Sodium titanates were evaluated as heterogeneous catalysts for biodiesel production. Materials were prepared using an experimental design considering NaOH and TiO2 concentrations and hydrothermal and calcination temperatures as input variables. Materials characterization was carried out by DRX-Rietveld refinement, CO2-TPD, and XPS. Statistical analysis of the experimental results indicates that the calcination temperature is the most influential factor in the formation of sodium titanates with high catalytic performance in transesterification reactions. Further analysis of the oil-to-biodiesel conversion revealed that the catalytic activity of sodium titanates is directly correlated to the catalyst associated species and to the density of medium-strong basic sites on the surface of the material, obtaining up to 95% conversion to biodiesel at 60 °C using 3.6% weight catalyst with respect to oil.

In the industry, sodium carbonate is used to prepare sodium silicate; however, this process generates great volumes of CO 2 . In this work, sodium hydroxide has been proposed to prepare sodium silicate using natural sand. Two experimental variables were considered, sodium hydroxide concentration and temperature to prepare sodium silicate. Results show the formation of sodium silicate with a NaOH:sand ratio = 1.1 at 550°C. Moreover, an economical revision was achieved to compare costs of sodium silicate with sodium hydroxide and sodium carbonate. The use of sodium hydroxide permits to decrease CO 2 emissions generated in the decomposition of sodium carbonate. Additionally, the sodium silicate prepared herein was used to synthesize a zeolite type material, SBA-15. SBA-15 obtained has similar characteristics than the commercial mesoporous material. The use of sodium silicate prepared with non-pure sand for preparing mesoporous materials is an economical and friendly environmental alternative.

In this work, the synthesis of sodium titanate for the biodiesel production was evaluated with emphasis on the synthesis parameters of titanates in the conversion of vegetable oil to biodiesel. Sodium titanate catalysts were synthesized via sol–gel hydrothermal method and tested as heterogeneous catalysts for biodiesel production, using a factorial design 2k. Four experimental factors were considered: NaOH concentration, hydrothermal temperature, TiO2/NaOH ratio, and calcination temperature, using as response variable the catalysts activity in soybean oil conversion to biodiesel. Titanates were characterized by XRD, SEM, and N2 physisorption techniques. The presence of tri and hexatitanate were confirmed. Trititanate was the most efficient in the conversion of soybean oil to biodiesel, achieving around 80% with an alcohol:oil molar ratio of 6:1 at 55°C for 5 hr and 300 rpm. Among the trititanate catalysts, the best performing sample showed a surface area of 217 m2/g with a porous size average of 4.8 nm related to nanotube structure with inter and intra particle mesoporosity. Conditions to prepare the efficient performing catalyst were as follows: NaOH concentration, 7.5 M; hydrothermal temperature, 130°C; TiO2/NaOH ratio, 0.06 g/mL; and calcination temperature, 600°C.