Effect of metal additives on the catalytic performance of Ni/Al2O3 catalyst in thermocatalytic decomposition of methane

Abstract

Thermocatalytic decomposition of methane is proposed to be an economical and green method to produce COx-free hydrogen and carbon nanomaterial. In present work, 60 wt% Ni/Al2O3 catalysts with different additives (Cu, Mn, Pd, Co, Zn, Fe, Mg) were prepared by co-impregnation method to investigate promotional effects of these metal additives on the activity and stability of 60 wt% Ni/Al2O3 and find out a really effective promoter for decomposition of methane. The catalyst was characterized by N2 adsorption/desorption, X-ray diffraction, scanning electron microscopy, inductively coupled plasma optical emission spectrometer and hydrogen temperature programmed reduction. While metal additives (5 wt%) were added into 60 wt% Ni/Al2O3, the activity stability of 60 wt% Ni/Al2O3 was improved and the CH4 conversion of 60 wt% Ni/Al2O3 was also improved except Zn addition. Mn addition was found to improve the catalytic activity of 60 wt% Ni/Al2O3 significantly and the CH4 conversion of 5 wt% Mn-60 wt% Ni/Al2O3 was ∼80%. Cu addition was found to remarkably improve the catalytic stability of 60 wt% Ni/Al2O3 and the CH4 conversion of 5 wt% Cu-60 wt% Ni/Al2O3 decreased from 61% to 45% after 250 min of reaction time. Carbon nanomaterials formed in the thermocatalytic decomposition process were characterized by X-ray diffraction, scanning electron microscopy, thermal gravimetric analyzer and Raman spectroscopy. Carbon deposits consist of amorphous carbon and carbon nanofibers.