Aldehydes 1 Biodiesel 1 Catalytic esterification 1 Catalytic performance 1 Condensation 1 Condensation reactions 1 Efficient catalysts 1 Esters 1 Fatty acids 1 Feedstocks 1 Free fatty acids 1 Fuel additives 1 Functionalizations 1 Functionalized silica 1 Furfural 1 Heterogeneous acid catalysts Ketones 1 Levulinic acid 1 Nanocatalysts 1 Nanoparticles 1 Renewable feedstocks 1 Reusability 1 Silica 1 Silica nanoparticles 1 Silicon 1 Structural characterization 1 Sulfonic acid catalysts 1 biofuel 1 biomass 1 catalysis 1