Nickel-based catalysts

It is used in certain nickel-based alloys, such as the "Hastelloys(R)" which are heat-resistant and corrosion-resistant to chemical solutions. Molybdenum oxidizes at elevated temperatures. The metal has found recent application as electrodes for electrically heated glass furnaces and foreheaths. The metal is also used in nuclear energy applications and for missile and aircraft parts. Molybdenum is valuable as a catalyst in the refining of petroleum. It has found applications as a filament material in electronic and electrical applications. Molybdenum is an... 

Fresh reducing gas is generated by reforming natural gas with steam. The natural gas is heated in a recuperator, desulfurized to less than 1 ppm sulfur, mixed with superheated steam, further preheated to 620°C in another recuperator, then reformed in alloy tubes filled with nickel-based catalyst at a temperature of 830°C. The reformed gas is quenched to remove water vapor, mixed with clean recycled top gas from the shaft furnace, reheated to 925°C in an indirect fired heater, and injected into the shaft furnace. For high (above 92%) metallization a CO2 removal unit is added in the top gas recycle line in order to upgrade the quaUty of the recycled top gas and reducing gas. 

Steam Reformings of Natural Gas. This route accounts for at least 80% of the world s methanol capacity. A steam reformer is essentially a process furnace in which the endothermic heat of reaction is provided by firing across tubes filled with a nickel-based catalyst through which the reactants flow. Several mechanical variants are available (see Ammonia). 

Butene. Commercial production of 1-butene, as well as the manufacture of other linear a-olefins with even carbon atom numbers, is based on the ethylene oligomerization reaction. The reaction can be catalyzed by triethyl aluminum at 180—280°C and 15—30 MPa ( 150 300 atm) pressure (6) or by nickel-based catalysts at 80—120°C and 7—15 MPa pressure (7—9). Another commercially developed method includes ethylene dimerization with the Ziegler dimerization catalysts, (OR) —AIR, where R represents small alkyl groups (10). In addition, several processes are used to manufacture 1-butene from mixed butylene streams in refineries (11) (see BuTYLENEs). 

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). 

Feed Ga.s Purifica.tion. Because nickel-based reforming catalysts are quite sensitive to sulfur, halogen, and heavy metal poisons which may be found ia natural gas, a feedstock purification system is normally required. Sulfur compounds, ia both organic and inorganic forms, are the most common... 

The methanation reaction is carried out over a catalyst at operating conditions of 503—723 K, 0.1—10 MPa (1—100 atm), and space velocities of 500—25,000 h . Although many catalysts are suitable for effecting the conversion of synthesis gas to methane, nickel-based catalysts are are used almost exclusively for industrial appHcations. Methanation is extremely exothermic (AT/ qq = —214.6 kJ or —51.3 kcal), and heat must be removed efficiently to minimise loss of catalyst activity from metal sintering or reactor plugging by nickel carbide formation. 

Earlier catalysts were based on cobalt, iron, and nickel. However, recent catalytic systems involve rhodium compounds promoted by methyl iodide and lithium iodide (48,49). Higher mol wt alkyl esters do not show any particular abiUty to undergo carbonylation to anhydrides. 

Polymers containing 90-98% of a c 5-1,4-structure can be produced using Ziegler-Natta catalyst systems based on titanium, cobalt or nickel compounds in conjuction with reducing agents such as aluminium alkyls or alkyl halides. Useful rubbers may also be obtained by using lithium alkyl catalysts but in which the cis content is as low as 44%. 

Anilines have been reduced successfully over a variety of supported and unsupported metals, including palladium, platinum, rhodium, ruthenium, iridium, (54), cobalt, and nickel. Base metals require high temperatures and pressures (7d), whereas noble metals can be used under much milder conditions. Currently, preferred catalysts in both laboratory or industrial practice are rhodium at lower pressures and ruthenium at higher pressures, for both display high activity and relatively little tendency toward either coupling or hydrogenolysis,... 

Functionalized polyethylene would be of great industrial importance, and if synthetic methods to control the microstructure of functionalized polymers using transition-metal-based catalysis are developed, it would significantly broaden the utility and range of properties of this class of polymers. Recent progress in the field of late transition metal chemistry, such as Brookliart s use of nickel-based diimine catalysts, has enabled the copolymerization of ethylene with functional a-olefins.29 However, these systems incorporate functionalized olefins randomly and with limited quantity (mol percent) into the polymer backbone. 

Many late transition metals such as Pd, Pt, Ru, Rh, and Ir can be used as catalysts for steam reforming, but nickel-based catalysts are, economically, the most feasible. More reactive metals such as iron and cobalt are in principle active but they oxidize easily under process conditions. Ruthenium, rhodium and other noble metals are more active than nickel, but are less attractive due to their costs. A typical catalyst consists of relatively large Ni particles dispersed on an AI2O3 or an AlMg04 spinel. The active metal area is relatively low, of the order of only a few m g . ... 

The Oxidative Transformation of Methane over the Nickel-based Catalysts Modified by Alkali Metal Oxide and Rare Earth Metal Oxide... 

We expected to control the direction of OTM reaction over NiO by sur ce modification, namely making use of the interaction between NiO and other conq>onents to beget a synergistic effect. In this paper, two completely different behaviors of the oxidative transformation of methane were performed over the nickel-based catalysts because of the different modifications by alkali metal oxide and rare earth metal oxide and the different interactions between nickel and supports. Furthermore, the two completely different reactions were related with the acid-base properties of catalysts and the states of nickel present. 

In a word, POM and OCM reactions proceed at different active sites with different reaction intermediates and reaction mechanisms over the nickel-based catalysts proposed as follows ... 

Two conqiletely different behaviors of oxidative transformation of methane, namely the Oxidative Coupling of Methane to C2 Hydrocarbons(OCM) and the Partial Oxidation of Methane to Syngas(POM), were performed and related over the nickel-based catalysts due to different modification and different supports. It is concluded that the acidic property favors keeping the reduced nickel and the reduced nickel is necessary for POM reaction, and the bade property frvors keeping the oxidized nickel and the oxidized mckel is necessary for OCM reaction. POM and OCM reactions proceed at different active sites caused by different... 

The chemical events described above are the basis for the removal of arsines (R3 As) in crude oil or in raw gas condensates, which are known to cause major environmental pollution, equipment corrosion and reduction of catalyst life time (including automotive converters). It was recently demonstrated that these compounds can be completely removed by feedstock hydrotreatment on nickel-based catalysts under FI2 at 160-200 °C [140]. 

In 2006, Poe et al. reported a cascade reaction employing two incompatible catalysts, one of which was microencapsulated [19]. In this case, an organic amine was encapsulated and used in conjunction with a nickel-based Lewis acid catalyst (Scheme 5.4). 

Without microencapsulation, precipitation of both catalysts rendered them inactive (Scheme 5.5). Moreover, the addition of the second nickel-based catalyst (Cat. 2)... 

Dehydrogenation of ethane over vanadium, cobalt and nickel based catalysts... 

Fig. 1 compares the activities of vanadium-, cobalt- and nickel- based catalysts in ODH of ethane. Representative catalysts contained between 2.9 and 3.9 wt.% of metal. It is to be pointed out that metal oxide-like species was not present at any of the catalysts, as its presentation is generally the reason in the activity-selectivity decrease. The absence of metal oxide-like species was evidenced by the absence of its characteristic bands in the UV-Vis spectra of hydrated and dehydrated catalysts (not shown in the Figure). The activity of catalysts was compared (i) at 600 °C, (ii) using reaction mixture of 9.0 vol. % ethane and 2.5 vol. % oxygen in helium, and (iii) contact time W/F 0.12 g. i.s.ml 1. These reaction conditions represent the most effective reaction conditions for V-HMS catalysts [4] The ethane conversions, the ethene yields and the selectivity to ethene varied between 13-30 %, 5-16 %, and 37-78 %, respectively, depending on the type of metal species (Co, Ni, V) and support material (A1203, HMS, MFI). 

Li, Y. et al., Simultaneous production of hydrogen and nanocarbon from decomposition of methane on nickel-based catalyst, Energy Fuel, 14,1188, 2000. 

The feasibility of carbon-supported nickel-based catalysts as the alternative to the platinum catalyst is studied in this chapter. Carbon-supported nickel (Ni/C, 10 wt-metal% [12]), ruthenium (Ru/C, 10 wt-metal% [12]), and nickel-ruthenium composite (Ni-Ru/C, 10 wt-metal%, mixed molar ratio of Ni/Ru 0.25,1,4, 8, and 16 [12]) catalysts were prepared similarly by the impregnation method. Granular powders of the activated carbon without the base pretreatment were stirred with the NiCl2, RuC13, and NiCl2-RuCl3 aqueous solutions at room temperature for 24 h, respectively. Reduction and washing were carried out in the same way as done for the Pt/C catalyst. Finally, these nickel-based catalysts were evacuated at 70°C for 10 h. 

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