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Quinoline-imine nickel (II) complexes were immobilized in fluorotetrasilicic mica interlayers by a one-pot synthesis through the reaction of a nickel ion-exchanged fluorotetrasilicic mica (Ni 2+ -mica) with the corresponding quinoline and aniline derivatives. After activation of the prepared precatalyst by a co-catalyst (Et 3 Al, i Bu 3 Al, or Et 2 AlCl), it showed a high catalytic activity for the oligomerization of ethylene with the formation of oligomers having carbon numbers 4–20. The maximum activity (168 g-product g-cat −1 h −1 ) was obtained by the oligomerization at 40 °C and 1.0 MPa in the presence of Et 3 Al using the precatalyst prepared from Ni 2+ -mica, 2-acetylquinoline, and 2, 6-dimethylaniline. In all the oligomerization runs, a long induction period was observed, and the induction time significantly depended on the co-catalyst. This induction period might be caused by the characteristic structure of the precatalysts. The FT-IR and XRD spectra of the precatalysts indicated the formation of the intended nickel complexes in the mica interlayer.

The effects of CO and H 2 S as catalyst inhibitors on the rate of toluene hydrogenation were studied as a means of hydrogen storage using low-grade hydrogen. Pd/SiO 2 suffered serious negative effects from catalyst inhibitors; however, Pd/TiO 2 –SiO 2 exhibited high CO and H 2 S tolerance because the acidic support decreased the electron density of the Pd metal particles, which, in turn, decreased the interaction between the Pd surface and CO (or H 2 S). The TiO 2 –SiO 2 -supported Pd catalyst exhibited activity greater than that of the TiO 2 –SiO 2 -supported Pt catalyst in the presence of CO; however, it exhibited lower activity in presence of H 2 S. Catalyst characterization after sulfidation with H 2 S revealed that Pd particles were fully sulfided, whereas Pt particles were sulfided only on their surface. We concluded that Pd catalysts supported on acidic oxides exhibit excellent activity toward toluene hydrogenation in the presence of CO and that Pt catalysts exhibit excellent activity in the presence of H 2 S.

To develop heterogeneous catalysts for ethylene polymerization, bis(imino)pyridineiron(III), α-diiminenickel(II), and iminopyridinenickel(II) complexes were immobilized in the clay mineral (montmorillonite, fluorotetrasilicic mica or saponite) interlayers by a one-pot preparation method. In this method, the Fe3 +- and Ni2 +-exchanged clay minerals as an acid catalyst promoted the ligand formation from a ketone derivative and an aniline derivative, and then the formed ligand simultaneously coordinated to the metal ions located in the clay mineral interlayer. The obtained heterogeneous catalysts showed 100–3,000 g-PE g-cat− 1 h− 1 as activities for the ethylene polymerization/oligomerization.

Fe–Ce mixed oxide catalysts promoted by Rb and Cs have been investigated for the dehydrogenation of ethylbenzene. Fe–Ce–Rb and Fe–Ce–Cs were found to be highly active. X-ray diffraction (XRD) analysis confirmed the formation of RbFeO2 and CsFeO2 in the catalyst. X-ray photoelectron spectroscopy (XPS) analysis suggests a surface composition of the catalysts with an atomic ratio of Rb/Fe = 1, Cs/Fe = 1 and O/Fe = 2, meaning the surface is composed of the binary oxides, RbFeO2 and CsFeO2. We conclude that the active phases of these catalysts are RbFeO2 and CsFeO2, similar to KFeO2 in the case of K–Fe and Fe–Ce–K mixed oxide catalysts. The rate equation of the reaction was determined supposing a Langmuir–Hinshelwood mechanism, in which the competitive adsorption of ethylbenzene and styrene dominate the reaction rate. However, the relative adsorption constant of styrene, Z ST, did not change significantly with the addition of Rb or Cs. The rate constant k increased with the addition of Rb or Cs. The activation energy increased with the addition of Rb or Cs compared with Fe–Ce, and the frequency factor also increased remarkably. Because the strong base points are most likely the active sites, addition of Rb and Cs increased the number of basic sites on the catalyst surface, resulting in higher activity. The kinetic factors, k and Z ST, were applied for the rate equation. The experimental results were in very good agreement with the derived rate equation.

Heterogeneous catalysts for production of linear α-olefins from ethylene were prepared by the direct reaction of the α-diimine ligand [L: R-N=C(R')-C(R')=N-R; R' = Me and R = 2,6-Me2Ph (L5), 2,5-Me2Ph (L1), 2-MePh (L2), or Ph (L3); R' = 1,8-naphth-diyl and R = Ph (L4)] and Ni2+ ion-exchanged fluorotetrasilicic mica. Only high molecular weight polyethylene was obtained in the reaction using the L5/Ni2+-Mica procatalyst activated by AlEt3 (TEA) as an activator, whereas the TEA-activated L1- and L2/Ni2+-Mica procatalysts afforded a mixture of a large amount of low-molecular weight polyethylene and a small amount of oligomers having 4-22 carbons. The procatalyst consisting of Ni2+-Mica and the L3 ligand that possesses non-substituted phenyl groups on the iminonitrogen atoms effectively promoted the oligomerization of ethylene after its activation with TEA, resulting in the fact that the ethylene oligomers were produced with a moderate catalytic activity (101 g-ethylene g-cat−1 h−1 at 0.7 MPa-ethylene) in the presence of TEA. When the backbone was varied from the butane moiety (L3) to acenaphthene (L4), the solid product dramatically increased. The weight percentage of the oligomers in the total products increased with the increasing reaction temperature; however, an insignificant increase in the oligomers was observed when the ethylene pressure was decreased.

The effect of pretreatment conditions on the dispersion of Pt/SiO 2 was studied. The catalysts were prepared by impregnation with H 2 PtCl 6 as the Pt precursor. Direct reduction of the supported Pt precursor in hydrogen flow was compared to calcinations of the precursor in air flow at various temperatures followed by reduction in hydrogen flow. When the supported precursor was directly reduced in hydrogen flow, Pt dispersion was independent of the reduction temperature. In contrast, when the supported precursor was calcined and then reduced, Pt dispersion was not affected by the reduction temperature but depended heavily on the calcination temperature, ranging widely from 7 to 70%. A good correlation was seen between the particle size calculated from CO adsorption and that observed with transmission electron microscope. Furthermore, it was found that calcination at the temperature at which PtCl 2 is stable gives the highest Pt dispersion. X-ray fluorescence analysis of the calcined samples confirmed the formation of PtCl 2 . High Pt dispersion after calcination at optimum temperature was also corroborated with X-ray diffraction analysis from the absence of sharp diffraction peaks. The results suggest that prompt formation and redispersion of PtCl 2 caused high Pt dispersion.

The effect of adding Fe2O3 to an Al2O3-supported Pt catalyst on isobutane dehydrogenation was studied. Catalytic activity, catalyst stability, and selectivity to isobutene were improved significantly by adding a small amount of Fe2O3 to Pt/Al2O3. The catalysts were characterized by CO and NH3 chemisorption measurements, Fourier transformed-infrared (FT-IR) analysis of adsorbed CO, and thermogravimatric-differential thermal analysis (TG-DTA) of the used catalyst. FT-IR analysis of the adsorbed CO showed that the electron density of Pt was increased by the formation of bimetallic particles. CO chemisorption suggested the formation of Pt-Fe bimetallic particles partially covered with Fe species. Furthermore, the number of strong acid sites on the Al2O3 surface was decreased by adding Fe2O3. Analysis of the used catalysts suggested that the addition of Fe2O3 inhibited sintering of supported Pt particles. The addition of Sn to Pt/Fe2O3-Al2O3 further improved the dehydrogenation activity of the catalyst. This catalyst showed better catalytic activity than that of Pt-Sn/Zn-Al-O, which has been employed in a commercial process and has been reported as an excellent catalyst in dehydrogenation reactions. We claim that we have developed a novel dehydrogenation catalyst system, Pt-Sn/Fe2O3-Al2O3, which has better catalytic properties than the reported commercial catalyst.

In order to examine the capability of AlPO4 to serve as a catalytic support, we analyzed naphthalene hydrogenation over Pd/AlPO4 catalyst in the presence of CO. This process is an effective storage strategy in the organic hydride method that uses low grade hydrogen. Pd/AlPO4 demonstrated high activity in naphthalene hydrogenation similar to Pd/SiO2–Al2O3, and retained the activity in much higher extent in the presence of CO as compared to Pd/Al2O3. The existence of acidic sites on the surface of AlPO4 was confirmed by ammonia adsorption. FT–IR analysis of adsorbed CO after high temperature evacuation revealed that CO desorbed more easily on Pd surface when supported on acidic materials. Detailed analysis of the IR spectra suggested that acidic support decreased the electronic density of Pd and weakened the adsorption bond. Because CO retardation decreased on acidic supports, Pd catalysts demonstrated high activity in the presence of CO. We found that AlPO4 was an effective acidic support for Pd catalyzed hydrogenation.

The cyclodimerization of crotonaldehyde was performed over acid or base catalysts in the gas phase. We first attempted the reaction over various acid and base catalysts using a pulse reactor. The typical bases, CaO and MgO, effectively promoted the reaction to form methylcyclohexadienecarbaldehydes (MCHC) and tolaldehydes. In contrast, no significant formation of the dimers was observed over the acid catalysts, such as SiO2–Al2O3 and H-mordenite. Aluminum oxide also promoted the dimerization, indicating that the dimerization proceeds on the weaker base sites. The main products in the formed dimers were 6-methylcyclohexa-1,3-dienecarbaldehyde and o-tolualdehyde. In addition, small amounts of 4-methylcyclohexa-1,5-dienecarbaldehyde and p-tolaldehyde were produced as dimers. When the dimerization was performed over CaO, MgO, and Al2O3 using a fixed-bed flow reactor, the catalytic activities of all the catalysts significantly decreased during the initial stage of the reaction. The TG–DTA analysis of the used catalysts clearly indicated that a large amount of the condensation products had adsorbed on the catalyst surface. The maximum selectivity to the dimers (MCHC and tolaldehydes) was 38% for an approximate 30% conversion, which was obtained during the initial stage of the reaction over the Al2O3 and CaO catalysts.

Heterogeneous bis(imino)pyridinecobalt(II) catalysts were prepared by direct reaction of cobalt-ion-exchanged fluorotetrasilicic mica and a bis(imino)pyridine ligand. The catalyst prepared from the...

The influence of trace oxygen on the catalytic activity of alumina supported Ru in the liquid phase hydrogenation of aromatic hydrocarbons was studied. The catalytic activity of Ru increased remarkably and the reproducibility was improved by removing dissolved oxygen from the reactant mixture and carefully refining the catalyst transfer procedure into the reactor to avoid exposure to air. Trace oxygen affected Ru very severely, but did not affect Rh, Pd, and Pt much. The activity of Ru was lower than those of Rh, Pd, and Pt in the presence of oxygen as reported in the literature; however, it was the highest when oxygen was removed carefully. Measurements of the adsorbed oxygen suggested that the activity seriously decreased when only the part of Ru surface was covered by oxygen. Bimetallic Pt–Ru catalysts demonstrated high activity even in the presence of oxygen.

Supported catalysts consisting of Cp 2 ZrCl 2 and cation-exchanged fluorotetrasilicic mica (M n + -mica, M n + = Na + , Mg 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ ) were prepared and employed in the ethylene polymerization or ethylene/1-hexene copolymerization in the presence of R 3 Al. The catalysts consisting of swellable Mg 2+ -mica and Zn 2+ -mica (both calcined at 200 °C) and Cp 2 ZrCl 2 displayed high activity for the polymerization reaction. By contrast, when Mg 2+ -mica and Zn 2+ -mica were calcined above 250 °C, the swellability was lost, and the activities of Cp 2 ZrCl 2 supported on these non-swellable micas were significantly reduced. The relationship between the activity and swellability of mica was clearly observed both in ethylene polymerizations employing ( n -BuCp) 2 ZrCl 2 in place of Cp 2 ZrCl 2 and in ethylene/1-hexene copolymerizations using Cp 2 ZrCl 2 . The role of M n + -mica for the activation of the metallocene complex was investigated by surface observation using a scanning electron microscope and by XRD measurements of the catalysts after polymerization of ethylene for a short time. The results of the surface observations indicated that polyethylene was produced on the edges of M n + -mica lamellas at the initial stage of the polymerization. The XRD measurements show that the regularity of the stacked lamellas was immediately lost at this stage. The catalyst prepared by removing free Cp 2 ZrCl 2 (i.e., unsupported Cp 2 ZrCl 2 , Cp 2 ZrCl 2 dissolved into the catalyst slurry) showed extremely low activity, suggesting that the most of the active sites were formed through the reactions of M n + -mica and free Cp 2 ZrCl 2 . These results indicate that the lamellas of M n + -mica are peeled off at the initial stage of the polymerization and that exposed metal cations react with free-Cp 2 ZrCl 2 to form additional active species. The swellability of M n + -mica strongly affects the formation of additional active sites, and therefore the supported catalysts based on non-swellable M n + -mica displayed only low activities.

Dehydrogenation of propane combined with selective hydrogen combustion was studied over supported Pt-Sn bimetallic catalysts. A catalytic test for normal dehydrogenation was also carried out as part of the proposed process. Pt/Al2O3 modified with Sri and Zn was found to be suitable for both of these two reactions. In the normal dehydrogenation, conversions equal to the calculated equilibrium conversion were achieved with almost complete selectivity for propylene. Optimization of catalyst composition was done by addition of various amounts of Sri to Pt/Al2O3 and Pt/Zn-Al-O. For dehydrogenation combined with hydrogen combustion, selective hydrogen combustion was achieved over Pt-Sn bimetallic catalysts. Moreover, a stable conversion higher than that of equilibrium for normal dehydrogenation was obtained using Pt-Sn/Zn-Al-O under certain reaction conditions. (C) 2008 Elsevier B.V. All rights reserved.

The alpha-diimine nickel (II) complexes immobilized into the clay mineral interlayer were prepared by the reaction of the Ni2+ ion-exchanged fluorotetrasilicic mica and the alpha-diimine ligand. These procatalysts showed a high catalytic activity for the Slurry, polymerization of ethylene in the presence of methylalumoxane, triethylaluminum or triisobutylaluminum. The activity was strongly affected by the solvent used in the preparation and the steric bulk of the ligand. A high activity (2313 kg-PE mol-Ni-1 h(-1)) was obtained by the polymerization at 50 degrees C in the presence of triisobutylaluminum Using the procatalyst prepared with the [Ar-N = C(CH3)C(CH3)= N-Ar (At = 2,6-C6H3(CH3)(2))] ligand in acetonitrile. (C) 2008 Elsevier B.V. All rights reserved.

The liquid phase hydrogenation of naphthalene was performed in the presence of CO over a commercial Ni/SiO2-Al2O3 catalyst. Naphthalene was hydrogenated even in the presence of CO at elevated temperatures, accompanying the hydrogenation of CO. Two activation energy values were obtained for the naphthalene hydrogenation depending on the reaction temperature. FT-IR measurement of the adsorbed CO was also carried out. Hydrogenation of the adsorbed CO created sites active for naphthalene hydrogenation.

The promoting effects of halogen ions (Cl − , Br − , I − ) on catalytic activity and selectivity in the hydrogenation of (E)-2-butenal to form (E)-2-buten-1-ol were investigated using alumina-supported cobalt catalyst in a liquid phase. The addition of Cl − or Br − to the reaction media greatly promoted the formation of (E)-2-buten-1-ol and simultaneously suppressed the formation of butanal, whereas the addition of I − prevented C C bond hydrogenation. The promoting effects increased with increasing electronegativity of the halogen atoms. The rate ratio of C O bond hydrogenation to C C bond hydrogenation was increased eightfold when Cl − was used under optimum conditions.

Hydrogenation of naphthalene over Pd/TiO2 and Pd/Al2O3 catalysts in the presence of dimethyldisulfide (DMDS) was performed in a batch reactor at 473 K and 2.45 MPa; the two catalysts were compared in detail in terms of sulfur tolerance. As compared with Pd/Al2O3, Pd/TiO2 showed high turnover frequency (TOF) and sulfur tolerance, in both the presence of dimethyldisulfide (DMDS) and the absence of DMDS. PdS bond strength was determined by temperature-programmed reduction of sulfide catalysts (H2S-TPR) profiles and CO uptake after H2 reduction of sulfided catalyst at various temperatures. The results show that desorption of H2S from sulfided Pd/TiO2 occurs at 553 K, whereas desorption of H2S from sulfided Pd/Al2O3 requires a higher temperature (773 K), indicating that the PdS bond in Pd/TiO2 is significantly weaker than that in Pd/Al2O3. Furthermore, the H2S-TPR profiles of Pd/TiO2 reduced at 573–773 K clearly indicate that the PdS bond in Pd/TiO2 reduced at 573 K is weak, whereas reduction at high temperature (SMSI state) strengthened the PdS bond. The high temperature reduction may result in formation of Ti3+ surrounding the Pd metals and spoil the catalytic activity. Therefore, the presence of Ti4+, which has a high electronegativity, is concluded to weaken the PdS bond and to be an important factor for high sulfur tolerance.

TiO2およびAl2O3担持バイメタリックPt-Pd触媒によるナフタレン水素化反応を, ジメチルジスルフィド (DMDS) を添加した場合および添加しない場合において, 0.95～2.45 MPa, 473 Kで行った。さらに, 吸着したCOの赤外吸収スペクトルにより調製した触媒の物性評価を行った。担持Pt触媒と比較すると, 担持Pd触媒は硫黄化合物が存在する条件下で高い触媒活性を示した。硫黄化合物が存在しない場合には, Pt触媒はPd触媒よりも高活性であることから, Pd触媒はより高い耐硫黄性を有していることを示していた。PtとPdを共存させると, 硫黄化合物存在下での触媒活性が大幅に向上し, 明らかな複合効果を示した。しかしながら, 硫黄化合物が存在しない場合, 顕著な複合効果は発現しなかった。さらに, Pd/(Pt + Pd) モル比は, それぞれAl2O3担持触媒0.8, TiO2担持触媒で0.5であった。これらの最適値の違いは, 金属粒子径の影響に帰属された。バイメタリック触媒に吸着したCOの赤外吸収スペクトルはPt-Pdバイメタリック粒子の形成を示した。しかしながら, PtとPd間での電子的な相互作用は見られなかった。よって, PtとPdの複合効果は幾何学的効果に帰属された。

Hydrogenation of naphthalene was performed over supported Pd catalysts prepared from precursors that contained Cl − and from precursors that were free of Cl − . The activity of catalyst prepared from PdCl 2 was much higher than that prepared from Pd(NH 3 ) 2 (NO 2 ) 2 . The species of Pd precursor strongly affected the activity of Pd/Al 2 O 3 , whereas no significant influence was observed in the effect of Pd/SiO 2 , because residual Cl − was easily removed by calcination and/or reduction. Catalytic activity was increased by addition of NH 4 Cl to Cl − -free Pd/Al 2 O 3 . Residual Cl − was concluded to enhance the catalytic activity of the supported Pd catalysts.

To clarify the mechanism of naphthalene hydrogenation to cis - and trans -decahydronaphthalene (decalins) via tetrahydronaphthalene (tetralin), the rate of naphthalene hydrogenation was compared with those of tetralin and tetralin containing 3–10 mol% naphthalene over a TiO 2 -supported Pt catalyst. Tetralin was hydrogenated to decalins readily, while the naphthalene hydrogenation did not take place under the same reaction conditions (433 K and 2.96 MPa). When 3–10 mol% naphthalene was added to tetralin, the rate of hydrogenation decreased clearly with an increase of naphthalene content. The observation suggests that naphthalene interacts with surface metals strongly and prevents the hydrogenation of tetralin.

[SbCl6]2- was formed in the flash photolysis of [SbCl6]3- or [SbCl6]- in both solutions of CH3CN and CHCl3 in the presence of an excess of chloride. [SbCl6]2- had absorption maxima at 293, 328, and 390 nm in CH3CN. A similar absorption spectrum of [SbCl6]2- was also obtained in CHCl3. The lifetime of [SbCl6]2- was much shorter in CHCl3 than in CH3CN. [SbCl6]- was easily reduced to [SbCl6]3- upon continuous UV-irradiation in CH3CN as well as in CHCl3. On the other hand, [SbCl6]3- was oxidized to [SbCl6]- in CHCl3 in the presence of oxygen, but was not in CH3CN. The spectrum and the decay rate of [SbCl6]2- were not essentially affected by oxygen in both solutions of CH3CN and CHCl3.

Supported catalysts prepared by an impregnation method using the bis(imino)pyridineiron(II) complex and clay minerals (montmorillonite, fluorotetrasilicic mica, and saponite) were used for ethylene polymerization. The activities of the montmorillonite- and saponite-based catalysts were much higher than that of the mica-based one.

A drastic synergistic effect has been found for the liquid-phase hydrogenation of aromatic hydrocarbons by the combination of Pt and Ru. The surface composition of Pt–Ru/SiO2 was estimated using O2...

The influence of residual chloride ions on the catalytic activity of Co/Al2O3 was investigated for liquid-phase hydrogenation of ketones and aldehydes using Cl−-free and Cl−-containing catalysts. T...

Ethylene polymerization was performed using bis(n-butylcyclopentadienyl)zirconium dichloride ((n-BuCp)2ZrCl2) supported on alumina- and titania-based acidic oxides (Al2O3, TiO2, AlPO4, TiO2–Al2O3, SiO2–Al2O3, TiO2–SiO2 and H–Y zeolite) in the presence of triisobutylaluminum. These oxides were also tested in an isopropylbenzene cracking reaction to determine their acid properties. Among the catalysts, AlPO4-supported (n-BuCp)2ZrCl2 showed the highest polyethylene productivity, but AlPO4 was inactive in the cracking reaction. FT-IR spectra of pyridine-adsorbed AlPO4 and Al2O3 indicated that the acid sites do not participate in active-site formation. It is possible that the metallocene is activated on sites formed by the reaction of characteristic OH groups of AlPO4 with triisobutylaluminum.

Dehydrogenation of ethylbenzene (EB) was examined in the presence of CO2, and the effect of CO2 on Fe2O3, Fe–Ce, Fe–K, and Fe–Ce–K oxide catalysts was evaluated. The rate equation was derived in relation to the Langmuir–Hinshelwood mechanism. The rate constant (k) and the relative adsorption coefficient (\( Z_{{{\text{CO}}_{2} }} \)) were obtained, and it was found that addition of K in the catalyst increased both k and \( Z_{{{\text{CO}}_{2} }}.\) We found that CO2 had a strong affinity for the catalyst surface and that the active sites were basic.

Ethylene was polymerized at 60 °C and 0.7 MPa using catalysts supporting Cp 2 ZrCl 2 on cation-exchanged montmorillonites as an activator. The supported catalysts consisting of Cp 2 ZrCl 2 and alkali metal ion-exchanged montmorillonites showed very low activity for ethylene polymerization. When Cp 2 ZrCl 2 supported on montmorillonites exchanged with H + , Mg 2+ , and Cu 2+ ions were used in the polymerization, polyethylene was obtained at high yields. The catalytic activity of Cp 2 ZrCl 2 supported on Mg 2+ -mont, 1.2 x 10 4 kg-PE.mol-Zr -1 .h, was determined from the polyethylene yield and the amount of Zr supported.

Hydrogenation activity of aromatic hydrocarbons was remarkably increased when the residual chlorine on Ru/Al2O3 and Ru/SiO2 was removed by washing. On the basis of FT-IR spectra in the CO region, a...