Catalytic co-pyrolysis of walnut shell and high-density polyethylene (HDPE) using nickel-doped gamma alumina spent adsorbent derived catalyst: Kinetics, thermodynamic and prediction modelling using artificial neural network (ANN) approach

Abstract

The present study is focused on evaluating the catalytic effect of nickel impregnated spent aluminium hydroxide nanoparticle (AHNP) adsorbent-based catalyst in the co-pyrolysis of walnut shell and high-density polyethylene (HDPE). The analysis was conducted through kinetic and thermodynamic assessments. Specific kinetic parameters, such as activation energy and pre-exponential factor, along with thermodynamic parameters, including entropy, enthalpy, and Gibbs free energy, was estimated using iso-conversional models such as Ozawa Flynn Wall (OFW), Kissinger Akahira Sunose (KAS) and Starink model. Thermogravimetric analysis of pyrolysis of walnut shell, HDPE, blend of walnut shell and HDPE (1:1) and blend of feedstock with catalyst (1:1) was conducted at different heating rates of 10–40 °C/min respectively. The results showed that the incorporation of nickel doped gamma alumina (NAO) catalyst lowered the activation energy (E_a) of co-pyrolysis of walnut shell and HDPE by 28 % as calculated by KAS method. Moreover, artificial neural network (ANN) was also applied for the predictive modelling of the degradation of walnut shell and HDPE where high regression (R≈0.99) as well as low mean squared error (<10⁻⁵) illustrated the accurate prediction of complex biomass and plastics degradation by the ANN model. Therefore, catalyst derived from waste AHNP has considerable potential to be utilized for the co-pyrolysis of biomass with plastics, enhancing the process's cost effectiveness, environmental sustainability, and renewability.