Phosphoric acid polymeric acids

Phosphates are the principal catalysts used in polymerization units the commercially used catalysts are Hquid phosphoric acid, phosphoric acid on kieselguhr, copper pyrophosphate pellets, and phosphoric acid film on quartz. The last is the least active and has the disadvantage that carbonaceous deposits must occasionally be burned off the support. Compared to other processes, the one using Hquid phosphoric acid catalyst is far more responsive to attempts to raise production by increasing temperature. 

Cyanide blood agents are relatively unstable and tend to polymerize on standing. Polymers can be explosive. Stabilizers or solvents can be added to inhibit decomposition. Stabilizers include phosphoric acid, sulfuric acid, powdered sodium pyrophosphate, and sulfur dioxide. Although cyanide blood agents react with metals, they can be stored in steel or other common containers if stabilized. 

Chemical/Physical. Oxidation in air yields acetic acid (Windholz et ah, 1983). In the presence of sulfuric, hydrochloric, or phosphoric acids, polymerizes explosively forming trimeric paraldehyde (Huntress and Mulliken, 1941 Patnaik, 1992). In an aqueous solution at 25 °C, acetaldehyde is partially hydrated, i.e., 0.60 expressed as a mole fraction, forming a gem-diol (Bell and McDougall, 1960). Acetaldehyde decomposes at temperatures greater than 400 °C, forming carbon monoxide and methane (Patnaik, 1992). 

Phosphoric acid polymerization a process using a phosphoric acid catalyst to convert propene, butene, or both, to gasoline or petrochemical polymers. 

Derivatives of phosphoric acid, pyrophosphoric acid, and related compounds are very important in biological systems. Pyrophosphoric acid is an anhydride of phosphoric acid. Adenosine triphosphate, an energy carrier that is universally found in living organisms, has a phosphorus dianhydride connected to an adenosine group by a phosphate ester linkage. Phosphorus ester bonds are used to form the polymeric backbone of DNA (see Chapter 27). 

The Condensed Phosphoric Acids. Phosphoric acid easily undergoes the process of condensation. Condensation is the reaction of two or more molecules to form larger molecules, either without any other products (in which case the condensation is also called polymerization), or with the elimination of small molecules, such as water. Condensation of two phosphoric acid molecules occurs by the reaction of two... 

Concentrated sulphuric acid has been initially used for dimerization and oligomerization of cyclic monoolefins such as cyclohexene and diolefins such as cyclo-pentadiene, and later on for indene-coumarone fractions. Diluted sulphuric acid and benezenesulpho-nic acid have been further employed for the polymerization of more active cycloolefins like norbornene and dicyclopentadiene. In these reactions, monomer conversion, product yield and molecular mass depended largely on the acid concentration and monomer nature as well as on the other reaction parameters. Various compositions of initiators containing sulphuric acid in association with phosphoric acid, boric acid, sulphonic acids or inorganic sulphates of the type M (S04) (M = Al, Cr, Mg, Co, V) have also been reported for the polymerization of unsaturated alicyclic and cyclic fractions and for reactions with heavy aromatic fractions in hydrocarbon resin synthesis [2]. 

The problem of limited plant-food solubility was much alleviated by TVA s introduction of superphosphoric acid in 1957. Super-phosphoric acids are acids of high P2O5 content (up to 80% P2O5) that contain significant proportions of polyphosphates (non-ortho, polymerized phosphates). The data in Fig. 11.20 show the favorable effects of polyphosphate on plant-food solubility in ammoniated phosphoric acids. The super-phosphoric acid first produced by TVA was a pure electric-furnace product of 76 percent P2O5 content, of which about 50 percent was in polyphosphate form. With ammoniation of... 

Phosphoric Acid Polymerization. At least three modifications in the use of phosphoric acid as a catalyst are widely used (1) quartz wetted with liquid acid, (2) acid-impregnated pellets (solid phosphoric acid)... 

Polymerization. Paraldehyde, 2,4,6-trimethyl-1,3-5-trioxane [123-63-7] a cycHc trimer of acetaldehyde, is formed when a mineral acid, such as sulfuric, phosphoric, or hydrochloric acid, is added to acetaldehyde (45). Paraldehyde can also be formed continuously by feeding Hquid acetaldehyde at 15—20°C over an acid ion-exchange resin (46). Depolymerization of paraldehyde occurs in the presence of acid catalysts (47) after neutralization with sodium acetate, acetaldehyde and paraldehyde are recovered by distillation. Paraldehyde is a colorless Hquid, boiling at 125.35°C at 101 kPa (1 atm). 

Polygas Olefins. Refinery propylene and butenes are polymerized with a phosphoric acid catalyst at 200°C and 3040—6080 kPa (30—60 atm) to give a mixture of branched olefins up to used primarily in producing plasticizer alcohols (isooctyl, isononyl, and isodecyl alcohol). Since the olefins are branched (75% have two or more CH groups) the alcohols are also branched. Exxon, BASE, Ruhrchemie (now Hoechst), ICl, Nissan, Getty Oil, U.S. Steel Chemicals (now Aristech), and others have all used this olefin source. 

Thermal polymerization is not as effective as catalytic polymerization but has the advantage that it can be used to polymerize saturated materials that caimot be induced to react by catalysts. The process consists of the vapor-phase cracking of, for example, propane and butane, followed by prolonged periods at high temperature (510—595°C) for the reactions to proceed to near completion. Olefins can also be conveniendy polymerized by means of an acid catalyst. Thus, the treated olefin-rich feed stream is contacted with a catalyst, such as sulfuric acid, copper pyrophosphate, or phosphoric acid, at 150—220°C and 1035—8275 kPa (150—1200 psi), depending on feedstock and product requirement. 

At equihbrium, the specific composition of a concentrated phosphoric acid is a function of its P2 s content. Phosphoric acid solutions up to a concentration equivalent of about 94% H PO (68% P2O5) contain H PO as the only phosphoric acid species present. At higher concentrations, the orthophosphoric acid undergoes condensation (polymerization by dehydration) to yield a mixture of phosphoric acid species (Table 5), often referred to genericaHy as polyphosphoric or superphosphoric acid, H20/P20 = - 3, or ultraphosphoric acid, H20/P20 = - 1. At the theoretical P2O5 concentration for orthophosphoric acid of 72.4%, the solution is actually a mixture containing 13% pyrophosphoric acid and about 1% free water. Because the pyrophosphoric acid present is the result of an equihbrium state dependent on the P2 5 content of the solution, pure orthophosphoric acid can be obtained because of a shift in equihbrium back to H PO upon crystallization. 

Higher polymeric forms, eg, (ROP ), also exist (see Phosphoric ACIDS AND PHOSPHATBs). 

Phosphorus(III) Oxide. Phosphoms(III) oxide [12440-00-5] the anhydride of phosphonic acid, is formed along with by-products such as phosphoms pentoxide and red phosphoms when phosphoms is burned with less than stoichiometric amounts of oxygen (62). Phosphoms(III) oxide is a poisonous, white, wax-like, crystalline material, which has a melting point of 23.8°C and a boiling point of 175.3°C. When added to hot water, phosphoms(III) oxide reacts violentiy and forms phosphine, phosphoric acid, and red phosphoms. Even in cold water, disproportionation maybe observed if the oxide is not well agitated, resulting in the formation of phosphoric acid and yellow or orange poorly defined polymeric lower oxides of phosphoms (LOOP). 

Nylon-11. This nylon is produced from 11-aminoundecanoic acid, which is derived from castor oil. The acid is polymerized by heating to 200°C with continuous removal of water. Catalysts such as phosphoric acid are frequentiy used. There is no appreciable amount of unreacted monomer left in the product. 

Many other polymerization processes have been patented, but only some of them appear to be developed or under development ia 1996. One large-scale process uses an acid montmorrillonite clay and acetic anhydride (209) another process uses strong perfiuorosulfonic acid reski catalysts (170,210). The polymerization product ia these processes is a poly(tetramethylene ether) with acetate end groups, which have to be removed by alkaline hydrolysis (211) or hydrogenolysis (212). If necessary, the product is then neutralized, eg, with phosphoric acid (213), and the salts removed by filtration. Instead of montmorrillonite clay, other acidic catalysts can be used, such as EuUer s earth or zeoHtes (214—216). 

Under certain conditions hydrogen cyanide can polymerize to black soHd compounds, eg, hydrogen cyanide homopolymer [26746-21-4] (1) and hydrogen cyanide tetramer [27027-02-2], C H N (2). There is usually an incubation period before rapid onset of polymer formation. Temperature has an inverse logarithmic effect on the incubation time. Acid stabilizers such as sulfuric and phosphoric acids prevent polymerization. The presence of water reduces the incubation period. 

In laboratory preparations, sulfuric acid and hydrochloric acid have classically been used as esterification catalysts. However, formation of alkyl chlorides or dehydration, isomerization, or polymerization side reactions may result. Sulfonic acids, such as benzenesulfonic acid, toluenesulfonic acid, or methanesulfonic acid, are widely used in plant operations because of their less corrosive nature. Phosphoric acid is sometimes employed, but it leads to rather slow reactions. Soluble or supported metal salts minimize side reactions but usually require higher temperatures than strong acids. 

Alkylation of furan and thiophene has been effected with alkenes and catalysts such as phosphoric acid and boron trifluoride. In general, Friedel-Crafts alkylation of furans or thiophenes is not preparatively useful, partly because of polymerization by the catalyst and partly because of polyalkylation. 

The term novolac refers to the early use of phenolic to replace expensive shellac-based coatings. Novolacs are now those resins made at formaldehyde-to-phenol molar ratios of less than one-to-one. They are generally, though not always, manufactured under acidic conditions. Sulfuric or oxalic acids are most often chosen as catalyst though aromatic sulfonic acids and phosphoric acid are also quite common. Many other acids are used for special purposes. The finished novolac resin is incapable of further polymerization or crosslinking and therefore... 

---