Nickel catalyst Nitrobenzene

To about 0.54 g. of 9,10-dihydroanthracene in 25 ml. of ethanol, 8 g. of Raney nickel catalyst was added. After refluxing for 2J hours in an atmosphere of nitrogen, the mixture was filtered and the filtrate was concentrated. On cooling, about 0.33 g. of 1,2,3,4-tetrahydroanthracene was obtained. The mother liquor, when treated with 0.3 g. of s-trinitro-benzene, yielded about 0.25 g. of the 1,2,3,4-tetrahydroanthracene-tri-nitrobenzene complex. The total yield was 81% of the theoretical. When about 0.34 g. of anthracene in 50 ml. of ethanol was treated with 10 g. of Raney nickel, a 71 % yield of the same product was obtained. 

Haloanilines are obtained from halonitrobenzenes preferably by the iron-acid reduction procedure. Nuclear halogenation occurs during the reduction of nitrobenzene by stannous chloride in the presence of acetic anhydride a quantitative yield of p-chloroacetanilide is obtained. Hydrogenation of halonitrobenzenes over Raney nickel catalyst is possible provided that the temperature is kept below 150°, at which point... 

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. 

The aim of the present article is to report the large scale (several hundred grams per gram of active phase) synthesis of uniform carbon nanofibers (average diameter ranging between 40 and 60 nm) by the catalytic decomposition of a mixture of ethane and hydrogen over a nickel catalyst supported on carbon nanotubes. To illustrate their catalytic potential, the as-synthesized carbon nanofibers are subsequently used as catalyst support for palladium in the hydrogenation of nitrobenzene in a liquid phase reaction. 

Hydrogenation of Dinitrotoluene to Toluenediamine. The hydrogenation of the dinitrotoluene mixture to toluenediamines is once again a standard process in aromatic synthesis. This reaction can be carried out with iron and aqueous hydrochloric acid like the reduction of nitrobenzene, but catalytic hydrogenation is preferred (e.g., in methanol with a Raney nickel catalyst at about 100°C and over 50 bars, or with palladium catalysts). 

When Raney nickel catalysts were used, it was found that the intermediate products of reduction absorbed hydrogen at lower rates than did nitrobenzene. The relative rates of hydrogenation were found to be as shown in Table 5-10 It would therefore appear that nitrosobenzene is not one of the intermediate steps in going from nitrobenzene to aniline. 

Working under favorable conditions with a nickel catalyst. Brown and Henke obtained a 95 per cent yield of aniline from nitrobenzene. With a constant rate of flow of nitrobenzene, the yields drop off with too much or too little hydrogen. This fluctuation has been ascribed to over- or underreduction. Since nickel is such an active catalyst for this purpose, reduction of the aniline to cyclohexane and ammonia is known to take place. 

The hydrogenation of nitrobenzene on a Raney nickel catalyst in ethanol has given a scatter diagram when correlated by the Taft equation (see Table IV). However, Finkelshtein and Kuzmina (17,18) have reported very good linear dependence of log k on Av, i.e., on the difference between the maxima of frequences of K absorption bands in... 

Linear poly(A/-methyl-3,6-carbazolylen) (64c) has been prepared by the reaction of 3,6-dibromo-9-methylcarbazole (67a) with the Grignard reagent (67b) in the presence of a complex nickel catalyst [436-438], A brittle film of (67c) can be cast from nitrobenzene solution which shows a conductivity, when doped with I2 or NOBF4, as high as 6 S cm . Doping with iodine induces a postpolymerization reaction which increases its molecular weight and improves mechanical stability. 

The catalyst potential was measured using the following conditions 750 ml glass reactor 15.8 g (0.1 mole) 2-chloro-nitrobenzene 3.0 g Raney nickel (60% in water) 0.02 moles modifier, 550 ml methanol temperature 30°C H2 pressure 1.1 bar 1500 rpm. 

Fig. 2a-d Hydrogenation of 2-chloro-nitrobenzene in presence of different modifiers. Catalyst potential and concentration of reactants and products versus hydrogen uptake (conversion). (Raney nickel methanol 30°C 1.1 bar). 

The catalytic gas-phase hydrogenation processes for nitrobenzene can be carried out using a fixed-bed or a fluidized bed reactor. Bayer and Allied work with nickel sulfide catalysts at 300°C to 475°C in a fixed bed. The selectivity to aniline is more than 99%. The catalytic activity slowly decreases due to carbon... 

Porphyrins are often employed in sensors on account of their ability to act as cation hosts and, with a suitable metal ion coordinated, as redox catalysts. Electropolymerised poly(metalloporphyrin)s have been used as potentiometric anion-selective electrodes [131] and as amperometric electrocatalytic sensors for many species including phenols [132], nitrous oxide [133] and oxygen [134]. Panasyuk et al. [135] have electropolymerised [nickel-(protoporphyrin IX)dimethylester] (Fig. 18.10) on glassy carbon in the presence of nitrobenzene in an attempt to prepare a nitrobenzene-selective amperometric sensor. Following extraction of the nitrobenzene the electrode was exposed to different species and cyclic voltammetric measurements made. A response was observed at the reduction potential of nitrobenzene (the polyporphyrin film acts only to accumulate the analyte and not in a catalytic fashion). Selectivity for nitrobenzene compared with w-nitroaniline and o-nitroto-luene was enhanced compared with an untreated electrode, while a glassy carbon-... 

Some complexes dissociate fully in solution (e.g., 7r-allyl nickel tri-fluoroacetate) whence [63] Rp cc [C2][M]. Donor solvents (triphenyl-phosphite, nitrobenzene) can also coordinate with the metal and influence catalyst dissociation with effects on rate and polymer molecular weight the structure of the polymer may also be affected [173]. 

From an industrial point of view Raney Nickel promoted by thiourea or by iodides is a very attractive catalyst especially in the hydrogenation of halogeno-nitrobenzenes containing chlorine atoms. 

Since active catalysts, such as nickel and the noble metals, are often poisoned by traces of sulfur-containing compounds, it is necessary to purify the feedstock rather rigorously to remove such poisons. It is for this reason that sulfides (e.g., nickel sulfide, molybdenum sulfide) are sometimes found advantageous as catalysts for such systems, since they do not suffer from the same disadvantages as do more active catalysts. A mixture of alumina and nickel sulfide has been claimed to have particularly long life in the reduction of nitrobenzene to aniline at 300 C. ... 

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