Mixed-oxide catalyst

Kelkar and McCarthy (1995) proposed another method to use the feedforward experiments to develop a kinetic model in a CSTR. An initial experimental design is augmented in a stepwise manner with additional experiments until a satisfactory model is developed. For augmenting data, experiments are selected in a way to increase the determinant of the correlation matrix. The method is demonstrated on kinetic model development for the aldol condensation of acetone over a mixed oxide catalyst. 

The present work demonstrates that the mixed oxide catalyst with inhomogeneous nanocrystalline MosOu-type oxide with minor amount of M0O3- and Mo02-type material. Thermal treatment of the catalyst shows a better performance in the formation of the crystals and the catalytic activity. The structural analysis suggests that the catalytic performance of the MoVW- mixed oxide catalyst in the partial oxidation of methanol is related to the formation of the M05O14 t3 e mixed oxide. 

Several other important commercial processes need to be mentioned. They are (not necessarily in the order of importance) the low pressure methanol process, using a copper-containing catalyst which was introduced in 1972 the production of acetic add from methanol over RhI catalysts, which has cornered the market the methanol-to-gasoline processes (MTG) over ZSM-5 zeolite, which opened a new route to gasoline from syngas and ammoxidation of propene over mixed-oxide catalysts. In 1962, catalytic steam reforming for the production of synthesis gas and/or hydrogen over nickel potassium alumina catalysts was commercialized. 

Pyruvic acid is the simplest homologue of the a-keto acid, whose established procedures for synthesis are the dehydrative decarboxylation of tartaric acid and the hydrolysis of acetyl cyanide. On the other hand, vapor-phase contact oxidation of alkyl lactates to corresponding alkyl pyruvates using V2C - and MoOa-baseds mixed oxide catalysts has also been known [1-4]. Recently we found that pyruvic acid is obtained directly from a vapor-phase oxidative-dehydrogenation of lactic acid over iron phosphate catalysts with a P/Fe atomic ratio of 1.2 at a temperature around 230°C [5]. 

Over the V2O5- and Mo03-based mixed oxide catalysts, the main part of lactic acid is converted to form acetaldehyde and CO2. 

An iron phosphate catalyst with a P/Fe atomic ratio of 1.2 used in this study was prepared according to the procedures described in the previous studies [6-8]. On the other hand, a V-P oxide catalyst with a P/V atomic ratio of 1.06 and pumice supported 12-molybdophosphoric acid (H3PM012O40) and its cesium salt (CS2HPM012O40) catalysts were the same as used in a previous study [9]. Pumice supported W03-based mixed oxide catalysts were the same as used in a previous study [10]. 

In this paper we attempt a preliminary investigation on the feasibility of catalytic combustion of CO/ H2 mixtures over mixed oxide catalysts and a comparison in this respect of perovskite and hexaaluminate type catalysts The catalysts have been characterized and tested in the combustion of CO, H2 and CH4 (as reference fuel). The catalytic tests have been carried out on powder materials and the results have been scaled up by means of a mathematical model of the catalyst section of the Hybrid Combustor. 

Thammachart M, Meeyoo V, Risksomboon T, Osuwan S (2001) Catalytic activity of Ce02-Zr02 mixed oxide catalysts prepared via sol-gel technique CO oxidation. Catal Today 68 (1) 53—61... 

The increasing volume of chemical production, insufficient capacity and high price of olefins stimulate the rising trend in the innovation of current processes. High attention has been devoted to the direct ammoxidation of propane to acrylonitrile. A number of mixed oxide catalysts were investigated in propane ammoxidation [1]. However, up to now no catalytic system achieved reaction parameters suitable for commercial application. Nowadays the attention in the field of activation and conversion of paraffins is turned to catalytic systems where atomically dispersed metal ions are responsible for the activity of the catalysts. Ones of appropriate candidates are Fe-zeolites. Very recently, an activity of Fe-silicalite in the ammoxidation of propane was reported [2, 3]. This catalytic system exhibited relatively low yield (maximally 10% for propane to acrylonitrile). Despite the low performance, Fe-silicalites are one of the few zeolitic systems, which reveal some catalytic activity in propane ammoxidation, and therefore, we believe that it has a potential to be improved. Up to this day, investigation of Fe-silicalite and Fe-MFI catalysts in the propane ammoxidation were only reported in the literature. In this study, we compare the catalytic activity of Fe-silicalite and Fe-MTW zeolites in direct ammoxidation of propane to acrylonitrile. 

A possible method for producing glycerol derivatives can be the reactive distillation in the presence of various oxide and mixed oxide catalysts, such as copper-chromite [3], In this reaction acetol, 1,2- and 1,3-propanediols may be obtained. 

With regard to the specific activity, the mixed oxide catalyst, E, showed the best performance of all reactants, 1 and 6 being exceptions. For the latter, A and B performed better. 

Although the catalyst did not recover in the reformate stream, the authors did indicate that the carbonate species could be removed by air treatment at temperatures > 400 °C. Ruettinger and coworkers452 reported on the mechanism of aging of Pt/ceria-zirconia mixed oxide catalysts. In that case, the authors followed the activity of a 2% Pt/Ce02-Zr02 catalyst at 228 °C in a feed containing 5.92% CO, 7.4% C02, 31.82% H2, 28.86% N2, and 26% H20, and observed the deactivation data tabulated in Table 86. 

Figure 1.18 Survey and expanded V 2p and Mo 3d XPS spectra form a Mo-V-Sb-Nb mixed oxide catalyst after calcination in nitrogen (a) and air (b) atmospheres [145]. The data indicate a lesser degree of oxidation in nitrogen, a result that was correlated with the promotion of reactions leading to the production of propene and acrylic acid rather than acetic acid, the main product obtained with the fully oxidized sample. (Reproduced with permission from Elsevier.)...

Many reports have focused on the use of LDHs as precursors to mixed oxide catalysts formed by thermal decomposition. Such metal oxides are... 

Heterogeneous catalysis is clearly a complex phenomenon to understand at the molecular level. Any catalytic transformation occurs through a sequence of elementary steps, any one of which may be rate controlling under different conditions of gas phase composition, pressure, or temperature. Furthermore, these elementary processes occur catalytically on surfaces that are usually poorly understood, particularly for mixed oxide catalysts. Even on metallic catalysts the reaction environment may produce surface compounds such as carbides, oxides, or sulfides which greatly modify... 

Babu NS, Pasha N, Rao KTV, Prasad PSS, Lingalah N (2008) A heterogeneous strong basic Mg/La mixed oxide catalyst for efficient synthesis of polyfunctionalized pyrans. Tetrahedron Lett 49 2730-2733... 

Saturating the electrolyte with iron(lll) hydroxide (e.g., by addition of aqueous solutions of ferric nitrate) and simultaneously adding cobaltous salts leads to in situ formation of a mixed Fe(llI)/Co(ll)/Co(IIl) deposit, which exhibits catalytic activity comparable to that of Fe304 shown by the current voltage curve in Fig. 11. Such mixed oxidic catalyst coatings are composed of very small oxide crystals, which evidently are dissolved upon current interruption due to dissociative oxide dissolution. The transfer of dissolved metal ions to the cathode followed by cathodic deposition of the metal, however, can be completely prohibited, if the potential of the cathode due to optimal electrocatalysis of cathodic hydrogen evolution proceeds with an over-... 

It is doubtful whether a single-step process is at present competitive with the two-step process currently used in industry. In the latter, the oxidation of acrolein to acrylic acid is carried out with high selectivity over mixed-oxide catalysts based, for example, on M0O3—V2Os or Mo03— Te02 [160],... 

The ammoxidation of propene to acrylonitrile is of great industrial importance and accordingly the literature is abundant. The reaction is very similar to the oxidation of propene to acrylonitrile and carried out at the same conditions and over the same kind of catalysts. The famous bismuth phosphomolybdate catalyst developed by Sohio was the first of a series of highly effective mixed-oxide catalysts. The optimum yields are generally obtained at temperatures of 400—500°C. Initial selectivities over 95% and yields up to 80% are feasible. The superior selectivity of the ammoxida-... 

Strong indications are present for some mixed oxide catalysts that the interaction with the molecule to be oxidized and the oxygen that reoxidizes the catalyst take place on different sites and involve different cations. These two sites may together form one ensemble that performs the complete reaction. However, they may also be actually separated and quite remote, provided that the transport of anions and the conduction of charge between such sites is sufficiently large. 

Hydroxylamine-O-sulfonic acid converts thiophene-2-carbaldehyde into the nitrile in high yield under mild conditions. 3-Azidothiophene-2-carbonitrile has been prepared thus and used for synthesizing many types of fused thiophenes (80JHC1765). Vapour-phase ammoxidation of thiophene-2-carbaldehyde to the nitrile has also been described (78CPB2838) the Mo-Bi-Sb (molar ratio 3 5 2) mixed oxide catalyst was found most suitable. 

Bismuth is an important element in many of the new high-temperature, oxide superconductors and in a variety of heterogeneous mixed oxide catalysts. Some of the methods employed in the preparation of these materials, namely sol-gel and chemical vapor deposition processes, require bismuth alkoxides as precursors and a number of papers on these compounds have recently been published.1 One synthetic route to bismuth alkoxides, which avoids the more commonly used trihalide starting materials and the often troublesome separation of alkali metal halides, involves the reaction between a bismuth amide and an alcohol according to the following equation ... 

Vapor-phase oxidation of toluene to benzaldehyde was studied with various Mo-, U—, and Sb-based mixed-oxide catalysts. The selectivity to benzaldehyde fell with increasing the toluene conversion. The best performances were obtained with Mo-P and U-Mo oxide catalysts the one-pass yield of benzaldehyde reached 40 mol% with a selectivity of about 60 mol%. The catalytic activity of the U-Mo oxides was more stable than that of the Mo-P oxides. The effects of the reaction variables on both the rate and selectivity were also studied. 

Our first study of reaction (342) kinetics (124) was done in a flow system under atmospheric pressure at 400, 450, and 500°C on a Fe304 catalyst without any additions and also on a mixed oxide catalyst of the nitrogen type, the active component of which is Fe304. 

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