Catalyst Decomposition Agents

Upon completion of the polymerisation of polyolefins by the Ziegler-Natta, low pressure routine, the organo-aluminium-titanium halide catalyst is decomposed and neutralised by the addition of low molecule weight alcohols and possibly aqueous wetting agents and soaps whilst pH control may be effected by the addition of aqueous alkalies such as sodium carbonate. This stage of the process can therefore introduce alcohols and alkali metal salts into the polymer. Similar comments apply in the case of the ferrocenyl catalysts now being used in polyolefin synthesis. 

---

More recently, the same catalyst was used to produce cyclic amines with retention of stereochemistry from a simple linear aliphatic azide [53]. Treatment of a substituted aliphatic azide by complex 66 afforded the cyclized compound 75, by insertion of the nitrene moiety in allylic, benzylic, and even in the less reactive tertiary C—H bonds. The catalyst is inhibited by coordination of the product to the metal center. However, that can be avoided by using an in situ protecting agent (Boep is preferred over Fmoc-OSuc which leads to catalyst decomposition). 

Catalysts. To make the final polyurethane, common catalysts are tertiary amines and organotin compounds, often used in mixtures. Amine catalysts favor the reaction of isocyanate with water, producing urea linkages and CO2, which acts as a blowing agent. On the other hand, organotin catalysts favor the isocyanate/hydroxyl reaction. Additional catalysts and catalyst decomposition products may be present if graft polyols are part of the mixture. The most common of these catalysts are free radical initiators. Phosphorus compounds may be present in the case of carbodiimide-modi-fied MDI. 

The product is considered nonhazardous for international transport purposes. However, it is an oxidizing agent sensitive to decomposition by water, direct sources of heat, catalysts, etc. Decomposition is accompanied by the Hberation of oxygen and heat which can support combustion and cause pressure bursts in confined spaces. Decomposition in the presence of organic material is rapid and highly exothermic. 

An excess of crotonaldehyde or aUphatic, ahcyhc, and aromatic hydrocarbons and their derivatives is used as a solvent to produce compounds of molecular weights of 1000—5000 (25—28). After removal of unreacted components and solvent, the adduct referred to as polyester is decomposed in acidic media or by pyrolysis (29—36). Proper operation of acidic decomposition can give high yields of pure /n j ,/n7 j -2,4-hexadienoic acid, whereas the pyrolysis gives a mixture of isomers that must be converted to the pure trans,trans form. The thermal decomposition is carried out in the presence of alkaU or amine catalysts. A simultaneous codistillation of the sorbic acid as it forms and the component used as the solvent can simplify the process scheme. The catalyst remains in the reaction batch. Suitable solvents and entraining agents include most inert Hquids that bod at 200—300°C, eg, aUphatic hydrocarbons. When the polyester is spHt thermally at 170—180°C and the sorbic acid is distilled direcdy with the solvent, production and purification can be combined in a single step. The solvent can be reused after removal of the sorbic acid (34). The isomeric mixture can be converted to the thermodynamically more stable trans,trans form in the presence of iodine, alkaU, or sulfuric or hydrochloric acid (37,38). 

Strong dehydrating agents such as phosphorous pentoxide or sulfur trioxide convert chlorosulfuric acid to its anhydride, pyrosulfuryl chloride [7791-27-7] S20 Cl2. Analogous trisulfuryl compounds have been identified in mixtures with sulfur trioxide (3,19). When boiled in the presence of mercury salts or other catalysts, chlorosulfuric acid decomposes quantitatively to sulfuryl chloride and sulfuric acid. The reverse reaction has been claimed as a preparative method (20), but it appears to proceed only under special conditions. Noncatalytic decomposition at temperatures at and above the boiling point also generates sulfuryl chloride, chlorine, sulfur dioxide, and other compounds. 

Cobalt salts are used as activators for catalysts, fuel cells (qv), and batteries. Thermal decomposition of cobalt oxalate is used in the production of cobalt powder. Cobalt compounds have been used as selective absorbers for oxygen, in electrostatographic toners, as fluoridating agents, and in molecular sieves. Cobalt ethyUiexanoate and cobalt naphthenate are used as accelerators with methyl ethyl ketone peroxide for the room temperature cure of polyester resins. 

---