Investigation of In-Situ and Ex-Situ Catalytic Pyrolysis Upgrading of Pine Using Thermo-Gravimetric Analysis and a Fixed-Bed Reactor System

To determine the influence of process parameters on the preparation of aromatic compounds from biomass by catalytic pyrolysis, in situ and ex situ catalytic pyrolysis processes were compared using TGA and a fixed-bed reactor. At the same time, BET, TEM and XRD were used to analyze the characteristic of HZSM-5 catalyst, and GC-MS, FTIR and elemental analysis were used to analyze the composition and selectivity of bio-oil. The results showed the following: catalyst addition can clearly promote the dehydration reaction of the initial stage, which can effectively reduce the activation energy and the steric hindrance effect, accelerate the reaction rate, increase the conversion of wood powder (the conversion rate increased from 70.39% to 94.07%), and reduce the amount of residual carbon; for different catalytic pyrolysis processes, the composition and selectivity of the bio-oil vary: higher permanent gas yields, higher aromatic contents and a higher selectivity to benzene and toluene in the bio-oil were observed from the ex situ catalytic pyrolysis upgrading, and the deoxidation effect was better, however, higher yields of the bio-oil and a higher selectivity to C10+ polycyclic aromatic hydrocarbon were recorded during in situ catalytic pyrolysis; moreover, a higher temperature is conducive to the dealkylation reaction, and it increased the selectivity of non-substituted aromatics, while a low temperature caused the alkylation reaction to increase, which increased the selectivity of the substituted aromatics; at a pyrolysis temperature of 450 degrees C and a catalytic temperature of 500 degrees C, the ratio of the biomass to catalyst was 1: 2, the contents of single ring aromatics and residues reached 69% and 28.95%, respectively, and the calorific value reached 31.74 MJ/Kg; in comparison, at a pyrolysis temperature of 450 degrees C, the in situ catalytic pyrolysis of biomass only produces 27.51% and 30.01% light aromatic and residues, respectively.