Abstract: The non-supported Ni catalyst was prepared by calcination of the nickel hydroxide precipitate, originated from precipitation of nickel acetate with aqueous solution of sodium carbonate, rinsed with ethanol. The influence of pretreatment conditions on Ni catalyst was investigated by means of X-ray diffraction, CH4 temperature-programmed surface reaction, and CH4 decomposition reactivity test. The results showed that lowering the reduction temperature could reduce Ni particle size and correspondingly improve the catalytic activity of Ni catalyst for CH4 decomposition. The result of the catalytic activity test showed that reaction history was an important factor influencing the catalytic activity of the Ni catalyst for CH4 decomposition at 500 oC. The formation of relatively stable Ni particles could be realized by carrying out CH4 decomposition stepwise at multiple reaction temperatures (multiple step temperature elevating decomposition), which could remarkably improve the catalytic activity and stability of the Ni catalyst for CH4 decomposition. The initial CH4 conversion reached 8.40% at 500 oC by using the multiple step temperature elevating decomposition method, and the CH4 conversion could further be increased to 11.20% within 120 min, whereas by the two step temperature elevating decomposition method, the maximum CH4 conversion at 500 oC was only 1.61%.

Key words: methane, step temperature elevating decomposition, non-supported nickel catalyst, decomposition reactivity