Catalysts from nickel

Induction periods and an accelerating stage in the polymerization may result from the presence of impurities which are slowly removed from the system by reaction with the catalyst components. In butadiene polymerization by the soluble catalyst from nickel salicylate/BF3Et2 0/LiBu there is a marked induction from traces of 1,2 butadiene (below 100 p.p.m.) in the monomer [67]. In the absence of 1,2 butadiene polymerization starts immediately. An induction period has been found with the similar catalyst, nickel naphthenate/BF3Et2 0/AlEt3 [68], but the origins of this were not identified. 

Temperature is not the sole parameter that governs drying, as is shown by two examples (Figure 4.2). Komiyama et al. prepared Ni/A Oj catalysts from nickel chloride and found that a heating rate of 10°C min up to llO C led to small particles disseminated all over alumina, whereas a six-fold lower rate resulted in a segregation of matter to the mouth of the pores [41]. In contrast, when the precursor is [Ni(NH3)6](NOj)2, it is a fast heating up to 200°C that results in an e -sheU distribution [31]. 

The selective addition of the second HCN to provide ADN requires the concurrent isomerisation of 3PN to 4-pentenenitrile [592-51 -8] 4PN (eq. 5), and HCN addition to 4PN (eq. 6). A Lewis acid promoter is added to control selectivity and increase rate in these latter steps. Temperatures in the second addition are significandy lower and practical rates may be achieved above 20°C at atmospheric pressure. A key to the success of this homogeneous catalytic process is the abiUty to recover the nickel catalyst from product mixture by extraction with a hydrocarbon solvent. 2-Methylglutaronitrile [4553-62-2] MGN, ethylsuccinonitfile [17611-82-4] ESN, and 2-pentenenitrile [25899-50-7] 2PN, are by-products of this process and are separated from adiponitrile by distillation. 

Tetrahydronaphthalene is produced by the catalytic treatment of naphthalene with hydrogen. Various processes have been used, eg, vapor-phase reactions at 101.3 kPa (1 atm) as well as higher pressure Hquid-phase hydrogenation where the conditions are dependent upon the particular catalyst used. Nickel or modified nickel catalysts generally are used commercially however, they are sensitive to sulfur, and only naphthalene that has very low sulfur levels can be used. Thus many naphthalene producers purify their product to remove the thionaphthene, which is the principal sulfur compound present. Sodium treatment and catalytic hydrodesulfuri2ation processes have been used for the removal of sulfur from naphthalene the latter treatment is preferred because of the ha2ardous nature of sodium treatment. 

Most commercial methanator catalysts contain nickel, supported on alumina, kaolin, or calcium aluminate cement. Sulfur and arsenic are poisons to the catalyst, which can also be fouled by carry-over of solvent from the CO2 removal system. 

The equivalent nickel content of the feed to the FCCU can vary from <0.05 ppm for a weU-hydrotreated VGO to >20 ppm for a feed containing a high resid content. The nickel and vanadium deposit essentially quantitatively on the cracking catalyst and, depending on catalyst addition rates to the FCCU, result in total metals concentrations on the equiUbrium catalyst from 100 to 10,000 ppm. 

Baker, R.T.K, Chemistry and physics of carbon, Marcel Dekker, New York, 14, 1978, Trimm, D.L., The formation and removal of coke from nickel catalyst, Catal. Rev. Sci. Eng., 1977, 16, 155 189. 

The azido mesylate is suspended in absolute ethanol and 80% hydrazine hydrate (3 ml/g of azido mesylate). A small amount (tip of spatula) of Raney nickel (W-2 grade or commercial 50% sponge nickel catalyst from W. R. 

Several products other than 2,2 -biaryls have been isolated following reaction of pyridines with metal catalysts. From the reaction of a-picoline with nickel-alumina, Willink and Wibaut isolated three dimethylbipyridines in addition to the 6,6 -dimethyl-2,2 -bipyridine but their structures have not been elucidated. From the reaction of quinaldine with palladium-on-carbon, Rapoport and his co-workers " obtained a by-product which they regarded as l,2-di(2-quinolyl)-ethane. From the reactions of pyridines and quinolines with degassed Raney nickel several different types of by-product have been identified. The structures and modes of formation of these compounds are of interest as they lead to a better insight into the processes occurring when pyridines interact with metal catalysts. 

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). 

Other potential poisons include zinc, manganese, chlorine, and bromine. A number of metals may be deposited on the catalysts from engine erosion and wear, including copper, chromium, nickel, and iron. The mechanism of poisoning has been reviewed by Maxted (134) and by Butt (135). 

Thiophenes can also be desulfurized to alkenes (RCH2CH=CHCH2R from 115) with a nickel boride catalyst prepared from nickel(II) chloride and NaBILj in methanol.It is possible to reduce just one SR group of a dithioacetal by treatment... 

Arnett, R.L. and Buell, B.O. Magnetic separator for removing nickel-on-kieselguhr catalyst from conjugated diene solutions. US Patent (1956) 2,760,638. 

Bremer, J.W.J. Recovery of nickel catalysts from hydrogenated fats. US Patent (1959) 2,875,220. 

We ivill discuss the reaction of hydrogen and oxygen on transition metals first. This reaction has been extensively studied in our laboratory 18-32) using evaporated metal films as a catalyst. From our previous considerations it follows that as a consequence of the choice of this particular system we must restrict ourselves to certain problems only. We cannot identify the surface species (we can indirectly indicate only some of them) nor understand completely their role in the reaction. Because of the polycrystalline character of the film, all the experimental results are averaged over all the surface. Several new problems thus arise, such as grain boundaries, and, consequently, the exact physical interpretation of these results is almost impossible it is more or less a speculative one. However, we can still get some valuable information concerning the chemical nature of the active chemisorption complex. The experimental method and the considerations will be shown in full detail for nickel only. For other metals studied in our laboratory, only the general conclusions will be presented here. 

Evidence has been collected over the years which strongly indicates that the active species in the oligomerization reactions are nickel-hydride and nickel-alkyl complexes. [This is not necessarily true for catalysts prepared from nickel(II) compounds and organoaluminum compounds having low Lewis acidity, e.g., (C2H5)2A10C2H5 (44).] The majority of the evidence is circumstantial and is discussed below. 

Carpenter-Evans A catalytic process for removing organic sulfur compounds from synthesis gas by hydrogenation to hydrogen sulfide, which is absorbed by iron oxide. The hydrogenation catalyst is nickel sub-sulfide, Ni3S2. Invented by E. V Evans and C. C. Carpenter in England around 1913 and operated in three commercial plants. 

Dimersol E A process for making gasoline from ethylene. The catalyst is a soluble Ziegler-type catalyst containing nickel. Developed by IFP in the 1980s and operated at an undisclosed location since 1988. 

ODORGARD A process for removing odorous gases from air streams by scrubbing with an aqueous solution of sodium hypochlorite in the presence of a proprietary heterogeneous catalyst. The catalyst contains nickel and is based on the HYDECAT catalyst. Developed by ICI Katalco and F. H. H. Valentin. Nine units had been installed in the United Kingdom by 1995. World Patent WO 94/11091. 

Precipitation of the catalyst can be effected by treating the polymer solution with acid/base and/or oxidants. Poloso and Murray [95] proposed a method to recycle the nickel octanoate ((CH3(CH2)6C02)2Ni)/triethylaluminum((C2H5)3Al) catalyst from a styrene-butadiene polymer solution. The polymer solution containing the catalysts was refluxed with 4 wt.% glacial acetic acid (relative to polymer) for 4 h, followed by treatment with 1.4 wt.% anhydrous ammonia. The solution was then filtered through a diatomaceous earth. The nickel content in the polymer was decreased from 310 ppm to 5.6 ppm. 

Fig. 11. CO formation rates determined from reactant conversions and product selectivities in a fixed-bed flow reactor for C02 reforming of CH4. The catalysts were nickel supported on La203, y-Al203, or CaO. Each catalyst contained 17 wt% Ni. Before reaction, the catalyst was reduced in flowing H2 at 773 K for at least 5 h and then at 1023 K for 2 h. Reaction conditions pressure, 1.0 atm temperature, 1023 K feed gas molar ratio, CH4/C02/He = 2/2/6 GHSV, 1,800,000 mL (g catalyst)-1 h-1 (227).

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