In this study, 13X zeolite was successfully synthesized from low-grade natural kaolin via alkali fusion followed by hydrothermal treatment, without extra Si source or dealumination. Fusion with NaOH, followed by hydrothermal reaction, kaolinite, illite and trace of quartz in kaolin sample were converted into zeolite. The effects of various factors during the synthesis process such as NaOH addition amount, crystallization time and temperature on the crystalline products were studied. The optimum synthesis conditions to get purity 13X zeolite were found to be alkali fusion of kaolin with the weight ration of NaOH/kaolin = 2.0 at 200 degrees C for 4 h, and crystallized at 90 degrees C for 8 h after homogenization by agitated at 50 degrees C for 2 h. The product was characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and N-2 adsorption-desorption. The BET surface area of the product was found to be 326 m(2) g(-1). It can be concluded that the study provides the basic data and the process for extensive and efficient utilization of low-grade natural kaolin. (C) 2013 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.