Microwave pyrolysis characteristics and product of Chlorella vulgaris under compound additives and optimization by Box-Behnken design

Microwave-assisted pyrolysis of Chlorella vulgaris was carried out under compound additives, which contained catalyst (ZSM-5) and microwave absorbent (graphite). The effects of three independent variables (Si/Al ratio of ZSM-5, additives amount and catalyst ratio) on the weight loss characteristics, product yield and energy consumption were investigated. Response Surface Methodology (RSM) coupled with Box-Behnken Design (BBD) was used to optimize pyrolysis time (T-s) and bio-oil yield (B-o) of Chlorella vulgaris pyrolysis under three independent variables. The results showed that compound additives can promoted the pyrolysis progress and increased the bio-oil yield. Besides, compound additives can also reduce the energy consumption of bio-oil production in most cases. The predicted results showed that optimal T-s and B-o were 3550s and 22.70%, respectively. GC-MS analysis further revealed that compound additive has stronger effect on denitrogenating than single additive, which is of great significance in alleviating nitrogen oxide pollution caused by bio-oil with high nitrogen content.

Automated summary

Through the addition of compound additives (catalyst and microwave absorbent), the microwave-assisted pyrolysis of Chlorella vulgaris can be promoted, leading to increased bio-oil yield and reduced energy consumption. Optimized results show that higher efficiency can be achieved under specific conditions.