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Catalyst systems for the gas-phase oxycarbonylation of methanol often suffer from low catalyst activities and strong catalyst deactivation. In this work, the continuous gas-phase oxycarbonylation of methanol was realized by using Supported Ionic Liquid-Phase (SILP) catalysts. Copper(I) bromide dissolved in various ionic liquids and dispersed on Polymer-Based Spherical Activated Carbon (PBSAC) as supporting material was found to be an active catalyst. The poor activity and stability of copper halide catalysts reported in literature was substantially increased by the presence of ionic liquids. In particular, trioctylmethylammonium bromide in combination with a basic salt additive increased the activity of the CuBr catalyst and led to comparatively stable SILP catalyst operation reaching a total turnover number of 600 over 50 h time-on-stream.

The development of mild and efficient process for the selective oxidation of organic compounds with molecular oxygen can be one of the key technologies for synthesizing oxygenates. Here, a visible light-driven metal chloride to catalyze the selective oxidation of cyclohexane was carried out at ambient temperature under a pure O2 atmosphere. Among the metal salts examined, only a few metal chlorides, with easily changeable valence, such as CuCl2·2H2O, VOCl3, and FeCl3·6H2O, were found to be active to this photo-oxidation reaction in acetonitrile or acetone, providing cyclohexanol, cyclohexanone, chlorocyclohexane, and cyclohexene as main products. This is likely because the weak coordination of these metal chlorides with solvent molecules plays key roles in absorbing visible light and realizing photoredox cycle, as supported by UV–Vis spectrum and cyclic voltammetry measurements. Among these active metal chlorides, CuCl2·2H2O showed a higher conversion and better selectivity for cyclohexanol and cyclohexanone (the oxygenated products) than the other two metal chlorides, and its activity and selectivity for chlorocyclohexane were significantly improved in the case of adding concentrated HCl, because HCl promotes the photocatalytic cycling, as supported by UV–Vis spectra. Notably, a high turnover frequency (TOF, 7.4 h−1) and an excellent selectivity for the oxygenated products (93%) were achieved upon a low concentration of CuCl2·2H2O (0.002 mol L−1), 0.1 ml of concentrated HCl and 2 atm of O2 pressure. Based on these findings, a free radical mechanism for the present photocatalysis system was proposed.

An improved procedure, three-step reaction cycle procedure, for the continuous preparation of phosgene from CO, air and HCl catalyzed by CuCl2 was reported for the first time. The corresponding catalytic mechanism of each step was preliminarily disclosed with the powder X-ray diffraction (XRD) analysis: the first step is the oxychlorination of CO to phosgene and simultaneous reduction of CuCl2 to CuCl; the second step is the oxidation of CuCl with air to Cu2OCl2, and the third step is the neutralization of Cu2OCl2 with HCl to CuCl2. The regeneration of catalyst consists of steps 2 and 3, which is called the two-step regeneration of catalyst. The no-simultaneous existence of Cu (I) chloride and water in this three-step reaction procedure prevented effectively copper (I) chloride from the disproportionation. The influence of regeneration conditions, including reaction time, pressure of air or HCl on morphologies and recovery degree of catalyst were investigated and discussed. The degree of recovery for the single-run yield and cumulative yield of phosgene from the two-step regenerated oxychlorination agent can reach, respectively, 87.0% and 97.0% whereas the single-run yield and cumulative yield of phosgene with the one-step regenerated catalyst only can be recovered to 58.8% and 80.5%, respectively. The two-step regeneration method also can result in a higher dispersion of CuCl2/KCl on silica gel than that of the one-step regeneration. These results not only can offer a quite promising potential for the industrial use, but also can promote our deeply understanding of this important industrial reaction.

Pd(II) chloride and Cu(II) chloride in various liquid polymer media supported on silica gel were prepared and used in a catalyst system for vapor-phase synthesis of acetaldehyde by Wacker-type oxidation of ethylene. This catalyst system supported on silica gel prepared by impregnation was quickly deactivated, while use of polyethylene glycol (PEG) as a liquid polymer medium supported on silica gel showed stable catalytic activity. PEG inhibited the formation of Pd metal particles, which deactivate the catalyst system. Addition of alkali metal salts, especially LiCl, to the PdCl2–CuCl2 catalyst system with PEG enhanced catalytic activity for 22 h, even when the Pd content was high, leading to high activity but poor stability. LiCl also inhibited the formation of metal particles.

Copper-loaded titania (Cu/TiO2) was synthesized via an improved modified sol–gel process. Photocatalysts were applied to the CO 2 photocatalytic reduction and the yield of the major product, methanol, was used to evaluate the photocatalytic performance. Copper precursors and the adding time with sol as well as posttreatments were studied to explore the relationships between the characteristics and the activity of the photocatalysts. The results revealed that Cu/TiO 2 prepared from copper chloride and added in the early sol–gel stage was more photoactive than that from copper acetate. Additional H2 reduction of calcined catalysts before the photoreduction CO2 decreased the yield of methanol due to the change of copper dispersion and oxidation state. TPR, XPS, and XAS measurements verified the oxidation state of Cu on Cu/TiO2 catalysts. The results indicated that the primary Cu(I) served as an active site. The zeta potentials of catalysts were measured and compared, showing that a higher positive zeta potential at pH 7 would lead to higher activity. Under 30-h UVC (254 nm) irradiation, the best catalyst gave a methanol yield above 600 µmol/gcat. Switching to UVA (365 nm) resulted in a significant decrease of methanol yield in the range of 10 µmol/gcat.

A complete catalytic cycle was performed on CuCl2/Al2O3 catalyst for ethylene oxychlorination at 500 K. X-ray absorption near-edge spectroscopy, extended X-ray absorption fine structure, electron paramagnetic resonance, and IR of adsorbed CO were used to demonstrate that the ethylene oxychlorination reaction, C2H4+2HCl+1/2 O2→C2H4Cl2+H2O, follows a three-step mechanism: (i) reduction of CuCl2 to CuCl (2CuCl2+C2H4→C2H4Cl2+2CuCl), (ii) oxidation of CuCl to give an oxychloride (2CuCl+1/2 O2→Cu2OCl2), and (iii) closure of the catalytic circle by rechlorination with HCl, restoring the original CuCl2 (Cu2OCl2+2HCl→2CuCl2+H2O). The dispersing/sintering effect of the different reagents on the active phase has been also investigated.

The effect of aging and heating treatments up to 500 K on alumina-supported CuCl2, i.e., the base catalyst for ethylene oxychlorination, has been investigated by UV‐vis spectroscopy, a solubility test, EXAFS, XRD, and EPR in a wide range (0.25‐9 wt%) of Cu concentration. It is shown that the catalyst undergoes significant changes with both time and thermal treatments, so accounting for some contradictory results reported in the literature. While the surface Cu aluminate (formed during impregnation) does not change upon aging and heating, supported CuCl2 (precipitated from impregnating solution during the drying process) undergoes a slow hydrolysis reaction with the formation of paratacamite and HCl. The HCl formed during the hydrolysis reacts with the alumina surface with the formation of >Al‐Cl species. Upon heating, the initially formed paratacamite can react with surface >Al‐Cl species with nearly total restoration of CuCl2, which is consequently the main species present on the catalyst at the beginning of the oxychlorination reaction. The obtained picture is able to explain the results emerging from activity tests on the whole set of catalysts, indicating that surface aluminate is not active and that the active phase is CuCl2. c ∞ 2000 Academic Press

Effects of copper phase on oxidation of carbon monoxide over supported Wacker-type catalysts were examined. XRD patterns and XANES spectra of the catalysts were measured to determine the bulk phase and the chemical environment of copper. The catalytic activity was affected by the composition of copper precursors, the nature of supports, the presence of HCl and SO 2 in the feed, and the reaction temperature. All these variables affecting the catalytic activity influenced the XRD intensity of Cu 2 Cl(OH) 3 phase in the same manner, which was believed to be the active copper phase of the catalyst. Thus the XRD intensity of Cu 2 Cl(OH) 3 of a catalyst was closely correlated with its catalytic activity and the change in the catalytic activity of CO oxidation with respect to different reaction and preparation conditions was directly related to the behavior of the active copper phase with respect to those variables.

The mobilities of active species in γ-Al2O3-supported CuCl2-KCl-LaCl3 at a low temperature typical of oxyhydrochlorination of ethylene (498 K) have been studied in a fluidized bed lab reactor. Copper chloride and KCI are mobile under reaction conditions and in a C2H4/N2 atmosphere, whereas LaCl3 is not. No mobility is observed in air or in HCl/air. It is suggested that the mobile species is cuprous. Mobility studies performed with catalysts supported on SiO2, α-Al2O3, and γ-Al2O3 in reducing atmospheres show that copper chloride is not mobile on SiO2 and α-Al2O3. Results of selective extractions with acetone, XRD, and TPR show that a strong salt-support interaction occurs in γ-Al2O3-, compared to α-Al2O3- and SiO2-supported copper chloride. Either promoter separates the CuCl2 from the γ-Al2O3, but does not affect the mobility of the species on this oxide. Lanthanum chloride increases the activity with no effect on the apparent activation energy. It counteracts the adverse effect of KCl which is not a promoter since it causes a decrease in the activity up to 525 K. The promotion of KCl occurs at higher temperatures. This behavior is due to an increase in the apparent activation energy with the addition of KCl.

Salt-support interactions have been studied on unpromoted CuCl2 catalysts supported on γ-Al2O3, TiO2, and SiO2. Selective extraction by solvents and thermal analysis have been used to probe the extent of interaction, which follows the sequence: Al2O3 > TiO2 > SiO2. It also increases with copper chloride dispersion. The experimental results can be explained in terms of the formation of a regenerable active phase on the support surface. This species is formed on Al2O3 and TiO2 but it is not on SiO2. The interacting phase can resist deactivation while the surface of the noninteracting particles is rapidly reduced to CuCl rending them inactive.

A modified supported molten-salt Wacker catalyst involving palladium chloride/copper chloride is developed by replacing the conventional aqueous reaction medium (H 2 O + HCl) with a eutectic melt of cuprous chloride and potassium chloride and supporting it on a porous support. Experimental studies for the oxidation of ethylene to acetaldehyde over the supported molten-salt catalyst (SMSC) show the kinetics to be similar to the aqueous-phase Wacker process and the SMSC diffusion-reaction characteristics to be well predicted by the theoretical model of R. Datta and R. G. Rinker ( J. Catal. 95 , 181 (1985)). The SMS catalyst was found to be extremely stable owing to the essentially nonvolatile nature of the molten salt whereas the aqueous-phase supported liquid-phase catalyst deactivated rapidly due to the evaporation of the solvent. The developed supported molten-salt catalyst appears to have substantial advantages over the commen⌝cal liquid-phase Wacker process. Further, the SMSC technique utilized here should prove to be useful in developing efficient catalysts for many other processes.

A supported liquid phase catalyst consisting of a copper chloride/potassium chloride mixture with or without cerium chloride and supported on either alumina or titania has been investigated using X-ray diffraction and transmission electron microscopy both with and without a heating stage. Catalysts used in an oxychlorination experiment have also been examined. X-Ray and TEM studies confirmed the existence of small clusters of active phase which were mobile at high temperatures and could coalesce to a greater or lesser extent depending upon the addition of cerium chloride. The X-ray studies also indicated the presence of a K 2 CuCl 4 · 2H 2 O phase in the used catalyst.

The impregnation of previously wetted alumina pellets with aqueous solution of copper(II) chloride is studied experimentally and theoretically. Internal copper concentration profiles resulting from impregnation with different copper chloride solution concentrations and various impregnation times are determined by electron probe microanalysis and indicate a shell-progressive immobilization. Temperature-programmed reduction measurements conducted on impregnated alumina catalysts indicate two types of immobilized copper species with different reducibilities. An impregnation model is applied to describe the experimentally determined internal copper concentration profiles and the copper uptakes in terms of the measurable properties of the system. The model is based on slow diffusion and rapid irreversible immobilization of the copper ions on the support. It extends the well-known shell-progressive immobilization model to account for precipitation, which occurs during the drying process, of metal ions from solution trapped in the catalyst pores. Thus the model extends the scope of the shell-progressive model, which is applicable only for local metal loadings corresponding to the site density of immobilization sites, to the preparation of catalysts with higher local metal loadings. A tortuosity factor of 1.8 for the alumina support is calculated from the effective diffusivity of the copper chloride as estimated from the measured data and its molecular diffusivity as reported in the literature. The experimentally determined internal concentration profiles and copper uptakes agree with the theory to within experimental error.

Methanol-reforming reaction CH3OH + H2O = 3H2 + CO2 was carried out over copper-containing catalysts which were prepared from hydroxides of copper or from the hydroxide kneaded with various metal oxides. The specific activity (activity per weight of copper used) either of supported or support-free catalyst was markedly increased when the hydroxide was prepared from alkali solution with addition of copper salt solution at higher pH or when the weight percentage of copper on the support was decreased. However, other kinetic parameters such as activation energy and selectivity of the reaction were unaffected by the preparation of the catalyst unless copper chloride was employed as a starting material of the hydroxide preparation at lower pH. DTA, ir, XPS, AES and other chemical analyses of the catalysts revealed that hydroxide ion in the hydroxide precipitate prepared at lower pH exchanged in part with the anionic group of its starting material during the course of the preparation. The anion or its fragment was found to be strongly held on the surface and inhibited the reaction to a great extent. On the other hand, the anion held was markedly decreased when the catalyst was prepared at higher pH. This catalyst was found to be highly active for the title reaction. The surface area of metallic copper was considerably increased when copper was kneaded with the support. This gave rise to the increase in the specific activity of the catalyst. The effect of the support upon the reaction was examined for the catalyst kneaded with silica, manganese dioxide, ferric oxide, titanium oxide, calcium oxide, and nickel oxide. However, the supports other than nickel oxide exerted no chemical effect upon the reaction. Nickel oxide was suggested to be reduced during the course of the reaction and metallic nickel thus formed catalyzed the methanol decomposition reaction CH3OH = CO + 2H2.

Variations of catalytic properties of CuCl2 supported on γ-alumina with active phase content and carrier thermal treatment were investigated by EPR and X-ray diffraction techniques. Two series of catalysts were prepared using γ-alumina, treated at 400 and 800 °C, as supports. In both series the copper content ranged from 0.3 to 8 wt % of the total catalyst weight. On the basis of EPR and X-ray diffraction studies, two different types of bonds between the oxygen of the γ-alumina surface and the copper ions are considered predominant in each series of catalysts. Catalyst activity and selectivity in the oxychlorination of benzene are discussed in terms of the chemical nature of these bonds and of the location of the copper chloride on the carrier surface.