Development of reusable Ni/γ-Al₂O₃ catalyst for catalytic hydrolysis of waste PET bottles into terephthalic acid

In order to efficiently recycle waste polyethylene terephthalate (PET) bottles, this study aimed to enhance the hydrolysis process to convert PET bottle into valuable terephthalic acid (TPA) by developing effective and reusable Ni/γ-Al₂O₃ catalysts. A series of Ni/γ-Al₂O₃ catalyst was prepared by the impregnation method with different Ni loadings (5–15 wt%) and was characterized by various techniques including XRD, SEM-EDX, and N₂ adsorption-desorption. The prepared catalysts were employed in the catalytic hydrolysis of PET under varied influencing factors, namely reaction temperature (220–280 °C), reaction time (20–60 min), and Ni loading. The response surface methodology (RSM) was used to optimize the operating condition to produce the maximum TPA yield, and the optimal values were determined as follows: reaction temperature = 267.07 °C, reaction time = 48.54 min, and Ni loading = 12.90 wt%, giving the highest TPA yield of 97.06%. The R ², F-value, and P-value of the analysis of variance (ANOVA) were 0.9982, 424.96, and <0.0001, respectively, indicating a good fit of the model. The results from XRD and FTIR measurement of the produced TPA indicated the high purity and comparable chemical structures to the TPA standard. In addition, the 12.9Ni/Al catalyst exhibited high catalytic activity in repeated cycles of hydrolysis process of PET and could be regenerated by calcination to restore its catalytic activity. This finding could be a promising alternative for an effective TPA recovery from waste plastic bottles.