Mechanism and kinetics of 1-dodecanol etherification over tungstated zirconia

Effect of Alcohol Structure on the Kinetics of Etherification and Dehydration over Tungstated Zirconia

“…Figure 4a shows that the apparent activation barrierf or etherification is fairly independent of the reactant. [19] This is consistentw ith the findings in Figure 4, as the increased sub- Also found in our previous study,t he dehydration of 1-hexanol produced both 1-hexene and 2-hexene, as verified by NMR spectroscopy ; however, no methyl shift was observed, as might be expected for the dehydration of as ubstrate such as 3,3-di-methyl-2-butanol. The dehydration activation barriers for 1-hexanol, 4-methyl-1pentanol, and 3-methyl-1-pentanola re 157 AE 13, 158 AE 10, and 155 AE 1kJmol À1 ,r espectively,i ndicating that the barriersa re within error for alcohols with branching at least three carbons away from the -OH group.…”

“…[17] The competing reaction for alcohold ehydration over an acid catalyst is unimolecular dehydration to form alkenes, which is thermodynamically favored at temperatures above approximately 350 K. Owing to their high volatility,a nd the propensityt of orm gums, alkenes are not desired in fuel and lubricant blends. [19] This study suggested that the high selectivity to ether is due to ac ooperative effect between Brønsted-and Lewis-acid sites on the surface of the catalyst, which promotes the bi-moleculare therification reaction. [19] This study suggested that the high selectivity to ether is due to ac ooperative effect between Brønsted-and Lewis-acid sites on the surface of the catalyst, which promotes the bi-moleculare therification reaction.…”

“…But from Figure4b, it is clear that as the substitution of the alcohol increases,t he barrier for unimolecular dehydration decreases. [19,37] In addition, sterice ffects that limit a-carbon oxygen bond formation between two alcohols could explain the preference towardsu nimolecular dehydration for 28 and 38 alcohols. But for 2-methyl-1-pentanol, 2-hexanol, and 2-methyl-2-pentanol, the barriers are 124 AE 2, 114 AE 5, and 100 AE 12 kJ mol À1 ,r espectively,i ndicating that the dehydration barrier decreases with increasing substitution of the alcohol.…”

“…[19,30,39,40] Powder X-ray diffraction (XRD) patterns for WO x /ZrO 2 were taken with aB ruker D8 GADDS diffractometer equipped with aC uK a source (40 kV,4 0mA). [19,30,39,40] Powder X-ray diffraction (XRD) patterns for WO x /ZrO 2 were taken with aB ruker D8 GADDS diffractometer equipped with aC uK a source (40 kV,4 0mA).…”

“…[19] The Arrhenius relation was given by: Apparent activation energies were calculated from an Arrhenius plot of the natural log of the initial rates versus the inverse temperature.…”