The Akzo Process

Akzo Nobel is an important producer of chlorine, vinyl chloride and PVC, strongly interested in a process for feedstock recycling of MPW containing PVC. Since 1994 they have chosen a fast pyrolysis process in a circulating fluidized-bed reactor, based on the technique developed by the Battelle Memorial Institute (CO, USA) for biomass gasification. 

Process performance and commercial status. The Akzo process was investigated on a pilot scale (30 kg/h) with PVC cable and pipe scrap. Some tests with mixed PVC waste were carried out on a larger scale (300 kg/h) with the support of the European Council of Vinyl Manufacturers, giving promising results. At the moment the project is on hold, even though there is a plan to realize an industrial-scale plant, with a capacity of about 50000 t/yr. On the other hand, Akzo Nobel has stopped all activities on HCl recycling from PVC [50]. The process is still at pilot-scale status, so that large uncertainty exists about its technical, enviromnental and economic performance. 

---

However, the production of the />-phenylenediamine [106-50-3] intermediate is more complex, because it involves the diazotization and coupling of aniline [65-53-3]. Aniline reacts with nitrogen oxides, produced via the oxidation of ammonia, to form 1,3-diphenyltriazene [136-35-6] in the process used by Du Pont (208,209) (see Amines, aromatic-aniline and its derivatives). In the Akzo process a metal nitrite salt and acid in water is used (210). The triazene rearranges in the presence of acid and an excess of aniline to form predominately the p-aminoazobenzene [60-09-3] and a small amount of the ortho isomer, 0-aminoazobenzene [2835-58-7]. The mixture of isomers is catalytically reduced to the respective diamines, and they are then separated from the aniline, which is recycled (208,209). The 0-phenylenedi amine [95-54-5] is used in the manufacture of herbicides (see Amines, aromatic-phenylenediamines). 

---