Preparation of Heteropoly Acid Entraped in Nano Silica Matrix

Synthesis of heteropolyacid (H3PW12O40)/SiO2 nanoparticles and their catalytic properties

“…The H 3 PW 12 O 40 immobilized in silica nanoparticles was successfully obtained as shown in our previous work [9]. The sizes of heteropolyacid (H 3 PW 12 O 40 ) immobilized in silica nanoparticles (HPA/SiO 2 ) were controlled in the range from 100 to 500 nm by changing the water-to-surfactant molar ratio ([H 2 O]/[AOT], R) and reaction time (H).…”

“…Since the heteropolyacid (H 3 PW 12 O 40 ) does not react with TEOS or with water in the microemulsion, the heteropolyacid can remain in the silica nanoparticle without large change of the structures. Also, the elution test of heteropolyacid from the SiO 2 nanoparticles was performed in our previous work [9]. Elution of heteropolyacid (H 3 PW 12 O 40 ) was not observed in aqueous solution for 24 h in silica matrix.…”

“…Dispersed HPA/SiO 2 nanoparticles in cyclohexane were centrifuged at 15,000 rpm and the particles were then repeatedly rinsed with acetone. The particle size was controlled by change of the amounts of water [9].…”

“…These properties make some difficulties in catalyst recovery and catalyst life. Since environmentally benign solid acid catalysts have recently been demanded by society place of problematic sulfuric acid and aluminum chloride, it is a very significant and useful target to immobilize such catalytically highly efficient heteropolyacids into an insoluble, easily separable and high surface area solid [1,[7][8][9][10][11]. Izumi et al have reported H 3 PW 12 O 40 (HPA) immobilized inside a silica matrix and have obtained high catalytic activity [7,8].…”

“…For hydrolysis of metal alkoxides in acidic condition, however, microemulsion based sol-gel methods have yielded uncontrolled aggregation and flocculation. Although the heteropolyacid provided the condition of low pH, we successfully synthesized the silica nanoparticles containing the heteropolyacid by the fine control of microemulsion and sol-gel reaction [9].…”