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In this work, Sn(II)-exchanged silicotungstic acid salt (i.e., Sn2SiW12O40) was synthesized and evaluated as the catalyst on the acetalization of glycerol with acetone to produce solketal, a versatile bioadditive of fuel. The Sn2SiW12O40 salt was compared to the other solid Keggin heteropoly salts (i.e., Sn3/4PMo12O40, Sn3/4PW12O40), and liquid (i.e., HCl, H2SO4 and p-toluenesulfonic acid) catalysts. Amongst the catalysts assessed, it was the most active, achieving a high conversion (ca. > 99%, after 1 h reaction at room temperature) and selective (ca. 97%) toward the formation of solketal. Moreover, the Sn2SiW12O40 salt demonstrated to be more active than acid and precursor Tin (II) chloride salt, as well as other heteropoly salts and solid supported catalysts. The effects of the main reaction variables were assessed. The Sn(II) cation, as well as the silicotungstate anion, showed being essential to convert glycerol to solketal. Insights on the reaction mechanism were performed. In a simple recycle procedure, the solketal was purified, the acetone excess recycled, and the catalyst was reused without loss activity.

In this paper, several commercial transition metal salts were tested in acetalization reactions of glycerol with acetone to produce solketal (i.e., 2,2-dimethyl-1,3-dioxolan-4-yl)methanol). Among the salts assessed, Fe(NO3)3 9⋅H2O exhibited the highest catalytic activity, virtually converting all the glycerol to solketal, with 95% selectivity in short reaction time (ca. 30 min). Ferric nitrate is inexpensive, commercially available, non-corrosive and water-tolerant Lewis acid catalyst. Although soluble, it was easily recovered through a liquid-liquid extraction process followed by the drying of the aqueous phase and reused without loss activity or selectivity. The performance of Fe(NO3)3 was compared to other Lewis and Bronsted acid catalysts. Insights on the reaction mechanism were performed aiming to verify the effect of H+ ions generated by hydrolysis of metal catalysts throughout the reactions. This process described herein is an attractive option to the Bronsted acid-catalyzed routes because it is non-corrosive, avoids products neutralization steps and allow an easy recovery and reuse of catalyst.

Herein, an efficient amphiphilic carbon catalyst produced by the reaction of bio-oil with sulfuric acid was used for the first time for the solvent-free glycerol ketalization with 2-propanone for solketal production (2,2-dimethyl-1,3-dioxolane-4-methanol) at room temperature. The catalyst synthesis, described previously, led to an amphiphilic carbon due to hydrophobic nanostructures, e.g. graphene, nanotube, nano-onions, nanographite, embedded in an amorphous carbon containing high concentration of hydrophilic oxygen and sulfonic surface groups with strong acid sites (ca. 0.3 mmol g−1). The amphiphilic catalyst promoted the formation of an emulsion from the two immiscible phases, glycerol and 2-propanone, which had a strong effect on the reaction interface and solketal yield. Glycerol ketalization at 25 °C and solvent-free showed conversions higher than 90%, using 0.6 wt% catalyst, 1:10 glycerol:2-propanone after 2 h. The catalyst can be recovered and reused four times without any significant activity loss.

In this work, the activity of Sn(II)-Keggin heteropolyacid salts (i.e., Sn3/2PW12O40 and Sn3/2PMo12O40) was investigated on the etherification reactions of glycerol with tert-butyl alcohol. Tin(II) heteropoly catalysts were easily synthesized and characterized by analyses of FT-IR/ATR, TG/DSC, MEV/EDS, XRD, BET, and potentiometric titration with n-butylamine. The activity of heteropoly salts was compared to the precursor heteropolyacids and SnSO4 catalysts. The Sn3/2PW12O40-catalyzed etherification achieved the highest tert-butyl glycerol ethers selectivity (ca. 90%) after 4 h of reaction at 363 K. The selectivity toward mono-glyceryl tert-butyl ether (i.e., an efficient surfactant) or di-tert-butyl glyceryl ether (i.e., a fuel bioadditive) can be tailored by an adequate adjustment of the reaction parameters (i.e., catalyst loading, reactant stoichiometry). Glycerol ethers were characterized by 1H and 13C NMR and infrared spectroscopy and mass spectrometry.

This work investigates the impacts on fuel consumption and exhaust emissions of a diesel power generator operating with biodiesel. Fuel blends with 5%, 20%, 35%, 50%, and 85% of soybean biodiesel in diesel oil, and fuel blends containing 5%, 20%, and 35% of castor oil biodiesel in diesel oil were tested, varying engine load from 9.6 to 35.7 kW. Specific fuel consumption (SFC) and the exhaust concentrations of carbon dioxide (CO 2 ), carbon monoxide (CO), and hydrocarbons (HC) were evaluated. The engine was kept with its original settings for diesel oil operation. The results showed increased fuel consumption with higher biodiesel concentration in the fuel. Soybean biodiesel blends showed lower fuel consumption than castor biodiesel blends at a given concentration. At low and moderate loads, CO emission was increased by nearly 40% and over 80% when fuel blends containing 35% of castor oil biodiesel or soybean biodiesel were used, respectively, in comparison with diesel oil. With the load power of 9.6 kW, the use of fuel blends containing 20% of castor oil biodiesel or soybean biodiesel increased HC emissions by 16% and 18%, respectively, in comparison with diesel oil. Exhaust CO 2 concentration did not change significantly, showing differences lower than ±3% of the values recorded for diesel oil operation, irrespective of biodiesel type, concentration and the load applied. The results demonstrate that optimization of fuel injection system is required for proper engine operation with biodiesel.

In this work, catalysts with acid and superabsorbent properties were obtained by sulfonation of expanded polystyrene and used to promote the esterification of oleic acid with ethanol. The prepared superabsorbent polymers (SAP) showed high concentration of active sulfonic acid sites (0.7–5.9 mmol acid sites g −1 ) and high water absorption capacity (445–900 g water g −1 ). It was observed that the catalytic activity increased with the number of acid site and water absorption capacity. Turnover frequencies suggested that the catalytic activity depends on the accessibility/diffusion processes determined by the crosslinks in the polymer. Commercial sulfonic acid resins and polyacrylate based superabsorbent polymers showed very low activities compared with the SAP produced. The SAP also showed higher activity compared to the homogeneous catalyst p -toluenesulfonic acid. The higher activity of the prepared SAP is discussed in terms of the acidity of sulfonic groups combined with the water absorption which shifts the esterification equilibrium.