Kinetics study of catalytic pyrolysis of polystyrene polymer using response surface method

The present study investigates the kinetics of polystyrene catalytic pyrolysis using the response surface method. Polystyrene is one of the most widely used polymers that decomposes slowly in the environment. Two models (nth-order reaction and first-order reaction) have been employed to examine the catalytic pyrolysis process. One-liter hydrothermal reactor is filled with 100 g of polystyrene granules that have an estimated diameter of 1 mm and an Iranian natural zeolite catalyst. 100 mL of n-hexane and the catalyst are added to the reactor for improved mixing and to stop the catalyst particles from escaping. Then, the reactor is sealed and when the polymer melts down, nitrogen gas is injected with a flow rate of 100 mL/min. Three variables of time (30–120 min), temperature (100–300 °C), and the amount of catalyst (2, 4, 6 g) were selected as independent variables. For statistical analysis, the second-order model (response surface methodology) was used to find the relationship between independent and dependent variables. The results have shown that temperature and time have a significant effect on pyrolysis efficiency and the Group Method of Data Handling neural network was used to investigate the effect of parameters such as time, temperature, amount of catalyst, polystyrene amount, and pyrolysis mass volume. The findings illustrated that temperature has the greatest effect on the pyrolysis product and the results of kinetic investigation have shown that the nth-order reaction is more suitable for the kinetic justification of all experimental data because the degree of compatibility between experimental data and modeling results is higher than the first-order reaction.

Graphical abstract