| A large quantity of gas which produced from flame coal's pyrolysis and gasification in northern shanxi province have been releasted into environment. These gas contains a great quantity of CH4 and CO2, both of them are greenhouse. On the basis of this background, CH4-CO2 reforming was proposed to high efficiently utilize CH4 and CO2. However, Ni catalysts were easy deactivated in CH4-CO2 reforming. Carbon-based catalysts offers certain advantages:durability (high temperature resistance and tolerance to sulfur); resistance to carbon formation and high activity. So we investigated various carbon materials as catalysts for CH4-CO2 reforming.The research used four carbon-based catalysts (FuGu coke, TongChuan coke, AC1, AC2) for CH4-CO2 reforming reaction. We also researched deashed cokes using different orders. The AC1 exhibited best catalysis activity. So it was modified by different concentrations of nitric. FT-IR techniques were used to characterize surface properties. (Liquid) nitrogen adsorption isotherm method was used to characterize pore structure. Finally, we added different promoters to ACl to increase the activity of catalysts as well as the stability. We screened the promoters to find the best activity of the catalyst. The research indicated:Thermodynamic analyses for CH4-CO2 reforming. The results indicated that there is chemical reaction between CH4 and CO2, when reaction temperature is higher than 890.57K. The higher temperature, the more conversion. But the conversion of CH4 and CO2 were very low in practice. So catalyst has a huge developing space.Compared with blank test, it can be seen obviously that four carbon-based catalysts had apparent activated to CH4-CO2 reforming in the temperature range from 700℃to 1000℃. The AC1 showed the best catalytic activity.Study on deashed cokes using different orders, we concluded that ash has no effect on catalytic activity of cokes at 700℃. For FuGu coke, the FuGu coke deashed before pyrolysis exhibited highest activity at 900℃and the FuGu coke deashed after pyrolysis showed lowest activity. For TongChuan coke, the TongChuan coke deashed after pyrolysis exhibited highest activity at 800℃and the TongChuan coke deashed before pyrolysis showed lowest activity. when the reaction temperature is 900℃, the initial activity order of three TongChuan cokes is the same as 800℃, but in the late stage, the catalytic activity of TongChuan coke deashed before pyrolysis is as good as TongChuan coke deashed after pyrolysis.Study on modified AC1, The activity and stability of AC1 modified by 9 mol/L HNO3 enhanced greatly. The conversion of CH4 and CO2 were increased by 15.9%and 9.8% respectively compared to unmodified. The mass loss of 9-AC1 was only 22%of the unmodified catalyst. The SEM showed deposition of carbon was not found on the surface of 9-ACl. The properties of catalysts were characterized by FT-IR, BET. Phenolic hydroxyl and ether bond played a key role on the catalytic activity of activated carbon and the more quantity of pore from 30-45 (?), the higher catalytic activity.The role of addition of different promoters to AC1 have been investigated. When reaction temperature is higher than 900℃, promoters have a small part in CH4-CO2 reforming. But at 700℃, the catalytic activity was dramatically improved through adding agents, especially sodium nitrate. The reactivity order of promoters:NaNO3>Ca(NO3)2>Al(NO3)3, which is the same as their alkaline. So different sodium salt and different NaNC3 concentrations were further researched. We can draw the conclusion that catalytic activity was best when NaNO3 was added 5%(wt). |
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