Insight into the catalytic properties zeolitized kaolinite/diatomite geopolymer as an environmental catalyst for the sustainable conversion of spent cooking oil into biodiesel; optimization and kinetics

Inorganic zeolite/geopolymer composite (Z/GP) was synthesized by controlled zeolitization of synthetic geopolymer from kaolinite and diatomite to be used as a potential catalyst in the transesterification of commercial spent cooking oil (SCO). The Z/GP composite demonstrates promising microstructural properties (106 m(2)/g surface area and 4.2 nm average pore diameter) and chemical structural enrich in OH and Na+ ions as active basic and catalytic centers. The Z/GP composite as catalyst was applied in the transesterification of SCO according to suggested experiment conditions from statistical design which was built based on the Response Surface Methodology. The measured biodiesel yield from SCO over Z/GP catalyst is 98.1% at experimental conditions of 40 degrees C as temperature, 90 min as time, 12:1 as methanol/SCO ratio, and 3.25 wt, % as Z/GP loading value. The theoretical optimization function of the statistical design suggested potential enhancement for the performance of the reaction to achieve a yield of 99% by adjusting the values of the studied factors at 54.9 degrees C, 81.9 min, at 12:1, and 3.48 wt, % for the temperature, time, methanol/SCO ratio, and Z/GP loading. The physical properties of the produced SCO-based biodiesel over Z/GP demonstrate the suitability of the product to be used as biofuels considering the criteria to international standards. The kinetic properties of the transesterification reactions of SCO over Z/GP catalyst follow the Pseudo-First order kinetic assumption and occurred with low activation energy. Finally, the synthetic Z/GP as a solid basic catalyst is of significant reusability and reused five times with remarkable biodiesel yields.

Automated summary

The synthesized Z/GP composite as a catalyst in transesterification of commercial spent cooking oil (SCO) shows promising performance, with potential for higher yield through parameter optimization. Experimental results demonstrate that the biodiesel produced from Z/GP composite meets international standards, with kinetic properties following the Pseudo-First order assumption and low activation energy. Additionally, the synthetic Z/GP as a solid basic catalyst exhibits significant reusability, with remarkable biodiesel yields over five repeated uses.