Nitrobenzene Conversion

Fig. 5 Comparison of nitrobenzene conversion and aniline selectivity as a function of reaction time for the incipient wetness catalyst [20]...

Figure 5.25 Catalytic activity of a sputtered palladium catalyst. Nitrobenzene conversion ( ) aniline selectivity ( ) [60. ...

Vargaftik, M.N. et al., Catalysis with a Pd giant cluster phenol oxidative carbonylation to diphenul carbonate conjugated with reductive nitrobenzene conversion, J. Mol. Catal. A Chem., 108, 77, 1996. 

The molar selectivity for aniline is up to 99.6 per cent for a nitrobenzene conversion of 99.7 percent The mam impurities are. nitrosobenzene, cydohexylamine, diphenyl-amine, phenyicyclohexylamme and aminophenols. 

Catalyst Irreversible CO uptake (pmol g cat) Nitrobenzene Conversion (mol %) Aniline Yield (mol %)... 

Figure 4. Effect of water on nitrobenzene conversion and reaction selectivity. Selectivity is defined as the ratio of para substituted products to ortho substituted products.

An agitated mixture of benzene and anhydrous K-nitrate irradiated ca. 2 hrs. with tungsten target X-rays in a sealed tube with exclusion of air nitrobenzene. Conversion up to 95%. W. W. Epstein, R. N. Kust, and D. MacGregor, Chem. Commun. 1968, 1190. 

The effect of silver salts, copper acetate and mercury acetate as an additive was studied in the palladium-catalyzed carbonylation of nitrobenzene [17]. The combination of palladium acetate, sliver fluoride, 1,10-phenanthroline and p-toluen-sulfonic acid were found to be highly active and selective yielding nitrobenzene conversion up to 96 %. Copper acetate and mercury acetate are also effective as additives and gave good results. A-phenylcarbamate was produced in the presence of alcohol. 

Environmental aspects, as well as the requirement of efficient mixing in the mixed acid process, have led to the development of single-phase nitrations. These can be divided into Hquid- and vapor-phase nitrations. One Hquid-phase technique involves the use of > 98% by weight nitric acid, with temperatures of 20—60°C and atmospheric pressure (21). The molar ratios of nitric acid benzene are 2 1 to 4 1. After the reaction is complete, excess nitric acid is vacuum distilled and recycled. An analogous process is used to simultaneously produce a nitrobenzene and dinitrotoluene mixture (22). A conversion of 100% is obtained without the formation of nitrophenols or nitrocresols. The nitrobenzene and dinitrotoluene are separated by distillation. 

Dehydrogenation processes in particular have been studied, with conversions in most cases well beyond thermodynamic equihbrium Ethane to ethylene, propane to propylene, water-gas shirt reaction CO -I- H9O CO9 + H9, ethylbenzene to styrene, cyclohexane to benzene, and others. Some hydrogenations and oxidations also show improvement in yields in the presence of catalytic membranes, although it is not obvious why the yields should be better since no separation is involved hydrogenation of nitrobenzene to aniline, of cyclopentadiene to cyclopentene, of furfural to furfuryl alcohol, and so on oxidation of ethylene to acetaldehyde, of methanol to formaldehyde, and so on. 

Until recent years the only syntheses of 3-hydroxy quinoline involved multistep processes, the last step of which consisted of the conversion of 3-aminoquinoline to 3-hydroxyquinoline via the diazonium salt. " Small quantities of quinoline have been oxidized to 3-hydroxyquinoline in low yields by using oxygen in the presence of ascorbic acid, ethylenediaminetetraacetic acid, ferrous sulfate, and i)hosi)halc buffer. The decarboxylation of 3-hydroxycinchoninic, acid in boiling nitrobenzene has been re-... 

Concentration of nitrobenzene depends on both temperature and conversion. If u is the volumetric flowrate at a point in the reactor where the concentration is C, and Ug is the value at the entrance, the conversion of nitrobenzene is... 

Longitudinal temperature profile and conversion in a reactor for the hydrogenation of nitrobenzene... 

The six-position may be functionalized by electrophilic aromatic substitution. Either bromination (Br2/CH2Cl2/-5°) acetylation (acetyl chloride, aluminum chloride, nitrobenzene) " or chloromethylation (chloromethyl methyl ether, stannic chloride, -60°) " affords the 6,6 -disubstituted product. It should also be noted that treatment of the acetyl derivative with KOBr in THF affords the carboxylic acid in 84% yield. The brominated crown may then be metallated (n-BuLi) and treated with an electrophile to form a chain-extender. To this end, Cram has utilized both ethylene oxide " and dichlorodimethyl-silane in the conversion of bis-binaphthyl crowns into polymer-bound resolving agents. The acetylation/oxidation sequence is illustrated in Eq. (3.54). 

The reaction rates cannot be set as high as intrinsically possible by the kinetics, because otherwise heat removal due to the large reaction enthalpies (500-550 kj mol ) will become a major problem [17, 60, 61]. For this reason, the hydrogen supply is restricted, thereby controlling the reaction rate. Otherwise, decomposition of nitrobenzene or of partially hydrogenated intermediates can occur ]60], The reaction involves various elemental reactions with different intermediates which can react with each other ]60], At short reaction times, the intermediates can be identified, while complete conversion is achieved at long reaction times. The product aniline itself can react further to give side products such as cyclohexanol, cyclohexylamine and other species. 

GL 18] ]R 1] ]P 19d] Using a high concentration of nitrobenzene, deleterious effects on the catalysts could be determined (1.0 mol 1 60 °C 1 bar 0.5 ml min ) [60, 62]. Both conversion and selectivity were lower compared with processing at 0.04 mol concentration, being 41 and 68%, respectively. The catalyst surface turned dark after prolonged operation and particles settled (8.5 h). As a positive result, the (low) activity remained fairly stable over this period. 

Cyanide and thiocyanate anions in aqueous solution can be determined as cyanogen bromide after reaction with bromine [686]. The thiocyanate anion can be quantitatively determined in the presence of cyanide by adding an excess of formaldehyde solution to the sample, which converts the cyanide ion to the unreactive cyanohydrin. The detection limits for the cyanide and thiocyanate anions were less than 0.01 ppm with an electron-capture detector. Iodine in acid solution reacts with acetone to form monoiodoacetone, which can be detected at high sensitivity with an electron-capture detector [687]. The reaction is specific for iodine, iodide being determined after oxidation with iodate. The nitrate anion can be determined in aqueous solution after conversion to nitrobenzene by reaction with benzene in the presence of sulfuric acid [688,689]. The detection limit for the nitrate anion was less than 0.1 ppm. The nitrite anion can be determined after oxidation to nitrate with potassium permanganate. Nitrite can be determined directly by alkylation with an alkaline solution of pentafluorobenzyl bromide [690]. The yield of derivative was about 80t.with a detection limit of 0.46 ng in 0.1 ml of aqueous sample. Pentafluorobenzyl p-toluenesulfonate has been used to derivatize carboxylate and phenolate anions and to simultaneously derivatize bromide, iodide, cyanide, thiocyanate, nitrite, nitrate and sulfide in a two-phase system using tetrapentylammonium cWoride as a phase transfer catalyst [691]. Detection limits wer Hi the ppm range. 

Nitrobenzene is fed to the reactor as a vapour, with three times the stoichiometric quantity of hydrogen. The conversion of the nitrobenzene, to all products, is 96 per cent, and the yield to aniline 95 per cent. 

Continuous Multicomponent Distillation Column 501 Gas Separation by Membrane Permeation 475 Transport of Heavy Metals in Water and Sediment 565 Residence Time Distribution Studies 381 Nitrification in a Fluidised Bed Reactor 547 Conversion of Nitrobenzene to Aniline 329 Non-Ideal Stirred-Tank Reactor 374 Oscillating Tank Reactor Behaviour 290 Oxidation Reaction in an Aerated Tank 250 Classic Streeter-Phelps Oxygen Sag Curves 569 Auto-Refrigerated Reactor 295 Batch Reactor of Luyben 253 Reversible Reaction with Temperature Effects 305 Reversible Reaction with Variable Heat Capacities 299 Reaction with Integrated Extraction of Inhibitory Product 280... 

Cytosol conversion of styrene 7,8 epoxide to styrene 7,8 glycol Sequential conversion of nitrobenzene to aniline... 

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