Nickel kieselguhr-supported

Fig. 2. (a) Magnetization-volume isotherms for the chemisorption of hydrogen and of benzene on kieselguhr-supported nickel at 150° C (16). (b) Average number of bonds formed by benzene adsorbed on nickel-silica as a function of temperature (17). From J. Amer. Chem. Soc. 79, 4637 (1957) 83, 1033 (1961). Copyright by the American Chemical Society. Reprinted by permission of copyright owner. 

Butanol, reaction over reduced nickel oxide catalysts, 35 357-359 effect of ammonia, 35 343 effect of hydrogen, 35 345 effect of pyridine, 35 344 effect of sodium, 35 342, 351 effect of temperature, 35 339 over nickel-Kieselguhr, 35 348 over supported nickel catalysts, 35 350 Butanone, hydrogenation of, 25 103 Butene, 33 22, 104-128, 131, 135 adsorption on zinc oxide, 22 42-45 by butyl alcohol dehydration, 41 348 chemisorption, 27 285 dehydrogenation, 27 191 isomerization, 27 124, 31 122-123, 32 305-308, 311-313, 41 187, 188 isomerization of, 22 45, 46 isomers... 

The effect of alkali metal on the catalytic gasification of rice straw over nickel catalysts supported on kieselguhr... 

Abstract Rice straw was catalytically gasified over nickel catalysts supported on kieselguhr. This has been done by varying the content of alkali carbonate, lithium metal (3-20wt%) and various sodium compounds. In the case which alkali metal carbonates were separately added with nickel catalyst, conversion to gas was increased in the following order of Li< Cs< Kalkali metals were used to as co-catalyst by impregnation method, gas formation was increased in the following order Cs< tC a< Li. These results showed same aspects with TPR patterns. 

The traditional treatment of nitrobenzene (1) with iron and acid, called Bechamp reduction, was employed almost exclusively in the production of aniline (2) and many aromatic amines until the 1960s1,2 (Scheme 1). The reduction is straightforward, and can also be achieved by catalytic hydrogenation, sodium sulfide reduction and zinc reduction with caustic soda. Nitrotoluenes and nitroxylenes are hydrogenated under pressure over a nickel catalyst supported on kieselguhr. The sulfide reduction is useful in selective reduction, such as of m-dinitrobenzene to m-nitroaniline. 

In an effort to obtain a less temperature-sensitive system, lower nickel content catalysts were prepared on an alumina support and tested for demethylation activity. The first, Preparation A, with a nominal nickel content of 50 wt % was activated at 700°F in a slow stream of hydrogen at atmospheric pressure for 16 hours. This catalyst was tested at conditions similar to those employed with the nickel-kieselguhr catalyst reported above. The results are given in Table II. 

Catalysts formed by intermetallic compound decomposition show impressive resistance to H2S. Results obtained are shown in Figure 2. It is to be noted that decomposed ThNis is more resistant to poisoning than decomposed ZrNis or the commercial supported nickel catalyst. It is not clear at this time what factors produce these diflFerences. Perhaps the metallic area was smaller for the kieselguhr-supported material it was not determined. The metallic areas of the two decomposed inter-metallics were established and were comparable. 

It will be seen that the toxicity increases with the molecular size of the poison. Further, in spite of the obviously far greater specific surface of the 0.05 g. of kieselguhr-supported nickel compared with the surface of the 0.05 g. of unsupported platinum (which is reflected in the different order of the values of a, i.e. 10 and 10 , respectively, in the platinum and... 

In industrial practice, although some copper catalysts have been used, it is customary to use dry or wet reduced nickel catalysts supported on a natural earth such as kieselguhr and suspended in an hydrogenated fat, usually hardened palm or soybean oil. The nickel content of the commercial catalyst is between 17 and 25% and a similar amount of earth is incorporated. 

Akers and Camp(1955) studied the reaction between steam and natural gas within the temperature range of 340-640°C at 1 atmosphere using 3mm diameter pellets of nickel produced by the reduction of nickel oxide supported on kieselguhr. There was little reaction at temperatures less than 600°C and they found first order dependence of the rate of disappearance of methane upon the partial pressure of methane at 640 C. They reported that there was no significant variation of catalyst activity with time. 

The first promising catalyst was introduced by 1931 and contained a high proportion of nickel oxide supported on a mixture of thoria and kieselguhr. The convention widely used at the time was to describe composition as 100 parts nickel, 18 parts thoria, 100 parts kieselguhr. Catalysts made with cobalt rather than nickel were more effective but could not be considered eommercially at that time because cobalt was not available in suffieiently large quantities. The same problem had, of course, faced Haber and Boseh in the replaeement of osmium by iron oxide for the ammonia synthesis eatalyst. 

The catalysts contain more than 50% nickel oxide, supported on kieselguhr with some added alumina, and are prereduced and stabilized. This allows for rapid reduction in existing reactors. The process operates at the relatively low temperature of 80°C with hydrogen pressures in the range 20-40 atm. A liquid space velocity of about 2.5 h" is required and hydrogen addition depends on the aromatics content of the feed being treated. 

Hydrogenation. Hydrogenation is one of the oldest and most widely used appHcations for supported catalysts, and much has been written in this field (55—57). Metals useflil in hydrogenation include cobalt, copper, nickel, palladium, platinum, rhenium, rhodium, mthenium, and silver, and there are numerous catalysts available for various specific appHcations. Most hydrogenation catalysts rely on extremely fine dispersions of the active metal on activated carbon, alumina, siHca-alumina, 2eoHtes, kieselguhr, or inert salts, such as barium sulfate. 

Supported palladium, zirconium-promoted cobalt on kieselguhr, or nickel on kieselguhr can be used under relatively mild conditions to effect reduction of the nitrile function without hydrogenating the ring. 

Nickel. As a methanation catalyst, nickel is presently preeminent. It is relatively cheap, it is very active, and it is the most selective to methane of all the metals. Its main drawback is that it is easily poisoned by sulfur, a fault common to all the known active methanation catalysts. The nickel content of commercial nickel catalysts is 25-77 wt %. Nickel is dispersed on a high-surface-area, refractory support such as alumina or kieselguhr. Some supports inhibit the formation of carbon by Reaction 4. Chromia-supported nickel has been studied by Czechoslovakian and Russian investigators. 

Nickel catalysts are universal and are widely used not only in the laboratory but also in the industry. The supported form - nickel on kieselguhr or infusorial earth - is prepared by precipitation of nickel carbonate from a solution of nickel nitrate by sodiiun carbonate in the presence of infusorial earth and by reduction of the precipitate with hydrogen at 450° after drying at 110-120°. Such catalysts work at temperature of 100-200° and pressures of hydrogen of 100-250 atm 43. ... 

The currently practiced commercial process using nickel catalysts, either supported on kieselguhr or silica, has some disadvantages ... 

Historical Development and Future Perspectives The Fischer-Tropsch process dates back to the early 1920s when Franz Fischer and Hans Tropsch demonstrated the conversion of synthesis gas into a mixture of higher hydrocarbons, with cobalt and iron as a catalyst [35, 36], Some 20 years earlier, Sabatier had already discovered the reaction from synthesis gas to methane catalyzed by nickel [37]. The FTS played an important role in the Second World War, as it supplied Germany and Japan with synthetic fuel. The plants used mainly cobalt catalysts supported on a silica support called kieselguhr and promoted by magnesia and thoria. 

For more effective and/or larger-scale hydrogenations, use of higher temperatures and pressures is advantageous as in an example shown in eq. 5.3.5 Supported nickel catalysts such as Ni-kieselguhr may also be useful at temperatures above 100°C (eq. 5.4).6... 

Catalytic tests in sc CO2 were run continuously in an oil heated flow reactor (200°C, 20 MPa) with supported precious metal fixed bed catalysts on activated carbon and polysiloxane (DELOXAN ). We also investigated immobilized metal complex fixed bed catalysts supported on DELOXAN . DELOXAN is used because of its unique chemical and physical properties (e. g. high pore volume and specific surface area in combination with a meso- and macro-pore-size distribution, which is especially attractive for catalytic reactions). The effects of reaction conditions (temperature, pressure, H2 flow, CO2 flow, LHSV) and catalyst design on reaction rates and selectivites were determined. Comparative studies were performed either continuously with precious metal fixed bed catalysts in a trickle bed reactor, or discontinuously in stirred tank reactors with powdered nickel on kieselguhr or precious metal on activated carbon catalysts. Reaction products were analyzed off-line with capillary gas chromatography. 

With a DELOXAN supported palladium complex catalyst, DELOXAN HK I, the linoleate selectivity is further increased. In comparison to the commercial batch hydrogenation with a nickel on kieselguhr catalyst, the DELOXAN supported palladium complex catalyst in combination with sc CO2 as a solvent gives higher space-time-yields, a higher linoleate selectivity and a significantly decreased cis/trans isomerization rate. 

DELOXAN AP II supported platinum catalysts in sc CO2 are less active than DELOXAN AP II supported palladium catalysts, but they show an improved linoleate selectivity and a significantly lower cis-trans isomerization rate. The overall yield of undesirable trans fatty acids is 7.5 GC area-% in the edible oil hardening with a DELOXAN AP II supported 2 wt. % platinum catalyst. In a batch hydrogenation using the commercial powdered nickel on kieselguhr catalysts the undesirable trans fatty acid content was determinded to 40 percent. 

Another common form of silica is diatomaceous earth, also known as kieselguhr. 6 This is a naturally occurring material composed of fossilized diatoms. It contains 70-90% Si02, has 0.2-0.7 im pores and a surface area of about 15-40 m /g. It is a common support for nickel catalysts used in large scale reactions. 

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