Catalytic pyrolysis of coconut shell: a study on product distributions, optimized response surface methodology, and catalytic mechanism of bio-oil production

The purpose of this research is to study the mechanism of catalytic pyrolysis of coconut shell in a microwave pyrolysis reactor, explore the effect of catalytic pyrolysis process parameters on the quality and yield of liquid products, and optimize the pyrolysis process parameters using response surface methodology with Box-Behnken design (RSM-BBD). The process parameters of catalytic pyrolysis are reaction time, heating rate, temperature, nitrogen flow rate, and the operating ranges are 5–20 min, 15–30 °C/min, 400–700 °C, 50–200 ml/min. The three factors of heating rate, temperature, and nitrogen flow rate were used as independent variables, and the relative contents of hydrocarbons and phenols in bio-oil were used as response values to construct the model. For both cases, the quadratic model has proven the reliability. The relative selectivity of hydrocarbons and phenols of the determination coefficient (R 2 ) is 0.9852 and 0.9373, respectively, which proves that the model has a good fit. The best relative contents of hydrocarbons and phenols obtained by fitting are 40.20 area% and 71.33 area%, and the relative contents of hydrocarbons and phenols in the bio-oil used for the verification experiment are 41.00 area% and 72.87 area%; the result is within the allowable range of error. Compared with the relative content of hydrocarbons in the bio-oil under the best single factor conditions, the relative content of hydrocarbons increased by ~ 5 area%, indicating that the response surface method can further optimize the process parameters of the experiment.