Catalytic Fast Pyrolysis of Prairie Cordgrass Lignin and Quantification of Products by Pyrolysis-Gas Chromatography-Mass Spectrometry

Organosolv lignin extracted from prairie cordgrass (PCG) was pyrolyzed in the presence of HZSM-5 and analyzed using pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). The pyrolysis products detected are primarily aromatic hydrocarbons and phenolic compounds. The effects of the HZSM-5 catalyst and pyroprobe temperature on the production of aromatic hydrocarbons and phenolic compounds were assessed quantitatively. HZSM-5 mixed with PCG lignin at a ratio of 5:1 and a pyroprobe temperature of 650 degrees C maximized the production of the detected aromatic hydrocarbons, resulting in about a 13 wt % yield of PCG lignin. At these conditions, the products detected are estimated to have a total oxygen content of about 1.4% and a higher heating value of 49 MJ/kg, although the detected compounds may constitute less than a quarter of the volatiles released during the pyrolysis of PCG lignin. Toluene and p-xylene were the two most abundant hydrocarbons formed in the presence of HZSM-5, with yields of 3.6 and 3.2% of the pyrolyzed lignin, respectively. This provides great potential for replacing a sizable portion of production for the two aromatic hydrocarbons from fossil sources worldwide. In the presence of HZSM-5, the largest total yield of the aromatic hydrocarbons from the pyrolysis of organosolv lignin extracted from aspen trees is almost twice as much as that produced from the pyrolysis of lignin extracted from PCG, a perennial grass. On the other hand, in the presence of catalyst, the volatile compounds detected from the pyrolysis of PCG lignin contain less oxygen than those for aspen lignin, thus resulting in a better quality product with enhanced higher heating value (HHV).