Phthalic production figures

The development of a normal-phase HPLC method was warranted due to the presence of phthalic anhydride, which is unstable in water. Analysis in organo-aqueous solvent systems that are used in RPLC would lead to an on-column reaction forming the respective carboxylic acid degradation product. Figure 5-5 shows the chromatogram obtained for the separation of 9,10-anthraquinone from the reactants and impurities on a silica column. The method was successfully applied to monitor the reaction conversion and also to determine the stability of 9,10-anthraquinone at the specified storage conditions. 

In 1968 U.S. production of p- and o-xylene was estimated at 1.3 billion and 0.97 billion pounds per year respectively. Production figures for m-xylene have never been published by the Tariff Commission. Its use has, however, remained quite small in relation to p- and o-xylene. It is expected that domestic demand for both p- and o-xylene will continue to increase. Terephthalic acid is the key component required for production of polyester film and fibers and is presently produced only from p-xylene. Phthalic anhydride is produced from both naphthalene and o-xylene. Although o-xylene is not expected to replace naphthalene entirely, its use for phthalic anhydride manufacture is expected to increase. 

No studies regarding di- -butyl phthalate metabolism in humans were located. Studies in animals indicate that metabolism of di- -butyl phthalate proceeds mainly by hydrolysis of one butyl ester bond to yield mono- -butyl phthalate. The product that appears in the urine is mainly mono- -butyl phthalate conjugated with glucuronic acid, with lower levels of unconjugated mono- -butyl phthalate, various oxidation products of mono- -butyl phthalate (see Figure 3-2), and a small amount of the free phthalic acid (Figure 3-2) (Albro and Moore 1974 Foster et al. 1982 Kawano 1980b Tanaka et al. 1978 Williams and Blanchfield 1975). 

Anthraquinone (A/Q). This product is mainly used for dyes, the classical route being the oxidation of anthracene (Figure 2.11) or the Friedel-Crafts route from phthalic anhydride (Figure 2.12). Alternative routes from benzene and ethylene and from naphthalene and butadiene have been studied on economic grounds. 

This will lead initially to branched chain structures such as indicated schematically in Figure 2.10, G indicating a glycerol residue and P a phthalic acid residue. In due course these branched molecules will join up, leading to a cross-linked three-dimensional product. 

The flexibility of some plastics can be improved by the addition of small molecules called plasticizers. For example, pure PVC turns brittle and cracks too easily to make useful flexible plastic products. With an added plasticizer, however, PVC can be used to make seat covers for automobiles, raincoats, garden hoses, and other flexible plastic objects. Plasticizers must be liquids that mix readily with the pol Tner. In addition, they must have low volatility so that they do not escape rapidly from the plastic. Dioctylphthalate is a liquid plasticizer that is formed by condensing two alcohol molecules with one molecule of phthalic acid, as illustrated in Figure 13-10. 

Figure 5.76. The fixed-bed reactor and the reaction scheme. Symbols A = o-xylene, B phthalic anhydride, C = waste gaseous products (CO2 and CO).

Indicator dyes for pH having the phthalide structure fall into two types, the phthaleins, shown in the lactone form of general structure (1.66) and the sulfoph-thaleins (1.67). The synthetic pathways to these products are very similar. The phthaleins (1.66) are made by reacting phenol with phthalic anhydride in the presence of Lewis acid catalyst, e.g. ZnCl, whilst (1.67) are obtained by using 2-sul-fobenzoic anhydride (Figure 1.20). 

There were 820 million pounds of phthalic anhydride produced in the United States in 1995. One of the end uses of phthalic anhydride is in the fiberglass of sailboat hulls. Phthalic anhydride can be produced by the partial oxidation of naphthalene in either a fixed or a fluidized catalytic bed. A flowsheet for die commercial process is shown in Figure P3-11. Here the reaction is carried out in a flxed-bed reactor with a vanadium pentoxide catalyst packed in 25 -mm-diameter tubes. A production rate of 31,000 tons pet year would require 15,000 tubes. 

Similarly, if the racemic mixture is composed of basic drugs, use is made of camphor-10-sulfonic acid, a natural product obtainable as an optically pure enantiomer. An example of the type of reactions involved is shown in Figure 4.13, where a pair of enantiomeric alcohols is resolved by reaction with phthalic anhydride and an optically pure base to form a pair of diastereoisomeric salts. Reactions of this type can be tedious to perform and, with the advent of HPLC with chiral stationary phases, are gradually being replaced. 

Herten and Froment (1968) studied the reaction on a doped vanadium pentoxide catalyst in a quasi-isothermal laboratory fixed bed reactor. Kinetic measurements were made in the temperature range 325-402 C for a wide range of feed compositions and varying residence times. The reaction scheme proposed is the same as that shown in Figure 3.13 with the exception that no maleic anhydride was isolated in the reaction products. They found no evidence of significant oxidation of phthalic anhydride to carbon oxides. The conversion of o-tolualdehyde to phthaiide is considered to be a relatively unimportant step in their model. 

All rates are defined as rates of consumption except for the main product phthalic anhydride where the reaction rates are defined as rates of production, r/s are reaction rates at the surface of the catalyst pellet while rjjs are reaction rates at bulk conditions. Component effectiveness factors for o-Xylene, otolualdehyde and phthalic anhydride are shown in Figure 5.18. 

Figure 5.41 shows the conversion of o-Xylene and yield of the desired product (phthalic anhydride). They show S-shape hysteresis and both conversion and yield are increasing with bulk temperature. The conversion is defined as ... 

The effectiveness factors for the o-Xylene consumption and phthalic anhydride production are shown in Figures 6.38 and 6.39 which show values very close to unity. The values of the effectiveness factor increase slowly along the length of the reactor which indicate that a small difference between the catalyst pellet surface and the bulk conditions do exist. From the figures, effectiveness factor increases as the oXylene feed mole fraction increases which was also noted in the single pellet parametric investigation in chapter 5. 

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