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•Contaminants determine the chemical recycling potential of pyrolysis oils.•Pyrolysis oils contain more and different contaminants than fossil feedstocks.•Contaminants cause ...corrosion, process fouling and downstream catalyst poisoning.•The main contaminants are nitrogen, oxygen, chlorine, iron, lead and calcium.•Advanced analytical techniques and standardization are crucial.
Thermochemical recycling of plastic waste to base chemicals via pyrolysis followed by a minimal amount of upgrading and steam cracking is expected to be the dominant chemical recycling technology in the coming decade. However, there are substantial safety and operational risks when using plastic waste pyrolysis oils instead of conventional fossil-based feedstocks. This is due to the fact that plastic waste pyrolysis oils contain a vast amount of contaminants which are the main drivers for corrosion, fouling and downstream catalyst poisoning in industrial steam cracking plants. Contaminants are therefore crucial to evaluate the steam cracking feasibility of these alternative feedstocks.
Indeed, current plastic waste pyrolysis oils exceed typical feedstock specifications for numerous known contaminants, e.g. nitrogen (∼1650 vs. 100 ppm max.), oxygen (∼1250 vs. 100 ppm max.), chlorine (∼1460vs. 3 ppm max.), iron (∼33 vs. 0.001 ppm max.), sodium (∼0.8 vs. 0.125 ppm max.)and calcium (∼17vs. 0.5 ppm max.). Pyrolysis oils produced from post-consumer plastic waste can only meet the current specifications set for industrial steam cracker feedstocks if they are upgraded, with hydrogen based technologies being the most effective, in combination with an effective pre-treatment of the plastic waste such as dehalogenation.
Moreover, steam crackers are reliant on a stable and predictable feedstock quality and quantity representing a challenge with plastic waste being largely influenced by consumer behavior, seasonal changes and local sorting efficiencies. Nevertheless, with standardization of sorting plants this is expected to become less problematic in the coming decade.
Pyrolysis of plastic packaging waste yields a liquid product that can be processed in steam crackers producing light olefins and hence closing the loop towards new virgin plastics. However, there is ...a lack of knowledge on how the plastic waste composition affects the pyrolysis oil quality regarding hydrocarbon composition and contaminant concentrations. The associated uncertainty is a key reason why thermochemical recycling of contaminated plastic waste is not yet industrially established. In this study, post-consumer plastic packaging waste fractions, namely mixed polyolefins (MPO), polyethylene (PE), and polypropylene (PP) were processed in a continuous pilot-scale pyrolysis unit and the pyrolysis oils subsequently characterized using advanced analytical techniques such as two-dimensional gas chromatography. Substantial amounts of branched olefins (~63 wt%) and diolefins (~20 wt%) were detected in the pyrolysis oil of PP-rich waste, while PE-rich waste produced high amounts of linear paraffins (~34 wt%) and olefins (~26 wt%). Furthermore, significant amounts of nitrogen, oxygen, chlorine, iron, sodium and silicon were detected in the pyrolysis oils exceeding feedstock specifications for industrial steam crackers by orders of magnitude. The results show that next to improved waste sorting and separation processes, pre- and post-treatment techniques are required to produce pyrolysis products suitable for chemical processing.
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•Pyrolysis of polyolefinic post-consumer plastic packaging waste.•Comprehensive two-dimensional gas chromatography coupled to various detectors.•PP-pyrolysis yields highly branched olefins, PE-pyrolysis mostly linear compounds.•Nitrogen, oxygen, chlorine, iron, sodium and silicon most important contaminants.•Upgrading or dilution needed when using pyrolysis oils as steam cracker feedstocks.
New Trends in Olefin Production Amghizar, Ismaël; Vandewalle, Laurien A.; Van Geem, Kevin M. ...
Engineering (Beijing, China),
04/2017, Volume:
3, Issue:
2
Journal Article
Peer reviewed
Open access
Most olefins （e.g., ethylene and propylene） will continue to be produced through steam cracking （SC） ofhydrocarbons in the coming decade. In an uncertain commodity market, the chemical industry is ...investingvery little in alternative technologies and feedstocks because of their current lack of economic viability,despite decreasing crude oil reserves and the recognition of global warming. In this perspective, some of themost promising alternatives are compared with the conventional SC process, and the major bottlenecks ofeach of the competing processes are highlighted. These technologies emerge especially from the abundanceof cheap propane, ethane, and methane from shale gas and stranded gas. From an economic point of view,methane is an interesting starting material, if chemicals can be produced from it. The huge availability ofcrude oil and the expected substantial decline in the demand for fuels imply that the future for proventechnologies such as Fischer-Tropsch synthesis （FFS） or methanol to gasoline is not bright. The abundance ofcheap ethane and the large availability of crude oil, on the other hand, have caused the SC industry to shiftto these two extremes, making room for the on-purpose production of light olefins, such as by the catalyticdehydrogenation of orooane.
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•Light olefin production via steam cracking of plastic waste pyrolysis oils (PWPO).•Main contaminants in PWPO are nitrogen, oxygen, chlorine, calcium and sodium.•High ethylene yields ...of pyrolysis oil/naphtha blends, higher than of pure naphtha.•Substantial formation of heavy products due to high olefin concentrations in PWPO.•Higher coke formation compared to naphtha due to contaminants and olefins in PWPO.
Chemical recycling of plastic waste to base chemicals via pyrolysis and subsequent steam cracking of pyrolysis oils shows great potential to overcome the limitations in present means of plastic waste recycling. In this scenario, the largest concern is the feasibility. Are plastic waste pyrolysis products acceptable steam cracking feedstocks in terms of composition, product yields and coke formation? In this work, steam cracking of two post-consumer plastic waste pyrolysis oils blended with fossil naphtha was performed in a continuous bench-scale unit without prior treatment. Product yields and radiant coil coke formation were benchmarked to fossil naphtha as an industrial feedstock. Additionally, the plastic waste pyrolysis oils were thoroughly characterized. Analyses included two dimensional gas chromatography coupled to a flame ionization detector for the detailed hydrocarbon composition as well as specific analyses for heteroatoms, halogens and metals. It was found that both pyrolysis oils are rich in olefins (∼48 wt%) and that the main impurities are nitrogen, oxygen, chlorine, bromine, aluminum, calcium and sodium.
Steam cracking of the plastic waste derived feedstocks led to ethylene yields of ∼23 wt% at a coil outlet temperature of 820 °C and ∼28 wt% at 850 °C, exceeding the ethylene yield of pure naphtha at both conditions (∼22 wt% and ∼27 wt%, respectively). High amounts of heavy products were formed when steam cracking both pyrolysis oils, respectively. Furthermore, a substantial coking tendency was observed for the more contaminated pyrolysis oil, indicating that next to unsaturated hydrocarbons, contaminants are a strong driver for coke formation.
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•Cable plastic, a mix of PE, XLPE and PVC, cannot be mechanically recycled.•Cable plastic steam cracking was evaluated as recycling option in an industrial scale.•Steam cracking of ...cable plastic shows the production of olefins and benzene.
The use of plastic materials in a circular way requires a technology that can treat any plastic waste and produce the same quality of product as the original. Cable plastic residue from metal recycling of electric wires is composed of cross-linked polyethene (XLPE) and PVC, which is a mixture that cannot be mechanically recycled today. Through thermochemical processes, polymer chains are broken into syngas and monomers, which can be further used in the chemical industry. However, feedstock recycling of such a mixture (XLPE, PVC) has been scarcely studied on an industrial scale. Here, the steam cracking of cable plastic was studied in an industrial fluidised bed, aiming to convert cable plastics into valuable products. Two process temperatures were tested: 730 °C and 800 °C. The results show that the products consist of 27–31 wt% ethylene and propylene, 5–16% wt.% other linear hydrocarbons, and more than 10 wt% benzene. Therefore, 40%–60% of the products are high-value chemicals that could be recovered via steam cracking of cable plastic.
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•Contaminant removal from pyrolysis oils is essential for practical viability.•Depth filtration of contaminated mixed polyolefin pyrolysis oil is effective.•Particle reduction from ...69 mg/L to < 2 mg/L in the filtered samples.•Depending on the fineness, metal contaminant removal of 25–82% was reached.•Steam cracking coke formation reduced by 40–60 % compared to the unfiltered oil.
Recycling of mixed plastic waste via pyrolysis and subsequent steam cracking towards light olefins is a promising solution for the ever-growing plastic waste crisis. However, the pyrolytic recycling pathway is still not established on industrial scale due to the large variety of pyrolysis oil contaminants that hamper the application in (petro-)chemical processes. In short, plastic waste pyrolysis oils are unfeasible for steam crackers without upgrading. In this work, depth filtration for the removal of particulate contamination from a post-consumer mixed polyolefin (MPO) pyrolysis oil was performed using three different filter media with different porosity. Comprehensive analyses using SEM-EDX of the retained particles as well as ICP-OES and GC × GC-FID of the filtered oils allowed to understand the efficacy of filtration. Most of the particulate contamination was removed by filtration leading to a reduction from 69 mg/L in the unfiltered sample to < 2 mg/L in the filtered samples. Particle characterization confirmed that the main contamination is composed of iron, calcium and silicon-based contaminants in combination with carbon-based species. It was confirmed by ICP-OES that after filtration, important contaminants such as nickel, vanadium and lead were reduced below contamination thresholds for steam crackers indicating that filtration is an efficient, and potentially cost-effective upgrading technique for pyrolysis oils. When steam cracking the filtered oils, results show that radiant coil coke formation was reduced by 40–60% compared to the unfiltered oil without changes in product selectivity, confirming the strong impact of particulate contamination on coke formation during steam cracking.
Lower olefins are the second most resource and emission intensive products in the manufacturing sector in Germany. Replacing conventional fossil feedstock with renewable or secondary feedstock thus ...represents a viable possibility to significantly increase the sustainability of the German industry. The environmental impact associated with olefin production is generally determined by feedstock and energy supply as well as the production technology. In the present study, the environmental effects of the utilization of conventional and alternative feedstock are assessed in the form of a cradle-to-gate life cycle assessment performed in GaBi LCA software. The assessment focused on global warming potential, fossil resource depletion and acidification potential of olefin production in Germany. Investigated raw materials included fossil resources in crude oil and shale gas, renewable resources in wood and maize-based biogas as well as secondary resources in municipal solid waste and flue gas-based carbon dioxide. Life cycle inventory data for olefin production are obtained by process simulation using Aspen Plus. Technologically, syngas-based olefin production is characterized by a lower product carbon recovery compared to direct cracker-based olefin production. By integrating upstream impacts, renewable-based production is observed to lead to negative effective greenhouse gas emissions and low resource demand, but showed significant acidification potential from agricultural feedstock production. Due to the avoidance of waste incineration, olefin production via waste gasification is associated with significant benefits in terms of greenhouse gas emissions, despite the substitution of waste-based electricity generation with other energy sources. The utilization of carbon dioxide from flue gas displayed the highest electricity demand by means of hydrogen generation. Therefore, a high level of renewable energy integration is required to be environmentally viable.
•Olefin feedstock alternatives are evaluated in a cradle-to-gate LCA in GaBi.•Global warming, fossil resource depletion and acidification are assessed.•Feedstock included crude oil, shale gas, wood, maize, solid waste and flue gas.•Inventory data for olefin production are provided by process simulation in Aspen Plus.
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•The promotion efficiency of C6 hydrocarbons steam cracking by hyperbranched poly(amidoamine) (PAMAM) was studied.•The underlying initiation mechanism was theoretically ...investigated.•The promotion efficiency of the initiator can be highly dependent on the cracking behaviour of hydrocarbons.•The promotion efficiency of PAMAM follows the order of n-hexane > isohexane > methyl-cyclopentane.
Initiators with low bond dissociation energy can initiate the cracking of hydrocarbons, but the initiation effect on hydrocarbons with different molecule structures remains ambiguous. In this study, the steam cracking of three C6 hydrocarbons, namely n-hexane, iso-hexane and methyl-cyclopentane (MCP), initiated by hyperbranched poly(amidoamine) (PAMAM) were investigated experimentally in a stainless-steel tubular reactor, and the detailed kinetic reaction models and reaction process simulations were conducted by Reaction Mechanism Generator and Chemkin-pro software packages. The results confirm that the addition of PAMAM can significantly promote the cracking conversion and reduce the initial cracking temperature of hydrocarbons because the decomposition of PAMAM at relatively low temperature produces high concentration of active NH2 and CH3 radicals, which significantly increases the rate of hydrogen abstraction. Importantly, the promotion efficiency of the initiator can be highly dependent on the cracking behaviour of hydrocarbons. The initiator will show higher promotion efficiency for hydrocarbon that is more prone to undergo sustained hydrogen abstraction after initiation. Therefore, the promotion efficiency of PAMAM follows the order of n-hexane > iso-hexane > MCP. This study is helpful for a better understanding of the initiation mechanism and will guide the design and screening of effective initiators for naphtha with different compositions.
•Two scenarios of ethylene production with seven electricity sources were performed.•This work aimed to find the proper cases for carbon–neutral ethylene production.•Economic, environmental, and ...technical feasibility of cases were analyzed.•Electrified steam cracking cases had the least carbon dioxide emissions.•Electrified steam cracking had a high potential for carbon neutrality.
Electrification is regarded as one of the solutions for decarbonization. To reduce the emissions of carbon dioxide from the steam cracking which is a conventional ethylene production process, the electrical heating furnace can be applied to the steam cracking called the electrified furnace. Here, to determine whether the electrified steam cracking is proper for carbon neutrality, the techno-economic analysis, life cycle assessment, and the analytic hierarchy process were implemented. The analysis was proceeded by the fourteen cases divided according to steam cracking, electrified steam cracking, and seven electricity generation methods. As a result, considering the technology development level, economic feasibility, and environmental impact, the best case was the steam cracking with hydropower, and the electrified steam cracking with hydropower, solar power, and wind power had high potential. As improving the technology development of the electrified furnace, the electrified steam cracking can be expected to become the proper ethylene production process to achieve carbon neutrality.
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