Study on catalytic pyrolysis of eucalyptus to produce aromatic hydrocarbons by Zn-Fe co-modified HZSM-5 catalysts

Eucalyptus was pyrolyzed over metal modified HZSM-5 for producing aromatics. The untreated HZSM-5 catalyst and Zn-Fe co-modified HZSM-5 were evaluated by XRD, SEM, NH3-TPD and N-2 physical adsorption. The PY-GC/MS and TGA methods were used to perform pyrolysis of eucalyptus, exploring the product distribution of eucalyptus catalytic pyrolysis and the coking characteristics of the catalysts. Experiment resulted that the products yields and composition were significantly influenced by the use of every catalysts. Under the catalysis of 1 wt.% Zn-4 wt.%Fe/HZSM-5, the yields of benzene, toluene, xylene and naphthalene were 98.3%, 80.9%, 26.4% and 49.0% higher than those catalyzed by HZSM-5 only. The difference between TG curves of after-pyrolysis and unused catalysts reflected that 1 wt.%Zn-4 wt.%Fe/HZSM-5 looks less prone to coke than 5 wt.%Fe/HZSM-5 and 5 wt.%Zn-5 wt.%Fe/ HZSM-5. Based on all the analyses of pyrolysis characteristics, it is found that eucalyptus catalytic pyrolysis to produce aromatics is feasible, and 1 wt.%Zn-4 wt.%Fe/HZSM-5 is the optimal catalyst among modified HZSM-5 in this work.