Origin of hydrogen in products derived from catalyzed co-pyrolysis of glucose and polypropylene via deuterium labeling using TG-FTIR

Catalytic co-pyrolysis of biomass and hydrogen donors is one of the important ways to improve the quality of biooil. The hydrogen transfer pathways in co-pyrolysis are significant yet remain vague. In this study, an isotopic labeling method to label glucose (G) with deuterium (D) atoms was used to trace the hydrogen. The results show the catalysts influence the hydrogen transformation significantly and selectively. The shift of the infrared (IR) peaks proves that the hydrogen atoms in products- phenols, alcohols, carboxylic acids, aldehydes, and olefins contain both hydrogen from polypropylene (PP) and deuterium from G. While the hydrogen in aromatic rings,- CH3 and- CH2 all come from polypropylene. Furthermore, the deuterium atoms from G only enter the olefin products with catalyst potassium chloride (KCl) or activated carbon (AC). On the other hand, the oxygenated compound products mainly contain hydrogen atoms from polypropylene with any of the three catalysts. The potassium chloride helps the hydrogen from polypropylene transfer to the products of mainly phenols, aldehydes and alcohols. The AC transfers the hydrogen from polypropylene to the products of carboxylic acid, aldehydes, and phenols. For the ZSM-5, it helps the hydrogen from polypropylene transfer to the products of carboxylic acid and aldehydes. The results of this study are useful for improving the effective hydrogen content of the mixed pyrolysis reaction of biomass.