Filter aids for treating oil and methods of making and using same

Abstract

The invention relates to filter aids for treating oil and methods of making and using the same. The present disclosure includes compositions and methods for filtering oils, such as for removing free fatty acids (FFA) from oils for cooking. In an example, a composition may include a filter aid including an alkali metal silicate and a composite material including a silicate mineral at least partially coated with an inorganic silica or silicate. In another example, the filter aid comprises an alkali metal silicate and a silicate mineral, where at least a portion of the alkali metal silicate is present as a coating on the silicate mineral, and where the ratio of the alkali metal silicate to the silicate mineral in the filter aid is in the range of about 1: 4 to 4: 1 by weight. In still another example, the filter aid includes an alkali metal silicate, a silicate mineral, and an adsorbent. A method of filtering an oil may include combining the oil with a filter aid, optionally heating the mixture, and separating at least a portion of the filter aid from the oil, thereby removing at least a portion of FFA from the oil.

Description

[0001] This application is a divisional application of the parent application with application number 201880080388.7. The filing date of the parent application is December 14, 2018; the invention title is "Filter Aid for Treating Oil and Its Preparation and Use Methods". Claims for Priority This PCT international application claims the benefit of the priority of U.S. Provisional Application No. 62 / 598728, filed on December 14, 2017, the subject matter of which is incorporated herein by reference in its entirety. Technical Field

[0002] Embodiments of the present disclosure generally relate to compositions used as filter aids (such as for filtering oil). The composition may comprise a filter aid, which comprises a composite silicate material and an alkali metal silicate. Background Art Using cooking oil to fry food results in several forms of oil contamination, such as by hydrolysis, oxidation, and / or polymerization. Moisture present in the food during cooking forms steam, which together with oxygen can initiate chemical reactions to produce free fatty acids (FFAs). An exemplary mechanism for the production of FFAs from triglycerides is shown below.

[0004] The amount of FFA in cooking oil tends to increase with use (repeated frying). FFAs have an adverse effect on the quality of the oil, such as reducing the oxidative stability of the oil and / or causing off-flavors in the food. Therefore, the FFA content can provide an indicator of the oil quality. Thus, compositions and methods capable of reducing the FFA content of cooking oil may be of interest. Summary of the Invention The present disclosure includes a filter aid, methods of using it, and methods of preparing it. For example, in one instance, the present disclosure includes a filter aid comprising: (a) an alkali metal silicate, and (b) a composite material comprising a silicate mineral at least partially coated with inorganic silica or silicate. In another instance, the present disclosure includes a filter aid comprising: (a) an alkali metal silicate, and (b) a silicate mineral, wherein at least a portion of the alkali metal silicate is present as a coating on the silicate mineral, and wherein the ratio of the alkali metal silicate to the silicate mineral in the filter aid is in the range of about 1:4 to 4:1 by weight. In still another instance, the present disclosure includes a filter aid comprising an alkali metal silicate, a silicate mineral, and an adsorbent.

[0006] In one example, the present disclosure includes a filter aid comprising an alkali metal silicate and a composite material, the latter comprising a silicate mineral at least partially coated with inorganic silica or a silicate. The alkali metal silicate may include, for example, sodium silicate, potassium silicate, or a mixture thereof. In some examples, the alkali metal silicate includes sodium metasilicate, such as sodium metasilicate pentahydrate, sodium metasilicate nonahydrate, anhydrous sodium metasilicate, or a mixture thereof. For example, the filter aid may comprise from about 10% to about 75% by weight of sodium metasilicate pentahydrate.

[0007] In one example, the filter aid comprises from about 10 to about 70% by weight of an alkali metal silicate. In another example, the filter aid comprises from about 10% to about 60% by weight of an alkali metal silicate, from about 10% to about 60% by weight of a silicate mineral, and from about 10 to about 60% by weight of an adsorbent.

[0008] Additionally or alternatively, the silicate mineral of the filter aid may include biogenic silica (such as diatomaceous earth), perlite, pumice, scoria, obsidian, rhyolite, volcanic ash, or a combination thereof. Further, for example, the inorganic silica or silicate may include silica gel, sodium silicate, magnesium silicate, or a combination thereof. In at least one example, the inorganic silica or silicate is precipitated on the surface of the silicate mineral. According to some examples herein, the composite material of the filter aid comprises from about 50% to about 95% by weight of biogenic silica and / or from about 5% to about 80% by weight of inorganic silica or silicate, relative to the total weight of the composite material. In some examples, the alkali metal silicate may be present as loose particles (such as a powder) incorporated with the composite material to form the filter aid. In some examples, the alkali metal silicate may include a compound or a mixture of compounds different from the inorganic silica or silicate of the composite material.

[0009] In one example, the filter aid may comprise at least one adsorbent. In some examples, the adsorbent may be at least partially coated on the silicate mineral. In other examples, the adsorbent may be particulate material that is substantially not bound to the silicate mineral. In many examples, the adsorbent may be magnesium silicate.

[0010] The filter aid may have a permeability in the range of about 0.05 darcy to about 10.0 darcy and / or a BET surface area in the range of about 0.2 m 2 / g to about 450 m 2 / g. In some examples, the d 50 diameter of the particle size distribution of the composite material in the filter aid is in the range of about 5 μm to about 300 μm. Further, in some examples, the filter aid may have a bimodal particle size distribution. In some examples, the composite material may have a median pore size (4V / A) in the range of about 0.1 μm to about 10.0 μm and / or in the range of about 5 lb / ft 3- Approximately 30 lb / ft 3 The wet density within the range of. In at least one instance, relative to the total weight of the filter aid, the filter aid contains from about 0.5% to about 10% water by weight.

[0011] This disclosure further includes a composition comprising the filter aid discussed above and elsewhere herein. For example, relative to the total weight of the composition, the composition may contain at least 80% filter aid and from about 1.0% to about 10.0% water by weight. In some instances, the pH of the composition (such as an aqueous composition) is in the range of about 9.0 to about 13.0. In some instances, the composition is in the form of dry particulate matter. In another instance, relative to the total weight of the filter aid, the filter aid contains from about 0.5% to about 20% water by weight, such as from about 1% to about 10% water by weight.

[0012] This disclosure also includes a method of filtering oil using such a filter aid and / or composition. For example, the method may include combining the oil with the filter aid to form a mixture, the filter aid comprising an alkali metal silicate and a composite material comprising a silicate mineral at least partially coated with inorganic silica or silicate. As described above, the alkali metal silicate may include sodium silicate, potassium silicate, or a mixture thereof. For example, the filter aid may contain sodium metasilicate, such as sodium metasilicate pentahydrate, sodium metasilicate nonahydrate, anhydrous sodium metasilicate, or a mixture thereof.

[0013] According to some aspects of the present disclosure, the filtering method further includes heating the mixture comprising the oil and the filter aid. The oil may contain free fatty acids, such as from about 0.05% to about 10.0% free fatty acids by weight. The method may further include separating at least a portion of the filter aid from the oil, wherein the filter aid removes at least 50%, at least 65%, or at least 70% free fatty acids by weight from the oil. The oil may include edible oil, such as oil derived from animals and / or plants. In some instances, relative to the weight of the oil, the mixture contains from about 0.05% to about 10.0% filter aid.

[0014] This disclosure also includes a method of preparing such a filter aid. For example, the method may include preparing a composite material by at least partially coating a silicate mineral with inorganic silica or silicate and combining the composite material with an alkali metal silicate. The alkali metal silicate may include sodium silicate, potassium silicate, or a mixture thereof. For example, the alkali metal silicate may include sodium metasilicate, such as sodium metasilicate pentahydrate, sodium metasilicate nonahydrate, anhydrous sodium metasilicate, or a mixture thereof. Additionally or alternatively, the silicate mineral may include diatomaceous earth, wherein preparing the composite material includes precipitating inorganic silica or silicate on the surface of the diatomaceous earth. In at least one instance, the method further includes adding water to the filter aid such that, relative to the total weight of the filter aid, the filter aid contains from about 0.5% to about 10% water by weight.

[0015] In another example, a method for preparing a filter aid includes coating an alkali metal silicate on a silicate mineral matrix. In one example, the coating can be accomplished using a rotary mixer, a disk granulator. In another example, the coating can be accomplished using a spray drying process. In some examples, a method for preparing a filter aid can include mixing an adsorbent with an alkali metal silicate and a silicate mineral. Detailed Description Specific aspects of the present disclosure are described in more detail below. If there is a conflict with terms and / or definitions incorporated by reference, the terms and definitions provided herein shall control.

[0017] As used herein, the term "comprising," "including," or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, composition, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, composition, article, or apparatus. The term "exemplary" is used in the sense of "example" rather than "ideal."

[0018] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context dictates otherwise. The terms "about" and "approximately" mean nearly the same as the referenced number or value. The terms "about" and "approximately" as used herein are to be understood to cover a ±5% variation of the specified amount or value.

[0019] The present disclosure includes a filter aid that is used to filter oils (such as edible oils) or other oils used for cooking or frying to remove contaminants such as FFA. The filter aid herein can comprise at least one silica or silicate or a combination of multiple types of silica / silicates, which can be biogenic or inorganic.

[0020] In some examples herein, the filter aid comprises a silicate mineral that is at least partially coated or fully coated with silica or silicate to form a composite material, wherein the matrix optionally comprises a silicate material different from the coating. The coated silicate mineral can be further combined with another silicate compound (such as an alkali metal silicate, such as sodium silicate, such as sodium metasilicate).

[0021] In other examples, the filter aid comprises an alkali metal silicate-coated silicate mineral, such as diatomaceous earth coated with sodium silicate or perlite coated with sodium silicate. For example, the filter aid can comprise an alkali metal silicate and a silicate mineral, wherein at least a portion of the alkali metal silicate is present as a coating on the silicate mineral, and wherein the ratio of the alkali metal silicate to the silicate mineral in the filter aid is in the range of about 1:4 to 4:1 by weight.

[0022] In other instances, the filter aid comprises an alkali metal silicate, a silicate mineral, and an adsorbent. The adsorbent can be, for example, an alkaline earth metal silicate such as magnesium silicate.

[0023] Without wishing to be bound by theory, it is believed that the combination of silicates in the filter aid can provide a functional synergy in filtering oils, for example to maintain or improve the quality of oils used in cooking such as frying oils. In some instances, the filtering can include combining the oil with the filter aid to form a mixture. Such filtering can allow the removal of FFA by neutralizing the FFA with the alkali metal silicate of the filter aid (such as sodium silicate) to form a salt: Equation 2 The FFA salt (commonly referred to as soap) can adsorb onto the coated silicate mineral particles of the filter aid. For example, the FFA salt can physically and / or chemically attach to the coated silicate mineral particles, allowing the removal of FFA by filtering the particles from the oil.

[0024] According to some aspects of the present disclosure, the filter aid comprises an alkali metal silicate such as sodium silicate, potassium silicate, or a mixture thereof. For example, the filter aid can comprise sodium silicate ((Na2SiO2) n O), where the molar ratio of SiO2:Na2O is in the range of 1.0 - 4.0. The alkali metal silicate can be hydrated or anhydrous. In some instances, the sodium silicate includes sodium metasilicate (Na2SiO3) having a SiO2:Na2O molar ratio of 1.0. For example, the filter aid can comprise anhydrous sodium metasilicate and / or a hydrated form of sodium metasilicate such as sodium metasilicate pentahydrate (Na2SiO3·5H2O), sodium metasilicate nonahydrate (Na2SiO3·9H2O), any other hydrated form, or a mixture thereof. In at least one instance, the sodium silicate includes sodium metasilicate pentahydrate. In at least one instance, the sodium silicate includes sodium metasilicate nonahydrate.

[0025] In some instances, the alkali metal silicate may be in powder form. For example, the filter aid further comprises particulate material (such as silicate mineral particles that are at least partially or fully coated with silica or silicate), such as a composite material. Thus, at least a portion of the alkali metal silicate may not be attached to the silicate mineral particles or otherwise associated with the coating of the silicate mineral particles. For example, the alkali metal silicate exists in the form of free particles. For example, the filter aid may comprise particles having a bimodal distribution (such as a particle size distribution corresponding to the free alkali metal silicate and the particle size distribution of the composite material). Further, for example, the alkali metal silicate may comprise a compound or a mixture of compounds different from the inorganic silica or silicate of the composite material. For example, the filter aid may comprise sodium silicate and / or potassium silicate, and the coating of the composite material may comprise silica gel. In another instance, the coating of the composite material may comprise sodium silicate, while the alkali metal silicate may comprise a sodium silicate different from the coating (such as different hydration forms, different molar ratios of SiO2 / Na2O, anhydrous versus hydrated, etc.).

[0026] In some instances, relative to the total weight of the filter aid, the filter aid may comprise from about 5% to about 80% by weight of the alkali metal silicate, such as from about 10% to about 75% by weight, from about 15% to about 70% by weight, from about 10% to about 20% by weight, from about 5% to about 25% by weight, from about 20% to about 60% by weight, from about 25% to about 50% by weight, from about 30% to about 65% by weight or from about 50% to about 75% by weight. Without being bound by theory, it is believed that the alkali metal silicate (such as sodium metasilicate) may provide a combination of base strength and moisture content that is particularly beneficial for neutralizing FFA in oil mixtures.

[0027] The particulate composite material of the filter aid may comprise silicate minerals that are at least partially or fully coated with one or more of silica, silicate, and / or aluminosilicate compounds. According to some aspects of the present disclosure, silicate minerals include mineral particles comprising one or more silicates and / or aluminosilicates, including vitreous minerals and materials derived from vitreous minerals. Exemplary silicates and aluminosilicates include (but are not limited to) diatomaceous earth, perlite, pumice, scoria, volcanic ash, calcined kaolin, montmorillonite, mica, shirasu, obsidian, rhyolite, rice husk ash, and combinations thereof.

[0028] Diatomaceous earth (also known as "DE" or "diatomite") is generally referred to as a sediment rich in biogenic silica (silica produced or caused by living organisms) in the form of diatomaceous siliceous cells. Diatoms are a variety of microscopic, single-celled, golden-brown algae, usually belonging to the class Bacillariophyceae, which have a magnificent siliceous skeleton with a variable and complex structure, including two valves that fit together like pillboxes in living diatoms. Diatomaceous earth can be formed from the remains of aquatic diatoms, and thus, deposits of diatomaceous earth may be located near current or former water bodies. Based on the source, these deposits are generally divided into two categories: freshwater and saltwater. Freshwater diatomaceous earth is usually mined from dry lake beds and is characterized by a low crystalline silica content and a high iron content. In contrast, saltwater diatomaceous earth is usually extracted from marine areas and is characterized by a high crystalline silica content and a low iron content.

[0029] Vitreous minerals, also known as "volcanic glass", are formed by the rapid cooling of siliceous magma or lava. Volcanic glass, such as perlite and pumice, often occurs in large deposits. Volcanic ash, when in a consolidated form, is usually referred to as "tuff" and includes small particles or fragments that can be in a vitreous form and are also characterized as vitreous minerals.

[0030] Perlite is a hydrated vitreous mineral containing a combination of silica, alumina, and other metals or metal oxides (such as sodium oxide and iron oxide). For example, perlite can contain approximately 70%-75% SiO2 by weight, approximately 12%-15% Al2O3 by weight, approximately 0.5%-2% Fe2O3 by weight, approximately 3%-5% Na2O by weight, approximately 3%-5% K2O by weight, approximately 0.4%-1.5% CaO by weight, and smaller amounts of other metals or metal oxides. The difference between perlite and other vitreous minerals can lie in its relatively high water content (e.g., approximately 2%-5% by weight), vitreous pearly luster, and characteristic concentric or arcuate onion-skin-like fractures. The Mohs hardness of perlite is generally greater than about 5, such as in the range of about 5.5 - about 7.0.

[0031] Expanded perlite refers to perlite that has been heated to cause thermal expansion through the evaporation of its internal water. For example, perlite can be rapidly heated to the point where the glass begins to soften (between about 750°C - 1100°C), and the water recombines and evaporates. As long as the glass is soft enough to stretch, the water vapor expands, causing small bubbles to form in the glass matrix, and the bubbles break and form smaller fragments with sharp edges.

[0032] Pumice is a vitreous mineral characterized by a mesoporous structure having, for example, pores or vesicles. The porous nature of pumice results in a relatively low apparent density, enabling it to float on water in many cases. Pumice typically contains about 60% to about 70% SiO2 by weight. Obsidian materials include vitreous minerals rich in silica. Obsidian glass can be subclassified according to its silica content, with rhyolitic obsidian (generally containing about 73% SiO2 by weight) being the most common. Rice husks contain sufficient silica to enable commercial ashing of their siliceous residue, which product is commonly referred to as rice husk ash. Certain sponges are also a concentrated source of silica, with their remnants potentially present as spicules in geological sediments.

[0033] According to some aspects of the present disclosure, silicate minerals include silicate materials such as biogenic silica. In some examples herein, silicate minerals can include diatomaceous earth, perlite, pumice, scoria, obsidian, pitchstone, volcanic ash, or combinations thereof. In some examples, silicate minerals include diatomaceous earth. In at least one example, silicate minerals include perlite, such as expanded perlite.

[0034] Silicate minerals can be treated with one or more silica, silicate, and / or aluminosilicate compounds, such as by partial coating or full coating. In some examples, the coating comprises inorganic silica and / or silicate. Exemplary inorganic silica / silicates that can be used in the coating include (but are not limited to) silica gel, sodium silicate, magnesium silicate, and combinations thereof. In at least one example, the inorganic silica / silicate precipitates on the surface of the silicate mineral. For example, the filter aids herein can comprise inorganic silica / silicate or a mixture of inorganic silica / silicates precipitated on particles (such as particles of diatomaceous earth, perlite, pumice, scoria, obsidian, pitchstone, volcanic ash, or combinations thereof). In at least one example, the coated silicate mineral includes diatomaceous earth particles at least partially or fully coated with sodium silicate, magnesium silicate, or a mixture of sodium silicate and magnesium silicate.

[0035] In at least one example, the composite material comprises silicate particles (such as diatomaceous earth particles) at least partially coated with magnesium silicate, and the alkali metal silicate includes sodium silicate and / or potassium silicate. In at least one example, the composite material comprises silicate particles (such as diatomaceous earth particles) at least partially coated with sodium silicate, and the alkali metal silicate includes a sodium silicate different from the sodium silicate of the coating. In still another example, the composite material comprises silicate particles (such as diatomaceous earth particles) at least partially coated with silica gel, and the alkali metal silicate includes sodium silicate, such as sodium metasilicate.

[0036] In some instances, the silica / silicate coating may account for about 5% to about 50% by weight of the silicate mineral coated in the composite material. For example, the filter aid may comprise a composite material, the composite material comprising about 20% to about 95% by weight of mineral particles and about 5% to about 80% by weight of inorganic silica / silicate that at least partially or completely coats the mineral particles. In some instances, the composite material comprises about 50% to about 95% by weight of biogenic silica (e.g., diatomaceous earth particles) or volcanic glass (e.g., perlite, pumice, scoria, obsidian, rhyolite, or volcanic ash particles) and a mixture of inorganic silicate or inorganic silicates precipitated on the biogenic silica or volcanic glass. In some instances, relative to the total weight of the composite material, the composite material comprises about 5% to about 80% by weight, about 10% to about 70% by weight, about 15% to about 50% by weight, or about 25% to about 40% by weight of inorganic silica / silicate or a mixture of inorganic silica / silicate, wherein the inorganic silica / silicate or the mixture of inorganic silica / silicate at least partially coats or completely coats the particles of biogenic silica or volcanic glass.

[0037] The mineral particles used as the matrix may undergo one or more processing steps, such as grinding and / or sizing, to provide a desired particle size distribution before coating. For example, the mineral particles may be ground so that the particles have a desired particle size distribution. Additionally or alternatively, the mineral particles may undergo one or more processing steps after coating. The particle size and other particle size characteristics mentioned in the present disclosure can be measured by any suitable measurement technique, such as the Sedigraph 5100 instrument provided by Micromeritics Corporation or the Microtrac Model X-100 provided by Leeds&Norththrup. Using such a measuring device, the size of a given particle is expressed as the diameter of a sphere of equivalent diameter, sometimes referred to as the equivalent spherical diameter or (ESD). The median particle size or d 50 value is the diameter at which 50% by weight of the particles have an ESD less than d 50 value. Similarly, the d 90 value is the diameter at which 90% by weight of the particles have an ESD less than d 90 value, and the d 10 value is the diameter at which 10% by weight of the particles have an ESD less than d 10 value. Consider other methods and / or devices for determining particle size.

[0038] According to some aspects of the present disclosure, the median particle diameter (d 50The value is in the range of about 1 μm - about 300 μm, such as about 5 μm - about 300 μm, about 100 μm - about 300 μm, about 150 μm - about 300 μm, about 1 μm - about 100 μm, about 5 μm - about 100 μm, about 10 μm - about 100 μm, about 50 μm - about 100 μm, about 1 μm - about 50 μm, about 5 μm - about 50 μm, about 10 μm - about 50 μm, about 1 μm - about 10 μm, about 5 μm - about 10 μm or about 1 μm - about 5 μm. For example, the d of the composite material 50 value is in the range of about 40 μm - about 300 μm, about 40 μm - about 250 μm, about 100 μm - about 250 μm, about 5 μm - about 150 μm, about 40 μm - about 140 μm, about 60 μm - about 120 μm, about 30 μm - about 60 μm, about 60 μm - about 90 μm, about 90 μm - about 120 μm, about 120 μm - about 150 μm, about 1 μm - about 40 μm, about 10 μm - about 40 μm, about 10 μm - about 30 μm or about 15 μm - about 25 μm.

[0039] Alternatively or additionally, the d of the silicate mineral or composite material 90 value can be in the range of about 50 μm - about 700 μm, such as about 300 μm - about 700 μm, about 300 μm - about 500 μm, about 100 μm - about 300 μm, about 200 μm - about 400 μm, about 50 μm - about 300 μm, about 100 μm - about 200 μm, about 200 μm - about 300 μm, about 50 μm - about 100 μm, about 60 μm - about 140 μm, about 70 μm - about 120 μm or about 80 μm - about 110 μm.

[0040] Alternatively or additionally, the d of the silicate mineral or composite material 10 value can be in the range of about 1 μm - about 30 μm, such as about 1 μm - about 10 μm, about 10 μm - about 20 μm, about 20 μm - about 30 μm, about 5 μm - about 15 μm, about 15 μm - about 25 μm, about 20 μm - about 25 μm, about 2 μm - about 20 μm, about 3 μm - about 15 μm, about 4 μm - about 12 μm, about 5 μm - about 10 μm, about 1 μm - about 5 μm or about 1 μm - about 3 μm.

[0041] Silicate minerals or composite materials can have a desired pore size or pore size distribution. One technique for describing the pore size distribution in a material is mercury intrusion porosimetry, which measures micron-scale pores using mercury intrusion under an applied isostatic pressure, such as those in silicate minerals. In this method, the material is surrounded by liquid mercury in a closed evacuated container, and the pressure is gradually increased. Before starting the mercury intrusion, the container is sealed and the pressure is reduced to a very low level. At low pressure, due to the high surface tension of liquid mercury, the mercury does not enter the sample. As the pressure increases, the mercury is forced into the sample, but first it enters the largest spaces where the curvature of the mercury surface is the lowest. As the pressure is further increased, the mercury is forced into the tighter spaces of the material. Eventually, all the voids will be filled with mercury. Nanoporous structures can be measured by nitrogen adsorption using a 2460 Surface Area and Porosity Analyzer (available from Micromeritics Instrument Corporation, Norcross, Ga., USA). Thus, a plot of total void volume versus pressure can be made. Therefore, this method can not only provide the total pore volume, but also distinguish the pore size distribution. Once the pore distribution has been estimated, an estimate of the surface area can be calculated based on the pore size and by assuming the pore shape (usually assumed to be spherical). The median pore size estimate can also be calculated based on volume or area. The median pore size (volume) is the pore size at the 50th percentile on the cumulative volume plot, and the median pore size (area) is the pore size at the 50th percentile on the cumulative area plot. The average pore size (diameter) is 4 times the ratio of the total pore volume to the total pore area (4V / A). In some examples, the median pore size (4V / A) of the composite material can be in the range of about 0.1 μm to about 10.0 μm, such as about 0.1 μm to about 5.0 μm, about 0.5 μm to about 5.0 μm, about 0.1 μm to about 1.0 μm, about 1.0 μm to about 10.0 μm, about 1.0 μm to about 5.0 μm, about 2.0 μm to about 5.0 μm, about 1.5 μm to about 8.0 μm, or about 5.0 μm to about 10.0 μm.

[0042] A filter component with a lower wet density can result in a product with a greater porosity, which may lead to higher filtration efficiency, provided that the true density remains relatively constant. According to some aspects, the wet density of the composite material can be in the range of about 5 lbs / ft 3 - about 30 lbs / ft 3 (corresponding to the range of about 80.1 kg / m 3 - about 480.6 kg / m 3 ). For example, the wet density of the composite material can be in the range of about 10 lbs / ft 3 - about 20 lbs / ft 3 or about 20 lbs / ft3 - Approximately 30 lbs / ft, approximately 15 lbs / ft 3 - Approximately 25 lbs / ft 3 , approximately 25 lbs / ft 3 - Approximately 35 lbs / ft 3 , approximately 15 lbs / ft 3 - Approximately 20 lbs / ft 3 , approximately 20 lbs / ft 3 - Approximately 25 lbs / ft 3 or approximately 25 lbs / ft 3 - Approximately 30 lbs / ft 3 within the range of. Since the wet density reflects the void volume of the adsorbent component used to hold substances during the filtration process, a lower wet density may indicate that the adsorbent component has a high void volume, thus being able to adsorb more components in the fluid.

[0043] The wet density can be measured by placing a sample of known weight (approximately 1.00 g - approximately 2.00 g) in a calibrated 15 mL centrifuge tube. Then add deionized water to make up a volume of approximately 10 mL. Thoroughly shake the mixture until all the samples are wetted and no powder remains. Add additional deionized water near the top of the centrifuge tube to rinse off any mixture adhering to the sides of the centrifuge tube due to shaking. Then centrifuge the centrifuge tube at 2500 RPM for 5 minutes on an IEC MP - 4R centrifuge (International Equipment Company; Needham Heights, Massachusetts, USA). After centrifugation, carefully remove the centrifuge tube without disturbing the solid and measure the level (volume) of the precipitate. Then calculate the wet density of the centrifuged sample by dividing the sample weight by the measured volume, for example in g / cm 3 (or in kg / m 3 or lbs / ft 3 etc.) based on the units used during the test.

[0044] The filter aids of the present invention may have properties beneficial to the filtration of oils and oil mixtures. According to some examples herein, the BET surface area (i.e., the specific surface area calculated according to the Brunauer, Emmett, and Teller (BET) theory) of the filter aids is in the range of approximately 0.2 m 2 / g - approximately 450 m 2 / g, such as approximately 5 m 2 / g - approximately 400 m 2 / g, approximately 25 m 2 / g - approximately 250 m 2 / g, approximately 50 m2 / g - about 150 m 2 / g, about 100 m 2 / g - about 200 m 2 / g, about 75 m 2 / g - about 150 m 2 / g, about 300 m 2 / g - about 450 m 2 / g, about 250 m 2 / g - about 300 m 2 / g, about 100 m 2 / g - about 150 m 2 / g or about 50 m 2 / g - about 300 m 2 within the range of / g.

[0045] According to some examples, the filter aid can have a permeability suitable for filtering non-aqueous liquids such as edible oils or other oils or oil mixtures used or useful in cooking. Permeability is typically measured in darcy units or darcies. A device designed to form a filter cake on a diaphragm from a suspension of the filter aid composition in water can be used, and then the time required for a specified volume of water to flow through a filter cake of known cross-sectional area and measured thickness can be measured to determine the permeability. For example, the permeability can be measured through a porous filter aid material 1 cm high and with a cross-section of 1 cm 2 while causing a fluid with a viscosity of 1 mPa·s to flow through the material at a flow rate of 1 cm 3 / sec under an applied pressure difference of 1 atmosphere. The principle for measuring permeability has previously been derived for porous media according to Darcy's law (see, for example, J. Bear, “The Equation of Motion of a Homogeneous Fluid: Derivations of Darcy’s Law,” in Dynamics of Fluids in Porous Media 161 - 177 (2nd ed. 1988)).

[0046] According to some examples, the permeability of the filter aid can be in the range of about 0.05 darcy - about 10.0 darcy. For example, the permeability of the filter aid can be in the range of about 0.1 darcy - about 10.0 darcy, about 0.1 darcy - about 5.0 darcy, about 0.1 darcy - about 3.0 darcy, about 0.5 darcy - about 2.5 darcy, about 0.5 darcy - about 1.5 darcy, about 1.0 darcy - about 2.0 darcy, about 0.1 darcy - about 1.0 darcy, about 0.5 darcy - about 1.0 darcy, about 1.0 darcy - about 2.5 darcy, about 0.05 darcy - about 1.0 darcy, or about 0.1 darcy - about 0.5 darcy.

[0047] According to some aspects of the present disclosure, the filter aid can be provided as a composition such as an aqueous suspension or slurry. In some examples, the composition can include water, such as at least 75% by weight or at least 80% by weight of water and from about 1.0% to about 10.0% by weight of the filter aid. For example, relative to the total weight of the composition, the composition can include from about 1.0% to about 5.0% by weight, from about 2.5% to about 7.5% by weight, from about 5.0% to about 7.5% by weight, from about 3.5% to about 8.0% by weight, or from about 3.5% to about 6.5% by weight of the filter aid. According to some aspects, relative to the total weight of the composition, the composition includes an aqueous suspension or slurry that contains 4.0% by weight, 4.5% by weight, 5.0% by weight, 5.5% by weight, or 6.0% by weight of the filter aid. The pH of such an aqueous composition can be in the range of about 9.0 to about 13.0, such as about 10.0 to about 13.0, about 11.0 to about 12.0, or about 12.0 to about 13.0.

[0048] The filter aid herein can be prepared, for example, by the following method: preparing a composite material (particulate material) by at least partially coating a silicate mineral with an inorganic silica / silicate (such as a silicate or silica gel), and combining the composite material with an alkali metal silicate (such as sodium metasilicate).

[0049] The composite material for preparing the filter aid can include precipitating an inorganic silicate on the surface of a silicate mineral, such as precipitating sodium silicate and / or magnesium silicate on the particles of diatomaceous earth, perlite), pumice, scoria, obsidian, rhyolite, volcanic ash, or a combination thereof. The precipitated sodium silicate and / or magnesium silicate can form an adsorbent coating or layer that has been precipitated in situ on the surface of the matrix mineral particles. In some examples, the silicate mineral particles can be coated with silica gel, for example, by combining the silicate mineral particles with water, sodium silicate, and an acid (such as H2SO4). The composite material thus formed can retain the adsorption properties of the silicate coating (such as for forming FFA salts) and the filtration performance of the matrix mineral particles.

[0050] In one example, the filter aid can include a silicate mineral coated with an alkali metal silicate, such as diatomaceous earth coated with sodium silicate or perlite coated with sodium silicate. In one example, the filter aid includes an alkali metal silicate and a silicate mineral, wherein at least a portion of the alkali metal silicate is present as a coating on the silicate mineral, and wherein the ratio of the alkali metal silicate to the silicate mineral in the filter aid is in the range of about 1:4 to 4:1 by weight.

[0051] In some instances, the alkali metal silicate may include, for example, sodium silicate, potassium silicate, or a mixture thereof. For example, the alkali metal silicate may include sodium metasilicate, such as sodium metasilicate pentahydrate, sodium metasilicate nonahydrate, anhydrous sodium metasilicate, or a mixture thereof. In some instances, the silicate minerals may include biogenic silica (e.g., diatomaceous earth), perlite, pumice, scoria, obsidian, rhyolite, volcanic ash, or a combination thereof.

[0052] In some instances, the ratio of the alkali metal silicate to the silicate mineral in the coating may range from about 1:4 to about 4:1, such as about 1:2 to about 1:4, about 3:4 to about 1:4, about 1:1 to about 1:4, about 1:1 to about 1:3, about 1:1 to about 1:2, or about 1:2 to about 2:1.

[0053] In one instance, coating may be accomplished using a rotary mixer, a pan granulator. In another instance, coating may be accomplished using a spray drying process. In some instances, the method for preparing the filter aid may include mixing an adsorbent with an alkali metal silicate and a silicate mineral. It is generally believed that the granulation method based on mixing is advantageous when the ratio of the alkali metal silicate to the silicate mineral in the coating is low, while spray drying is advantageous at a higher ratio.

[0054] In another instance, the filter aid may comprise a combination of an alkali metal silicate, a silicate mineral, and an adsorbent material. In this instance, the silicate mineral filter does not need to be chemically modified or functionally coated. When the alkali metal silicate and the silicate mineral are used together with the adsorbent, even if the adsorbent itself has a relatively low filtration efficiency, the resulting filter aid can still achieve a good balance among free fatty acid removal, soap removal, filtration rate, and cost.

[0055] In one instance, the adsorbent may be at least partially coated on the silicate mineral. In other instances, the adsorbent may be particulate material that is substantially not bound to the silicate mineral. In some instances, the adsorbent may include an alkaline earth metal silicate, such as magnesium silicate.

[0056] In some instances, the filter aid comprises about 10% - about 60% by weight of an alkali metal silicate, about 10% - about 60% by weight of a silicate mineral, and about 10% - about 60% by weight of an adsorbent. For example, the filter aid may comprise about 10% - about 50% by weight of an alkali metal silicate, such as about 20% - about 50%, about 30% - about 60%, or about 30% - about 50%. Again, for example, the filter aid may comprise about 10% - about 50% by weight of a silicate mineral, such as about 20% - about 50%, about 30% - about 60%, or about 30% - about 50%. In another instance, the filter aid may comprise about 10% - about 50% by weight of an adsorbent, such as about 10% - about 40%, about 20% - about 50%, or about 20% - about 40%.

[0057] In some exemplary methods of the present disclosure, silicate mineral particles can be mixed with water to form a suspension or slurry. A sodium silicate solution, a potassium silicate solution, and / or a magnesium sulfate solution (when the coating includes magnesium silicate) can be added to the suspension, and the mixture can be stirred or agitated to precipitate the silicate. The sodium silicate can include, for example, sodium orthosilicate (Na4SiO4), sodium metasilicate (Na2SiO3), and / or sodium disilicate (Na2Si2O5). The magnesium sulfate can be any magnesium sulfate that reacts with the sodium silicate to precipitate magnesium silicate. For example, the magnesium sulfate can be hydrated magnesium sulfate, which can be diluted to a desired molar concentration for precipitation before being combined with the sodium silicate solution.

[0058] According to some aspects of the present disclosure, the composite material can be treated with an acid before combining the material with an alkali metal silicate to form a filter aid. Without wishing to be bound by a particular theory, it is believed that the acid treatment reacts with the surface of the silicate coating to improve the adsorption and / or impurity removal performance of the composite material. According to some examples, the acid treatment can change the surface chemistry of the composite material. For example, the acid treatment can lower the surface pH of the silicate coating, which can promote the adsorption of impurities, such as metals, soaps, and FFAs, from non-aqueous liquids such as oils and oil mixtures.

[0059] For example, the composite material can be treated with at least one weak acid (such as citric acid, acetic acid, oxalic acid, malic acid, tartaric acid, ascorbic acid, or a mixture thereof). The acid treatment can be carried out by mixing the coated silicate mineral particles with the acid or with a mixture of the acid and water. According to some aspects, the acid treatment can include spraying the acid or the mixture of the acid and water onto the material. In some examples herein, the acid-treated composite material can then be dried, optionally at an elevated temperature, such as above about 70°C or at a temperature in the range of about 70°C to about 120°C, before combining the composite material with an alkali metal silicate (such as sodium metasilicate).

[0060] In some examples, the composite material is not treated with an acid before combining the material with an alkali metal silicate to form a filter aid.

[0061] According to some aspects of the present disclosure, the filter aid may comprise from about 0.5% to about 20% by weight of moisture, such as from about 5% to about 20%, from about 5% to about 15%, from about 10% to about 20%, from about 0.5% to about 10%, from about 2% to about 8%, from about 5% to about 10%, from about 1% to about 5%, from about 6% to about 9%, from about 2.5% to about 4.5% or from about 3% to about 5% by weight of water. For example, a method of preparing a filter aid may include preparing a material by at least partially coating a silicate mineral with an inorganic silica or silicate; combining the composite material with an alkali metal silicate; and adding from about 1% to about 10% by weight of water. Without wishing to be bound by theory, it is believed that adding moisture may improve the filtration performance of the filter aid, for example via forming an FFA salt with the alkali metal silicate and subsequently adsorbing the FFA salt onto the composite material.

[0062] The filter aids herein can be used to filter various non-aqueous liquids. For example, the liquid can be an oil or an oil mixture, such as including edible oils, such as oils derived from animal or plant materials that can be used for cooking. Suitable oils can include palm oil, palm kernel oil, butter, ghee, cocoa butter, cocoa butter substitutes, illipe fat, shea fat, canola oil, castor oil, coconut oil, coriander oil, corn oil, cottonseed oil, hazelnut oil, hempseed oil, linseed oil, mango kernel oil, olive oil, peanut oil, rapeseed oil, rice bran oil, safflower oil, soybean oil, sunflower oil, animal fats or oils (such as duck oil, lard, tallow, fish oil) and mixtures thereof. Before filtration, the oil may have been subjected to one or more refining steps, including degumming, bleaching, deodorizing and / or transesterification, such as by chemical or enzymatic treatment. In at least one instance, the oil is refined. Before filtration, the oil may have additionally undergone other processing steps, such as fractionation.

[0063] In some instances, the oil comprises one or more oils derived from palm. Oils derived from palm include palm oil, palm stearin, palm olein, palm kernel oil, palm kernel stearin and palm kernel olein and their transesterification products. In some instances, the vegetable oil comprises palm oil or a fraction thereof. Palm oil fractions include palm olein, palm stearin, palm mid-fraction and their transesterification products. The vegetable oil can include refined palm oil or a fraction thereof, such as palm olein or palm stearin.

[0064] According to some aspects of the present disclosure, the oil includes cooking oil, such as frying oil, which may include one or more of the exemplary oils and fats listed above. The oil can be filtered according to the present disclosure before and / or after being used for cooking (e.g., where the oil to be filtered includes used cooking oil). For example, the filter aids herein can be used to filter used cooking oil, e.g., to improve the quality of the oil for subsequent cooking (e.g., frying) processes. The oil to be filtered can contain FFA and / or other components that are generally considered to be contaminants to be removed.

[0065] According to some aspects of the present disclosure, the method can include passing a liquid through a filter aid as disclosed herein or otherwise bringing the liquid into contact with the filter aid. In some instances, the filter aid can be directly added to the liquid to be filtered, commonly referred to as the bulk feed. In an exemplary filtration process, an oil containing FFA can be combined with a composite filter aid as disclosed herein to form a mixture. The oil can contain at least 0.05% by weight of FFA, e.g., about 0.05% - about 10.0% by weight, about 0.1% - about 8.0% by weight, about 0.5% - about 5.0% by weight, about 1.0% - about 5.0% by weight, about 5.0% - about 10.0% by weight, about 7.0% - about 9.0% by weight, about 4.0% - about 6.0% by weight, about 1.0% - about 3.0% by weight, about 1.5% - about 2.5% by weight, about 0.05% - about 2.0% by weight, or about 0.1% - about 3.0% by weight of FFA. For example, the oil can contain about 0.5%, about 0.7%, about 1.0%, about 1.2%, about 1.4%, about 1.6%, about 1.8%, about 2.0%, about 2.2%, about 2.4%, or about 2.5% by weight of FFA.

[0066] Relative to the weight of the oil, the mixture of the oil and the filter aid can contain about 0.05% - about 10.0% by weight of the filter aid. In some instances, the filter aid can be combined with the oil in a dry form, such as a particulate filter aid. In other instances, the filter aid can be prepared as an aqueous suspension, e.g., the amount of the filter aid is in the range of about 1.0% - about 10.0% by weight relative to the total weight of the aqueous suspension.

[0067] The oil can be agitated, for example, to fully distribute the filter aid throughout the oil. In some instances, the oil (or oil / water mixture) can be heated or heated to a temperature in the range of, for example, about 50 °C to about 130 °C or about 60 °C to about 120 °C (such as a temperature of about 70 °C, about 80 °C, about 90 °C, about 100 °C, or about 110 °C). In some embodiments, the oil can be at a temperature of up to 120 °C - 160 °C. After a period of time sufficient to filter the liquid, the particles can be collected and removed from the liquid. For example, after forming the FFA salt and adsorbing the FFA salt onto the composite material, the material can be removed from the oil, thereby removing FFA from the oil. The material can be removed by any suitable technique (such as filtration, centrifugation, etc.).

[0068] In some cases, the filtration method can include pre - coating at least one filter element with a filter aid and contacting the liquid to be filtered with at least one filter element. The filter element can include a diaphragm (such as a screen, membrane, or pad), a cylindrical tube or a flake - like structure covered with a plastic or metal fabric woven fine enough. In certain cases, the filter element can include a porous structure with voids to allow materials of a certain size to pass through the filtration device. The filter aid can first be applied to the diaphragm of the filter element by a method called pre - coating. Pre - coating generally can include mixing a slurry of water and the filter aid and introducing the slurry into the liquid stream flowing through the diaphragm. During this process, a thin layer of the filter aid (such as about 1.5 mm - about 3.0 mm) can be deposited on the diaphragm, thereby forming the filtration device.

[0069] The filter aids herein may be capable of removing at least a portion or substantially all of the FFA of the oil. For example, the filter aids herein can be used to remove at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least 99% of the FFA of the oil. In some instances, the filter aid removes about 40% - about 99% of the FFA from the oil, such as removing about 50% - about 95%, about 60% - about 90%, about 75% - about 99%, about 80% - about 95%, or about 90% - about 99% of the FFA. Additionally or alternatively, the methods herein can remove at least 50% of the soap (such as the FFA salt produced from FFA) of the oil, such as removing at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least 99% of the soap. In some instances, the filter aid can remove about 75% - about 99%, about 80% - about 99%, about 90% - about 99%, or about 95% - about 99% of the soap (produced from FFA) from the oil. In some instances, the filter aid can remove substantially all of the soap (removing greater than 99% of the soap) from the oil.

[0070] On the one hand, an alkali metal carbonate or bicarbonate may be optionally added to the oil before or during filtration to provide enhanced removal of free fatty acids. On the one hand, an alkali metal carbonate or bicarbonate may be added and filtration may be carried out at an elevated temperature (such as above about 120 °C, above about 130 °C or above about 140 °C). On the one hand, the elevated temperature may be caused by the waste heat generated by the operating temperature of the frying oil, thereby reducing the need for cooling before the free fatty acid removal treatment. Therefore, a formulation having good performance at elevated temperatures may be more useful to the user.

[0071] Aspects of the present disclosure are further illustrated by reference to the following non-limiting numbered exemplary embodiments.

[0072] 1. A filter aid comprising: (a) an alkali metal silicate, and (b) a composite material comprising a silicate mineral at least partially coated with inorganic silica or a silicate.

[0073] 2. A filter aid comprising: (a) an alkali metal silicate, and (b) a silicate mineral, wherein at least a portion of the alkali metal silicate is present as a coating on the silicate mineral, and wherein the ratio of the alkali metal silicate to the silicate mineral in the filter aid is in the range of about 1:4 to 4:1 by weight.

[0074] 3. A filter aid comprising an alkali metal silicate, a silicate mineral and an adsorbent.

[0075] 4. The filter aid of paragraph 1, wherein the alkali metal silicate accounts for about 10 - about 70% by weight of the filter aid.

[0076] 5. The filter aid of paragraph 3, comprising about 10% - about 60% by weight of an alkali metal silicate, about 10% - about 60% by weight of a silicate mineral, and about 10 - about 60% by weight of an adsorbent.

[0077] 6. The filter aid of paragraph 3, wherein the adsorbent is at least partially coated on the silicate mineral.

[0078] 7. The filter aid of paragraph 3, wherein the adsorbent is a particulate material that does not substantially bind to the silicate mineral.

[0079] 8. The filter aid of any of the preceding paragraphs, wherein the alkali metal silicate comprises sodium silicate, potassium silicate or a mixture thereof.

[0080] 9. The filter aid of any of the preceding paragraphs, wherein the alkali metal silicate comprises sodium metasilicate.

[0081] 10. The filter aid of any of the preceding paragraphs, wherein the sodium metasilicate is sodium metasilicate pentahydrate, sodium metasilicate nonahydrate, anhydrous sodium metasilicate or a mixture thereof.

[0082] 11. The filter aid of any of the preceding paragraphs, wherein the alkali metal silicate includes sodium metasilicate pentahydrate.

[0083] 12. The filter aid of any of the preceding paragraphs, wherein the silicate mineral includes biogenic silica.

[0084] 13. The filter aid of any of the preceding paragraphs, wherein the silicate mineral includes diatomaceous earth.

[0085] 14. The filter aid of any of the preceding paragraphs, wherein the silicate mineral includes perlite, pumice, scoria, obsidian, pitchstone, volcanic ash, or a combination thereof.

[0086] 15. The filter aid of any of paragraphs 3-7, wherein the adsorbent is magnesium silicate.

[0087] 16. The filter aid of paragraph 1, wherein the inorganic silica or silicate includes silica gel, sodium silicate, magnesium silicate, or a combination thereof.

[0088] 17. The filter aid of paragraph 1, wherein the inorganic silica or silicate is precipitated on the surface of the silicate mineral.

[0089] 18. The filter aid of paragraph 1, wherein the composite material comprises about 50% to about 95% by weight of biogenic silica.

[0090] 19. The filter aid of paragraph 1, wherein the composite material comprises about 5% to about 80% by weight of inorganic silica or silicate relative to the total weight of the composite material.

[0091] 20. The filter aid of any of the preceding paragraphs, wherein the permeability of the filter aid is in the range of about 0.05 Darcy to about 3.0 Darcy.

[0092] 21. The filter aid of any of the preceding paragraphs, wherein the BET surface area of the filter aid is in the range of about 5 m 2 / g to about 450 m 2 / g.

[0093] 22. The filter aid of paragraph 1, wherein the d 50 diameter of the particle size distribution of the composite material is in the range of about 5 μm to about 300 μm.

[0094] 23. The filter aid of paragraph 1, wherein the median pore diameter (4V / A) of the composite material is in the range of about 0.1 μm to about 10.0 μm.

[0095] 24. The filter aid of paragraph 1, wherein the wet density of the composite material is in the range of about 5 lb / ft 3 to about 30 lb / ft 3 .

[0096] 25. A filter aid according to any one of the preceding paragraphs, wherein the filter aid contains about 0.5% to about 20% by weight of water, such as about 1% to about 10% by weight of water, relative to the total weight of the filter aid.

[0097] 26. A composition comprising a filter aid according to any one of the preceding paragraphs.

[0098] 27. The composition of paragraph 26, wherein the composition contains at least 80% by weight of the filter aid and about 1.0% to about 10.0% by weight of water relative to the total weight of the composition.

[0099] 28. The composition of paragraph 26 or 27, wherein the pH of the composition is in the range of about 9.0 to about 13.0.

[0100] 29. Use of a filter aid according to any one of paragraphs 1-25 or a composition according to any one of paragraphs 26-28 for filtering oil.

[0101] 30. A method of filtering oil, the method comprising combining the oil with a filter aid according to any one of paragraphs 1-25 to form a mixture.

[0102] 31. The method of paragraph 30, further comprising heating the mixture.

[0103] 32. The method of paragraph 30 or 31, wherein the oil contains about 0.05% to about 10.0% by weight of free fatty acids.

[0104] 33. The method of any one of paragraphs 30-31, further comprising separating at least a portion of the filter aid from the oil, wherein the filter aid removes at least 50%, at least 65% or at least 70% by weight of the free fatty acids from the oil.

[0105] 34. The method of any one of paragraphs 30-33, wherein the oil includes edible oil.

[0106] 35. The method of any one of paragraphs 30-34, wherein the mixture contains about 0.05% to about 10.0% by weight of the filter aid relative to the weight of the oil.

[0107] 36. A method of preparing a filter aid according to any one of paragraphs 1, 4, 8-14 and 16-25.

[0108] 37. The method of paragraph 36, wherein the method comprises preparing a composite material by at least partially coating a silicate mineral with inorganic silica or silicate; and combining the composite material with an alkali metal silicate.

[0109] 38. The method of paragraph 36 or 37, wherein the silicate mineral comprises diatomaceous earth, and preparing the composite material comprises precipitating inorganic silica or silicate on the surface of the diatomaceous earth.

[0110] 39. The method of any one of paragraphs 36 - 38, further comprising adding water to the filter aid such that the filter aid comprises from about 0.5% to about 10% by weight of water relative to the total weight of the filter aid.

[0111] The following examples are intended to illustrate the present disclosure and are not restrictive in nature. It should be understood that the present disclosure includes additional embodiments consistent with the foregoing description and the following examples. Examples

[0112] Example 1 Experiments were conducted to compare the performance of different filter aid compositions in filtering oil samples with a high FFA content. The oil sample used in each case was a commercially available vegetable oil for home cooking use (<0.1% wt. FFA), which was doped with 2% wt. oleic acid to simulate FFA contamination.

[0113] Four compositions outlined in Table 1 below were tested. Samples 1 and 2 were prepared as filter aids according to the present disclosure, which comprised sodium metasilicate pentahydrate and diatomaceous earth particles coated with magnesium silicate or diatomaceous earth particles coated with silica gel, having a particle size where more than 95% of the particles were less than 400 μm in size and more than 95% of the particles were greater than 5 μm in size. Sample 1 was prepared with 30% wt. Na2SiO3·5H2O and 70% wt. DE / MgO - SiO2 composite (comprising 60% wt. MgO - SiO2 (SiO2 / MgO molar ratio in the range of about 2.5 - about 3.2) coated on 40% wt. DE particles) (Imerys). Sample 2 was prepared with 30% wt. Na2SiO3·5H2O and 70% wt. DE / SiO2 composite (comprising 60% silica gel coated on 40% wt. DE particles) (Imerys). Two reference samples (Samples 3 and 4) were also prepared from 600R and PolySorb 30 / 40 (which are products commercially available from the Dallas Group). Sample 3 was (comprising 60% wt. Na2SiO3 and 40% wt. MgSiO3), and Sample 4 was 600R and a 50 / 50 mixture of PolySorb 30 / 40 (comprising 30% wt. Na2SiO3 and 70% wt. MgSiO3).

[0114] In each case, 150 g of oil was heated to 100 °C and 3 g of the dry composition sample (2% by weight of the oil) was added. The mixture was stirred at 100 °C for 60 minutes. The treated oil was then vacuum filtered through a heated Büchner funnel (100 ± 5 °C) using Whatman #4 filter paper. The time required to filter 150 g of the oil sample was recorded to an accuracy of ±1 minute.

[0115] Using phenolphthalein as an indicator, the FFA content of the filtered oil sample was titrated with NaOH in isopropanol (AOCS official method Aa 6-38). The percentage of FFA removal was calculated according to Equation 3 below: To determine the soap removal, using bromophenol blue as an indicator, the soap content of the filtered oil sample was titrated with HCl in acetone with 2% water (AOCS recommended practice Cc 17-95). The percentage of soap removal was calculated according to Equation 4 below: The theoretical amount of soap produced was calculated according to Equation 5 below: The results are shown in Table 1 below.

[0116] Table 1 When compared with commercially available products, Samples 1 and 2 were found to provide higher FFA removal rates, equivalent or higher soap (derived from FFA) removal rates, and faster filtration times.

[0117] Example 2 Using the same procedure as described in Example 1, additional filter aid compositions (Samples 5, 6, and 9-14) and reference compositions (7 and 8) were prepared and their filtration times, % FFA removal, and % soap removal were tested, as outlined in Table 2 below. For these studies, two different types of DE particles coated with synthetic magnesium silicate were used, which contained 60% wt. MgO-SiO2 (SiO2 / MgO molar ratio in the range of about 2.5 - about 3.2) coated on 40% wt. DE particles (Samples 5, 6, 9, and 11) (Imerys) or 40% wt. MgO-SiO2 (SiO2 / MgO molar ratio in the range of about 2.5 - about 3.2) coated on 60% wt. DE particles (Samples 10 and 13) (Imerys). Silica-coated DE particles were used for Samples 12 and 14 (Imerys). Anhydrous sodium silicate (molar ratio SiO2 / Na2O = 2.0) was obtained from PQ Corporation and Sodium silicate C20 (molar ratio SiO2 / Na2O = 2.0; 17.5% moisture). Water was added to Sample 6 to provide approximately 8% moisture by weight.

[0118] Table 2 §DE / SiO2 = 40% wt. silica gel coated on 60% wt. DE particles *DE / MgO - SiO2 = 60% wt. MgO - SiO2 coated on 40% wt. DE particles DE / MgO - SiO2 = 40% wt. MgO - SiO2 coated on 60% wt. DE particles Compared with Example 1, these studies showed that various alkali metal silicates other than sodium metasilicate successfully removed FFA from oil. Compositions containing sodium silicate with a higher SiO2 / Na2O molar ratio generally resulted in a lower FFA removal rate. Compared with silica gel - coated particles, compositions with silicate - coated diatomaceous earth particles also resulted in a higher FFA removal rate. Further, the results of Composition F showed that adding some additional water to the filter aid could result in better performance in FFA filtration.

[0119] Example 3 Samples of alkali metal silicate - coated silicate minerals were determined using the same general procedure as described in Example 1, except that the free fatty acid content in the oil used was approximately 0.82%. A filter aid sample containing sodium silicate - coated diatomaceous earth was prepared as follows: 1600 g of sodium silicate (Oxy Chemicals grade 50), 560 g of diatomaceous earth, and 384 g of deionized water were mixed. The resulting mixture was spray - dried in a laboratory - scale spray dryer with an inlet temperature set at 320 °C, an outlet temperature of 108 °C, and a pumped feed rate set at 21 rpm.

[0120] The resulting spray - dried material was considered sodium silicate - coated DE (NaSil - DE), with a NaSil:DE ratio of 1.5:1 (w / w), and the moisture content in the sodium silicate coating was approximately 15% (total moisture was approximately 10%, determined by weight loss on drying at 400 °C). Used in Samples 18 - 20 C20 silica gel was used as a control. In Sample 20, 50% C20 was mixed with 50% of high - purity grade silica gel, which had pore size, 230 - 400 mesh particle size, and 550 m 2 / g BET surface area (commercially available from Sigma - Aldrich).

[0121] Table 3 As shown in Table 3 above, when the composite material "NaSil-DE" is used alone (Sample 15), very good filtration time, FFA removal rate and satisfactory soap removal performance are obtained. The combination of 80% NaSil-DE and 20% DE / SiO2 composite material (Sample 17) allows excellent soap removal and is generally considered to achieve the best balance among the three performance factors. The combination of 80% NaSil-DE and 20% sodium metasilicate pentahydrate (Na2SiO3·5H2O) (Sample 16) allows almost complete FFA removal.

[0122] Example 4 Except that the free fatty acid content in the oil used was about 0.82%, the same general procedure as described in Example 1 was used, and the samples were measured as shown in Table 4 below to evaluate the effect of using the adsorbent magnesium silicate. The magnesium silicate (MgSil) used was precipitated magnesium silicate, commercially available from Shangyu Jiehua (particle size Dv = 60 μm, Dn = 9.3 μm, ~500 m 2 / g BET surface area).

[0123] Table 4 Based on the oil recovered before the filter became blocked.

[0124] The combination of sodium metasilicate and expanded ground perlite (Sample 23) obtained very good FFA removal and soap removal performance. However, the composite materials with magnesium silicate and mineral filter aids (Samples 21 and 22) obtained better FFA removal and soap removal performance. A mixture of 40% sodium metasilicate and 60% MgSil was tested and found to cause filter blockage, which may be due to the failure to effectively filter soap. Samples 21 - 23 completed filtration within 3 minutes, which is related to a good filtration rate in actual use.

[0125] Example 5 It was found that including sodium carbonate (e) or sodium bicarbonate (e) in the filter aid formulation had little effect on reducing FFA at low temperatures. Specifically, treating 150 g of vegetable oil containing 2% oleic acid with a 2% formulation (3 g) of a composite material containing 40% NaHCO3 + 60% (DE-SiO2) or 40% Na2CO3 + 60% (DE-SiO2) for 60 minutes resulted in a relative removal of approximately 10% of FFA (or an absolute reduction of 0.2% of FFA). However, when the temperature was raised to 146 °C (290 °F), the FFA reduction increased to 71% (or an absolute reduction of 0.85% of FFA).

[0126] Other aspects and embodiments of the present disclosure will be apparent to those skilled in the art upon consideration of the specification and practice of the embodiments disclosed herein.

[0127] It is intended that the specification and examples therein be considered only as exemplary, with the true scope and spirit of the present disclosure being indicated by the following claims.

Claims

1. A method for filtering oil, the method comprising combining the oil with a filter aid to form a mixture, wherein the filter aid comprises: an alkali metal silicate including sodium metasilicate pentahydrate, sodium metasilicate nonahydrate or a mixture thereof; a silicate mineral selected from ground expanded perlite or thermally alkali-treated diatomaceous earth; and an adsorbent selected from magnesium silicate; and wherein the method further comprises separating at least a portion of the filter aid from the oil, wherein the filter aid removes at least 70% by weight of free fatty acids from the oil.

2. The method of claim 1, wherein the alkali metal silicate comprises sodium metasilicate pentahydrate.

3. The method of claim 1, wherein the alkali metal silicate accounts for 10 - 70% by weight of the filter aid.

4. The method of claim 1, wherein the magnesium silicate is precipitated on the surface of the silicate mineral.

5. The method of claim 1, wherein the permeability of the filter aid is in the range of 0.05 Darcy - 3.0 Darcy.

6. The method of claim 1, wherein the BET surface area of the filter aid is in the range of 5 m 2 / g - 450 m 2 / g.

7. The method of claim 1, wherein the d of the particle size distribution of the composite material 50 has a diameter in the range of 5 μm to 300 μm.

8. The method of claim 1, further comprising heating the mixture.

9. The method of claim 1, wherein the oil contains 0.05% - 10.0% by weight of free fatty acids.

10. The method of claim 1, wherein the oil includes edible oil.

11. The method of any one of claims 1 - 10, wherein the mixture comprises 0.05% - 10.0% of the filter aid relative to the weight of the oil.

12. The method of claim 1, further comprising adding water to the filter aid such that the filter aid comprises 0.5% - 10% by weight of water relative to the total weight of the filter aid.

13. Use of the filter aid defined in claim 1 for filtering oil.

Images