Meta-Ethyltoluene

Fraenkel et al. postulated that H-ZSM-5 crystals contain two types of Brdnsted acid sites [43]. The internal sites are accessible for molecules which can cross the 10-MR barriers and have kinetic diameters lower than 0.58 run. A second type of sites is accessible for molecules with kinetic diameters up to 0.62 nm, and was assigned to half chatmel intersections located on (001) crystal planes. These special pore mouths were thought to be responsible e.g. for the discrimination between ortho- and meta-ethyltoluene isomers and cymene. The key observation at the basis of this hypothesis was that in the alkylation of naphthalene with methanol the "slim" isomers 2-methyl- and 2,6- and 2,7-dimethylnaphthalene were dominating [44,45] over HZSM-5 and HZSM-11 as catalysts, in contrast to what was observed on zeolites with larger pores as H-Mordenite. lire authors suggest that this shape selectivity occurs at the special sites at the external surface of the ZSM-5 or 2 M-11 crystals and advanced the concept of shape selectivity at the external surface. Derouane et al. [46,47] generalized this concept and coined to it the term "nest effect" [46]. 

Vinyltoluene (VT) is a mixture of meta- and i ra-vinyltoluenes, typically in the ratio of 60 40. This isomer ratio results from the ratio of the corresponding ethyltoluenes in thermodynamic equiHbrium. Physical properties and chemical analysis of a typical vinyltoluene product are shown in Tables 7 and 8, respectively. Vinyltoluene monomer is produced by Dow Chemical Company and Fina Oil Chemical Company. The worldwide consumption is estimated to be approximately 100,000 t/yr. 

Ethyltoluene is manufactured by aluminum chloride-cataly2ed alkylation similar to that used for ethylbenzene production. All three isomers are formed. A typical analysis of the reactor effluent is shown in Table 9. After the unconverted toluene and light by-products are removed, the mixture of ethyltoluene isomers and polyethyltoluenes is fractionated to recover the meta and para isomers (bp 161.3 and 162.0°C, respectively) as the overhead product, which typically contains 0.2% or less ortho isomer (bp 165.1°C). This isomer separation is difficult but essential because (9-ethyltoluene undergoes ring closure to form indan and indene in the subsequent dehydrogenation process. These compounds are even more difficult to remove from vinyltoluene, and their presence in the monomer results in inferior polymers. The o-ethyltoluene and polyethyltoluenes are recovered and recycled to the reactor for isomerization and transalkylation to produce more ethyltoluenes. Fina uses a zeoHte-catalyzed vapor-phase alkylation process to produce ethyltoluenes. 

Structural Isomers. Chromatograms illustrating the separation of ortho, meta and para isomers of cresol (22) and and xylene ( O)on RP columns are shown in Figures 4 and 5. They enable a comparison of the chromatographic properties and selectivities due to <. - and -CD complexation between positional isomers of the above compounds.Similar behaviour was observed for ortho,meta and para isomers of fluoronitrobenzene, chloronitrobenzene, iodoni-trobenzene, nitrophenol, nitroaniline, dinitrobenzene (22), nitrocinnamic acid (22) some mandelic acid derivatives (19,21,34) and ethyltoluene (28). Both [Pg.225]

The sequence of elution of positional isomers of halogen derivatives of nitrobenzene (23), xylene and ethyltoluene (20) from RP column modified with a f>-CD solution is identical 1) ortho, 2) para and 3) meta. 

Ethyltoluenes or Ethylmethylbenzenes, C2H5.CeH4.CH3 mw 120.19. Three isomers are known ortho-, meta- and para-. Their, prepns and properties are given in Refs Refs 1) Beil 5, 396, (192) [308] (ortho)... 

The present study explores acidity and poisoning on the external surface of a zeolite, using ZSM-5 and a facile probe reaction, the alkylation of toluene with ethylene to yield ortho-, meta- and para-ethyltoluenes (OET, MET and PET, respectively) (ref. 3). As with the xylenes, strong para-selectivity is to be expected in the toluene-ethylene reactions which occur within the ZSM-5 poiespace. 

The distribution among aromatic products was also altered by the presence of molybdenum (Fig. 1). The relative yields of para and meta isomers of xylenes and ethyltoluenes were increased over Mo exchanged ZSM-5 and over the physical mixture of MoO and H-ZSM-5 (no aromatics were detected over the impregnated catalyst), but this effect was not found for the partially poisoned catalyst. 

TSCA 40CFR716.120.cll ethyltoluenes-ethyltoluene (mixed isomers) and the ortho (1,2-), meta (1,3-), and para (1,4-) isomers T120-C11... 

More recently, methods have been developed for reducing the effective pore and channel dimensions. These techniques employ both physical treatments and chemical reagents. They have provided the basis for para-selective alkylation catalysts (18). These modified zeolites permit discrimination between molecules of slightly different dimensions. As a result, the para-isomers of the xylene or ethyltoluene products with the smallest minimum dimensions (Table 4) are able to diffuse out of the catalyst pores at rates about three orders of magnitude greater than those for the corresponding ortho- and meta-isomers (20). This discrimination capability is schematically represented in Figure 1, where the effective size of a para-selective catalyst pore is shown by the dashed line. 

The reaction data are summarized in Table 4.4. With unmodified H — ZSM-5 zeolite catalyst, near equilibrium ratio of the meta and para isomers was observed. However, lower than equUibrium amounts of o-ethyltoluene were produced. A dramatic increase in selectivity compared with unmodified catalysts was obtained for the para isomer (up to 98%). A corresponding decrease in meta isomer and virtual elimination of 0-ethyltoluene was also observed. Thus, a completely different isomeric mixture ofethyltoluenes was obtained with modified ZSM-5 zeolites compared with HCl/AlCb catalyst presently used for commercial vinyltoluene production. 

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