Insight into the green doping of clinoptilolite with Na+ ions (Na+/Clino) as nanocatalyst in the conversion of palm oil into biodiesel; optimization and mechanism.

The critical demand for eco-friendly, renewable, and safe energy resources is essential issue encountering in the contemporary world. The catalytic transesterification of plant oils into biodiesel was assessed as promising technique to provide new forms of clean and safe fuels. Natural clinoptilolite was doped with Na+ ions by green chemical reactions suiting sodium nitrite and green tea extract producing novel modified structure (Na+/Clino). The Na+/Clino product is of enhanced total basicity (6.41 mmol OH/g), ion exchange capacity (387 meq/100g), and surface area (312.7 m2/g) which qualifies it as a potential basic catalyst for the transesterification of palm oil. The transesterification tests were assessed statistically by the response surface methodology and the central composite design. Considering the interaction effect of the affecting factors with each other, the synthetic Na+/Clino achieved 96.4 % as experimental biodiesel yield after 70 min at 100 oC in the presence of 2.75 wt., % catalyst loading, and 12.5:1 methanol/palm oil ratio. Based on the optimization function of the statistical model, the performance of Na+/Clino can be enhanced theoretically to increase the yield to 98.2 % by expanding the test time to 85 min and the loading value to 3 wt., %. The resulted product over Na+/ClinO is of adequate technical properties considering the international levels for standard biodiesel (EN 14214 and ASTM D-6751). Finally, the prepared green Na+ doped clinoptilolite is of excellent recyclability as a heterogeneous basic catalyst and displayed higher efficiency than several species of previously studied heterogeneous and homogenous catalysts.