Mechanocatalytic PET Depolymerization With Solid Catalyst Separation

The patent replaces conventional homogeneous chemical catalysis with a mechanocatalytic system using solid catalysts in a ball mill. The mechanical energy from ball milling provides the activation energy for depolymerization, substituting the need for homogeneous acids or bases that require expensive separation processes. This resolves the contradiction by achieving depolymerization through mechanical means while eliminating separation costs.

The patent extracts the catalytic function from homogeneous solutions and transfers it to solid catalyst particles that can be easily separated. By using solid NaOH or other solid catalysts in the ball mill, the catalytic activity is maintained while the solid catalyst can be simply filtered or decanted from the reaction mixture, eliminating the complex and costly separation processes required for homogeneous catalysts.

The ball mill creates intense mechanical vibration and collision between the solid catalyst particles and PET feedstock. The grinding balls repeatedly impact and shear the catalyst-feed mixture, ensuring intimate contact between the solid catalyst surfaces and the polymer. This mechanical activation overcomes the limitation of poor contact in conventional heterogeneous catalysis while maintaining easy separability of the solid catalyst.

The patent changes the physical state and energy parameters of the system by applying mechanical energy through ball milling. The mechanical forces generate local high-energy zones and transient temperatures that enhance catalyst activity and contact efficiency. This parameter change allows solid catalysts to effectively process solid feedstock without requiring complex slurry or melt systems.

The patent utilizes phase transition differences to achieve separation without energy-intensive distillation. The mechanocatalytic depolymerization produces monomers that can be separated from the solid catalyst and unreacted polymer through simple filtration and phase separation. The monomers are then purified through crystallization or extraction, leveraging their distinct phase behaviors at different temperatures and solubilities, avoiding the high energy costs of conventional distillation.

The patent replaces thermal separation processes (distillation) with mechanical and phase-based separation methods. The ball mill mechanically separates the solid catalyst from the liquid monomer products, and subsequent purification uses phase transitions and solubility differences rather than continuous heating and vaporization. This substitution dramatically reduces both energy consumption and capital equipment requirements.