Assessing the Suitability of Kaolin as a Catalyst for Polyethylene Plastic Waste Pyrolysis: A Case Study Kikuubo-Uganda
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Date
2025-04-09
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Uganda Christian University
Abstract
In the Kampala Metropolitan Area, including Mbuya, approximately 135,804 tonnes of plastic waste are generated annually, of this, 42% remains uncollected, 15% is collected through value chain approaches, and 43% is collected by service providers. Significant amounts of plastic waste are either burned (21,728 tonnes), landfilled (47,457 tonnes), or end up in water systems (13,580 tonnes) (I. Tumuhimbise, 2023). Despite multiple bans on plastics since 2009, plastic use has not decreased, with over half of the waste ending up in open land and waterways (Ugandan Environmental Authorities, 2020). Recycling rates are alarmingly low at only 1%, and few companies recycle or repurpose plastic (S. Naluyima, 2022).Traditional methods such as landfilling, open dumping, and incineration are unsustainable due to environmental degradation and public health risks. Pyrolysis, a thermochemical process that decomposes plastic waste into fuel and chemical feedstocks in the absence of oxygen, offers a promising alternative (Sharma et al., 2020). However, conventional pyrolysis faces challenges such as high energy demands, prolonged reaction times, and low-quality outputs due to incomplete hydrocarbon breakdown (Kizito, 2022). Catalytic pyrolysis addresses these limitations by using catalysts to lower reaction temperatures, improve efficiency, and enhance product yield. This study investigates the suitability of kaolin, a locally abundant and cost-effective aluminosilicate clay, as a catalyst for polyethylene (PE) plastic waste pyrolysis. Kaolin’s high silica (SiO₂) and alumina (Al₂O₃) content (53.67% and 24.47%, respectively) provides acidic sites that facilitate hydrocarbon cracking, while its thermal stability ensures durability under high temperatures (Wang et al., 2021). The research evaluates kaolin’s impact on pyrolysis efficiency, optimizing the kaolin-to-PE ratio, reaction time, and product yield. Experiments conducted using a fixed-bed reactor demonstrated that a 16% kaolin-to-PE ratio maximized liquid yield (75.67%), minimized char (4.08%) and gas (20.24%) production, and reduced reaction time by 18% compared to non-catalytic pyrolysis.
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