Nowadays, waste plastics made a signifi cant environmental problems. Chemical converting of the polymers to valuable liquids

is a promising method to solve the problem and make excellent benefi t. This study investigates the utilization of kaolin,

a natural resource, for synthesizing zeolite Na-A and signifi cance of the catalyst crystallinity on the catalytic cracking of a

50:50 mixture of polystyrene (PS) and low-density polyethylene (LDPE). This research aims to identify the optimal hydrothermal

conditions for producing crystalline zeolite Na-A and evaluate the eff ect of crystallinity of synthesized zeolite Na-A

on production of liquids. A central composite design (CCD) model is employed to achieve this, selecting three independent

variables: hydrothermal temperature (80, 85, 90, 95 and 100 °C), the molarity of the alkaline solution (NaOH concentration

= 1,2,3,4 and 5 molar), and hydrothermal time (8, 10.43, 14, 17.56 and 20 h). Fourier transform infrared spectroscopy

(FTIR) determines the functional groups which proves the presence of sodium aluminosilicate in the synthesized zeolite.

The crystallinity of the produced zeolite Na-A is evaluated through X-ray diff raction (XRD) analysis, optimizing the results

using the CCD model. Scanning electron microscopy (SEM) reveals well-formed cubic crystalline structures of zeolite Na-A.

The optimum conditions for polymer cracking are determined as hydrothermal temperature of 89 °C, a hydrothermal time

of 13 h, and a NaOH molarity of 2.8, while predicted liquid production was obtained 81%. The analysis of ANOVA indicates

that the designed model based on CCD calculations is valid for prediction of the process. Finally, gas chromatography

with fl ame ionization detection (GC-FID) is employed to characterize the main resulting value-added components (styrene,

toluene, and ethylbenzene) under optimum conditions.