M-xylene oxidation

Upon m-xylene oxidation, the above band of m-tolualdehyde disappears near 523 K, while a couple of strong and broad bands is grown near 1530 and 1430 cm. These bands are typical of carboxylates and are again observed, with very weak band shifts, upon oxidation of all methyl-benzenes, as well as of the corresponding aromatic aldehydes. They can be assigned predominantly (if not entirely) to benzoate and toluate anions (28) (in Figure 2, meta-toluate anions). These bands raise their maximum near 523 K in all cases and suddenly disappear above 673 K, when gas-phase CO2 begins to be detectable. 

However, features belonging to other species not involved in this path are also observed upon m-xylene oxidation in Near 433 K two other bands are clearly observed at 1710 and 1670 cm. A feature near 1700 cm persists also near 673 K when a very strong and complex absorption pattern becomes detectable in the 1900-1700 cm region. In this region the couples of bands due to symmetric and asymmetric C=0 stretchings of the 0=C-0-C=0 system of cyclic anhydrides typically fall. The... 

Isophthalic acid by m-Xylene oxidation Generic MMlb/y 160 300 9.914 0.6... 

Fig. 1 High ( ) and low (o) activity states of Pd catalysts in m-xylene oxidation. Contact time 0.06 s temperature ramp 5 C min" T heating, i cooling. Catalyst catalyst (III) m-xylene concentration 0.065 vol. % oxygen concentration 40 vol. % (A) CO concentration.

Fig. 2 The effect of hydrogen concentration on the m-xylene oxidation to CO2. 0.3% m-xylene/20% oxygen mixture in nitrogen over catalyst (II) at 170°C, contact time 0.06 sec.

Petal, J., Ollis, D., 1992, Heterogenous photocatalytic oxidation of gas phase organics for air purification acetone, 1-butanol, biityraldehyde, formaldehyde, m-xylene oxidation, J. of Cataly.sis, 136 554-565... 

Colourless crystals, m.p. 345-347" C with sublimation, obtained by oxidation of m-xylene. 

The oxidation of m-xylene produces isophthalic acid. The reaction occurs in the liquid-phase in presence of ammonium sulfite ... 

Iodosobiphenyl, 43, 61 4-Iodosobiphenyl diacetate, 43, 64 o-Iodosophenetole, 43, 61 o-Iodosophenetole diacetate, 43, 64 m-Iodosotoluenc, 43, 61 o-Iodosotoluene, 43, 61 /y-Iodosotoluene, 43, 61 m-Iodosotoluene diacetate, 43, 64 o-Iodosotoluene diacetate, 43, 64 p-Iodosotoluene diacetate, 43, 64 2-lodoso-iB-xylene, 43, 61 2-Iodoso-J>-xylene, 43, 61 4-Iodoso-i -xyIene, 43, 61 2-Iodoso-m-xylene diacetate, 43,64 4-Iodoso-m-xylene diacetate, 43, 64 2-Iodoso- -xylene diacetate, 43, 64 N-Iodosuccinimide, 42, 73 Iodoxyarenes by oxidation of aryl iodides, 43, 66... 

Harms G, K Zengle, R Rabus, F Aeckersberg, D Minz, R Rossell6-Mora, F Widdel (1999) Anaerobic oxidation of o-xylene, m-xylene, and homologous alkylbenzenes by new types of sulfate-reducing bacteria. Appl Environ Microbiol 65 999-1004. 

Seyfried B, G Glod, R Schocher, A Tschech, J Zeyer (1994) Initial reactions in the anaerobic oxidation of toluene and m-xylene by denitrifying bacteria. Appl Environ Microbiol 60 4047-4052. 

The products for which the cyclo-C4 isomerization intermediate has been suggested, can also be explained by a sequence of vinyl insertions. Thus, two vinyl insertions would be adequate to explain the formation of m-xylene from 2,3,4-trimethylpentane. Although we have seen in previous sections that extensive reaction sequences are possible on platinum, isomerization by a single vinyl insertion process on chromium oxide is relatively difficult, and the chance of two occurring in sequence would therefore be expected to be very low. In fact, the proportion of m-xylene is comparable to that of o- and p-xylene. 

Reaction of glycosyl thioimidate 79 with aa -dibromo-m-xylene in the presence of NaH as a base and 15-crown-5 as a supporting reagent allowed the intermediate 80 (Scheme 4.88). Treatment of the diol 81 with dibutyltin oxide in dry toluene and then reaction with 80 in the presence of tetrabutylammonium iodide afforded the desired O-linked intermediate 82. Activation of this compound with NIS-TMSOTf afforded 83 in a good yield. Hydrogenolysis followed by acetylation gave the desired disac-... 

The presence of two methyl groups in m-xylene makes it a more reactive substrate than toluene, but as a consequence, this substrate is more susceptible to oxidation. Therefore, the nitration of m-xylene requires lower temperatures and the use of less concentrated mixed acid. In fact, the nitration of either 2,4- or 2,6-dinitro-m-xylenes to 2,4,6-trinitroxylene (TNX) can be achieved with mixed acid containing up to 10 % water. TNX is a less powerful explosive than TNT and has a poor oxygen balance (—78.4 %). 

Trinitrobenzene is present in crude TNT manufactured by mixed acid nitration and results from methyl group oxidation followed by decarboxylation." In fact, a convenient method for the synthesis of 1,3,5-trinitrobenzene involves oxidation of 2,4,6-trinitrotoluene with a solution of sodium dichromate in sulfuric acid, followed by decarboxylation of the resulting 2,4,6-trinitrobenzoic acid in boiling water." 1,3,5-Trinitrobenzene is prepared from 2,4,6-trinitro-m-xylene by a similar route." 2,4,6-Trinitroanisole can be prepared from the... 

Petroleum refineries produce a stream of valuable aromatic compounds called the BTX, or benzene-toluene-xylenes (Ruthven 1984). The Cg compounds can be easily separated from the Ce and C compounds by distillation, and consist of ethyl benzene, o-xylene, m-xylene, and / -xylene. Ethyl benzene is the starting material for styrene, which is used to make polystyrene / -xylene is oxidized to make terephthalic acid, and then condensed with ethylene glycol to make polyester for fibers and films. The buyers of / -xylene are the manufacturers of terephthalic acid, such as BP-Amoco, who in turn sell to the fiber manufacturers such as DuPont and Dow. These are big and sophisticated companies that have strong research and engineering capabilities, and are used to have multiple suppliers. The eventual consumers of adsorbents are the public who consider polyester as one of the choices in fabric and garments, in competition with other synthetic and natural fibers. Their purchases are also dependent on personal income and prosperity. In times of recession, it is always possible for a consumer to downgrade to cheaper fibers and to wear old clothes for a longer period of time before new purchases. 

For the rate of initiation, a half-order was usually obtained, and a first order with respect to the reagent as with tetrahydrofuran (THF) (13). For a few reagents, these relations do not apply—e.g.9 for m-xylene the rate of oxidation is between half and first order with respect to V and less than first order with respect to xylene (11). (In every case Vo2 represents the rate of consumption of 02 corrected for N2 evolution, and efficiency of initiation is assumed to be 0.7). 

The same relation applies to Tetralin, cumene, alcohols, and all compounds oxidizing with a considerable chain length. For m-xylene the chain is short (A — 2). In this case, the simplifying hypotheses for long chains which neglect the initiator radicals (I ) and their peroxy (I02 ) forms are no longer valid (11). In particular the rate of oxygen con-... 

A similar effect was noted in separate investigations by another group [108], Oil-in-water HIPEs, where the oil phase contained aromatic or halogenated liquids, were difficult or impossible to form, with nonionic surfactants. This was postulated to be as a result of interactions between the polar ethylene oxide groups of the surfactant and the aromatic or halogenated solvents, which are more polar than hydrocarbons. Water-in-oil systems also displayed this tendency [21] however, w/o HIPEs with m-xylene as the oil phase [13] could be produced with monolaurin as nonionic emulsifier, due to stronger intermolecu-lar interactions at the interface. 

The presence of gas-phase water is generally beneficial to the photocatalytic oxidation of aromatic contaminants. In continuous photoreactors, humidity appears to prolong catalyst activity and delay or prevent catalyst deactivation. The effects of humidity on reaction rates, however, appear to vary, depending on the aromatic contaminant concentration and the humidity level. For example. Petal and Ollis [18] examined the continuous photocatalytic oxidation of m-xylene in a powder-layer photoreactor at several different relative humidity levels. The m-xylene photo-oxidation reaction rate was observed to increase for gas-phase water concentrations up to 1000 mg/m (—7% relative humidity). Increasing the humidity level further (up to 5500 mg/m ) produced a gradual decrease in the observed reaction rate, possibly due to increased adsorption-site competition between xylene and water. The reported xylene removal rate for a water concentration of 5500 mg/m was approximately half that seen at 1000 mg/m. ... 

---