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A step forwards in ethanol selective photo-oxidation
Ciambelli, P.,Sannino, D.,Palma, V.,Vaiano, V.,Mazzei, R.S. Korean Society of Photoscience 2009 Photochemical & photobiological sciences Vol.8 No.5
This work focuses on the optimization of a photocatalyst formulation for the selective oxidation of ethanol to acetaldehyde. $VO_x/TiO_2$ catalysts at different vanadium loading were studied in a gas-solid photocatalytic fluidized bed reactor at high illumination efficiency, in which the bed is constituted by photocatalyst diluted with $\alpha-Al_2O_3$ or silica gel. Photocatalytic tests showed the selective formation of acetaldehyde, with ethylene and carbon dioxide as by-products. Selectivity is influenced by the vanadium loading. For ethanol inlet concentration of 0.2 vol%, maximum conversion and acetaldehyde selectivity of 73% and 97%, respectively, were obtained at $100^{\circ}C$ on catalyst at nominal 5 wt% $V_2O_5$ content (53% of surface monolayer) mixed with $\alpha-Al_2O_3$. Selective sites were related to surface polymeric vanadates possessing Ti-O-V and V-O-V functionalities while the photoactivity appeared correlated with the catalyst equivalent band gap energy. Increasing the ethanol inlet concentration to 1 vol% and diluting the catalyst with silica gel, total ethanol conversion with about 97% selectivity to acetaldehyde was achieved with a photoreactivity of $0.34\;mol\;{m_{irradiated}}^{-3}\;s^{-1}$. This is three times higher than reported for other photoreactors.
Mohammad Hajaghazadeh,Vincenzo Vaiano,Diana Sannino,Hossein Kakooei,Rahmat Sotudeh-Gharebagh 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.4
The effect of operating parameters on gas phase photocatalytic oxidation of methyl ethyl ketone (MEK) hasbeen investigated over P25 and PC500 photocatalysts. The parameters were gas flow rate, relative humidity (RH), reactiontemperature, and ultraviolet intensity. The photoreactor was composed of two LEDs matrices and a fluidized bedreactor (LED-FBR). No mass transfer limitation phenomena occurred at flow rates in the range 30-70 NL/h. The oxidationof MEK over the two photocatalysts did not highly depend on the presence or absence of humidity in the airstream. Temperature was determined as an important parameter in conversion of MEK over 60 to 120 oC, influencingalso the selectivity to carbon dioxide and carbon monoxide. The simultaneous influence of RH and temperature wasobserved in the reaction at different temperatures and RHs, evidencing the decrease in the selectivity towards CO withincrease of RH. With the increase of ultraviolet intensity, the rate of MEK oxidation increased over both catalysts, withthe better activity of PC500 than P25 particularly at higher light intensities. The main effect of temperature was both topromote the MEK conversion and to limit the competitive water adsorption in the PCO reaction over the tested titanias.