method for synthesising microparticles

Abstract

A method for synthesising mesoporous silica microparticles comprising the steps of: —preparing a sol from an ammonium catalysed hydrolysis and condensation reaction of a pre-sol solution comprising a silica precursor and a structure directing agent dissolved in a mixed solvent system comprising an alcohol and water to produce mesoporous particles of silica with an average diameter of up to about 50 μm; hydrothermally treating the particles to increase the pore size; treating the particles to remove residual structure directing agent; and further increasing the pore size using controlled dissolution.

1 - 82 . (canceled) 
     
     
         83 . A method for synthesizing mesoporous silica microparticles comprising:
 preparing a pre-sol solution comprising a silica precursor and a structure directing agent dissolved in a mixed solvent system;   catalyzing a hydrolysis and condensation reaction of the pre-solution to produce mesoporous silica microparticles having an average pore diameter;   using the structure directing agent as a porogen to increase the size of pores in the microparticles; and   treating the resulting mesoporous microparticles to enlarge the average pore diameter.   
     
     
         84 . A method according to  claim 83  wherein treating the resulting mesoporous microparticles comprises:
 hydrothermally treating the microparticles to increase the pore size;   treating the microparticles to remove residual structure directing agent; and further increasing the pore size using controlled dissolution.   
     
     
         85 . A method according to  claim 83 , wherein further increasing the pore diameters comprises increasing the average pore diameter to at least 6.8 nm. 
     
     
         86 . A method according to  claim 83 , wherein the microparticles have diameters that vary no more than about 5% from the average diameter. 
     
     
         87 . A method according to  claim 83 , wherein the mixed solvent system comprises an alcohol and water. 
     
     
         88 . A method according to  claim 87 , wherein the alcohol of the mixed solvent system is one or more selected from the group consisting of: methanol, ethanol, propanol, 1-propanol, 2-propanol, butanol, 1-butanol, isopropyl alcohol, sec-butyl alcohol and isobutyl alcohol. 
     
     
         89 . A method according to  claim 84 , wherein the porous particles are hydrothermally treated at a temperature between about 70° C. and about 150° C. 
     
     
         90 . A method according to  claim 89 , wherein the porous particles are hydrothermally treated at a temperature of about 110° C. 
     
     
         91 . A method according to  claim 84 , wherein the step of controlled dissolution is repeated at least once to further increase the pore size. 
     
     
         92 . A method according to  claim 84 , wherein hydrothermally treating the microparticles comprises hydrothermally treating in an organic compound-water emulsion. 
     
     
         93 . A method according to  claim 92 , wherein the organic compound to water ratio is between about 1 v/v % and about 10 v/v %. 
     
     
         94 . A method according to  claim 92 , wherein the organic compound is an amine. 
     
     
         95 . A method according to  claim 94 , wherein the amine is a tertiary amine. 
     
     
         96 . A method according to  claim 94 , wherein the amine has the structure:
   (CH 3 ) 3-z N(C x H y ) z      wherein:   x is an integer between 1 and 20; and   y is an integer between 3 and 41.   Z=3, 2, 1, 0   
     
     
         97 . A method according to  claim 94 , wherein the amine is one or more selected from the group consisting of: N,N-dimethyldecylamine, trioctylamine, trimethylamine, tridodecylamine and triethylamine. 
     
     
         98 . A method according to  claim 94 , wherein the amine is N,N-Dimethyldecylamine. 
     
     
         99 . A method according to  claim 92 , wherein the organic compound is an alcohol. 
     
     
         100 . A method according to  claim 99 , wherein the alcohol is selected from one or more of the group comprising: hexanol, octanol, decanol and dodecanol. 
     
     
         101 . A method according to  claim 83 , wherein the mesoporous silica microparticles have an average diameter of up to about 50 μm. 
     
     
         102 . A method according to  claim 83 , wherein the mesoporous particles have an average diameter of at least about 0.1 μm. 
     
     
         103 . A method according to  claim 83 , wherein the mesoporous particles have an average diameter of about 0.1 μm to about 3 μm. 
     
     
         104 . A method according to  claim 83 , wherein the structure directing agent is a surfactant. 
     
     
         105 . A method according to  claim 104 , wherein the surfactant is a cationic surfactant. 
     
     
         106 . A method according to  claim 104 , wherein the surfactant has the structure:
   (CH 3 ) 4-n N + (C x H y ) n      wherein:   n is 1, 2, 3 or 4;   x is an integer between 12 and 20; and   y is an integer between 23 and 41.   
     
     
         107 . A method according to  claim 106 , wherein the surfactant is cetyltrimethylammonium bromide (CTAB). 
     
     
         108 . A method according to  claim 84 , wherein the controlled dissolution step comprises an etching process. 
     
     
         109 . A method according to  claim 108 , wherein the etching process utilizes a base catalyst. 
     
     
         110 . A method according to  claim 109 , wherein the base catalyst comprises a basic organic compound or an inorganic base. 
     
     
         111 . A method according to  claim 109 , wherein the base catalyst comprises an inorganic base comprising a hydroxide. 
     
     
         112 . A method according to  claim 111 , wherein the base catalyst is one or more selected from the group consisting of: ammonium hydroxide (NH4OH), sodium hydroxide, potassium hydroxide (KOH), lithium hydroxide (LiOH) and calcium hydroxide. 
     
     
         113 . A method according to  claim 111 , wherein the base catalyst is present in a concentration of between about 0.01 M and about 1 M. 
     
     
         114 . A method according to  claim 111 , wherein the base catalyst is present in a concentration of about 0.05 M. 
     
     
         115 . A method according to  claim 108 , wherein the particles are etched for up to about 12 hours. 
     
     
         116 . A method according to  claim 108 , wherein the particles are etched for about 1 day to about 5 days. 
     
     
         117 . A method according to  claim 108 , wherein the particles are etched for about 3 days. 
     
     
         118 . A method according to  claim 108 , wherein the particles are etched at a temperature of about 50° C. 
     
     
         119 . A method according to  claim 108 , wherein the etching process comprises a silica chelating or complexing agent. 
     
     
         120 . A method according to  claim 119 , wherein the silica chelating or complexing agent is present in a concentration of about 0.5M. 
     
     
         121 . A method according to  claim 119 , wherein the silica chelating or complexing agent is catechol. 
     
     
         122 . A method according to  claim 84 , wherein the particles are treated with an agent to remove residual structure directing agent. 
     
     
         123 . A method according to  claim 84 , wherein the particles are treated with heat to remove residual structure directing agent. 
     
     
         124 . A method according to  claim 123 , wherein the particles are heated to a temperature of about 400° C. to about 800° C. to remove residual structure directing agent. 
     
     
         125 . A method according to  claim 84 , wherein the particles are treated with microwave irradiation to remove residual structure directing agent. 
     
     
         126 . A method according to  claim 84 , wherein the particles are treated in air to remove residual structure directing agent. 
     
     
         127 . A method according to  claim 84 , wherein the particles are treated in an air-ozone mixture to remove residual structure directing agent. 
     
     
         128 . A method according to  claim 84 , wherein the particles are treated for about 1 hour to about 24 hours to remove residual structure directing agent. 
     
     
         129 . A method according to  claim 128 , wherein the particles are treated for at least 8 hours to remove residual structure directing agent. 
     
     
         130 . A method according to  claim 84 , wherein the particles are treated in the presence of an alcohol to remove residual structure directing agent. 
     
     
         131 . A method according to  claim 130 , wherein the alcohol is one or more selected from the group consisting of: ethanol, methanol, 1-propanol and 2-propanol. 
     
     
         132 . A method according to  claim 83 , wherein the silica precursor is one or more selected from the group consisting of: tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), tetrapropoxysilane (TPOS), tetrabutoxysilane (TBOS), tetra-acetoxysilane and tetrachlorosilane or an organic derivative thereof. 
     
     
         133 . A method according to  claim 132 , wherein the organic derivative has the formula:
   R n SiX (4-n)      wherein:   R is an organic radical;   X is a hydrolysable group selected from one or more of the group comprising: halide, amido, amino, acetoxy, alkoxy, teramethysilane and tetraethysilane; and   n is an integer from 1 to 4.   
     
     
         134 . A method according to  claim 83 , wherein the silica precursor is a hybrid silica precursor. 
     
     
         135 . A method according to  claim 134 , wherein the hybrid silica precursor is one or more selected from the group consisting of: dimethyldimethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, isobutyltriethoxysilane, isobutyltrimethoxysilane, phenyltrimethoxysilane, n-octyltriethoxysilane, and iso-octyltrimethoxysilane. 
     
     
         136 . A method according to  claim 135 , wherein the hybrid silica precursor is a bridged hybrid silica precursor having the general formula:
   R n X (3-n) Si—R′—Si—R n X (3-n)      wherein:   R is an organic radical;   X is a hydrolysable group such as halide, amido, amino, acetoxy, alkoxy, trimethysilane, or tetraethysilane;   R′ is a bridging group such as methyl, ethyl, propyl or butyl; and   n is 1 or 2.   
     
     
         137 . A method according to  claim 83 , wherein the ammonia catalyst is ammonium hydroxide. 
     
     
         138 . A method according to  claim 83 , wherein the pre sol solution contains from about 0.001 moles to about 0.08 moles of silica precursor. 
     
     
         139 . A method according to  claim 83 , wherein the pre sol solution contains from about 0.001 moles to about 0.006 moles of structure directing agent. 
     
     
         140 . A method according to  claim 83 , wherein the pre sol solution contains from about 8 moles to about 14 moles of alcohol. 
     
     
         141 . A method according to  claim 83 , wherein the pre sol solution contains from about 2 moles to about 10 moles of water. 
     
     
         142 . A method according to  claim 83 , wherein the pre sol solution contains from about 0.05 moles to about 1.5 moles of ammonia catalyst. 
     
     
         143 . A method according to  claim 83 , wherein the mole ratio of silica precursor:structure directing agent:alcohol:water:ammonia catalyst is about 0.0359:0.0032:12.36:6.153:0.505. 
     
     
         144 . A method according to  claim 83 , wherein the mole ratio of silica precursor:structure directing agent:alcohol:water:ammonia catalyst is 0.0359:0.0032:12.36:0.0159:6.153. 
     
     
         145 . A method according to  claim 83 , wherein the pre-sol solution is heated to a temperature of about −5° C. to about 80° C. 
     
     
         146 . A method according to  claim 145 , wherein the pre-sol solution is heated to a temperature of about −5° C. to about 80° C. for up to 2 hours. 
     
     
         147 . A method according to  claim 83 , wherein the pre-sol solution is agitated. 
     
     
         148 . A method according to  claim 83 , further comprising the step of adding a dopant compound to the pre-sol solution. 
     
     
         149 . A method according to  claim 148 , wherein the dopant compound comprises aluminium or boron. 
     
     
         150 . A method according to  claim 148 , wherein the dopant compound is one or more selected from the group consisting of: aluminium nitrate, aluminium isopropoxide and triethyl borane. 
     
     
         151 . Mesoporous silica microparticles produced by the method according to  claim 83 . 
     
     
         152 . A chromatography stationary phase comprising mesoporous silica microparticles produced by the method according to  claim 83 . 
     
     
         153 . Discrete mesoporous silica microparticles with an average particle diameter of about 0.1 μm to about 50 μm and an average pore diameter of at least 7.1 nm. 
     
     
         154 . Discrete mesoporous silica microparticles according to  claim 153  with an average particle diameter of about 0.1 μm to about 3 μm. 
     
     
         155 . Discrete mesoporous silica microparticles according to  claim 153  with an average particle diameter of about 3 μm to about 50 μm. 
     
     
         156 . Discrete mesoporous silica microparticles according to  claim 153  with an average pore diameter of about 7.1 nm to about 20.1 nm. 
     
     
         157 . Discrete mesoporous silica microparticles according to  claim 153  with an average pore volume of about 0.3 cm 3 g −1  to about 1 cm 3 g −1 . 
     
     
         158 . Discrete mesoporous silica microparticles according to  claim 153  with a surface area of about 100 m 2 g −1  to about 1000 m 2 g −1 . 
     
     
         159 . Discrete mesoporous silica microparticles according to  claim 153 , wherein the pores of the particles are ordered in a random direction. 
     
     
         160 . Discrete mesoporous silica microparticles according to  claim 153 , wherein the particles are in the form of spheres.