Alumina-based catalysts

Sodium alumiaate is widely used in the preparation of alumina-based catalysts. Aluminosilicate [1327-36-2] can be prepared by impregnating siHca gel with alumiaa obtained from sodium alumiaate and aluminum sulfate (41,42). Reaction of sodium alumiaate with siHca or siHcates has produced porous crystalline alumiaosiHcates which are useful as adsorbents and catalyst support materials, ie, molecular sieves (qv) (43,44). 

For the methanation reaction in the process of converting coal to a high Btu gas, various catalyst compositions were evaluated in order to determine the optimum type catalyst. From this study, a series of catalysts were developed for studying the effect of nickel content on catalyst activity. This series included both silica- and alumina-based catalysts, and the nickel content was varied (Table I). 

Investigation of ozonolysis of phenol using y-alumina based catalysts... 

P., Detailed characterization of various porous alumina based catalyst coatings within microchannels and their testingfor methanol steam reforming, Chem. Eng. Res. Des., special issue on Chemical Reaction Engineering (2003) submitted for publication. 

GSl 6][R14] SputteredandimpregnatedPtcatalystswerecompared(Figure3.62) regardingtheirreactionrates([Pg.352]

Arco A process for making isobutene by dehydrating /-butanol. The reaction takes place in the gas phase at 260 to 273°C, 14 bar, in the presence of an alumina-based catalyst. 

An alumina-based catalyst will be bound, for the purpose of mechanical strength, with carbon. The alumina-carbon mixture is essentially a composite support for adsorbing the Pt precursor. If it is desired that all metal go onto the alumina phase, which type of carbon (oxidized or unoxidized) and what type of Pt complex should be used and why A sketch of the surface potential vs. pH for alumina and the carbon binder will help. 

Table 12. Physicochemical properties of alumina-based catalysts [110]...

Fischer-Tropsch (FT) process is used for the production of hydrocarbon fuels. The process uses synthesis gases CO and H2O. It is shown that cobalt/alumina-based catalysts are highly active for the synthesis. The process is also used to convert coal to substitute or synthetic natural gas (SNG). The use of Fe-based catalysts is also believed to be attractive due to their high FT activity. HRTEM has played a major role in the study of phase transformations in Fe Fischer-Tropsch during temperature programmed reduction (TPR) using both CO and H2 (Jin et al 2000, Shroff et al 1995). TiClj/MgC -based (Ziegler-Natta) catalysts are used for polymerization of alkenes (Kim et al 2000) and EM is used to study the polymerization (Oleshko et al 2002). 

The conversion of furans into the corresponding thiophenes or pyrroles entails passage of the furan with hydrogen sulfide or ammonia over an alumina-based catalyst at elevated temperatures (B-73MI50300). Conversions of furans into thiophenes are also achieved with hydrogen sulfide and hydrogen chloride at 80-100°C (80DOK(255)H44>. Selenophenes can be obtained similarly. 

The amount of wash coat which was deposited in the testing reactors was in the same range, between 14 and 17 mg, for the rhodium, platinum and palladium samples tested. The platinum sample was calcined after impregnation at a lower temperature of 450 °C, all other samples at 800 °C. The reason for this will be explained below. The content of the active noble metal was around 5 wt.%. All noble metal-containing samples were laboratory-made catalysts. A commercial a-alumina-based catalyst containing 14 wt.% Ni was added for comparison, as nickel catalysts are applied in industrial steam reforming [52],... 

Up to 48 ternary catalyst mixtures were prepared simultaneously in less than 1 h. Hence the sputtering procedure is much faster than the wet chemical route and in fact one of the fastest syntheses available. This advantage is gained at the expense of low layer porosity. Thus, sputtered catalysts are new artificial catalysts and not directly comparable to catalysts prepared by wet-chemical procedures. These catalysts offer the advantage of quick preparation and characterization compared with alumina-based catalysts. They can also be used for obtaining so-called intrinsic kinetics because there is no influence of diffusion. 

The continuous vapor phase dehydrogenation of piperazines is effectively carried out over a prereduced 80% CuO-20% Cr2Os catalyst at 350°. In this way 2-ethyl-, 2,6-dimethyl-, and 2,3,5,6-tetramethylpiperazines have been converted into the corresponding pyrazines in 79-89% yield.126-128 Pyrazine itself is obtained from piperazine in 18% yield by the use of 5% Pt on alkali-washed firebrick catalyst.129 The catalytic deamination of diethylenetriamine over alumina-based catalysts at temperatures of 300°-400° gives good... 

Alkylphenols may be produced via the alkylation of phenol with methanol. This reaction produces predominantly anisole and o-cresol with methylanisole and xylenol also being obtained. Strong Bronsted acids are not required to effect these transformations, as both amorphous aluminas and silica/aluminas are active catalysts. Often o-cresol can be produced in 100% isomeric selectivity, particularly when the reaction is run over amorphous alumina based catalysts. When zeolites are used isomer selectivities are changed. 

Catalyst Acidity bv Ammonia Chemisorption. Plant performances below expectations were reported by two units, in which the original alumina based catalysts were replaced. Surface area specifications were 150-200 m2/g for both catalysts. Acidity was measured by ammonia chemisorption using a recording vacuum thermoanalyzer with a TGA sample holder, and was correlated with BET surface area, as shown in Table V. 

The derivation of a mechanism for a chemical reaction is by its very nature an uncertain process, being dependent critically on the nature and extent of the experimental evidence. Mechanisms that have at their heart a surface process or processes are even more uncertain and when the constraints imposed by the manipulation of HF are also taken into account, it is not surprising that there have been relatively few mechanistic studies made of heterogeneous catalytic fluorination. However a catalytic process cannot be said to be understood fully without a mechanism based on the experimental evidence available and such studies are helpful in the design of the next generation of catalysts. In most cases the work described below involves chromia or y-alumina based catalysts that have been pretreated according to the methods described above. Studies involving C2 and Q compounds are described in turn. 

The earlie industrial developments of vapor phase alkylation processes involved the use of alumina base catalyst systems. They include the Koppers technique industrialized in the Second World War, which operates around 310°C and between 6 and 6. 10 Pa absolute, but does not allow the transalkylation of polyethylbenzenes. 

The zeolites have been first used as catalyst in the 1960s for alkane cracking reactions in petroleum industry.They replaced favorably previously employed alumina based catalysts because of their better therm and mechanical stability. Moreover, they showed higher selectivity. The selectivity finds its source in the zeolite micropore structure with different... 

FeS also catalyzes the shift reaction, but its activity is only half that of Fe,04 [592]-[594], In principle the catalyst can tolerate up to 500 or 1000 ppm H2S, but with a considerable loss of mechanical strength, which is additionally affected by other contaminants in the gas, such as soot and traces of formic acid. For this reason the so-called dirty shift catalyst is used in this case, which was originally introduced by BASF [639]. This cobalt-molybdenum-alumina catalyst [603], [630], [640]-[644] is present under reaction conditions in sulfidized form and requires for its performance a sulfur content in the gas in excess of 1 g S/m3. Reaction temperatures are between 230 and 500 °C. COS is not hydrolyzed on dirty shift catalysts, but may be removed in the subsequent sour-gas removal stage using the Rectisol process. Separate hydrolysis on alumina based catalysts is possible at temperatures below 200 °C [603],... 

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