Effect of desilication process on natural zeolite as Ni catalyst support on hydrodeoxygenation of palm fatty acid distillate (PFAD) into green diesel

Abstract

Natural zeolite (NZ) from desilication and activation was prepared to support the Ni catalyst. The catalyst was utilized for the hydrodeoxygenation (HDO) of the palm fatty acid distillate (PFAD) into green diesel. Desilication using sodium hydroxide (NaOH) solution increases the porosity, surface area, and acidity of the natural zeolite, thus increasing the catalytic activity. This study aims to determine the effect of the NaOH concentration utilized in the desilication process on the characteristics of support and catalytic activity of the Ni/NZ catalyst. Additionally, pure Ni and Ni/NZ without desilication were also investigated for comparison. NZ underwent desilication by varying the concentration of NaOH (0.5, 1, and 2 N). Desilicated zeolite was then activated using a 1 M ammonium acetate solution and impregnated with Ni metals. The desilication NZ increases the acidity and surface area at a low NaOH concentration, while the zeolite structure (clinoptilolite) is still intact. Therefore, the catalytic activity of the catalyst was also increased compared to Ni and Ni/NZ catalysts without desilication. Conversely, a higher concentration of NaOH decreases the Si/Al ratio, acidity, and surface area of support. As a result, the catalytic activity of the catalyst decreases, as evidenced by the reduced liquid product in the hydrodeoxygenation of PFAD. The Ni/NZ0.5 catalyst revealed optimal catalytic activity with a liquid fraction and green diesel selectivity of 83.64% and 92.74%, respectively.