Pyrolysis Of Waste Polyethylene Research Articles

Pyrolysis of waste polyethylene in a semi-batch reactor to produce liquid fuel: Optimization of operating conditions

This study investigated the interactive effects of temperature, residence time, and carrier gas flow rate on the liquid fuel production through the pyrolysis of waste polyethylene (WPE) in a bench-scale semi-batch reactor. To enhance the liquid fuel production, fifteen experiments were conducted based on a central composite design. The adaptive neural fuzzy model was adopted to establish the relationship between liquid fuel production and operating conditions. The R-squared value of the experimental and adaptive neural fuzzy model predicted that liquid fuel production was 0.9934. Four additional experimental results verified the adaptive neural fuzzy model's applicability. Subsequently, the genetic algorithm (GA) was adopted to optimize operating conditions to maximize liquid fuel production. The GA optimized operating conditions (temperature, residence time, and carrier gas flow rate) were: 488 °C, 20 min, and 20 mL/min. The liquid fuel under the optimal operating conditions was analyzed by Fourier-transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC–MS). The liquid fuel had similar main functional groups as diesel. The components of the liquid fuel were mainly 1-alkenes and n-alkanes ranging from C7 to C36. The effects of operating conditions on liquid fuel fractions and mean molecular weight were also investigated.

Pyrolysis of waste polyethylene under vacuum using zinc oxide

ABSTRACT Innovative approaches in pyrolysis process to recover energy from plastic wastes in a sustainable manner are being explored progressively. Present study reports the effect of vacuum on pyrolysis of polyethylene waste in the presence of zinc oxide as a catalyst. Firstly, the effect of vacuum on the pyrolysis of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) wastes was investigated by conducting the pyrolysis at various applied vacuums of 101.325 kPa, 88 kPa, 73 kPa, 60 kPa, and 47 kPa in the absence of catalyst. Vacuum was observed to have positive effect on the pyrolysis in terms of increase in the yield of liquid product. Further, the effect of zinc oxide on the pyrolysis was studied by performing the pyrolysis at various catalyst feed ratios of 3:100, 5:100, 10:100 and 15:100 under the applied vacuum of 50 kPa. The maximum yield of liquid product obtained was 74.58% and 78.65% for the waste LDPE and HDPE, respectively, for the catalyst feed ratio of 15:100 and at applied vacuum of 50 kPa. GC-MS analysis of the liquid products demonstrated that the major fraction of hydrocarbons present is in a sufficiently narrow range. The fuel properties of the obtained liquid product were also determined.

Petrochemical feedstock from pyrolysis of waste polyethylene and polypropylene using different catalysts

In this work, thermal and catalytic pyrolysis of urban plastic waste composed of a mixture of polyethylene (PE) and polypropylene (PP) was studied. The catalysts investigated were HZSM-5, USY, NH4ZSM-5 (ZSM-5 in ammonium form), and their corresponding alkaline-treated (BHZSM-5, BUSY, and BNH4ZSM-5) or acid-leached (LHZSM-5, LUSY, and LNH4ZSM-5) forms. The catalytic pyrolysis using BHZSM-5 (ZSM-5 in alkaline form), USY, BUSY, and NH4ZSM-5 resulted in higher amounts of liquid fraction, which was composed of alkylbenzenes, naphthalenes, and olefins. Acid leaching of zeolite NH4ZSM-5 increased both the specific area and the mesopore volume, allowing an increase in the liquid and gas fractions, and a reduction in the solid fraction. BHZSM-5 zeolite showed the best catalytic performance for the production of a high amount of liquid fraction, which was virtually composed of olefinic hydrocarbons without the formation of solid products. Moreover, BNH4ZSM-5 zeolite (alkaline-treated NH4ZSM-5) was a good pyrolysis catalyst also due to its high specific area and pore volume, resulting in higher gas formation in comparison with the liquid fraction (composed mostly of alkylbenzenes), and almost no solid fraction.

Investigation into the Catalytic Activity of Microporous and Mesoporous Catalysts in the Pyrolysis of Waste Polyethylene and Polypropylene Mixture

Catalytic pyrolysis behavior of synthesized microporous catalysts (conventional Zeolite Socony Mobil–5 (C-ZSM-5), highly uniform nanocrystalline ZSM-5 (HUN-ZSM-5) and β-zeolite), Mesoporous catalysts (highly hydrothermally stable Al-MCM-41 with accessible void defects (Al-MCM-41(hhs)), Kanemite-derived folded silica (KFS-16B) and well-ordered Al-SBA-15 (Al-SBA-15(wo)) were studied with waste polyethylene (PE) and polypropylene (PP) mixture which are the main constituents in municipal solid waste. All the catalysts were characterized by Brunauer-Emmett-Teller (BET), X-ray powder diffraction (XRD), and NH3-temperature programmed desorption (TPD). The results demonstrated that microporous catalysts exhibited high yields of gas products and high selectivity for aromatics and alkene, whereas the mesoporous catalysts showed high yields of liquid products with considerable amounts of aliphatic compounds. The differences between the microporous and mesoporous catalysts could be attributed to their characteristic acidic and textural properties. A significant amount of C2–C4 gases were produced from both types of catalysts. The composition of the liquid and gas products from catalytic pyrolysis is similar to petroleum-derived fuels. In other words, products of catalytic pyrolysis of plastic waste can be potential alternatives to the petroleum-derived fuels.

Thermo-Catalytic Pyrolysis of Waste Plastics from End of Life Vehicle

Pyrolysis of waste plastics is widely used recycling method. Owing to the end-of-life vehicles regulations, 95% of passenger cars and vehicles must reused/recovered after the dismantling. Pyrolysis of waste polyethylene and polypropylene obtained from end-of-life vehicles was investigated in a continuously stirred batch reactor using 500 and 600°C temperatures. To ensure the pyrolysis reactions the tested catalysts (5% of ZSM-5, HZSM-5, Ni-ZSM-5 and Fe-ZSM-5) were added directly to the mixtures of raw materials. Products of pyrolysis were separated into gases, pyrolysis oil and heavy oil, which was further analyzed by gas-chromatography, Fourier transformed infrared spectroscopy and other standardized methods. Based on the results it was concluded, that the catalysts significantly increase the yields of volatile products, and modify their composition. Especially the alkane/alkene ratio, the methane concentration and the concentration of branched hydrocarbon could be affected by the applied catalysts. Ni-ZSM-5 catalyst had the highest activity in methane production, while HZSM-5 catalyst proved effective in isomerization reactions. Using H-ZSM-5, Ni-ZSM-5, and Fe-ZSM-5 catalyst notably decreased average molecular weight of pyrolysis oils and significantly higher aromatic content was observed.

A process study on the pyrolysis of waste polyethylene

The thermo-catalytic cracking of waste polyethylene bottles was thoroughly examined to determine the possibility of operating the process in continuous mode. Two types of zeolite catalysts renowned for their strong catalytic properties and precise selectivity, HUSY and HBeta, were used to study the slates and yields of the products generated under various operating conditions. The liquid and gas samples were analyzed via GC–MS to determine the hydrocarbons chain distribution in terms of paraffins, olefins and aromatics. Under thermal heating, the gas yield reached 17.8% in the absence of catalysts and it increased to 93–96% when HUSY and HBeta were used in vapor contact mode. This yield dropped to 57% when energy-efficient induction heating was applied. Under hydrogen cracking, the gas yield decreased further to 51.6% while the P/O ratio increased due to a rise in the C13–C23+ paraffin contents. The catalyst deactivation stage showed that both HUSY and HBeta started to lose their activity as waste HDPE charges were continuously fed to the reactor. After the third HDPE charge, the amount of solid and liquid wax products dramatically increased and the process started to resemble to thermal pyrolysis. High gas yields of greater than 90% were achieved when the catalysts were regenerated with industrial air at 550°C, indicating full catalyst recovery.

Test to screen catalysts for reforming heavy oil from waste plastics

A method which combines pyrolysis and catalytic reforming is a more efficient and pollution-free recovery method for processing large amounts of waste plastics than a combustion-based process. Several solid acid catalysts such as HY, rare earth metal-exchanged Y-type (REY), and HZSM-5 zeolites and silica-alumina (SA) were used for catalytic reforming of heavy oil produced by pyrolysis of waste polyethylene, to yield gasoline. REY zeolite was found to be the most suitable catalyst for the reaction having the highest research octane number (RON) of 67 and a gasoline yield of 48 wt.-%. In contrast, high siliceous and ordinary HZSM-5 zeolites have the lowest RON value (23) and gasoline yield (18 wt.-%), respectively.