Y-alumina-supported catalyst

Table V shows the results obtained for the carbonylation of dimethyl ether and methyl acetate with molybdenum catalysts supported on various carrier materials. In the case of dimethyl ether carbonylation, molybdenum-activated carbon catalyst gave methyl acetate with an yield of 5.2% which was about one-third of the activity of nickel-activated carbon catalyst. Silica gel- or y-alumina-supported catalyst gave little carbonylated product. Similar results were obtained in the carbonylation of methyl acetate. The carbonylation activity occured only when molybdenum was supported on activated carbon, and it was about half the activity of nickel-activated carbon catalyst.

Table 1 lists the surface area of prepared catalysts and the chemisorption results of CO2 and H2 on the catalysts. In case of supported Fe catalysts, the sxirface area is support-dependent. In contrast, Fe-K/Si02 shows much smaller surface area compared with silica or Fe/Si02. This indicates that with increased mass of active phase, iron and potassium blocks the micro-pore of silica support. This seems to be due to the smaller pore diameter of silica (see experimental). In addition, if Fe-K exists mainly as poorly dispersed masses, it would block easily the micro-pores of the support. From the chemisorption results, it is apparent that only y-alumina-supported catalysts, Fe/Al203 and Fe-K/Al203 give greatly... 

The effects of oxidation - reduction cycles on the activity and selectivity of supported Rh catalysts were investigated using the hydrogenolysis of methylcyclopentane (MCP) as a test reaction. Prom the analysis of catalytic properties and reduction profiles it Is concluded that, on silica-supported catalysts, following the initial oxidation at 400 C successive reduction treatments at increasing temperatures cause a progressive reconstruction of the Rh particles. On y-alumina-supported catalysts the situation is more complex. The interaction of Rh with the support during the Initial oxidation makes a fraction of the Rh Inaccessible to the gas phase. Only after subsequent oxidation - reduction cycles do they behave like the silica-supported catalysts... 

Olefin Metathesis in Nontraditional Media T 37 Figure 5.24 y-Alumina-supported catalyst 116. 

Noble Metal Catalysts. Rh-based catalysts have been investigated on different supports, resulting in different H2 and CO yields. Gasoline and naphtha POX over a supported Rh catalyst were reported by Fujitani et al. For y-alumina supported Rh catalyst, maximum yields of 96% of both H2 and CO were reported with 0.2 wt% Rh loading at 700°C, an air equivalence ratio of 0.41, and a liquid hourly space velocity (LHSV) of 2 h A 0.05 wt% Rh supported on zirconia yielded 98% H2 and 85% CO at 725°C, an... 

A direct comparison of Al203-supported Pt, Pd, and Ru suggests that Ru is the most active metal for diesel reforming, at least on this support. Berry et al studied diesel reforming at a temperature range of 750 to 850°C and GHSVs of 25,000 to 200,000 h Activity increased in the order Pd < Pt < Ru. Complete conversion of diesel was obtained at 850°C and space velocity of 50,000 h from the ATR of diesel over a y-alumina supported Ru catalyst. 

Beltramini and Trimm (67) utilized Pt-, Sn- and Pt-Sn- supported on y-alumina for the conversion of n-heptane at 500°C and 5 bar. They observed that during six hours less coke per mole of heptane converted was deposited on the Pt-Sn-alumina catalyst than on Pt-alumina however, the total amount of coke formed during six hours was much greater on Pt-Sn-alumina than on Pt-alumina. The addition of tin increased the selectivity of dehydrocyclization. Since hydrocracking and isomerization activity of a Sn-alumina catalyst remained high in spite of coke formation, the authors concluded that there was little support for the suggestion that tin poisons most of the acid sites on the catalyst. These authors (68) also measured activity, selectivity and coking over a number of alumina supported catalysts Pt, Pt-Re, Pt-Ir, Pt-Sn and Pt-... 

Although the relative deactivation of titania-supported catalysts is smaller than for y-alumina-supported ones, the activity still decreases considerably over the first 150 h of operation (see Fig. 3), resulting in a loss of approximately 40% of the initial activity (neglecting Stage 1). After 150 h the activity and butanone selectivity remains stable for a period of more than 650 h. After 800 h the catalyst was taken from the reactor and investigated to reveal the differences with the fresh catalyst. 

Aluminas are used in various catalytic applications, a-, y-, and -aluminas are all used as support materials, the first one in applications where low surface areas are desired, as in partial oxidation reactions. The latter two, and especially y-alumina, in applications where high surface areas and high thermal and mechanical stability are required. One of the most prominent applications of y-alumina as support is the catalytic converter for pollution control, where an alumina washcoat covers a monolithic support. The washcoat is impregnated with the catalytically active noble metals. Another major application area of high-surface aluminas as support is in the petrochemical industry in hydrotreating plants. Alumina-supported catalysts with Co, Ni, and/or Mo are used for this purpose. Also, all noble metals are available as supported catalysts based on aluminas. Such catalysts are used for hydrogenation reactions or sometimes oxidation reactions. If high... 

Typical substances that find wide use as high-area supports include silica gel and y-alumina, which can be obtained with surface areas in the range 100-800 m2/g. Materials used as low-area supports ( 1 m2/g) include a-alumina and mullite (alumina-silica). It is not easy to make general statements about the preparation of industrial catalysts because of the great variety of forms they take, but in many cases one can distinguish between the chemical operations in which the various components are assembled in the desired form, and the fabrication step in which they are made into the desired shape. The first step will be illustrated by a description of the method of preparing of silica gel and y-alumina support material [1]. 

In the present case we report ESCA examinations of composite systems realized when varying amounts of platinum metals (i.e., Pt or Pd) and other species are doped by some conventional means onto a standard y-alumina support in a manner designed to simulate systems often employed in Pt metals catalysis (1.2). A unique feature of the present study is that the doping compositions are typical of those of real catalysts, e.g., 0.2 < Pt wt% < 0.75. Generally the Pt metals can be assumed to be the principal active metal species added, although the function of that dopent has been suspected to depend significantly on the other species present (3). 

The catalyst of the current invention has also been prepared on a y-alumina support (3). 

The preparation procedure employed is known to lead to the formation of VOPO4, rather than (VO)2P207. The presence of Sb, however, may lead to a modification of the structural features. Indeed, the authors claim the presence of vanadyl pyrophosphate as the major phase present in catalysts, with a minor amount of vanadium phosphate. The atomic ratio between the components of the y-alumina-supported active phase was V/Sb/P 1/1.9/1.18. The reaction conditions were 425 °C (at which the best yields were reported), and a feed ratio of reactant/ air/ammonia of 0.6-1.0/4.2/1.5. The following results were claimed under these conditions ... 

Galwey AK, Bettany DG, Mortimer M (2006) Kinetic compensation effects observed during oxidation of carbon monoxide on y-alumina supported palladium, platinum, and rhodium metal catalysts toward a mechanistic explanation. Int J Chem Kin 38 689... 

Mixtures of transition metal (Mo or W) sulphides dispersed on y-alumina supports are used in hydrotreatment processes to remove sulphur, nitrogen, oxygen and metals from oil fractions. The addition of phosphorus to these catalysts enhances the solubility and stability of molybdate and improves the thermal stability of the alumina support. Solid state P double-resonance NMR experiments ( P- AI REDOR and TRAPDOR) have been used to investigate the interaction between the impregnating phosphorus and the support surface (van Eck etal. 1995). The results showed that most of the phosphorus is in close contact with the aluminium, and that the layer of AIPO4 formed on the surface is not completely amorphous, but is slightly more ordered. 

Y. F. Chu, Behavior of Pt CrystalUtes on Carbon and Alumina Supported Catalyst Ph.D. Dissertation, University of New York at Buffalo, 1978. 

About 30 mg of a Pt-Sn/AlaOs catalyst were used in each run. The particle size were chosen small enough to avoid internal mass transfer limitations. The catalyst was prepared by sequential impregnation of a commercial y-alumina support with aqueous solutions of SnCl2 and HaPtClfi [9]. Characterization data are summarized in Table 1. 

In the early 80 s, Bachelier et al. [9] demonstrated that catalytic efficiency depends on the Mo loading of the catalyst. We have studied the effect of molybdenum loading on HDS activity and found an optimum metal loading of about 6 wt% for a selected y-alumina support (Figure 1). Such a behaviour has been rationalized by a change in the molybdenum sulfide particle size [9]. With the addition of cobalt, the activity per molybdenum atom increases at low cobalt content and then reaches a plateau as shown in Figure 2. Such a result confirms earlier works done by Bachelier et al. on NiMo catalysts [10, 12]. Today, the preferred interpretation is that cobalt atoms decorate the molybdenum sulfide particles. This hypothesis was predicted by a geometrical model [8] and confirmed experimentally [12],... 

In this work, we report a comparative study of 3%CoO and 14%Mo03 catalysts made with either a y-alumina support or a proprietary Procatalyse support. We have compared their toluene hydrogenating activity and characterized the sulfided catalysts by Transmission Electronic Microscopy (TEM). 

Finally, Vroon et al. [82,97] reported the synthesis of continuous porous films of ZSM5 on top of y-alumina supported membranes (pore diameter 4 nm) by slip-casting with a zeolite crystal suspension. The porous zeolite layers (thickness 1-2.5 pm) consist of densely packed zeolite crystals with a diameter of 70-80 nm and with micropores in the zeolite and mesopores (diameter 8-24 nm) between the zeolite particles. This zeolite layer can be used as a support for further processing, e.g., pore filling of the mesopores or deposition of catalysts. First experiments by Vroon et al. to fill the mesopores by in situ crystallisation of MFI in the pores did not result in gas-tight membranes... 

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