Vapor-phase nitrations

Zeohtes have recendy been employed as soHd catalysts for the vapor-phase nitration of aromatics with nitric acid. Additional research is required to improve yields and to niinimi2e loss of catalytic activity as the nitration progresses (see Molecularsieves). 

Chemistry. Free-radical nitrations consist of rather compHcated nitration and oxidation reactions (31). When nitric acid is used in vapor-phase nitrations, the reaction of equation 5 is the main initiating step where NO2 is a free radical, either -N02 or -ON02. Temperatures of >ca 350° are required to obtain a significant amount of initiation, and equation 5 is the rate-controlling step for the overall reaction. Reactions 6 and 7 are chain-propagating steps. 

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. 

Several patents have been issued that offer improvements in chloronitrobenzene production. Most are vapor-phase nitrations using soHd catalysts. Table 8 Hsts some of these results. 

The only method utilized commercially is vapor-phase nitration of propane, although methane (70), ethane, and butane also can be nitrated quite readily. The data in Table 5 show the typical distribution of nitroparaffins obtained from the nitration of propane with nitric acid at different temperatures (71). Nitrogen dioxide can be used for nitration, but its low boiling point (21°C) limits its effectiveness, except at increased pressure. Nitrogen pentoxide is a powerful nitrating agent for alkanes however, it is expensive and often gives polynitrated products. 

NMe is now commercially available and is prepd by the vapor phase nitration of methane at a ratio of 9 moles of methane to I mole of nitric acid at 475° and a residence time of 0.18sec (Ref 12) or by the similar nitration of aliphatic hydrocarbons (Ref 8). Other prepns are from Me sulfate and Na nitrite (Ref 26) by the oxidn of Me amine with dinitrogen trioxide in the gas phase or in methylene chloride, yield 27%... 

L.F. Albright C. Hansen, Eds, Industrial and Laboratory Nitrations , ACS Symposium Series 22, ACS, Washington, DC (1976). Excellent modern review. Ten chapters emphasize various aspects of the chemistry and mechanism of nitrations, including oxidation and ipso-nitration side reactions. Six chapters discuss the chemistry and physical transfer steps between phases. Eight chapters discuss plant operation-improvements, safety features, and new operations. The final chapter is devoted to vapor phase nitrations... 

Titov and co-workers, although conceding the validity of the ionic nitration mechanism for liq phase nitrations with coned acids, believe that many nitrations occur via a free-radical mechanism involving the free radicals (at any rate molecules having an unpaired electron) N02, N03, and NO. For vapor phase nitration of hydrocarbons, nitration of side chains of aromatic compds in... 

Probably the main point of disagreement between the Ingold and Titov schools arises in the vapor phase nitration of hydrocarbons. Titov believes that this occurs via reaction (19), (20), (21), etc. Ingold et al (Ref 77), on the basis of some sound kinetics, propose the sequence HN03 = HO + NOp HO+ R- H20 + R R + HN03 ->RN02 (or RONO) + OH R + HNO3 -+ROH + NO2... 

F. SI sol in w (1.4ml/100ml) 0.5ml w dissolves in 100ml of 1-Nitropropane misc with many org solvents. Prepd by the vapor-phase nitration of propane (Refs 1 a 3)... 

Another important development in the field was the discovery of the vapor-phase nitration in the 1930s by H. Hass and his students at Purdue University. It led in 1940 to the commercial production of lower molecular weight nitroalkanes [Cl to C4] at a pilot plant of the Commercial Solvents Corporation in Peoria, Illinois. In the organic nitro chemistry era of the fifties and early sixties, a great emphasis of the research was directed towards the synthesis of new compounds that would be useful as potential ingredients in explosives and propellants. 

U.S. consumption pattern 1999, 3 619t U.S. producers, 3 610t vapor-phase nitration of, 17 257 vinyl chloride reactions with, 25 632 world production by country, 3 611-612t Benzene-based catalyst technology, 15 500 Benzene-based fixed-bed process technology, 15 505-506 Benzene chlorination process, of phenol manufacture, 18 751 m-Benzenedisulfonic acid, 3 602 p-Benzenedisulfonic acid, 3 602 Benzene feedstock, 23 329 Benzene hexachloride, 3 602 Benzene manufacture, toluene in, 25 180-181... 

V.Y Shtem, KhimKinetTsepnyeReakts, InstKhimFizAkadNauk 1966, 286—322 CA 66, 54671(1967) (Review with 33 refs) (Vapor phase nitration of alkanes by nitrogen dioxide)... 

Acetone, Nitration. Krauz Stepanek(Ref 1) attempted to prepare terrani from ethane by nitration of acetone, but failed, instead, they obtained (after treating the resulting product with a silver salt) a very expl solid claimed to be Ag salt of acetylmethylnitrolic acid, also called a-nitro - a -isonitroso-acetone. Hass Hudgin(Ref 3) nitrated acet, using a vapor-phase nitration technique described in Ref 2. The high-boiling fractn from the nitration gave an odor of acetic acid, an acidic reaction in aq soln, a red color with ferric chloride and a yel salt with Ag nitrate soln,... 

It was claimed by Henry(Ref 2) that 0. de Battice prepd nitroacetone in 1895 in Belgium by oxidation of nitroisopropanol with chromic mixture. Henry described the compd as a coi, mobile liq with a sharp odor, a 1.070 at 14°, bp 152° at 767 mm and insol in w. Lucas c]aimed(Ref 3) that the compd described by Henry was not nitroacetone, but this statement was disputed by Henry(Ref 4). Harries also claimed(Ref 5) that the compd described by Henry is not nitroacetone More recently, Hass Hudgin(Ref 7) claimed that they had isolated some nitroacetone from the high-boiling fraction of the vapor-phase nitration of acetone but it is not clear from their paper whether the substance was liq or solid. Hurd NilsonfRef 8) prepd nitroacetone as pale-green crysts, mp 47°, by oxidizing 1—nitro—2—propanol with sodium dichromate and sulfuric acid. The yield was (5% of theoretical. The explosifcility of this compd was not mentioned... 

All four compounds are produced by the vapor-phase nitration of propane.197-199 Nitroalkanes are important as solvents and intermediates.199... 

Vapor Phase Nitration. See under Nitration in Vol 8, N48-R N56-L, and under Nitro-methane , M69-R... 

Solid catalysts - [CATALYSIS] (Vol 5) -for vapor-phase nitration [NITRATION] (Vol 17)... 

A continuous vapor-phase nitration of cellulosic material in the form of a sheet was developed in the USA by the Brown Paper Co, Berlin, New Hampshire. No description of this method is available Refs l)J.Downie, BritP 1813 (1864) A-Nobel,... 

At a time when the only practicable methods for the preparation of nitromethane were the interaction of methyl iodide with silver nitrite and the Kolbe reaction from chloracetic acid, the explosive was far too expensive to merit consideration. The present cheap and large scale production of nitromethane by the vapor-phase nitration of methane and of ethane has altered the situation profoundly. Trimethylolnitromethane trinitrate is an explosive which can now be produced from coke, air, and natural gas. Nitromethane too has other interest for the manufacturer of explosives. It may be used as a component of liquid explosives, and it yields on reduction methylamine which is needed for the preparation of tetryl. 

Vapor-phase nitration of paraffin hydrocarbons, particularly propane, can be brought about by uncatalyzed contact between a large excess of hydrocarbon and nitric acid vapor at around 400°C, followed by quenching. A multiplicity of nitrated and oxidized products results from nitrating propane nitromethane, nitroethane, nitropropanes, and carbon dioxide all appear, but yields of useful products are fair. Materials of construction must be very oxidation-resistant and are usually of ceramic-lined steel. The nitroparaffins have found limited use as fuels for race cars, submarines, and model airplanes. Their reduction products, the amines, and other hydroxyl compounds resulting from aldol condensations have made a great many new aliphatic syntheses possible because of their ready reactivity. 

Bertea, L. E., Kouwenhoven, H. W. and Prins, R. Vapor-phase nitration of benzene over modified mordenite catalysts, Appl. Catal., A, 1995, 129, 229-250. 

Nitroparaffins are produced by vapor phase nitration with nitric acid vapor. Nitroethane is also prepared in this way. The individual reaction products (nitromethane, nitroethane, nitropropane) must then be separated by distillation. 

Accdg to Hibshman et al (Re f 4), vapor-phase nitration of ethane produces a mixture of C2H5NO with CH8N02. In the lab method of prepn by Desseigne Giral (Ref 8), pure NEt is produced starting from ethanol, oleum and Na nitrate. It is stated, however, that the method is not suitable for industrial purposes because it cannot compete with vapor-phase nitration of propane which renders... 

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