K+ trapped kaolinite (Kaol/K+) as low cost and eco-friendly basic heterogeneous catalyst in the transesterification of commercial waste cooking oil into biodiesel

Abstract

Raw kaolinite mineral was modified by alkaline potassium hydroxide solution at 373.15 K for 8 h and calcinated at about 573.15 K to produce a new low cost and eco-friendly heterogeneous catalyst for efficient transformation of commercial waste cooking oil into biofuels (biodiesel). The synthetic catalyst was defined as K+-trapped kaolinite (Kaol/K+) and characterized by XRD, TEM, SEM, BET, and FT-IR in addition to the investigation of other properties as ion exchange capacity and total basicity. Different operating parameters were involved for the transesterification system for waste cooking oil in the presences of Kaol/K+ as a basic catalyst. 343.15 K temperature, 14:1 methanol-to-oil molar ratio, 180 min conversion time, and 15 wt% catalyst loading were defined as the best conditions for maximum production of biodiesel from waste cooking oil with yield percentage of 94.76%. The basicity and catalytic activity of kaolinite/K+ enhanced greatly with increasing the concentration of KOH solution up to 30% and then decreased again with the studied higher concentrations (35% and 40%). The catalyst can be reused for five runs using distilled water, methanol and acetone as washing reagents with clear preferences for organic solvents. The properties of the produced biodiesel in this study match the requirements of ASTM D-6571 specification and EN 14214 specification as the international standards for biodiesel in the world.