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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.

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.

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.

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.

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.