Abstract:This study evaluates catalytic pyrolysis, microwave pyrolysis, and photocatalytic depolymerization for converting waste plastics into liquid fuels, with an emphasis on the efficiency, selectivity, and scalability. Catalytic pyrolysis achieved a 79.08% liquid yield from high-density polyethylene (HDPE) at 550 ℃ using Fe-HZSM-5 catalysts. Hydrocarbon selectivity was governed by catalyst acidity and pore structure. Hierarchical ZSM-5 further enhanced low-density polyethylene (LDPE) conversion (>95%) by mitigating overcracking through optimized pore architecture. The microwave pyrolysis demonstrated rapid heating kinetics, yielding a 98.78% aromatic-rich liquid fuel from polystyrene (PS) at 600 W with 60 g SiC absorbent. Monoaromatic hydrocarbons dominated the liquid fuel (93.9%), meeting aviation fuel standards. However, excessive power (>6 kW) reduced yields by 10% due to secondary decomposition. Photocatalytic depolymerization in 30% H2O2 facilitated the production of acetic acid yield of 1.1 mmol·g−1·h−1 from polyethylene (PE), utilizing hydroxyl radicals (·OH) to cleave C—C bonds, leading to an increase in PE mass loss from 50.1% to 85.4%. The key findings are as follows: (1) Fe doping in HZSM-5 boosted liquid yields by 16% via enhanced dehydrogenation activity; (2) Microwave absorber loading (e.g., SiC) nonlinearly affected cycloparaffin selectivity (65.6% at 450 W for polypropylene); (3) H2O2 increased photocatalytic PE conversion by 70% compared to pure water, where limited ·OH generation restricted CO2-to-fuel pathways (≤47.4 μg·g−1·h−1). Catalytic pyrolysis faces the challenge of rapid catalyst deactivation (resulting in a 30% activity loss after 5 cycles), while microwave systems incur high capital costs. Photocatalysis prioritizes gaseous products (e.g., H2, CH4) with liquid fuel selectivity below 15% for most polymers. To address these challenges, three actionable pathways are proposed: (1) Pilot-scale optimization: Current studies predominantly use lab-scale feeds (<100 g), necessitating trials with industrial-grade plastics containing pigments and plasticizers. Electrostatic separation pretreatment reduced PVC-derived HCl corrosion by 80% in pilot tests, while anti-fouling membranes (90% recovery) enhanced acetone purity (>98%) in continuous systems. (2) Hybrid energy systems: Integrating microwave heating (200 – 300 ℃/min) with photocatalysis may synergize rapid thermal activation and selective bond cleavage. For instance, microwave-enhanced light absorption in TiO2-MoS2 hybrids doubled charge carrier density, potentially reducing energy consumption by 30% – 40%. (3) Intelligent reactors: IoT-enabled sensors and machine learning algorithms stabilized multiphase reactions in simulated trials, minimizing yield fluctuations to ±5% versus ±15% in batch modes. Real-time monitoring of temperature gradients and microwave power enabled dynamic adjustments, improving diesel-range hydrocarbon selectivity by 25%. Economically, catalytic pyrolysis shows near-term viability with a break-even cost of 0.8 – 1.2 $/L for diesel-range fuels, while photocatalysis requires a 50% – 70% reduction in catalyst synthesis costs (e.g., replacing Pt with Fe-Ni sulfides). Environmentally, microwave pyrolysis reduces carbon intensity by 40% – 60% versus incineration, aligning with net-zero roadmaps. Lifecycle assessments revealed that hybrid systems could achieve carbon-negative profiles when coupled with renewable energy. Future work should focus on developing multifunctional catalysts (e.g., acid-base bifunctional sites for tandem cracking-isomerization), modular reactor designs, and standardized testing protocols to expedite industrial implementation. These strategies underscore the potential of tailored energy-input systems to advance plastic valorization, supporting circular economies and global decarbonization efforts. Close-