The effects of catalysts on the conversion of organic matter and bio-fuel production in the microwave pyrolysis of sludge at different temperatures

[Display omitted] •CaO was a better catalyst for the production of bio-gas while Fe2O3 for bio-oil.•The best quality of bio-oil could be catalyzed by CaO at 800°C.•The maximum bio-gas production could both be catalyzed by CaO and Fe2O3 at 900°C.•CaO was more suitable for oriented catalytic production of H2 while Fe2O3 for CH4. Adding catalyst could improve the yields and qualities of bio-gas and bio-oil, and realize the oriented production. Results showed that the catalytic gas-production capacities of CaO were higher than those of Fe2O3, and the bio-gas yield at 800°C reached a maximum of 35.1%. Because the polar cracking active sites of CaO reduced the activation energy of the pyrolysis reaction and resulted in high catalytic cracking efficiencies. In addition, the quality of bio-oil produced by CaO was superior to that by Fe2O3, although the bio-oil yield of CaO was relatively weak. The light bio-fuel oriented catalytic pyrolysis could be realized when adding different catalysts. At 800°C, CaO was 45% higher than Fe2O3 in aspect of H2 production while Fe2O3 was 103% higher than CaO in aspect of CH4 production. Therefore, CaO was more suitable for H2 production and Fe2O3 was more suitable for CH4 production.