Poly recycling hydrolysis

About half of the wodd production comes from methanol carbonylation and about one-third from acetaldehyde oxidation. Another tenth of the wodd capacity can be attributed to butane—naphtha Hquid-phase oxidation. Appreciable quantities of acetic acid are recovered from reactions involving peracetic acid. Precise statistics on acetic acid production are compHcated by recycling of acid from cellulose acetate and poly(vinyl alcohol) production. Acetic acid that is by-product from peracetic acid [79-21-0] is normally designated as virgin acid, yet acid from hydrolysis of cellulose acetate or poly(vinyl acetate) is designated recycle acid. Indeterrninate quantities of acetic acid are coproduced with acetic anhydride from coal-based carbon monoxide and unknown amounts are bartered or exchanged between corporations as a device to lessen transport costs. 

Macromolecular Materials and Engineering 286, No. 10, 25th Oct.2001, p.640-7 POLY(ETHYLENE TEREPHTHALATE) RECYCLING AND RECOVERY OF PURE TEREPHTHALIC ACID. KINETICS OF A PHASE TRANSFER CATALYZED ALKALINE HYDROLYSIS... 

Polyesters, polyamides and other poly-condensation polymers can be chemically recycled simply by reversing their synthesis process by raising the process temperature, using traditional processes such as hydrolysis, ammonolysis, acidolysis, transesterification, etc. Bayer and other interested suppliers pioneered such processes that are beyond the scope of this book. Such processes can also be used for adjusting the MW required in one application (e.g. PET-bottles) to that needed in a different market (e.g. polyester fibres). 

Among polyesters synthesized from 1,4-benzenedicarboxylic acid and aliphatic diols, poly (ethylene terephthalate) (PET) and poly (butylene terephthalate) (PBT) are the most frequently applied ones. Hydrolysis is evidently the easiest chemical recycling technique of polyesters, however they may be mixed with other waste plastics, thus it is useful to know the properties of their pyrolysis product. 

Enzyme activity loss because of non-productive adsorption on lignin surface was identified as one of the important factors to decrease enzyme effectiveness, and the effect of surfactants and non-catalytic protein on the enzymatic hydrolysis has been extensively studied to increase the enzymatic hydrolysis of cellulose into fermentable sugars [7, 9 19]. The reported study showed that the non-ionic surfactant poly(oxyethylene)2o-sorbitan-monooleate (Tween 80) enhanced the enzymatic hydrolysis rate and extent of newspaper cellulose by 33 and 14%, respectively [20]. It was also found that 30% more FPU cellulase activity remained in solution, and about three times more recoverable FPU activity could be recycled with the presence of Tween 80. Tween 80 enhanced enzymatic hydrolysis yields for steam-exploded poplar wood by 20% in the simultaneous saccharification and fermentation (SSF) process [21]. Helle et al. [22] reported that hydrolysis yield increased by as much as a factor of 7, whereas enzyme adsorption on cellulose decreased because of the addition of Tween 80. With the presence of poly(oxyethylene)2o-sorbitan-monolaurate (Tween 20) and Tween 80, the conversions of cellulose and xylan in lime-pretreated com stover were increased by 42 and 40%, respectively [23]. Wu and Ju [24] showed that the addition of Tween 20 or Tween 80 to waste newsprint could increase cellulose conversion by about 50% with the saving of cellulase loading of 80%. With the addition of non-ionic, anionic, and cationic surfactants to the hydrolysis of cellulose (Avicel, tissue paper, and reclaimed paper), Ooshima et al. [25] subsequently found that Tween 20 was the most effective for the enhancement of cellulose conversion, and anionic surfactants did not have any effect on cellulose hydrolysis. With the addition of Tween 20 in the SSF process for... 

For polymers produced by condensation reactions (see Section 2.4), for example polyamides (PA) or poly(ethylene terephthalate) (PET), the plastic waste may be converted back directly to the monomer by hydrolysis. There is much developmental and pilot plant work in this area. The monomers can then be separated and introduced into the virgin feedstock for polymerization in the normal way. There is no way in which, for example, a PA polymerized from chemically recycled monomer will be inferior to virgin material. This is the ideal procedure, but it is applicable in only a few cases to the remainder of the polymer kingdom, the addition polymers (see Section 2.4). 

Selected chemolysis processes for PET are illustrated in Figure 9.8 and tabulated in Table 9.6. These reactions yield either the original monomers or products that can be converted to other monomers. Hydrolysis can be effectively used with PET and polyurethane waste plastics in feedstock recovery (Zia et al., 2007). Reaction conditions employed are varied and these selected references do not cover them exhaustively. Aromatic polyesters, PET and poly(butylene terephthalate), have been studied intensively for feedstock recovery. PET is extensively used in soda bottles and less than 30% of the product is mechanically recycled. 

Poly(3-hydroxyalkanoates) (PHAs) are a family of polyesters accumulated as inclusion bodies (Fig. 1) by a wide variety of bacteria. They are water-insoluble, relatively resistant to aqueous hydrolysis but are readily biodegraded in any natural environment where microbial diversity exists. They can be produced from renewable resources and waste materials and, although temperature-sensitive, are potentially recyclable. Many PHAs have mechanical properties similar to those of common synthetic plastics. 

The thermophilic actinomycete T. fusca produces cutinolytic activity when grown in media containing cutin or suberin [28]. The cutinase preparation showed a half-life of more than 1 h at 70°C and a pH optimum of 11.0. An enzyme preparation obtained from T. fusca KW3 grown in media containing PET hbers or suberin released hydrolysis products from PET hbers, poly(butylene terephthalate) hbers, and recycled PET granulate at 50 and 70°C [2]. 

Mishra, S. Goje, A S. Zope, V.S. Chemical Recycling, Kinetics, and Thermodynamics of Poly(Ethylene Terephthalate) (PET) Waste Powder by Nitric Acid Hydrolysis. Polymer Reaction Engineering. 2003,11, 79-99. 

Karayannidis, G.P. Chatziavgoustis, A.P., Achillas, D.S. Poly(ethylene terephthalate) Recycling and Recovery of Pure Terephthalic Acid by Alkaline Hydrolysis. Advances in Polymer Technology. 2002, 27, 250-259. 

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