The effect of Kankara zeolite-Y-based catalyst on some physical properties of liquid fuel from mixed waste plastics (MWPs) pyrolysis

Catalyst Accessibility and Acidity in the Hydrocracking of HDPE: A Comparative Study of H-USY, H-ZSM-5, and MCM-41 Modified with Ga and Al

Plastic pollution is a critical environmental issue due to the widespread use of plastic materials and their long degradation time. Hydrocracking (HDC) offers a promising solution to manage plastic waste by converting it into valuable products, namely chemicals or fuels. This work aims to investigates the effect of catalyst accessibility and acidity on the HDC reaction of high density polyethylene (HDPE). Therefore, a variety of materials with significant differences in both textural and acidic properties were tested as catalysts. These include H-USY and H-ZSM.5 zeolites with various Si/Al molar ratios (H-USY: Si/Al = 2.9, 15, 30 and 40; H-ZSM-5: Si/Al = 11.5, 40, 500) and mesostructured MCM-41 materials modified with Ga and Al, also with different Si/metal ratios (Si/Al = 16 and 30; Si/Ga = 63 and 82). Thermogravimetric analysis under hydrogen atmosphere was used as a preliminary screening tool to evaluate the potential of the various catalysts for this application in terms of energy requirements. In addition, batch autoclave reactor experiments (T = 300 °C, PH2 = 20 bar, t = 60 min) were conducted to obtain further information on conversion, product yields and product distribution for the most promising systems. The results show that the catalytic performance in HDPE hydrocracking is determined by a balance between the acidity of the catalyst and its structural accessibility. Accordingly, for catalyst series where the structural and textural properties do not vary with the Si/Al ratio, there is a clear correlation of the HDPE degradation temperature and of the HDPE conversion with the Si/metal ratio (which relates to the acidic properties). In contrast, for catalyst series where the structural and textural properties vary with the Si/Al ratio, no consistent trend is observed and the catalytic performance is determined by a balance between the acidic and textural properties. The product distribution was also found to be influenced by the physical and chemical properties of the catalyst. Catalysts with strong acidity and smaller pores were observed to favor the formation of lighter hydrocarbons. In addition to the textural and acidic properties of the catalyst, the role of coke formation should not be neglected to ensure a comprehensive analysis of the catalytic performance.

A State-of-the-Art Review on the Technological Advancements for the Sustainable Management of Plastic Waste in Consort with the Generation of Energy and Value-Added Chemicals

Plastic waste poses a serious threat to the environment and it has been increasing at an alarming rate. In 2022, global plastic waste generation was reported to be around 380 million tonnes as compared to 353 million tonnes in 2019. Production of liquid fuel from plastic waste is regarded as a viable method for disposing of the plastic and utilizing its energy. Currently, a wide range of technologies have been explored for turning plastic waste into fuel, including the conventional pyrolysis, incineration, gasification and advanced oxidation. However, a systematic summary and comparative analysis of various technologies has still not reported. Traditional non-biodegradable plastic waste (NPW) treatment methods include landfilling and incineration, but these methods encounter bottlenecks and are unable to adequately address NPW issues. This review attempts to present a thorough summary of treatment methods for plastic waste (both conventional and novel treatment technologies that have recently been reported), examine their mechanism and their current state of development. Furthermore, the superiority and drawbacks of each technology are analysed and the prospects of technology application are proposed. By tackling the problems of white pollution and energy scarcity, this review intends to inspire the use of solid waste as a source of energy.

Utilizing Waste Plastic Bottle-Based Pyrolysis Oil as an Alternative Fuel

In the present work, an experimental investigation is carried out on the use of waste plastic oil produced from waste poly(ethylene terephthalate) (PET) bottles (WPOB) as an alternative fuel for diesel engines. The physical and chemical properties of WPOB were analyzed, and it was found that it has fuel properties similar to those of petroleum fuels. The WPOB was tested in a diesel engine to evaluate the effect of WPOB on combustion and emissions characteristics. In addition, particulate matter (PM) emissions generated by the combustion of WPOB were analyzed. The combustion of WPOB was retarded with respect to diesel fuel, resulting in higher carbon-based emissions. The thermogravimetric analysis (TGA) results show that the temperature to reach the maximum rate of soot oxidation was lower with WPOB combustion. Because of the significant delay at the start of combustion and increase in emissions, the direct use of WPOB in the diesel engine is not recommended. It is suggested that WPOB can be used as a blend component to reduce the amount of diesel fuel used in diesel engines. Thus, further study on the effect of diesel fuel blended with WPOB on the combustion and emissions characteristics was performed. The results reveal that the maximum WPOB present in diesel fuel to avoid the increase in carbon-based emissions is 20% by volume to keep combustion and emissions characteristics similar to those of diesel fuel.

Kinetic study of the pyrolysis of polypropylene over natural clay

Clay is widely used in numerous industrial activities; however, its application as an efficient catalyst for the decomposition of plastic waste on a commercial scale is scanty. Therefore, in this study, we have made efforts to use natural clay as the catalyst for the thermal decomposition of polypropylene in a pyrolysis setup. The pyrolysis oil obtained was found rich in hydrocarbons ranging from C8–C35. Kinetics of the pyrolysis reaction was determined utilizing thermogravimetric data and the activation energy (E) and A-factor were observed as 70.33–94.80 kJ/mol and 6 × 105–2.3 × 108 min−1 using the Ozawa-Flynn-Wall method and 58.19–74.82 kJ/mol and 4.1 × 102–4.2 × 103 min−1 applying Tang Wanjun equation. The activation energy was found to increase with enhancement in conversion presenting a complex decomposition reaction. Comparing the activation energy determined in this work with previous studies confirmed that natural clay has reduced E of decomposition reaction at high fraction conversion. The pyrolysis results supported with the kinetic investigation in this work would have potential applications in disposing of plastic waste on an industrial scale and a step forward in the field of waste management.

Waste Refinery: The Valorization of Waste Plastics and End-of-Life Tires in Refinery Units. A Review

This review collects a wide range of initiatives and results that expose the potential of the refineries to be converted into waste refineries. Thus, they will use their current units for the valorization of consumer society wastes (waste plastics and end-of-life tires in particular) that are manufactured with petroleum derivatives. The capacity, technological development, and versatility of fluid catalytic cracking (FCC) and hydroprocessing units make them appropriate for achieving this goal. Polyolefinic plastics (polyethylene and polypropylene), the waxes obtained in their fast pyrolysis, and the tire pyrolysis oils can be cofed together with the current streams of the industrial units. Conventional refineries have the opportunity of operating as waste refineries cofeeding these alternative feeds and tailoring the properties of the fuels and raw materials produced to be adapted to commercial requirements within the oil economy frame. This strategy will contribute in a centralized and rational way to the recycling of the consumer society wastes on a large scale. Furthermore, the use of already existing and, especially, depreciated units for the production of fuels and raw materials (such as light olefins and aromatics) promotes the economy of the recycling process.