High-Temperature Behavior of Pd/MgO Catalysts Prepared via Various Sol-Gel Approaches

Area of Science:

• Materials Science
• Catalysis
• Nanotechnology

Background:

• Nanocrystalline magnesium oxide (MgO) serves as a support for palladium (Pd) catalysts.
• Sol-gel and impregnation methods are employed for catalyst preparation, influencing Pd particle size and oxidation state.
• Understanding catalyst deactivation under thermal stress is crucial for practical applications.

Purpose of the Study:

• To synthesize and characterize Pd/MgO catalysts prepared by different sol-gel routes and impregnation.
• To evaluate the catalytic performance and thermal stability of these catalysts in CO oxidation.
• To investigate the deactivation mechanisms of Pd/MgO catalysts at high temperatures.

Main Methods:

• Catalyst preparation using sol-gel methods with supercritical or ambient drying, and impregnation of aerogel-prepared MgO.
• Characterization techniques including low-temperature nitrogen adsorption, UV-vis spectroscopy, XPS, and TEM.
• Evaluation of catalytic activity via CO oxidation and assessment of thermal stability under aging conditions.

Main Results:

• The impregnated Pd/MgO catalyst exhibited the highest initial activity (T50 = 103 °C) with 3 nm Pd(0) particles.
• The impregnated Pd/MgO-WI sample showed the best thermal stability, with the lowest T50 (215 °C) after aging at 1000 °C.
• Catalyst deactivation was linked to palladium particle agglomeration and the formation of Pd-MgO solid solutions.

Conclusions:

• The preparation method significantly impacts the initial activity and high-temperature stability of Pd/MgO catalysts.
• The initial oxidation state and dispersion of palladium are critical factors governing the catalyst's high-temperature behavior.
• Two distinct deactivation pathways were identified, highlighting the importance of catalyst design for demanding applications.