K- and Cu-doped CaTiO3-based nanostructured hollow spheres as alternative catalysts to produce fatty acid ethyl esters as potential biodiesel

New functional polycation oxide-type catalysts were synthesized by the ultrasonic spray-pyrolysis method. The catalytic activity in the production of fatty acid ethyl esters (FAEE's) using soybean oil was studied. Catalysts are conformed by nanostructured hollow spheres of low density with a stoichiometric formula Ca1-xKxTiCux/2O3. The influence of the substitutional ratio (x) upon the catalytic activity was verified. The Ca1-xKxTiCux/2O3 sample with x = 0.3 showed the highest activity with a yield up to 89 % to produce fatty acid ethyl esters (FAEE's) after 24 h reaction using 15 wt.% catalysts, 120 degrees C and 40 bars. The enhancement in the activity was ascribed to the substitution of the Ca+2 sites by K+ and Ti+4 by Cu+2 and to the hollow morphology favoring a more effective interaction between the soybean oil and the active basic sites of the catalysts.