Phthalic anhydride recovery

Phthalic Anhydride Recovery and Purification. The accepted method of recovering phthalic anhydride from vapor-phase oxidation... 

Until 1959, all the phthalic anhydride was made from coal tar naphthalene, the double-benzene ring compound also shown in Figure 18—3 was easily oxidized directly to phthalic acid. But with phthalic anhydride being only a small share of coal oil, and with the demand for phthalic anhydride escalating rapidly, coal tar became an inadequate source. The frantic search for an alternative route led to the development of the recovery process for ortho-xylene from refinery aromatics streams discussed in Chapter 3 and the... 

We have already seen various syntheses of SMA phthalimides, either through nucleophilic animation of a-chlorosilanes (see Sections III.A.l and III.A.2), hydro-silylation of A-vinyl phthalimide (see Section III.B.5.f) or by reaction of SMA with phthalic anhydride (see Section IV.A.2.h). The deprotection and recovery of free SMA has been conducted in the usual way by reaction with hydrazine.81,88,211... 

Desublimation Vapour Solid ESA Recovery of phthalic anhydride from non-condensible gas... 

Sublimation is the transfer of a substance from the solid to the gaseous state without formation of an intermediate liquid phase, usually at a relatively high vacuum. The reverse process, desublimation, is also practised, for example, in the recovery of phthalic anhydride from gaseous reactor effluent. 

Lonza S.p.A. Maleic anhydride Phthalic anhydride offgas Maleic anhydride recovery, dehydration and azetropic distillation 2 1987... 

Lurgi 01 Gas Chemie GmbH Phthalic anhydride O-xylene, naphthalene Multi-tubular reactor oxidizes o-xylene at high yield with maximum heat recovery for export HP steam 110 1998... 

The production of chilled water in the fine chemical manufacture and food processing industries may also give rise to freezing fouling where ice is formed on the cold surface. The problem may also exist in vapour systems during the recovery of solid products, e.g. the production of phthalic anhydride crystals in so-called "switch condensers". 

Recovery of phthalic anhydride from gas containing N, O, CO, CO, HjO, and other organic compounds by condensation to the solid state (Vol. 15, p. 451)... 

Sublimation is the transfer of a substance from the solid to the gaseous state without formation of an intermediate liquid phase, usually at a relatively high vacuum. Major applications have been in the removal of a volatile component from an essentially nonvolatile one separation of sulfur from impurities, purification of benzoic acid, and freeze drying of foods, for example. The reverse process, desublimation (16), is also practiced, for example in the recovery of phthalic anhydride from reactor effluent. The most common application of sublimation in everyday life is the use of dry ice as a refrigerant for storing ice cream, vegetables and other perishables. The sublimed gas, unlike water, does not puddle and spoil the frozen materials. 

For the recovery of phthalic anhydride from the hot dilute mixture of gases and vapors issuing from the catalytic converter, the normal technique is to effect condensation of the phthalic anhydride in large, roomlike cooling chambers (indicated in Fig. 9-11) where the product deposits in the form of a bulky mass of long needlelike crystals. 

To reduce the space required for this recovery, to improve the density and control the purity, and to reduce the amount of manual labor required, it has been proposed to accomplish recovery by use of a sequence of steps (1) cool the vaporous mixture by passage through a water-cooled tubular cooler condenser, (2) remove the bulk of the condensed material by means of a scraper-screw conveyer in the cold end of this cooler, and (3) recover dust from the cold gases by means of a bag filter. Fractional condensation of phthalic anhydride from gas-vapor mixtures containing maleic anhydride may be accomplished by maintaining the mixture in the temperature range of 80-90 C to 132 C by indirect heat exchange with a fluid confined in tubular conduits. ... 

Valuable chemicals are recovered from the gas in the coke plant. Bensene is used in the production of nylon, toluene euid xylene are used as solvents and in the making of various chemicals. Phenols recovered from tar amd the gas find uses in meJcing thermosetting phenolic plastics. Ammonia is used as fertiliser in aigriculture. Coumarone-indene recovered from the high boiling solvent is used in the resin industry. Naphthalene recovered from tar is used to make phthalic anhydride. There are literally hundreds of compounds in the tar and the chemicals recovered from the coke oven gas. Several of these are in sufficiently laurge concentrations to make recovery in pure form economically feasible. 

At these equilibrium conditions of 70°C and 1,034 torr, the partial pressure of phthalic anhydride in the vapor is (0.005/99.005)1,034 = 0.05 torr, which is equal to its vapor pressure. The partial pressure of water in the vapor is (4.25/99.005)1,034 = 44.4 torr, which is well below its vapor pressure of 234 torr at 70°C. Thus, water does not condense at these conditions. The amount of solids in the table above corresponds to a 99.5% desublimation of phthalic anhydride. At 85°C the percent desublimation is only 98%, while at 96.4 C it is only 95%. Thus, the recovery of phthalic anhydride from the reactor effluent is sensitive to the desublimation condenser temperature. 

In recent years the nonsteady state mode has been used to an increasing extent because it permits accessing intermediate steps of the overall reaction. Very complete reviews of this topic are presented by Mills and Lerou [1993] and by Keil [2001]. Specific reactors have been developed for transient studies of catalytic reaction schemes and kinetics. One example is the TAP-reactor ( Transient Analysis of Products ) that is linked to a quadrupole mass spectrometer for on line analysis of the response to an inlet pulse of the reactants. The TAP reactor was introduced by Cleaves et al. in 1968 and commercialized in the early nineties. An example of appUcation to the oxidation of o.xylene into phthalic anhydride was published by Creten et al. [1997], to the oxidation of methanol into formaldehyde by Lafyatis et al. [1994], to the oxidation of propylene into acroleine by Creten et al. [1995] and to the catalytic cracking of methylcyclohexane by Fierro et al. [2001], Stopped flow experimentation is another efficient technique for the study of very fast reactions completed in the microsecond range, encountered in protein chemistry, e.g., in relaxation techniques an equilibrium state is perturbed and its recovery is followed on line. Sophisticated commercial equipment has been developed for these techniques. 

Ozonation of benzo[r,s,t]pentaphene (7) followed by oxidative workup led to benzo[r,s,t]pentaphene-5,8-dione (12) (14%), phthalic acid (13) (4%), p-terphenyl-2,2, 3, 2"-tetra-carboxylic acid-2, 3 -anhydride (14) (10%), and 2-(o-car-boxyphenyl)- ,10-phenanthrenedicarboxylic acid anhydride (15) (3%), with a 56% recovery of unreacted 7, Ozonation of pentaphene (11) led to a peroxidic mixture which on oxidative workup led to 2,2 -binaphthyl-3,3 -dicarboxalde-hyde (16) (16%), 2,2 -binaphthyl-3,3 -dicarboxylic acid (17) (16%), and 13 (2%), with a 28% recovery of unreacted 11. A comparison of the reactivity to ozone of carcinogenic polycyclic aromatics benzo c]phenanthrene (1), 7,12-di-methylbenz [a] anthracene (2), 3-methylcholanthrene (3), dibenz[si,]] - (4), and dibenzlsi, ]anthracene (5), benzo Si -pyrene (6) and 7, and the noncarcinogen 11, all determined in our laboratory, leads us to conclude that there is no simple, consistent correlation between carcinogenicity, K-and L-region additivity towards ozone and the Pullmans electronic theory of carcinogenesis. 

Ozonation of 7 in methylene chloride at —78°C. with 3.5 mole equivalents of ozone (requiring passage of 5-6 mole equivalents), followed by oxidative workup (1 1 10% sodium hydroxide 30% hydrogen peroxide) led to benzo[r,5,f]pentaphene-5,8-dione (12) (14% ), phthalic acid (13) (4%), p-terphenyl-2,2, 3, 2"-tetracarboxylic acid-2, 3 -anhy-dride (14) (10%), and 2-(o-carboxyphenyl)-l,10-phenanthrenedicar-boxylic acid anhydride (15) (3%), with a 56% recovery of unreacted 7, as shown below. 

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