PS Catalytic Cracking

Similarly the fluidized-bed pyrolysis of polystyrene in the presence of fluid catalytic cracking (FCC) catalysts was investigated at temperatures between 370 and 515°C [18]. In 

Waste-plastic-derived oil that was prepared by thermal degradation of municipal waste plastics at 410°C was dehydrochlorinated to remove chloroorganic compounds using various catalysts such as iron oxide, iron oxide-carbon composite, ZnO, MgO and red mud. The iron oxide catalysts were effective in removing the chloroorganic compounds. MgO and ZnO catalysts were deactivated during the reaction by HCl, which is produced by the dehydrochlorination of chloroorganic compounds. Iron oxide and its carbon composite were found to be stable in the dehydrochlorination of municipal waste plastic derived oil [19]. 

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However, other authors have proposed that the primary product of the PS catalytic cracking is styrene, as in thermal cracking, which is further converted into ethylbenzene, toluene, benzene, etc. on the acid sites of the catalyst. De la... 

The thermal and catalytic cracking of PP, PS, and SBR waste, dissolved in light cycle oil, was studied in a riser simulator. 19 refs. 

Likewise, Tang et al. [95] have investigated the catalytic cracking of mixtures of several polyolefins and PVC (PP/PVC, PE/PVC, PS/PVC) at 360-380°C over a novel Al-Zn composite. These authors observed that the composite accelerated the degradation of the plastic mixtures and retained the chlorine resulting from PVC degradation. 

Reentech Limited (Korea) has developed a patented catalytic cracking process (Figure 15.14) which converts mixed plastics (e.g. PE, PP, PS) into gasoline, kerosene and diesel fuel [27-31]. 

The components of products from thermal and catalytic cracking of HDPE, LDPE, LP, PP, PS were analyzed [48], and the results are shown in Table 28.2 and Table 28.3. The products from thermal cracking of HDPE, LDPE and LP (linear polyethylene) are mainly wax-like substances at normal temperamre. The fraction under 200°C recovered from HDPE accounts for 16% of the total cracking products, while that from LP accounts for 23%. Compared with tlie products of PE, PP produces less solid residue, but more liquid components, and PS produces the highest proportion of liquid fraction, which is 99.17% by thermal cracking and 99.56% by catalytic cracking. 

Catalysts tend to be deactivated in the process of plastics pyrolysis because of coke deposition on their surface. The deactivation of HZSM-5, HY, H-zeolite and silica-alumina was compared by Uemichi et al. [86]. In the case of PE pyrolysis and HZSM-5 added as catalyst, no deactivation occurred due to the low coke deposit, and high yields of light hydrocarbons (mainly branched hydrocarbons and aromatics) were achieved. In the case of PS, however, coke production increased dramatically, so HZSM-5 was deactivated very quickly. Silica-alumina catalyst was deactivated gradually and slowly with the increase of cracking gas, while HY- and H-zeolite molecule sieve catalysts were deactivated very quickly. Walendziewski et al. [87] studied the catalytic cracking of waste... 

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