Orthoxylene

Paraxylene is recovered from Cg aromatics by crystallization. Fortunately, the solidification point of the para isomer is unusually high, -1-55.9°F, considerably above the meta and orthoxylenes which freeze at -54.2 and -13.3°F, respectively. The separation of para from meta by distillation is impractical because the spread in their normal boiling points is only 1.4°F. 

Orthoxylene (the highest boiling xylene isomer) is separated from the other xylenes and the heavier C, aromatics by fractionation. The meta and lighter xylenes are taken overhead in a xylenes splitter containing 160 trays. Orthoxylene is then separated from the C, aromatics in a 50-plate rerun column. Product purity from such a fractionation is typically 99-1- %. 

High purity orthoxylene is used almost solely in the manufacture of phthalic anhydride. The anhydride is an intermediate for the manufacture of plasticizers, alkyd resins, polyester resins and other derivatives, such as phenolphthalein. 

Ortho-verbindung,/. ortho compound, -xylol, n. orthoxylene, o-xylene. -zimtsdure, /. orthocinnamic acid. 

Ultrasonic irradiation of a mixture of zinc and a,a -dibromo-orthoxylene in dioxane results in dehalogenation and the generation of a xylylene intermediate (9) which readily adds to any dienophiles present in the reaction mixture e. g. with maleic anhydride or methyl propenoate to afford high yields of (10) and (11) respectively [95]. In the absence of dienophile the product is mainly polymer with a trace of (12) (Scheme 3.16). The work was performed in a cleaning bath at 25 °C on 10 mmol scale using 23 mmol zinc under N2. There was no reaction in the absence of ultrasound. 

In the primary application of phthalic acid, life is rather transitory. Almost all phthalic acid is used to make phthalic anhydride. When orthoxylene is used as the starting base chemical, phthalic acid is formed but immediately dehydrates (loses a molecule of water) to form phthalic anhydride, as shown in Figure 18-3. 

Alkyl aryl orthoxylene sulfonates were also investigated. 

The first being a linear nonyl orthoxylene sulfonate and the second being a branched dodecyl one. Both were supplied by the Exxon Corporation and contain known amounts of unsulfonated hydrocarbons (14% and 25.2% respectively). ... 

The nomenclature adopted by the lUPAC (International Union of Pure and Applied Chemistry) for some additional aromatic systems is shown in Figure 6-11. The symbolism for xylene indicates that two methyl groups are present. The methyl groups may be at the one and two positions (orthoxylene), the one and three positions (meta-xylene), or the one and four positions (para-xylene). Alternate names are o-xylene, m-xylene, and p-xylene. In the other cases, one group is attached at the number one position. All numbering begins at this position. 

The increase in dipole moments is observed in a sequence of aromatic compounds paraxylene, metaxylene, orthoxylene, bromobenzene. However the correlation between the magnitudes of dipole moments of solvents and the magnitudes of C6o solubility in these solvents is not observed (Table 1). 

Based on the results obtained by the NQR method it has been found that donor activity of an aromatic molecule depends upon the number of methyl substituents added to benzene. A series of increasing donor force have been obtained in [28] Benzene < Orthoxylene Paraxylene < 1,3,5-Trimethylbenzene <... 

Figures 4 a, b,c illustrate the position effect of three CH3-groups on C6o solubility. C6o solubility increases compared to that in orthoxylene (Fig. 4 a) if the third -CH3 group is located in the para-position (Fig. 4 a, c) and decreases if this group is located in the /weta-position (Fig. 4 a, b). If both of these methyl groups are in the weta-positions, their presence does not change dissolving ability of benzene. C6o solubility in 1,3,5-trimethylbenzene is identical to that in benzene (Fig. 5 a, c).

These isomers can be distinguished on the basis of their l3C-NMR spectra because they have different symmetries. The ortho-isomer has four different carbons, the meta-isomer has five, and the para-isomer has only three. The unknown must be orthoxylene. Note that this compound could be identified as one of the xylene isomers on the basis of its H-NMR spectrum, but it would be difficull to establish which isomer it is from just that information. 

Analogous results were observed for HYDW coked by orthoxylene. 

High-purity benzene and xylenes are products of aromatics complexes having several interconnected processes and unit operations (22). In 1998, the market demand for benzene, on a world-wide basis, was 27.4 million metric tons per year, mostly for styrene. By comparison, the demand for para-xylene was 16.1 million metric tons. Ortho-xylene demand was lower, at 3 million metric tons. The market for meta-xylene was even lower, at about 300,000 metric tons. Because of these relative market requirements, most aromatics complexes are designed for benzene and para-xylene. Depending on local situations, they may also produce orthoxylene, which can be separated by fractionation, and/or meta-xylene. Process units that can be integrated into UOP aromatics complexes are described in Figure 4.17. 

Crystallization and adsorption are both widely used to perform the separation distillation is not used (except for orthoxylene separation) because of too small differences between the boiling points (Table 10.1). Despite the still high importance of crystallization, adsorption becomes the most widely used technique because of its high efficiency. The adsorbents which are used for selective adsorption of paraxylene are X or Y zeolites exchanged with adequate cations. Liquid phase Simulated Counter Current adsorption, which is the most efficient process, is generally used (1). In addition to the complexity of this process, the choice of an adsorbent selective for paraxylene is the critical point. 

Application To produce high yields of benzene, toluene, xylenes and hydrogen from naphthas via the CCR Aromizing process coupled with RegenC continuous catalyst regeneration technology. Benzene and toluene cuts are fed directly to an aromatics extraction unit. The xylenes fraction, obtained by fractionation and subsequent treatment by the Arofining process for diolefins and olefins removal, is ideal for para-xylene and orthoxylene production. 

It remained for Massimilla (1973) to provide laboratory research demonstrating the higher contacting efficiency that a turbulent fluid bed affords. Wainwright and Hoffman (1974) reported excellent contacting for oxidation of orthoxylene in what was probably a fast fluid bed. 

Figure 10) - 129-Xe NMR chemical shift as a function of sorbed Xe of dealuminated HY zeolites. coked during orthoxylene cracking then partiallly and totally reoxidized. fresh sample 8.7 % coke pyrolyzed O oxidized, 4.8% coke oxidized, 1.6% coke A oxidized, 0% coke .(from reference 14).

Thermal decomposition of 1-butene provides a more complex product spectrum than is obtained from either cis- or trans-2-butenes. Between 550° and 760°C in a flow system with nitrogen dilution (3), methane, propylene, butadiene, and ethylene were major products as well as hydrogen, ethane, 1-pentene, 2-pentene, 3-methyl-1-butene, and 1,5-hexa-diene. In studies in a static system (4), cyclohexadienes, benzene, cyclopentene, cyclopentadiene, toluene, orthoxylene, and cyclohexene were observed among the liquid products of the reaction over the temperature range 490°-560°C. 

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