Kinetic and Thermodynamic Analyses of Poly (3‐Hydroxybutyrate‐co‐3‐hydroxyvalerate) Pyrolysis by Model‐Free and Gaussian Deconvolution Methods

The study reports the deconvolution of intricate pyrolysis of PHBV into four parallel sub-reactions via the Gaussian method. Model-free methods are used to gain activation energy Ea and pre-exponential factor lnA while the Avrami-Erofeev type reaction models are the most suitable for the global pyrolysis and sub-reactions. Thermodynamic parameters and thermal lifespan are evaluated for practical application considerations.

Abstract

Pyrolysis of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) has been investigated in detail by means of thermogravimetric measurements and theoretical kinetic parameterization. The novelty of present work is that the Gaussian deconvolution method is attempted for the first time to perform kinetic study of PHBV pyrolysis along with thermodynamic analysis. The results acquired from 5 to 20 K/min demonstrate that PHBV was mainly pyrolyzed within 500 ∼ 950 K. The pyrolysis features were characterized by some specific pyrolysis indexes and kinetic analysis was conducted by using various methods. Using the model-free methods, the activation energy Ea and pre-exponential factor lnA for global PHBV pyrolysis are 118.1 ∼ 189.2 kJ/mol and 18.43 ∼ 24.83 min-1, separately. By the Gaussian multi-peak fitting method, the PHBV pyrolysis has been deconvoluted into four parallel sub-reactions. Following Coats-Redfern method, the Avrami-Erofeev type reaction models are found to be the most suitable for describing the global pyrolysis process and sub-reactions. With kinetic parameters, the fittings against experimental results are satisfactorily achieved. Finally, the evaluations of thermodynamic parameters and thermal lifespan are made for practical application considerations. Overall, our results can be very helpful for deeply understanding intricate pyrolysis of PHBV waste and advancing bioenergy development.

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