阶跃升温分解法对非负载型镍催化甲烷分解活性的影响

Influence of Step Temperature Elevating Decomposition on the Catalytic Activity of Non-supported Ni for Methane Decomposition

以乙醇为洗涤溶剂采用沉淀法制备了非负载型Ni催化剂,考察了预处理过程对催化剂上CH4分解活性的影响.X射线衍射及CH4程序升温表面反应结果表明,降低还原温度可减小Ni粒子尺寸,从而提高催化剂活性.同时,采用CH4多温度逐步分解(多点阶跃升温分解)法可形成较稳定的Ni粒子,有效提高催化剂的活性及稳定性,500oC下CH4初始转化率可达8.40%,反应120min时升至11.20%;而在350和500oC两点阶跃升温分解的CH4最高转化率只有1.61%.

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 ℃.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 ℃ 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 ℃ was only 1.61%.