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The management of plastic waste (PW) has become an indispensable worldwide issue because of the enhanced accumulation and environmental impacts of these waste materials. Thermo-catalytic pyrolysis has been proposed as an emerging technology for the valorization of PW into value-added liquid fuels. This review provides a comprehensive investigation of the latest advances in thermo-catalytic pyrolysis of PW for liquid fuel generation, by emphasizing polyethylene, polypropylene, and polystyrene. To this end, the current strategies of PW management are summarized. The various parameters affecting the thermal pyrolysis of PW (e.g., temperature, residence time, heating rate, pyrolysis medium, and plastic type) are discussed, highlighting their significant influence on feed reactivity, product yield, and carbon number distribution of the pyrolysis process. Optimizing these parameters in the pyrolysis process can ensure highly efficient energy recovery from PW. In comparison with non-catalytic PW pyrolysis, catalytic pyrolysis of PW is considered by discussing mechanisms, reaction pathways, and the performance of various catalysts. It is established that the introduction of either acid or base catalysts shifts PW pyrolysis from the conventional free radical mechanism towards the carbonium ion mechanism, altering its kinetics and pathways. This review also provides an overview of PW pyrolysis practicality for scaling up by describing techno-economic challenges and opportunities, environmental considerations, and presenting future outlooks in this field. Overall, via investigation of the recent research findings, this paper offers valuable insights into the potential of thermo-catalytic pyrolysis as an emerging strategy for PW management and the production of liquid fuels, while also highlighting avenues for further exploration and development., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The use of lignocellulosic waste as an energy source for substituting fossil fuels has attracted lots of attention, and pyrolysis has been established as an effective technology for this purpose. However, the utilization of bio-oil derived from non-catalytic pyrolysis faces certain constraints, making it impractical for direct application in advanced sectors. This study has focused on overcoming these challenges by employing fractional condensation of pyrolytic vapors at distinct temperatures. The potential of five types of sawdust for producing high-quality bio-oil through pyrolysis conducted with a bench-scale bubbling fluidized bed reactor was investigated for the first time. The highest yield of bio-oil (61.94 wt%) was produced using sample 3 (damaged timber). Remarkably, phenolic compounds were majorly gathered in the 1st and 2nd condensers at temperatures of 200 °C and 150 °C, respectively, attributing to their higher boiling points. Whereas, carboxylic acid, ketones, and furans were mainly collected in the 3rd (-5 °C) and 4th (-20 °C) condensers, having high water content in the range of 35.33%-65.09%. The separation of acidic nature compounds such as acetic acid in the 3rd and 4th was evidenced by its low pH in the range of 4-5, while the pH of liquid collected in the 1st and 2nd condensers exhibited higher pH (6-7). The well-separated bio-oil derived from biomass pyrolysis facilitates its wide usage in various applications, proposing a unique approach toward carbon neutrality. In particular, achieving efficient separation of phenolic compounds in bio-oil is important, as these compounds can undergo further upgrading to generate hydrocarbons and diesel fuel., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Young-Kwon Park reports financial support was provided by National Research Foundation. Moonis Ali Khan reports financial support was provided by King Saud University., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

[Display omitted] • Catalytic pyrolysis of sewage sludge for the production of aromatics is studied. • A higher yield of aromatics is obtained using HZSM-5 compared to HY and Hβ. • CH 4 decomposition environment outperforms CH 4 and N 2 for aromatics production. • The introduction of Ni or Mo on HZSM-5 increases the aromatics yield. • Co-impregnation of Ni and Mo on HZSM-5 further enhances the aromatics yield. Sewage sludge is solid waste resulting from wastewater treatment processes, and its improper management adversely affects the environment and human health. This study aims to convert sewage sludge into valuable aromatics, including benzene, toluene, ethylbenzene, and xylenes, or BTEX, via the catalytic pyrolysis using mono- and bimetal-modified protonated Zeolite Socony Mobil–5, or HZSM-5, catalysts under nitrogen, methane and methane decomposition conditions. In the methane medium, HZSM-5 yielded more BTEX (20.91 wt%) compared to those obtained using protonated Y zeolite (HY) (17.24 wt%) and protonated beta zeolite (Hβ) (11.70 wt%) owing to its proper acidity, higher shape selectivity, and higher methane activation. When HZSM-5 is used, the BTEX yield increased considerably in the methane decomposition environment (27 wt%), 1.29 and 1.46 times higher than those produced under methane and nitrogen, respectively. This increase is attributed to the dual effects of the surplus in situ hydrogen (H 2) and direct involvement of methane, which resulted in accelerated hydrocracking, hydrodeoxygenation, and co-aromatization reactions. Under methane decomposition conditions, the use of the Ni/HZSM-5, Mo/HZSM-5, and Ni-Mo/HZSM-5 catalysts led to 1.23-, 1.30-, and 1.66-fold increases in BTEX production, respectively, than that of the parent HZSM-5, owing to the dual effects of acidity enhanced by the newly formed Lewis acid sites, increased oxygen vacancies, and improved physical properties of the catalysts. Hence, the catalytic pyrolysis of sewage sludge using mono- and bimetal-modified HZSM-5 catalysts in a H 2 -rich environment proposed in this study is expected to be an efficient and sustainable method for converting undesirable materials into valuable biofuels. [ABSTRACT FROM AUTHOR]

Owing to the ever-increasing generation of plastic waste, the need to develop environmentally friendly disposal methods has increased. This study explored the potential of waste plastic straw to generate valuable light olefins and monocyclic aromatic hydrocarbons (MAHs) via catalytic pyrolysis using high-silica zeolite-based catalysts. HZSM-5 (SiO 2 /Al 2 O 3 :200) exhibited superior performance, yielding more light olefins (49.8 wt%) and a higher MAH content than Hbeta (300). This was attributed to the increased acidity and proper shape selectivity. HZSM-5 displayed better coking resistance (0.7 wt%) than Hbeta (4.4 wt%) by impeding secondary reactions, limiting coke precursor formation. The use of HZSM-5 (80) resulted in higher MAHs and lower light olefins than HZSM-5 (200) because of its higher acidity. Incorporation of Co into HZSM-5 (200) marginally lowered light olefin yield (to 44.0 wt%) while notably enhancing MAH production and boosting propene selectivity within the olefin composition. These observations are attributed to the well-balanced coexistence of Lewis and Brønsted acid sites, which stimulated the carbonium ion mechanism and induced H-transfer, cyclization, Diels-alder, and dehydrogenation reactions. The catalytic pyrolysis of plastic straw over high-silica and metal-loaded HZSM-5 catalysts has been suggested as an efficient and sustainable method for transforming plastic waste materials into valuable light olefins and MAHs. [Display omitted] • Waste plastic pyrolysis was conducted to produce light olefins and aromatics. • HZSM-5(200) outperformed Hbeta(300) for light olefins and aromatics production. • HZSM-5(200) achieved a higher light olefins yield (49.8 wt%) than HZSM-5(80). • The use of HZSM-5(80) maximized the generation of aromatics. • The addition of Co into HZSM-5 improved the generation of aromatics and propene. [ABSTRACT FROM AUTHOR]

This study presents the catalytic pyrolysis of microalgae, Chlorella vulgaris (C. vulgaris), using pure CH 4 and H 2 -rich gas evolved from CH 4 decomposition on three different HZSM-5 catalysts loaded with Zn, Ga, and Pt, aimed specifically at producing high-value mono-aromatics such as benzene, toluene, ethylbenzene, and xylene (BTEX). In comparison with that for the typical inert N 2 environment, a pure CH 4 environment increased the bio-oil yield from 32.4 wt% to 37.4 wt% probably due to hydrogen and methyl radical insertion in the bio-oil components. Furthermore, the addition of bimetals further increased bio-oil yield. For example, ZnPtHZ led to a bio-oil yield of 47.7 wt% in pure CH 4. ZnGaHZ resulted in the maximum BTEX yield (6.68 wt%), which could be explained by CH 4 activation, co-aromatization, and hydrodeoxygenation. The BTEX yield could be further increased to 7.62 wt% when pyrolysis was conducted in H 2 -rich gas evolved from CH 4 decomposition over ZnGaHZ, as rates of aromatization and hydrodeoxygenation were relatively high under this condition. This study experimentally validated that the combination of ZnGaHZ and CH 4 decomposition synergistically increases BTEX production using C. vulgaris. [Display omitted] • Chlorella vulgaris pyrolysis was performed under N 2 , CH 4 and CH 4 -D environment. • Synergistic effect of Zn and Ga led to enhanced CH 4 activation and aromatization. • The CH 4 -D case led to maximum BTEX yield due to higher H/C eff ratio. • The CH 4 -D environment suppressed the coke formation. [ABSTRACT FROM AUTHOR]