Adsorbent

Abstract

The present invention addresses the problem of providing a novel adsorbent that has a high adsorption capacity and that is capable of adsorbing a substance to be adsorbed with a small amount of use.　The present disclosure provides an adsorbent composed of an amorphous magnesium silicate compound. The magnesium silicate compound according to the present disclosure has an alkali metal content of 1.20 mass% or less. The magnesium silicate compound according to the present disclosure has a solid acid content of 0.70 mmol / g or more.

Description

Adsorbent

[0001] The present invention relates to a novel adsorbent used for adsorbing adsorbates such as alkali metals.

[0002] Chemical products may contain trace amounts of impurities, such as catalysts used in synthesis, unreacted raw materials, and by-products from reactions. From the perspective of improving product quality, it is desirable to efficiently remove these impurities. Examples of methods for removing such impurities include those used in the production process of chemical products, such as neutralization, distillation, extraction, and adsorption. Among these, adsorption methods, particularly those using adsorbents, are commonly used as simple methods.

[0003] For example, polyurethane foams are produced by polymerizing raw materials, namely, polyol and isocyanate components. Polyols used in the production of polyurethane foams include polyether polyols, polymer polyols, and polyester polyols, and are used in any combination depending on the desired polyurethane performance. For example, polyether polyols are produced by addition polymerization of propylene oxide to glycerin in the presence of an alkali metal-containing basic catalyst, and require a purity as close to zero as possible to residual catalyst after purification.

[0004] In order to achieve such high level of purity, in the production of polyether polyol, adsorbents that can adsorb and remove alkali metal-containing basic catalysts are used.The adsorbents used here are usually synthetic products such as molecular sieves, activated alumina, synthetic magnesium silicate, synthetic aluminum silicate, activated carbon, natural products, processed natural products such as acid clay, activated clay, etc., but are not particularly limited.For example, Patent Document 1 discloses an adsorbent that can adsorb and remove alkali metal-containing basic catalysts, which is made of amorphous synthetic hydrous magnesium silicate compound, and its chemical formula, BET specific surface area, alkali metal content and average particle size are each within a specific range.

[0005] Japanese Patent Application Laid-Open No. 2004-75674

[0006] However, these conventional adsorbents require a large amount of adsorbent relative to the amount of alkali metal-containing basic catalyst to be adsorbed, which leads to problems such as a decrease in yield due to the adsorption of polyether polyol by the adsorbent and a large amount of waste generated after purification. To solve these problems, there is a strong demand for improving the adsorption capacity of the adsorbent and reducing the amount of adsorbent used.

[0007] Therefore, an object of the present invention is to provide a novel adsorbent that has a high adsorption capacity and is capable of adsorbing an adsorbate with a small amount of use.

[0008] As a result of extensive research conducted by the present inventors to achieve the above object, it has been found that by using an amorphous magnesium silicate compound having a low alkali metal content and high solid acidity as an adsorbent, it is possible to obtain a K ＋ , Na ＋ , Ni ＋ The present disclosure has been completed based on this finding and includes the following aspects.

[0009] (First Disclosure) The first disclosure relates to an adsorbent comprising an amorphous magnesium silicate compound. The magnesium silicate compound has an alkali metal content of 1.20 mass% or less. The magnesium silicate compound has a solid acidity of 0.70 mmol / g or more.

[0010] (Second Disclosure) In the second disclosure, in the first disclosure, the magnesium silicate compound is a compound represented by the following formula (1): (MgO) ｘ SiO ２ ・mH ２ O (1) [In formula (1), x is a number that satisfies 0.1≦x≦0.5, and m is a number that satisfies 0.1≦m≦1.5.]

[0011] (Third Disclosure) The present third disclosure is the first or second disclosure, wherein the magnesium silicate compound has a BET specific surface area of ​​200 m ２ / g to 1000m ２ / g.

[0012] (Fourth Disclosure) The present fourth disclosure relates to any one of the first to third disclosures, wherein the total pore volume of the magnesium silicate compound is 0.40 cm ３ / g ~ 1.50 cm ３ / g.

[0013] (Fifth Disclosure) The fifth disclosure relates to a method for reducing the alkali metal content in a polyether polyol, the method comprising contacting a polyether polyol containing an alkali metal-containing basic catalyst with the adsorbent according to any one of the first to fourth disclosures.

[0014] According to the present invention, it is possible to provide a novel adsorbent which has a high adsorption capacity and can adsorb an adsorbate with a small amount used.

[0015] Fig. 1 is a powder X-ray diffraction pattern of the magnesium silicate compound of Example 2. Fig. 2 is a powder X-ray diffraction pattern of the magnesium silicate compound of Example 4.

[0016] Preferred embodiments of the adsorbent of the present invention will be described in detail below. In this specification, various numerical ranges mean ranges including the upper and lower limits unless otherwise specified.

[0017] [Adsorbent] An adsorbent according to one embodiment of the present invention comprises an amorphous magnesium silicate compound. This magnesium silicate compound has an alkali metal content of 1.20 mass% or less. Furthermore, this magnesium silicate compound has a solid acidity of 0.70 mmol / g or more.

[0018] The adsorbent of the present embodiment is made of the amorphous magnesium silicate compound having a low alkali metal content and a high solid acidity as described above, and therefore, ＋ , Na ＋ , Ni ＋The adsorbent of this embodiment can exhibit excellent adsorption capacity for metal ions such as magnesium silicate compounds. Furthermore, since its adsorption capacity is much higher than that of adsorbents made of conventional magnesium silicate compounds, the amount of the adsorbent used can be significantly reduced compared to such conventional adsorbents. In other words, the adsorbent of this embodiment is a novel adsorbent that has a much higher adsorption capacity than adsorbents made of conventional magnesium silicate compounds and can adsorb adsorbates with a small amount used. Furthermore, the adsorbent of this embodiment can contribute to reducing energy consumption and waste disposal, and has the advantage of being able to contribute to the achievement of the SDGs (Sustainable Development Goals) adopted at the United Nations Summit.

[0019] (Magnesium silicate compound) As described above, the adsorbent according to one embodiment of the present invention comprises an amorphous magnesium silicate compound. Here, the term "amorphous magnesium silicate compound" refers to a magnesium silicate compound whose powder X-ray diffraction pattern shows an amorphous structure.

[0020] (Alkali Metal Content) In this embodiment, the alkali metal content of the magnesium silicate compound is 1.20 mass % or less.

[0021] Such an alkali metal content of less than a specific amount can be obtained, for example, by adjusting the pH of the reaction slurry to be low during the synthesis of the magnesium silicate compound described below, or by performing a heat aging treatment and / or an acid treatment after synthesis. For example, the alkali metal content can be reduced by lowering the pH of the reaction slurry during the synthesis of the magnesium silicate compound. Furthermore, performing a heat aging treatment after the synthesis of the magnesium silicate compound is thought to promote the dissolution and precipitation of the magnesium silicate compound, thereby reducing the alkali metal content. Furthermore, performing an acid treatment after the synthesis of the magnesium silicate compound replaces the contained alkali metal components with acid protons, thereby reducing the alkali metal content.

[0022] In this specification, the alkali metal component refers to alkali metals such as sodium and potassium derived from the raw materials.

[0023] The alkali metal content of the magnesium silicate compound is preferably 1.10% by mass or less, more preferably 1.00% by mass or less. The lower limit of the alkali metal content of the magnesium silicate compound is not particularly limited, but may be, for example, 0.001% by mass.

[0024] (Solid Acidity) In one embodiment of the present invention, the magnesium silicate compound has a solid acidity of 0.70 mmol / g or more.

[0025] Such a solid acid content of at least a specific amount can be obtained by the same means as the alkali metal content described above. That is, such a solid acid content of at least a specific amount can be obtained, for example, by adjusting the pH of the reaction slurry to be low during the synthesis of the magnesium silicate compound described below, or by performing a heat aging treatment and / or an acid treatment after synthesis. For example, by lowering the pH of the reaction slurry during the synthesis of the magnesium silicate compound, the alkali metal content can be reduced and the solid acid content can be increased. Furthermore, performing a heat aging treatment after the synthesis of the magnesium silicate compound is thought to promote the dissolution and precipitation of the magnesium silicate compound, thereby reducing the alkali metal content and increasing the solid acid content. Furthermore, performing an acid treatment after the synthesis of the magnesium silicate compound replaces the contained alkali metal component with acid protons, thereby reducing the alkali metal content and increasing the solid acid content.

[0026] The solid acidity of the magnesium silicate compound is preferably 1.00 mmol / g or more, more preferably 1.50 mmol / g or more. The upper limit of the solid acidity of the magnesium silicate compound is not particularly limited, but may be, for example, 10.00 mmol / g.

[0027] A specific method for measuring the solid acidity will be explained in the examples below.

[0028] As described above, the magnesium silicate compound according to one embodiment of the present invention has an alkali metal content equal to or less than the specific amount and a high solid acidity equal to or greater than the specific amount, and thus exhibits excellent adsorption capacity for various metal ions. As a result, the adsorbent according to this embodiment can adsorb various metal ions in smaller amounts than adsorbents made of conventional magnesium silicate compounds.

[0029] In this embodiment, the magnesium silicate compound is not particularly limited except that it is amorphous, has an alkali metal content equal to or less than the specific amount, and has a high solid acidity equal to or greater than the specific amount, but is preferably a hydrous magnesium silicate compound represented by the following formula (1): (MgO) ｘ SiO ２ ・mH ２ O (1) [In formula (1), x is a number that satisfies 0.1≦x≦0.5, and m is a number that satisfies 0.1≦m≦1.5.]

[0030] When the magnesium silicate compound is a hydrous magnesium silicate compound represented by formula (1), it can more reliably exhibit the excellent adsorption ability for the above-mentioned metal ions.

[0031] In the above formula (1), the preferred range of x is 0.2≦x≦0.35.

[0032] (BET specific surface area) In this embodiment, the BET specific surface area of ​​the magnesium silicate compound is 200 m ２ / g to 1000m ２ When the BET specific surface area of ​​the magnesium silicate compound is within this range, a certain amount or more of adsorption can be ensured, and therefore the excellent adsorption ability for the above-mentioned metal ions can be more reliably exhibited.

[0033] The BET specific surface area of ​​the magnesium silicate compound is 220 m ２ / g or more is more preferable, and 250m ２ The BET specific surface area of ​​the magnesium silicate compound is more preferably 900 m / g or more.２ / g or less is more preferable, and ２ It is more preferable that the tensile strength is 1 / g or less.

[0034] In this specification, the BET specific surface area means the specific surface area of ​​a magnesium silicate compound measured by the BET method. A specific method for measuring the BET specific surface area will be described in the Examples below.

[0035] (Total pore volume) In this embodiment, the total pore volume of the magnesium silicate compound is 0.40 cm ３ / g ~ 1.50 cm ３ When the total pore volume of the magnesium silicate compound is within this range, a certain amount or more of adsorption can be ensured, and therefore the excellent adsorption ability for the above-mentioned metal ions can be more reliably exhibited.

[0036] The total pore volume of the magnesium silicate compound is 0.50 cm ３ / g or more. The total pore volume of the magnesium silicate compound is more preferably 1.20 cm ３ It is more preferable that the SiO2 content is 1 / g or less.

[0037] The specific method for measuring the total pore volume will be explained in the examples below.

[0038] (Average particle size) In this embodiment, the average particle size of the magnesium silicate compound is preferably 2.0 μm to 60.0 μm. When the average particle size of the magnesium silicate compound is within this range, the specific surface area can be increased and a certain amount of adsorption can be secured, thereby more reliably exhibiting the excellent adsorption ability for the above-mentioned metal ions.

[0039] The average particle size of the magnesium silicate compound is more preferably 5.0 μm or more, and more preferably 50.0 μm or less.

[0040] The specific method for measuring the average particle size will be explained in the examples below.

[0041] [Production Method] A method for producing the magnesium silicate compound constituting the adsorbent according to one embodiment of the present invention will be described below using the above-mentioned method for producing the hydrous magnesium silicate compound as an example. Note that the magnesium silicate compound that can be used as the adsorbent of the present invention is amorphous, has an alkali metal content not greater than the above-mentioned specific amount, and has a high solid acidity not less than the above-mentioned specific amount, so long as it is not particularly limited in terms of its production method, conditions, etc.

[0042] (Synthesis Step) The above-mentioned hydrous magnesium silicate compound can be synthesized by reacting a water-soluble magnesium compound with a water-soluble silicic acid compound. Examples of the water-soluble magnesium compound include magnesium chloride, magnesium sulfate, magnesium nitrate, etc. Examples of the water-soluble silicic acid compound include, for example, magnesium chloride, magnesium sulfate, magnesium nitrate, etc., which is commonly known as water glass and has the general formula Na ２ O.nSiO ２ Examples of the water-soluble silicate include sodium silicate represented by the formula (n = 2 to 4), sodium metasilicate, sodium orthosilicate, and alkali silicate salts such as potassium silicate. Of these, it is preferable to use No. 3 water glass as the water-soluble silicate compound.

[0043] The reaction may be a batch reaction in which a fixed amount of an aqueous solution of a magnesium compound and a fixed amount of an aqueous solution of a silicic acid compound are simultaneously poured into a reaction vessel, or a continuous reaction in which a fixed amount of an aqueous solution of a magnesium compound and a fixed amount of an aqueous solution of a silicic acid compound are continuously poured into a reaction vessel to continuously obtain a reaction slurry. A continuous reaction is advantageous in terms of production efficiency.

[0044] The reaction temperature is not particularly limited, and may be, for example, a temperature of 15° C. to 60° C. For example, the reaction may be carried out by placing the reaction vessel in a thermostatic bath controlled at a constant temperature, or a container containing an aqueous magnesium compound solution and a container containing an aqueous silicic acid compound solution may be placed in a thermostatic bath controlled at a constant temperature, and the aqueous solutions may be poured from each container into the reaction vessel using a metering pump.

[0045] The reaction pH is, for example, 7 to 10, and preferably 8.5 to 9.5. By adjusting the reaction pH within this range, the primary particles of the synthesized hydrous magnesium silicate compound can be converted into fine particles. By converting the primary particles into fine particles, the specific surface area of ​​the hydrous magnesium silicate compound increases, increasing the number of adsorption sites and improving the adsorption capacity.

[0046] (Heat Aging Step) The reaction slurry obtained by the synthesis step may be aged by heating and stirring. The aging temperature is, for example, 60°C to 120°C, preferably 70°C to 110°C, and more preferably 80°C to 100°C. The aging time is, for example, 0.5 hours to 18 hours, preferably 1 hour to 12 hours, and more preferably 2 hours to 6 hours. By heat-aging the synthesized hydrous magnesium silicate compound under such specific conditions, the specific surface area of ​​the hydrous magnesium silicate compound increases, increasing the number of adsorption sites and improving the adsorption capacity.

[0047] (Acid Treatment Step) The synthesized hydrous magnesium silicate compound may be acid-treated using an inorganic acid. By performing such acid treatment, the alkali metal component in the synthesized hydrous magnesium silicate compound is substituted with a proton of the inorganic acid, thereby increasing the solid acidity of the hydrous magnesium silicate compound, thereby improving the adsorption capacity of alkali metal ions. The alkali metal component is, for example, sodium or potassium derived from the raw material.

[0048] The inorganic acid that can be used in the acid treatment step is not particularly limited, but examples thereof include sulfuric acid, hydrochloric acid, and nitric acid.

[0049] A specific method for the acid treatment step, i.e., a specific method for substituting the alkali metal component in the synthesized hydrous magnesium silicate compound with the proton of an inorganic acid, includes, for example, a method of separating the reaction slurry into solid and liquid, washing the solid with diluted inorganic acid, and then washing with water.Another method includes a method of separating the reaction slurry into solid and liquid, suspending the solid in diluted inorganic acid and stirring for a certain period of time, dehydrating, and then washing with water.

[0050] The concentration of the inorganic acid is, for example, 0.01 mol / L to 0.5 mol / L, preferably 0.02 mol / L to 0.2 mol / L. When the concentration of the diluted inorganic acid is 0.01 mol / L or higher, the protons in the inorganic acid are sufficiently substituted with alkali metal components. On the other hand, when the concentration of the diluted inorganic acid is 0.5 mol / L or lower, sulfate ions, chloride ions, nitrate ions, and the like of the inorganic acid are less likely to remain as impurities in the solid. Furthermore, when the concentration of the diluted inorganic acid is 0.5 mol / L or lower, the magnesium in the magnesium silicate is less likely to be dissolved by the inorganic acid.

[0051] (Drying Step) The method for drying the hydrous magnesium silicate compound after synthesis is not particularly limited, but examples include a tray drying method in which the dehydrated solid is placed in a stainless steel tray and dried with hot air. Other drying methods include a spray drying method in which the dehydrated solid is slurried to a concentration of 100 g / L to 500 g / L in terms of solid content, and optionally processed in a wet mill such as a ball mill, colloid mill, SC mill, or Dyno Mill to shape the dried product, followed by drying in a spray dryer. Spray drying is preferably used as the drying method because it makes it easy to granulate the hydrous magnesium silicate compound into spherical particles. Granulating the hydrous magnesium silicate compound into spherical particles has the advantage of making it easier to separate and remove after the adsorption treatment.

[0052] The magnesium silicate compound obtained by the above-described production method is amorphous and has an alkali metal content equal to or less than the above-described specific amount and a high solid acidity equal to or more than the above-described specific amount due to the reaction conditions during synthesis and the heat-aging step and / or acid treatment step after synthesis.

[0053] Such magnesium silicate compounds can be used, for example, as adsorbents for various industrial applications, but as described above, they are particularly useful as adsorbents for adsorbing and removing alkali metal-containing basic catalysts when producing polyether polyols.

[0054] [Method for Reducing Alkali Metal Content in Polyether Polyol] Another embodiment of the present invention is a method for reducing the alkali metal content in a polyether polyol, which comprises contacting a polyether polyol containing an alkali metal-containing basic catalyst with an adsorbent comprising an amorphous magnesium silicate compound having an alkali metal content not greater than the specified amount and a high solid acidity not less than the specified amount.

[0055] As described above, this reduction method has an extremely excellent adsorption capacity that allows the adsorbent to adsorb various metal ions even with a small amount of use, so it can increase the yield of polyether polyol and further reduce the amount of waste generated after purification.

[0056] A specific method for adsorbing and removing the residual alkali metal-containing basic catalyst contained in the polyether polyol includes, for example, adding the magnesium silicate compound as an adsorbent to the polyether polyol, mixing the resulting mixture, and then separating and removing the adsorbent.

[0057] The amount of adsorbent added depends on the amount of the remaining alkali metal-containing basic catalyst, but is, for example, 0.1 to 10.0% by mass, preferably 0.5 to 5.0% by mass, based on the mass of the polyether polyol.

[0058] The adsorption treatment can be carried out under stirring at a temperature of 70°C to 150°C for a treatment time of 5 to 120 minutes. Water may be added during the adsorption treatment. In this case, it is preferable to add 0.5% by mass to 3.0% by mass of water relative to the mass of the polyether polyol. Before the adsorption treatment, an antioxidant may be added to the polyether polyol to prevent deterioration.

[0059] Furthermore, before adding the adsorbent to the polyether polyol, at least one of inorganic acids such as phosphoric acid, sulfuric acid, sodium hydrogen pyrophosphate, and oxalic acid, inorganic acid salts, and organic acids may be added to cause a neutralization reaction. In this case, the adsorbent is added after the neutralization reaction is completed.

[0060] The present invention is not limited to the above-described embodiments or the examples to be described later, and appropriate combinations, substitutions, modifications, etc. are possible within the scope that does not deviate from the purpose and intent of the present invention.

[0061] EXAMPLES The present invention will be explained in more detail below by way of examples and comparative examples, but the present invention is not limited to these examples.

[0062] The methods for measuring various physical properties and the like in the examples and comparative examples are as follows.

[0063] <SiO ２ / MgO molar ratio and alkali metal content> SiO of magnesium silicate compound ２ The / MgO molar ratio and the alkali metal content were measured using a scanning X-ray fluorescence analyzer "ZSX Primus IV" manufactured by Rigaku Corporation.

[0064] <BET specific surface area and total pore volume> The BET specific surface area and total pore volume of the magnesium silicate compound were measured using a high-precision specific surface area / pore distribution measuring device "BELsorp-max" manufactured by Microtrac BEL Corporation.

[0065] <Liquid pH> The liquid pH of the magnesium silicate compound was measured as follows. 2.0 g of a dried magnesium silicate compound and 40 mL of ion-exchanged water were placed in a beaker and stirred with a magnetic stirrer for 5 minutes. The mixture was then filtered using No. 5C filter paper, and the pH of the filtrate was measured. The pH of this filtrate was taken as the liquid pH of the magnesium silicate compound.

[0066] <Solid Acidity> 0.1 g of dried magnesium silicate compound was placed in a stoppered Erlenmeyer flask and 5 mL of benzene (Wako Reagents Special Grade) was added. 1 mL of a 0.1 wt % benzene solution of methyl orange was added as an indicator with a pKa of 4.8, causing the dried particles to turn red. The dried particles were titrated with a 0.1 mol / L n-butylamine-benzene solution until they turned yellow, and the amount of n-butylamine-benzene solution required for the titration was designated A (mL). After the Erlenmeyer flask was stopped and left to stand for 24 hours, the dried particles returned to red. They were then titrated again with a 0.1 mol / L n-butylamine-benzene solution until they turned yellow, and the amount of n-butylamine-benzene solution required for the titration was designated B (mL). This procedure was repeated once more, and the amount of n-butylamine-benzene solution required for the titration was designated C (mL). The solid acidity was calculated from the total amount of the three titrations using the following formula: Solid acid amount (mmol / g) = 0.1 (A+B+C) / 0.1g

[0067] <Average Particle Size> The average particle size of the magnesium silicate compound was measured using a particle size distribution analyzer "MICROTRAC MT3000II Series" manufactured by Nikkiso Co., Ltd. Specifically, 70 mL of a 2.0 g / L aqueous solution of sodium hexametaphosphate was added to 0.7 g of dried magnesium silicate compound, and the mixture was stirred with a magnetic stirrer. 2 to 4 mL of the resulting dispersion was added to a 2.0 g / L aqueous solution of sodium hexametaphosphate, and the dispersion was circulated for 1 minute. The particle size distribution was then measured using the particle size distribution analyzer. The average particle size was determined from the resulting 50% cumulative (median diameter).

[0068] Next, examples of the present invention and comparative examples will be described.

[0069] Example 1 (Synthesis test) A 1.17 mol / L aqueous solution of magnesium sulfate and a 0.46 mol / L aqueous solution of Na ２ O and 1.44 mol / L SiO ２A constant amount of a No. 3 water glass aqueous solution consisting of the above was continuously poured into a continuous reaction vessel to cause a coprecipitation reaction. The reaction temperature was 40°C. The pH of the resulting reaction slurry was 8.9. The average particle size of the reaction product particles was 8.2 μm. The reaction slurry was then dehydrated by suction filtration using a Nutsche filter, and the resulting solid was washed with ion-exchanged water in an amount 20 times the weight of the solid. The resulting solid was slurried to a concentration of 250 g / L and spray-dried using a spray dryer.

[0070] The dried magnesium silicate compound of Example 1 thus obtained was subjected to measurement of various physical properties. ２ The alkali metal content of the magnesium silicate compound of Example 1 was 1.00 mass %. The BET specific surface area of ​​the magnesium silicate compound of Example 1 was 295 m ２ The total pore volume of the magnesium silicate compound of Example 1 was 0.47 cm ３ / g. Furthermore, the liquid pH of the magnesium silicate compound of Example 1 was 9.8. The solid acid amount of the magnesium silicate compound of Example 1 was 0.73 mmol / g. The average particle size of the magnesium silicate compound of Example 1 was 42.2 μm. Furthermore, the powder X-ray diffraction pattern of the magnesium silicate compound of Example 1 showed that it was amorphous.

[0071] (Adsorption Test 1) 160 g of polypropylene glycol (degree of polymerization: 3,000) in which potassium hydroxide had been dissolved to a potassium concentration of 1,400 ppm was placed in a four-neck round-bottom flask and heated and stirred with a mantle heater while purging with nitrogen. When the liquid temperature reached 85°C, 1.6 mL of ion-exchanged water was added. After that, when the liquid temperature reached 90°C, 0.4 g of an adsorbent composed of a synthesized magnesium silicate compound was added, and the mixture was heated and stirred for 30 minutes. After 30 minutes, the treated liquid was immediately suction-filtered at a suction pressure of 0.02 MPa to obtain a filtrate. The filtrate was subjected to potentiometric titration with 0.01 N hydrochloric acid to determine the potassium concentration in the filtrate, which was 209 ppm.

[0072] (Adsorption Test 2) 160 g of polypropylene glycol (degree of polymerization: 3,000) in which potassium hydroxide had been dissolved to a potassium concentration of 1,400 ppm was placed in a four-neck round-bottom flask and heated and stirred with a mantle heater while purging with nitrogen. When the liquid temperature reached 85°C, 1.6 mL of ion-exchanged water was added. After that, when the liquid temperature reached 90°C, 0.56 g of an adsorbent composed of a synthesized magnesium silicate compound was added, and the mixture was heated and stirred for 30 minutes. After 30 minutes, the treated liquid was immediately suction-filtered at a suction pressure of 0.02 MPa to obtain a filtrate. The filtrate was subjected to potentiometric titration with 0.01 N hydrochloric acid to determine the potassium concentration in the filtrate, which was 128 ppm.

[0073] (Adsorption Test 3) 160 g of polypropylene glycol (degree of polymerization: 3,000) in which potassium hydroxide had been dissolved to a potassium concentration of 1,400 ppm was placed in a four-neck round-bottom flask and heated and stirred with a mantle heater while purging with nitrogen. When the liquid temperature reached 85°C, 1.6 mL of ion-exchanged water was added. After that, when the liquid temperature reached 90°C, 0.8 g of an adsorbent composed of a synthesized magnesium silicate compound was added, and the mixture was heated and stirred for 30 minutes. After 30 minutes, the treated liquid was immediately suction-filtered at a suction pressure of 0.02 MPa to obtain a filtrate. The filtrate was subjected to potentiometric titration with 0.01 N hydrochloric acid to determine the potassium concentration in the filtrate, which was 38 ppm.

[0074] Example 2 (Synthesis test) A 1.17 mol / L aqueous solution of magnesium sulfate and a 0.46 mol / L aqueous solution of Na ２ O and 1.44 mol / L SiO ２ A constant amount of a No. 3 water glass aqueous solution consisting of the above was continuously poured into a continuous reactor and subjected to a coprecipitation reaction. The reaction temperature was 40°C. The pH of the resulting reaction slurry was 8.9. The average particle size of the reaction product particles was 8.2 μm. The reaction slurry was then dehydrated by suction filtration using a Nutsche filter, and the resulting solid was washed with 0.05 mol / L sulfuric acid in an amount 15 times the weight of the solid to ion-exchange the sodium in the solid, followed by similar washing with 20 times the amount of ion-exchanged water. The resulting solid was slurried to a concentration of 250 g / L and spray-dried using a spray dryer.

[0075] The dried magnesium silicate compound of Example 2 thus obtained was subjected to measurement of various physical properties. ２ The alkali metal content of the magnesium silicate compound of Example 2 was 0.17% by mass. The BET specific surface area of ​​the magnesium silicate compound of Example 2 was 259 m ２ The total pore volume of the magnesium silicate compound of Example 2 was 0.56 cm ３ / g. Furthermore, the liquid pH of the magnesium silicate compound of Example 2 was 9.1. The solid acid amount of the magnesium silicate compound of Example 2 was 0.90 mmol / g. The average particle size of the magnesium silicate compound of Example 2 was 43.8 μm. Furthermore, the powder X-ray diffraction pattern of the magnesium silicate compound of Example 2 showed that it was amorphous, as shown in FIG. 1.

[0076] (Adsorption Test 1) An adsorption test was carried out in exactly the same manner as Adsorption Test 1 in Example 1, and the potassium concentration in the filtrate was found to be 211 ppm.

[0077] (Adsorption Test 2) An adsorption test was carried out in exactly the same manner as Adsorption Test 2 in Example 1, and the potassium concentration in the filtrate was 104 ppm.

[0078] (Adsorption Test 3) An adsorption test was carried out in exactly the same manner as Adsorption Test 3 in Example 1, and the potassium concentration in the filtrate was 34 ppm.

[0079] Example 3 (Synthesis test) A 1.17 mol / L aqueous solution of magnesium sulfate and a 0.46 mol / L aqueous solution of Na ２ O and 1.44 mol / L SiO ２A constant amount of a No. 3 water glass aqueous solution consisting of the above was continuously poured into a continuous reaction vessel to cause a coprecipitation reaction. The reaction temperature was 40°C. The pH of the resulting reaction slurry was 8.9. The average particle size of the reaction product particles was 8.2 μm. The reaction slurry was then heated and stirred at 90°C for 2 hours. The slurry was then dehydrated by suction filtration using a Nutsche filter, and the resulting solid was washed with ion-exchanged water in an amount 20 times the weight of the solid. The resulting solid was slurried to a concentration of 250 g / L and spray-dried using a spray dryer.

[0080] The dried magnesium silicate compound of Example 3 thus obtained was subjected to various physical properties measurements. ２ The alkali metal content of the magnesium silicate compound of Example 3 was 0.98 mass %. The BET specific surface area of ​​the magnesium silicate compound of Example 3 was 714 m ２ The total pore volume of the magnesium silicate compound of Example 3 was 1.05 cm ３ / g. Furthermore, the liquid pH of the magnesium silicate compound of Example 3 was 9.6. The solid acid amount of the magnesium silicate compound of Example 3 was 1.65 mmol / g. The average particle size of the magnesium silicate compound of Example 3 was 39.8 μm. Furthermore, the powder X-ray diffraction pattern of the magnesium silicate compound of Example 3 showed that it was amorphous.

[0081] (Adsorption Test 1) An adsorption test was carried out in exactly the same manner as Adsorption Test 1 in Example 1, and the potassium concentration in the filtrate was 123 ppm.

[0082] (Adsorption Test 2) An adsorption test was carried out in exactly the same manner as Adsorption Test 2 in Example 1, and the potassium concentration in the filtrate was found to be 70 ppm.

[0083] (Adsorption Test 3) An adsorption test was carried out in exactly the same manner as Adsorption Test 3 in Example 1, and the potassium concentration in the filtrate was 40 ppm.

[0084] Example 4 (Synthesis test) A 1.17 mol / L magnesium sulfate aqueous solution and a 0.46 mol / L Na ２O and 1.44 mol / L SiO ２ A constant amount of a No. 3 water glass aqueous solution consisting of the above was continuously poured into a continuous reactor and subjected to a coprecipitation reaction. The reaction temperature was 40°C. The pH of the resulting reaction slurry was 8.9. The average particle size of the reaction product particles was 8.2 μm. The reaction slurry was then heated and stirred at 90°C for 2 hours. The slurry was then dehydrated by suction filtration using a Nutsche filter. The solid matter was washed with 0.05 mol / L sulfuric acid in an amount 15 times the weight of the solid matter to ion-exchange the sodium in the solid matter, and then similarly washed with 20 times the amount of ion-exchanged water. The resulting solid matter was slurried to a concentration of 250 g / L and spray-dried using a spray dryer.

[0085] The dried magnesium silicate compound of Example 4 thus obtained was subjected to various physical properties measurements. ２ The alkali metal content of the magnesium silicate compound of Example 4 was 0.08% by mass. The BET specific surface area of ​​the magnesium silicate compound of Example 4 was 702 m ２ The total pore volume of the magnesium silicate compound of Example 4 was 1.07 cm ３ / g. Furthermore, the liquid pH of the magnesium silicate compound of Example 4 was 8.4. The solid acid amount of the magnesium silicate compound of Example 4 was 1.62 mmol / g. The average particle size of the magnesium silicate compound of Example 4 was 39.8 μm. Furthermore, the powder X-ray diffraction pattern of the magnesium silicate compound of Example 4 showed that it was amorphous, as shown in FIG. 2.

[0086] (Adsorption Test 1) An adsorption test was carried out in exactly the same manner as Adsorption Test 1 in Example 1, and the potassium concentration in the filtrate was 162 ppm.

[0087] (Adsorption Test 2) An adsorption test was carried out in exactly the same manner as Adsorption Test 2 in Example 1, and the potassium concentration in the filtrate was found to be 78 ppm.

[0088] (Adsorption Test 3) An adsorption test was carried out in exactly the same manner as Adsorption Test 3 in Example 1, and the potassium concentration in the filtrate was 33 ppm.

[0089] Comparative Example 1 (Synthesis Test) A 1.35 mol / L aqueous solution of magnesium sulfate and a 0.55 mol / L aqueous solution of Na ２ O and 1.73 mol / L SiO ２ A constant amount of a No. 3 water glass aqueous solution consisting of the above was continuously poured into a continuous reaction vessel to cause a coprecipitation reaction. The reaction temperature was 40°C. The pH of the resulting reaction slurry was 9.3. The average particle size of the reaction product particles was 12.8 μm. The reaction slurry was then dehydrated by suction filtration using a Nutsche filter, and the resulting solid was washed with ion-exchanged water in an amount 20 times the weight of the solid. The resulting solid was slurried to a concentration of 250 g / L and spray-dried using a spray dryer.

[0090] The dried magnesium silicate compound of Comparative Example 1 thus obtained was subjected to various physical properties measurements. ２ The alkali metal content of the magnesium silicate compound of Comparative Example 1 was 1.60 mass %. The BET specific surface area of ​​the magnesium silicate compound of Comparative Example 1 was 126 m ２ The total pore volume of the magnesium silicate compound of Comparative Example 1 was 0.24 cm ３ / g. Furthermore, the liquid pH of the magnesium silicate compound of Comparative Example 1 was 10.1. The solid acid amount of the magnesium silicate compound of Comparative Example 1 was 0.61 mmol / g. The average particle size of the magnesium silicate compound of Comparative Example 1 was 40.6 μm. Furthermore, the powder X-ray diffraction pattern of the magnesium silicate compound of Comparative Example 1 showed that it was amorphous.

[0091] (Adsorption Test 1) An adsorption test was carried out in exactly the same manner as Adsorption Test 1 in Example 1, and the potassium concentration in the filtrate was 424 ppm.

[0092] (Adsorption Test 2) An adsorption test was carried out in exactly the same manner as Adsorption Test 2 in Example 1, and the potassium concentration in the filtrate was found to be 283 ppm.

[0093] (Adsorption Test 3) An adsorption test was carried out in exactly the same manner as Adsorption Test 3 in Example 1, and the potassium concentration in the filtrate was 65 ppm.

[0094] The measurement results of various physical properties of each magnesium silicate compound of Examples 1 to 4 and Comparative Example 1 are shown in the following Table 1. The potassium concentration in the filtrate in the adsorption test is referred to as "residual K amount" in Table 1.

[0095]

[0096] As shown in Table 1, the adsorbents made of the magnesium silicate compounds of Examples 1 to 4 had a small amount of residual K in the adsorption test, and were found to be able to exhibit extremely excellent adsorption performance for alkali metals. On the other hand, the adsorbent made of the magnesium silicate compound of Comparative Example 1 had a large amount of residual K in the adsorption test, and was found to have insufficient adsorption performance for alkali metals.

[0097] The adsorbent of the present invention has a much higher adsorption capacity than conventional adsorbents made of magnesium silicate compounds and can adsorb adsorbates with a small amount used, so it can be suitably used, for example, as an adsorbent for various industrial applications. The adsorbent of the present invention is particularly useful as an adsorbent for adsorbing and removing an alkali metal-containing basic catalyst in the production of polyether polyols.

Claims

1. An adsorbent comprising an amorphous magnesium silicate compound, The magnesium silicate compound is The alkali metal content is 1.20% by mass or less, The above adsorbent is characterized in that the solid acidity is 0.70 mmol / g or more.

2. The adsorbent according to claim 1, wherein the magnesium silicate compound is a compound represented by the following formula (1): (MgO) ｘ ・SiO ２ ・mH ２ O ・・・(1) [In formula (1), x is a number satisfying 0.1≦x≦0.5, and m is a number satisfying 0.1≦m≦1.5.]

3. The magnesium silicate compound has a BET specific surface area of ​​200 m ２ / g to 1000m ２ / g.

4. The total pore volume of the magnesium silicate compound is 0.40 cm ３ / g ~ 1.50 cm ３ / g.

5. A method for reducing the alkali metal content in a polyether polyol, comprising contacting the polyether polyol containing an alkali metal-containing basic catalyst with the adsorbent of claim 1.