Synthesis Of Phthalic Anhydride Research Articles

The Synthesis of Phthalic Anhydride via Ozonation of Naphthalene

The oxidation of naphthalene (1) (Scheme 1) in dichloromethane or acetonitrile with excess ozone gives phthalic aldehyde (3), 2-formyl benzoic acid (4) and phthalic anhydride (8). Small amounts of the (E)- and (Z)-isomer of 3-phenyl-(2-formyl)-propenal (10) and (11) are also observed in some cases. The reaction is faster in acetonitrile than in dichloromethane owing to the higher solubility of ozone in the former solvent. The reaction is faster on lowering the temperature because of the increase of the concentration of ozone in solution at lower temperature. With a 1:1 or a 1:2 naphthalene:ozone ratio high conversion and low selectivity for the anhydride (8) is observed.

ChemInform Abstract: Synthesis of Phthalic Anhydride: Catalysts, Kinetics, and Reaction Modeling

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Synthesis of Phthalic Anhydride: Catalysts, Kinetics, and Reaction Modeling

Information concerning the oxidation of o-xylene and naphthalene, the two main processes for producing phthalic anhydride, is updated and analyzed. New techniques for the preparation of catalysts, all based in the impregnation method and involving the control of parameters such as pH and ionic strength of solutions, are described; the performance of the resulting catalysts is compared with that of catalysts prepared by other methods. Sulfur-containing substances and promoters such as Ag, P, Nb, and Sb have been shown to enhance catalyst performance; studies of their effect on the surface area, acidic properties, and stabilization of the oxidation state of vanadium in supported V2O5 catalysts are described. The latest attempts to correlate the physicochemical characteristics of the catalysts with their catalytic features are analyzed. FTIR, Raman spectroscopy, adsorption of bases, 51V-NMR, XRD, XPS, SIMS, and electrical conductivity have been used in the study of V2O5/TiO2 catalysts, allowing further understanding of the effects of the properties such as acidity and the state of oxidation of the surface. Particular emphasis has been given to the presence of VIV, which is thought to cause lower selectivity to phthalic anhydride. For o-xylene oxidation, the formation of involatile by-products has been established as a secondary reaction, accounting for the poor carbon balances obtained under some experimental conditions. Involatile by-products, whose formation has been associated with the presence of strong acid sites, can adsorb on the catalyst surface, leading to deactivation, or undergo total combustion, acting as a source of CO2. Attempts to quantify and characterize those by-products are described. The modeling of the reaction using both fixed- and fluidized-bed reactors, including the study of parameters such as the inlet temperature and the bath temperature, is analyzed. Models considering catalyst deactivation have been also developed; for o-xylene oxidation, deactivation has been associated with processes both reversible, such as changes in the oxidation state of vanadium, deposition of involatile compounds, and irreversible, such as structural changes, decrease in surface area, sintering, and variation of the promoter concentration at the catalyst surface. The study of V2O5/TiO2 EUROCAT catalysts, involving a number of European laboratories, is reviewed, and their performance is compared with that of other V2O5/TiO2 catalysts.

On the polyfunctional nature of (VO)2P2O7

The catalytic behavior of vanadyl pyrophosphate in the conversion of decalin, tetrahydro phthalic anhydride, naphthalene, 3-methyl tetrahydrophthalic anhydride, and benzene is reported in order to evidence some basic key catalytic properties of this catalyst and to discuss the possible surface pathways in the synthesis of phthalic anhydride from n-pentane, a characteristic specific catalytic property of this system.

Catalysts, Kinetics and Reactor Design in Phthalic Anhydride Synthesis

Abstract Phthalic anhydride is a chemical of considerable importance and is generally produced by the vapor-phase oxidation of o-xylene or naphthalene over vanadium pentoxide catalysts according to

Maximum allowable temperatures in chemical reactors

The calculation of the required cooling capacity in tank reactors—in order to obtain a high conversion to desired product and to prevent excessive degradation of the reagent to unwanted products— is discussed. Temperature limits, as normally specified in practice, are shown to depend on the residence time in the reactor. The synthesis of phthalic anhydride in a well mixed fluid bed reactor is treated as an example of a process in which a high conversion and a safe limitation of the reactor temperature are difficult to achieve simultaneously.

Reactions of Carbon Monoxide at High Temperature. I. A New Synthesis of Phthalic Anhydrides

Reactions of Carbon Monoxide at High Temperature. I. A New Synthesis of Phthalic Anhydrides