Catalytic Pyrolysis of Cotton Stalk by K2CO3 and Its Potassium-Containing Semi-Coke Products Used for Catalytic Degradation of Tar
Tar produced during biomass pyrolysis has caused serious harm to equipment and environment.Exploring the influence mechanism of K2CO3 catalytic pyrolysis of cotton stalk to generate tar and the catalytic degradation of tar by potassium-containing semi-coke is of great significance for realizing efficient utilization of biomass energy.In this work,the catalytic pyrolysis characteristics of cotton stalk were studied with a horizontal fixed bed catalytic pyrolysis experimental device at 600℃.The results showed that the addition of K2CO3 could inhibit tar production.When the addition of K2CO3 was 7.5%(mass fraction),the tar yield decreased from 43%to 33%(without K2CO3),and the content of aromatic hydrocarbons in tar increased.The molecular pyrolysis results of the hemicellulose model compound 4-O-methylglucuronic acid based on density functional theory show that potassium activates the side chain groups of 4-O-methylglucuronic acid,which makes it easier to remove-OH.Using toluene as the model compound of tar,the heterogeneous degradation of toluene by cotton straw semi-coke was studied.It was found that the addition of K2CO3 increased the specific surface area and adsorption sites on the semi-coke surface,which enhanced the degradation and condensation reaction of toluene.In conclusion,the addition of K2CO3 can reduce tar production at the initial stage of pyrolysis,and the recovery of potassium-containing semi-coke as a catalyst can strengthen tar degradation,providing a new idea for improving the utilization rate of cotton stalk resources.
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