Abstract
The special photocatalytic degradation intrinsic kinetics of gaseous cyclohexane were investigated in a designed fluidized bed photocatalytic reactor (FBPR). A series of photocatalytic kinetic reaction equations were developed to explore the relationship of degradation efficiency and operating variables based on photocatalytic mechanism and particle fluidization hydrodynamic characteristics. The corresponding results indicated that the initial concentration has influenced the photocatalytic degradation reaction conversion, and having a concentration inflexion point which theoretically divided the photocatalysis into a first-order apparent kinetic rate equation at low concentrations and a zero-order kinetic rate equation at high concentrations. Furthermore, these results were validated theoretically by the intrinsic kinetic models of photocatalytic degradation conversion developed according to variation of cyclohexane concentration and gas velocity. Based on the experimental results, the optimal operating gas velocity range was determined. The multi-factors synergy effect resulting from gas velocity on photocatalytic degradation efficiency was explored and proved by mass transfer, illumination transmission and adsorption models. Finally, the degradation pathways of the cyclohexane and deactivation mechanism of the photocatalyst were studied according to the intermediates degraded on TiO2 surface, and a feasible method presented for catalyst regeneration.
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Abbreviations
- A i :
-
Peak area of component i (%)
- C e :
-
Equilibrium concentration (ppmv)
- C 0 :
-
Initial concentration of component i (ppmv)
- C t :
-
Remaining concentration at t min (ppmv)
- K i :
-
Adsorption equilibrium constant of the component i (ppmv min−1)
- D eff :
-
Diffusion coefficient (m2 s−1)
- k i :
-
Reaction rate constants of component i (ppmv min−1)
- [h +]:
-
Concentration of hole (mol L−1)
- [H2O]:
-
Water concentration (ppmv)
- I :
-
Light intension (μmol m−2 s−1)
- [.OH]:
-
Concentration of hydroxyl radical (mol L−1)
- r :
-
Photocatalytic degradation reaction rate (ppmv min−1)
- R :
-
Bed diameter (mm)
- RH :
-
Related humidity (%)
- R out :
-
Outer diameter of reactor (mm)
- U g :
-
Gas velocity (mm s−1)
- U mf :
-
Minimum fluidization velocity (mm s−1)
- t :
-
Time (min)
- T :
-
Ratio of transimission (%)
- z :
-
Bed height (cm)
- θ i :
-
Surface coverage (%)
- ε :
-
Averaged bed voidage (%)
- ρ :
-
Density (kg m−3)
- ŋ :
-
Degradation efficiency of component i (%)
- λ :
-
Thickness of reactor inner-sleeve
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Acknowledgments
This investigation was supported by the Ph.D. Programs Foundation of Weifang University (Contract No. 2012BS07), Natural Science Foundation of Shandong Province (Contract No. ZR2011BM019), and Education Department Teacher Project of Shandong Province (Contract No. J11LB55).
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Geng, Q., Wang, Q., Zhang, Y. et al. Photocatalytic degradation intrinsic kinetics of gaseous cyclohexane in a fluidized bed photocatalytic reactor. Res Chem Intermed 39, 1711–1726 (2013). https://doi.org/10.1007/s11164-012-0904-3
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DOI: https://doi.org/10.1007/s11164-012-0904-3