Influence of crystallinity of zeolite NaX as a support for potassium catalyst in transesterification of palm oil

Zeolite NaX samples synthesized from varying hydrothermal times (HTx, x = 0, 4, 8, 12, and 24 h) were impregnated with potassium (K) to produce K/HTx as catalysts in the transesterification of palm oil with methanol. The goal of this work is to explore the influence of the crystallinity of zeolite NaX on biodiesel production. The findings from XRD, N₂ sorption, SEM-EDS, FTIR, and CO₂-TPD demonstrate that the longer hydrothermal treatment times enhance the zeolite NaX crystallinity. A pure phase of zeolite NaX was achieved from hydrothermal times of 8 h or longer. The HT0 and HT4 exhibited poor crystallinity, and consequently, the supported catalysts, K/HT0 and K/HT4, provided low biodiesel yields (29.7 % and 43.9 %, respectively) despite having similar surface area, functional groups, and morphology. The catalysts supported on fully crystallized zeolite NaX gave biodiesel yields of about 80 %. The enhanced crystallinity of zeolite increased the basicity of the K/NaX, resulting in an improved catalytic performance for the transesterification of palm oil.