(210b) Catalytic Pyrolysis of Chitin over H-ZSM-5
Approximately 6â8 million tons of waste crustacean shells (i.e., crab, lobster, and shrimp shells) are produced annually from seafood processing facilities around the world. Among them, more than 66,000 tons of waste lobster shells are produced in New England alone. More than 40% of crustacean waste by mass consists of chitin, a long chain polymer of N-acetylglucosamine. It is also the second most abundant natural biopolymer in the world behind cellulose. In this work, catalytic pyrolysis of chitin over H-ZSM-5 solid acid catalyst was conducted using a custom-made batch reactor system. The effects of catalyst loading, reaction temperature, and reaction time were systematically studied. Our experiments show that three distinct phases of pyrolysis products exist: solid char, solid condensate, and volatile compounds. Analysis of molecular composition of non-soluble solid condensate suggests that the condensate likely consists of nonvolatile, insoluble molecules with amine, acid, or hydroxyl functional groups. Increase in catalyst loading and a reaction temperature above 450 oC both favor deoxygenation, resulting in increase in solid condensate yields and its oxygen content. On the contrary, reduced char yields was observed at higher catalyst loading and higher reaction temperature, with the elemental composition of char being more carbon and nitrogen rich and oxygen deficient. No significant effect was found for reaction time longer than 15 min, suggesting that chitin pyrolysis is a rapid process and our results represent equilibrium compositions. This work demonstrates that catalytic pyrolysis of chitin could be an energy efficient pathway to promote the production of nitrogen containing char and value added nitrogen-containing products from crustacean seafood waste.