载镍橄榄石催化剂对棉秆热解的影响

Influence of the nickel loaded olivine catalyst on the pyrolysis of cotton stalk

为了揭示催化剂对生物质热解过程的影响,文章以新疆棉秆为原料,研究了橄榄石及载镍橄榄石(NiO-olivine)对棉秆热解产物的影响规律,并对其物理、化学性质进行表征。研究结果表明:催化剂对生物质热解起到双重作用,一方面,促进半焦的进一步热解,提高生物质热解过程中碳的转化率和原料的利用率,另一方面,对热解焦油的裂解具有较好的催化作用,促进了焦油和甲烷的裂解/重整反应,从而提高了气体产率,H2含量提高一倍。生物质热解过程中,催化剂表面的NiO被热解气还原形成单质Ni充当活性中心;随着热解温度的升高,催化剂的催化效果更加明显;随着NiO负载量的增加,催化剂的催化活性不断增强,当负载量大于7%时,催化剂的自还原消耗大量的热解气导致产气中的H2和CO含量大幅度降低,CO2和H2O含量增加。该研究结果有助于深入了解镍基催化剂对生物质热解的影响机制,为生物质催化气化提供参考依据。

Pyrolysis reaction was the first step during the catalytic biomass gasification. Catalytic pyrolysis of the cotton stalk has been conducted in a fixed bed reactor in order to reveal the influence of catalyst during the biomass pyrolysis using olivine and NiO-olivine as a catalyst. At the same time, the physical and chemical properties of catalyst has been characterized. The result showed that the catalyst has double effect during the catalytic biomass pyrolysis： On the one hand, carbon conversion was promoted due to further pyrolysis of the residual char by the catalyst; On the other hand, it has catalytic effect to cracking/reforming reaction of tar and methane witch promotes the gas yield and H2 concentration. The catalytic effect of those catalyst has been increased with the increasing temperature.The NiO at the surface of the NiO-olivine catalyst was reduced to metal Nias the active center by the pyrolysis gas during pyrolysis. The catalytic activity of NiO-olivine has been increased with the increasing NiO loading ratio. However, when the NiO load is higher than 7%, the self-reduction of the catalyst consumes large amount of pyrolysis gas, results significant reduction in H2 and CO in the gas production and increases the content of CO2 and H2O. The results of this study can provides valuable information to understand the influence mechanism of nickel-based catalysts during biomass pyrolysis and provides reference for the catalytic gasification of biomass.