The adsorption-enhancing TiO2-SBA-15 photocatalyst has been synthesized by an in situ etching displacement method, which possesses unique regular hexagonal pores and large specific surface area. The as-prepared TiO2-SBA-15 can effectively adsorb and increase the concentration of pollutants in the photocatalyst and collision likelihood with the photogenerated radicals, thus improving the efficiency of photocatalytic organic degradation. The structure and morphology have been characterized by N2adsorption isotherms, X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), and scanning electron microscopy (SEM). These characterizations confirm that TiF4alcohol solution prefers to react with the internal surface of SBA-15 because of the Siphon effect. Fourier transform infrared (FTIR) spectra demonstrate that a Ti-O-Si bond formed after the reaction of TiF4with SBA-15, which reveals a wonderful combination of TiO2and SiO2even at low temperatures. Through this function, the nanocomposite TiO2-SBA-15 could obviously improve the efficiency of photocatalytical removal of toluene in the gas phase.
This study investigates catalytic adsorptive desulfurization (CADS) of model diesel fuel using TiO 2 /SBA-15 under mild conditions. The TiO 2 /SBA-15 was prepared by a facile incipient wetness impregnation method and characterized by N 2 adsorption and X-ray diffraction. The CADS referred to ADS performance were evaluated in a batch reactor. High desulfurization uptake of 12.7 mg/g was achieved at low sulfur concentration of 15 ppmw-S by TiO 2 /SBA-15 under CADS, which was two-magnitude higher than that under ADS without the in-situ catalytic oxidation of dibenzothiophene. Kinetic results suggested that the CADS equilibrium over TiO 2 /SBA-15 was reached fast in 0.5 h. In the CADS–TiO 2 /SBA-15 system, the TiO 2 loading, cumene hydroperoxide/dibenzothiophene ratio and CADS temperature were optimized to be 10 wt%, 2, and 35 °C, respectively. Furthermore, desulfurization tests in 5 consecutive CADS-regeneration cycles suggested that the bi-functional TiO 2 /SBA-15 can be regenerated by acetonitrile washing followed with oxidative air treatment. The CADS–TiO 2 /SBA-15 mechanism went through the oxidation of DBT to oxidized DBTO 2 over TiO 2 /SBA-15 by cumene hydroperoxide, which was followed by the adsorption of the oxidized DBTO 2 over TiO 2 /SBA-15. The superior desulfurization uptake at low sulfur concentration range, fast adsorption kinetics, excellent regenerability, operation at mild conditions, and facile and low-cost adsorbent synthesis make the CADS–TiO 2 /SBA-15 system an effective and economic desulfurization approach for ultra-clean fuel production.
Bi-doped TiO2/SBA-15 (Bi–TiO2/SBA-15) was synthesized by a wet impregnation method. It was found that SBA-15 retained its ordered hexagonal mesostructure after incorporation of TiO2 and Bi. TiO2 nanoparticles and Bi species dispersed well and anchored both in the channel and the wall of SBA-15. The photocatalytic activity was evaluated on photodegradation of Rhodamine B (RhB) under visible light irradiation (λ ≥ 420 nm). Experimental results indicated that Bi–TiO2/SBA-15 exhibited higher photocatalytic activities than pure TiO2 and TiO2/SBA-15 owing to the synergetic effects of Bi species and TiO2. The degradation of RhB by these catalysts follows the pseudo-first-order kinetic model and Bi–TiO2/SBA-15 (2.0%) was found to be the best. The effect of Bi doping on the photocatalytic activity was investigated by the density functional theory (DFT) method. The calculated results indicated that Bi doping could improve the photocatalytic activity by extending the spectral response from UV to the visible region, making the Bi–TiO2/SBA-15 active under visible light irradiation.
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