Photoactivity of Titanium Dioxide Supported on MCM41, Zeolite X, and Zeolite Y

Abstract

Titanium dioxide supported on microporous zeolites of type X and Y and on mesoporous molecular sieves of the MCM41 type was studied for the photocatalytic degradation of acetophenone in an aqueous medium. The photoactivity of the supported catalyst is strongly influenced by the method of titania loading, but less affected by the temperature at which the sample was calcined. The highest photoactivity among the supported catalysts is observed for a support that has a lower Si/Al ratio in the framework and relatively large pore size. The measured apparent activation energies for photocatalyzed consumption of acetophenone for a commercial TiO2 (P-25) and 10 wt % TiO2-loaded samples of zeolite A, X, Y, and Al-MCM41 are 4.2−6.7, 16.9, 13.5, 32.2 and 3.6 kJ/mol, respectively. Selective doping by Fe, Mn, and V into the framework of MCM41 suppresses the photoactivity of the supported titanium dioxide. The physical state of the titanium dioxide on the supports is characterized by XRD, adsorption and pore size analysis, IR, and Raman spectroscopy. All methods emphasize the small particle or amorphous character of the TiO2. The normal phase transition to rutile does not occur at higher temperatures on zeolite supports. In some cases, very low loadings of TiO2 appear to achieve total absorption of the light entering the reaction vessel. For the Al-rich MCM41-supported catalysts, maximal photoactivity can be achieved at low TiO2 loading (<3%). It appears to absorb 100% of light entering the reaction vessel with a much lower TiO2 load than is the case with TiO2 itself. There is evidence that the crystallinity of the zeolite is an important factor in photocatalytic efficiency, but the mechanism of zeolite participation in reactions remains incompletely elucidated.

Research progress of novel adsorption processes in water purification: A review

“…It also shows low adsorption ability for the pollutants due to its nonporous property , especially for the non-polar organic compounds due to its polar surface (Lepore et al, 1996). Thus, in recent years, attempts have been made to immobilize fine TiO 2 on porous adsorbent materials like silica (Lepore et al, 1996;Xu et al, 1999), activated carbon Yoneyama and Torimoto, 2000), alumina (Anderson and Bard, 1997), clay and zeolites (Sampath et al, 1994;Xu et al, 1997;Bhattacharyya et al, 2004) to produce composite adsorbent/catalyst. The sol-gel route is well established as an excellent method to prepare the TiO 2 -based materials.…”

Size-selective photocatalytic reactions by titanium(iv) oxide coated with a hollow silica shell in aqueous solutions

“…[16][17][18][19][20][21][22] Although various examples have been reported, this approach often includes a problem of difficulty to fabricate a TiO 2 photocatalyst with sufficient activity comparable to that of commercially available TiO 2 . From the viewpoint of practical utility, therefore, the use of commercially available TiO 2 having sufficient photocatalytic performance is more advantageous than the use of such synthesized TiO 2 photocatalysts.…”

Changing the characteristics and properties of zeolite Y and nano-anatase in the formation of a nano-anatase/Y composite with improved photocatalytic and adsorption properties

“…The following methods are currently used for the synthesis of nanocomposites NTD/Y: -Ion exchange between the Na + and NH 4+ forms of zeolite Y in an aqueous solution of (NH 4 ) 2 (TiNO)(C 2 O 4 ) 2 followed by calcination at 400-550 °C (nanocrystalline NTD in NTD/Y) (Liu et al 1992;Zhang et al 1995;Alwash et al 2013;Easwaramoorthi and Natarajan 2009); -Wet impregnation of zeolite NaY (Alwash et al 2013;Kuwahara et al 2012;Wang et al 2008) or HY (Kamegawa et al 2013) with a TiO 2 sol followed by evaporation of the liquid, drying, and calcination at 350-600 °C (amorphous (Alwash et al 2013) or nanocrystalline (Wang et al 2008) NTD in NTD/Y); -Mechanical mixing of NTD, which was synthesized by the sol-gel method (Maraschi et al 2014), via the hydrolysis of titanium isopropoxide (Xu and Langford 1997) or a solution of titanium tetraisopropoxide in ethanol (Ito et al 2014), with HY zeolite (Maraschi et al 2014) or NaY zeolite (Xu and Langford 1997;Ito et al 2014); the separation of the precipitate, washing, drying, and annealing at 350-450 °C [nanocrystalline NTD in NTD/Y (Xu and Langford 1997;Ito et al 2014)]; -A sol-gel method using titanate n-butyl acetate followed by annealing at 400 °C (Easwaramoorthi and Natarajan 2009;Wang et al 2015), the degree of crystallinity of the composite decreases with an increase in TiO 2 loading (Easwaramoorthi and Natarajan 2009) In NTD/Y nanocomposites synthesized by the ion exchange reaction (Liu et al 1992;Zhang et al 1995;Alwash et al 2013), nanocrystalline NTD occupies zeolite cavities (group II), as it was demonstrated by X-ray photoelectron spectroscopy (XPS), IR spectroscopy, X-ray powder diffraction, scanning (SEM) and transmission electron microscopy (TEM). In NTD/Y synthesized by wet impregnation (Alwash et al 2013;Jansson et al 2015) or mechanical mixing techniques (Maraschi et al 2014), amorphous …”