Waxes pyrolysis-derived

Figure 1113 Gas chromatographic analysis of the wax material derived from the fluidized-bed pyrolysis of HDPE...

Table 8.2 Properties of pyrolytic wax derived from PE pyrolysis...

The detailed analysis of the derived oil/wax and gas products from the pyrolysis of plastics in relation to process conditions and different types of plastic is essential in providing data for the assessment of the feedstock recycling process. In addition, the yields and composition of gases and oils from the pyrolysis of mixed plastic waste are important in assessment of the process and to determine the possibility of any interactions between the plastics during pyrolysis. 

Figure 11.4 Fourier transform infrared spectra of the waxes derived from the pyrolysis of high-density polyethylene, low-density polyethylene and polypropylene...

Figure 11.5 shows that the functional group compositional analysis of the pyrolysis oil/waxes derived from the fixed-bed pyrolysis of PVC, PS and PET is very different from the polyalkene plastic pyrolysis oil/waxes. The spectra of the PVC pyrolysis oil/wax shows that the characteristic peaks of alkanes and alkenes are present as described for the polyalkene plastics. Since the PVC plastic polymer is based on a similar backbone structure to the polyalkene plastics, a similar degradation product oil/wax composition may be expected. However, the spectra for PVC in Figure 11.5 show that there are additional peaks in the region of 675-900 cm and 1575-1625 cm The presence of these peaks indicates the presence of mono-aromatic, polycyclic aromatic and substituted aromatic groups. Benzene has been identified as a major constituent in oils derived from the pyrolysis of PVC whilst other aromatic compounds identified included alkylated benzenes and naphthalene and other polycyclic aromatic hydrocarbons [19, 32, 39]... 

The pyrolysis oil/wax derived from the fixed-bed pyrolysis of PS produced a strong presence of both aromatic and aliphatic functional groups. The presence of CH3 and CH2 are indicated by the peaks between 3000 and 2800 cm and the peak in the region of... 

Figure 11.10 shows the molecular weight distribution for the oils and Figure 11.11 for the waxes derived from the fluidized-bed pyrolysis of the plastic mixture in relation to pyrolysis temperature. The oils show a higher proportion of low-molecular-weight species compared with the waxes and a clear bimodal distribution for the oils and waxes. The two peaks occur at molecular weights of about 120 and about 1200 Da., depending on whether... 

Thermoset plastics have also been pyrolysed with a view to obtain chemicals for recycling into the petrochemical industry. Pyrolysis of a polyester/styrene copolymer resin composite produced a wax which consisted of 96 wt% of phthalic anhydride and an oil composed of 26 wt% styrene. The phthalic anhydride is used as a modifying agent in polyester resin manufacture and can also be used as a cross-linking agent for epoxy resins. Phthalic anhydride is a characteristic early degradation product of unsaturated thermoset polyesters derived from orf/io-phthalic acid [56, 57]. Kaminsky et al. [9] investigated the pyrolysis of polyester at 768°C in a fiuidized-bed reactor and reported 18.1 wt% conversion to benzene. 

Aside from the use of the wax in cosmetics and specialty lubricant applications, the cost of the oil has limited its scope of incorporation into the industrial market. However, efforts by Shani et al. (9-12) have provided some degree of functionalization of jojoba, particularly at the olefin positions. These functionalizations fall into the classes of halogenation, allylic bromination-dehydrohalogenation, sulfurization, phosphorylation, ozonolysis, amination, oxidation, and pyrolysis. These derivatives are intended to boost the polarity of the wax or provide functionalization for binding to polymers. 

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