Pyrolysis Of High Density Polyethylene Research Articles

Fractional distillation of waste plastic pyrolysis oil for isolating narrow hydrocarbons cuts

Pyrolysis of polyolefins generates a large amount of olefins, which can serve as a valuable feedstock for the synthesis of chemicals. Nevertheless, their effective utilization requires refining owing to their diverse carbon distribution. This study performed a comprehensive GC×GC analysis of pyrolysis oils derived from waste polypropylene (PP) and waste high-density polyethylene (HDPE). The chemical composition of PP pyrolysis oil exhibited a high content of iso-olefins, whereas HDPE pyrolysis oil contained mainly alpha-olefins. Experimental batch distillation of PP pyrolysis oil yielded narrow hydrocarbon cuts with iso-olefins content exceeding 70 wt%. In contrast, distillation of HDPE resulted in cuts with more than 25 wt% alpha-olefins content. To perform ASPEN simulations, the physical properties (density, viscosity) of the oil were determined, two ways for obtaining boiling curves (ASTM D2887 and ASTM D86) were compared and two property methods (Peng-Robinson and Soave-Redlich-Kwong) were compared. It was concluded that the ASTM D2887 boiling curve and the Peng-Robinson property method present better experimental agreement for pyrolysis oils using the Theil’s Inequality Coefficients test. Based on the validated batch simulation, continuous distillation process schemes for isolating narrow carbon cuts in the refinery atmospheric tower indicate that a side draw configuration provides a better yield of (19.1 wt%) compared to a dedicated separate distillation column of (11.9 wt%) for the same number of trays, while the dedicated column allows the possibility to achieve higher purity.

Pyrolytic Decomposition of Polyethylene in the Presence of Aluminosilicate Materials Containing Nickel Oxide

The work is devoted to the study of the pyrolysis of high-density polyethylene (PE) in the presence of aluminosilicate materials containing nickel oxide. The process of catalytic pyrolysis of plastics makes it possible to convert polymers into chemical compounds, which can later be used as an additional source of fuels, raw materials for the chemical industry or polymer production. The physicochemical parameters of materials containing nickel oxide have been established using the following methods: IR-Fourier spectroscopy; x-ray diffraction analysis; N2 physical adsorption method; thermogravimetric analysis; pyrolytic gas chromatography. The dependences of the chemical composition of PE pyrolysis products on the type of support used and the presence of nickel oxide. The presence of nickel oxide in the studied aluminosilicates increases the Lewis acidity, which increases the content of aromatic compounds in the pyrolysis products. The activation energy of the PE pyrolysis process in the presence of MCM-41 containing nickel oxide was calculated from experimental data.

Pyrolysis of high-density polyethylene: Degradation behaviors, kinetics, and product characteristics

Pyrolysis is a promising technology for converting plastic waste into valuable raw materials while offering a potential solution to the global plastic pollution crisis. In this study, the thermal pyrolysis of high-density polyethylene (HDPE) is investigated in a drop tube reactor under nearly isothermal conditions. The impact of reaction temperature and gas/volatile residence time on carbon conversion and product distribution is examined across a range of 500–900 °C and 3.6–32.2 s, respectively. Non-condensable gas products detected by online mass spectrometry are H2, CH4, C2H4, C2H6, C3H6, and C3H8. At elevated temperatures and prolonged residence time, H2 yield reaches as high as 8.6 wt% of the initial HDPE mass due to intensified cracking reactions of C2–C3 hydrocarbons and long-chain aliphatic compounds. Consequently, pyrolysis tars consist mainly of polycyclic aromatic hydrocarbons (PAHs) with 5–7 rings, accompanied by visible coke deposition within the reactor. HDPE decomposition to volatiles is an endothermic process and it is complete at a temperature between 492 °C and 525 °C, depending on the heating rate employed, from non-isothermal thermogravimetric analysis and differential scanning calorimetry (TGA-DSC) measurements. The thermal degradation of HDPE pellets follows the two-dimensional nucleation growth model for conversion levels up to 0.8 with an apparent activation energy of 259–270 kJ/mol and a pre-exponential factor of 4.83 × 1017–1.37 × 1019 min−1, determined from various isoconversional methods such as Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), and Starink, along with Criado's master plots. These findings provide valuable insights into optimizing process parameters and refining reactor design for pyrolysis, which can be integrated with gasification and reforming processes to enhance hydrogen production on a larger scale.

Catalytic upgrading of polyethylene plastic waste using GMOF catalyst: Morphology, pyrolysis, and product analysis

Since 2000, global plastic waste production and consumption have doubled, escalating from 250 to 500 million tonnes. Merely 9 % of plastic waste undergoes global recycling, leaving the majority either in landfills or poorly managed. This research introduces a new catalyst, GMOF, created by growing Metal-Organic Framework (MOFs) rods on the flaked, carpet-like structure of Graphene Oxide (GO) nanosheets. The aim is to enhance the quality of pyrolysis products derived from high-density polyethylene (HDPE) and low-density polyethylene (LDPE) waste using this GMOF catalyst. HDPE and LDPE, sourced from post-consumer plastic packaging, underwent specific treatment involving cleaning, drying, and shredding. Morphological and property evaluations of GO nanosheets before and after MOF decoration employed techniques including Field-Emission Scanning Electron Microscopy (FE-SEM), Energy-Dispersive X-ray Spectroscopy (EDS), and Fourier Transform Infrared Spectroscopy (FTIR). Flash pyrolysis at 500 °C for 1 min using a sample-to-catalyst ratio of 4:1 in a Quartz Wool Matrix (QWM) reactor was conducted via a Thermogravimetric Analyzer (TGA) and Frontier LAB pyrolizers. Thermal stability and characteristics of feedstocks and catalysts were assessed using TGA. Gas Chromatography-Mass Spectrometry (GC–MS) analyzed and quantified pyrolysis product compounds, while a Micro GC Fusion system determined non-condensable pyrolyzate permanent gas distribution. Results showcased that the GMOF catalyst's unique morphology efficiently captured smaller radicals on its surface, providing increased surface area for effective radical–radical interactions during pyrolysis. In HDPE pyrolysis, the GMOF catalyst notably decreased selectivity of C21-C40 and C40 + wax fractions to 49.07 % and 7.73 %, respectively, while boosting C1-C20 olefin production by 2.54 %. Conversely, LDPE pyrolysis with the GMOF catalyst notably amplified the CO2 peak intensity by 3.17 %, signifying a gasification phase. Primary gases produced were C3 aliphatic hydrocarbons, propane, and propylene, yielding 79.46 % collectively.

Catalytic pyrolysis of high-density polyethylene (HDPE) over hierarchical ZSM-5 zeolites produced by microwave-assisted chelation-alkaline treatment

A new microwave (MW) assisted chelation-alkaline strategy was developed to produce hierarchical ZSM-5 zeolites (with external surface area of 203 m2/g) in minutes, leading to the formation of heterogeneous structure with a high-silica shell and aluminium-rich core (silicon-to-aluminium ratios of 49.2 and 37.6, respectively). The zeolites were assessed comparatively by catalytic pyrolysis of high-density polyethylene (HDPE). Compared to the mesoporous ZSM-5 zeolite prepared by the conventional alkaline treatment (via desilication by the NaOH aqueous solution), the hierarchical zeolite by the MW-assisted method showed comparable kinetics in catalytic pyrolysis of HDPE, but with the improved stability in the cyclic pyrolysis-regeneration tests. The improved stability could be due to the better-preserved structural integrity thanks to the relatively milder surface etching by the MW-assisted chelation dealumination method. In addition, compared to the parent ZSM-5, the product distribution of HDPE catalytic pyrolysis over the hierarchical ZSM-5 zeolite showed a higher portion of oil products (i.e., 12 wt% vs. 6.9 wt%) and an improved alkane-to-olefin ratio in the oil products (2.22 vs. 1.86, respectively) due to the reduced acidity and improved hydrogen transfer ability. The MW-assisted chelation-alkaline treatment could be a new strategy to regulate the trade-off between stability and activity of zeolites for catalytic applications.

Molecular-level kinetic modelling for the pyrolysis of high-density polyethylene in a two-stage process

A two-stage process has been developed for the pyrolysis of high-density polyethylene to obtain light olefins, where probable mechanisms for each stage pyrolysis were proposed in our previous study. This work aims to establish molecular-level kinetic models for the first-stage pyrolysis at a lower temperature and for the second-stage pyrolysis at a higher temperature, respectively, to predict the overall reaction performances in accordance to the role of detailed mechanisms. A structure-oriented lumping (SOL) method based molecular-level kinetic model can effectively describe the first-stage pyrolysis, while a detailed molecular-level kinetic model is developed for the second-stage pyrolysis to track the evolutions of all alkanes, olefins, and diolefins, with special focus on the formation of light olefins. The established separate models can achieve the automatic generation of complex reaction networks and present good agreement with experimental data obtained from the first- and second-stage. In addition, the first-stage model indicates that the random scission plays an important role in the pyrolysis process at lower temperatures, while the chain-end scission mechanism dominates the second-stage reaction to produce light olefins at higher temperatures. As a whole, the molecular-level modelling scheme behaves excellently at a wide range of temperature, which provides guidance for upgrading the pyrolysis process.

Comparative Analysis of Kerosene Grade Fuel from Pyrolysis of HDPE and LDPE Waste Plastics

To curb the menace of plastic waste and energy crisis, this study investigated the conversion of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) grades of plastics to kerosene. Plastics sourced from dumpsites within Port Harcourt metropolis in Rivers State, Nigeria were shredded and pyrolyzed (thermally degraded under inert condition at a temperature range of 350-400oC). The obtained hydrocarbon liquid was distilled using distillation column at a temperature range of 150-270oC and characterised to evaluate the physico-chemical parameters such as flash point, density, copper corrosion, and calorific value and compared against the acceptable standard. The result showed that these properties were within the permissible limit. However, the sulphur content and smoke point of HDPE and LDPE were above and below the limits, respectively. The GC-MS and GC-FID results of kerosene samples obtained from both grades of plastics indicates that the product comprised C9 to C17 grades.

Arduino Controlled Catalytic Pyrolysis of Plastic/Municipal Waste to Higher Hydrocarbons

Worldwide, the broad usage of plastic has resulted in the massive production of plastic pollution. In this work, it was demonstrated that municipal plastic waste could be converted into valuable liquid products. This study shows the catalytic and non-catalytic pyrolysis of low-density polyethylene (LDPE), polypropylene (PP), and high-density polyethylene (HDPE). Pyrolysis was carried out in the absence of Oxygen, and three types of fractions: gas, liquid, and solid residues were obtained. The proportions of liquid or gas residue depend on the operating conditions such as temperature and the type of catalyst. The product obtained was then characterized through ASTM D-97, ASTM D-86, ASTM D-4294, Cloud Point, Conradson Carbon Residue, FTIR Analysis, ASTM D-611, Density and Specific Gravity. The use of catalysts showed more quantity of lower boiling points products due to further cracking of carbon chains and pour points decrease was also observed generally with the use of catalyst specially by using bentonite. A decrease in Pour Point indicated a decrease in paraffin content, therefore, reducing wax content, and so it indicated better flow properties at lower temperatures. Pour point and viscosity observed were interconnected with each other, sample having high pour points had high viscosity, hence showing the flowing ability of the liquid. Also, the Sulphur contents of all the samples falling under Euro II and Euro II category. C-Stretching, C=Stretching and C-Bending bonds were noted using the FTIR analysis. One of the important purposes of this study was to convert the waxes obtained from thermal pyrolysis of HDPE and LDPE to higher chain hydrocarbons, which was achieved by using bentonite as the catalyst and also flowing properties of the liquid improved by using the catalyst. HDPE with bentonite gave the highest percent of liquid fuel (75.15%) obtained which in turn shows the best result obtained through all our experiments.

Artificial Neural Network based prediction of Specific Fuel Consumption in various Compression Ratio CI Engine Fueled with Various Plastic Composition Pyrolysis oil and Diesel

This study looks at the usage of Artificial Neural Network Modeling for predicting Specific Fuel Consumption for compression ignition engines running on Diesel, Low-Density Polyethylene Pyrolysis Oil (LDPE PO), High-Density Polyethylene Pyrolysis Oil (HDPE PO), and Polypropylene Pyrolysis Oil (PP PO). Using preliminary practical findings, The Model of ANN was built to estimate SFC by adjusting the parameters of the engine. SFC is anticipated by adjusting the parameters and utilizing the orthogonal array. The experiment is then carried out using an orthogonal array. The outcomes of experimental work are used to create an ANN model. In the case of a non-linear mapping between input & output, the classic back-propagation method and a multi-layer perception network are utilized. The values of Mean Square Error (MSE), Root Mean Square Error (RMSE), and Regression Coefficient (R2) for LM10TP architecture are 1.5143×10–06, 0.0012 & 1 in training & the validation values 1.2185×10–06, 0.0011 and 0.9999 respectively. It was discovered that neural networks are useful tools for prediction since they performed well in specific fuel consumption prediction in both training and validation.

Analysing the effects of process parameters on HDPE pyrolysis and in-line reforming

This study presents a comprehensive parametric investigation focusing on the pyrolysis and in-line reforming of High-Density Polyethylene (HDPE) at zero time on stream. The research explores the impact of varying operating parameters, specifically examining the effects of temperature, space time, and steam/plastic (S/P) ratio on conversion, hydrogen production, and product yields. The temperature was varied within the range of 600–750 °C, demonstrating notable influence on conversion efficiency and hydrogen production. Additionally, the effect of space-time (2.8–20.8 g catalyst min gHDPE−1) was thoroughly evaluated, revealing substantial improvements in both conversion and hydrogen yields. Moreover, the S/P ratio of 1 to 3 was investigated, showcasing significant enhancements in hydrogen and CO2 yields with increasing steam partial pressure. The study provides valuable insights into optimizing the process parameters for HDPE pyrolysis and in-line reforming, which are crucial for achieving efficient conversion and enhancing hydrogen production.

Aromatization of HDPE and PP over Ga-promoted zeolite: Effects of pretreatment and zeolite type

The effects of pretreatment and structure of zeolite on aromatization of high-density polyethylene (HDPE) and polypropylene (PP) over different Ga-promoted zeolites (HZSM-5, hierarchical HZSM-5, HY, Hβ, and USY) were investigated. Hydrogen reduction of Ga-promoted HZSM-5 resulted in a higher yield of alkenes during HDPE pyrolysis but did not lead to increased production of total aromatic hydrocarbons. The reduction and subsequent oxidation of Ga/Z5 led to the formation of GaO+ species with high dehydrogenation activity. This resulted in a remarkable 65% yield of aromatics, with a BTEX (benzene, toluene ethylbenzene and xylene) overall yield of 60% and a selectivity of 90% of the liquid product. Increasing the Ga loading decreased the BTEX yield due to pore blockage and a decrease in the amount of Brønsted acid sites. The BTEX yield over Ga-promoted zeolites was found to be strongly related to the pore size of the zeolite, whereas its yield over the parent zeolite was not strongly dependent on the pore size. Diffusion of the cracking intermediates was found to have a more significant impact on the aromatization of PP than HDPE. The highest BTEX yield for HDPE was achieved with Ga-promoted HZSM-5, while Ga-promoted hierarchical HZSM-5 exhibited the highest BTEX yield for PP. Furthermore, Ga(1)/Hβ-Redox demonstrated remarkable selectivity (90%) towards ethylene and propylene in the gas phase, surpassing other zeolites (37%-68%).

Thermogravimetric catalytic pyrolysis of high-density polyethylene over iron modified chicken eggshell wastes

Among the major concerns of our current world include the accumulation of plastic wastes and the exhaustion of petroleum resources. Efforts to resolve these issues have contributed to multiple research and alternatives to be explored. One of the attractive alternatives that have been approached is the pyrolysis of plastic wastes. The use of catalysts offers multiple advantages in pyrolysis and different types of catalysts have been investigated in recent years. The potential of discarded natural wastes is acknowledged and studies to use food waste as a catalyst are to be developed in this research. The main objective of this project is to investigate the pyrolysis of high-density polyethylene (HDPE) over iron (Fe) modified waste chicken eggshell (WCE) as the catalyst. The pyrolysis was conducted at a temperature of 30 – 700℃ via a Thermogravimetric analyzer (TGA). WCE was washed, dried, and calcined in the furnace at 900℃ for 4 h. Fe was loaded (5 wt%) on the calcined WCE via the incipient wetness impregnation (IWI) method. The catalyst to HDPE mass ratio was fixed at 1:1. For comparison purposes, the commercial calcium oxide (CaO), calcined WCE, and Hydrogen exchanged Zeolite Socony Mobil − 5 (HZSM-5) were utilised in the pyrolysis of HDPE. Catalytic pyrolysis of HDPE over WCE and CaO had almost completely degraded with mass loss of 99.50% and 99.83% respectively at Phase II followed by pyrolysis of HDPE (94.05%), HZSM-5 (77.50%) and Fe/WCE (31.40%) samples. Among tested catalytic samples, the WCE catalyst works best to degrade HDPE into the highest volatile matter which attributes to higher pyrolysis oil yield.

Catalytic pyrolysis of high-density polyethylene for the production of carbon nanomaterials: effect of pyrolysis temperature

Catalytic pyrolysis of high-density polyethylene for the production of carbon nanomaterials: effect of pyrolysis temperature

Chemical Recycling of Polyolefins with the Molten Metal Reactor at 460 °C

AbstractThis paper describes the pyrolysis of high‐density polyethylene (HDPE) in a molten metal reactor, where the HDPE is initially in direct contact with molten metal at 460 °C. Due to the equal temperature across the molten metal, secondary reactions are minimised, and long‐chain waxes with boiling points over 600 °C accumulate on the molten metal. Once enough wax has accumulated, further HDPE pyrolysis occurs within the wax in a direct heat transfer reaction.

IMPACT OF NANOPARTICLES AS A HOMOGENEOUS CATALYST IN IGNITION CHARACTERISTICS OF WASTE PLASTIC OIL

A novel approach was employed to develop alternative fuels by blending pyro-oil from used plastic with graphene, which acted as a combustion additive. The biofuels were produced through pyrolysis of high-density polyethylene (HDPE). When evaluating the fuel blends, the fuel properties were analyzed and compared to commercially available diesel fuel, while Fourier transform infrared (FTIR) spectrometry was employed to know the fuel character. The findings demonstrate that including graphene as a combustion additive significantly enhances the Fuel's performance. The phenomena suggest that graphene effectively weakens the dispersion forces among the triglyceride molecules. Consequently, the droplet is easier to burn. By incorporating graphene, the alternative fuels droplet exhibits improved ignition properties, offering potential benefits in terms of efficiency and performance. The additive plays a crucial part in modifying the molecular structure of the Fuel, resulting in enhanced reactivity and ignition characteristics. Furthermore, the analysis of physical properties and spectroscopic data provides valuable insights into alternative fuels' molecular composition and behavior.

Synergistic Activity of the Fe2O3/Al2O3 Catalyst for Hydrogen Production through Pyrolysis-Catalytic Decomposition of Plastics

Plastic recycling through thermochemical conversion for the production of fuels and chemicals is a promising way for simultaneous waste processing and utilization. In the current study, high-density polyethylene (HDPE) was subjected to pyrolysis and then catalytic upgrading to produce hydrogen in the presence of a novel Fe2O3/Al2O3 catalyst with a grain boundary. To understand the catalyst–support interaction as well as the resulting synergistic catalytic effects, catalytic pyrolysis of HDPE with supported Fe2O3/Al2O3 was compared with those over Fe2O3, Al2O3, and a cascade combination of both. It was found that the performance of Fe2O3/Al2O3 was superior to that of other catalysts in terms of chain cracking and C–C/C–H bond cleavage. The hydrogen yield with Fe2O3/Al2O3 was 50.53 mmol·gplastic–1, equivalent to more than 70% of hydrogen in plastic. Besides, alkanes/alkenes ranging from C2 to C9 dominated the hydrocarbon products. The analysis of the cycle performance revealed that the reduction pathway of Fe2O3/Al2O3 was different from those of other Fe2O3-containing catalysts, which was also confirmed by temperature-programmed reduction. To investigate the essential role and reaction mechanism with Fe2O3/Al2O3, characterizations of Fe2O3/Al2O3 before and after the reaction were conducted. The grain boundary between Fe2O3 and Al2O3 enhanced the adsorption of gaseous products. More importantly, the catalyst–support interaction to form FeAl2O4 during the pyrolysis reaction, determined by X-ray photoelectron spectroscopy, was responsible for effective proton adsorption and C–H bond cleavage. This study provides an insightful understanding of catalyst transformation during plastic catalytic pyrolysis for hydrogen production.

Synergistic interactions between sewage sludge, polypropylene, and high-density polyethylene during co-pyrolysis: An investigation based on iso-conversional model-free methods and master plot analysis

Sewage sludge (SS) is a hazardous by-product of wastewater treatment processes that requires careful management for minimal environmental impacts and effective resource recovery. Through thermochemical processes such as pyrolysis, clean energy is recovered from SS in the form of bio-oil, biogas, and biochar. To improve the yield and quality of products, the co-pyrolysis of more than two materials is increasingly gaining interest. Here, the thermal behaviour, kinetics, and synergistic interactions during the co-pyrolysis of SS with polypropylene (PP) and high-density polyethylene (HDPE) were comparatively evaluated with thermogravimetric analysis at different mixing ratios and heat rates. Activation energies and reaction mechanisms were determined through iso-conversional model-free methods and master plot analysis. Evolved gases were monitored with thermogravimetric-mass spectrometry. Increased volatile conversion and degradation rates, and reduced activation energies during co-pyrolysis were mediated by synergistic interactions between H-radicals of PP/HDPE and oxygenated intermediates of SS. Contrary to the pyrolysis of SS, PP and HDPE, the co-pyrolysis processes are predominantly diffusion-controlled. Insights into the co-pyrolysis processes of SS/PP and SS/HDPE gained from this work provide the theoretical support for subsequent investigation, facilitate design of waste-to-energy reactor, and aid the adoption of the technology to harness the bioenergy potential of the feedstocks.

Investigation of high-density polyethylene pyrolyzed wax for asphalt binder modification: Mechanism, thermal properties, and ageing performance

The thermal pyrolysis of high-density polyethylene in a fixed bed reactor has been studied in the temperature range of 450–550 °C with two different nitrogen carrier gas flowrates, 2 and 4nullLnullmin−1, to study the effect of these process parameters as well as the resultant vapour residence times on the formation of wax and its chemical and thermal properties. The technology had a high selectivity to waxes, with a yield of up to 91.87% wax from high-density polyethylene at 500 °C using a nitrogen carrier gas flowrate of 4nullLnullmin−1 and subsequent 1.76 second vapour residence time, calculated using the ideal gas law. The waxes were characterised using techniques including gas-chromatography-mass spectroscopy (GC-MS), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The process operating temperature especially and its subsequent effect on vapour residence times within the reactor had a considerable impact on both the chemical and thermal properties of the waxes. Higher operating temperatures yielded more olefinic waxes due to the promotion of degradation radical mechanisms such as β-scission. They were observed to have higher melting points and thermal stability. An investigation was conducted to assess the thermal properties and ageing performance of the waxes. Thermal conditioning in an ashing oven at 170 °C for 0–6 hours was conducted with a detailed analysis of GC-MS and FTIR at each stage of thermal exposure to further support thermal characterisation results. The changes in chemical composition were attributed mainly to oxidation and polymerization ageing reactions and were seen to be more prominent in the more unsaturated waxes produced at higher pyrolysis temperatures. The wax produced at 550 °C was determined the optimal wax for binder modification in hot-mix asphalt pavement design due to lower volatile/mass loss. A lower temperature range was suggested for optimal blending conditions to further reduce loss of volatiles with initial blending and storage.

Estimating the efficiency of catalysts for catalytic pyrolysis of polyethylene

The paper is devoted to investigation of the catalytic pyrolysis of high-density polyethylene (PE) in the presence of HBEA, HZSM-5 and HFER catalysts and natural clay. Catalytic pyrolysis of plastic materials is a promising method for treatment of secondary raw materials because it allows converting polymers into chemical compounds, which further serve as a source for chemical industry. Physicochemical parameters of the catalysts were estimated using various methods: IR Fourier spectroscopy, X-ray diffraction analysis, physical adsorption of N2, thermogravimetric analysis, and pyrolytic gas chromatography. Temperature dependences of PE destruction were obtained as well as the dependence of chemical composition of the catalytic pyrolysis products on the catalyst type. Two main factors were shown to determine the efficiency of cracking and the qualitative composition of products – structural and acidic parameters of the catalyst. The presence of Broensted acid sites in zeolites promoted the cracking and aromatization reactions. The possibility of using the clay sample for thermal decomposition of PE was estimated.

Co-pyrolysis of pinewood and HDPE: pyrolysis characteristics and kinetic behaviors study

Abstract Co-pyrolysis of lignocellulosic biomass and hydrogen-rich petroleum-based polyolefin plastics is a promising to way to improve bio-oil quality and alleviate the waste plastic pollution issues. In this study, co-pyrolysis of pinewood and HDPE was systematically investigated. The addition of HDPE decreased yield of char and gas while increased that of bio-oil, enhancing the selectivity to alcohols and hydrocarbons. The most obvious synergistic effect was observed at the HDPE mixing proportion of 0.25, at which hydrocarbon selectivity derived from co-pyrolysis experiments was 41.19% higher than the calculated weighted average values. As pyrolysis temperature increased from 500°C to 700°C, the yield of bio-oil from co-pyrolysis at the HDPE mixing proportion of 0.25 decreased from 69.11 wt.% to 50.33 wt.%, alkanes selectivity decreased from 27.41% to 3.67% and olefins selectivity increased from 14.96% to 47.12%. At 700°C, aromatics started to produce with a selectivity of 15.50%. The surface morphologies of char were not significantly affected by the HDPE mixing proportion and pyrolysis temperature. The thermogravimetric analysis results revealed that the global co-pyrolysis process can be divided into two major degradation stages, based on which multi-step method was adopted to analyze the kinetics of the process. The average apparent activation energies of stage I and stage II were 167.73 kJ/mol and 274.74 kJ/mol, respectively. The results from this work provide a theoretical guide for further development of co-pyrolysis of pinewood and high-density polyethylene (HDPE).