Size effect of γ-Al2O3 supports on the catalytic performance of Pd/γ-Al2O3 catalysts for HCHO oxidation

Supported noble metal catalysts have been widely utilized for HCHO catalytic oxidation. When the active components are fixed, the altering and regulation of the supports would have a huge effect on catalytic performance. Here, two types of Pd/gamma-Al2O3 catalysts with different support size (micro-gamma-Al2O3 and nano-gamma-Al2O3, respectively) were fabricated and used for HCHO oxidation. Compared with the micro-sized counterpart, the Pd/nano-gamma-Al2O3 catalyst exhibited much superior HCHO oxidation performance which could totally oxidize 160 ppm of HCHO into harmless CO2 under a WHSV of 100,000 mL g(cat)(-1) h(-1) at room temperature. Multiple characterizations including XRD, BET, TEM, CO chemisorption, FT-IR, O-2-TPD, XPS and in situ DRIFTS were implemented to study the effect of gamma-Al2O3 support size on physicochemical properties of Pd/gamma-Al2O3 catalysts and elucidate the structure-activity relationship. The results revealed that large specific surface area, rich surface OH groups as well as high curvature of nano-gamma-Al2O3 not only facilitated HCHO adsorption, but also stabilized highly dispersed Pd species which then promoted the activation of oxygen and boosted formate species decomposition, and consequently leading to the enhanced HCHO oxidation performance of Pd/nano-gamma-Al2O3. This work deepens the comprehension of support size-dependent activity of Pd/gamma-Al2O3 catalysts for HCHO oxidation and provides an alternative method to prepare high-performance Pd catalysts for HCHO oxidation.