Measurement and Testing


use of these oils lowers the pyrolysis temperature, resulting in an increased yield and a decreased energy cost [32]. Serrano et al. tested lubricating oil with LDPE (low-density polyethylene) in a range of concentrations in a screw kiln reactor (Figure 2) and was able to achieve complete conversion at acceptable temperatures.


35


Figure 2: Schematic of rotary kiln reactor with output hole for pyrolysis gas [34]


resulting oil had paraffi nic hydrocarbons as high as 96.8% and an absence of any oxygenated products. The resulting crude oil was synthesized to obtain: 20% motor oil, 41% diesel #1, 23% diesel #2, and 16% vacuum gas oil-range fractions. This conversion occurred at 440 celsius without the use of a catalyst.


Figure 1: Schematic of Fluidized Bed Reactor [33]


Also of interest is the kinetics of pyrolysis. Kinetic evaluation involves performing plastic cracking via thermogravimetric analysis techniques. The amount of plastic mass degraded and the reaction temperature are measured at regular time intervals [35]. The results of kinetic studies show that cracking is a fi rst- order reaction, consisting of a single-step degradation process. This generally holds true for polyamide (PA), polycarbonate (PC), and both LDPE and HDPE. Polyvinyl chloride (PVC) is reported to decompose over multi-reaction mechanisms, likely due to the release of HCl during degradation [36]. Activation energies can also be determined via kinetic evaluation. Sorun et al. examined PS, LDPE, HDPE, and PP, using a single reaction model. It was found that the lower activation energy bound for PS degradation is 311.5 kJ/mole, and the upper bound for HDPE is 445.1 kJ/ mole. The activation energy is determined by the dissociation energy for the different bonds, such as C=C, C-H, and C-C.


With increasing pyrolytic temperature, the yield of gasoline- range hydrocarbons increases. The yield of gaseous products also increases. In a pyrolysis experiment on mixed plastics, the highest yield of liquid fuel (76%) and gaseous products (28.5%) was obtained at 370 degrees celsius [38-39]. Also of note are comparative studies of yields from varying pyrolysis temperatures. Kamal et al. tested the pyrolysis of mixed plastics (2:1 ratio of PE to PP) at both 900 and 425 degrees celsius. It was determined that there were signifi cant differences in the calorifi c values of the two products, with the 900℃ pyrolysis product showing 46.8 MJ/kg, and the 425℃ product showing 41.8 MJ/kg. Interestingly, the higher temperature reduced the levels of carcinogenic compounds, including boric acid and cyclopentanone. Olefi n content is similarly infl uenced by temperature, showing a decrease with increasing pyrolysis temperature [40] This is likely a result of longer reaction times with lower temperatures, making fl ash pyrolysis a potentially more attractive method.


Successful Plastic to Fuel Processes


In real-world cases, all of these methods show promise. For non- catalytic pyrolysis, a temperature range as broad as 350-900℃ can be used, with varying results. In the 650-700℃ range, the weight percent of gases produced increases. When temperatures are near 500℃, oil containing aromatic hydrocarbons are produced [41].


Sarker et al.[19] tested pyrolysis at temperatures between 370 and 420℃ waste plastic degradation. In this study, the plastic was degraded to a slurry and then condensed, resulting in a range of hydrocarbons between C4H8 and C28H58 [42]. The differences between hydrocarbon products from waste plastic mixtures and individual plastics have been studied as well. Williams et al. pyrolyzed both waste mixtures and pure plastics in the presence of nitrogen and hydrogen. It was found that while the compositions of gas products from mixtures and individual plastics were similar, the mixed plastics produced higher concentrations of alkanes and aromatics. Sharma et al. pyrolyzed high-density polyethylene in the form of grocery bags. The


Also noteworthy are the pyrolysis tests performed using catalysts. Sarker et al. pyrolyzed waste polyethylene terephthalate to produce hydrocarbons at a temperature of 405℃. Hydrocarbons ranging from C3 to C27 were obtained, with very few oxygenated compounds. The study of the conversion of contaminated plastics to fuel is particularly interesting, as virtually all ocean MSW is contaminated. Miskolczi et al. examined the catalytic conversion of contaminated HDPE and PP. While the contaminants (Ca, P, C, and N) did distort the fuel properties, when the trial was run with the addition of ZSM-5, these distortions were negated. This lower concentration of impurities can be attributed to the contaminants attaching to the catalyst, and therefore becoming separated from the hydrocarbons. The presence of the catalyst also increased the percentage of lighter hydrocarbons and gasoline products. Isobutane formation was also higher when the catalyst was used.


Also tested was the impact of catalyst pore size on pyrolysis conversions. The use of HZSM-5, HY, and � zeolite catalysts was compared. Elordi et al. determined that smaller pore- sized catalysts, such as ZSM-5, resulted in an elevated yield of lighter olefi ns and gases. With the use of a catalyst with larger pores, non-aromatic compounds and higher hydrocarbons are predominantly produced. Also worth considering is the use of multiple catalysts in combination. Uemechi et al. utilized both HZSM-5 and SiO2-Al2O3, producing a high yield of gasoline with a high octane rating.


The potential of plastic pyrolysis cannot be understated. The conversion of waste plastic to fuel simultaneously addressed the issues of plastic pollution and reliance on fossil fuels, making it an attractive solution for the pollution and energy crises.


Conclusion


In the last 20 years, the use of plastics has skyrocketed. Yet, the same properties that make plastic so desirable, including its durability, light weight, and low cost, also make plastic a unique environmental danger. As plastics continue to accumulate in the ocean, the damage to marine ecosystems and wildlife becomes an increasingly urgent concern. Simultaneously, there is a continuous rise in the consumption and cost of fossil fuels. As the world continues to further its reliance on both plastic and fossil fuels, the conversion of waste plastics to fuel presents an attractive opportunity. As the majority of plastic waste is either polyethylene or polypropylene, most of the existing literature on plastic pyrolysis concerns PE and PP.


Municipal plastic wastes are easily converted into fuel-range hydrocarbons via pyrolysis and catalytic cracking processes. The thermal degradation of plastics has been proven an effective alternative fuel source and has potential for widespread adoption. For pyrolysis processes to become commonplace in both the plastics and energy industries, further study is recommended in several subsets. The use of catalysts is an opportunity for both enhanced effi ciency and greater selectivity in the fuel conversion process. The choice of catalyst is also impactful, with the pore size impacting the yield. Optimization is also possible through procedural changes, including catalyst loading, temperature, and reactor type. As suffi cient literature is published on the optimization of the degradation process and the fuel yields become uniform, the use of cracking techniques to repurpose plastic waste will become sustainable and widely adopted.


References


[1] Plastic Market Size. Share & Trends Analysis Report by Product (PE, PP, PU, PVC, PET, Polystyrene, ABS, PBT, PPO, Epoxy Polymers, LCP, PC, Polyamide), by Application, by Region, and Segment Forecast, 2020–2027. Available online: https://www. researchandmarkets.com/reports/4751797/plastic-market-size- share-and-trends-analysis


[2] Barnes, D.K.A., F. Galgani, R.C. Thompson & M. Barlaz. 2009. Accumulation and fragmentation of plastic debris in global environments. Philosophical Transactions of the Royal Society B: Biological Sciences 364: 1985-1998


[3] UNEP. 2009. Marine Litter: A Global Challenge. In: (Ed.). UNEP, Nairobi, Kenya. pp. 232


[4] Wabnitz, Colette & Nichols, Wallace. (2010). Editorial: Plastic Pollution: An Ocean Emergency. Marine Turtle NewsLetter. 20.


[5] Mrosovsky, N., G.D. Ryan & M.C. James. 2009. Leatherback turtles: The menace of plastic. Marine Pollution Bulletin 58: 287-289


[6] Derraik, J.G.B. 2002. The pollution of the marine environment by plastic debris: a review. Marine Pollution Bulletin 44: 842-852


[7] J. M. Escola, J. Aguado, D. P. Serrano, L. Briones, J. L. D´ıaz de Tuesta, R. Calvo and E. Fernandez, Energy Fuels, 2012, 26, 3187–3195.


[8] A. López, I. de Marco, B. M. Caballero, M. F. Laresgoiti, A. Adrados and A. Aranzabal, Appl. Catal., B, 2011, 104, 211–219.


[9] C. Dorado, C. A. Mullen and A. A. Boateng, ACS Sustainable Chem. Eng., 2014, 2, 301–311.


[10] Patni, N., Shah, P., Agarwal, S. and Singhal, P. (2013). Alternate Strategies for Conversion of Waste Plastic to Fuels. ISRN Renewable Energy, 2013, pp.1–7.


[11] A. Demirbas, “Biorefi neries: current activities and future developments,” Energy Conversion & Management, vol. 50, pp. 2782–2801, 2009


[12] Ohkita H, Nishiyama R, Tochihara Y, Mizushima T, Kakuta N, Morioka Y. Acid properties of silica-alumina catalysts and catalytic degradation of polyethylene. Industrial & Engineering Chemistry Research 1993;32(12):3112–6.


[13] Lee SY. Catalytic degradation of polystyrene over natural clinoptilolite zeolite. Polymer Degradation and Stability 2001;74(2):297–305


[14] Park DW, Hwang EY, Kim JR, Choi JK, Kim YA, Woo HC. Catalytic degradation of polyethylene over solid acid catalysts. Polymer Degradation and Stability 1999;65(2):193–8.


[15] Ding WB, Liang J, Anderson LL. Thermal and catalytic degradation of high density polyethylene and commingled post- consumer plastic waste. Fuel Processing Technology 1997;51(1– 2):47–62.


[16] Bagri R, Williams PT. Fluidised-bed catalytic pyrolysis of polystyrene. Journal of the Institute of Energy 2002;75(505):117–23.


[17] Park JJ, Park JW, Park J, Kim DC. Characteristics of LDPE pyrolysis. Korean Journal of Chemical Engineering 2002;19(4):658–62.


[18] Hwang EY, Kim JR, Choi JK, Woo HC, Park DW. Performance of acid treated natural zeolites in catalytic degradation of polypropylene. Journal of Analytical and Applied Pyrolysis 2002;62(2):351–64.


[19] Kim JR, Yoon JH, Park DW. Catalytic recycling of the mixture of polypropylene and polystyrene. Polymer Degradation and Stability 2002;76(1):61–7.


[20] Hwang EY, Choi JK, Kim DH, Park DW. Catalytic degradation of polypropylene I. Screening of catalysts. Korean Journal of Chemical Engineering 1998;15(4):434–8.


[21] Dawood, A.; Miura, K. Catalytic pyrolysis of γ-irradiated polypropylene (PP) over HYzeolite for enhancing the reactivity and the product selectivity. Polym. Degrad. Stab. 2002, 76 (1),


WWW.PETRO-ONLINE.COM


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76