Characterization of Pd impregnated on metal/silica-pillared H-keyaites (M-SPK, M = Ti, Zr) catalysts for partial oxidation of methane to hydrogen

Pd(5) impregnated metal/silica-pillared H-keyaites (M-SPK, M = Ti, Zr) catalysts were prepared for the partial oxidation of methane (POM) to hydrogen. The catalysts were characterized by BET, TEM, SAXS and XPS. In addition, the catalytic yield of the POM to hydrogen over Pd(5) impregnated on M-SPK and Pd(5)/Al2O3, commercial catalyst were investigated in a fixed bed flow reactor under (Ed atmosphere. BET-specific surface areas, average pore sizes and nitrogen adsorption/desorption isotherms were 284.3–396.2 m2/g, 3.3–3.8 nm and type B on type IV isotherms for Pd(5)/M-SPK(M = Ti, Zr), and 90.5 m2/g, 8.3 nm and type E on type IV isotherm for Pd(5)/Al2O3, respectively. TEM images of SPK and Pd(5)/SPK showed the formation of mesoporous layer compounds, as well as the homogenous dispersion of Pd particles on the surface. SAXS peaks at 0.13 Å for fresh Pd(5)/SPK were maintained without being broken, even after about 53 h in stream at 973 K. XPS showed the existence of two oxidation states for Pd (Pd0 and Pd2+) on the surface of the catalyst, depending on the carrier, whereas the presence of Ti and Zr in SPK induced a change in the oxidation state (O2−, O−) of the catalyst. The yield values of the POM to hydrogen over Pd(5)/M-SPK(M = Ti, Zr) were 64.9% and 55.8%, respectively, at 973K, CH4/O2 = 2, GHSV = 8.4 × 104 ml/gcat h, and these values were kept constant even after 70 h in stream. These results confirm that Ti and Zr in SPK frame induced oxidation states of Pd, and that the yield of Pd(5)/M-SPK positively regulates the POM to hydrogen.