Plastic Pyrolysis Research Articles

Analysis and prediction model of the minimum explosion concentration of plastic dust in gaseous fuel environments

Polyethylene dust and polypropene dust were selected to measure the minimum explosion concentration in three kinds of gaseous fuel environments. The results show that the MEC of polyethylene dust with higher apparent activation energy decreased more significantly, and the plastic dust showed higher explosion sensitivity for the gaseous fuel with high combustion heat. The explosion mechanism for plastic dust in gaseous fuel environments was proposed with the global reaction kinetics of plastic pyrolysis, and it suggests that the gaseous fuels reduce the apparent activation energy of plastic dust and provide additional heat for the plastic dust explosion. A corresponding prediction model for the minimum explosion concentration of plastic dust was established. The new model has good applicability for the data obtained in this work and the data in the previous reference.

Oxidative stability of hydrocarbons produced by pyrolysis of polypropylene

The instability of liquid oils issued from the pyrolysis of plastics usually leads to the degradation and the deterioration of their different properties. In this study, the stability of oils produced from the pyrolysis with and without reflux of polypropylene (PP) was investigated in a standard test device called PetroOxy. This work compares the stability of PP liquid oils with kerosene throughout their induction period and hydroperoxide (ROOH) content, two well-known stability parameters. Moreover, experimental investigations of the impact of a stabilizer (BHT = butylated hydroxytoluene) on the same stability parameters were achieved. A titration method and GC-MS were used to quantify ROOHs and to identify the oxidized liquid compounds, respectively.PetroOxy tests with BHT showed an enormous influence of BHT on the oxidation stability compared to all other oxidative tests. Adding 500 ppm of BHT multiplied the induction period by 5.9, 4.3, 10.7 and 6.7 for reflux liquid oils, no-reflux liquid oils mixed with kerosene, reflux liquid oils mixed with kerosene and pure kerosene respectively. The ROOH concentration was divided by up to 16.9 for reflux liquid oil when BHT was used.Based on the results, it can be concluded that the liquid oils obtained by pyrolysis with reflux are less stable than without reflux, and both of them are less stable than kerosene used as reference model. But using kerosene as solvent mixed with liquid oils obtained by pyrolysis with and without reflux increases their oxidative stability. The use of BHT as an antioxidant contributes to make these oils compatible for use as fuels.

Waste catalyst potential for co-pyrolysis of biomass and single-use plastics: model-free isoconversional kinetics and thermodynamics

AbstractThe study aims to investigate the kinetic and thermodynamic characteristics of single and binary pyrolysis of biomass (date pits: DP) and single-use-plastics (polypropylene: PP, and polystyrene: PS), and the effect of adding natural catalysts—seashell (SS) and cuttlebone (CB) for ternary co-pyrolysis of the feeds. The activation energy (Ea) was calculated using different model-free kinetic methods, including Kissinger–Akahira–Sunose (KAS), Ozawa–Flynn–Wall (FWO), and Starink, utilizing information from the degradation at three heating rates from room temperature to 1173 K. The results showed that all three methods produced relatively similar Ea values with a high coefficient of correlation (R2), indicating a good fit for the data. The Ea values for single feeds of DP, PP, and PS using the FWO method were found to be in the range of 196–223 kJ/mol, while for binary feeds—DPPP and DPPPS—the values were found to be lower than for the individual plastics. The high Ea values of the binary plastic mixture are also reduced by ~ 40 kJ/mol in the ternary mixture due to biomass co-pyrolysis. Additionally, the study revealed that the addition of SS and CB catalysts positively affected the ternary co-pyrolysis by reducing activation energy by 28.5 and 5.8%, respectively, due to the catalytic activity of 20 wt% of CaCO3 decomposition from the seashell and cuttlebone added in situ to the feeds. The research contribution of this study lies in its comprehensive investigation of the kinetic and thermodynamic characteristics of biomass and plastic pyrolysis, including single and binary systems, as well as the introduction of natural catalysts for ternary co-pyrolysis. The findings highlight the effectiveness of the studied catalysts in reducing activation energy and provide valuable insights for the development of efficient biomass and plastic waste conversion processes.

Ga-modified zeolites to convert mixed waste plastics to benzene, toluene, ethylbenzene, and xylene (BTEX)-enriched oil through a dielectric barrier discharge plasma-modified reactor

Non-thermal plasma (NTP)-assisted catalytic pyrolysis is a promising technology for producing benzene, toluene, ethylbenzene, and xylene (BTEX) from mixed waste plastics. A primary challenge in this approach is the need to achieve a high selectivity for the target products. To address this challenge, this study focused on the preparation of Ga-modified zeolites. The results showed that Ga loading was effective in increasing BTEX yields for the zeolites of USY, β, and HZSM-5 by 7.49%, 4.72%, and 8.63%, respectively. Among these zeolites, HZSM-5-Ga-N2 was the most suitable for catalyzing the NTP-assisted pyrolysis reaction to produce BTEX hydrocarbons, with a maximum selectivity of 63.19% and a maximum yield of 31.84%. This was because the pore of HZSM-5 matched the ring size of BTEX, and NTP improved the distribution of Ga2O3 active sites, allowing more acidic active sites to participate in the catalytic reaction. This work provides an applicable solution to increase the selectivity and yield of BTEX from NTP-assisted pyrolysis of mixed waste plastics with Ga-loading catalysts.

Non-isothermal thermal decomposition behavior and reaction kinetics of acrylonitrile butadiene styrene (ABS)

Environmental concerns associated with the rapid rising plastic consumption have led to the search for better waste utilization and management. Pyrolysis has emerged as an ideal and promising technique for energy extraction from plastic waste. The aim of this work is to explore the waste plastic pyrolysis behavior under non-isothermal heating conditions. The decomposition characteristics, reaction mechanism, kinetics and thermodynamics of a typical widely used thermosetting plastic, acrylonitrile butadiene styrene (ABS), were studied via coupled thermogravimetry, Fourier transform infrared spectrometry and gas chromatography-mass spectrometry analysis (TG-FTIR-GC/MS). Kinetic analysis showed the average Eα values are estimated to be 187.02, 188.55, 187.04 and 185.67 kJ/mol via advanced Vyazovkin, Flynn-Wall-Ozawa (FWO), Tang and Starink model-free method, respectively. Model-fitting CR and master-plots method indicated that f(α)=(1-α)n is the most probable reaction mechanism. The equation of kinetic compensation effect was further developed as lnA = −3.1955 + 0.1736 Eα. Based on these initial inferences, a new reaction scheme coupled with Particle Swarm Optimization (PSO) was put forward for modeling ABS pyrolysis. The optimized values of E, A and n are 198.07 kJ/mol, 7.61 × 1012 s−1 and 1.56, respectively. The predicted results showed that the experimental data can be well characterized by the optimized parameters from PSO, validating the effectiveness and accuracy of the inverse modeling procedure. Moreover, it is found that the volatile products are mainly composed of aromatic compounds, ketones, amines, esters, nitrile compounds, alkenes and amines. Based on the FT-IR and GC-MS results, the possible chemical reactions for ABS pyrolysis from molecular structure were proposed. Finally, thermodynamic analysis was carried out, the calculated values of enthalpy ΔH, Gibb's free energy ΔG and entropy ΔS indicated that non-spontaneous reactions with low favorability exists during ABS decomposition, the process is complex therefore extra energy is needed to promote the reaction. The obtained results should offer as an important reference for future disposal and thermochemical management of such polymer waste.

Upgrading MSW pyrolysis oil through distillation and hydrotreatment for automobile engine applications: A short review

The demand for fossil fuel in today’s world is increasing at a higher pace with rapid population growth and industrial development. The reserve for petroleum-based fossil fuels is finite which necessitates the search for alternative fuels. Pyrolysis oil obtained from Municipal Solid Waste (MSW) has drawn the attention of many researchers because of their high heating value and similar fuel properties with commercial automobile fuel and has potential to substitute commercial diesel fuel. Nevertheless, the crude oil obtained from pyrolysis of MSW has some shortcomings such as higher viscosity and density, lower flash point and cetane index, unpleasant odor, and higher sulfur content, preventing its useability as a drop in fuel for automobiles at present. In this short review, distillation and hydrotreatment post treatment procedures, amongst many others, are discussed for improving the properties of pyrolysis crude oil. Focus has been given on waste plastic and waste automobile tire pyrolysis oils as they constitute a significant amount of MSW currently. This review reported that noticeable improvement of the properties (cetane number, flash point, viscosity, and sulphur contents) of crude pyrolysis oil (PPO or TPO) can be achieved through distillation and/or hydrotreatment, which are comparable to the properties of standard diesel.

Standard diesel production from mixed waste plastics through thermal pyrolysis and vacuum distillation

Plastic pyrolysis oil (PPO) was produced in a pilot-scale batch pyrolysis reactor at 540 °C from mixed waste plastic (MWP) (high-density polyethylene (HDPE), polypropylene (PP) and polystyrene (PS)). The produced PPO was then distilled in a vacuum distillation unit and diesel was obtained at temperatures between 170 and 380 °C along with light petrol (<170 °C) and heavy residue (>380 °C). This study found that MWP can produce over 80% liquid oils without operational problems or wax formation. Distilled PPO produces 49.5–53% diesel, 39 – 46.5% petrol and residue 1.5 – 8% by weight. Although PPO has calorific value ranging from 43.85 to 45.26 MJ/kg like commercial diesel however, PPO is not suitable for direct use in diesel engine for low kinematic viscosity (KV) and density values at 1.1–1.26 mm2/s and 0.78 – 0.83 gm/cm3 respectively. For the distilled diesel cut (DC), KV, density, higher heating value (HHV), cetane index (CI), aromatic hydrocarbon (AH) and poli-aromatic hydrocarbon (PAH) were found 1.95–2.15 mm2/s, 0.81 – 0.85 gm/cm3, 44.92–46.36 MJ/kg, 46 – 58, 18.81 – 35.1% and 4.81 – 11.9% respectively indicating better option for direct use as automobile diesel with significant effect of HDPE amount present in feedstock.

Halogenated polymers as a problematic component in the pyrolysis of waste plastics

The study deals with the complications associated with the pyrolysis of a polymer releasing highly corrosive compounds and other products that are difficult to be utilized in practice. Poly(vinyl chloride-vinyl acetate) was chosen as a sample material. This copolymer was subjected to slow pyrolysis up to a temperature of 650 °C, which was achieved with a temperature ramp of 10 °C min‒1. Thermal decomposition took place in a batch apparatus in nitrogen atmosphere. The evaluation of the experiments included a mass balance using an online recording of gas and condensate formation, which was followed by an analysis of the obtained products. The tests showed very small yields of condensates (pyrolysis tar) in the range of 3.0 – 5.5% compared to gas production reaching 71.1 – 72.1% of the raw material weight. Within the discussion, the problem with the production of non-flammable gas consisting mainly of HCl in the initial stages of pyrolysis was highlighted. Under the given conditions, the release of acid gases, in which HCl was gradually replaced by also non-flammable CO2, continued up to about 400 °C. Only gases collected from this temperature above and having a calorific value of 33.5 MJ m‒3 (20 °C / 101.32 kPa) can be considered energetically usable. Condensates mainly represented by a mixture of aromatic hydrocarbons, acetic acid and chlorobenzene were also evaluated as problematic for possible use. The possibilities of physical activation of solid pyrolysis residues by steam at temperatures of 850 and 900 °C were also tested. All experiments led to obtaining products with very small specific surface areas in the range of 1 – 6 m2 g–1. The process loss during activation reached 25 – 33% of the pyrolysis residue weight, depending on the applied temperature and contact time with steam. These values show that the reaction of the activation medium with the sample took place more or less only on the outer surface of the particles and did not lead to the development of an internal porous structure. The achieved results were compared with the identically processed samples of waste tires, which were evaluated as promising in tests carried out in the past. The contrast be-tween the two materials clearly spoke against the discussed copolymer. The results of the experiments can be interpreted, among other things, as a certain warning against attempts at industrial pyrolysis processing of this type of plastic.

Performance and emission characteristics of a CI engine with post-treated plastic pyrolysis oil and diesel blend

Conversion of waste plastics into energy products is an effective waste management technique as they constitute a considerable portion of solid waste at present. In this study, distilled diesel fraction of Plastic Pyrolysis Oil (PPO) named Distilled Plastic Diesel (DPD) was hydrotreated named hydrotreated plastic diesel (HPD) and blended with commercial diesel fuel by 15:85 ratio (wt%), defined as HPD15, to experimentally investigate the performance and emission characteristics of a compression ignition (CI) engine. The experiment was done in 4-cylinder, 4-stroke diesel engine with an eddy current dynamometer testbed at full load (100 % engine load) and an engine speed of 1200–2400 rpm with 300 rpm intervals. The results are compared with neat diesel fuel data at the same operating conditions. This study found that HPD15 performed better or comparable with diesel fuel. Overall, the brake power (BP) and brake thermal efficiency (BTE) of HPD15 were higher than diesel fuel by a maximum of about 4.77 % and 3.77 %, respectively. Brake specific fuel consumption (BSFC) of HPD15 was lower at all operating speeds (by a maximum of about 4.66 %) and brake specific energy consumption (BSEC) was lower in most of the operating speeds (by a maximum of about 3.77 %). This study also revealed that CO2 at some operating speeds and NOx emission at all operating speeds for HPD15 are lower than diesel fuel. However, CO and unburnt hydrocarbon (UHC) emission are slightly higher for HPD15 than diesel at all speeds. Overall, HPD15 can be recommended as a suitable alternative for diesel fuel without any engine modification.

Techno-Economic Feasibility Study for Organic and Plastic Waste Pyrolysis Pilot Plant in Malaysia

Organic and plastic waste (OPW) is diverted from landfills in order to lower carbon emissions. Nevertheless, modern pyrolysis techniques are frequently utilized in laboratories (using feedstocks that weigh less than 1 kg), which employ costly pure nitrogen gas (N2). This study developed a fast pyrolysis system to produce pyrolysis oil or liquid (PyOL) from OPW using flue gas as the pyrolysis agent. The added benefits included the efficient value-added chemical extractions and the non-thermal plasma reactor upgraded PyOL. OPW was also pyrolyzed at a pilot scale using flue gas fast pyrolysis in this study. In addition to lowering operational expenses associated with pure N2, flue gas reduced the lifecycle carbon emissions to create PyOL. The results indicated that considerable material agglomeration occurred during the OPW pyrolysis with an organic-to-plastic-waste (O/P) ratio of 30/70. Furthermore, the liquid yields were 5.2% and 5.5% when O/P was 100/0 (305 °C) and 99.5/0.5 (354 °C), respectively. The liquid yields also increased when polymers (polypropylene) were added, enhancing the aromatics. Two cases were employed to study their techno-economic feasibility: PyOL-based production and chemical-extraction plants. The mitigated CO2 from the redirected OPW and flue gas produced the highest revenue in terms of carbon credits. Moreover, the carbon price (from RM 100 to 150 per ton of CO2) was the most important factor impacting the economic viability in both cases. Plant capacities higher than 10,000 kg/h were economically viable for the PyOL-based plants, whereas capacities greater than 1000 kg/h were financially feasible for chemical-extraction plants. Overall, the study found that the pyrolysis of OPW in flue gas is a viable waste-to-energy technology. The low liquid yield is offset by the carbon credits that can be earned, making the process economically feasible.

Sustainable production of aromatics via catalytic pyrolysis of polyolefins towards the carbon cycle for plastics

Catalytic pyrolysis has been emerging as a promising chemical recycling technology to convert plastic waste into olefins and aromatics that can be used as alternatives to petroleum-based chemicals and promote the carbon cycle for plastics. However, the above procedure typically suffers from poor selectivity of the target product. Herein, catalytic pyrolysis of polyolefin plastics was carried out in a two-stage fixed bed reactor for highly selective production of monocyclic aromatic hydrocarbons (MAHs), over Zn-P/HZSM-5 catalysts. After loading 3.0 wt% Zn and 0.5 wt% P on HZSM-5 catalyst, catalytic pyrolysis of low-density polyethylene (LDPE) at 500 °C achieved the highest liquid yield of 55.9 wt% and exhibited a remarkably high selectivity up to 87.44 % towards MAHs, especially in which the BTEX (benzene, toluene, ethylbenzene, xylene) content reached 75.16 %. The introduced Zn species decreased Brønsted acid sites while increased Lewis acid sites of HZSM-5, which in turn improved the aromatization activity. Simultaneously, the addition of P decreased the acidity strength, inhibiting the formation of coke and polycyclic aromatics hydrocarbons. Furthermore, catalytic co-pyrolysis of LDPE, high-density polyethylene (HDPE) and polypropylene (PP) were investigated to reveal the synergistic effect in terms of BTEX selectivity. Intriguingly, a high liquid yield of 55.7 wt% can be obtained at a feeding ratio of HDPE:LDPE:PP = 1:1:1, and an enhanced selectivity of MAHs up to 87.66 % was achieved, with the highest BTEX content of 79.89 %. Finally, carbon emission assessments of catalytic plastic pyrolysis indicated that it presented great potential to reduce carbon emission and facilitate carbon cycle.

Catalytic pyrolysis of polypropylene and polyethylene terephthalate waste using graphene oxide‐sulfonated zirconia (GO‐Szr) and analysis of its oil properties for Bharat Stage VI fuel production

AbstractThis research work is focused on the production of liquid hydrocarbon fuel from plastic waste. To perform the experiments, polypropylene waste (PPW) and polyethylene terephthalate (PETW) were selected and pyrolyzed in a semi‐batch reactor at a temperature of 500°C. Nearly 72.28 wt.% of liquid fuel was recovered from 100 g of plastic waste feed through non‐catalytic pyrolysis process. The application of catalyst GO‐Szr to the pyrolysis process increased the oil yield to 92.76 wt.%. The oil properties were studied, to assess the characteristics and to compare with that of diesel fuel. The properties of oil were found to possess very good diesel properties such as kinematic viscosity of 2.18 mm2/s, density of 790 kg/m3, cloud and pour point less than −11°C, Sulphur content less than 3 ppm and cetane number was found to be as high as 72.44. From these studies, it is highlighted that waste plastics pyrolysis is a suitable option to produce diesel‐like fuel.

Effect of ambient temperature and density on the transition of hot temperature combustion to low temperature combustion of commercial diesel and waste plastic diesel in an optical access machine

Alternative diesel production from mixed waste plastic pyrolysis is an effective method for the management of waste plastic and its related costs. The low temperature combustion (LTC) of diesel enables the reduction of nitrogen oxides and soot simultaneously. However, because of the high quantity of unburned hydrocarbon (UHC) and carbon monoxide (CO) emissions, LTC has a low combustion efficiency. This paper investigated the combined effect of low ambient temperature and high density (LATHD) on the transition from hot temperature combustion (HTC) to LTC by using commercial diesel (CD) and waste plastic diesel (WPD) without exhaust gas recirculation (EGR) and low cetane fuels. The results showed that NOx and soot concentrations were decreased and integral heat release was increased. For a given unit heat release, the NOx emissions of CD and WPD decreased 60% and 38%, respectively, by decreasing the ambient temperature from 1050 K to 750 K. Furthermore, integral heat release is a more influential parameter on NOx than heat release rate. After that, soot concentrations of CD and WPD were significantly decreased by 85% and 81% with a reduction in ambient temperature from 1050 K to 750 K. At the same ambient temperature, the NOx and soot concentrations of WPD were higher than that of CD for all cases. With the same ignition delay, however, the NOx and soot concentrations of WPD/high cetane fuel decreased dramatically compared to CD. This information will be useful for determining compression ratio and combustion phasing when considering engine designs.

Life-cycle analysis of recycling of post-use plastic to plastic via pyrolysis

Advanced recycling enables the application of post-use plastics (PUP) to produce valuable industrial chemicals and develop markets for recycled feedstocks. Pyrolysis is one of the most common advanced recycling technologies undergoing industrial-scale implementation for converting PUP. This paper presents a life cycle analysis (LCA) to assess greenhouse gas (GHG) emissions, fossil energy, water consumption, and solid waste impacts of converting PUP into new plastics such as high-density and low-density polyethylene (HDPE and LDPE, respectively). Data was collected from eight plastic pyrolysis companies. This study addresses the impacts of pyrolysis plant size and maturity; two substitution rate (SR) cases of pyrolysis oil with fossil-derived feedstocks in steam crackers (5% and a 20% of pyrolysis oil SR); and potentially avoided emissions from traditional end-of-life (EOL) management. Because the conventional feedstock slate of steam crackers in the Unites States is comprised of 94% gases (a mix of ethane, propane, and butane) and 6% naphtha, the 5% SR case looked at polyethylene (PE) derived from 5% pyrolysis oil, 1% naphtha, and 94% gases; while the 20% SR looked at PE derived from 20% pyrolysis oil and 80% gases. Moreover, the results are presented from two perspectives: 1) steam crackers' and 2) plastic recyclers'. In the recyclers' perspective, the results for the 5% SR showed for each kg of PUP used there was a 23% and 18% decrease in GHG emissions for HDPE and LDPE respectively, while the 20% SR showed a 4% and 3% reduction in GHG emissions for HDPE and LDPE respectively compared to virgin plastic. The 20% SR has lower GHG emissions reductions because there is an added step of hydrotreating the pyrolysis oil to remove chlorine concentrations that is not included in the 5% SR scenario. Furthermore, the 5% SR removes most of the naphtha, a more carbon intense feedstock, and replaces it with PUP-based pyrolysis oil, a less carbon intense feedstock. GHG emissions for PUP pyrolysis could be further reduced by 50% and 131% in the United States and European Union respectively if the GHG emissions of current PUP incineration practices were considered as emission reductions credits.

Removal of carbon residue precursor in waste plastic pyrolysis oil via oxidation

Removal of carbon residue precursor in waste plastic pyrolysis oil via oxidation

Screening of Commercial Organic Solvent Nanofiltration Membranes for Purification of Plastic Waste Pyrolysis Liquids.

Increasing consumption rates of plastics, combined with the waste generated from their production, leads to several environmental problems. Presently, plastic recycling takes account of only about 10% of the plastic waste, which is achieved mainly through mechanical recycling. Chemical recycling methods, such as pyrolysis, could significantly increase overall recycling rates and reduce the need for the production of fossil-based chemicals. Produced pyrolysis oil can be used for the production of benzene, toluene and xylene (BTX) through catalytic upgrading or for the production of alkanes if used directly. Separation of high-value components in pyrolysis oil derived from plastic waste through traditional separation methods can be energy intensive. Organic solvent nanofiltration has been recognised as an alternative with very low energy consumption, as separation is not based on a phase transition. This work focuses on the screening of several (semi-) commercially available membranes using a simplified model mixture of pyrolysis oil obtained from plastics. Based on membrane performance, a selection of membranes was used to treat a feedstock obtained from the direct pyrolysis of plastics. This work shows that currently, commercial OSN membranes have promising separation performance on model mixtures while showing insufficient and non-selective separation at very low flux for complex mixtures derived from the pyrolysis of plastics. This indicates that OSN is indeed a promising technology but that membranes should likely be tailored to this specific application.

Experimental investigation of emission parameters of diesel engine fueled with various plastic pyrolysis oils

Plastic has various advantages and is becoming more ubiquitous by the year, yet recycling and disposal remain challenges for the world. We conduct tests in this study to evaluate the appropriateness of various Plastic Pyrolysis Oils (PPOs) made from Low Density Polyethylene (LDPE), High Density Polyethylene (HDPE), and Polypropylene (PP) for diesel engine fuel. Determine which type of plastic pyrolysis oil would function best as an alternative fuel in an experimental investigation. The elemental composition of pyrolysis oil generated from LDPE, HDPE, and PP to diesel was assessed, tabulated, and compared in this study. This study examines emission characteristics (Nitrogen Oxide (NOX), Hydro Carbon (HC), and Carbon Monoxide (CO)) for Diesel, LDPE, HDPE and PP in CI engines using different injection pressure, compression ratio, and load in a specific configuration. In the result of experimental work the CO emission range for diesel and LDPE is exceeded only during overload situations or when the engine load is 100%. The average NOX emission is lowest when PP is used in comparison to other fuels, and the highest NOX emission occurs when LDPE is utilised as a fuel. Increased fumigation rates may be to blame for the rising hydrocarbon content of plastic oil. Unburned hydrocarbon levels are lower at lighter loads due to increased oxygen availability. The use of this whole pyrolysis oil results in a significant decrease in Nitrogen Oxide (NOX), Hydro Carbon (HC), and Carbon Monoxide (CO) exhaust emissions. With the help of this current study. one can solve plastic waste disposal problem and also find any unknown fuel (PPOs) that can be used as an alternative fuel for CI engine or not.

Plasma-catalytic pyrolysis of polypropylene for hydrogen and carbon nanotubes: Understanding the influence of plasma on volatiles

Plasma-catalytic pyrolysis was developed for upgrading polypropylene (PP) pyrolysis volatiles to co-produce carbon nanotubes (CNTs) and hydrogen. To uncover the role of plasma on the plastic catalytic pyrolysis process, the pyrolysis of polypropylene (PP) over Fe/γ-Al2O3 was carried out in a two-stage pyrolysis system with a coaxial dielectric barrier discharge (DBD) plasma reactor. The results showed that the plastic pyrolysis volatiles were further cleaved and activated with plasma, resulting in more active carbon species for the growth of CNTs. Compared to conventional catalytic pyrolysis, plasma addition shifted the initial formation temperature of CNTs to a lower ambient temperature by ∼100 °C, and significantly promoted the conversion of liquid and gaseous products to CNTs and hydrogen, with higher carbon and hydrogen yields of ∼322 mg/gplastic and 30 mmol/gplastic, respectively. In addition, the degree of graphitization of the CNTs in the presence of the plasma was significantly enhanced with less defectivity. The influence of catalytic temperature variation caused by plasma on CNTs growth was also discussed from the perspective of volatile evolution. This work highlights the potential of plasma-catalytic pyrolysis for the production of hydrogen and high-value carbon materials from plastic waste.

Pyrolysis as a value added method for plastic waste management: A review on converting LDPE and HDPE waste into fuel

The global demand for plastic is increasing year by year due to its indispensable uses and excellent properties. Plastic wastes persist for many years due to their slow deterioration and cause severe environmental problems. Therefore, there is a growing focus worldwide on plastic waste disposal methods to overcome adverse environmental impacts. As plastics are petroleum-based materials, the pyrolysis of plastics to fuel oil, gases, and char, has more concern than the other plastic waste management methods of recycling and landfilling. A yield of 70-80 wt.% of liquid fuel from pyrolysis waste has been reported elsewhere, emerging the importance and aptness of this method in plastic waste management. The common reactor types for the pyrolysis process are batch reactor, semi-batch reactor, spouted bed reactor, and fluidized bed reactor. The common catalysts employed in plastic pyrolysis were zeolites, including ZSM-5, HUSY, Zeolite X, and Y. The pore structure and the catalyst’s acidity are the most influencing parameters in increasing the liquid yield and the quality of the oil produced in the pyrolysis process. This paper reviews the existing literature on pyrolysis processes developed for HDPE and LDPE wastes globally and their governing factors. Furthermore, emissions in the pyrolysis process and engine combustion of the fuel oil, performance, and emission characteristics were discussed. Although plastic waste separation prior to its management is a challenging process, this review highlights the conversion of waste plastic into energy as a smart way to meet the rising demands.

Experimental investigation on the effect of injection timing and injection duration of low reactive fuels on RCCI mode of combustion operated with plastic pyrolysis oil

The goal study is to investigate the effect of low reactive fuels (LRFs) injection timing and duration of injection on a reactivity-controlled compression ignition (RCCI) engine. The diesel, mixtures of Karanja oil methyl ester (KOME), plastic pyrolysis oil (PPO) and ethanol are used as LRFs. The examined LRFs have the injection timings (ITs) of 40°ATDC, 45°ATDC, and 50°ATDC. Additionally, the influence of different LRFs injection durations (IDs) of 3, 6, and 9 ms, on the RCCI mode of combustion is included in the present work. The entire experimental process is performed at 75% of the rated power. According to the findings, at IT of 45°ATDC and ID of 6 ms, the Diesel-Gasoline mixture has the highest brake thermal efficiency (BTE) of all the ITs and IDs examined. Nitric oxide (NOx) emissions are higher for all ITs and IDs but smoke, carbon monoxide (CO), and hydrocarbon (HC) emissions are lower for the Diesel-Gasoline mixture compared to other fuel mixtures. Diesel-Gasoline produces a greater peak pressure rise (PPR) compared to other test samples at all ITs and IDs.