Palladium (Pd⁰) Loading-Controlled Catalytic Activity and Selectivity for Chlorophenol Hydrodechlorination and...

Area of Science:

• Catalysis
• Nanomaterials
• Environmental Chemistry

Background:

• Chlorophenols (CPs) are environmental pollutants requiring efficient detoxification.
• Reductive catalysis using zero-valent palladium nanoparticles (Pd0NPs) offers a promising route.
• Existing methods for converting CPs to cyclohexanone (CHN) often require harsh conditions.

Purpose of the Study:

• To investigate the hydrodechlorination and hydrosaturation of 4-chlorophenol (4-CP) using Pd0NPs.
• To achieve selective production of CHN, a valuable product, under ambient conditions.
• To understand the role of Pd0NPs morphology, size, and loading in controlling catalytic outcomes.

Main Methods:

• Utilized a hydrogen (H2)-based membrane catalyst-film reactor.
• Deposited Pd0NPs onto H2-transfer membranes.
• Varied Pd0 loading to control nanoparticle characteristics and assess catalytic performance.

Main Results:

• Achieved up to 99% CHN selectivity under ambient conditions.
• Demonstrated that Pd0NPs size and morphology, dictated by Pd0 loading, are critical for activity and selectivity.
• Sub-nano Pd particles favored hydrodechlorination to phenol, while Pd0NPs enabled subsequent hydrosaturation to CHN.
• Higher Pd0 loading (1.0 g-Pd/m2) consistently yielded CHN (>92%), whereas lower loading (0.2 g-Pd/m2) favored phenol (>98%) during 15-day continuous tests.

Conclusions:

• Pd0NPs catalysis in a membrane reactor enables selective CP hydrogenation under ambient conditions.
• Catalyst design, specifically Pd0 loading, allows for precise control over product distribution (phenol vs. CHN).
• This approach offers a sustainable pathway for CP detoxification and resource recovery.