Tin(II) phosphotungstate heteropoly salt: An efficient solid catalyst to synthesize bioadditives ethers from glycerol

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.