Study on Pyrolysis of Pine Sawdust with Solid Base and Acid Mixed Catalysts by Thermogravimetry-Fourier Transform Infrared Spectroscopy and Pyrolysis-Gas Chromatography/Mass Spectrometry

Catalytic fast pyrolysis of biomass with microporous ZSM-5 to produce aromatics is a promising technology for biomass use. To improve the aromatic yield, meso- and macroporous [CaO, MgO, and fluidized catalytic cracking (FCC)] catalysts were added in a microporous catalyst (ZSM-5). The added catalysts can crack large-molecule oxygenates from pyrolysis into small-molecule oxygenates, and then these small-molecule oxygenates were converted to aromatics over ZSM-5. The experiments of pine wood catalytic pyrolysis with two mixed catalysts were performed and analyzed using thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The TG-FTIR results show that CaO and ZSM-5 mixed catalysts produced more aromatic rings and C-H bonds than pure ZSM-5. The Py-GC/MS results show that CaO and MgO mixed with ZSM-5 improved the aromatic yield significantly. The maximum aromatic yield that boosted 30% of that with pure ZSM-5 was obtained with CaO as the additive. It was obtained with a biomass/CaO/ZSM-5 mass ratio of 1:4:4. According to the disposal mode of feedstock and two catalyst studies, the completely separated mode of feedstock, CaO, and ZSM-5 (mode 3) produced the highest yield of indene and its derivatives and other hydrocarbons. This paper provides a simple way to improve the aromatic yield from biomass catalytic pyrolysis.