A strategy of using recycled char as a co-catalyst in cyclic in-situ catalytic cattle manure pyrolysis for increasing gas production

摘要

Cattle manure is a major livestock waste in agroecosystem, and in-situ catalytic pyrolysis is considered as a potential technology for its disposal. In order to increase the gas production during cattle manure pyrolysis and alleviate the problem of frequent regeneration-separation of the in-situ catalyst, a strategy of in-situ catalytic pyrolysis was proposed in this work, in which the pyrolytic char product was not separated from the pyrolysis catalyst of NiO/γ-Al_2O_3 but mixed with it and recycled for several times as the co-catalyst for cattle manure pyrolysis instead. Adopting this strategy, it was observed that the mixed-type catalyst could lead to 70% increase in gas production and 82% promotion in syngas energy conversion rate compared with the circumstance of no catalyst added. Through different means of characterization, it was found that there are synergistic effects between char and NiO/γ-Al_2O_3, which enhance the catalytic performance of catalyst. On one hand, during the pyrolysis process, char can translate NiO into Ni that has higher cracking activity through in-situ reduction. On the other hand, due to its rich porous texture and large pore volume, char can act as an additional adsorbent for the reactants. Based on the experimental results of this work, the proposed strategy of cyclic in-situ catalysis with the recycled char as the co-catalyst can be a promising scheme in the practical biomass pyrolysis process for gas production.