Pyrolysis Of High Density Polyethylene Research Articles

Oxidative Fast Pyrolysis of High-Density Polyethylene on a Spent Fluid Catalytic Cracking Catalyst in a Fountain Confined Conical Spouted Bed Reactor.

The oxidative fast pyrolysis of plastics was studied in a conical spouted bed reactor with a fountain confiner and draft tube. An inexpensive fluid catalytic cracking (FCC) spent catalyst was proposed for in situ catalytic cracking in order to narrow the product distribution obtained in thermal pyrolysis. Suitable equivalence ratio (ER) values required to attain autothermal operation were assessed in this study, i.e., 0.0, 0.1, and 0.2. The experiments were carried out in continuous regime at 550 °C and using a space-time of 15 gcatalyst min gHDPE -1. The influence of an oxygen presence in the pyrolysis reactor was analyzed in detail, with special focus on product yields and their compositions. Operation under oxidative pyrolysis conditions remarkably improved the FCC catalyst performance, as it enhanced the production of gaseous products, especially light olefins, whose yields increased from 18% under conventional pyrolysis (ER = 0) to 30% under oxidative conditions (ER = 0.1 and 0.2). Thus, conventional catalytic pyrolysis led mainly to the gasoline fraction, whereas light olefins were the prevailing products in oxidative pyrolysis. Moreover, the oxygen presence in the pyrolysis reactor contributed to reducing the heavy oil fraction yield by 46%. The proposed strategy is of great relevance for the development of this process, given that, on one hand, oxygen cofeeding allows solving the heat supply to the reactor, and on the other hand, product distribution and reactor throughput are improved.

Plastic pyrolysis over HZSM-5 zeolite and fluid catalytic cracking catalyst under ultra-fast heating

Plastic pollution compromises the environment and human well-being, and a global transition to a circular economy of plastics is vital to address this challenge. Pyrolysis is a key technology for the end-of-life recycling of plastics, although high energy consumption limits the economic feasibility of the process. Various research has shown that the application of induction heating in biomass pyrolysis reduces energy consumption when compared to conventional heating. Nevertheless, the potential of induction heating in plastic pyrolysis is rarely explored. This paper presents an exploratory study on the thermal and catalytic pyrolysis of high-density polyethylene, low-density polyethylene, and polypropylene in a fixed bed reactor through induction heating. An MFI-type HZSM-5 zeolite (SiO2/Al2O3 = 23) and an FAU-type spent fluid catalytic cracking (FCC) catalyst with distinctive Brønsted acidity and textural properties were used. A complete conversion of the plastic feedstocks was achieved within 10 min, even without a catalyst. Thermal pyrolysis produced wax (72.4–73.9 wt%) and gas products, indicating a limited degree of polymer cracking. Catalytic pyrolysis over HZSM-5 and FCC catalyst significantly improved polymer cracking, leading to higher gas (up to 75.2 wt%) and liquid product (up to 35.9 wt%) yields at the expense of wax yield (up to 25.4 wt%). In general, the gas products were rich in C3 and C4 compounds. The liquid product composition was highly dependent on the catalyst properties, for example, the HZSM-5 produced high aromatics, while the FCC catalyst produced high alkenes in the liquid products. The catalyst acidity and textural properties played an essential role in plastic pyrolysis within the short reaction time. This study demonstrated the feasibility of a fast, energy-efficient, and versatile plastic valorization technology based on the application of induction heating, where the plastic feed can be converted into wax, gas, and liquid products depending on the end-use applications.

Automobile fuels (diesel and petrol) from plastic pyrolysis oil—Production and characterisation

Plastics like high-density polyethylene (HDPE), polystyrene (PS), and Polypropylene (PP) constitute a large portion of municipal solid waste. Plastics can be pyrolysed for reuse, but the end-product qualities are critical to industry refining processes. Pilot-scale pyrolysis and vacuum distillation were used to thermally degrade the plastics and convert it to petrol (gasoline) and diesel. Batch pyrolysis of HDPE, PS, and PP at 540 oC yielded plastic pyrolysis crude oils. The crude oil was separated into different fractions starting with distillation temperatures of less than 170 OC, 170 to 380 °C, and above 380 °C. The quality of the produced crude oil, gasoline, and diesel cuts was evaluated analytically according to the fuel specifications. This study demonstrated that pyrolysis of plastics can convert up to 80% of solids by weight) into liquid crude oil. HDPE pyrolysis produces lower quantities of oil due to the production of wax. A high calorific value (38.1 to 42.9 MJ/kg) similar to fossil fuels indicates that the liquid product of plastic pyrolysis could be a viable energy source. Plastic pyrolysis crude oil from PS mostly yielded gasoline at around 70% by weight, while HDPE and PP yield predominantly diesel at more than 50% by weight. The distilled oil characterisation results were outstanding, confirming that the quality of produced petrol and diesel from plastics pyrolysis oil suppress minimum specifications for automotive fuel standards. The cetane index of HDPE and PP diesel was found to be 60 and 55 respectively, significantly above the required value of 46 for automotive diesel. Higher heating values of most petrol cuts were in the range of 41.1 to 44.6 MJ/kg. These and other fuel qualities are within or near the approved range for automotive fuel. Thus, the findings can be used to build a foundation for the industrial manufacture of automotive quality fuels from plastic solid waste.

Copper catalyzed co‐pyrolysis of polyethylene terephthalate with low and high density polyethylene for liquid fuel production

AbstractBACKGROUNDMunicipal waste contains low density polyethylene (LDPE), high density polyethylene (HDPE), and polyethylene terephthalate (PET) in enormous amount. As these plastics are non‐biodegradable and pose serious threats to the environment, efforts have been made towards their safe disposal with energy recovery and value added chemicals by subjecting them to heat under oxygen deficient conditions. This study deals with the co‐pyrolysis of the three types of waste polymers, with special focus on the conversion of PET into liquid fuel by its interaction with the other two polymers.ResultsThe individual pyrolysis of LDPE and HDPE produced pyrolysis oil, whereas PET produced only wax. The co‐pyrolysis of the three polymers with different mixing ratios showed that PET hindered oil formation and increasing its amount more than 20 wt% in the polymer mixture resulted in wax formation. The thermal process produced 8 wt% pyrolysis oil, 32.3 wt% wax, 39.7 wt% pyro‐gases and 20 wt% coke while the catalytic process with copper catalyst produced 32.5 wt% pyrolysis oil, 3 wt% wax, 46.5 wt% pyro‐gases, and 18 wt% coke under optimum conditions.ConclusionThe thermal pyrolysis oil contained long chain paraffins as major components, while short chain isoparaffin and naphthenes were predominant in the catalytic pyrolysis oil owing to which marked differences were observed in the physicochemical properties of both oils. The fractionally distilled fractions of catalytic pyrolysis oil in gasoline, kerosene, and diesel range showed profound similarities with standard fuels in terms of fuel properties particularly the gasoline range fraction. © 2022 Society of Chemical Industry (SCI).

Catalytic pyrolysis of high-density polyethylene over nickel-waste chicken eggshell/HZSM-5

The main objective of the current work is to investigate the effect of nickel–waste chicken eggshell modified Hydrogen exchanged Zeolite Socony Mobil-5 (Ni-WCE/HZSM-5) on pyrolysis of high-density polyethylene (HDPE). Ni-WCE/HZSM-5 was synthesized via the impregnation incipient wetness (IWI) method with Ni and WCE mass loading of 4 and 12 wt% respectively. HZSM-5, CaO, WCE, WCE/HZSM-5, and Ni/HZSM-5 were prepared for comparison purposes with Ni-WCE/HZSM-5. All the synthesized catalysts were characterized for phase analysis, metal loading, surface morphology, and textural properties. The impregnation of nickel and WCE had significantly affected the original framework of HZSM-5, where the crystallinity percentage and average crystal size of HZSM-5 dropped to 44.97% and increased to 47.90 nm respectively. The surface morphology of HZSM-5 has drastically changed from a cubic-like shape into a spider web-like surface after the impregnation of WCE. The BET surface area of HZSM-5 has been lowered due to the impregnation of nickel and WCE, but the total pore volume has increased greatly from 0.2291 cm3/g to 0.2621 cm3/g. The catalyst performance was investigated in the pyrolysis of HDPE via a fixed bed reactor and the pyrolysis oil was further analysed to evaluate the distribution of C6 to C9> hydrocarbons. Among the tested catalytic samples, the highest pyrolysis oil yield was achieved by WCE (80%) followed by CaO (78%), WCE/HZSM-5 (63%), HZSM-5 (61%), Ni/HZSM-5 (44%) and Ni-WCE/HZSM-5 (50%). For hydrocarbon distribution in pyrolysis oil, the Ni/HZSM-5 produced the highest of total C6 and C7 hydrocarbons at 12% and 27% respectively followed by WCE/HZSM-5 (4% and 20%), non-catalytic (5% and 13%), Ni-WCE/HZSM-5 (0% and 15%), WCE (0% and 10%), HZSM-5 (0% and 6%) and CaO (0% and 0%).

Analysis of Statistically Predicted Rate Constants for Pyrolysis of High-Density Plastic Using R Software.

The surge in plastic waste production has forced researchers to work on practically feasible recovery processes. Pyrolysis is a promising and intriguing option for the recycling of plastic waste. Developing a model that simulates the pyrolysis of high-density polyethylene (HDPE) as the most common polymer is important in determining the impact of operational parameters on system behavior. The type and amount of primary products of pyrolysis, such as oil, gas, and waxes, can be predicted statistically using a multiple linear regression model (MLRM) in R software. To the best of our knowledge, the statistical estimation of kinetic rate constants for pyrolysis of high-density plastic through MLRM analysis using R software has never been reported in the literature. In this study, the temperature-dependent rate constants were fixed experimentally at 420 °C. The rate constants with differences of 0.02, 0.03, and 0.04 from empirically set values were analyzed for pyrolysis of HDPE using MLRM in R software. The added variable plots, scatter plots, and 3D plots demonstrated a good correlation between the dependent and predictor variables. The possible changes in the final products were also analyzed by applying a second-order differential equation solver (SODES) in MATLAB version R2020a. The outcomes of experimentally fixed-rate constants revealed an oil yield of 73% to 74%. The oil yield increased to 78% with a difference of 0.03 from the experimentally fixed rate constants, but light wax, heavy wax, and carbon black decreased. The increased oil and gas yield with reduced byproducts verifies the high significance of the conducted statistical analysis. The statistically predicted kinetic rate constants can be used to enhance the oil yield at an industrial scale.

Prediction of high-density polyethylene pyrolysis using kinetic parameters based on thermogravimetric and artificial neural networks

Prediction of high-density polyethylene pyrolysis using kinetic parameters based on thermogravimetric and artificial neural networks

Thermochemical recycling of end-of-life and virgin HDPE: A pilot-scale study

Industrial-scale application of end-of-life plastic pyrolysis still faces significant problems, such as a lack of detailed knowledge on degradation mechanisms, parameters affecting the degradation, and formation pathways of the primary pyrolysis products. Today, the degradation mechanisms based on radical chain scission are insufficiently understood to explain the pyrolysis chemistry from feedstock-to-product comprehensively. In this study, the impact of operating conditions on the degradation mechanism is evaluated by pyrolyzing end-of-life and virgin high-density polyethylene (HDPE) in a continuous pilot-scale unit at temperature and pressure ranges of 450–504 ºC and 0.1–2 bara. The pyrolysis products were analyzed based on the detailed product composition obtained using comprehensive two-dimensional gas chromatography (GC×GC). A simplified kinetic mechanism was proposed to describe the main production pathways of the various components by considering the weakest points along the polymer chain. The results showed that the chain-end scission mechanism is the main mechanism in the HDPE pyrolysis process, even at low temperatures and pressures in the studied ranges. The pyrolysis of virgin HDPE under sub-atmospheric pressure, 0.1 bara, at 464 ºC reactor temperature, yields the highest concentration of linear hydrocarbons in the pyrolysis oil (93.2 wt%). At higher pressure and temperature, the cyclic and branched hydrocarbons had a higher share of up to 17.4 wt% compared to 6.8 wt% at vacuum pressure and lower temperature. Interestingly, the pyrolysis of end-of-life HDPE at atmospheric pressure and 450 ºC led to more cyclic and branched hydrocarbons (sum: 22.1 wt%), as opposed to that of virgin HDPE which is more prone to the production of linear hydrocarbons at the studied conditions. Regarding the additives and contaminants, a large amount of different metals and halogen atoms in the ppm range were detected in end-of-life HDPE, of which a small amount was still found in the pyrolysis oil.

Liquid-fed waste plastic pyrolysis pilot plant: Effect of reactor volume on product yields

A unique waste plastic pyrolysis pilot plant was used for fast pyrolysis (1–5 s vapor residence time) of HDPE at 600 °C. A dissolution pre-treatment step dissolved the high-density polyethylene (HDPE) in recycled pyrolysis wax to create a liquid feed to the pyrolysis reactor, avoiding clogging and bridging of the plastic particles that is common in alternative feeding strategies. Three different reactor volumes were tested to determine the effect of residence time on product distribution. Pyrolysis products were cooled through a series of two condenser to separate the products into three groups: a heavy, waxy product (> C15), a lighter liquid product (C6-C15), and a gaseous product (C1-C6). GC/MS analysis was used to characterize the composition of each product. Multiphysics modeling was conducted to estimate the residence time in the reactor and compare the pilot plant results to previously published micropyrolysis research. It was found that residence time had a significant effect on product distribution, with an increase from 1 to 4.5 s of residence time causing a 9 wt% drop in wax (C20-C30) production and a 11 wt% increase in light oil (C5-C10) production. The trends for product distribution as a function of residence time were found to be consistent between both the pilot plant and micropyrolysis systems, demonstrating that the pilot plant system can be “tuned” to produce the desired pyrolysis product.

Catalytic pyrolysis of HDPE over WOx/Al2O3: Effect of tungsten content on the acidity and catalytic performance

A series of WOx/Al2O3 catalysts with different tungsten contents were prepared by an incipient-wetness impregnation method for use in the pyrolysis of high density polyethylene (HDPE) to liquid oil. Physicochemical properties of the catalysts were investigated by N2 physisorption, field emission-scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy analyses. Acid properties of the catalysts were examined by FT-IR analyses of pyridine-adsorbed catalysts and NH3-TPD (temperature programmed desorption) experiments to elucidate the catalytic performance. The catalytic pyrolysis of HDPE was carried out over WOx/Al2O3 catalysts in a batch-type pyrex reactor at atmospheric pressure. It was found that HDPE conversion and oil yield showed volcano-shaped trends with respect to the tungsten content of the WOx/Al2O3 catalysts. Among the catalysts tested, the 6.25 wt% WOx/Al2O3 catalyst with the largest acidity showed the best catalytic performance. A correlation between the catalytic performance (HDPE conversion and oil yield) and acidity showed that the catalytic performance increased with the increasing acidity of the catalyst.

Energy recovery of waste plastics into diesel fuel with ethanol and ethoxy ethyl acetate additives on circular economy strategy

The widespread use of plastic goods creates huge disposal issues and environmental concerns. Increasing emphasis has been paid to the notion of a circular economy, which might have a significant impact on the demand for plastic raw materials. Post-consumer plastics recycling is a major focus of the nation’s circular economy. This study focuses on energy recovery from waste plastics as an alternative fuel source to meet the circular economy demand. Waste plastic fuel produced through pyrolysis has been claimed to be utilized as a substituted fuel. This work focuses to determine the performance and emission standards of Waste Plastic Fuel (WPF) generated from the pyrolysis of High-Density Polyethylene (HDPE) in a single-cylinder Direct Injection Diesel Engine (DIDE). Three different ratios of WPF were combined with 10% ethanol and 10% ethoxy ethyl acetate as an oxygenated additive to create quaternary fuel blends. The ethanol has a low viscosity, a high oxygen content, a high hydrogen-to-carbon ratio as favourable properties, the quaternary fuel results the improved brake thermal efficiency, fuel consumption and reduced emissions. The blend WEE20 exhibits 4.7% higher brake thermal efficiency, and 7.8% reduced fuel consumption compared to the diesel. The quaternary fuel blends demonstrated decreased carbon monoxide of 3.7 to 13.4% and reduced hydrocarbons of 2 to 16% under different load conditions.

Energy recovery from high density polyethylene plastic via pyrolysis with upgrading of the product by a novel nano MIL-53 (Cu) derived@Y zeolite catalyst using response surface methodology

Pyrolysis of plastics is an economical method to recover valuable fuels from waste sources. In this study, the response surface methodology is adopted to model the behavior for the pyrolysis of high-density polyethylene (HDPE). The three operating parameters of temperature in the range of 415 to 585 ° C, feed density in a window between 959 and 967 kg/m3 and reactor loading range from 23 to 57% were selected as the main variables. Using the thermogravimetric analysis (TGA) study for different heat transfer rates, the range at which the feed is fully converted was determined, thus ensuring that the correct operating temperature range was selected. By drawing difference thermogravimetry (DTG) curves and using a dynamic model, the activation energy for converting heavy and light feeds was determined to be 300.984 and 273.57 kJ/mol, respectively. Analysis of the experimental results using the (Central Composite Design) CCD method shows the ease of pyrolysis of light feed, which is agreed upon with less activation energy. As the main goal of this study, the effect of parameters on the liquid fuel production was investigated, and it was turned out that under optimum conditions, the amount of liquid fuel production will be 95.3%. For the optimal conditions, a temperature of 500 ° C, feed density is 963 kg/m3 and reactor loading rate of 40% were determined. Analysis of the exhaust gases also showed that propylene and ethane are the most abundant components of this phase. Furthermore, with the help of analysis of variance, the proposed model to produce liquid fuel and gas yield was evaluated as a significant and the accurate model. Finally, under the optimized conditions, by using a new MIL-53 (Cu) derived @ Zeolite Y catalyst, the percentage of heavy compounds in the fuel was meaningfully reduced, and at the same time, the octane number of the gasoline produced was considerably improved. Based on the energy considerations, it was calculated that the recovery of energy from combustion as well as the sensible energy of the exhaust gases from the reactor, leads to significant savings in total energy consumption to produce each gram of liquid fuel.

Investigation on the co-pyrolysis of agricultural waste and high-density polyethylene using TG-FTIR and artificial neural network modelling

To realize utilization of agricultural and plastic waste to alleviate environmental pollution, the individual pyrolysis and co-pyrolysis characteristics of kidney beans stalk (KS) and high-density polyethylene (HDPE) were investigated. Thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR) was used to investigate the pyrolysis behaviour, synergistic effect, kinetics and gaseous product evolution of different samples. In addition, an artificial neural network (ANN) model was established to predict the mass change with temperature during sample pyrolysis or co-pyrolysis. The results showed that the decomposition of HDPE was easier than that of KS, and synergistic and inhibitive effects occurred during co-pyrolysis. The synergistic or inhibitive effect was most significant from 470 to 510 ℃. The FTIR analysis results showed that gaseous products of KS pyrolysis were mainly oxygen-containing compounds including CO2, CO, ketones, aldehydes, esters, etc., while those of HDPE pyrolysis were mainly hydrocarbons including alkanes, alkenes, aromatic rings, etc. The co-pyrolysis of samples with different proportions promoted or inhibited the production of some gaseous products to different degrees. Moreover, the activation energy of the two stages during co-pyrolysis was lower than that of the pure sample. The established ANN model can effectively predict the mass loss of a sample with temperature.

Cracking of plastic pyrolysis oil over FCC equilibrium catalysts to produce fuels: Kinetic modeling

The kinetics of the catalytic cracking of plastic pyrolysis oil (PPO) over three FCC (fluid catalytic cracking) equilibrium commercial catalysts has been modeled. The PPO comes from the fast pyrolysis of high-density polyethylene (HDPE). The cracking runs have been carried out in a laboratory-scale reactor under FCC conditions: 500–560 °C; catalyst/oil weight ratio of 5 gcat gPPO-1; and contact time of 1.5–6 s. Four different reaction schemes composed of six lumps have been compared and it has been obtained by statistical means that the simplest one is the most appropriate for describing the process. The differences in the kinetic parameters have been related to the properties of the catalysts. Among them, total acidity and mesoporous structure have a key role. The former for promoting the cracking reactions and the latter for limiting the diffusional restrictions of both the bulky compounds within the PPO and the formed coke precursors. This way, ECAT-3 that is the most acid and most mesoporous catalyst, maximizes the yields of naphtha (33.6 wt%) and liquefied petroleum gases (LPG) (18.9 wt%). In contrast, ECAT-1 and ECAT-2 should be chosen for producing light cycle oil (LCO). For ECAT-3, the apparent activation energies of the conversion of heavy cycle oil (HCO) into light cycle oil (LCO), LCO into naphtha, and LCO into LPG are 60.5 42.5 and 58.3 kJ mol-1, respectively. In addition, those of the formation of coke from HCO, LPG and dry gas are 129.0, 4.4 and 40.7 kJ mol-1, respectively.

Pyrolysis-Aided Microbial Biodegradation of High-Density Polyethylene Plastic by Environmental Inocula Enrichment Cultures

Polyethylene plastics are a major source of industrial and household wastes, the majority of which end up in the environment or in landfills. These wastes pose challenges for microbial biodegradation due to their polymeric structure. There is a critical need for a process that aids in the breakdown and reuse of plastic compounds. Pyrolysis of high-density polyethylene (HDPE) has previously been used to induce chemical changes in plastic compounds, resulting in more structurally simplistic compounds. Here, we demonstrate the ability of pyrolysis to produce microbially biodegradable intermediate compounds. Biodegradation of pyrolysis-treated plastics has not previously been demonstrated. We found that enrichment cultures derived from six different environmental inocula were able to achieve extensive biodegradation of polyethylene pyrolysis products over the course of 5 days. We verified the biodegradation by quantifying residual compound concentrations of alkenes using gas chromatography/mass spectrometry (GC/MS). 16S rRNA gene amplicon sequencing results demonstrated that the most dominant taxa in the microbial community belonged to the phylum Proteobacteria. Many organisms in this phylum have previously been shown to metabolize hydrocarbons. Our results indicate that the coupling of chemical and biological processes can speed up the breakdown and conversion of polyethylene to bacterial biomass by microbial consortia.

Catalytic Pyrolysis of High-Density Polyethylene: Decomposition Efficiency and Kinetics

Organic waste is generally characterized by high volume-to-weight ratios, requiring implementation of waste minimization processes. In the present study, the decomposition of high-density polyethylene (HDPE), was studied under thermal and catalytic pyrolysis conditions on two experimental systems. Firstly, pyrolytic conditions for HDPE decomposition were optimized in a laboratory-scale batch reactor. In order to maximize gas yields and minimize secondary waste, the effects of aluminosilicate catalysts, catalyst loading, and reaction temperature on decomposition efficiency were examined. Secondly, kinetics and reaction temperatures were studied on a large capacity thermobalance, especially adjusted to perform experiments under pyrolytic conditions at a larger scale (up to 20 g). The addition of catalysts was shown to enhance polymer decomposition, demonstrated by higher gas conversions. Condensable yields could be further minimized by increasing the catalyst to polymer ratio from 0.1 to 0.2. The most prominent reduction in pyrolysis temperature was obtained over ZSM-5 catalysts with low Si/Al ratios; however, this impact was accompanied by a slower reaction rate. Of the zeolites tested, the ZSM-5 catalyst with a Si/Al of 25 was found to be the most efficient catalyst for waste minimization and organic destruction, leading to high gas conversions (~90 wt%.) and a 30-fold reduction in solid waste mass.

Pyrolysis of High-Density Polyethylene in a Fluidized Bed Reactor: Pyro-Wax and Gas Analysis

Pyrolysis of High-Density Polyethylene in a Fluidized Bed Reactor: Pyro-Wax and Gas Analysis

Kinetic study of pyrolysis of high‐density polyethylene (HDPE) waste at different bed thickness in a fixed bed reactor

AbstractThe aim of this study is to investigate the kinetic characteristics of the high‐density polyethylene (HDPE) waste pyrolysis process based on thermogravimetric analysis (TGA) and using a fixed bed pyrolytic reactor (FBPR) at different temperatures. In addition, the influence of material bed thickness on the yield distribution and the composition of products was examined over a temperature range of 425–550°C. A higher wax fraction was obtained in the thin bed of the FBPR bed at 425°C. With temperature above 500°C, more oil and wax products were generated in the thick bed of the FBPR. Based on the experimental study, a discrete first‐order kinetic lumping model, comprising three independent parallel reactions (lumps), was developed to describe the yield distribution of gases, oil fractions, wax fractions, and solid residue, coupling with secondary cracking reactions of the wax fractions into lighter fractions (i.e., oil and gas). The overall apparent activation energy (Ea) and pre‐exponential factor (A0) of HDPE pyrolysis were estimated in the FBPR. The results showed that the thickness of the bed of plastics has a pronounced influence on the pyrolysis kinetics of HDPE.

Catalytic pyrolysis of recycled HDPE, LDPE, and PP

Plastic waste has been growing every year, and as a result, environmental concern has been a topic of much attention. Many properties of plastics, such as their lightweight, durability, and versatility, are significant factors in achieving sustainable development. The exponential increase of plastic production produces every year approximately 100 million tons of waste plastic, which could be converted into hydrocarbon fuels by employing a process appropriately called pyrolysis. Pyrolysis, which is thermal or catalytical, can be performed under different experimental conditions that affect the type and amount of product obtained. With the pyrolysis process, products can be obtained with high added value, such as fuel oils and feedstock for new products. In this study, magnesium silicate (MgO3Si) and Cloisite 30B were used as catalysts for the decomposition of different plastics, and the results were compared with the zeolite catalyst. In the case of high-density polyethylene (HDPE), the oil yield with a zeolite catalyst was found to be 71%, whereas with MgO3Si and Cloisite 30B, this was 68% and 67%, respectively. Zeolite produced better results in the decomposition of polypropylene (PP) compared to MgO3Si and Cloisite 30B. Fourier-transform infrared spectroscopy (FTIR), and gas chromatography (GC) were conducted in this work. The spectra results for all samples were consistent and in the fuel range.

Modelling pyrolysis process for PP and HDPE inside thermogravimetric analyzer coupled with differential scanning calorimeter

Plastic pyrolysis is widely studied and implemented at lab-scale but rarely modelled numerically. For the sake of designing efficient industrial reactors, modelling plastic pyrolysis process at particle scale could be a prerequisite. Therefore, the aim of this work is to model the whole plastic pyrolysis process, on particle scale, for polypropylene (PP) and high density polyethylene (HDPE) inside a thermogravimetric analyzer coupled with differential scanning calorimeter (TGA-DSC). First, the kinetic triplet for PP and HDPE pyrolysis, at heating rates 4-10°C/min, are determined according to the isoconversional methods. Secondly, the kinetic triplets are used along with the appropriate conditions to model and simulate the pyrolysis process for PP and HDPE in TG analyzer, using finite element method. The melting sub-process is modelled using the modified apparent heat capacity method, which resulted in a relative error below 10% between the simulated and measured heat flow. Furthermore, the cracking model describes perfectly PP and HDPE cracking, where the average relative error among all calculated and experimental conversions didn't exceed 5%. Furthermore, the heat flow inside the TGA-DSC crucible was modelled and the average error was reduced to less than 8% by dividing the cracking phenomena into a “latent” and an apparent process.