甲烷催化裂解制备碳纳米管过程中二氧化碳的影响

生物质发酵沼气含有高浓度CH₄,具有制备碳纳米管的潜力,但其中所含的大量CO₂对碳纳米管制备存在潜在影响. 研究了CH₄催化裂解制备碳纳米管过程中CO₂的影响,使用商用Ni基催化剂和水平管式炉装置开展碳纳米管制备试验,采用TPR、TPO、SEM、TEM等手段对催化剂和碳纳米管进行表征. 650 ℃时催化裂解效率最高,碳产物最大质量为催化剂质量的4倍,其中主要产物为多壁碳纳米管. CO₂对最佳催化裂解温度、催化裂解效率及多壁碳纳米管产量无显著影响,但CO₂的存在增加了碳纳米管内外径、长度和平滑度. 这可能是由于CH₄催化裂解产生无定形积碳,阻碍碳纳米管生长; 而CO₂与积碳反应清除积碳,促进了碳纳米管生长. 从CO₂的影响来看,沼气制备碳纳米管具有可行性.

Effect of CO2 on the Preparation of Carbon Nanotubesby Catalytic Cracking of CH4

Biogas contains high concentrations of CH₄,so it has a potential to produce carbon nanotubes. However,the high concentration of CO₂ in it has a potential impact on the preparation. In this paper,we investigate the effect of CO₂ on the preparation of carbon nanotubes by catalytic cracking of methane. The carbon nanotube preparation experiments are carried out by using the commercial nickel-based catalyst and the horizontal tube furnace apparatus. The catalysts and carbon nanotubes are characterized by TPR,TPO,SEM,TEM,etc. The highest catalytic cracking efficiency is obtained at 650 ℃ with the maximum mass of carbon products which are 4 times as much as that of the catalyst. The main product is multi-walled carbon nanotubes. CO₂ has no effect on the best temperature for catalytic cracking,the highest efficiency of catalytic cracking and the production of multi-wall carbon nanotubes. However,CO₂ increases the inner diameter,length and smoothness of the carbon nanotubes,which may be due to the deposited amorphous carbon from CH₄ inhibition of catalytic cracking,that hindered the growth of carbon can nanotubes. However,the reaction of CO₂ and deposited carbon removes the deposited carbon,resulting in the enhancement of the carbon nanotubes growth. From the perspective of the impact of CO₂,it is feasible to prepare carbon nanotubes from biogas.