Method of producing silica-based particles

A method of producing hollow spherical silica-based particles, comprising:

• (a) a step of preparing a first dispersion liquid of first composite oxide particles having an average diameter (Dp1) of 3 to 300 nm by simultaneously adding a solution (M) containing element M and a solution (S) into an alkali aqueous solution so that a molar ratio (MOx/SiO2) of the first dispersion liquid is 0.01 to 2,
• wherein the solution (M) is an aqueous solution of an alkali soluble inorganic compound,
• the element M is at least one of Al, B, Ti, Zr, Sn, Ce, P, Sb, Mo, Zn, and W,
• the solution (S) is at least one of an aqueous silicate solution and an acidic silicic acid solution,
• the MOx denotes a molar number of the element M contained in the solution (M) in terms of an oxide, and
• the SiO2 denotes a molar number of an element Si contained in the solution (S) in terms of an oxide (SiO2),
• (b-1) a step of preparing a second dispersion liquid by adding an electrolytic salt into the first dispersion liquid so that a molar ratio (ME/MS) of the second dispersion liquid is 0.1 to 10,
• (b-2) a step of preparing a third dispersion liquid of third composite oxide particles that are the first composite oxide particles forming shells around the first composite oxide particles by adding a solution (M) containing element M and a solution (S) into the second dispersion liquid so that a value of B/A (the A denotes the molar ratio (MOx/SiO2) of the first dispersion liquid, the B denotes the molar ratio (MOx/SiO2) of the third dispersion liquid) satisfies 0<(B/A)≤0.8,
• wherein the electrolytic salt is a water-soluble compound selected from the group consisting of sodium chloride, potassium chloride, sodium nitrate, potassium nitrate, ammonium sulfate, magnesium chloride, and magnesium nitrate,
• the ME denotes a number of mole of the electrolytic salt,
• the MS denotes a number of mole of the element Si contained in the first dispersion liquid in terms of the oxide (SiO2),
• the solution (M) of the step (b-2) is an aqueous solution of an alkali soluble inorganic compound,
• the element M is at least one of Al, B, Ti, Zr, Sn, Ce, P, Sb, Mo, Zn, and W,
• the solution (S) of the step (b-2) is at least one of an aqueous silicate solution and an acidic silicic acid solution,
• the MOx denotes a molar number of the element M contained in the solution (M) of the step (b-2) in terms of an oxide, and
• the SiO2 denotes a molar number of an element Si contained in the solution (S) of the step (b-2) in terms of an oxide (SiO2),
• (c-1) a step of adding an acid into the third dispersion liquid to dissolve elements constituting the third composite oxide particles other than silicon,
• (c-2) a step of removing dissolved elements from a fourth dispersion liquid obtained by the step (c-1), and
• (e) a step of aging a fifth dispersion liquid obtained by the step (c-2) at a room temperature to 300° C.,
• wherein the third composite oxide particles have an average diameter (Dp2) of up to 500 nm, and a relationship between the Dp1 and the Dp2 is 3≤Dp1<Dp2≤500 nm.