دانلود رایگان مقاله ارزش افزوده مواد شیمیایی تکامل ارگانونیتروژن از تجزیه حرارتی کیتین و کیتوزان

Abstract

Thermogravimetric characteristics of chitin and chitosan and their potentials to produce value-added organonitrogen chemicals were separately evaluated via TG/DSC-FTIR and Py-GC/MS. Results shown that chitin had the better thermal stability and higher activation energy than chitosan because of the abundant acetamido group. Furthermore, the dominated volatilization in active pyrolysis of chitin contributed to its endothermic property, whereas the charring in chitosan led to the exothermal. During fast pyrolysis, the acetamido group in chitin and chitosan was converted into acetic acid or acetamide. Typical products from chitosan pyrolysis were aza-heterocyclic chemicals, i.e. pyridines, pyrazines, and pyrroles, with the total selectivity of 50.50% at 600 °C. Herein, selectivity of pyrazine compounds was up to 22.99%. These aza-heterocyclic chemicals came from the nucleophilic addition reaction of primary amine and carbonyl. However, main reaction during chitin pyrolysis was ring-opening degradation, which led to the formation of acetamido chemicals, especially acetamido acetaldehyde with the highest selectivity of 27.27% at 450 °C. In summary, chitosan had the potential to produce aza-heterocyclic chemicals, and chitin to acetamido chemicals.

4. Conclusions

Chitosan had the potential to produce aza-heterocyclic chemicals, whereas chitin to acetamido chemicals. Pyridines, pyrazines, and pyrroles evolution from chitosan pyrolysis, whose total selectivity was 50.50% at 600 ◦C, profited from the nucleophilic addition reaction of primary amine and carbonyl. Herein, selectivity of pyrazine compounds was up to 22.99%. Moreover, acetamido chemicals from chitin pyrolysis were released through the ringopening degradation, especially acetamido acetaldehyde with the highest selectivity of 27.27% at 450 ◦C. All these differences were caused by the different content of acetamido group, which also led to the better thermal stability andhigher activationenergy of chitin, as well as its endothermic property during active pyrolysis.