Method for synthesising microparticles

a technology of microparticles and synthesis methods, applied in the direction of metal layered products, inorganic chemistry, layered products, etc., can solve the problems of difficult to form high yields of porous particles, short separation of simple mixtures, and limited use of small particles, so as to increase the pore size

Inactive Publication Date: 2010-10-28
UNIV COLLEGE CORK NAT UNIV OF IRELAND CORK
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Benefits of technology

[0004]With conventional HPLC systems, the use of small particles has been limited to short, fast separations of simple mixtures. To work with longer columns, pumps that can achieve higher pumping pressures than conventional pumping systems are required. The pressure drop (ΔP) necessary to flow a mobile phase at the optimum linear velocity (uopt) through the packed bed increases at a rate inversely proportional to the particle diameter cubed, assuming constant mobile-phase viscosity and column length. For instance, flow, at uopt requires 125 times greater liquid pressure at the head of a column packed with 1 μm particles than for a column of equal length packed with 5 μm particles. The benefits however are a 5-fold increase in theoretical plates (N) and a 5-fold decrease in analysis time.
[0071]Calcination is described as a thermal treatment under air. As an alternative, mixtures of air and ozone may be used as this ensures complete removal of organic materials.

Problems solved by technology

However, the chromatographic industry is on the verge of radical change.
With conventional HPLC systems, the use of small particles has been limited to short, fast separations of simple mixtures.
The task of acquiring porous silica particles in the 1-2 μm size range suitable for UHPLC has proven to be a challenge as it is difficult to form high yields of porous particles with mean diameters below 2 μm that have a narrow size distribution.
Additionally, as commercial HPLC systems are not generally capable of operating at pressures above 400 bar, there have been very few commercial sources for porous particles in the 1-2 μm size range.
The stability of these materials is also questionable at the high pressures that are involved in UHPLC and they are not seen as suitable long term replacement for porous silica particles.
Such a method may result in a non-uniform distribution of pores and pores of greatly varying size depending on the amount of and location of radicals in the pre-formed spherical particles.
However, the application of many of these methods to the m-SFB system results in loss of particle size control or particle aggregation.
Techniques used to achieve a larger pore size in direct synthesis (prior to addition of metal oxide precursor) is a major challenge as any change to the reactant stoichiometry can result in a different particle size and distribution.

Method used

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  • Method for synthesising microparticles
  • Method for synthesising microparticles
  • Method for synthesising microparticles

Examples

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example 1

[0128]Mesoporous silica particles are prepared in several stages, as represented schematically in FIG. 1 and described below:

[0129]Step 1: CTAB (about 0.001 to about 0.006 moles, typically about 0.0032 moles) is first dissolved in methanol (at a concentration of about 8 to about 14 moles, typically about 12.36 moles). Ammonia (about 0.05 to about 1.5 moles, typically 0.505 moles) and water (about 2 to about 10 moles, typically about 6.153 moles) are added to the mixture and stirred for 15 minutes before the one step addition of TEOS (about 0.001 to about 0.08 moles, typically about 0.00826 moles. The silica precursor is typically present at a concentration of between about 5 to about 25% v / v of the pre-sol). The sol is allowed to stir for between 24 and 96 hours. The pre-sol solution may be prepared at temperatures between −5 and 80° C. and agitation speed of between 0 and 1000 rpm. The pre-sol solution should be clear and free from any visible particles to produce high quality poro...

example 2

Preparation of Mesoporous Silica Spheres

[0138]Mesoporous silica spheres were prepared based on modified methods described by Shimura et al.12 and Unger et al.15 Tetraethoxysilane (TEOS) was used as the silica precursor, while cetyltrimethylammonium bromide (CTAB) acted as the surfactant template. Methanol (MeOH) was used as the co-solvent.

[0139]In a typical reaction, 1.25 g of CTAB was mixed in a 2 L beaker with 88 ml of H2O and 500 ml of methanol and was left stirring (200 rpm) for 10 mins. 32 ml of NH4OH was then added to the solution and the system was left stirring for a subsequent 10 mins. Finally 8 ml of TEOS was added to the solution in a one step addition and the stirring speed increased to 300 rpm. The reaction temperature was controlled at 16° C. The liquid suspension was filtered from the beaker after 24 hours and was subsequently washed with MeOH. It was air-dried at room temperature for 2 hours. A known mass of the as-synthesised material was then added to a pre-prepare...

example 3

Preparation of Mesoporous Silica Spheres

[0140]Mesoporous silica spheres were prepared based on modified methods described by Shimura et al.12 and Unger et al.15 Tetraethoxysilane (TEOS) was used as the silica precursor, while cetyltrimethylammonium bromide (CTAB) acted as the surfactant template. Methanol (MeOH) was used as the co-solvent.

[0141]In a typical reaction, 1.25 g of CTAB was mixed in a 2 L beaker with 88 ml of H2O and 500 ml of methanol and was left stirring (200 rpm) for 10 mins. 32 ml of NH4OH was then added to the solution and the system was left stirring for a subsequent 10 mins. Finally 8 ml of TEOS was added to the solution in a one step addition and the stirring speed increased to 300 rpm. The reaction temperature was controlled at 16° C. The liquid suspension was filtered from the beaker after 24 hours and was subsequently washed with MeOH. It was air-dried at room temperature for 2 hours. A known mass of the as-synthesised material was then added to a pre-prepare...

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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.

Description

[0001]The invention relates to a method for the synthesis of porous silica particles with micrometer diameters.INTRODUCTION[0002]High-performance liquid chromatography (HPLC) is currently the most commonly applied technique for separating and analysing multi-component mixtures. However, the chromatographic industry is on the verge of radical change. The development of pumping technology and more sensitive detection systems has opened up a new field of HPLC known as ultra high-performance liquid chromatography (UHPLC). The shorter run times achieved by UHPLC, compared to HPLC, are possible by faster elution of the sample through a silica stationery phase composed of particles with diameters below 2 μm, typically between 1.1-1.9 μm.[0003]In recent years, improvements in chromatographic efficiency and analysis time have been demonstrated by the use of small stationary-phase support particles (<2 μm) packed into relatively long (>20 cm) fused-silica capillary columns. This techniq...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C01B33/12
CPCC01B33/12Y10T428/2982C01B37/02
Inventor HOLMES, JUSTINMORRIS, MICHAELHANRAHAN, JOHNKEANE, DONALCOPLEY, MARK
Owner UNIV COLLEGE CORK NAT UNIV OF IRELAND CORK
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