Integrated Process Of Coal Pyrolysis With Catalytic Cracking Of Pyrolysis Products Over Carbon-based Catalyst For High Quality Tar And Gas

Integrated process of coal pyrolysis with catalytic cracking over carbon-based catalysts (char or activated carbon) was used for improving tar and gas quality. Pyrolysis manner and reaction conditions were examined in a fix-bed reactor, and the role of carbon-based catalyst in integrated process were explored.Different kinds of pyrolysis manner were examined in N2 atmosphere. The results showed that the integrated process of coal pyrolysis with catalytic cracking possessed lighter tar and higher gas yield comparing with coal pyrolysis alone. Activated carbon presented better cracking activity than char. The light tar content (boiling points< 360℃) reached to 76% when activated carbon was used as the catalyst at 650℃, and pyrolysis gas yield increased by 32%. Catalytic cracking of carbon-based catalyst mainly played a role of converting heavy tar fractions into light tar fractions and more pyrolysis gas. The appropriate reaction conditions of integrated process of coal pyrolysis with catalytic cracking over activated carbon in N2 atmosphere were 650 ℃, with 20% activated carbon of SM coal and 100 ml/min N2 flow rate.The blank experiment with the same height of SiO2 and TG/DTG、BET、FT-IR indicated that except for catalytic cracking, carbon-based catalyst also played other roles in the integrated process:Thermal cracking had a slight contribution to tar cracking; Adsorption of activated carbon not presented obviously in the process of catalytic cracking, while the carbon-based catalyst with high specific surface area and pore volume presented better cracking activity owing to effective collision of tar and active sites. In addition, oxygen-containing functional group in carbon-based catalyst had some contribution to integrated process.The pyrolysis atmospheres have great influences on tar and pyrolysis gas in the integrated process. The results showed that the effect of atmospheres on lighten tar was CH4-CO2> H2> N2. The content of phenol oil and naphthalene oil improved obviously when CH4-CO2 or H2 were used as the atmosphere. Comparing CH4-CO2 atmosphere with CH4-CO2 reforming atmosphere in the integrated process of coal pyrolysis with catalytic cracking over activated carbon, the light tar content was almost no difference. While the integrated process in CH4-CO2 reforming atmosphere could acquire higher tar yield than CH4-CO2 atmosphere.