Etherification of glycerol with C4 and C5 reactive olefins

Etherification of glycerol with C4 (i-butene) and C5 (i-amylenes: 2-Methyl-2-Butene (2M2B) and 2-Methyl-1-Butene (2M1B) mixture) i-olefins was investigated for the production of transportation fuel oxygenates. Results proved formation of mono-, di- and tri-ethers of glycerol, as a result of its etherification with i-amylene at 120-140 °C over Amberlyst-36. Glycerol fractional conversion values and di-ether selectivity values approaching to 1.0 and 0.7 respectively were highly promising. Glycerol etherification results obtained by using i-butene as the reactant, proved the importance of Brønsted acidity of the catalyst, as well as the pore diffusion resistance, on the catalytic performance. Silicotungstic acid (STA), with very high acidity, showed very good performance at T ≤ 80 °C. However, at higher temperatures it also facilitated the oligomerization of i-butene, which caused a negative effect on glycerol etherification. Both Amberlyst-36 and Dowex DR-2030 showed excellent performance in catalyzing glycerol with i-butene, at 90 °C. Results proved that etherification of the biodiesel by-product glycerol could be successfully achieved by using i-amylenes, as well as i-butene, to improve the economics of biodiesel production.