Photo oxidation of DBT using carbon nanotube titania composite as visible light active photo catalyst

Abstract

Sulfur removal from liquid fuels has increased in importance in recent years. Although hydrodesulfurization is the usual method for removing sulfur, the elimination of thiophene compounds using this process is difficult. Photocatalysis is an alternative method being developed for thiophene removal at ambient conditions. Among semiconductors, titania has shown good potential as a photo-catalyst; however, quick recombination of electron holes hinders its commercial use. One way to decrease the recombination rate is to combine carbon nanotubes with a semiconductor. In this work, multiwall carbon nanotube (MWCNT) / titania composites were prepared with different mass ratios of MWCNT to titania using tetraethyl orthotitanate (TEOT) and titanium tetra isopropoxide (TTIP) as precursors of titania. Dibenzothiophene (DBT) photocatalytic removal from n-hexane was measured in both the presence and absence of oxygen. The results indicated that the best removal occurred when the MWCNT to titania ratio was 1. When the ratio exceeded this number, DBT removal efficiency decreased due to light scattering. Also, the composites prepared by TEOT exhibited better efficiency in DBT removal. The research findings suggested that the obtained composite was a visible light active photocatalyst and exhibited better performance in the presence of oxygen. Kinetics of photocatalytic DBT removal was a first-order reaction with removal rate constant 0.7 h^–1 obtained at optimum conditions.

Keywords

advanced oxidation processes / carbon nanotube / photocatalysis / UV / kinetics / semiconductor / sol-gel process

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