期刊
CATALYSIS TODAY
卷 372, 期 -, 页码 238-245出版社
ELSEVIER
DOI: 10.1016/j.cattod.2020.10.005
关键词
Solketal; Sulfated zirconia; Batch reactor; Kinetic model
资金
- Consejo Nacional de Investigaciones Cientificas y Tecnicas [CONICET-PIP 0065]
- Universidad Nacional de La Plata [UNLPI248]
- CONICET
A series of acid catalysts were synthesized from a commercial zirconium oxide sulfated with a 0.5 M H2SO4 solution by wet impregnation. The sulfated zirconia calcined in air at 400 degrees C (Zr-S-400) showed the highest activity and stability for glycerol conversion, with a molar ratio S/Zr = 0.23. The estimated activation energy of the reaction based on a developed kinetic expression was 88.1 +/- 8.9 kJ/mol.
In this work, a series of acid catalysts were synthetized from a commercial zirconium oxide sulfated with a 0.5 M H2SO4 solution by wet impregnation. The characterization results show a correlation between the calcination temperature and the acid sites generated on the materials. Among the catalysts prepared, the sulfated zirconia calcined in air at 400 degrees C (Zr-S-400), with a molar ratio S/Zr = 0.23 was the most active one due to its larger acid density and greater acid strength caused by the generation of new Bronsted sites. The Zr-S-400 catalyst exhibited an initial reaction rate of 0.0497 mol.min(-1).g(-1), and achieved a glycerol conversion of 80 % in 1 h of reaction at 40 degrees C (glycerol:acetone molar ratio = 1:6). The Zr-S-400 material remained stable after four catalytic cycles, demonstrating the stability of the superficial sulfate species (S/Zr similar to 0.2). In addition, the thermodynamics and kinetics of the reaction were evaluated, as well as the influence of some operating conditions such as the molar ratio of reactants and the water content in the reaction mixture. The following standard molar reaction properties were obtained: Delta H degrees = -11.6 +/- 1.1 kJ.mol(-1) and Delta G degrees = 4.0 +/- 0.1 kJ.mol(-1). Taking into account that the adsorption of water on this catalyst did not affect the number of acid sites available, a simple pseudohomogeneous kinetic expression was developed and successfully adjusted to the experimental data in the range under study. Based on this model, the estimated activation energy of the reaction was 88.1 +/- 8.9 kJ.mol(-1).
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