A Non‐Aqueous Synthesis of TiO₂/SiO₂ Composites in Supercritical CO₂ for the Photodegradation of Pollutants

Abstract

Titania/silica composites with different Ti/Si ratios are synthesized via a nonconventional synthesis route. The synthesis involves non-aqueous reaction of metal alkoxides and formic acid at 75 °C in supercritical carbon dioxide. The as-prepared composite materials contain nanometer-sized anatase crystallites and amorphous silica. Large specific surface areas are obtained. The composites are evaluated in the photocatalytic degradation of phenol in aqueous medium, and in the elimination of acetaldehyde from air. The highest photocatalytic activity in both processes is achieved with a composite containing 40 wt % TiO₂.

Cost-effectiveness analysis to assess commercial TiO2 photocatalysts for acetaldehyde degradation in air

“…The catalyst-coating procedure, photocatalytic test protocol and procedure are discussed in detail elsewhere (Jammaer et al, 2011;Verbruggen et al, 2011Verbruggen et al, , 2012Tytgat et al, 2012). In summary, the catalysts were immobilised on 108 g of 2 mm glass beads (Assistent, Belgium, no.…”

Nanostructured Oxides Synthesised via scCO2-Assisted Sol-Gel Methods and Their Application in Catalysis

“…The whole sol-gel process in scCO 2 could be monitored by FTIR spectroscopy with an in-situ probe and by online gas chromatography-mass spectrometry (GC-MS) analysis [36]. The use of scCO2 as the solvent for the synthesis of nanostructured oxides was also applied using a high-throughput unit for performing reactions in scCO2 ( Figure 4) [42]. The reported set-up consisted of four modules: a visualisation batch reactor, a block with 10 parallel batch reactors, a block with 24 parallel batch reactors and a fixed-bed reactor.…”

“…The reactor was pressurised at 85 bar with CO 2 and subsequently heated to 75 • C. The powders obtained after depressurisation were calcined at 350 • C and then were employed as photocatalysts for the degradation of pollutants (see Section 3.1). The use of scCO2 as the solvent for the synthesis of nanostructured oxides was also applied using a high-throughput unit for performing reactions in scCO2 ( Figure 4) [42]. The reported set-up consisted of four modules: a visualisation batch reactor, a block with 10 parallel batch reactors, a block with 24 parallel batch reactors and a fixed-bed reactor.…”

“…The stability against hydrolysis of the CdS-ZnS quantum dots was not addressed. TiO2/SiO2 composites with different Ti/Si ratios were synthesised by reacting Si(OMe)4 and Ti(OPr i )4 in the presence of formic acid and scCO2 at 75 °C, with or without a surfactant (Pluronic 17R4) [42]. This non-aqueous synthesis method led to the formation of high surface area composites, reaching the highest value (595 m 2 /g) for the composite containing 40 wt % TiO2.…”

“…The obtained material was applied as photocatalyst for the photodegradation of Rhodamine B under UV irradiation and showed higher activity compared to commercial ZnO. The ZnO aerogel was reused three times without activity loss or structural change TiO 2 /SiO 2 composites with different Ti/Si ratios were synthesised by reacting Si(OMe) 4 and Ti(OPr i ) 4 in the presence of formic acid and scCO 2 at 75 • C, with or without a surfactant (Pluronic 17R4) [42]. This non-aqueous synthesis method led to the formation of high surface area composites, reaching the highest value (595 m 2 /g) for the composite containing 40 wt % TiO 2 .…”