Phthalic anhydride is an organic compound that has a pungent odor. The compound is white and dissolves in water, alcohol, and other organic solvents. PA is used in the manufacture of dyes, phthaleins, resins, insecticides, and emollients. In addition, PA is used in the manufacture of plastic softeners.

As the name implies, PA is a phthalic acid anhydride. PA is produced by an oxidation reaction with naphthalene or O-Xylene catalyst. This is known as an intermediate element in chemical reactions; Because it is both oxidized and always available. In the continuation of this article, join us to introduce you to phthalic anhydride.

What is the chemical structure of phthalic anhydride or PA?

Phthalic Anhydride Structure

Phthalic Anhydride Structure

It is a white substance with a crystalline appearance. It also has interesting chemical properties and has a variety of applications in the industry. The chemical properties of this substance, which has the molecular formula of C8H4O3, are:

  • Molecular weight: 148 g/mol
  • Boiling point: 284.5 ° C
  • Melting point: 131.1 ° C
  • Soluble in alcohol, water, ether, benzene, and other organic solvents
  • Flashpoint: 584
  • Solid density: 1.527 g / cm3

PA is a cyclic substance used to make emollients. In addition, PA is also used to make PVC. In the process of making PVC softeners, PA is used as a catalyst. In addition, DOP and di-butyl phthalate are important emollients in which PA is the catalyst.

In addition to these applications, phthalic anhydride can also be used in the paint industry. In this way, this material is combined with polyols and polyacrylate resins are made by condensation method. In this process, if an unsaturated acid is condensed with ethylene glycol, two products are made. Unsaturated polyester resin and glass fiber reinforced plastic. It is interesting to know that phthalic anhydride is also a raw material for the synthesis of important drugs.

Various uses of phthalic anhydride in global industries

PA Uses

PA Uses

One of the most important applications of PA is its use as a monomer and intermediate chemical in polymer reactions. Phthalic anhydride is also used in the production of unsaturated polyester resins. This strengthens the plastics produced. These reinforced plastics are used in various industries. For example the construction industry and the manufacture of bathroom fixtures, the manufacture of auto parts and boats.

Application of phthalic anhydride in the production of alkyd resins

It is used to make paints, nail polishes, and other cosmetic products. Phthalic anhydride is the raw material for the production of PVC and other general softeners. In addition, PA is used to make saccharin.

Another application of this white material is in making beautiful colors and repelling insects and thermal insulation.

Advantages of using phthalic anhydride

This substance is one of the most widely used substances in the world. There are many different applications for PA. These applications are due to the special properties and benefits of this material. Some of the benefits of using phthalic anhydride:


Because phthalic anhydride has a high concentration of O-Xylene, it will have a very low cost for various processes. PA with a high concentration of this gas, makes you have good efficiency in your reactions.

Elimination of unauthorized products in the production cycle

With this material, you can remove unnecessary reactants from the production reactions. Phthalic anhydride removes by-products from the combustion cycle. This reduces the environmental pollution of the reactions.

High efficiency of phthalic anhydride

This feature is one of the top benefits of PA. This white substance can be up to 115% more effective than its weight percentage in reactions! This rate of return is truly amazing! You can use this advantage of phthalic anhydride and make very targeted reactions.

Thermal recovery and insulation

The clever design of phthalic anhydride makes this material have good heat recovery. In addition, you can use PA to obtain medium and low vapor pressures in reactions. So do not worry! Your chemical reactions will be very easy with PA.

Proper flexibility

The use of PA in various reactions increases the efficiency of devices and reactants. This results in less energy loss in the reactions.

Environmental care

PA causes little contamination. This causes the reactants to burn completely in the reaction so that no additional contaminants remain.

No oscillation in phthalic anhydride vapors

The design of reactions using phthalic anhydride as a catalyst is very clever. In these projects, using small equipment and low energy resources, they do the planning. Once the calculations are complete, the reactors and energy can be increased without oscillation in the system and good efficiency can be achieved.

High efficiency of this material

With PA, the efficiency of switch capacitors in reactions increases to 99.8%. This high efficiency indicates the very high purity of phthalic anhydride and its excellent catalyst.

How is phthalic anhydride stored?

It should be noted that PA should be stored in a completely dry environment. PA containers should be completely closed so that no moisture enters the container. In addition, phthalic anhydride should be kept away from water, oxidants, acids, amines, bases, and alcohols!

You must pay attention to the standards of handling and storage of this material. Keep in mind that breathing phthalic anhydride will cause respiratory problems such as asthma! So unlike HIPS and GPPS, this substance is not harmless. In addition, PA is very irritating in contact with the skin. This irritation causes skin eczema and may have irreversible effects on the cornea.

This substance is useful, very dangerous! Animal studies show that PA vapors cause severe damage to lung cells. However, detailed studies on the effect of phthalic anhydride on cell carcinogenesis have not been performed.

However, you must be very careful in storing and handling PA. This substance, despite having excellent benefits, is very toxic and dangerous. It should be noted that children should not come into contact with this substance in any way. Because the bad effects of this substance on children will be much more severe.

How is PA production done?



There are two main processes for the production of PA: O-Xylene oxidation and naphthalene oxidation. These production methods are constantly being updated to get the most out of these reactions. Various tests are performed on the catalysts of these reactions, examining various factors such as the ionic resistance of the reactant solutions and their pH.

Oxidation of O-Xylene produces by-products. These products reduce the reaction efficiency. These substances are non-volatile and inactivate the reaction. In addition, they can catch fire and be a source of heat energy. One of the experiments was performed to reduce the oxidation of this substance and increase its efficiency.

In other experiments, the available catalysts are compared. Sulfurous materials react and accelerate the catalysts. For example, SB, Ag, and NB can speed up reactions. In addition, various studies have been performed on the effect of different substances on the PA production reaction. These studies show that vanadium oxidation also accelerates catalysts.

Various studies have been performed on the effect of chemicals on the efficiency of PA production reactions. For example, the effect of spectroscopy, the adsorption of bases, the electrical conductivity of reactants and catalysts, the oxidation state, and the acidic properties of materials. Among these reactants, however, vanadium with a capacity of 5 produced less phthalic anhydride; So it has to be removed from the reactions.

As mentioned, there are two ways to produce phthalic anhydride. To build a PA, different modeling must be done. The purpose of these modelings is to increase the production process of phthalic anhydride and reduce the reaction return process.

We know that chemical reactions are often bilateral. This reduces the production efficiency of PA. Experts have found in various experiments that reducing the deposition level, increasing the concentration of catalysts, improving the energy source, and reducing unnecessary oxidations can improve the production process.

Uses of phthalic anhydride

In general, 3 important applications for PA have been recorded. These applications include:

Manufacture of unsaturated polyesters

These materials can harden against heat. That is, with increasing ambient temperature, the resistance of unsaturated polyesters increases. These versatile materials are used in the construction of boats and bathtubs. In addition, it is used in the manufacture of durable auto parts products.

Production of phthalic anhydride esters

PA esters are used to make PVC and other softeners. In everyday life, we see a variety of emollients, most of which are made from PA.

Production of glycerol alkyd resins

PA in resins

PA in resins

One of the most important uses of PA is to make resin paints. For example, the production of phthalates increases the production of dyes. These colors are more durable and can be easily combined. This material is also used to produce furniture and household items.

Its use has changed since the production of the first PA products. O-Xylene is one of the most important substances in the production of phthalic anhydride. This material, which is more efficient than naphthalene, also makes reaction possible in small reactors.

In addition, the risk of naphthalene explosion during the reactions led to the use of O-Xylene to produce PA. Despite its advantages, this material also has disadvantages. Contamination from the burning of this substance poses many dangers to human and animal health. Because PA is produced using O-Xylene, the use of O-Xylene has received a lot of attention around the world.

O-Xylene applications in the world



It is one of the best materials for the production of PA, which is obtained from crude oil. The uses of O-Xylene are very diverse and it is also used in dentistry and medicine. It is the best substance for coloring cell tissues in the laboratory, which is also used to produce PA.

One of the most important applications of O-Xylene is the production of lubricants. This material is used in engine oils and brake fluid. In addition, O-Xylene is used in the manufacture of leather and the printing industry. In addition, this material is also used for the production of PVC. O-Xylene in PVC production makes the flexibility of materials higher. This advantage of O-Xylene is used to produce strong resins and ships and boats.

Other uses of this material:

  • Making paint
  • Making wax
  • Made of antifreeze
  • Making adhesives
  • Making cleaners
  • Manufacture of disinfectants and insecticides

Summary of a review of phthalic anhydride

In this article, we have thoroughly investigated PA. This material has various applications in various industries. This substance is used as a reactant in the production reactions of PVC and other softeners. This substance increases the efficiency of reactions.

Phthalic anhydride has many benefits and has many uses. For example, PA is used in the manufacture of all kinds of paints, all kinds of furniture and kitchen utensils, durable boats, and adhesives.

As mentioned, there are two ways to produce phthalic anhydride. One is the oxidation of naphthalene and the other is the oxidation of O-Xylene. Currently, due to the greater dangers of naphthalene, O-Xylene is used to produce PA. O-Xylene has a variety of applications. This material is currently one of the most widely used materials in the manufacture of resin paints and various chemical reactions. O-Xylene is also used to increase PA production efficiency in small reactors.

Despite the advantages of phthalic anhydride, it also has disadvantages. Inhalation of this substance is very dangerous and may cause lung problems. In addition, contact with the skin can cause skin conditions such as eczema. Therefore, it is better to be very careful in storing and moving phthalic anhydride.

If you want to ask your questions about PA and buying it, contact us. Our experts will give you a free consultation and guide you in choosing the best PA.

What is phthalic anhydride or PA?

PA is a chemical used to produce a variety of plastics in various industries. This material is one of the most important materials used to produce plastics, resins, paints, and emulsions.

What are the most common names for phthalic anhydride?

This substance is known as 2-Benzofuran-1,3-dione. In addition, it is also known as Isobenzofuran-1,3-dione Phthalic anhydride. In various industries, this chemical is known as phthalic anhydride or PA.

What are the major applications of phthalic anhydride in global industries?

PA is one of the most important chemicals used in the production of various plastics in the world. In addition, this chemical is used to produce emulsions, paints, and plasticizers. In addition, PA is also used to produce a variety of durable resins.

Does phthalic anhydride oxidize in atmospheric air?

What are the ingredients of phthalic anhydride or PA?

PA is produced by the ortho-xylene oxidation reaction as well as the oxidation of naphthalene. These reactions must be performed in standard conditions and accordance with the rules. For example, to use ortho-xylene in water, different reactions must be used. In addition, phthalic acid is used to produce phthalic anhydride in global industries.

What is the structural and chemical formula of phthalic anhydride?

It is a type of acid made up of hydrogen, carbon, and oxygen atoms. It should be noted that the structural and chemical formula of phthalic anhydride is C8H4O3. It is an acid that contains COOH in its structure.

What is the shape and color of phthalic anhydride?

PA is an odorless and white chemical. On average, phthalic anhydride is produced in crystalline, fine-grained form. This chemical is sometimes produced without dyes and is used to produce plastics and various resins in the industry.

Is phthalic anhydride allergenic?

Yes! This substance can cause two types of allergies in the human body. These allergies include respiratory allergies and skin allergies. Phthalic anhydride skin allergy is delayed; It should be noted that PA skin allergies are rare.