Nickel-aluminum-alumina catalyst

A novel nickel-aluminum-alumina catalyst was used in this work. The same catalyst was used in all tests although several different batches were prepared. Since a standardized procedure was used, variations in catalyst composition were not great and activity was reproducible. Because details of the preparation and composition are presented in several patent applications, no further discussion of the catalyst is given. 

Tetrahydrofurfuryl alcohol reacts with ammonia to give a variety of nitrogen containing compounds depending on the conditions employed. Over a barium hydroxide-promoted skeletal nickel—aluminum catalyst, 2-tetrahydrofurfur5iarnine [4795-29-3] is produced (113—115). With paHadium on alumina catalyst in the vapor phase (250—300°C), pyridine [110-86-1] is the principal product (116—117) pyridine also is formed using Zn and Cr based catalysts (118,119). At low pressure and 200°C over a reduced nickel catalyst, piperidine is obtained in good yield (120,121). 

The predominant process for manufacture of aniline is the catalytic reduction of nitroben2ene [98-95-3] ixh. hydrogen. The reduction is carried out in the vapor phase (50—55) or Hquid phase (56—60). A fixed-bed reactor is commonly used for the vapor-phase process and the reactor is operated under pressure. A number of catalysts have been cited and include copper, copper on siHca, copper oxide, sulfides of nickel, molybdenum, tungsten, and palladium—vanadium on alumina or Htbium—aluminum spinels. Catalysts cited for the Hquid-phase processes include nickel, copper or cobalt supported on a suitable inert carrier, and palladium or platinum or their mixtures supported on carbon. 

Alumina-supported nickel catalysts are an excellent example for the advantages of and the problems associated with coprecipitation processes for the manufacture of catalysts. Such catalysts are accessible via several pathways, as impregnation, deposition/precip-itation, coprecipitation from alumina gels, and more conventional coprecipitation routes. Also, for coprecipitation, different routes are possible, the first examples originating from the 1920s [48]. Starting from the nitrate solutions of nickel and aluminum, there are at least three different routes ... 

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While catalyst activity is generally inversely related to the amount of aluminum and alumina present it is not desirable to remove all of these materials from the nickel. It has been proposed that some aluminum in the nickel crystal lattice creates the defect sites responsible for catalytic activity. The alumina appears to prevent the sintering of the nickel particles. With the 20% alumina that is found in the commercial catalyst, heating to 500°C results in only a 20% reduction in surface area. When only 1% alumina is present there is a 50% reduction in surface area at this temperature but no change in surface area on heating to 250°C. 

Although palladium occupies the dominant position in semi-hydrogenation catalysts, it is by no means the only metal suitable for formulation into a viable catalyst. Mention has already been made of the nickel boride alternatives, with or without copper promotion, for example. Other examples include the skeletal catalyst Raney nickel [69], alumina-supported nickel [70], and aluminum phosphate-supported nickel [71] (Eqs 21 and 22) ... 

Reduction of quinoxaline with sodium in THF at 20° yields a deep-purple solution from which 1,4-dihydroquinoxaline is isolated. Reduction with either sodium in refluxing alcohol or lithium aluminum hydride in ether gives 1,2,3,4-tetrahydroquinoxaline. Hydrogenation of quinoxaline over a 5% rhodium-on-alumina catalyst at 100° and 136 atm or over freshly prepared Raney nickel W-6 under similar conditions gives meso-(cis)-decahydroquinoxaline. ° However hydrogenation of quinoxaline over a palladium-on-charcoal catalyst at 180° and 50 atm gives dl-(/rans)-decahydroquinoxaline." ... 

Silver granules are used to oxidize methanol to formaldehyde. Raney nickel is produced by leaching aluminum from a nickel/aluminum alloy with alkali solution. Not all of the alumina is removed and the catalyst may be regenerated a number of times by alkali treatment. 

Other Higher Oleiins. Linear a-olefins, such as 1-hexene and 1-octene, are produced by catalytic oligomerization of ethylene with triethyl aluminum (6) or with nickel-based catalysts (7—9) (see Olefins, higher). Olefins with branched alkyl groups are usually produced by catalytic dehydration of corresponding alcohols. For example, 3-methyl-1-butene is produced from isoamyl alcohol using base-treated alumina (15). 

Hydrotreating also produces some residuals in the form of spent catalyst fines, usually consisting of aluminum silicate and some metals (e.g., cobalt, molybdenum, nickel, tungsten). Spent hydrotreating catalyst is now listed as a hazardous waste (K171) (except for most support material). Hazardous constituents of this waste include benzene and arsenia (arsenic oxide, AS2O3). The support material for these catalysts is usually an inert ceramic (e.g., alumina, AI2O3). 

The composition of the catalyst will, of course, vary with the method of preparation. Aubrey (23) indicates the following composition for his catalyst Al 1-3%, Fe 1%, Cu 0.1%, Co 0.05%, Mn 0.04%. The aluminum content is a function of the duration of the treatment with the alkali. Paul (6) has used catalysts which titrated to 17 % aluminum. Heublen (24) has used catalysts even richer in aluminum. Adkins and Billica (11) reported their W-6 catalyst to contain 11% aluminum, the remainder being nickel. Ipatieff and Pines (25), however, found 21% alumina, 1.36% aluminum, 0.5% sodium aluminate, and about 77% nickel in W-6 catalyst. 

If a carrier is to be incorporated in the final catalyst, the original precipitation is usually carried out in the presence of a suspension of the finely divided support or, alternatively, a compound or suspension, which will eventually be converted to the support, may initially be present in solution. Thus, a soluble aluminum salt may be converted to aluminum hydroxide during precipitation and ultimately to alumina. Alternatively, a supported nickel catalyst could be prepared from a solution of nickel nitrate, containing a suspension of alumina, by precipitation of a nickel hydroxide with ammonia. 

Fumeaux et al. [1987] used porous alumina membrane reactors to hydrogenate ethene to form ethane at 200X with Ft or Os as the catalyst impregnated in the alumina membranes. Conversion to ethane was detected but no data was provided. Suzuki [1987] tested porous stainless steel and nickel-aluminum alloys as membrane reactors for hydrogenation reactions. Hydrogenation of 2-butenc with stainless steel as the membrane... 

Abbattista et al. (26) found that phosphorus addition prevents crystallization of the y-alumina phase and the transformation from y- to a-alumina in the system AI2O3 —AIPO4 (Fig. 23). More precisely, Morterra et al. (77) reported that phosphates do not affect the phase transition from low-temperature spinel alumina (y-alumina) to high-temperature spinel aluminas 8 and 6 phases) but delay the transition of 8 and 9 to a-alumina (corundum). Stanislaus et al 46) also reported that phosphorus significantly improves the thermal stabihty of the y-alumina phase in P/Al catalysts. However, the same authors found that the positive effect of phosphorus seems to be canceled in the presence of molybdenum due to the formation of aluminum molybdate. Thermal treatments of MoP/Al catalysts at temperatures >700°C result in a considerable reduction of SSA and mechanical strength. The presence of phosphorus does not prevent the reaction between the molybdenum oxo-species and alumina since the interaction between molybdates and phosphates is weak. The presence of nickel does not obviously affect the positive effect of phosphorus in terms of thermal stability 46). On the other hand, Hopkins and Meyers 78) reported that the thermal stability of commercial CoMo/Al and NiMo/Al catalysts is improved by the addition of phosphorus. 

Chemically these catalysts contain metallic nickel along with 1-8% aluminum and up to 20% aluminum oxide or hydroxide. The surface is 50-100% metallic nickel which is present in an fee crystalline lattice, the same crystal orientation found for the bulk nickel. The use of low hydroxide ion concentrations and reaction temperatures in the reaction with the alloy gives catalysts containing more aluminum and aluminum oxide. The alumina in these preparations is occluded in the metallic skeleton and is difficult to remove even when later exposed to higher hydroxide concentrations. High temperature digestion is needed to remove all of the alumina from these catalysts. 

Most steam-reforming catalysts are based on nickel as the active material. Also, cobalt and noble metals catalyze the steam-reforming reaction, but they are generally too expensive to find widespread use. A number of different carriers including alumina, magnesium-aluminum spinel, zirconia, and calcium aluminate are employed. 

Monoliths made of metal foils can also be used as substrates in combustion catalysts [19, 20]. The metal is generally an iron- or nickel-based steel containing small amounts of aluminum. The aluminum diffuses to the surface on heating and oxidizes to form an adherent alumina layer. This alumina layer gives the alloy high oxidation resistance and is essentially self-healing as it arises from diffusion from the bulk material. It also provides good adhesion for the alumina washcoat. 

The following nickel-carrier catalysts have been described nickel-kieselguhr,169 nickel-pumice,170 nickel-kieselguhr containing thorium oxide,171 nickel on magnesium oxide, barium oxide, or beryllium oxide,172 nickel on aluminum oxide,173 and nickel-zinc oxide-barium oxide-chromium oxide.174 Other carriers for nickel catalysts are active charcoal, silica, fuller s earth, and oxides such as magnesia, alumina, and bauxite. 

Recent patent disclosures by the Standard Oil Co. of Indiana indicate that their process for the polymerization of ethylene is also a relatively low-pressure process, and the following process information is based on these disclosures. The polymerization process is a fixed-bed process employing a prereduced catalyst, ethylene pressures of 809-1,000 psi, and temperatures somewhat greater than 200°C. The metal oxides (such as nickel, cobalt, and molybdenum) can be supported on either charcoal or alumina, and materials such as lithium aluminum hydride, boron, alkali metals, and alkaline-earth hydrides may be used as promotors. Variations of this process are reported to produce polyethylene resins with densities from 0.94-0.97. 

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