Promotion of palladium-based catalysts on metal monolith for partial oxidation of methane to syngas

Four different modifications of alumina were prepared for use as the support for a Pd catalyst used for the partial oxidation of methane to syngas. The catalysts were washcoated on a metallic monolith in order to determine their activities at high gas flow rates. Compared with the Pd/Al2O3 catalyst, enhanced partial oxidation activities were observed with the Pd/CeO2/Al2O3, Pd/CeO2/BaO/Al2O3 and Pd/CeO2/BaO/SrO/Al2O3 catalysts. The palladium particles were better dispersed in the presence of CeO2 and SrO. Adding BaO, CeO2 and BaO–CeO2 to γ-Al2O3 prevented the transformation of the alumina phase during the 3-day aging process at 1000 °C, providing the support with some level of thermal stability. The addition of small amounts of SrO to the CeO2/BaO/Al2O3 support enhanced the thermal stability of the Pd particles and minimized their sintering. The triply promoted Pd catalyst studied in this work was effective in carrying out partial oxidation at high temperatures, with BaO and CeO2 promoting the thermal stability of the support, CeO2 and SrO dispersing the Pd particles and SrO anchoring the Pd particles strongly to the support. The composition of the catalyst which gave both the highest partial oxidation activity and the best thermal stability was Pd(2)/CeO2(23)/BaO(11)/SrO(0.8)/Al2O3.