Study of benzene hydrogenation catalyzed by nickel supported on alumina in a fixed bed reactor

The Ni/Al₂O₃ catalysts were prepared for studying benzene hydrogenation. It was observed that the activity for Ni loading under 5% is very low due to the formation of nickel aluminate (spinel) in low nickel loading. It has been found that Ni/Al₂O₃ systems exhibit SMSI (strong-metal support interaction) to a much lesser extent. It could be concluded that the hydrogenation of benzene on supported Ni catalysts is a structure insensitive reaction.     

The catalytic performance of different promoted iron catalysts on combined supports Al<Subscript>2</Subscript>O<Subscript>3</Subscript> for carbon dioxide hydrogenation

Global warming, fossil fuel depletion and fuel price increases have motivated scientists to search for methods for the storage and reduction of the amount of greenhouse gases, especially CO₂. The hydrogenation process has been introduced as an emerging method of CO₂ capture and convertion into value-added products. In this study, new types of catalysts are introduced for CO₂ hydrogenation and are compared based on catalytic activity and product selectivity. The physical properties of the samples are specified using BET. Iron catalysts supported on γ-Al₂O₃ with different metal promoters (X = Ni, K, Mn, Cu) are prepared through the impregnation method. Moreover, Fe–Ni catalysts supported on HZSM5-Al₂O₃ and Ce–Al₂O₃ are synthesized. Samples are reduced by pure H₂ and involved in hydrogenation reaction in a fixed bed reactor (H₂/CO₂ = 3, total pressure = 10 MPa, temperature = 523 K, GHSV = 2000, 1250 nml/min). All catalysts provide high conversion in hydrogenation reactions and the results illustrate that the selectivity of light hydrocarbons is higher than that of methane and CO. It is found that Ni has a promoting effect on the conversion fluctuations throughout the reaction with 66.13% conversion. Using combined supported catalysts leads to enhancing catalytic performance. When Fe–Ni/γ–Al₂O₃—HZSM5 is utilized, CO₂ conversion is 81.66% and the stability of the Fe–Ni catalyst supported on Al₂O₃ and Ce–Al₂O₃ furthey improves.     

Characterization and Activity of Cu‐MnOx/γ‐Al2O3 Catalyst for Hydrogenation of Carbon Dioxide

The effect of manganese on the dispersion, reduction behavior and active states of surface of supported copper oxide catalysts have been investigated by XRD, temperature‐programmed reduction and XPS. The activity of methanol synthesis from CO₂/H₂ was also investigated. The catalytic activity over CuO‐MnO_x/γ‐Al₂O₃ catalyst for CO₂ hydrogenation is higher than that of CuO/γ‐Al₂O₃. The adding of manganese is beneficial in enhancing the dispersion of the supported copper oxide and make the TPR peak of the CuO‐MnK_x/γ‐Al₂O₃ catalyst different from the individual supported copper and manganese oxide catalysts, which indicates that there exists strong interaction between the copper and manganese oxide. For the CuO/γ‐Al₂O₃ catalyst there are two reducible copper oxide species; α and β peaks are attributed to the reduction of highly dispersed copper oxide species and bulk CuO species, respectively. For the CuO‐MnO_x/γ‐Al₂O₃ catalyst, four reduction peaks are observed, α peak is attributed to the dispersed copper oxide species; β peak is ascribed to the bulk CuO; γ peak is attributed to the reduction of high dispersed CuO interacting with manganese; δ peak may be the reduction of the manganese oxide interacting with copper oxide. XPS results show that Cu⁺ mostly existed on the working surface of the Cu‐Mn/γ‐Al₂O₃ catalysts. The activity was promoted by Cu with positive charge which was formed by means of long path exchange function between Cu? O? Mn. These results indicate that there is synergistic interaction between the copper and manganese oxide, which is responsible for the high activity of CO₂ hydrogenation.     

Catalysis for One‐step Synthesis of Dimethyl Ether from Hydrogenation of CO

In this paper, a new catalyst system Cu‐Mn‐(M)/γ‐Al₂O₃ was developed for the directly synthesis dimethyl ether (DME) from synthesis gas in a fixed‐bed reactor. The catalysts with different n (Cu) : n (Mn) ratios, several promoter M (M is one of Zn, Cr, W, Mo, Fe, Co or Ni) were prepared and tested. The results showed the catalysts have a high conversion of CO and a high DME selectivity. The DME yield in tail gas reached 46.0% (at 63.27% conversion of CO) at 2.0 MPa, 275°C, 1500 h^?1 with the Cu₂Mn₄Zn/γ‐Al₂O₃ catalyst.     

Adducts of nickel(II) acetylacetonate chelating with heterocyclic bases: 3‐­cyanopyridine and 4‐cyanopyridine

In both title compounds, (acetyl­acetonato‐O,O′)­bis(3‐cyano­pyridine‐N)­nickel(II), (I), and (acetyl­acetonato‐O,O′)­bis(4‐cyanopyridine‐N)­nickel(II), (II), both [Ni(C₅­H₇O₂)₂(C₆H₄N₂)₂], the Ni^II atom, which is situated on a centre of symmetry, is octahedrally coordinated. Distances and angles for (I) and (II), respectively, are: Ni—O 2.009 (2)/2.016 (2) and 2.0110 (16)/2.0238 (18) Å, Ni—N 2.116 (3) and 2.179 (2) Å, O—Ni—O 91.86 (10) and 90.19 (7)°, and O—Ni—N 91.27 (11)/90.19 (11) and 89.65 (8)/90.79 (7)°.     

An Effect of a Support Nature and Active Phase Morphology on Catalytic Properties of Ni-Containing Catalysts in Hydrogenation of Biphenyl

Ni/Sup catalysts were prepared, where SBA-15, γ-Al₂O₃, SiO₂ were used as supports (Sup). The synthesized catalysts were investigated by the methods of low-temperature nitrogen adsorption, temperatureprogrammed reduction (TPR), and high-resolution transmission electron microscopy. The catalytic properties of the prepared catalysts were tested in liquid phase hydrogenation of biphenyl under conditions of a flow installation at temperatures of 60–100°C, pressure of 4 MPa, volumetric feed rate of 4–10 h^–1 and H₂: feed ratio of 1500 nM.. A 1 wt % solution of biphenyl in heptane,, as a model mixture, was used. It has been established that the activity of nickel hydrogenation catalysts depends on the nickel content and the type of support. The activity of supported nickel catalysts decreases in the series Ni-12/SBA-15 > Ni-12/SiO₂ >> Ni-12/Al₂O₃. The kinetic characteristics of the biphenyl hydrogenation reaction were determined: the rate constants and activation energy for the hydrogenation of the first and second aromatic rings of the substrate molecule.     

A Heterogeneous‐Catalyst‐Based,Microwave‐Assisted Protocol for the Synthesis of 2,2′‐Bipyridines

A new method of preparing 2,2′‐bipyridines with short reaction times by using microwave assistance and heterogeneous catalysts has been developed. With a Negishi‐like protocol, it was found that Ni/Al₂O₃–SiO₂ afforded 2,2′‐bipyridine products in up to 86 % yield in 1 h. Palladium supported on alumina also provided yields of 2,2′‐bipyridines comparable to those seen for homogeneous PEPPSI^TM (1,3‐diisopropylimidazol‐2‐ylidene)(3‐chloropyridyl)palladium(II)dichloride) and tetrakis(triphenylphosphanyl)palladium complexes.     

Initiation behaviour in hydrogenation of pyrolysis gasoline over presulphided Ni-Mo-Zn/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst

A presulphided treatment was applied to the oxidic Ni-Mo-Zn/Al₂O₃ catalyst (nickel catalyst) in order to avoid thermal run-away during initiation of the hydrogenation of pyrolysis gasoline. The physico-chemical properties of the prepared oxidic nickel catalyst, the reduced and passivated (RP) nickel catalyst and the sulphided (RPS) nickel catalyst were characterised using N₂ adsorption-desorption, X-ray diffraction, temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). The TPR results showed that the reducibility of the RP Ni-Mo-Zn/Al₂O₃ catalyst was improved over the oxidic nickel catalyst. The XPS spectra confirmed the binding energy of the RPS nickel catalyst to be higher than that of the oxidic nickel catalyst. The catalytic performance was evaluated on a fixed-bed reactor (reaction temperature between 30 °C and 70°C, at 2.8 MPa of total pressure and weight hourly space velocity of 2.0 h^?1, the volume of H₂/pyrogasoline = 200: 1). The rising temperature of the RPS nickel catalyst was almost 20°C lower than that of the oxidic nickel catalyst during the initial stage of the hydrogenation reaction. The results indicated that the RPS nickel catalyst exhibited better stability than the oxidic nickel catalyst during the start-up period, thereby providing a better selectivity in long-term operation.     

Time‐Resolved,In Situ DRIFTS/EDE/MS Studies on Alumina‐Supported Rhodium Catalysts: Effects of Ceriation and Zirconiation on Rhodium–CO Interactions

The effects of ceria and zirconia on the structure–function properties of supported rhodium catalysts (1.6 and 4 wt % Rh/γ‐Al₂O₃) during CO exposure are described. Ceria and zirconia are introduced through two preparation methods: 1) ceria is deposited on γ‐Al₂O₃ from [Ce(acac)₃] and rhodium metal is subsequently added, and 2) through the controlled surface modification (CSM) technique, which involves the decomposition of [M(acac)_x] (M=Ce, x=3; M=Zr, x=4) on Rh/γ‐Al₂O₃. The structure–function correlations of ceria and/or zirconia‐doped rhodium catalysts are investigated by diffuse reflectance infrared Fourier‐transform spectroscopy/energy‐dispersive extended X‐ray absorption spectroscopy/mass spectrometry (DRIFTS/EDE/MS) under time‐resolved, in situ conditions. CeO_x and ZrO₂ facilitate the protection of Rh particles against extensive oxidation in air and CO. Larger Rh core particles of ceriated and zirconiated Rh catalysts prepared by CSM are observed and compared with Rh/γ‐Al₂O₃ samples, whereas supported Rh particles are easily disrupted by CO forming mononuclear Rh geminal dicarbonyl species. DRIFTS results indicate that, through the interaction of CO with ceriated Rh particles, a significantly larger amount of linear CO species form; this suggests the predominance of a metallic Rh phase.     

Pentacoordinated Al3+‐Stabilized Active Pd Structures on Al2O3‐Coated Palladium Catalysts for Methane Combustion

Supported Pd catalysts are active in catalyzing the highly exothermic methane combustion reaction but tend to be deactivated owing to local hyperthermal environments. Herein we report an effective approach to stabilize Pd/SiO₂ catalysts with porous Al₂O₃ overlayers coated by atomic layer deposition (ALD). ²⁷Al magic angle spinning NMR analysis showed that Al₂O₃ overlayers on Pd particles coated by the ALD method are rich in pentacoordinated Al³⁺ sites capable of strongly interacting with adjacent surface PdO_x phases on supported Pd particles. Consequently, Al₂O₃‐decorated Pd/SiO₂ catalysts exhibit active and stable PdO_x and Pd–PdO_x structures to efficiently catalyze methane combustion between 200 and 850 °C. These results reveal the unique structural characteristics of Al₂O₃ overlayers on metal surfaces coated by the ALD method and provide a practical strategy to explore stable and efficient supported Pd catalysts for methane combustion.     

Hydrogenating Activity and Adsorption Capacity of Supported Nickel Catalysts Modified by Heteropoly Compounds

The catalytic activity, adsorption capacity, and pore structure of low-percentage nickel catalysts supported on -Al₂O₃or activated carbon and modified by tungsten heteropoly compounds are studied. The activity, selectivity, and thermal stability of the catalysts in the vapor-phase hydrogenation of olefins and aromatic hydrocarbons are higher than those for conventional nickel catalysts. The concentration of nickel in the catalysts is 10–15 times lower than that in commercial catalysts. However, the modified catalysts have higher specific surface areas of metal, higher dispersion, a uniform distribution of metal particles, and a pore-radius distribution other than in the support. The study of water adsorption and desorption showed that the heteropoly compound modifying the -Al₂O₃support covers the support surface completely, and supported nickel interacts with the active surface of the modifying agent rather than with Al₂O₃. A hydrogenation mechanism is proposed, which involves H₂dissociation on Ni particles and the subsequent diffusion of hydrogen atoms via a spillover mechanism to the adsorbed organic compound with the participation of the OH groups of the modifying agent.     

Retroracemization using new forms of Belokon's original ligand: ­intermediate NiII complexes of N‐({2‐[N‐(S)‐alkylprolylamino]phenyl}phenylmethylene)‐(S)‐phenylalanine (alkyl is 2‐picolyl, 3‐picolyl or ethyl)

In the title compounds, [N‐(phenyl{2‐[N‐(S)‐(2‐picolyl)­prolyl­amino]­phenyl}methyl­ene)‐(S)‐phenyl­alaninato]­nickel(II), [Ni(C₃₃H₃₀N₄O₃)], (I), [N‐(phenyl{2‐[N‐(S)‐(3‐picolyl)­prolyl­amino]­phenyl}methyl­ene)‐(S)‐phenyl­alaninato]­nickel(II) hemihydrate, [Ni(C₃₃H₃₀N₄O₃)]·0.5H₂O, (II), and [N‐({2‐[N‐(S)‐ethyl­prolyl­amino]­phenyl}phenyl­methyl­ene)‐(S)‐phenyl­ala­nin­ato]­nickel(II), [Ni(C₂₉H₂₉N₃O₃)], (III), the Ni^II centres have approximate square‐planar coordination geometries from N₃O donor sets. The picolyl N atoms in (I) and (II) are too remote from the metal centres to interact significantly, but the metal coordination geometries experience tetrahedral distortion and/or displacement of the metal centre from the N₃O plane. These are linked to conformational differences between the ligands of the symmetry‐independent complexes (Z′ = 2), which in turn are related to molecular packing. In (III), where a less sterically demanding ethyl group replaces the picolyl substituents, there are none of the distortions or displacements seen in (I) and (II).     

Novel Flower‐Like Ag‐SiO2‐MgO‐Al2O3 Material: Preparation,Characterization and Catalytic Application in Methanol Dehydrogenation

Catalytic direct dehydrogenation of methanol to formaldehyde was carried out over Ag‐SiO₂‐MgO‐Al₂O₃ catalysts prepared by sol‐gel method. The optimal preparation mass fractions were determined as 8.3% MgO, 16.5% Al₂O₃ and 20% silver loading. Using this optimum catalyst, excellent activity and selectivity were obtained. The conversion of methanol and the selectivity to formaldehyde both reached 100%, which were much higher than other previously reported silver supported catalysts. Based on combined characterizations, such as X‐ray diffraction (XRD), scanning electronic microscopy (SEM), diffuse reflectance ultraviolet‐visible spectroscopy (UV‐Vis, DRS), nitrogen adsorption at low temperature, temperature programmed desorption of ammonia (NH₃‐TPD), desorption of CO₂ (CO₂‐TPD), etc., the correlation of the catalytic performance to the structural properties of the Ag‐SiO₂‐ MgO‐Al₂O₃ catalyst was discussed in detail. This perfect catalytic performance in the direct dehydrogenation of methanol to formaldehyde without any side‐products is attributed to its unique flower‐like structure with a surface area less than 1 m²/g, and the strong interactions between neutralized support and the nano‐sized Ag particles as active centers.     

Conformational analysis of the disaccharide methyl α‐d‐mannopyranosyl‐(1→3)‐2‐O‐acetyl‐β‐d‐mannopyranoside monohydrate

The crystal structure of methyl α‐d ‐mannopyranosyl‐(1→3)‐2‐O‐acetyl‐β‐d ‐mannopyranoside monohydrate, C₁₅H₂₆O₁₂·H₂O, ( II ), has been determined and the structural parameters for its constituent α‐d ‐mannopyranosyl residue compared with those for methyl α‐d ‐mannopyranoside. Mono‐O‐acetylation appears to promote the crystallization of ( II ), inferred from the difficulty in crystallizing methyl α‐d ‐mannopyranosyl‐(1→3)‐β‐d ‐mannopyranoside despite repeated attempts. The conformational properties of the O‐acetyl side chain in ( II ) are similar to those observed in recent studies of peracetylated mannose‐containing oligosaccharides, having a preferred geometry in which the C2—H2 bond eclipses the C=O bond of the acetyl group. The C2—O2 bond in ( II ) elongates by ～0.02 Å upon O‐acetylation. The phi (?) and psi (ψ) torsion angles that dictate the conformation of the internal O‐glycosidic linkage in ( II ) are similar to those determined recently in aqueous solution by NMR spectroscopy for unacetylated ( II ) using the statistical program MA′AT, with a greater disparity found for ψ (Δ = ～16°) than for ? (Δ = ～6°).     

Vapor‐Phase Aldolization of n‐Butyraldehyde to 2‐Ethyl‐2‐Hexenal over Solid‐Base Catalysts

Vapor‐phase aldol condensation of n‐butyraldehyde to 2‐ethyl‐2‐hexenal was studied at 1 atm and 150～ 300°C in a fixed‐bed, integral‐flow reactor by using NaX, KX, γ‐Al₂O₃ and Na/NaOH/γ‐Al₂CO₃ catalysts. Ion exchange of NaX zeolite with potassium acetate solution results in a decrease of crystallinity and apparent lowering of surface area, whereas the basic strength is enhanced. Treatment of γ‐Al₂O₃ with NaOH and Na causes a large decrease of the surface area but strong enhancement of the catalyst basicity. The catalytic activity on the basis of unit surface area is in the order Na/NaOH/γ‐Al₂O₃ < KXU < KXW < NaX >γ‐Al₂O₃, in accordance with the relative catalyst basic strength. The molar ratio of trimeric to dimeric products increases with increasing the reaction temperature and the catalyst basic strength except for Na/NaOH/γ‐Al₂O₃. Very high selectivity of 2‐ethyl‐2‐hexenal (>98.5%) was observed for reactions over NaX zeolite at 150°C. Based on the FT‐IR and the catalytic results, the reaction paths are proposed as follows: self‐aldol condensation of n‐butyraldehyde, followed by dehydration produces 2‐ethyl‐2‐hexenal, which then reacts with n‐butyraldehyde and successively dehydrates to 2,4‐diethyl‐2,4‐octadienal and 1,3,5‐triethylbenzene. For the reaction over NaX, the calculated Arrhenius frequency factor and activation energy are 314 mol/g·h and 32.6 kJ/mol, respectively.     

Structural Characterization of Alumina‐Supported Rh Catalysts: Effects of Ceriation and Zirconiation by using Metal–Organic Precursors

The effects of the addition of ceria and zirconia on the structural properties of supported rhodium catalysts (1.6 and 4 wt % Rh/γ‐Al₂O₃) are studied. Ceria and zirconia are deposited by using two preparation methods. Method I involves the deposition of ceria on γ‐Al₂O₃ from Ce(acac)₃, and the rhodium metal is subsequently added, whereas method II is based on a controlled surface reaction technique, that is, the decomposition of metal–organic M(acac)_x (in which M=Ce, x=3 and M=Zr, x=4) on Rh/γ‐Al₂O₃. The structures of the prepared catalyst materials are characterized ex situ by using N₂ physisorption, transmission electron microscopy, high‐angle annular dark‐field scanning transmission election microscopy, energy‐dispersive X‐ray spectroscopy, X‐ray photoelectron spectroscopy (XPS), and X‐ray absorption fine structure spectroscopy (XAFS). All supported rhodium systems readily oxidize in air at room temperature. By using ceriated and zirconiated precursors, a larger rhodium‐based metallic core fraction is obtained in comparison to the undoped rhodium catalysts, suggesting that ceria and zirconia protect the rhodium particles against extensive oxidation. XPS results indicate that after the calcination and reduction treatments, a small amount of chlorine is retained on the support of all rhodium catalysts. EXAFS analysis shows significant Rh? Cl interactions for Rh/Al₂O₃ and Rh/CeO_x/Al₂O₃ (method I) catalysts. After reaction with H₂/He in situ, for series of samples with 1.6 wt % Rh, the EXAFS first shell analysis affords a mean size of approximately 30 atoms. A broader spread is evident with a 4 wt % rhodium loading (ca. 30–110 atoms), with the incorporation of zirconium providing the largest particle sizes.     

Multiply Confined Nickel Nanocatalysts Produced by Atomic Layer Deposition for Hydrogenation Reactions

To design highly efficient catalysts, new concepts for optimizing the metal–support interactions are desirable. Here we introduce a facile and general template approach assisted by atomic layer deposition (ALD), to fabricate a multiply confined Ni‐based nanocatalyst. The Ni nanoparticles are not only confined in Al₂O₃ nanotubes, but also embedded in the cavities of Al₂O₃ interior wall. The cavities create more Ni–Al₂O₃ interfacial sites, which facilitate hydrogenation reactions. The nanotubes inhibit the leaching and detachment of Ni nanoparticles. Compared with the Ni‐based catalyst supported on the outer surface of Al₂O₃ nanotubes, the multiply confined catalyst shows a striking improvement of catalytic activity and stability in hydrogenation reactions. Our ALD‐assisted template method is general and can be extended for other multiply confined nanoreactors, which may have potential applications in many heterogeneous reactions.     

Preparation,Solid‐state Characteristics,and Catalytic Properties of Promoted Vanadium Phosphate Materials

The syntheses of transition metal promoted (M = Co, Cr, Fe, Mo) supported vanadium phosphate (VPO) catalysts (TiO₂ (anatase), γ‐Al₂O₃) and their characterization by N₂‐adsorption, X‐ray diffractometry (XRD), FTIR‐spectroscopy and determination of V‐valence state is reported. The catalytic properties were checked in the heterogeneous catalytic ammoxidation of 2, 6‐dichlorotoluene to the corresponding nitrile. The catalyst samples were prepared by synthesis of the precursor compound VOHPO₄ · 0.5 H₂O, impregnation using various metal salt solutions and mixing with the support materials. The characterization revealed increased surface areas for all the promoted samples in comparison to the basic materials. XRD showed the formation of (VO)₂P₂O₇ after calcinations as well as patterns of support materials (anatase, γ‐Al₂O₃). The formation of crystalline proportions of mixed oxides were not observed. The catalytic ammoxidation runs revealed a significant effect of the promoter metals on the catalytic properties by an increase of yield by ca. 20 % compared to bulk VPO. Almost complete conversion of 2, 6‐dichlorotoluene and 81 % yield of nitrile were observed using a 25 %VPCoO/γ‐Al₂O₃ catalyst.     

Formation of a supported cobalt catalyst for the synthesis of carbon nanofibers on aluminum oxide

Comparative studies of the effect of the physicochemical characteristics of a support (aluminum oxide) on the formation of a supported Co catalyst and its activity in the pyrolysis of alkanes (propane-butane) were performed. The effect of the crystalline modification of alumina on the yield of catalytic filamentous carbon (CFC) ((g CFC)/(g Co)) was studied. The surface morphologies of Co-containing catalysts and synthesized carbon deposits were studied by scanning electron microscopy. It was found that carbon deposits with a well-defined nanofiber structure were synthesized by the pyrolysis of a propane-butane mixture in the presence of hydrogen at 600°C on supported Co catalysts prepared by homogeneous precipitation on macroporous corundum (α-Al₂O₃). The yield of CFC was no higher than 4 (g CFC)/(g Co). On the Co catalyst prepared by homogeneous precipitation on mesoporous Al₂O₃, the intense carbonization of the initial support; the formation of cobalt aluminates; and, as a consequence, the deactivation of Co⁰ as a catalyst of FC synthesis occurred. The dependence of the yield of CFC on the preheating temperature (from 200 to 800°C) of Co catalysts before pyrolysis was studied. It was found that, as the preheating temperature of supported Co/Al₂O₃ catalysts was increased, the amount of synthesized carbon, including CFC, decreased because of Co⁰ deactivation due to the interaction with the support and coke formation.     

Oxidative coupling polymerization of 2,3‐dihydroxynaphthalene with dinuclear‐type copper(II) catalyst

The oxidative coupling polymerization of 2,3‐dihydroxynaphthalene with the novel dinuclear‐type copper(II) catalysts successfully produced poly(2,3‐dihydroxy‐1,4‐naphthylene). For example, the MeOH‐insoluble polymer with a number average molecular weight of 4.4 × 10³ from the polymerization using the complex of CuCl₂ and N,N′‐bis(2‐morpholinoethyl)‐p‐xylylenediamine ( p ‐ 1 ) at room temperature under an O₂ atmosphere followed by acetylation of the hydroxyl groups was obtained in 63% yield. The structures of the tetraamine ligands and the counter anion of the copper(II) salts significantly influenced the catalyst activity. The polymerization of 2,2′‐dimethoxy‐1,1′‐binaphthalene‐3,3′‐diol with the 2CuCl₂‐ p ‐ 1 catalyst, however, resulted in a lower yield. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1635–1640, 2005