Polyphosphoric acid

Description

Superphosphoric acid is made by the concentration of regular wet-process acid up to P2O5 concentrations of 78%. Granular polyphosphates suitable for bulk blending are made by reacting ammonia with regular wet process acid of 52% P2O5 content and using the heat of reaction to drive off water to produce a phosphate melt of 10-43-0, with about 40% of the phosphorus in the polyphosphate form. These materials are, however, not suitable for bulk blending due to their “sticky” nature (10).

Chemical Properties

Viscous, water-white liquid. Water solu- ble. Does not crystallize on standing; hygroscopic. The commercial acid is a mixture of orthophos- phoric acid with pyrophosphoric, triphosphoric, and higher acids and is sold on the basis of its calcu- lated content of H3PO4, e.g., 115%. Superphospho- ric acid is a similar mixture sold at 105% H3PO4. These acids revert slowly to orthophosphoric acid on dilution with water.

Uses

Polyphosphoric Acid is a ligand used as an analytical tool to image nanoparticles through photon emission topography. Used also in the synthesis of pharmaceuticals.

Uses

Polyphosphoric acid can be used as an analytical reagent in chemical industry and a powerful dehydrating agent for organic synthesis. It is used in production of acid phosphates and pharmaceuticals. Intermediate for production of phosphate esters with high mono-ester content. Polyphosphoric acid can be used as a catalyst during synthesis of dimethyl carbonate from urea and methanol. It is widely employed as acylation and alkylation reagent in various reactions. It can be used as a catalyst in the synthesis of various aromatic ketones. It may be used to prepare silica-supported polyphosphoric acid, an easy to handle, reusable heterogeneous catalyst. Polyphosphoric acid may be used in the synthesis of aromatic sulfones, N-substituted amides and 4-aminobenzophenones. Used as a catalyst and absorbent of ammonia during the synthesis of dimethyl carbonate (DMC). Used as a solvent in the synthesis of hyperbranched polybenzoxazoles.

Uses

Dehydrating, catalytic, and sequestering agents, for metal treating; many applications where a con- centrated monooxidizing acid is needed; laboratory reagent.

Definition

ChEBI: A polymerized phosphorus oxoacid of general formula HO[PO2OH]nH formed by condensation of orthophosphoric acid molecules and containing a backbone chain consisting of alternating P and O atoms covalent y bonded together.

General Description

Polyphosphoric acid (PPA) is widely employed as acylation and alkylation reagent in various reactions. It is a strong mineral acid with excellent dehydrating properties.

Hazard

Toxic by ingestion; strong irritant.

Agricultural Uses

Polyphosphoric acid is obtained by heating the wetprocess phosphoric acid. It contains around 72% phosphorus (as P₂O₅) and represents a series of phosphoric acids containing more than one atom of phosphorus (such as H₄P₂O₇). The general formula is H_n+2PnO_3n+1.

Solubility in water

Polyphosphoric acids are miscible with water, hydrolyzing to orthophosphoric acid with the generation of heat. They are insoluble in hydrocarbons and halogenated hydrocarbons.