiments were produced in a fixed bed reactor at 550 °C using different catalyst to reactants relationships. The desilicated zeolites were more effective than the parent zeolite to deoxygenate bio-oil and produce more hydrocarbons, with higher selectivity to olefins (more than 35 wt.%) and lower selectivity to aromatics (less than 60 wt.%) in gasoline. The selectivity to C4− and gasoline olefins increased if the mesoporosity was higher, and the coke formed was less condensed. These observations were the result of improvements in the diffusion of bulky molecules in bio-oils, such as phenolic ethers, increasing their conversion to hydrocarbons.
Keywords: Bio-oils; Fuels; Desilication; Y zeolite; Mesopores;
Synthesis of new metalloporphyrin derivatives from [5,10,15,20-tetrakis (pentafluorophenyl)porphyrin] and 4-mercaptobenzoic acid for homogeneous and heterogeneous catalysis by Kelly A.D. de F. Castro; Mário M.Q. Simões; Maria da Graça P.M.S. Neves; José A.S. Cavaleiro; Ronny R. Ribeiro; Fernando Wypych; Shirley Nakagaki (9-19).
Synthetic metalloporphyrins are catalysts that can efficiently insert oxygen and other atoms such as nitrogen and sulfur in hydrocarbons and in a wide variety of other organic compounds. This work reports on a synthetic strategy to prepare new metalloporphyrins via structural modification of [5,10,15,20-tetrakis (pentafluorophenyl)porphyrin], or [H2(TPFPP)], with 4-mercaptobenzoic acid; it also describes their characterization and catalytic activity. The substituent groups present in the structure of the resulting porphyrins furnished structured solids, which could potentially serve as catalysts in heterogeneous medium. Investigation of the catalytic activity of the new derivatives in the oxidation of (Z)-cyclooctene, cyclohexane, and heptane, under homogeneous conditions, and in the oxidation of (Z)-cyclooctene, in heterogeneous medium, proved that the new metalloporphyrins constituted excellent catalysts for (Z)-cyclooctene epoxidation. As for alkane oxidation, they selectively gave the corresponding alcohol in good yields.
Keywords: Porphyrin; 4-Mercaptobenzoic acid; Nucleophilic substitution; Homogeneous and heterogeneous catalysis; Oxidation;
A pyridyl-triazole ligand for ruthenium and iridium catalyzed C＝C and C＝O hydrogenations in water/organic solvent biphasic systems by Stefano Paganelli; Md. Mahbubul Alam; Valentina Beghetto; Alberto Scrivanti; Emanuele Amadio; Matteo Bertoldini; Ugo Matteoli (20-25).
The water soluble pyridyl-triazole ligand sodium 2-(1-((pyridin-2-yl)methyl)-1H-1,2,3-triazol-4-yl)ethyl sulfate (Na1) has been successfully employed in combination with ruthenium and iridium for catalytic hydrogenation of C＝C and C＝O double bonds in water/toluene biphasic systems. Reaction of the ligand with [RuCl2(η6-p-cymene)]2 affords the new water soluble complex [RuCl(η6-p-cymene)(1)] (2) which has been found to be catalytically active in the water/organic solvent biphasic hydrogenation using styrene and 2-cyclohexen-1-one as model substrates. Very conveniently, the iridium based catalytic system is prepared by simply stirring in water [Ir(η4-COD)Cl]2 with Na1 (Ir:Na1 molar ratio = 1:4), the resulting solution is catalytically active and appears more efficient than 2. With both the Ru- and Ir-based systems the catalytically active aqueous phases can be used at least three times without loss of activity.
Keywords: Ruthenium; Iridium; Catalytic hydrogenation; Biphasic catalysis; Water;
Synthesis, characterization and catalytic properties for olefin polymerization of two new dimeric zirconium(IV) complexes having diamine-bis(phenolate) and chloride ligands by Elwira Bisz; Marzena Białek; Bartosz Zarychta (26-33).
Display OmittedReaction of the zirconium tetrachloride with one equivalent of the sodium salt of the diamine bis (phenolate) ligand, L1H2 (Me2NCH2CH2N-(CH2-2-OH-3,5-tBu-C6H2)2) or L2H2 (Me2NCH2CH2N-(CH2-2-OH-3,5-tBu-C6H2)(CH2-2-OH-C6H4)) in the presence of air led to formation of [Lig1ZrCl]2(μ-O) and [Lig2ZrCl]2(μ-O), respectively. These novel oxo-bridged dinuclear zirconium complexes were characterized by elemental analysis, 1H NMR spectroscopy and by single-crystal X-ray diffraction. Their reactivities in polymerization of ethylene and 1-octene, upon activation with Al(iBu)3/Ph3CB(C6F5)4 and MAO, were examined. It was found that lack of t-Bu substituents on one phenolate ring cause a significant decrease in catalytic activity but leads to polymers with improving properties, i.e., to poly(1-olefin)s with significantly higher stereoregularity and polyethylenes with higher molecular weight. In addition, the interaction of the [Lig1ZrCl]2(μ-O) precursors with MAO and with the Me3Al activator was investigated by 1H NMR spectroscopy giving an insight into the catalyst transformations in the course of the polymerization reaction.
Keywords: Zirconium catalyst; Diamine-bis(phenolate) ligand; Ziegler–Natta polymerization; Poly(1-octene); Polyethylene;
Ni/SiO2 catalyst prepared via Ni-aliphatic amine complexation for dry reforming of methane: Effect of carbon chain number and amine concentration by X.Y. Gao; J. Ashok; S. Widjaja; K. Hidajat; S. Kawi (34-42).
Display OmittedAliphatic amines of different carbon numbers (i.e., carbon number in one linear hydrocarbon chain, N c) and concentrations (C a) were used in the preparation of silicon dioxide (SiO2) supported nickel catalysts by incipient wetness impregnation (IWI) method. The results showed that both the size and the metal-support interaction (MSI) were affected by the carbon chain number and the amine concentration. On one hand, the use of the aliphatic amine with a larger carbon chain number achieved a smaller size and higher dispersion due to the stronger steric hindrance; this smaller size and higher dispersion further enhanced the MSI because of the larger contact area of Ni with the silica support. On the other hand, a higher amine concentration decreases the size and improve the dispersion because of the faster nucleation rate; also when higher concentration of amine was used, more hydrogen bonds were formed between the -NH2 and the silanol group and more electron transfer was found between Ni and the -NH2, leading to a stronger MSI. With a small size, high dispersion and strong MSI, NiSi-OAm showed the most stable catalytic performances (CO2 conversion of 78% and CH4 conversion of 70% within 20 h) with low carbon deposition (1.8 mgC/g cat h) for dry reforming of methane (DRM) reaction.
Keywords: Ni; Aliphatic amine; Carbon chain; –NH2 terminal group; Dry reforming of methane;
Fe and CaO promoted Ni catalyst on gasifier bed material for tar removal from producer gas by Tinku Baidya; Robert J. Cattolica (43-50).
Display OmittedA new Ni-based mixed oxide material (Ni-Fe-CaO) for catalyzing Carbo HSP gasifier bed material was prepared and characterized by XRD, TPR, TEM, and SEM techniques. The catalyst performance for tar removal from a simulated producer gas mixture via steam reforming was tested in a laboratory-scale fixed-bed reactor between 700 and 800 °C, using toluene and ethylene as tar surrogates. Ni–Fe–CaO catalysts had significantly higher activity and deactivation resistance for toluene removal compared to either Ni–Fe or Ni catalysts. Keeping CaO loading similar in the catalysts, the Ni:Fe ratio was varied and the optimum tar conversion and highest CO x selectivity were obtained with ratios of 3:1 and 2:1. The turn over frequency (TOF) on Ni in the Ni–Fe–CaO mixed oxides were higher compared to pure Ni or Ni–CaO combinations and increased with lowering Ni/Fe ratio. High tar removal activity (80% vs 68%) and CO x selectivity (96% vs 98%) at 750 °C were obtained for 1.6% (Ni45Fe15Ca40)/Carbo HSP and 1.6% (Ni40Fe20Ca40)/Carbo HSP compositions, respectively. Deactivation occurred mainly due to sintering of the 1.6% (Ni45Fe15Ca40) composition reducing conversion efficiency by 17% (from 99.7% to 83%) after 48 h in time-on-stream at 800 °C. After regeneration with a O2/H2 sequence, the conversion was reduced from 98% to 80% after 24 h in time-on-stream. Similarly, 1.6% (Ni40Fe20Ca40) composition shows a stable conversion of ∼80% at the end of 50 h, which was much superior compared to the 1% (Ni65Fe35)/Carbo HSP catalyst. The individual role of Fe and CaO in promoting Ni for improving catalytic activity and stability in Ni-Fe-CaO was investigated
Keywords: Gasifier bed material; Producer gas; Steam reforming; Toluene; Tars;
Effects of Cu/Fe ratio on structure and performance of attapulgite supported CuFeCo-based catalyst for mixed alcohols synthesis from syngas by Haijun Guo; Hairong Zhang; Fen Peng; Huijuan Yang; Lian Xiong; Can Wang; Chao Huang; Xinde Chen; Longlong Ma (51-61).
Display OmittedThe effects of Cu/Fe ratio on structure of attapulgite (ATP) supported CuFeCo-based catalysts were detected by N2 physical adsorption/desorption, XRD, H2-TPR, FE-SEM, TEM, XPS etc.. And the effect on the catalytic performance for mixed alcohols synthesis (MAS) from syngas was evaluated with a continuous flow fixed bed reactor as well. The characterization results indicated that the increase of iron addition resulted in the increase of BET surface area and facilitated the dispersion of oxide particles. Increasing iron concentration also facilitated the separation of Cu–Fe alloy phase, the incorporation of Cu and Fe species and the formation and dispersion of CuFe2O4 spinel phase, thus promoting its reduction to generate Cu–FeC x dual active site for C2+ alcohol formation. However, more Fe2O3 was formed and dispersed on/in the catalyst with higher iron concentration and was reduced to generate sole FeC x and Fe3O4 phase during reaction. The coverage of CuFe2O4 phase by Fe2O3 inhibited the mixed alcohols formation. In the MAS reaction, the Cu5.2Fe4.8 catalyst showed the highest selectivity and yield of total alcohol due to the well dispersion of high concentration of Cu-FeC x dual active site, which may be attributed to the optimum Cu–Fe interaction and the intimate contact of Cu–Fe species. In view of the utilization of low-cost nonmetallic mineral resource and the production of clean liquid fuel, the attapulgite clay has a great promise to be used as catalyst support in energy field.
Keywords: Mixed alcohols synthesis; Attapulgite; Syngas; Cu–Fe–Co based catalyst;
Effect of microwave calcination on catalytic properties of Pt/MgAl(Sn)Ox catalyst in cyclohexane dehydrogenation to cyclohexene by Nai-liang Wang; Jian-e Qiu; Zhao-wei Wu; Jian Wu; Kui-yi You; He-an Luo (62-68).
Display OmittedThis paper describes an investigation on catalytic properties of Pt nanoparticles supported on MgAl(Sn)Ox mixed oxide for cyclohexane dehydrogenation to cyclohexene. The MgAl(Sn)Ox supports were synthesized by microwave calcined hydrotalcite-derived precursors, and Pt/MgAl(Sn)Ox catalysts were prepared by an incipient wetness impregnation method. The catalysts were characterized by X-ray diffraction (XRD), hydrogen temperature-programmed reduction (H2-TPR), hydrogen temperature-programmed desorption (H2-TPD), X-Ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The results showed that the microwave calcination changed the interfacial character between Pt and support, and strengthened the interaction between tin and support, and facilitated the high dispersion of Pt nanoparticles presented on the support. These effects resulted in higher activity, stability and cyclohexene selectivity in cyclohexane dehydrogenation to cyclohexene.
Keywords: Cyclohexane; Cyclohexene; Dehydrogenation; Microwave; Pt–Sn;
Sonogashira coupling reaction over supported gold nanoparticles: Influence of support and catalyst synthesis route by Sheetal Sisodiya; L. Reine Wallenberg; Erik Lewin; Ola F. Wendt (69-76).
Display OmittedThis study investigates the impact of supports and synthesis routes on the performance of supported gold nanoparticles in the Sonogashira coupling reaction. The catalysts were synthesized by deposition–precipitation (DP) and incipient wetness impregnation (IMP), employing carriers of different nature (redox: CeO2, TiO2, and non-redox: Al2O3) and were characterized by various physical techniques such as X-ray fluorescence, powder X-ray diffraction, X-ray photoelectron spectroscopy, N2 sorption, and high resolution transmission electron microscopy. It is revealed that gold is present in the metallic state in all of the samples, independent of the nature of the support and the way of synthesis. The DP technique gave catalysts with smaller gold particles (4–14 nm), while the IMP route led to agglomeration due to presence of chlorine and resulted in distinctly larger gold particles (50–100 nm) on the supports. The evaluation of catalysts in the Sonogashira coupling of phenylacetylene and iodobenzene demonstrated that the catalysts’ performance is negligibly dependent on the specific surface area of the catalysts. Synthesis paths, however, greatly affected the catalysts’ activity and selectivity. All the catalysts prepared by DP gave significantly higher conversion of iodobenzene and selectivity to diphenylacetylene (desired hetero-coupled product) than their analogs prepared by IMP. This is shown to be related to the superior dispersion achieved by the DP route with the formation of smaller Au nanoparticle, which are highly active and selective. Thus, the present study explicitly establishes that the choice of proper synthesis method is vital to achieve sufficiently small nanoparticles leading to the best Sonogashira performance. Also, redox active oxide supports lead to a better performance than non-redox carriers. Despite significant leaching, the catalysis is shown to be heterogeneous.
Keywords: Sonogashira coupling; Gold nanoparticles; Support; Synthesis routes;
Sulphated mesoporous La2O3–ZrO2 composite oxide as an efficient and reusable solid acid catalyst for alkenylation of aromatics with phenylacetylene by Zhongkui Zhao; Jinfeng Ran (77-83).
Sulphated mesoporous La2O3–ZrO2 composite oxides (SO4 2−/meso-La2O3–ZrO2) were firstly prepared by a surfactant-assisted co-precipitation/hydrothermal crystallization with subsequent impregnation method (SACPHC-IM). The prepared SO4 2−/meso-La2O3–ZrO2 catalyst was employed as solid acid to catalyze direct alkenylation of p-xylene with phenylacetylene for clean production of α-arylstyrene. Various characterization techniques such as N2 adsorption–desorption, X-ray diffraction (XRD), FT-IR, NH3 temperature-programmed desorption (NH3-TPD), and pyridine-IR were employed to reveal the relationship between catalyst nature and catalytic performance. The as-prepared SO4 2−/meso-La2O3–ZrO2 catalyst shows much superior catalytic activity and similar selectivity to SO4 2−/meso-ZrO2, ascribed to increasing acid properties, enlarging specific surface area and increasing pore volume, reducing average crystalline size resulting from the promoting effect of adding La into ZrO2 matrix. Furthermore, the SO4 2−/meso-La2O3–ZrO2 catalysts were optimized by varying the atomic ratio of La/(La + Zr) from 0.05 to 0.2. The SO4 2−/meso-La2O3–ZrO2 catalyst with the 0.1 of optimum La/(La + Zr) atomic ratio exhibited excellent catalytic performance, ascribed to the increase in amount acid sites and pore size. The results for stability test demonstrated that close to 100% of maximum conversion can be achieved, and more than 80% of conversion can be maintained with the time on stream up to 780 min. Through simple calcination treatment, the spent catalyst can be almost complete recovered. The developed SO4 2−/meso-La2O3–ZrO2 catalyst could be a potential candidate for α-arylstyrene production via acid catalyzed direct alkenylation of aromatics with phenylacetylene.
Keywords: Mesoporous materials; SO4 2−/ZrO2 solid acid; La modification; Alkenylation; Heterogeneous catalysis;
Surface reactivity and self-oscillating oxidation of butan-2-ol over palladium loaded AlPO4 by Omar Ouariach; Mohamed Kacimi; Mahfoud Ziyad (84-93).
Palladium loaded AlPO4 catalysts were synthesised and characterised by XRD, IR, UV–vis spectroscopy, temperature programmed desorption (TPD) and temperature programmed surface reaction (TPSR). The Pd2+ ions of the dispersed palladium on the amorphous surface of AlPO4 are in D4h symmetry. They can partially be reduced into Pd0 even in dynamic conditions by a mixture of butan-2-ol and oxygen. TPD/TPSR showed that the active sites are formed by the couple PdO/Pd. The presence of PdO on the surface favours the production of methyl ethyl ketone (MEK). The CO2 formation was never observed below 100 °C. Moreover, desorption of the MEK takes place in two waves arising from two different types of sites. Only the reactivity of the first set of sites which are located around 80 °C was considered in the present study. As a matter of fact, the oxidation of butan-2-ol into MEK (<1.3%) at 74.2 °C describes a counter-clockwise hysteresis attributed to a bistability induced by the competition between the redox processes that the surface and the reagents undergo. This sensibility of the catalyst to the parameters governing the reaction resulted in an oscillating oxidation of butan-2-ol. Spontaneous oscillations of the MEK production (α one) appear around 85 °C and stop before 100 °C. Oscillations of the temperature of the catalyst bed were also recorded but their amplitude never exceeds 7 °C. An oscillatory regime appears also for butan-2-ol pressures ranging from 0.61 to 1.65 kPa and for a total flow rate between 80 and 260 mL min−1. The oscillating oxidation of butan-2-ol is accompanied by a significant enhancement of the methyl ethyl ketone production.
Keywords: Pd(x)/AlPO4; TPD/TPSR; Butan-2-ol oxidation; Hysteresis loop; Oscillating oxidation;
Phyllosilicate evolved hierarchical Ni- and Cu–Ni/SiO2 nanocomposites for methane dry reforming catalysis by Tao Wu; Qing Zhang; Weiye Cai; Peng Zhang; Xuefeng Song; Zhuang Sun; Lian Gao (94-102).
Display OmittedWell dispersed Ni and Cu–Ni alloy nanoparticles (∼7 nm) embedded in nanosheets of hierarchical SiO2 hollow spheres (surface area > 400 m2/g) have been synthesized through a hydrothermal process and have shown superior catalytic performance in methane dry reforming (DRM) reaction to the impregnated control sample based on SiO2 nanospheres. The catalytic activity and the sintering and coke resistant properties of the hierarchical composite catalysts in the high temperature DRM catalysis are ascribed to the strong metal–support interaction and the well dispersed small metal nanoparticles.
Keywords: Hierarchical; Ni/SiO2; Cu–Ni/SiO2; Methane dry reforming; Catalysis;
Supported phosphotungstic acid catalyst on modified activated carbon for Friedel–Crafts alkenylation of diverse aromatics to their corresponding α-arylstyrenes by Zhongkui Zhao; Xianhui Wang (103-110).
Display OmittedThe supported phosphotungstic acid catalysts on modified activated carbon (PTA/AC) prepared by a facile wet impregnation method were employed for Friedel–Crafts alkenylation of diverse aromatics with phenylacetylene to synthesize their corresponding α-arylstyrenes. Reaction results demonstrate that the fabricated PTA/AC catalyst with 30 wt.% PTA loading exhibits outstanding catalytic performance. The 100% conversion of phenylacetylene with 95.7% selectivity towards α-(2,5-dimethylphenyl) styrene can be achieved over the developed 30 wt.% PTA/AC catalyst under optimized reaction conditions, and no visible loss in catalytic performance can be observed after it suffers from several times recycling. The various characterization techniques including X-ray diffraction, N2 adsorption–desorption, Fourier transform infrared spectroscopy, and NH3 temperature-programmed desorption were employed to reveal the relationship between the catalysts nature and catalytic properties. Moreover, the results on the scope of aromatics for the Friedel–Crafts alkenylation illustrate that the developed PTA/AC alkenylation catalyst can be efficiently catalyze the diverse aromatics and even for the electron deficient chlorobenzene. The developed PTA/AC catalyst, using the modified low-cost and sustainable AC as support, may be a robust and promising candidate for highly-efficient and clean α-arylstyrenes production through Friedel–Crafts alkenylation of diverse aromatics including electron-donating and electron-withdrawing groups substituted benzene derivatives as well as heterocyclic and polypolycyclic arenes with phenylacetylene.
Keywords: Activated carbon; Phosphotungstic acid; Alkenylation; Clean synthesis; Heterogeneous catalysis;
In situ magnetic resonance imaging study of the impregnation of γ-alumina pellets by A. Nowacka; J. Moughames; Z. Adem; A.-A. Quoineaud; M. Rolland; F. Guenneau; A. Gédéon (111-116).
Display OmittedIn petroleum refining, γ-alumina is used as a solid support of molybdenum nickel/cobalt promoted catalysts for the hydrotreatment processes, such as hydrodesulfurization. The ever decreasing norms for the sulfur content in gasoline require better and more efficient catalysis, prompting extensive research on the materials and the factors influencing the activity, selectivity and stability of the catalytic processes. In the present study, Magnetic Resonance Imaging Single Point Imaging is tested as a tool to monitor the impregnation of γ-alumina pellets with Ni(NO3)2 aqueous solutions at varying Ni2+ concentration. The method enables a study in the presence of paramagnetic elements in the alumina support, in the conditions of very fast T1 and T2. It is shown that at higher concentrations of metal ions a homogenous distribution in the support is attained faster. A non-linear dependence is observed and a minimum ion concentration of 0.2 M is necessary for achieving short impregnation times of alumina pellets of millimeter size scale.
Keywords: MRI; SPI; γ-Al2O3; Alumina impregnation; Catalyst preparation; Ni2+;
Zr-doped CeO2 nanorods as versatile catalyst in the epoxidation of styrene with tert-butyl hydroperoxide as the oxidant by Xin Liu; Jing Ding; Xi Lin; Ruihua Gao; Zhenhua Li; Wei-Lin Dai (117-123).
Display OmittedThe CeO2 nanorods with various Zr dopant concentrations were studied in terms of their activity in the selective oxidation of styrene to styrene oxide using tert–butyl hydroperoxide as the oxidant. Several techniques were used to characterize the synthesized Zr-doped CeO2 nanorods. The results indicated that Zr ions were doped into the ceria lattice and formed fluorite-like solid solutions, resulting in an increase in oxygen vacancy concentration. It was also found that Zr content has a significant impact on intrinsic natures of the catalyst, namely, the specific surface area, oxygen vacancy concentration and the content of Ce3+ ions, which were found to determine the catalytic efficiency of the catalyst in the epoxidation of styrene. It is interesting that the remarkably increased catalytic performance of the ceria nanorods with 10 mol% zirconium is mainly attributed to the more oxygen vacancy and the higher percentage of Ce3+. Furthermore, recycling studies proved the heterogeneous zirconium-doped ceria nanorods did not lose the initial high catalytic activity after five successive recycles.
Keywords: Zr-doped CeO2 nanorods; Styrene; Oxygen vacancies; Selective oxidation; TBHP;
Visible light-driven photoactivity of zinc oxide impregnated chitosan beads for the detoxification of textile dyes by M. Hasmath Farzana; Sankaran Meenakshi (124-134).
The photocatalytic decolorization of model textile dyes, namely, Methylene Blue (MB) and Rhodamine B (RB) dyes using zinc oxide (ZnO) and zinc oxide impregnated chitosan beads (ZCB) under UV and visible light irradiations were investigated. ZCB was synthesized in order to enhance the photoresponse of ZnO toward visible light using chitosan, a well-known biopolymer. The ZnO and ZCB photocatalysts were characterized by Fourier transform-infrared spectra (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), diffuse reflectance spectra (DRS) and X-ray diffraction studies (XRD). In order to optimize various experimental parameters viz., irradiation time, the amount of catalyst, pH, co-ions, initial concentration of dye, experiments were conducted under UV and visible light irradiations. The percentage of decolorization of MB and RB dyes using ZnO and ZCB is in the order of ZnO/UV > ZCB/vis > ZnO/vis. The mineralization of dyes was assessed by measuring chemical oxygen demand (COD) at optimized conditions. The rate of photodecolorization of MB and RB dyes follows the pseudo-first-order kinetics. The reuse of ZCB in the photocatalytic decolorization of textile dyes has also been studied.
Keywords: Visible light; Zinc oxide; Chitosan; Band gap energy; Chemical oxygen demand;
Highly selective conversion of maleic anhydride to γ-butyrolactone over Ni-supported catalysts prepared by precipitation–deposition method by Matías E. Bertone; Camilo I. Meyer; Silvina A. Regenhardt; Victor Sebastian; Teresita F. Garetto; Alberto J. Marchi (135-146).
Display OmittedThe gas-phase hydrogenation of maleic anhydride over Ni catalysts supported on SiO2 and SiO2–Al2O3, prepared by incipient wetness impregnation (I) and constant-pH precipitation–deposition (PD), was studied. The samples were characterized by N2 adsorption at −196 °C, X-ray diffraction, temperature-programmed reduction, H2 chemisorption, X-ray photoelectron spectroscopy, and transmission electron microscopy. The catalytic tests were carried out at atmospheric pressure, between 170 and 220 °C and using a space-time of 12 g h mol−1. From the characterization results, it was determined that the interaction between Ni2+ species and the support strongly depends on the preparation method. The trend found for the Ni2+-support interaction was Ni/SiO2-PD >Ni/SiO2-Al2O3-PD > Ni/SiO2-I. After reduction in H2 flow, metal Ni particles were one order of magnitude smaller in catalysts prepared by precipitation–deposition than those prepared by impregnation. All catalysts were active for the hydrogenation of maleic anhydride (MA) into succinic anhydride (SA) and subsequent hydrogenolysis to γ-butyrolactone (GBL) and propionic acid (PA). Regardless of small amounts of CH4, no other products were detected at the reactor outlet. However, the activity and selectivity to GBL depends on the metal particle size, Ni-support interaction and the presence of Lewis acid sites on SiO2–Al2O3 surface. It was found that the small metallic particles obtained by precipitation–deposition method are more active and selective to GBL than the large particles formed using the impregnation method. The highest GBL yield (83%) was reached at 220 °C with Ni/SiO2–Al2O3–PD, which is attributed to selective hydrogenolysis of SA adsorbed on Lewis acid sites by spillover of hydrogen chemisorbed on neighboring metal nickel nanoparticles.
Keywords: Ni catalysts; Precipitation–deposition; γ-Butyrolactone; Maleic anhydride; Hydrogenation;
Combined desilication and phosphorus modification for high-silica ZSM-5 zeolite with related study of hydrocarbon cracking performance by Jian Ding; Meng Wang; Luming Peng; Nianhua Xue; Yimeng Wang; Ming-Yuan He (147-155).
Display OmittedMesoporosity was introduced into high-silica ZSM-5 zeolite (SiO2/Al2O3 = 417) by controlled desilication using the mixture of NaOH and TEAOH (tetraethylammonium hydroxide), and subsequent phosphorus modification was used to improve the structural stability and acidity reservation of the desilicated ZSM-5 samples during the procedure of severe steam aging treatment. The phosphorus modified mesoporous ZSM-5 sample along with parent ZSM-5, solo phosphorus modified ZSM-5 and mesoporous ZSM-5 were characterized by techniques of N2 adsorption-desorption, NH3-TPD (temperature programmed desorption), IR (infrared) spectroscopy of pyridine adsorption and 27Al &31P MAS NMR spectroscopy. A mechanism for underlying chemistry of the combinative treatment was proposed. The aluminophosphate formed in the steam activation could interact with the framework aluminum on zeolite, thus achieved to the textural and acidity stabilization during the steam aging. The catalytic performance of these samples was tested by different hydrocarbon cracking reactions. It turned out that owing to its reduced diffusion limitation and stabilized acidity, the phosphorus modified mesoporous ZSM-5 sample exhibited the highest conversion in the bulky molecule cracking reaction. And in the 1-octene cracking reaction under harsh reaction conditions, the steamed phosphorus modified mesoporous ZSM-5 sample exhibited higher activity and more prolonged catalyst life compared to the other steamed catalysts, which could be attributed to the improved coke tolerance capability by mesoporosity introduction and the stabilized acid sites by phosphorus modification.
Keywords: Desilication; Mesoporous ZSM-5; Phosphorus modification; Hydrothermal stability; Hydrocarbon cracking;
Hydrophobicity enhancement of Ti-MWW catalyst and its improvement in oxidation activity by Hong Zhao; Toshiyuki Yokoi; Junko N. Kondo; Takashi Tatsumi (156-164).
The effect of the preparation conditions of the Ti-MWW catalyst on the hydrophobicity of the catalyst and its catalytic activity was investigated. Our findings demonstrated that the condensation of interlayer hydroxyl groups was greatly affected by the preparation conditions, in particular washing conditions of the as-synthesized lamellar precursor of Ti-MWW, then further controlling the final hydrophobicity and oxidation properties. Using organic solvents, especially EAOH, instead of water to wash the wet lamellar precursor would synchronize the interlayer hydroxyl condensation with the decrease of interlayer distance mainly caused by the leaching of piperidine, which was used as structure-directing agent (SDA). After acid-treatment, less SDA was kept in the EAOH washed sample and 3D-MWW with less defects was formed by calcination. Both drying temperature and acid-treatment would also affect the amount of SDA occluded in the interlayer void space of the acid-treated samples and then further affect the final interlayer hydroxyl condensation upon the following calcination. The lower both drying temperature and acid-treatment temperature were favorite to unequal interlayer dehydroxylation to form MCM-56, while higher drying temperature such as 150 °C not only caused the anatase phase in the calcined samples but also occluded more SDA molecules in the acid-treated samples which greatly affect the further interlayer hydroxyl condensation upon the calcination. Ti-MWW-OH-100 containing smallest amount of silanols and less defect sites showed the best hydrophobicity and the highest catalytic activity in 1-hexene oxidation.
Keywords: Ti-MWW; Preparation conditions; Hydrophobicity; Catalytic activity;
Effect of MnO x in the catalytic stabilization of Co2MnO4 spinel during the ethanol steam reforming reaction by Byeong Sub Kwak; Gayoung Lee; Sun-Min Park; Misook Kang (165-175).
Display OmittedCo-based spinel-structured Co2MnO4 was assessed as a catalyst for the ethanol steam reforming reaction. Ethanol conversion over spinel-structured Co2MnO4/SBA-15 was comparable to that over Co x O y /SBA-15 and Co x O y /Mn x O y /SBA-15 after a reduction treatment. The spinel structure of Co2MnO4 exhibited extremely stable performance until 71 h, whereas the catalytic activities of the Co x O y /SBA-15 and Co x O y /Mn x O y /SBA-15 were reduced by carbon deposition involving different reforming mechanisms. The catalytic stability for the reforming reaction was closely related to the stability of the cobalt oxidation states through the assistance of manganese oxides and its spinel structure. The Co2MnO4/SBA-15 exhibited the highest activity for the reforming reaction at 700 °C. Cobalt in the spinel structure of Co2MnO4 is believed to make a major contribution to the absolute catalytic activity because there is little or no catalytic deactivation induced by aggregation between their particles compared to the impregnated cobalt ingredients. On the other hand, manganese oxide in the spinel structure of Co2MnO4 was suggested to provide oxygen to the cobalt catalytic active sites, resulting in increases in hydrogen production and the suppression of CO generation.
Keywords: Spinel-structure; Co2MnO4; Hydrogen production; Ethanol steam reforming; Co x O y /SBA-15; Co x O y /Mn x O y /SBA-15;
A green chemical route for synthesis of graphene supported palladium nanoparticles: A highly active and recyclable catalyst for reduction of nitrobenzene by S.I. El-Hout; S.M. El-Sheikh; Hassan M.A. Hassan; Farid A. Harraz; I.A. Ibrahim; E.A. El-Sharkawy (176-185).
Display OmittedA facile green chemical reduction approach is developed to synthesize palladium (Pd) nanoparticles (NPs) supported on reduced graphene oxide (RGO) using exfoliated graphite oxide as a precursor with various reducing agents, including salicylic acid, oxalic acid, ascorbic acid, NaOH and hydrazine hydrate. The as-prepared catalysts were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transfer infrared (FT-IR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The catalytic performance has been examined for the reduction of nitrobenzene using sodium borohydride as a reducing agent under mild conditions. Our findings indicated that most of oxygen functionalities are removed using green chemical reduction approach associated with the good catalytic performance. The catalytic activity depends particularly on target concentration, catalyst loading and reaction time. The results of this research would develop a new one-pot synthesis avenue for the preparation of Pd/RGO nanocomposite materials and provides the application of Pd/RGO into the heterogeneous catalysis.
Keywords: Palladium nanoparticles; Reduced graphene oxide; Nitrobenzene reduction;
Polystyrene-supported ionic liquid copper complex: A reusable catalyst for one-pot three-component click reaction by Mahnaz Tavassoli; Amir Landarani-Isfahani; Majid Moghadam; Shahram Tangestaninejad; Valliolah Mirkhani; Iraj Mohammadpoor-Baltork (186-195).
Display OmittedCopper(II) complex of 1,2-bis(4-pyridylthio)ethane immobilized on polystyrene was a used as a highly stable, active, reusable and green catalyst for click synthesis of 1,2,3-triazoles via one-pot three-component reaction of organic halides, sodium azide and alkynes. The catalyst was characterized by FT-IR spectroscopy, thermogravimetric analysis, elemental analysis, field emission scanning electron microscopy, energy dispersive X-ray, transmission electron microscopy and elemental analysis. High selectivity, broad diversity of organic halides or α-bromoketones and alkyl/aryl terminal alkynes, and excellent yields of the products were obtained using 0.2 mol% of catalyst. This catalytic system also showed excellent activity in the synthesis of bis-1,4-disubsitituted 1,2,3-triazoles. Moreover, the catalyst could be recycled and reused for seven cycles without any decrease in its catalytic activity.
Keywords: Copper complex; Click reaction; Polystyrene; Triazole; Ionic liquid;
The effect of metal composition on the performance of Ir–Au/TiO2 catalysts for citral hydrogenation. by Hugo A. Rojas; José J. Martínez; Gabriela Díaz; Antonio Gómez-Cortés (196-202).
Display OmittedThe effect of gold addition to iridium catalysts and the nature of active sites for citral hydrogenation were investigated over Ir–Au/TiO2 catalysts. All samples (Au/TiO2, Ir/TiO2 and Ir–Au/TiO2) were prepared by deposition-precipitation with urea (DPU). Bimetallic catalysts were synthetized by co-deposition at different Ir/Au atomic ratios (3, 1, 0.3). The catalysts were characterized by ICP, BET, H2–TPR, H2-Chemisorption, TEM, DRIFTS and XPS techniques. A partial coverage of iridium sites by gold atoms takes place as the gold amount in the catalyst increases as shown by chemisorption and XPS measurements. The latter also evidenced a trend consistent with modification of the electronic environment of iridium due to interaction with gold atoms. Also, compared to Ir/TiO2, the amount of Irδ+ species was higher in the bimetallic catalysts reaching a maximum in Ir–Au (1) sample. Characterization of the catalytic surface using DRIFTS of adsorbed CO evidenced a shift towards higher wavenumbers as a function of the gold content indicating, as the XPS results, a modification of the adsorption site. The catalytic activity for citral hydrogenation increased as a function of the gold content. The selectivity to unsaturated alcohol is related to the amount of Irδ+ species which in turns depends on the catalyst composition. For the most active sample Ir–Au (1), a suitable Irδ+/Ir0 ratio is already obtained when the catalyst is reduced at 573 K and does not vary with reduction temperature.
Keywords: Ir–Au; TiO2; Citral; Hydrogenation; Irδ+/Ir0 ratio;
A heterogeneous mesoporous silica-supported cyclopentadienyl ruthenium(II) complex catalyst for selective hydrosilylation of 1-hexyne at room temperature by Dang Do Van; Takuya Hosokawa; Masakazu Saito; Yu Horiuchi; Masaya Matsuoka (203-208).
Display OmittedA cyclopentadienyl ruthenium(II) complex has been immobilized on MCM-41 modified with aminopropyl group through an amide bond formation reaction. FT-IR and UV–vis spectra show successful immobilization of cyclopentadienyl ruthenium complex onto the mesoporous silica surface by utilizing the amino group as a connector. The coordination state of the ruthenium complex is analyzed in detail by XAFS measurements, which indicate that the immobilization process does not influence its coordination geometry. Moreover, the retaining of long range ordering of the mesoporous structure of MCM-41 after grafting is evident from the results of XRD and N2 adsorption–desorption measurements. The resulting material promotes efficiently the hydrosilylation of 1-hexyne to produce vinylsilane with high α-selectivity under UV-irradiation at room temperature. Furthermore, the catalyst is recyclable for several catalytic runs without significant loss of its catalytic activity.
Keywords: Heterogeneous catalyst; Ru complex; Mesoporous silica; Hydrosilylation;
Sol–gel-hydrothermal synthesis of Er3+:Y3Al5O12/Pt–TiO2 membrane and visible-light driving photocatalytic hydrogen evolution from pollutants by Hongbo Zhang; Chunhong Ma; Yun Li; Yang Chen; Chunxiao Lu; Jun Wang (209-217).
Display OmittedA novel visible-light photocatalyst, Er3+:Y3Al5O12/Pt–TiO2 membrane, was prepared via sol–gel–hydrothermal method on glass substrates as a support. X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) were used to reveal the crystallinity, surface morphology and chemical composition of the prepared Er3+:Y3Al5O12/Pt–TiO2 membrane. The catalytic activity of Er3+:Y3Al5O12/Pt–TiO2 membrane was examined through the photocatalytic hydrogen evolution from some pollutants, including phenol, glycerol and Na2S/Na2SO3, which were used as electron donors, under visible-light irradiation. Furthermore, some influence factors, such as mass ratio, pre-treatment temperature and used times, on the photocatalytic activity of Er3+:Y3Al5O12/Pt–TiO2 membrane were studied. The experimental results showed that the Er3+:Y3Al5O12/Pt–TiO2 membrane is a good and broad-spectrum photocatalyst in visible-light photocatalytic hydrogen evolution with simultaneous pollutant solution treatment.
Keywords: Sol–gel–hydrothermal method; Er3+:Y3Al5O12/Pt–TiO2 membrane; Visible-light photocatalyst; Hydrogen evolution; Pollutant degradation;
Dehydroaromatization of methane over Sn–Pt modified Mo/H-ZSM-5 zeolite catalysts: Effect of preparation method by Themba E. Tshabalala; Neil J. Coville; James A. Anderson; Michael S. Scurrell (218-226).
Display OmittedThe effect of different catalyst preparation methods to make tin–platinum modified Mo/H-ZSM-5 zeolite catalysts for methane dehydroaromatization at 700 °C was investigated. The catalysts were prepared by both incipient wetness co-impregnation and sequential impregnation and calcined at 500 °C for 6 h. Catalysts prepared by the co-impregnation method showed a good platinum dispersion (10.8%), higher than found for the Pt/Sn and Sn/Pt sequentially impregnated catalysts (5.6% and 1.4%, respectively). Successive calcination treatments influenced the location of both tin and platinum in the catalyst and a decrease in platinum dispersion after reduction was evident from CO chemisorption studies. The order of sequentially loading platinum before or after tin had an effect on the electronic and structural properties of platinum as shown by XPS and FTIR studies. Different catalytic activities and aromatic selectivities were observed for the Pt/Sn and Sn/Pt catalysts. The co-impregnated Sn–Pt and the sequentially impregnated Pt/Sn catalysts showed high aromatic selectivity (>70%) and low coke selectivity (<20%). The decrease in coke selectivity is mainly dependent on the availability of platinum sites for hydrogenation of carbonaceous species.
Keywords: Methane dehydroaromatization; H-ZSM-5; Tin; Platinum; Molybdenum;
An experimental assessment of the ammonia temperature programmed desorption method for probing the surface acidic properties of heterogeneous catalysts by Francesco Arena; Roberto Di Chio; Giuseppe Trunfio (227-236).
Display OmittedThe surface acidic properties of oxide catalysts and carriers (γ-Al2O3, CeO2, ZrO2, SiO2, TiO2, HZSM5 zeolite) have been comparatively probed by ammonia temperature programmed desorption (ATPD) measurements. Reliability and accuracy of ATPD data were assessed by theoretical criteria and experimental tests highlighting the effects of carrier gas, data acquisition mode, catalyst particle size and reactor geometry. All the materials feature complex ATPD patterns spanned in the range 423–873 K, except for ceria showing a narrow and resolved desorption peak, indicative of homogeneous weak acidity. Quantitative data signal a difference of more than one order of magnitude in ammonia uptake between silica and the other materials. Since the ATPD profiles of ceria match Gaussian curves regardless of heating rate and surface coverage, the patterns of the studied materials are described as linear combinations of four Gaussian functions related to weak, medium, strong and very strong site populations. ATPD modelling analyses to get energy data are discussed. The functionality of the studied materials in the dehydration of isopropanol to propylene matches abundance, type and strength of surface acid sites.
Keywords: Ammonia temperature programmed desorption (ATPD); Modeling analysis; Energy distribution function; Acid sites; Type and strength;