Catalysts coprecipitation method

On the basis of the experimental results, Sn02-Zr02 catalysts were prepared by the coprecipitation method. That is, Sn02 and Z1O2 were mixed chemically rather than physically. The effects of the Sn/Zr molar ratio and reaction temperature on the SO2 conversion and sulfur yield for Sn02-Zr02 catalysts were... 

The copper-ceria catalysts in WGS were found to be nonpyrophoric and stable, showing little or no deactivation during the experiments. The Civ,2Ce(J802 y catalyst prepared by coprecipitation method showed good catalytic activity for the WGS reaction. The Cu0, Ce0 902 v catalysts prepared by the sol-gel method were found to be less active, which could be due to the lower number of active... 

By carrying out selective CO oxidation with some addition of C02 and H20 to the feed gas over a similar nanostructured CTy.Cej x02 catalyst prepared by a coprecipitation method [56], 15 vol% of C02 in the feed gas decreases the activity of the catalyst. Under these conditions the same values of activity and selectivity were obtained at temperatures 15 to 35°C higher. The addition of 10 vol% of H20 shifted the activity and selectivity curves to temperatures 20 to 40°C higher with respect to the curves where only CO, 02, H2, and He were used in the feed. 

The catalysts can be obtained by a coprecipitation method consisting of two steps (Figure 6.2). In the first step, a stable suspension of protected metal nanoparticles is obtained according to the method reported by Schulz and co-workers [75-77]. The metal particles are prepared in the presence of a highly water-soluble ionic surfactant which is able, due to its nature, to modulate the particle size and to prevent their aggregation. Modifying parameters such as pH, temperature and surfactant concentration, it is possible to tune the metal particle size [71]. Moreover, the role of the... 

M(lI)AlSn-LDHs with M(II) being Mg, Ni or Co were synthesized by a coprecipitation method. The influence of Sn on the thermal transformations and redox properties were investigated in detail using XRD, TG/DTA, SEM, TPR, 1 l9Sn-MAS NMR and UV-visible diffuse-reflectance (DR) spectroscopy methods. Some of these samples calcined at 450 °C were tested as catalysts in the partial oxidation of methanol (POM) reaction. In this paper we discuss briefly the effect of Sn-incorporation on the structural features and reducibility of CoAI-LDH. The catalytic performance of Co-spinel microcrystallites derived from CoAl-, and CoAlSn-LDHs was also evaluated. 

Metallic gold has also been dissolved from pure ceria,51 from gadolinium-doped ceria,51 and from catalysts made by a urea gelation/coprecipitation method ,52 without significant effect on their activities for water-gas shift. The only problem that has been identified is the formation of a cerium hydroxycarbonate, which occurs during shut-down when water is present. The very extensive work performed on this system48-52 ensures that its conclusions are given full consideration. 

Shen GC, Fujita SI, Takezawa N. Preparation of precursors for the Cu/ZnO methanol synthesis catalysts by coprecipitation methods - effects of the preparation conditions upon the structures of the precursors. J Catal. 1992 138(2) 754—8. 

The catalysts studied were prepared and purified by methods previously described1. Briefly, the silica-alumina support was prepared by a coprecipitation method on to the support and possessed a Si/Al ratio of 25. Ni2+ ions were introduced from an aqueous solution of nickel chloride by ion exchange at reflux. The final catalysts contained about 1.5 mass% Ni, with some residual sodium and chlorine, corresponding to a CI Ni mol ratio of <0.1, and a Ni Al mol ratio close to 1.0 (calculated with the assumption that all residual sodium is associated with some of the Al sites in the material (Na/Al mol ratio typically ca. 0.5)). 

A multicomponent catalyst (Cu/Zn0/Zr02/Ah03/Ga203) prepared by a conventional coprecipitation method [1] was used for the present study. The catalyst was pelletized to a cylindrical shape, the size of 3 mmD x 3 mmH. The multicomponent catalyst was developed on the basis of the role of metal oxides contained in a Cu/ZnO-based catalyst [2]. 

The iron oxide-based catalysts were prepared by Figure 1. Pathways of dehy-a coprecipitation method. In a typical experiment, drogenation of ethylben-1.4 g of catalyst (0.18-0.30mm) was set in a quartz tube reactor. Ethylbenzene was fed through a vaporizer, and was mixed with CO2. The flow rate was 130 ml/min. The dehydrogenation was conducted at 550 °C under atmospheric pressure. The product was analyzed by GC. ... 

Binary copper-based catalysts were prepared by coprecipitation method and some components were added as promoters into the binary catalysts. The methanol synthesis reaction was carried out in a continuous flow microreactor operated at 22 atm and at various temperatures. Reaction pathway of the methanol synthesis was investigated through FT-IR spectroscopy. For the catalyst with a copper content over 15wt%, the diffuse reflectance method (DRIFT) was applied, but for fee catalyst wife a copper content of 7wt%, the transmission teclmique was used. For more information about intermediates, TPD of adsorbed methanol was carried out and the products were analyzed using mass spectrometer. 

It is possible to obtain well-dispersed Ni-Co catalyst supported in a ZnAl204 non-stoichiometric inverse-spinel structure, by using an appropriate coprecipitation method. The close proximity of the reduction temperatures of Ni and Co produces a high degree of interdispersion and a synergetic increase in the activity of the active metals. Thus, catalytic... 

At these temperatures, not alkoxide catalyst, but conventional Cu/Zn based catalyst could be applied for the process to attain such high CO conversion, because some additives to Cu/Zn based catalyst such as Al, Ga, Zr, and Cr optimized the surface Cu /Cu ratio to give high methanol synthesis activity (5). Furthennore, Cu/Zn based catalysts prepared by an oxalate-ethanol coprecipitation method shows higher activity than those prepared by alkali coprecipitation method (6, 7), and thus, novel synergetic additives are expected using the novel preparation method. Therefore, we focused on the development... 

Cu/Zn/X oxide catalysts were prepared by an oxalate-ethanol coprecipitation method. Ethanol solutions of nitrate of Cu, Zn and one additive were mixed (Cu/Zn/X molar ratio was 65/35/5), and then an ethanol solution of oxalic acid was mixed to precipitate the mixed oxalic salts. Only vanadium acetyl acetone was solved in a mixed solvent (acetone methanol =1 1), and it was used as V source. Ethanol was removed by vaporization followed by calcination in air at 623 K for 4 hours. 

To determine whether titanium substitution would occur in the presence of excess antimony, catalyst 9 (Table I) was prepared as described in a Distillers patent (JL ), while catalyst 10 was prepared by our standard coprecipitation method. Small, amounts of Ti02 could be detected in both catalysts. Catalyst 9, which was calcined at a lower temperature than catalyst 10, contained USbO in addition to Ti02 The shift in d-spacing for the 004 reflection noted with the titanium-substituted phases was not seen for catalysts 9 and 10. Thus, the presence of excess antimony appeared to inhibit titanium substitution. These compositions were well above (on the excess antimony side) the binary join expected to facilitate titanium substitution for antimony. 

Mesoporous catalysts based on W03/Zr02 system have higher productivity due to the higher surface area and pore volume compared to similar materials obtained by the coprecipitation method. 

On the other hand, cerium has been shown to be an effective oxygen reservoir, enhancing the activity of many oxidation catalysts. Due to this property, cerium oxide is also considered to potentially enhance the thioresistance of the catatysts. This aspect is of great practical importance, since the use of palladium catalysts is hindered by the poisonous effect of sulphur compoimds, often present in off gases. Most works dealing with ceria-zirconia catalysts have been carried out with catalysts prepared by coprecipitation methods, whereas in this work an ahemative procedure, based on the incipient wetness technique is used to incorporate ceria to the zirconia support. The aim is to maintain the advantages of zirconia supports, especially the thermal stability. 

Bulk elemental analysis of some catalysts was performed by atomic absorption. The results presented in table 1 show that coprecipitation method yields, within the experimental errors, catalysts with the Mo/Fe atomic ratio of preparation. Catalysts prepared by sol-gel method showed lower Mo/Fe atomic ratios than the expected value. Furthermore calcination of these catalysts under air flow enhances the loss of Mo. 

Vanadium and antimony oxides are essential parts of some industrial catalysts for the selective oxidation of substituted aromatics to the corresponding anhydrides [1] and the selective oxidation of paraffins to the corresponding unsatuiated acids and nitriles [2], These catalysts are generally prepared by impregnation or coprecipitation methods. 

Each alloy catalyst was prepared by a coprecipitation method in which ammonium bicarbonate was added to an aqueous solution of nickel and copper nitrates. The resulting precipitate was dried and heated in air at 370°C to form a mixture of nickel and copper oxides. The mixed oxides were then reduced in hydrogen in several stages over a range of temperatures to produce the nickel-copper alloy. The reduction was completed at 400°C. 

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