Method for producing porous spherical silica gel particles

Abstract

A method for forming a porous spherical silica material is provided, which includes the steps of mixing an alkali silicate with a mineral acid at a pH and temperature sufficient to form a silica sol, mixing the silica sol with an oil and a surfactant to form a water-in-oil emulsion, adding an alkaline solution to the emulsion to form a gel, adding a demulsifier, heating to a temperature of about 60° C. to about 90° C., filtering, washing, optionally aging, and drying to obtain porous spherical silica gel particles.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 320,600, filed March 16, 2022, the contents of which are incorporated by reference in their entirety into this specification. [Background technology]

[0002]

[0002] Porous, spherical silica particles are used in a wide range of applications. For example, they can be used as fillers for films and resins, as carriers or supports for various catalysts, as fillers for cosmetics, as chromatographic fillers, as desiccants, and for other purposes. The requirements for the physical properties of the silica particles, such as particle size, particle shape, particle size distribution, pore size, pore volume, and surface area, can vary depending on the application.

[0003]

[0003] Various methods for producing porous spherical silica particles are known in the art. For example, in some methods, aqueous sodium silicate solution or alkyl silicate is emulsified in a solvent and then gelled. In other methods, aqueous sodium silicate solution or alkyl silicate is gelled and then emulsified in a solvent and granulated. In still other methods, silica sol or alkali silicate is spray-dried to form porous spherical particles. Also, some methods include wet-milling hydrogel followed by spray-drying. However, there is still a need for a simple and economical method for producing porous spherical silica particles in which the pore size, pore volume, and particle size can be reliably controlled. Summary of the Invention [Means for solving the problem]

[0004]

[0004] A method for forming a porous spherical silica material is provided, which includes the steps of mixing an alkali silicate with a mineral acid to form a silica sol, mixing the silica sol with an oil and a surfactant to form an emulsion, adding an alkaline solution to the emulsion to form a gel, adding a demulsifier, and filtering to obtain silica gel particles.

[0005] The silica material formed by the method includes a plurality of porous, spherical silica gel particles. Each particle includes a rigid network of amorphous silica. The particles have an average aspect ratio of about 1.2 or less, an average pore volume of greater than about 0.3 cc / g, and an average pore volume of at least about 200 m. 2 / g; and a median particle size of about 1 μm or greater.

[0006]

[0006] Other features and aspects of the disclosure are discussed in further detail below. [Brief description of the drawings]

[0007] [Figure 1] 1 is a process flow diagram of a production method according to the present disclosure. [Diagram 2]

[0008] FIG. 2 shows an SEM image of silica particles produced in Example 1. [Diagram 3]

[0009] FIG. 2 shows an SEM image of silica particles produced in Example 2. [Figure 4]

[0010] FIG. 1 shows an SEM image of silica particles produced in Example 3. [Diagram 5]

[0011] FIG. 1 shows an SEM image of silica particles produced in Example 4. [Figure 6]

[0012] FIG. 1 shows an SEM image of silica particles produced in Example 5. [Figure 7]

[0013] FIG. 1 shows an SEM image of silica particles produced in Example 6. [Figure 8]

[0014] FIG. 1 shows an SEM image of silica particles produced in Example 7. [Figure 9]

[0015] FIG. 1 shows an SEM image of silica particles produced in Example 8. [Figure 10]

[0016] FIG. 1 shows an SEM image of silica particles produced in Example 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008]

[0017] Before describing several exemplary embodiments, it is to be understood that the invention is not limited to the details of construction or process steps set forth in the following description as the invention is capable of other embodiments and of being practiced or carried out in various ways.

[0009]

[0018] The embodiments described herein by way of example may suitably be practiced in the absence of any element or elements, or limitation or limitations not specifically disclosed herein. Thus, for example, the terms "comprising," "including," "containing," and the like, should be read expansively and without limitation. Furthermore, the terms and expressions used herein are used as terms of description without limitation, and in using such terms and expressions, there is no intention to exclude any equivalents of the features shown and described, or portions thereof, but it is recognized that various modifications are possible within the scope of the technology described in the claims. In addition, the phrase "consisting essentially of" is understood to include the elements specifically described and additional elements that do not materially affect the basic and novel characteristics of the technology described in the claims. The phrase "consisting of" excludes any elements not specified.

[0010]

[0019] As used herein, "about" will be understood by those of ordinary skill in the art and will vary to some extent depending on the context in which it is used. If there are uses of terms which are not clear to persons of ordinary skill in the art, "about" will mean up to plus or minus 10% of the particular term, given the context in which it is used.

[0011]

[0020] In describing elements (particularly in the context of the claims which follow), use of the terms "a" and "an" and "the" and similar referents should be construed to include both the singular and the plural, unless otherwise indicated in the specification or clearly contradicted by context.

[0012]

[0021] As will be understood by those skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges disclosed herein include any and all possible subranges and combinations of subranges. Any recited range can be easily recognized as being fully described, with that same range being at least equally divisible into halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be easily subdivided into a lower third, a middle third, and an upper third, etc. As will also be understood by those skilled in the art, all terms such as "less than," "at least," "greater than," "less than," etc., refer to ranges that are inclusive of the recited numbers and can then be subdivided into subranges as discussed above. Finally, as will be understood by those skilled in the art, a range includes each individual member.

[0013]

[0022] In general, the present disclosure relates to a method for forming single gel porous silica particles by an emulsification process. The method generally involves preparing a silica sol by mixing an alkali silicate with an acid at a specific pH and temperature, and then mixing the sol with an oil and a surfactant to produce a water-in-oil emulsion. The term "water-in-oil emulsion" is used herein to indicate an emulsion in which oil is the continuous phase and water is the dispersed phase. The "water" used in the term "water-in-oil emulsion" should be understood to include aqueous silica sol. The pH can then be adjusted by adding a basic compound to the emulsion to control the gelation process and the final pore structure within the emulsion. It has been discovered that by manipulating certain aspects of the emulsification process, the particle size, particle size distribution, pore volume, pore size, and surface area can be reliably controlled. In addition, the method forms spherical single gel particles that exhibit various advantages over particles formed by conventional processes, such as those formed by spray-drying agglomeration processes.

[0014]

[0023] For example, when used as a catalyst support, catalysts containing single gel support particles tend to perform better in olefin polymerization processes than catalysts containing agglomerated support particles. As used herein, single gel particles refer to particles that are not formed from an agglomerate of smaller particles. Agglomerates refer to products that combine particles held together by a variety of physical-chemical forces. More specifically, agglomerates consist of multiple continuous component primary particles that are joined and connected at contact points. In contrast to agglomerates, single gel particles cannot be separated into smaller particles without fracturing the particles.

[0015]

[0024] The method is also suitable for forming gel particles for a variety of applications including, for example, catalyst supports, chromatographic media, plastics additives, personal care and cosmetics, as it can produce particles having desired particle size and pore characteristics.

[0016]

[0025] The method can be used to form particles having relatively high surface areas as determined by the BET method using nitrogen adsorption as described hereinbelow. For example, particles having an average surface area of ​​about 200 m 2 / g or more, in some embodiments, about 300 m 2 / g or more, in some embodiments, about 400 m 2 / g or more, in some embodiments, about 500m 2 / g or more, in some embodiments, about 600 m 2 / g or more, in some embodiments, about 700m 2 The average surface area of ​​the particles can be about 1000 m 2 / g or less, in some embodiments, about 900m 2 / g or less, in some embodiments, about 800 m 2 / g or less, in some embodiments, about 700 m 2 / g or less, in some embodiments, about 500m 2 / g or less.

[0017]

[0026] In addition, the methods can be used to form particles having relatively high pore volumes as measured by nitrogen pore volume as described herein below. For example, the average pore volume of the particles can be about 0.3 cc / g or more, in some embodiments about 0.5 cc / g or more, in some embodiments about 0.8 cc / g or more, and in some embodiments about 1.2 cc / g or more. The pore volume can be about 2.5 cc / g or less, in some embodiments about 2.0 cc / g or less, in some embodiments about 1.5 cc / g or less, and in some embodiments about 1 cc / g or less. In some embodiments, the pore volume ranges from 0.3 to 2.5 cc / g, in some embodiments about 0.5 to 2 cc / g, and in some embodiments about 0.8 to about 1.5 cc / g.

[0018]

[0027] The method can produce particles having an average pore size, as measured by nitrogen porosimetry, of about 30 Angstroms or more, in some embodiments about 50 Angstroms or more, in some embodiments about 70 Angstroms or more, in some embodiments about 100 Angstroms or more, and in some embodiments about 150 Angstroms or more. The average pore size can be about 300 Angstroms or less, in some embodiments about 250 Angstroms or less, and in some embodiments about 200 Angstroms or less.

[0019]

[0028] Surface areas are determined by BET nitrogen adsorption analysis after activation of the samples at 400 °C for 30 min in vacuum. Surface areas are calculated from multipoint values ​​of nitrogen volumetric uptake in the adsorption branch at low partial pressures [P / Po = ~0.05-0.15]. The adsorption branch of the isotherm is stopped at a partial pressure of P / Po = 0.995 and then the descending branch of the isotherm is measured. Nitrogen pore volume is calculated by applying Gurvich's law at P / Po = 0.995. Pore diameters are reported as calculated BJH desorption mean diameters.

[0020]

[0029] Traditionally, it has been difficult to produce spherical, single gel porous silica particles with both high pore volume and high surface area. However, in some embodiments, the methods described herein provide an average pore volume of about 2.3 cc / g or more and a surface area of ​​about 350 m 2 It is possible to produce silica particles having average surface areas greater than 100 / g. For example, when used in catalytic applications, such a combination allows for high catalyst loading of the support and high catalyst activity during polymerization.

[0021]

[0030] The method can produce porous silica particles having a median particle size (D50) of about 1 μm or more, in some embodiments about 3 μm or more, in some embodiments about 8 μm or more, in some embodiments about 15 μm or more, and in some embodiments about 20 μm or more, as measured by the laser diffraction method described hereinbelow. The average particle size can be about 50 μm or less, and in some embodiments about 40 μm or less.

[0022]

[0031] Regardless of their average size, the method can produce particles having a relatively narrow particle size distribution. The width of the particle size distribution is given by:

[0023]

number

[0024] [In the formula, D 10 , D 50 , and D. 90 represent the 10th, 50th, and 90th percentiles of the particle size (diameter) distribution, respectively, i.e., D of 100 microns 90 means that 90% by volume of the particles have a diameter less than or equal to 100 microns. In this regard, the distribution span of the particles can be about 2.0 or less, in some embodiments about 1.5 or less, in some embodiments about 1.45 or less, in some embodiments about 1.4 or less, in some embodiments about 1.3 or less, and in some embodiments, from about 0.9 to about 1.25.

[0025]

[0032] The present inventors have unexpectedly discovered that the emulsification process described herein can produce porous silica particles having the unique properties described above. In addition, it has been found that the particle size, particle size distribution, pore size, pore volume, and surface area of ​​the particles can be controlled by manipulating certain aspects of the emulsification process.

[0026]

[0033] In the water-in-oil emulsification process, a silica sol is prepared by mixing an alkali silicate with an acid. The sol is then mixed with oil and a surfactant to produce an emulsion. In the emulsion formed during this process, the oil phase is continuous and the sol forms stable spherical droplets dispersed in the oil phase. The pH can then be adjusted by adding a basic compound to the emulsion, which can help control the gelation process and the final pore structure within the emulsion.

[0027]

[0034] This process is described in more detail with reference to FIG. 1. First, in step 101, a silica sol is formed by combining a mineral acid and an alkali silicate. The alkali silicate can include sodium silicate, potassium silicate, lithium silicate, and the like. The alkali silicate is typically provided as an aqueous solution at a concentration of about 5 wt.% to about 50 wt.% (based on SiO2 in the alkali silicate), for example about 10 wt.% to about 35 wt.%. The mineral acid can be sulfuric acid, hydrochloric acid, nitric acid, and the like. In some embodiments, the alkali silicate is sodium silicate and the mineral acid is sulfuric acid. In other embodiments, the alkali silicate is sodium silicate and the mineral acid is hydrochloric acid. To form the sol, the alkali silicate can be added to a vessel containing the mineral acid. The flow rate is adjusted to obtain a desired throughput on an industrial scale. For example, on a laboratory scale, the alkali silicate can be added to the mineral acid at a flow rate of about 1 ml / min to about 250 ml / min, for example, about 5 ml / min to about 200 ml / min, preferably about 50 ml / min to about 200 ml / min. Alternatively, the alkali silicate and the mineral acid can be combined at one time by pouring one into the other. The concentration of the mineral acid is typically about 10 wt.% to about 50 wt.%, in some embodiments about 15 wt.% to about 40 wt.%, in some embodiments about 18 wt.% to about 35 wt.%. The weight ratio of the mineral acid to the alkali silicate preferably results in a pH of less than 7. The weight ratio of the mineral acid to the alkali silicate is generally about 1:10 to about 2:1, in some embodiments about 1:7 to about 1:1, in some embodiments about 1:5 to about 1:2.

[0028]

[0035] In some embodiments, the concentration and amount of aqueous alkali silicate and mineral acid are selected to reach a specified pH value.For example, in some embodiments, the pH of the resulting mixture is controlled to remain below about 4, such as below about 3, such as below about 1.5. The pH of the resulting mixture is usually about 1 or more.

[0029]

[0036] During the sol formation process, the temperature should be controlled to a relatively low temperature, for example, in some embodiments, the temperature is controlled to about 40° C. or less, in some embodiments, about 30° C. or less, and in some embodiments, about 20° C. or less.

[0030]

[0037] To form the sol, the mineral acid and the alkali silicate can be continuously mixed in a container using a mixer, such as an overhead mixer. The mixer can be operated at any suitable speed for a period of time sufficient to form the sol. For example, in some embodiments, the mixture can be mixed for a period of time from about 2 minutes to about 1 hour, such as from about 5 minutes to about 45 minutes, such as from about 10 minutes to about 40 minutes.

[0031]

[0038] After the sol is formed, it is pumped or otherwise combined with the oil and surfactant to form a water-in-oil emulsion in step 102. The oil and surfactant can be combined to form a surfactant / oil mixture, and this mixture is added to the sol. The amount of surfactant can be controlled to form stable spherical silica sol droplets. In some embodiments, the surfactant is present in the mixture in an amount ranging from about 3 wt. percent to about 25 wt. percent of the total surfactant / oil mixture. Preferably, the surfactant is present in the mixture in an amount ranging from about 5 wt. percent to about 15 wt. percent. Alternatively, the oil and surfactant are added separately to the sol in amounts sufficient to provide a surfactant / oil mixture having the wt. percentages described above.

[0032]

[0039] The oil is not particularly limited except that it should be non-reactive and immiscible with the aqueous alkali silicate and mineral acid. Representative oils include n-octane, gasoline, kerosene, isoparaffinic hydrocarbon oils, etc., alicyclic hydrocarbons such as cyclononane, cyclodecane, etc., aromatic hydrocarbons such as toluene, xylene, ethylbenzene, tetralin, etc., and mixtures of alkanes, such as mineral oil.

[0033]

[0040] A wide range of surfactants, such as glycerol monocaprylate, glycerol monolaurate, glycerol mono / dicoccoate, glycerol dilaurate, glycerol monostearate, glycerol monostearate distillate, glycerol distearate, glycerol monooleate, glycerol dioleate, glycerol trioleate, glycerol monoisostearate, glycerol monoricinoleate, glycerol monohydroxystearate, POE glycerol monostearate, acetylated glycerol monostearate glycerol phthalate, succinylated glycerol monostearate, diacetylated glycerol monostearate tartrate, modified glycerol phthalate resin, triglycerol monostearate, triglycerol monooleate, triglycerol monoisostearate, decaglycerol tetraoleate, decaglycerol deca stearate, pentaerythritol monolaurate, pentaerythritol monostearate, pentaerythritol distearate, pentaerythritol tetrastearate, pentaerythritol monooleate , pentaerythritol dioleate, pentaerythritol trioleate, pentaerythritol tetraricinoleate, sorbitan monolaurate, POE sorbitan monolaurate, sorbitan monopalmitate, POE sorbitan monopalmitate, sorbitan monostearate, POE sorbitan monostearate, sorbitan tristearate, POE sorbitan tristearate, sorbitan monooleate, POE sorbitan monooleate, sorbitan sesquioleate, sorbitan trioleate, POE sorbitan trioleate Oleate, POE sorbitol hexaoleate, POE sorbitol oleate laurate, POE sorbitol polyoleate, POE sorbitol, beeswax esters, sucrose monolaurate, sucrose cocoate, sucrose monomyristate, sucrose monopalmitate, sucrose dipalmitate, sucrose monostearate, sucrose distearate, sucrose monooleate, sucrose dioleate, lauryl lactate, cetyl lactate, sodium lauryl lactate, sodium stearoyl lactate,Sodium isostearoyl-2-lactylate, sodium stearoyl-2-lactylate, calcium stearoyl-2-lactylate, sodium capryl lactate, lauryl alcohol, and cetyl alcohol can be used.

[0034]

[0041] In one embodiment, the surfactant comprises at least one sorbitan ester. The sorbitan esters include sorbitan fatty acid esters, where the fatty acid moiety of the ester comprises a carboxylic acid of from about 10 to about 100 carbon atoms, in one embodiment from about 12 to about 24 carbon atoms. The sorbitans are a mixture of anhydrosorbitols, primarily 1,4-sorbitan and isosorbide (Formulas I and II):

[0035] [ka]

[0036]

[0042] Sorbitan (also called monoanhydrosorbitol or sorbitol anhydride) is a general term for anhydrides that can be derived from sorbitol by removing one molecule of water. The sorbitan fatty acid esters of this invention are mixtures of partial esters of sorbitol and its anhydrides with fatty acids. These sorbitan esters can be represented by the following structure, which can be any one of monoesters, diesters, triesters, tetraesters, or mixtures thereof (Formula III):

[0037] [ka]

[0038]

[0043] In formula (III), each Z independently represents a hydrogen atom or C(O)R-, and each R independently represents a hydrocarbyl group of from about 9 to about 99 carbon atoms, more preferably from about 11 to about 23 carbon atoms. Examples of sorbitan esters include sorbitan stearate and sorbitan oleate, such as sorbitan stearate (i.e., monostearate), sorbitan distearate, sorbitan tristearate, sorbitan monooleate, and sorbitan sesquioleate. Sorbitan esters also include polyoxyalkylene sorbitan esters, in which the alkylene group has from about 2 to about 30 carbon atoms. These polyoxyalkylene sorbitan esters have formula IV:

[0039] [ka]

[0040] wherein each R is independently an alkylene group of from about 2 to about 30 carbon atoms; R' is a hydrocarbyl group of from about 9 to about 99 carbon atoms, more preferably from about 11 to about 23 carbon atoms; and w, x, y, and z represent the number of repeating oxyalkylene units. For example, ethoxylation of sorbitan fatty acid esters results in a series of more hydrophilic surfactants, which is the result of the hydroxy groups of sorbitan reacting with ethylene oxide. One major class of these ethoxylated sorbitan esters is one that contains from about 2 to about 80 ethylene oxide units, in one embodiment from about 2 to about 30 ethylene oxide units, in one embodiment about 4, in one embodiment about 5, and in one embodiment about 20 ethylene oxide units. Typical examples are polyoxyethylene (hereinafter "POE") (20) sorbitan tristearate, POE (4) sorbitan monostearate, POE (20) sorbitan trioleate, POE (5) sorbitan monooleate, and POE (80) sorbitan monooleate. As used herein, the number in parentheses refers to the number of ethylene oxide units present in the composition.

[0041]

[0044] Useful surfactants of the type listed in the above table can be generally represented by the following classes of chemical compounds, some of which are commercially available and suitable provided they are used in accordance with the teachings herein to produce stable emulsions: (a) Sorbitol esters of the general formula:

[0042] [ka]

[0043] [wherein the groups X are the same or different and each represents OH or R 1 COO - and; R 1 is a linear or branched, saturated or unsaturated aliphatic hydrocarbon radical having 7 to 22 carbon atoms, optionally substituted by hydroxyl, provided that at least one of the radicals X is R 1 COO - is], (b) a fatty acid ester of the general formula:

[0044] [ka]

[0045] [In the formula, R 2 is a linear or branched, saturated or unsaturated aliphatic hydrocarbon group having 7 to 22 carbon atoms, optionally substituted by a hydroxyl group; R 3 is linear or branched C1-C 10 alkylene; n is an integer greater than or equal to 6; R 4 is H, linear or branched C1-C 10 Alkyl or

[0046] [ka]

[0047] and R5 is R 2 as defined above for and, (c) a polyalkoxylated alkylphenol of the general formula:

[0048] [ka]

[0049] [In the formula, R 6 is linear or branched C1-C 20 alkyl; m is an integer greater than or equal to 8; R 7 and R 8 are R in formula (II), 3 and R 4 as defined above for

[0050] Typically, the weight ratio of the sol to the oil and surfactant mixture can be from about 1:5 to about 5:1, such as from about 1:4 to about 4:1, such as from about 1:3 to about 2:1, such as from about 1:2 to about 2:1. In some embodiments, the oil is a mineral oil and the surfactant is a sorbitan ester, such as sorbitan monooleate, and the weight ratio ranges from 1:2 to 2:1.

[0051]

[0046] The temperature can be controlled during the emulsion formation process to obtain the desired silica sol droplet size. For example, the temperature can be maintained at greater than about 30°C, such as from about 40°C to about 80°C, such as from about 50°C to about 65°C, while forming the emulsion.

[0052] The mixing speed should be high enough to form a stable emulsion, i.e., an emulsion that does not separate when left at room temperature for a desired time, and to obtain the desired silica sol droplet size. Such mixing speed can be achieved using an overhead type mixer, such as a DISPERMAT® mixer, or an in-line type mixer, such as a SILVERSON® mixer. After the sol has been sufficiently pumped or otherwise thoroughly mixed into the reaction vessel, the emulsion can be continued to mix for a period of time sufficient to maintain a stable emulsion. For example, in some embodiments, mixing can be continued for a period of time from about 1 minute to about 1 hour.

[0053] After the formation of the emulsion, the process proceeds to step 103, where the pH of the emulsion is optionally adjusted. The pH can be adjusted using a basic compound. For example, any base known or hereafter discovered can be used to adjust the pH in the various embodiments described herein. In various embodiments, the base can be selected from the group consisting of NaOH, aqueous ammonia, ammonium hydroxide (e.g., NH4OH), KOH, Na2CO3, TMAOH, NaAlO2, and mixtures thereof. Furthermore, the base used can be in the form of a solution having a concentration ranging from 0.2 to 50 percent. In various embodiments, the above-mentioned base can have a pH of at least 7, such as from about 8 to about 14, such as from about 9 to about 13. The amount of basic compound used is determined by the target pH to be reached. For example, in some embodiments, the basic compound is added until the pH reaches a value of about 3 or more, in some embodiments about 4 or more, in some embodiments about 5 or more, in some embodiments about 6 or more, in some embodiments about 7 or more, and in some embodiments about 8 or more. The pH typically reaches about 12 or less, in some embodiments about 11 or less, in some embodiments about 10 or less, and in some embodiments about 9 or less. For example, in some embodiments, ammonium hydroxide is added until the pH reaches about 3 to about 10, e.g., about 5 to about 9. The emulsion can be continuously mixed as the basic compound is added and for a short period thereafter to facilitate pH stabilization. Optionally, the mixing speed can be reduced at this stage. For example, in some embodiments, the mixing speed is reduced to about 10% to about 60% of the mixing speed used to form the emulsion.

[0054] It should be understood that the pH is not necessarily adjusted and that step 103 is optional. The pore characteristics of the resulting silica particles can be controlled by adjusting the pH of the emulsion during gelation. Thus, the pH should be adjusted to the level required to obtain the desired pore characteristics. Thus, in some cases, the pH does not need to be adjusted at all.

[0055] After the optional pH adjustment step, the process can proceed to step 104, where the silica is gelled. The gelling step can optionally include adding water to the emulsion and optionally continuously mixing while increasing the temperature. The volume of water added at this stage is not critical and can be from about 0.25 to about 10 times the volume of the mixture in the vessel. In other embodiments, no water is added.

[0056] The gelation temperature can range from about 50° C. to about 95° C., in some embodiments from about 70° C. to about 90° C., and in some embodiments from about 75° C. to about 85° C. The mixing speed can be maintained at a speed similar to that of step 103. This temperature and mixing speed can be maintained for a time sufficient to gel the silica. For example, in some embodiments, the gelation time can be from about 20 minutes to about 2 hours, such as from about 30 minutes to about 90 minutes.

[0057]

[0052] In some embodiments, the obtained silica gel can be aged prior to separation. In this case, the obtained silica gel is maintained at a temperature of about 50°C to about 95°C, in some embodiments, about 70°C to about 90°C, in some embodiments, about 75°C to about 85°C for a period of about 10 minutes to about 10 hours, in some embodiments, about 30 minutes to about 5 hours, in some embodiments, about 45 minutes to about 2 hours. The pH can optionally be adjusted during the aging step. In this way, the surface area and pore size can be adjusted in situ and the gel network can be strengthened.

[0058] After the gelation step, the process can proceed to separation at step 105. Any suitable method can be used to separate the solid silica gel particles from the oil and water phases of the mixture. For example, in some embodiments, mixing is discontinued such that the oil and surfactant separate from the formed silica particles. In some embodiments, the solid particles can be filtered from the mixture.

[0059]

[0054] The resulting silica particles can then be optionally washed in step 106, for example by stirring in acid, water, and / or alcohol. The particles can then be dried in step 107 using any suitable method. For example, in some embodiments, the particles can be dried at a temperature and for a time sufficient to remove a desired amount of moisture. In some embodiments, the particles can be dried in a vacuum oven at a temperature of about 40°C to about 80°C for about 30 minutes to about 24 hours. In some embodiments, the particles can be dried in a conventional oven at a temperature of about 90°C to about 130°C for about 30 minutes to about 24 hours. In some embodiments, the particles can be dried using a spray dryer. In other embodiments, the particles can be dried by flash drying or by co-evaporation with an organic solvent.

[0060]

[0055] In some embodiments, the emulsion is demulsified by adding a demulsifier to facilitate separation of the oil and surfactant from the emulsion. In some embodiments, the demulsifier is water or an acid, such as a mineral acid. For example, in some embodiments, deionized water or aqueous mineral acid is added to the emulsion as the demulsifier. For example, when an aqueous sulfuric acid composition is used as the demulsifier, the concentration of sulfuric acid can be about 1 wt.% to about 30 wt.%, and in some embodiments, about 5 wt.% to about 15 wt.%, of the total aqueous composition. The demulsifier can be added to the emulsion in a weight ratio of about 1:5 to about 5:1, and in some embodiments, about 1:2 to about 1:1, based on the weight of the emulsion.

[0061]

[0056] Demulsification can occur at elevated temperatures. For example, the temperature can be from about 50°C to about 95°C, in some embodiments from about 60°C to about 90°C, and in some embodiments from about 70°C to about 80°C. During demulsification, the mixture can optionally be agitated by any suitable means. For example, in some embodiments, after the demulsifier is added, the mixture is agitated at elevated temperature for about 30 minutes to about 5 hours, for example, from about 1 hour to about 3 hours. In other embodiments, the mixture is held at elevated temperature without agitation for about 30 minutes to about 5 hours, for example, from about 1 hour to about 3 hours.

[0062] After demulsification, the particles can be separated from the remaining mixture by any suitable means. For example, in some embodiments, the mixture can be transferred to a separatory funnel to separate the aqueous phase from the oil phase. The silica particles can then be separated from the remaining liquid. In some embodiments, for example, the particles can be repeatedly filtered and redispersed as necessary.

[0063] After separation, the particles can optionally be aged as shown in FIG. 1, step 106a. The particles can be aged at elevated temperature in an ammonia solution. In some embodiments, the particles are redispersed in an aqueous medium, heated, and combined with ammonium hydroxide for a suitable period of time. The pH of the particles redispersed in the aqueous medium can be about 1 to about 5, such as about 2 to about 4. The temperature of aging can be about 50° C. to about 95° C., in some embodiments about 70° C. to about 90° C., and in some embodiments about 75° C. to about 85° C. Ammonium hydroxide can be added until the pH of the solution reaches about 6 to about 9, such as about 7 to about 8. In some embodiments, the particles are aged for a period of about 10 minutes to about 10 hours, in some embodiments about 30 minutes to about 5 hours, and in some embodiments about 45 minutes to about 2 hours.

[0064]

[0059] When the particles are aged in such a solution, they can then be filtered and dried. For example, in some embodiments, the particles can be filtered from the ammonia solution, redispersed in water if necessary, and then filtered and dried to remove the water and any solvent to form a powder. In some embodiments, after filtering from the ammonia solution, the particles can be redispersed in deionized water and then dried at an elevated temperature for a suitable period of time. Any suitable temperature can be used to dry the particles. In some embodiments, for example, the particles can be dried at a temperature of about 50°C to about 250°C, in some embodiments about 80°C to about 200°C, in some embodiments about 100°C to about 150°C, for a period of about 1 hour to about 48 hours, for example about 5 hours to about 24 hours, although the time and temperature are not critical.

[0065]

[0060] The emulsification process used to form the porous silica particles can provide additional advantages over conventional processes. For example, in conventional processes to produce porous silica gel particles having a desired particle size, a grinding step is typically used. This grinding step tends to produce very small silica particles, referred to as "fines." Advantageously, however, the methods disclosed herein produce particles having a desired particle size, and grinding is not required.

[0066] During the above process, silica gel particles are formed within the emulsion droplets to provide porous spherical silica particles. Each particle contains a rigid network of amorphous silica. Thus, the particles tend to be highly spherical. One way to measure the sphericity of the particles is to take images of many particles and calculate the aspect ratio of each particle using the largest and smallest diameters of each particle that can be determined from the images. The average aspect ratio of the particles can then be calculated using the aspect ratios of the individual particles. The aspect ratio is an indicator of sphericity. Particles with low aspect ratios are more spherical than particles with higher aspect ratios. In this regard, the particles formed by any of the above processes can be highly spherical and have a low average aspect ratio, for example, about 1.2 or less, in some embodiments about 1.17 or less, in some embodiments about 1.15 or less, in some embodiments about 1.12 or less, and in some embodiments about 1.1 or less. For example, in some embodiments, at least 75% of the particles have an aspect ratio of about 1.2 or less, such as about 1.1 or less. In some embodiments, at least 50% of the particles have an aspect ratio of about 1.1 or less. The aspect ratio is typically about 1.0 or more.

[0067] As explained above, the highly spherical porous silica particles can be used in a variety of different applications. For example, the silica particles can be used as catalyst supports, insulating materials, toners, food additives, medical diagnostic agents, paint fillers, cosmetic fillers, resin fillers, chromatography media, adsorbents, desiccants, etc.

[0068]

[0063] The present disclosure may be better understood with reference to the following examples. EXAMPLES

[0069] Test method:

[0065] Surface area, pore volume, and average pore diameter were measured by nitrogen adsorption. The instrument used for the analysis was an autosorb iQ2 TPX from Quantachrome Instrument. The nitrogen adsorption method is known as BET and is described in S. Brunauer, PH Emmett and E. Teller, J. Am. Chem. Soc., 1938, 60, 309.

[0070] Prior to analysis, the samples were activated in vacuum at a temperature of 400°C for 30 min. Surface areas were calculated from multipoint values ​​of nitrogen volumetric uptake in the adsorption branch at low partial pressures [P / Po = 0.05-0.15]. The adsorption branch of the isotherm was stopped at a partial pressure of P / Po = 0.995, and then the descending branch of the isotherm was measured. Pore volumes were calculated by applying the Gurvich law at P / Po = 0.995. Pore diameters are reported as calculated BJH desorption mean diameters.

[0071]

[0067] The silica gels of this invention are typical mesoporous materials (pore size 2-50 nm, IUPAC definition) and usually show type IV isotherms (IUPAC classification). Therefore, nitrogen porosimetry is a suitable method for characterization, and the determination of surface area using the BET method and pore volume from nitrogen adsorption and desorption isotherms using the BJH method are well-established and suitable methods used in this invention.

[0072]

[0068] The mean particle size (D50) and particle size distribution were measured after 2 minutes of sonication by using a Malvern 3000 particle size analyzer from Brightwell Technologies Inc. The measurements were performed using a refractive index of 1.49.

[0073] Aspect ratios were determined from SEM micrographs using Image-Pro Premier software. For each particle in the sample image, the aspect ratio was calculated by dividing the longest diameter by the shortest diameter. The aspect ratios of the individual particles in each sample were then averaged to determine the average aspect ratio of the particles within the sample. For each sample for which an aspect ratio is provided, approximately 150 particles were used in the calculation.

[0074] Example 1

[0070] Porous spherical silica material was obtained using an emulsification process. First, a sol was prepared by reacting sodium silicate with mineral acid. The sol was prepared by adding 2829 g of sodium silicate (14 wt.%) to 850 g of acid (25 wt.% H2SO4) at a flow rate of 150 ml / min at a temperature of 15°C and pH 1.5, and mixing with a DISPERMAT® overhead mixer at 500 rpm for 10 minutes. 3500 g of the sol was mixed with mineral oil (3500 g) and surfactant (sorbitan monooleate, 245 g). An emulsion was prepared by continuously passing the mixture through a SILVERSON® in-line mixer at a flow rate of 3.5 L / min and a speed of 1500 rpm for 1 minute. The gelation process was controlled by adjusting the pH to 5.5 by adding ammonium hydroxide to the emulsion. The temperature was then increased to 60°C and aged at 60°C for 1 hour. Then 3000 g of 5 wt.% sulfuric acid was added and the mixture was demulsified at 250 rpm at 60°C for 1 hour. After demulsification, the mixture was cooled and the oil phase was separated from the aqueous phase. The aqueous phase containing the silica particles was collected and the silica particles were filtered from the aqueous phase. The silica particles were repeatedly washed by reslurrying the particles in water at 50°C. This process was continued until the pH of the slurry reached 4. The particles were then dried in a spray dryer. The resulting particles were spherical porous silica with a D50 particle size of 20 μm and a span of 1.4. The BET surface area of ​​the resulting particles was 618 m 2 / g, pore volume was 1.4 ml / g, and average pore diameter was about 89 Å. An image of the particles is shown in FIG. 2. The average aspect ratio is 1.08. The properties of the obtained silica particles are summarized in Table 1 below.

[0075] Example 2

[0071] Porous spherical silica material was obtained using an emulsification process. First, a sol was prepared by reacting sodium silicate with mineral acid. The sol was prepared by adding 2869 g of sodium silicate (14 wt.%) to 850 g of acid (25 wt.% H2SO4) at a flow rate of 200 ml / min at a temperature of 15°C and pH 1.5, and mixing with a DISPERMAT® overhead mixer at 500 rpm for 10 minutes. 3500 g of the sol was mixed with mineral oil (3500 g) and surfactant (sorbitan monooleate, 245 g). An emulsion was prepared by continuously passing the mixture through a SILVERSON® in-line mixer at a flow rate of 3.5 L / min for 1.5 minutes. The gelation process was controlled by adjusting the pH to 6 by adding ammonium hydroxide to the emulsion. The temperature was then increased to 60°C and aged at 60°C. Then 3000 g of 5 wt.% sulfuric acid was added and the mixture was demulsified at 250 rpm at 60°C for 1 hour. After demulsification, the mixture was cooled and the oil phase was separated from the aqueous phase. The aqueous phase containing the silica particles was collected and the silica particles were filtered from the aqueous phase. The silica particles were repeatedly washed with water at 50°C by reslurrying the particles in water. This process was continued until the pH of the slurry reached 4. The particles were then dried in a spray dryer. The resulting particles were spherical porous silica with a D50 particle size of 35 μm and a span of 1.5. The BET surface area of ​​the resulting particles was 551 m 2 / g, pore volume was 1.3 ml / g, and average pore diameter was about 97 Å. An image of the particles is shown in FIG. 3. The average aspect ratio was 1.1. The properties of the obtained silica particles are summarized in Table 1 below.

[0076] Example 3

[0072] Porous spherical silica material was obtained using an emulsification process. First, a sol was prepared by reacting sodium silicate with mineral acid. The sol was prepared at a temperature of 15°C and pH of 1.5 by adding 200g sodium silicate (14wt.%) to 53g acid (18.5% HCl) at a flow rate of 10ml / min and mixing with an overhead mixer at 960 rpm for 20 minutes. The sol was then pumped into a mixture of mineral oil (300g) and surfactant (sorbitan monooleate, 15g). An emulsion was prepared by continuously mixing the mixture at a speed of 960 rpm and temperature (60°C) for 10 minutes with an overhead mixer. The gelation process was controlled by adjusting the pH by adding 2.9g ammonium hydroxide to the emulsion. The emulsion was then mixed at 250 rpm for 5 minutes. 400ml water was added to the emulsion. The temperature was then increased to 80°C. The emulsion was mixed at 250 rpm for 1 hour for gelation. After gelation, the mixture was cooled for 30 minutes to allow the oil phase to separate from the water phase. The water phase containing the silica particles was collected and the silica particles were filtered from the water phase. The silica particles were washed with 200 ml water at pH 4, 60°C while mixing at 250 rpm for 40 minutes and then filtered. The washing process was repeated two more times. The particles were then washed with isopropanol and then dried in a vacuum oven at 60°C for 1 hour. The resulting particles were spherical porous silica with a D50 particle size of 14 μm and a span of 1.5. The BET surface area of ​​the resulting particles was 456 m 2 / g, pore volume was 1.5 ml / g, and average pore diameter was about 101 Å. An image of the particles is shown in Figure 4. The properties of the obtained silica particles are summarized in Table 1 below.

[0077] Example 4

[0073] Porous spherical silica material was obtained using an emulsification process. First, a sol was prepared by reacting sodium silicate with mineral acid. The sol was prepared by adding 253 g of sodium silicate (14 wt.%) to 50.5 g of acid (18.5% HCl) at a flow rate of 10 ml / min at a temperature of 15°C and pH 1.5, and mixing with an overhead mixer at 960 rpm for 20 minutes. The sol was then pumped into a mixture of oil (150 g) and surfactant (sorbitan monooleate, 10 g). An emulsion was prepared by continuously mixing the mixture at a speed of 960 rpm and a stable temperature (60°C) for 10 minutes using an overhead mixer. The gelation process was controlled by adjusting the pH by adding 2.4 g of ammonium hydroxide to the emulsion. The emulsion was then mixed at 250 rpm for 5 minutes. 400 ml of water was added to the emulsion. The temperature was then increased to 80°C. The emulsion was mixed at 250 rpm for 1 hour for gelation. After gelation, the mixture was cooled for 30 minutes to allow the oil phase to separate from the water phase. The water phase containing the silica particles was collected and the silica particles were filtered from the water phase. The silica particles were washed with 200 ml of water at pH 4, 60°C while mixing at 250 rpm for 40 minutes and then filtered. The washing process was repeated two more times. The particles were then washed with isopropanol and then dried in a vacuum oven at 60°C for 1 hour. The resulting particles were spherical porous silica with a D50 particle size of 17 μm and a span of 1.3. The BET surface area of ​​the resulting particles was 917 m 2 / g, pore volume was 1.9 ml / g, and average pore diameter was about 101 Å. An image of the particles is shown in Figure 5. The properties of the obtained silica particles are summarized in Table 1 below.

[0078] Example 5

[0074] Porous spherical silica material was obtained using an emulsification process. First, a sol was prepared by reacting sodium silicate with mineral acid. The sol was prepared by adding 201 g of sodium silicate (14 wt.%) to 53.5 g of acid (18.5% HCl) at a flow rate of 10 ml / min at a temperature of 15°C and pH 1.5, and mixing with an overhead mixer at 960 rpm for 20 minutes. The sol was then pumped into a mixture of oil (91 g) and surfactant (sorbitan monooleate, 7.7 g). An emulsion was prepared by continuously mixing the mixture with an overhead mixer at a speed of 960 rpm and a stable temperature (60°C) for 10 minutes. The gelation process was controlled by adjusting the pH by adding 1.0 g of ammonium hydroxide to the emulsion. The emulsion was mixed at 250 rpm for another 5 minutes. 400 ml of water was added to the emulsion. The temperature was then increased to 80°C. The emulsion was mixed at 250 rpm for 1 hour for gelation. After gelation, the mixture was cooled for 30 minutes to allow the oil phase to separate from the water phase. The water phase containing the silica particles was collected and the silica particles were filtered from the water phase. The silica particles were washed with 200 ml of water at pH 4, 60°C while mixing at 250 rpm for 40 minutes and then filtered. The washing process was repeated two more times. The particles were then washed with isopropanol and dried in a vacuum oven at 60°C for 1 hour. The resulting particles were spherical porous silica with a D50 particle size of 9 μm and a span of 1.1. The BET surface area of ​​the resulting particles was 505 m 2 / g, pore volume was 2.5 ml / g, and average pore diameter was about 189 Å. An image of the particles is shown in Figure 6. The properties of the obtained silica particles are summarized in Table 1 below.

[0079] Example 6

[0075] Porous spherical silica material was obtained using an emulsification process. First, a sol was prepared by reacting sodium silicate with mineral acid. The sol was prepared by adding 805 g of sodium silicate (22.5 wt.%) to 455 g of acid (25 wt.% H2SO4) at a flow rate of 80 ml / min at a temperature of 15°C and pH 1.5, and mixing with a DISPERMAT® overhead mixer at 500 rpm for 10 minutes. 1000 g of the sol was mixed with mineral oil (370 g) and surfactant (sorbitan monooleate, 25 g). An emulsion was prepared by continuously mixing with a DISPERMAT® overhead mixer at a speed of 1500 rpm for 30 minutes. The gelation process was controlled by adjusting the pH to 3.5 by adding ammonium hydroxide to the emulsion. The temperature was then increased to 70°C and mixed at 70°C for 1 hour. Then 2000 g of 10 wt.% sulfuric acid was added and the mixture was demulsified at 250 rpm at 70° C. for 30 minutes. After demulsification, the mixture was cooled and the oil phase was separated from the water phase. The water phase containing the silica particles was collected and the silica particles were filtered from the water phase. The silica particles were repeatedly washed by reslurrying the particles in water with 1500 g of water at 50° C. This process was repeated three times. The pore volume was then adjusted according to the alternative aging step (106a). The particles were redispersed in water at pH 3, and then the pH was adjusted to 7.6 at 70° C. for aging by adding ammonia. After aging for 1 hour, the particles were separated, pH washed with water and then collected by filtration. The particles were then dried in an oven at 130° C. for 10 hours. The resulting particles were spherical porous silica with a D50 particle size of 3.8 μm and a span of 0.9. The BET surface area of ​​the resulting particles was 526 m 2 / g, pore volume was 2.1 ml / g, and average pore diameter was about 151 Å. An image of the particles is shown in FIG. 7. The average aspect ratio is 1.03. The properties of the obtained silica particles are summarized in Table 1 below.

[0080] Example 7

[0076] Porous silica materials were obtained using an emulsification process. First, sodium silicate and acid were reacted to form a sol, which was then added to oil and surfactant to produce an emulsion. The sol was made by adding 2233 g of sodium silicate (14%) to acid (700 g, 25 wt.% sulfuric acid) at a flow rate of 150 ml / min at controlled temperature (below 25°C) and pH (below 1.5) and mixing at 500 rpm for 10 minutes. 2000 g of the sol was mixed with mineral oil (850 g) and surfactant (sorbitan monooleate, 50 g). The emulsion was made by continuous mixing with a DISPERMAT® overhead mixer at a speed of 1200 rpm for 15 minutes. The pH of the emulsion was adjusted to 3.5 by adding ammonium hydroxide to the emulsion to promote gelation. The emulsion was heated to 70°C and then mixed at 250 rpm for 1 hour. After reaction, 3000 g of 10 wt.% sulfuric acid was added to the emulsion and mixed at 80 °C for 30 min and 2 h for demulsification. The mixture was left for 30 min to allow the oil and surfactant to separate from the resulting silica particles. The mixture was then filtered to separate the oil and surfactant from the silica particles. The silica particles were then washed three times with 1500 g of water. An alternative aging step (106a) was performed to adjust the pore volume. The particles were redispersed in water at pH 3, and then ammonia was added to adjust the pH to 7-8 at 70 °C for aging. After aging, the particles were separated and redispersed at pH 4, then collected after filtration. The wet particles were dried in an oven at 130 °C for 10 h. The resulting particles had a D50 particle size of 6.7 μm and a span of 1.4. The average BET surface area of ​​the resulting particles was 652 m 2 / g, average pore volume was 1.2 ml / g, and average pore diameter was about 94 Å. An image of the particles is shown in FIG. 8. The average aspect ratio is 1.07. The properties of the obtained silica particles are summarized in Table 1 below.

[0081] Example 8

[0077] Porous silica materials were obtained using an emulsification process. First, sodium silicate was reacted with acid to make a sol, and then the sol was added to oil and surfactant to produce an emulsion. The sol was made by adding 3086 g of sodium silicate (14%) to acid (700 g, 25 wt.% sulfuric acid) at a flow rate of 100 ml / min at controlled temperature (below 25°C) and pH (below 1.5) and mixing at 500 rpm for 10 minutes. 2000 g of the sol was mixed with mineral oil (900 g) and surfactant (sorbitan monooleate, 50 g). The emulsion was made by continuous mixing for 30 minutes at a speed of 1000 rpm using a DISPERMAT® overhead mixer. The pH of the emulsion was adjusted to 3 by adding ammonium hydroxide to the emulsion to promote gelation. The emulsion was heated to 70°C and then mixed at 250 rpm for 1 hour. After reaction, 3000 g of 10 wt.% sulfuric acid was added to the emulsion and mixed at 80 °C for 30 min and 2 h for demulsification. The mixture was left for 30 min to allow the oil and surfactant to separate from the resulting silica particles. The mixture was then filtered to separate the oil and surfactant from the silica particles. The silica particles were then washed three times with 1500 g of water. An alternative aging step (106a) was performed to adjust the pore volume. The particles were redispersed in water at pH 3, and then ammonia was added to adjust the pH to 7-8 at 70 °C for aging. After aging, the particles were separated and redispersed at pH 4, then collected after filtration. The wet particles were dried in an oven at 130 °C for 10 h. The resulting particles had a D50 particle size of 38 μm and a span of 1.7. The average BET surface area of ​​the resulting particles was 549 m 2 / g, average pore volume was 1.0 ml / g, and average pore diameter was about 110 Å. An image of the particles is shown in FIG. 9. The average aspect ratio was 1.1. The properties of the obtained silica particles are summarized in Table 1 below.

[0082] Example 9

[0078] Porous silica materials were obtained using an emulsification process. First, sodium silicate and acid were reacted to form a sol, and then the sol was added to oil and surfactant to form an emulsion. The sol was made by adding 2411 g of sodium silicate (14%) to acid (700 g, 25 wt.% sulfuric acid) at a flow rate of 100 ml / min at controlled temperature (below 25°C) and pH (below 1.5) and mixing at 500 rpm for 10 minutes. 2000 g of the sol was mixed with mineral oil (750 g) and surfactant (sorbitan monooleate, 50 g). The emulsion was made by continuously mixing with a DISPERMAT® overhead mixer at a speed of 1200 rpm for 30 minutes. The emulsion was heated to 70°C and then mixed at 250 rpm for 1 hour. After the reaction, 3000 g of 10 wt.% sulfuric acid was added and the mixture was demulsified at 250 rpm and 80°C for 2 hours. After demulsification, the mixture was cooled and the oil phase was separated from the water phase. The water phase containing the silica particles was collected and the silica particles were filtered from the water phase. The silica particles were repeatedly washed with water at 50°C by reslurrying the particles in 1500 g of water. This process was repeated three times. The particles were then dried in an oven at 130°C for 10 hours. The resulting particles were spherical porous silica with a D50 particle size of 30 μm and a span of 1.7. The BET surface area of ​​the resulting particles was 750 m 2 / g, pore volume was 0.5 ml / g, and average pore diameter was about 33 Å. An image of the particles is shown in FIG. 10. The average aspect ratio is 1.11. The properties of the obtained silica particles are summarized in Table 1 below.

[0083] Table 1 summarizes the properties of the silica particles produced in Examples 1-9.

[0084] [Table 1]

[0085] Certain embodiments

[0081] Embodiment 1. A method for forming porous spherical silica, comprising the steps of: a. mixing an alkali silicate with a mineral acid at a pH and temperature sufficient to form a silica sol; b. mixing the silica sol with an oil and a surfactant to form an emulsion; c. adding an alkaline solution to the emulsion for a time and at a temperature sufficient to form a gel; d. adding a demulsifier and heating at a temperature sufficient to separate the porous spherical silica particles from the oil; e. washing and optionally aging the particles; f. drying the porous spherical silica particles; A method comprising:

[0086]

[0082] Embodiment 2. The method of embodiment 1, wherein the alkali silicate is sodium silicate.

[0083] Embodiment 3. The method of embodiment 1 or embodiment 2, wherein the mineral acid is sulfuric acid or hydrochloric acid.

[0087]

[0084] Embodiment 4. The method of any one of embodiments 1-3, wherein the oil comprises mineral oil.

[0085] Embodiment 5. The method of any one of embodiments 1 to 4, wherein the surfactant comprises a nonionic surfactant.

[0088]

[0086] Embodiment 6. The method of embodiment 5, wherein the surfactant comprises a sorbitan ester.

[0087] Embodiment 7. The method of embodiment 6, wherein the surfactant comprises sorbitan oleate.

[0088] Embodiment 8. The method of any one of embodiments 1 to 7, wherein the alkaline solution comprises ammonium hydroxide.

[0089]

[0089] Embodiment 9. The method of any one of embodiments 1 to 8, wherein the emulsion is maintained at a temperature of about 40° C. to about 90° C. for about 0.25 to about 2 hours prior to adding the demulsifier.

[0090] Embodiment 10. The method of any one of embodiments 1-9, wherein the alkaline solution is added until the pH reaches a level of about 5 to about 10.

[0090]

[0091] Embodiment 11. The method of embodiment 10, wherein the alkaline solution is added until the pH reaches a level of about 6 to about 9.

[0092] Embodiment 12. The method of any one of embodiments 1 to 11, wherein the silica sol is formed at a temperature below 25° C.

[0091]

[0093] Embodiment 13 The method of any one of embodiments 1 to 12, wherein the particles are aged after washing and before drying.

[0094] Embodiment 14. The method of embodiment 13, wherein the particles are aged at a pH of about 7 to about 9 and a temperature of about 60° C. to about 90° C. for a period of about 1 to about 4 hours.

[0092]

[0095] Embodiment 15. The method of any one of embodiments 1 to 14, wherein the emulsion is formed by mixing a silica sol with a mixture comprising an oil and a surfactant.

[0096] Embodiment 16. The method of embodiment 15, wherein the concentration of the surfactant in the surfactant / oil mixture ranges from about 3 wt. percent to about 25 wt. percent of the mixture.

[0093]

[0097] Embodiment 17. The method of embodiment 15, wherein the concentration of the surfactant in the surfactant / oil mixture ranges from about 4 wt. percent to about 15 wt. percent of the mixture.

[0098] Embodiment 18. The method of embodiment 15, wherein the concentration of the surfactant in the surfactant / oil mixture ranges from about 5 wt. percent to about 8 wt. percent of the mixture.

[0094]

[0099] Embodiment 19. The method of any one of embodiments 1 to 18, wherein the ratio of silica sol to surfactant / oil mixture ranges from about 1:5 to about 5:1.

[0100] Embodiment 20. The method of any one of embodiments 1 to 19, wherein the ratio of silica sol to surfactant / oil mixture ranges from about 1:3 to about 4:1.

[0095]

[0101] Embodiment 21. The method of any one of embodiments 1 to 20, wherein the ratio of silica sol to surfactant / oil mixture ranges from about 1:2 to about 2:1.

[0102] Embodiment 22. The method of any one of embodiments 1 to 21, wherein the demulsifier comprises a mineral acid.

[0096]

[0103] Embodiment 23. A silica material formed by the method of any one of embodiments 1 to 22, comprising: The silica gel composition comprises a plurality of single silica gel particles, each particle comprising an amorphous network, the particles having an average aspect ratio of about 1.2 or less, a pore volume of about 0.5 cc / g to about 2.5 cc / g, and a pore size of about 300 m 2 / g~about 800m 2 / g surface area; and a median particle size of about 3 μm to about 40 μm.

[0097]

[0104] Embodiment 24. A silica material formed by the method of any one of embodiments 1 to 22, The silica gel composition comprises a plurality of single silica gel particles, each particle comprising an amorphous network, the particles having an average aspect ratio of about 1.2 or less, a pore volume of about 0.8 cc / g to about 2.0 cc / g, and a pore size of about 400 m 2 / g~about 700m 2 / g surface area; and a median particle size of about 8 μm to about 40 μm.

[0098]

[0105] Embodiment 25. The silica material of embodiment 23 or embodiment 24, wherein the silica particles have a span of about 2.0 or less.

[0106] Embodiment 26. The silica material of embodiment 23 or embodiment 24, wherein the silica particles have an average pore size of about 30 to about 250 angstroms.

Claims

1. A method for forming porous spherical silica, a. A step of mixing an alkali silicate with a mineral acid at a pH and temperature sufficient to form a silica sol, b. A step of mixing silica sol with oil and surfactant to form an emulsion, c. The step of adding an alkaline solution to the emulsion for a sufficient time and temperature to form a gel, d. Adding a deemulsifier and heating to a temperature sufficient to separate the porous spherical silica particles from the oil, e. A step of washing the particles and, if necessary, aging them, f. A step of drying porous spherical silica particles and Includes, method.

2. The method according to claim 1, wherein the alkali silicate is sodium silicate.

3. The method according to claim 1, wherein the mineral acid is sulfuric acid or hydrochloric acid.

4. The method according to claim 1, wherein the oil contains mineral oil.

5. The method according to claim 1, wherein the surfactant includes a nonionic surfactant.

6. The method according to claim 5, wherein the surfactant comprises a sorbitan ester.

7. The method according to claim 6, wherein the surfactant comprises sorbitan oleate.

8. The method according to claim 1, wherein the alkaline solution contains ammonium hydroxide.

9. The method according to claim 1, wherein the emulsion is maintained at a temperature of approximately 40°C to approximately 90°C for approximately 0.25 to approximately 2 hours before the addition of a deemulsifier.

10. The method according to claim 1, wherein an alkaline solution is added until the pH reaches a level of approximately 5 to approximately 10.

11. The method according to claim 10, wherein an alkaline solution is added until the pH reaches a level of approximately 6 to approximately 9.

12. The method according to claim 1, wherein the silica sol is formed at a temperature of less than 25°C.

13. The method according to claim 1, wherein the particles are aged after washing and before drying.

14. The method according to claim 13, wherein the particles are aged at a pH of approximately 7 to approximately 9 and a temperature of approximately 60°C to approximately 90°C for a period of approximately 1 to approximately 4 hours.

15. The method according to claim 1, wherein the emulsion is formed by mixing a mixture containing oil and a surfactant with a silica sol.

16. The method according to claim 15, wherein the concentration of the surfactant in the surfactant / oil mixture is in the range of about 3 wt. percent to about 25 wt. percent of the mixture.

17. The method according to claim 15, wherein the concentration of the surfactant in the surfactant / oil mixture is in the range of about 4 wt. percent to about 15 wt. percent of the mixture.

18. The method according to claim 15, wherein the concentration of the surfactant in the surfactant / oil mixture is in the range of about 5 wt. percent to about 8 wt. percent of the mixture.

19. The method according to claim 1, wherein the ratio of silica sol to surfactant / oil mixture is in the range of about 1:5 to about 5:

1.

20. The method according to claim 1, wherein the ratio of silica sol to surfactant / oil mixture is in the range of about 1:3 to about 4:

1.

21. The method according to claim 1, wherein the ratio of silica sol to surfactant / oil mixture is in the range of about 1:2 to about 2:

1.

22. The method according to claim 1, wherein the deemulsifier contains a mineral acid.

23. A silica material formed by the method of any one of claims 1 to 22, comprising a plurality of single silica gel particles, Each particle contains an amorphous network structure, with an average aspect ratio of approximately 1.2 or less, a pore volume of approximately 0.5 cc / g to approximately 2.5 cc / g, and a pore size of approximately 300 m ２ / g ~ approx. 800m ２ Surface area per g; and having a median particle size of approximately 3 μm to approximately 40 μm. Silica material.

24. A silica material formed by the method of any one of claims 1 to 22, comprising a plurality of single silica gel particles, Each particle contains an amorphous reticular structure, with an average aspect ratio of approximately 1.2 or less, a pore volume of approximately 0.8 cc / g to approximately 2.0 cc / g, and a pore size of approximately 400 m ２ / g ~ approx. 700m ２ Surface area per g; and median particle size of approximately 8 μm to approximately 40 μm, Silica material.

25. The silica material according to claim 23, wherein the silica particles have a span of about 2.0 or less.

26. The silica material according to claim 23, wherein the silica particles have an average pore size of about 30 to about 250 angstroms.

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