Influence of Rare Earth (La, Pr, Nd, Gd, and Sm) Metals on the Methane Decomposition Activity of Ni-Al Catalysts

Rare earth (RE = La, Pr, Nd, Gd and Sm) metal-doped Ni-Al (Ni-RE-Al) hydrotalcite precursors were obtained by coprecipitation and calcined to form mixed oxide catalysts. The physicochemical characteristics of calcined and reduced Ni-RE-Al samples were determined by X-ray powder diffraction, Brunauer-Emmett-Teller surface area, H-2 temperature-programmed reduction, O-2 pulse chemisorption, UV-diffuse reflectance spectroscopy, electron spin resonance spectrometry, and Fourier transform infrared spectroscopy. The catalysts were evaluated for CH4 decomposition at 550 degrees C until their complete deactivation. The deactivated catalysts were examined by transmission electron, scanning electron, and Raman spectroscopy and elemental analysis. The Raman spectra indicated the presence of both ordered and disordered carbon in deactivated catalysts. A correlation is drawn between H-2 production rates and the Ni metal surface area of catalysts. The addition of La to Ni-Al dramatically changed the Ni behavior, leading to higher H-2 yields.