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 H-1 and C-13 NMR and infrared spectroscopy and mass spectrometry.