The gas chromatography-mass spectrometry (GC-MS) analysis of oil showed a mixture of aromatics, aliphatic and other hydrocarbon compounds. Stab. Pyrolysis of poly (ethylene terephthalate) in a fluidised bed plant. Pyrolysisgasification of plastics, mixed plastics and real-world plastic waste with and without NiMgAl catalyst. The pyrolysis oil obtained from various plastic types need to be cleaned significantly before it is used in any application, to ensure minimal environmental impact. Serious consideration is therefore needed in this regard. Naturally, NZ is found in Japan, USA, Cuba, Indonesia, Hungary, Italy, and the Kingdom of Saudi Arabia (KSA) (Sriningsih et al., 2014; Nizami et al., 2016). Saptoadi and Pratama (2015) successfully used pyrolytic liquid oil as an alternative in a kerosene stove. doi: 10.1016/j.fuproc.2014.06.018, Inman, M. (2012). The major compounds found were; benzene, 1,1-(1,3-propanediyl)bis-, mono(2-ethylhexyl) ester, 1,2-benzenedicarboxylic acid, anthracene, pentadecane, phenanthrene, 2-phenylnaphthalene and so on (Figures 4B, 5B). The char production was higher (29.7%) with the AA-NZ catalyst than (19.0%) with the TA-NZ catalyst, which may be due to polymerization reactions (Wu and Williams, 2010). FT-IR analysis of liquid oil produced from catalytic pyrolysis with TA-NZ. doi: 10.1002/app.1982.070270306. Tekin et al. Fuel Process. Environ. The functional groups in pyrolysis oil was analyzed by a FT-IR, Perkin Elmer's, UK instrument. J. Anal. doi: 10.1016/j.fuel.2010.05.032, Wu, J., Chen, T., Luo, X., Han, D., Wang, Z., and Wu, J. Chem. Stab. In order to obtain an oil product in the pyrolysis of waste plastics, the major steps for waste plastics that are derived from the household, industry, etc. Furthermore, the potential and challenges of pyrolysis-based biorefineries have been discussed. This material can block the flow line and make difficult the continuous control of unit process. (2016b) reported that feedstock composition also affects the quality and chemical composition of the oil. Energy Environ. Technol. Liquid and gaseous fuel from waste plastics by sequential pyrolysis and catalytic reforming processes over indonesian natural zeolite catalysts. Catal. A very strong peak at 696 cm1 was observed in most of the liquid oils obtained using both catalysts, which corresponds to the high concentration of aromatic compounds. Catalytic conversion of polyolefins into liquid fuels over MCM-41: comparison with ZSM-5 and amorphous SiO2Al2O3. Similarly, more focus is needed to conduct further research and development work on enriching the biorefinery concept and to tap into its true potential. Polym. Int. doi: 10.1016/j.wasman.2011.05.021, Lopez, G., Olazar, M., Artetxe, M., Amutio, M., Elordi, G., and Bilbao, J. However, microporous catalysts hinder the entrance of larger molecules and thus higher carbon chain compounds are produced from catalytic pyrolysis of PE with microporous catalysts. Thermogravimetric analysis (TGA) of PS, PE, PP, and PET plastic waste. Afterward, the sample was washed with deionized water until a normal pH was obtained. Res. Stab. Received: 15 November 2018; Accepted: 22 February 2019; Published: 19 March 2019. The lowest HHV of 41.7 MJ/ kg was found in liquid oil obtained from PS using the TA-NZ catalyst, whereas the highest HHV of 44.2 MJ/kg was from PS/PE/PP using the AA-NZ catalyst. Recovery of indan derivatives from polystyrene waste. Thus, the pyrolysis liquid oil produced from various plastic wastes has the potential to be used as an alternative source of energy. A Gen. 278, 3743. The liquid oil produced from the individual plastic types such as PS, PP and PE contained a mixture of aromatics, aliphatic and other hydrocarbon compounds. (2014) reported that AA-NZ with HCl has high acidity compared to TA-NZ, produced less liquid oil yield and had high production of gases. (2011) reported that the use of catalysts decreases the process temperature. Fuel Process. Protect. These results were further confirmed by the FT-IR analysis showing clear peaks corresponding to aromatic and other hydrocarbon functional groups. Proc. A capillary GC 30 m long and 0.25 mm wide column coated with a 0.25 m thick film of 5% phenyl-methylpolysiloxane (HP-5) was used. Polym. Conversion of polyethylene into gasoline-range fuels by two-stage catalytic degradation using SilicaAlumina and HZSM-5 Zeolite. The plastic waste used as the feedstock in the catalytic pyrolysis process was collected from Jeddah and included grocery bags, disposable juice cups and plates, and drinking water bottles, which consist of polyethylene (PE), polypropylene (PP) polystyrene (PS), and polyethylene terephthalate (PET) plastics, respectively. Several researchers activated the char via steam and thermal activation (Lopez et al., 2009; Heras et al., 2014). Energy Technol. Appl. (2004). (2015) reported that 20:80% blend ratio of pyrolytic liquid oil and conventional diesel, respectively, gave similar engine performance results than conventional diesel. Effects of the types of zeolites on catalytic upgrading of pyrolysis wax oil. Comput. J. Anal. Polym. Catalytic degradation of polystyrene over natural clinoptilolite zeolite. The catalytic pyrolysis of PS produced a higher liquid oil (70 and 60%) than PP (40 and 54%) and PE (40 and 42%), using TA-NZ and AA-NZ catalysts, respectively. Polym. doi: 10.1016/j.wasman.2013.12.005, Xue, Y., Johnston, P., and Bai, X. Application of waste plastic pyrolysis oil in a direct injection diesel engine: For a small scale non-grid electrification. The editor and reviewer's affiliations are the latest provided on their Loop research profiles and may not reflect their situation at the time of review. doi: 10.1016/j.fuel.2014.05.028, Keywords: catalytic pyrolysis, pyrolysis based biorefineries, natural zeolite, plastic waste, aromatic compounds, modified natural zeolite, catalyst, Citation: Miandad R, Rehan M, Barakat MA, Aburiazaiza AS, Khan H, Ismail IMI, Dhavamani J, Gardy J, Hassanpour A and Nizami A-S (2019) Catalytic Pyrolysis of Plastic Waste: Moving Toward Pyrolysis Based Biorefineries. In the pyrolysis process, one of the most important decision items is the degradation temperature in the reactor. The catalytic pyrolysis of different types of plastics waste (PS, PE, PP, and PET) as single or mixed in different ratios, in the presence of modified natural zeolite (NZ) catalysts in a small pilot scale pyrolysis reactor, was carried out for the first time. Thus, the feeding system will be determined by the profile of waste plastics that are exited from industry, agriculture and household, etc. Chem. Waste Technol. 202, 775784. There was a significant difference in the liquid oil yield of 54 and 34% for catalytic pyrolysis of PS/PP (50/50% ratio) with TA-NZ and AA-NZ catalysts, respectively. Degrad. (2011) reported the possible degradation mechanism of PS on acid catalysts that may occur due to the attack of a proton associated with Bronsted acidic sites, resulting in the carbenium ion mechanism, which further undergoes -scission and is later followed by hydrogen transfer. 29, 273283. Obali et al. The energy and value- added products from pyrolysis of waste plastics, in Recycling of Solid Waste for Biofuels and Bio- Chemicals, eds O. P. Karthikeyan, K. H. Subramanian, and S. Muthu (Singapore: Springer), 333355. Fuel Process. All types of plastic waste show similar degradation behavior with the rapid loss of weight of hydrocarbons within the narrow range of temperature (150250C) (Figure 2). There are many challenges and room for improvement in pyrolysis-based biorefineries, that need to be addressed and optimized to ensure maximum benefits. Nileshkumar et al. doi: 10.1016/j.polymdegradstab.2005.05.028, Lee, K. H. (2012). Initially, degradation starts on the external surface of the catalysts and later proceeds with further degradation in the inner pores of the catalysts (Lee, 2012). The effect of thermal and acid activation of NZ on the product yield of the pyrolysis process was examined (Figure 3). 102, 822838. (A,B) GC-MS of liquid oil produced from different types of plastic waste with AA-NZ. 58, 250259. Plastic waste production and consumption is increasing at an alarming rate, with the increase of the human population, rapid economic growth, continuous urbanization, and changes in life style. (1998) carried out catalytic pyrolysis of polyethylene (PE) with HZSM-5 catalysts. doi: 10.1016/j.jaap.2004.03.001, Dimitrov, N., Krehula, L. K., Siroi, A. P., and Hrnjak-Murgi, Z. 27, 857869. Biodegrad. The use of synthetic catalysts enhanced the overall pyrolysis process and improved the quality of produced liquid oil. The char production was lowest in this case, 7.2 and 13.0% with AA-NZ and TA-NZ, respectively. (2018) used the char obtained from pyrolysis of PS plastic waste to synthesize a novel carbon-metal double-layered oxides (C/MnCuAl-LDOs) nano-adsorbent for the adsorption of Congo red (CR) in wastewater. The global plastic production was estimated at around 300 million tons per year and is continuously increasing every year (Miandad et al., 2016a; Ratnasari et al., 2017). doi: 10.1016/j.fuel.2013.08.044. These extra peaks corresponded to aromatics, alkanes and alkene compounds. Today 62, 6775. Technol. However, microporous and less acidic catalysts favor the production of long chain hydrocarbons as the cracking process occurred only on the outer surface of the catalysts. Figure 2. Polymer Degrad. (2012) carried out pyrolysis of PP with an alumina-loaded catalyst and reported the maximum production of gas. Furthermore, the presence of PP also enhances gas production due to the carbocation process during degradation (Jung et al., 2010). The initial degradation of PET was perhaps due to the presence of some volatile impurities such as diethylene glycol (Dimitrov et al., 2013). The rest of the gas products consisting of light hydrocarbons can be used as fuel gas in the heating system. doi: 10.1002/1521-3935(20010301)202:6<775::AID-MACP775>3.0.CO;2-G, Ramli, M. R., Othman, M. B. H., Arifin, A., and Ahmad, Z. (2000) reported that hydrogenation of styrene increased with the increase of the reaction temperature. Physico-chemical characterization of chars produced in the co-pyrolysis of wastes and possible routes of valorization, in Chemical Engineering (Lisboa: Universidade Nova de Lisboa), 2736. *Correspondence: Mohammad Rehan, dr.mohammad_rehan@yahoo.co.uk, Waste Biorefineries: Future Energy, Green Products and Waste Treatment, View all Waste Manag. Waste Manag. 85, 539543. The pyrolysis reactor can hold up to 20 L of feedstock and the maximum working safe temperature of up to 600C can be achieved with the desired heating rates. A process study on the pyrolysis of waste polyethylene. A pyrolysis based biorefinery can be developed to treat a range of biomass waste and plastic waste to produce liquid and gas fuels, energy, biochar, and other higher value chemicals using an integrated approach. (2011) reported that catalysts with high acidity enhanced the cracking of polymers during the catalytic pyrolysis. (2016b). 142, 441451. (2014) carried out TGA of PS with PE and observed two peaks, the first one for PS at a low temperature, followed by PE degradation at a high temperature. Wu et al. Energy 108, 162171. RM performed the pyrolysis experiments and helped in manuscript write up. Chem. (2011) and Seo et al. The liquid oil produced from the catalytic pyrolysis of PE, when using both catalysts, produced mainly Naphthalene, Phenanthrene, Naphthalene, 2-ethenyl-, 1-Pentadecene, Anthracene, 2-methyl-, Hexadecane and so on (Figures 4A, 5A). Bomb Calorimeter and TGA (Mettler Toledo TGA/SDTA851) by adopting the standard ASTM methods. Gaca et al. Technol. Fuel production from LDPE plastic waste over natural zeolite supported Ni, Ni-Mo, Co and Co-Mo metals. The gases produced from pyrolysis of some plastic waste such as PVC are toxic, and therefore pyrolysis emission treatment technology has to be further refined to achieve maximum environmental benefits. (2006). doi: 10.1016/j.jaap.2014.06.013, Aguado, J., Sotelo, J. L., Serrano, D. P., Calles, J. A continuous condensation system using a water bath and ACDelco Classic coolant was used to ensure the condensation temperature was kept below 10C, and to ensure the maximum condensation of vapor to liquid oil. Thus, in order to reduce the melting time of reactant in the melting system, it needs be heated in the feeding system prior to the melting system. doi: 10.1016/S0921-3449(00)00052-5, Kunwar, B., Moser, B. R., Chandrasekaran, S. R., Rajagopalan, N., and Sharma, B. K. (2016). World Bank. Conversion of methoxy and hydroxyl functionalities of phenolic monomers over zeolites. J. Moreover, Yoshioka et al. doi: 10.1016/j.polymdegradstab.2004.02.015, Lopez, A., Marco d, I., Caballero, B. M., Laresgoiti, M. F., Adrados, A., and Torres, A. Polystyrene degradation studies using Cu supported catalysts. Waste Manag. Pyrolysis 72, 2733. The outcomes of LCA will help to determine the sustainability of biorefineries, which is crucial in making the right decision. Vol. Biorefining 8, 645657. Wu, C., and Williams, P. T. (2010). Catalytic pyrolysis of low density polyethylene using cetyltrimethyl ammonium encapsulated monovacant keggin units and ZSM-5. 11, 22781684. Untapped conversion of plastic waste char into carbon-metal LDOs for the adsorption of Congo red. 186, 189196. (2017a). In addition, due to rapid urbanization, the land available for landfills, especially in cities, is reducing. Polym. In the third step, the separated plastics are delivered by the feeding system such as the conveyer, hopper and extruder, etc. Continue reading here: Total Mass Balance, General Scheme Of Waste Polyolefin Processing, Georges Voituron - Pvc and Mixed Plastics. Lee (2012) reported that ZSM-5 produced more aromatic compounds compare to the mordenite catalyst, due to its crystalline structure. Figure 7. Siddiqui and Redhwi (2009) reported that PS has a cyclic structure, which leads to the high yield of liquid oil from catalytic pyrolysis. The oven was set at 50C for 2 min and then increased up to 290C using a 5C/min heating rate. doi: 10.1016/j.energy.2016.06.024, Lecomte, H. A., and Liggat, J. J. Bhaskar, T., Kaneko, J., Muto, A., Sakata, Y., Jakab, E., Matsui, T., et al. (2006) carried out pyrolysis of PS with PE with a ratio of 10 and 90%, respectively, and reported the maximum production of aromatics even at a very low ratio of PS. J. Taiwan Inst. Figure 4. doi: 10.1016/j.fuproc.2009.01.003, Sriningsih, W., Saerodji, M. G., Trisunaryanti, W., Armunanto, R., and Falah, I. I. Aguado et al. doi: 10.1016/j.polymdegradstab.2004.06.001, Zeaiter, J. 70, 383398. 17, 2535. Moreover, the film type reactant is very bulky and voluminous, which makes it difficult to ensure continuous feeding, is easily dosed at the melting system after melting in the feeding system. Chapter 17-Wastewater Biorefinery based on the microbial electrolysis cell: opportunities and challenges, in Progress and Recent Trends in Microbial Fuel Cells, eds K. Dutta and P. Kundu (New York, NY: Elsevier Inc.), 347374. J. As the temperature increases above certain values, the plastic waste (organic polymers) converts into monomers that are transferred to the condenser, where these vapors are condensed into liquid oil. Steam activation of pyrolytic tyre char at different temperatures. Adv. Effect of catalyst contact mode and gas atmosphere during catalytic pyrolysis of waste plastics. The produced liquid oil from catalytic pyrolysis of PE/PP contains aromatic, olefin, and naphthalene compounds. Basically, waste plastics are melted to materials of low viscosity and then the liquefied reactant is thermally decomposed to low-molecular-weight hydrocarbons in the pyrolysis reactor. The catalytic reaction during the pyrolysis of plastic waste on solid acid catalysts may include cracking, oligomerization, cyclization, aromatization and isomerization reactions (Serrano et al., 2012). The feeding system is continuously controlled with a constant reactant amount and classified as heated or nonheated case of the extruder. Overall catalytic pyrolysis of PP/PE produced the maximum amount of gas with low amounts of char. HK, JD, JG, and AH have carried out the detailed characterization of the process products. Fuel 89, 30223032. Appl. A., and Escola, J. M. (1997). (2016b) reported that thermal pyrolysis of PE with PS without a catalyst, resulted in the conversion of PE into liquid oil with a high composition of aromatics. Ramli et al. Stab. Eng. If it contains a lot of various contaminative materials in waste plastics, it leads to poor economics by increasing the recycling procedure cost. Alexandra, L. C. (2012). Benzene, 1,1-(2-butene-1,4-diyl)bis-, benzene, 1,1-(1,3-propanediyl)bis-, anthracene, 9-methyl-, naphthalene, 2-phenyl-, 1,2,3,4-tetrahydro-1-phenyl-, naphthalene, phenanthrene etc. J. Chem. Energy. Green Chem. 2016:2857162. doi: 10.1155/2016/2857162. Demirbas (2004) carried out pyrolysis of PS/PE/PP and reported similar results for the product yield. Several studies reported the use of microporous and mesoporous catalysts for the conversion of plastic waste into liquid oil and char. Thermal degradation of polyethylene and polystyrene from the packaging industry over different catalysts into fuel-like feed stocks. Process Safety Environ. However, the use of synthetic catalysts increased the cost of the pyrolysis process. 34, 187204. Polym. The chemical composition of the liquid oil was analyzed by GC-MS. Biodeterior. Thus, the important point for the pyrolysis process is the purification of waste thermoplastics, especially excluding PVC and PET in the reactant. doi: 10.1016/S0920-5861(00)00409-0, Waqas, M., Rehan, M., Aburiazaiza, A. S., and Nizami, A. S. (2018). Catalysts have a very critical role in promoting process efficiency, targeting the specific reaction and reducing the process temperature and time (Serrano et al., 2012; Ratnasari et al., 2017). In reality however, oil from most plastic waste has a complex chemical structure and may contain other groups of unidentified chemicals such as sulfur, nitrogen, and oxygen-containing hydrocarbons. There are two possible mechanisms which may involve the degradation of PE in the presence of a catalyst; hybrid ion abstraction due to the presence of Lewis sites or, due to the carbenium ion mechanism via the addition of a proton (Rizzarelli et al., 2016). (2004) used different kinds of catalysts and reported that even mixing of HZSM-5 with mesoporous SiO2-Al2O3 or MCM-41 led to the maximum production of liquid oil with minimal gas production. The initial degradation of PE and PET may be due to the presence of some volatile impurities such as the additive filler used during plastic synthesis (Dimitrov et al., 2013). The identified peaks were matched with the NIST and mass bank spectra library. Effect of TA-NZ and AA-NZ on the pyrolysis product yield. 76, 6167. (1982) carried out pyrolysis of PS with the alumina-silica catalyst at 300C and found the hydrogenation of styrene to its derivate. J. Anal. (1999). Front. Pyrol. J. Anal. Eng. doi: 10.1021/ie980341+, Ukei, H., Hirose, T., Horikawa, S., Takai, Y., Taka, M., Azuma, N., et al. (2015) and Rehan et al. doi: 10.1080/15567036.2016.1153753, Rizzarelli, P., Rapisarda, M., Perna, S., Mirabella, E. F., La Carta, S., Puglisi, C., et al. Utilization of plastics waste oil as partial substitute for kerosene in pressurized cookstoves. Miskolczi, N., Bartha, L., and Deak, G. (2006). The distribution of the oil product must be decided by market circumstances. B:Environ. (2018). The chemical composition of oil was studied using a GC-MS (Shimadzu QP-Plus 2010) with FI detector. 14 Articles, This article is part of the Research Topic, Creative Commons Attribution License (CC BY). The Combustion of Organic Polymers. (2017). 74, 297305. 5:18. doi: 10.5539/eer.v5n1p18, Lee, S. Y., Yoon, J. H., Kim, J. R., and Park, D. W. (2001). Polym. (2017b). Also the nonvolatile material generated in the melting and pyrolysis process, which includes a small amount of volatile hydrocarbon components, is discharged to a sludge treatment system. (2004) reported the maximum production of gas and char with negligible liquid oil production from catalytic pyrolysis of PET. FT-IR results showed clear peaks of aromatic compounds in all liquid oil samples with some peaks of alkanes that further confirmed the GC-MS results. Moreover, the HHV of the produced liquid oil has been found in the range of 41.744.2 MJ/kg (Table 2) which is very close to the energy value of conventional diesel. doi: 10.1016/j.cej.2012.06.146, Ogawa, T., Kuroki, T., Ide, S., and Ikemura, T. (1982). The problem is the fact that carbon residues tend to foul the walls of the reactor and thus give poor heat transfer from the external wall to the center of the reactor. Plastic waste recycling is carried out in different ways, but in most developing countries, open or landfill disposal is a common practice for plastic waste management (Gandidi et al., 2018). The catalytic pyrolysis of PS mainly produces styrene and its derivate as the major compounds in the produced liquid oil (Siddiqui and Redhwi, 2009; Rehan et al., 2017). doi: 10.1016/j.fuproc.2016.01.018, Marcilla, A., Beltrn, M. I., Hernndez, F., and Navarro, R. (2004). TG/FTIR analysis on co-pyrolysis behavior of PE, PVC and PS. The potential of Saudi Arabian natural zeolites in energy recovery technologies. The chemical composition of the pyrolysis oil was analyzed using GC-MS, and it was found that most of the liquid oil produced a high aromatic content with some aliphatic and other hydrocarbon compounds. PS degradation starts with cracking on the outer surface of the catalyst and is then followed by reforming inside the pores of the catalyst (Uemichi et al., 1999). doi: 10.1002/bbb.1474, Demirbas, A. Energy Inst. In the pyrolysis and catalytic degradation of polymer at temperature 300-450C the melted reactant is degraded into a smaller molecule and also upgraded to oil product with a high quality. The characteristics of this process are the quality of the oil product, very similar to that of conventional gasoline, kerosene and diesel oils, but the drawback of the catalyst is high cost and short life-cycle due to poisoning/deactivation. Energy Conv. Similarly, a significant difference in the char yield of 20.3 and 35.2% was observed, whereas the high yield of gases were 25.7 and 30.8% using TA-NZ and AA-NZ catalysts, respectively. Degrad. doi: 10.1016/S0141-3910(01)00266-X, Kiran, N., Ekinci, E., and Snape, C. E. (2000). 127, 157162. (2017) also reported the high production of char from the catalytic pyrolysis of PS with an acidic zeolite (H) catalyst. Ind. Furthermore, in the presence of acid catalysts, PS degradation followed a carbenium mechanism, which further underwent hydrogenation (inter/intramolecular hydrogen transfer) and -scission (Serrano et al., 2000). Pyrol. Although pyrolysis oil holds more energy than coal and some other fuels, pyrolysis itself is an energy-intensive process, and the oil product requires more energy to be refined (Inman, 2012). For the processes of different reactor types, kiln and retort pyrolysis processes are characterized by a relatively low capital investment.

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