Method for producing a particle containing porous silica, porous silica, and a particle containing porous silica
Provided is a process for producing satisfactory particles held in porous silica. The process comprises (a) the step of preparing porous silica, (b) the step of bringing the porous silica into contact with a liquid which contains either a metal or a compound that has the metal as a component element and infiltrating the liquid into the pores of the porous silica, and (c) the step of subjecting, after the step (b), the impregnated porous silica to a heat treatment to thereby form fine particles comprising the metal or the metal compound in the pores of the porous silica. When porous silica is synthesized by hydrolyzing an alkoxysilane in a solvent-free system, it is possible to synthesize porous silica having a fine pore diameter. Use of this porous silica as a template facilitates formation of particles (e.g., W, Cu, Cr, Mn, Fe, Co, or Ni or an oxide of any of these metals) that show peculiar properties not observed in the bulk material.
1. A method for producing a particle containing porous silica comprising the following steps:
(a) producing porous silica by hydrolysis of alkoxy silane comprising the following steps:
(a1) mixing a surfactant and an alkoxy silane to form a mixed solution;
(a2) hydrolyzing the alkoxy silane by adding water to the mixed solution; and
(a3) removing the surfactant by heat treatment after the (a2) process;
(b) synthesizing the particle in the pores of porous silica produced in the step (a), and,
(c) removing the porous silica and obtaining a metallic oxide after the step (b),
wherein the step (b) is contacting the porous silica with solution or gas containing a compound comprising the metal of the metallic oxide as a component element to introduce pores of the porous silica with the solution or gas, and forming the particle containing the metallic oxide in the pores of the porous silica by heat treatment,
wherein the surfactant is a cationic surfactant of which carbon atoms of a hydrophobic group is 2 to 7,
wherein in the step (a2), silica is formed by the hydrolysis with micelle of the surfactant used as a template under a condition of a stoichiometric ratio of alkoxy silane:water=1:n, the amount of water is an amount in which n is 2 to 4; and, pH value of the water is 0 to 2, and
an average pore diameter of the porous silica is 0.5 nm or more to 1.5 nm or less.
2. The method according to claim 1 , wherein producing porous silica by hydrolysis of alkoxy silane further comprises a step of adding an organic silane compound.
3. The method according to claim 1 , wherein the heat treatment in the step (a3) is heat treatment at 600° C. for at least 3 hours.