Steam reforming of n-dodecane over K₂Ti₂O₅-added Ni-alumina and Ni-zirconia (YSZ) catalysts

The steam reforming of n-dodecane over 35 wt% Ni supported on alumina (Ni-Al₂O₃) and yttrium-stabilized zirconia (Ni-YSZ) at 800 °C for 10 h with a steam-to-carbon ratio of 3 was tested in the presence and absence of 10 wt% of K₂Ti₂O₅ (KTO) particles. The suppression of coke formation by KTO was investigated using various characterizations, including BET, TPO, TGA, TEM, and EELS. After the addition of 10 wt% of KTO particles by ball milling, Ni-YSZ exhibited stable performance with negligible coke formation at space velocities of less than 20,000 h⁻¹. The addition of KTO to Ni-Al₂O₃ did not yield any improvements because the majority of Ni particles in alumina pores are not directly in contact with the KTO phase. The dispersion of finely divided KTO particles on the surfaces of both Ni and the support effectively suppressed coke formation by steam gasification of the deposited coke into CO and H₂. First, the gradual accumulation of coke during the course of the reaction deactivated the Ni sites, which presented activity for the steam reforming of methane. The Ni and acidic sites, which were effective for the hydrogenolysis of n-dodecane to methane and ethylene (or ethane in the presence of KTO), were eventually deactivated. An overall reaction pathway was then proposed based on the results.