Transforming plastic waste into clean fuel and chemical: zeolite-catalyzed dechlorination and cracking of plastic-derived oil

Because of the continuous increase in the amount of plastic waste, catalytic cracking is an interesting method that could be used to convert heavy oil from thermal cracking of plastic waste into fuel. The objective of this study was to investigate the hydrodynamic behavior and the performance of catalytic cracking of heavy oil in a circulating fluidized bed reactor using computational fluid dynamics. The two– fluid model incorporated with the kinetic theory of granular flow was applied to predict the hydrodynamic behavior with a reactive flow. Three reactor geometries were studied, which included a conventional riser, tapered–out riser, and tapered–in riser. The four–lump kinetic model was used to describe the catalytic cracking of heavy oil from waste plastic. A core–annulus flow pattern was found in the three reactor geometries. The solid fraction distribution of the tapered reactor was found to be more uniform than that of the conventional riser. The tapered–in riser showed the highest heavy oil conversion with the lowest gasoline selectivity. However, the heavy oil conversion and gasoline selectivity of the conventional and tapered–out reactors were not significantly different.

Assessing the feasibility of chemical recycling via steam cracking of untreated plastic waste pyrolysis oils: Feedstock impurities, product yields and coke formation

The effects of reaction conditions and properties of the catalysts used on the product yields and quality of the gasoline fraction from the catalytic cracking of heavy oil obtained from waste plastics over rare-earth metal exchanged Y-type (REY) zeolites were examined. Gasoline with high contents of isoparaffins and low contents of n-paraffins and aromatics is desired in order to increase the research octane number and to achieve complete burning. A large amount of gasoline with these favorable components was obtained by the catalytic cracking of heavy oil over a REY zeolite catalyst under the condition of a time factor (ratio of the mass of the catalyst to the mass flow rate of the feed oil) of 0.75-1 kg-cat.kg-oil −1 .h, a reaction temperature of 673 K, and a catalyst of small crystal size that has a moderate amount of sites of strong acid strength

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetic studies for catalytic cracking of heavy oil from waste plastics over REY zeoliteAhmad Rahman Songip, Takao Masuda, Hiroshi Kuwahara, and Kenji HashimotoCite this: Energy Fuels 1994, 8, 1, 131–135Publication Date (Print):January 1, 1994Publication History Published online1 May 2002Published inissue 1 January 1994https://doi.org/10.1021/ef00043a022RIGHTS & PERMISSIONSArticle Views587Altmetric-Citations49LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (537 KB) Get e-Alerts Get e-Alerts

Maximizing light olefin production via one-pot catalytic cracking of crude waste plastic pyrolysis oil

Sustainable ethylene production: Recovery from plastic waste via thermochemical processes

Steam cracking is an integral process in the plastic manufacturing industry. Conventional steam crackers are tubular reactors and use fossil-based feedstocks like naphtha and LPG. This work presents steam cracking in a dual fluidized bed (DFB) reactor as an alternative for the direct steam cracking of plastic waste. Experiments were performed on a semi-industrial DFB system using naphtha, clean polyolefins, real-life plastic wastes, and a polyolefin-derived pyrolysis oil. The results show that steam cracking in a DFB is fundamentally equivalent to steam cracking in tubular reactors. Selective production of light olefins and monoaromatics was achieved within a temperature range of 700–825 °C. Naphtha yielded up to 56 % light olefins and 7 % BTXS, with ethylene and BTXS production positively correlating with cracking severity, while C3 and C4 olefins show a negative correlation. These results confirm that the established steam cracking mechanisms also apply to large-scale DFB steam crackers. The yield of light olefins is consistently obtained at approximately 52 % relative to the polyolefin content of the feedstock, regardless of the non-polyolefin content. This highlights the DFB steam cracker’s ability to produce light olefins directly from plastic waste without presorting. However, steam cracking in DFB results in significantly higher CO and CO2 yields than conventional steam cracking, especially with feedstocks containing non-polyolefins like PET and cellulose. Additionally, steam cracking of an olefin-rich pyrolysis oil yields up to 50 % light olefins with minimal coke formation, highlighting the potential in processing plastic waste pyrolysis oils without pretreatment steps such as distillation and hydrotreatment.

Nanozeolite aggregates (NZAs) have emerged as a class of promising catalysts for waste plastic recycling and industrial applications, owing to the coexistence of nanozeolite domains for short diffusion lengths and micron-scale bulk size for the ease of industrial processing. However, it is challenging to synthesize NZAs in a facile and green routine. Conventional hydrothermal routes often rely on commercial silicon reagents and costly secondary templates to create mesopores, rendering them difficult for practical applications. Herein, a facile approach for NZAs synthesis is developed using natural silicon-rich diatomite as the sole silicon source, and a continuous three-step process on diatomite surface is streamlined, including (1) Si dissolution, (2) surface-involved nucleation, and (3) Na+-assisted rapid in situ crystallization. As characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller (BET), Hg intrusion, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and electron probe microanalysis (EPMA), the obtained NZAs exhibit micron-scale particle sizes (1–5 μm) with hierarchically porous structures (SBET = 336 m2/g). The surfaces of the obtained NZAs are fully covered with self-assembled ZSM-5 nanocrystals, meanwhile mesopores that run through the nanocrystal domains are spontaneously created without the need for additional secondary templates. Compared to commercial microsized zeolites with higher crystallinity, NZAs exhibit better activity and higher propylene yields in catalytic cracking of n-octane and polypropylene pyrolysis oil. The enhanced performances may be linked to the existence of highly accessible acid sites in NZAs, which help suppress secondary reactions of propylene. This work offers an economically viable and environmentally benign for novel NZA catalyst synthesis aiming at circular economy.

Towards high-quality petrochemical feedstocks from mixed plastic packaging waste via advanced recycling: The past, present and future

Maximizing olefin production via steam cracking of distilled pyrolysis oils from difficult-to-recycle municipal plastic waste and marine litter

Global plastic waste generation exceeds 460 million tons per year, while recycling rates remain below 10%. Innovative solutions are needed for recycling plastic waste into valuable products. This study employs experimental data and two methods to evaluate economic analysis of fluid catalytic cracking (FCC) of plastic-derived pyrolysis oil: physics-based and machine learning (ML)-based methods to model the effects of reactions in the FCC unit. FCC offers many advantages compared to hydrocracking: e.g., it operates under lower pressure (implying lower equipment costs), eliminates the use of hydrogen, and runs with reduced operating costs. The physics-based model was used to determine reaction stoichiometries, ensuring chemical plausibility, while a Decision Tree regressor was employed to predict product yields based on the cycle number and cycle time, a proxy for catalyst deactivation that captures time-dependent experimental observations. Both models were integrated surrogate models within a full process model in BioSTEAM to conduct a technoeconomic assessment (TEA) and a life-cycle assessment (LCA) with uncertainty analysis. The research also highlights the production of valuable chemicals, specifically light olefins such as ethylene and propylene and aromatic compounds such as benzene, toluene, and xylenes (BTX). The ML-based framework estimated a minimum selling price (MSP) for naphtha of approximately $1.38/kg under input uncertainties, while the physics-based approach estimated an MSP of $1.76/kg. These results are within 22% of each other, which is within the expected range of ± 30% for the preliminary TEA estimates. These findings suggest that ML-based approaches can be an effective substitute for physics-based models when there is limited understanding of the underlying chemical mechanisms. Sensitivity analysis captured the impacts of varying the catalyst cycle number and times. Cycle numbers between 1 and 4 and cycle times of up to 20 min resulted in MSPs ranging between 1 and 2 $/kg. This variation captures the impacts of catalyst deactivation in FCC systems, supporting the need for optimizing the catalyst performance.

Energy-efficient processes using sustainable resources, such as plastic waste, are essential for alleviating environmental pollution and carbon emissions. Herein, we demonstrated the highly efficient direct conversion of crude waste plastic pyrolysis oil (WPPO) into light olefins using a pilot-scale circulating fluidized bed reactor (CFBR) with a WPPO throughput of 1000 g·h–1. Catalytic WPPO cracking over a microspherical P-modified steam-treated ZSM-5 catalyst outperformed naphtha cracking in terms of the C2–C4 olefins yield (44.1 vs 34.6 wt %), highlighting the superiority of WPPO as a feedstock for light olefin production. Fine-tuning the operating parameters, including the catalyst circulation rate (24,000 g·h–1), feed rate (1000 g·h–1), and catalyst-to-oil ratio (24) further increased the C2–C4 olefins yield to 46.2 wt %. Main product yields were stable during a 24 h durability test, with average ethylene, propylene, C4 olefins, and C2–C4 olefins yields of 10.3, 21.4, 12.6, and 44.3 wt %, respectively, indicating the suitability of the CFBR for continuous catalytic WPPO cracking. This approach offers advantages over commercial schemes, including complete utilization of crude WPPO, increased C2–C4 olefins yield, reduced energy consumption, continuous coke removal, and non-necessity of hydroprocessing, making it a promising alternative for sustainable light olefin production with environmental benefits.

3D-printed monolithic ZSM-5@nano-ZSM-5: Hierarchical core-shell structured catalysts for enhanced cracking of polyethylene-derived pyrolysis oils

Mechanism investigations on co-pyrolysis of polyethylene and biomass using ReaxFF simulation and DFT computation

The increasing amount of waste plastics which causes serious pollution problems is a cheap and abundant source of chemicals and energy. Chemical recycling method which recovers hydrocarbons is recognized as the ideal approach in recycling the waste.1 The economics and engineering constraints in the chemical method of a combined pyrolysis-reforming reactor has been discussed earlier.2 The pyrolysis-reforming reactor was found to inhibit systematic study on the effects of various reaction conditions. A proposed process scheme of independently studying the pyrolysis and catalytic reforming reactions has been shown to alleviate the constraints of the combined pyrolysis-reforming scheme.2