Hydrolysis of Polyamide 6 to ε-Caprolactam over Titanium Dioxide

Area of Science:

• Materials Science
• Chemical Engineering
• Sustainable Chemistry

Background:

• Polyamides (PAs) are prevalent in textile and food packaging waste.
• Current chemical recycling methods for PAs often use homogeneous catalysts that are difficult to recover.
• Efficient recovery of PA monomers is crucial for sustainable material management.

Purpose of the Study:

• To develop a heterogeneous catalyst for efficient chemical recycling of polyamide 6 (PA6).
• To investigate the stability and reusability of the catalyst under industrially relevant conditions.
• To achieve repeatable yields of ε-caprolactam (CL) monomer from PA6 hydrolysis.

Main Methods:

• Utilizing anatase TiO2 as a heterogeneous catalyst for PA6 hydrolysis.
• Investigating catalyst performance at temperatures between 250-330°C and reaction times under 3 hours.
• Employing hydrothermal pretreatment to stabilize the catalyst's morphology and crystallinity.

Main Results:

• Anatase TiO2 demonstrated catalytic activity for PA6 hydrolysis, yielding ε-caprolactam (CL).
• Catalyst reuse led to decreased CL yields due to morphological and textural degradation.
• Hydrothermal pretreatment stabilized the catalyst, enabling repeatable equilibrium CL yields.
• The heterogeneous catalyst operates effectively under industrially relevant conditions.

Conclusions:

• A stabilized heterogeneous anatase TiO2 catalyst enables repeatable ε-caprolactam yields from PA6 hydrolysis.
• Hydrothermal pretreatment is key to maintaining catalyst stability and performance over multiple cycles.
• This approach offers a promising heterogeneous catalytic route for sustainable PA6 chemical recycling.