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SYNTHESIZING ALCOHOLS AND KETONES BY PHOTOINDUCED CATALYTIC PARTIAL-OXIDATION OF HYDROCARBONS IN TI02 FILM REACTORS PREPARED BY THREE DIFFERENT METHODS
Citation:
SahleDemessie**, E, M A. Gonzalez**, Z. M. Wang, AND P. Biswas. SYNTHESIZING ALCOHOLS AND KETONES BY PHOTOINDUCED CATALYTIC PARTIAL-OXIDATION OF HYDROCARBONS IN TI02 FILM REACTORS PREPARED BY THREE DIFFERENT METHODS. INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH 38(9):3276-3284, (1999).
Description:
The partial oxidation of cyclohexane to cyclohexanol and cyclohexanone on UV irradiated titanium dioxide films in the presence of molecular oxygen at ambient temperatures and pressures was studied. Three different coating methodologies (dip coating using titanium isopropoxide and commercially available titanium dioxide particles, sol-gel process and flame aerosol process) were used to deposit the titanium dioxide films, and their effectiveness in partial oxidation of cyclohexane was compared. Conversions of the cyclohexane in the gas phase reactor averaged between 1.1 to 8.7% per pass (8 second contact time) for the different film reactors. The yield (formation of ketone and alcohol) exceeded 96% for all the film reactors.
No detectable amount of carbon dioxide was generated. The selectivity for ketone formation ranged from 59 to 91%. The films produced by the flame aerosol method resulted in the highest yield per mass of catalyst used, and showed no coking and deactivation for a total run time of approximately 10 hours (two cycles). The films were characterized by XRD, SEM and TEM to establish the phase compositions, morphologies and primary particle sizes respectively. The flame aerosol coating resulted in the formation of high surface area aggregates consisting of nanometer sized primary particles with high density (minimal internal porosity), whereas dip coating resulted in formation of bulk crystallites that were more susceptible to coking and deactivation. The flame aerosol deposited titania particles had more surface sites per unit mass for photoxidation and minimal intraparticle diffusion limitations.