fig2
From: Toward CO2-neutral biodiesel production: industrial challenges and advances in CaO-based catalysts
Figure 2. SEM images of (A) CaO; (B) SiO2; (C) CaO/SiO2 (fresh); (D) CaO/SiO2 (used). Reproduced from ref.[232] under a Creative Commons Attribution 3.0 Unported License (CC BY 3.0).
