Potassium feldspathoid precursors and dispersions thereof, potassium feldspathoid catalysts and methods of making and use

Abstract

This invention discloses a potassium nepheline precursor and its dispersion, a potassium nepheline catalyst, its preparation method, and its applications. The potassium nepheline precursor of this invention has an amino-containing silane coupling agent grafted onto its surface. The potassium nepheline precursor dispersion of this invention comprises a potassium nepheline precursor and a dispersion medium, wherein the average diameter of the potassium nepheline precursor in the dispersion is 5–20 nm. The potassium nepheline catalyst prepared using the potassium nepheline precursor dispersion of this invention exhibits high activity and good stability when used in transesterification reactions to produce biodiesel.

Description

Technical Field

[0001] This invention relates to an alkaline solid catalyst, specifically to a potassium nepheline precursor and a potassium nepheline precursor dispersion, a potassium nepheline catalyst, its preparation method, and its application. Background Technology

[0002] Biodiesel mainly refers to fatty acid esters produced by transesterification of animal, vegetable, or microbial oils with methanol (ethanol). It is a typical "green energy" source, characterized by its environmental friendliness, good engine starting performance, good fuel performance, wide availability of raw materials, and renewable nature. Common solid base catalysts such as KOH and NaOH have solubility in alcohols, leading to difficulties in catalyst recovery when used in biodiesel production. Potassium nepheline (KAlSiO4), with its potassium content in its crystal lattice that is not easily lost at high temperatures, is insoluble in oils and alcohols, and possesses certain basic active centers, meeting the conditions for catalytic production of biodiesel. However, current potassium nepheline catalysts used for catalysis suffer from a series of problems, including large particle size, small specific surface area, and low utilization of active sites, hindering their industrial application.

[0003] The study, titled "Preparation of Biodiesel from Soybean Oil by Solid Alkali Catalysis of Potassium Nepheline" (Wen Guang et al., Molecular Catalysis, Vol. 25, No. 1, February 2011), describes the preparation of potassium nepheline with pore sizes of 0.2–1.0 μm using a co-precipitation method. The resulting biodiesel was used to produce biodiesel from soybean oil, with a yield of only 19.8%.

[0004] CN109012646A discloses a low-temperature synthesis method for potassium nepheline catalysts used in the preparation of biodiesel. This method directly synthesizes bulk potassium nepheline using fly ash, potassium silicate, and potassium hydroxide. After pulverization, bulk potassium nepheline particles with a particle size of 0.150–0.315 mm are obtained. When these potassium nepheline particles are used to catalyze the production of biodiesel from soybean oil, the yield is only 41.2%. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a potassium nepheline precursor, a potassium nepheline dispersion, a potassium nepheline catalyst, and their preparation methods and applications. The potassium nepheline catalyst prepared using the potassium nepheline precursor dispersion of this invention exhibits advantages of high activity and good stability when used in transesterification reactions to produce biodiesel.

[0006] The first aspect of the present invention provides a potassium nepheline precursor, wherein the surface of the potassium nepheline precursor is grafted with an amino-containing silane coupling agent.

[0007] Furthermore, the amino-containing silane coupling agent is selected from (3-aminopropyl)trimethoxysilane, tert-butylpropylaminotrimethoxysilane, N-methylaminopropyltris(trimethylsiloxy)silane, 3-aminopropyldi(trimethylsiloxy)methylsilane, N-(6-aminohexyl)aminomethyltriethoxysilane, 4-amino-3,3-dimethylbutyltrimethoxysilane, and [2-[[3-(trimethoxysilyl)propyl]amino]ethyl]urea At least one of N-[3-(trimethoxysilyl)propyl]ethylenediamine, 3-aminopropyldimethoxymethylsilane, and 3-[bis(2-hydroxyethyl)amino]propane-triethoxysilane, preferably at least one of (3-aminopropyl)trimethoxysilane, N-[3-(trimethoxysilyl)propyl]ethylenediamine, 3-aminopropyldi(trimethylsiloxy)methylsilane, and [2-[[3-(trimethoxysilyl)propyl]amino]ethyl]urea.

[0008] Furthermore, in the potassium nepheline precursor, the amino-containing silane coupling agent accounts for 5 wt% to 30 wt% of the potassium nepheline precursor mass.

[0009] A second aspect of the present invention provides a potassium nepheline precursor dispersion comprising a potassium nepheline precursor and a dispersion medium, wherein the average diameter of the potassium nepheline precursor in the dispersion is 5 to 20 nm.

[0010] Furthermore, in the potassium nepheline precursor dispersion, the potassium nepheline precursor is dispersed as potassium nepheline nanoparticles with an average diameter of 5–20 nm.

[0011] Furthermore, the solid content of the dispersion is 1 wt% to 40 wt%, preferably 5 wt% to 35 wt%.

[0012] Furthermore, the dispersion medium is water.

[0013] A third aspect of this invention provides a method for preparing a potassium nepheline precursor, comprising the following steps:

[0014] (1) Mix silicon source, KOH, potassium salt and alcohol to obtain solution A, and dissolve aluminum salt in alcohol and water to obtain solution B;

[0015] (2) Add solution B to solution A to allow the reaction to proceed;

[0016] (3) Add a mixture of modifier and alcohol to the mixture after the reaction in step (2) and continue the reaction;

[0017] (4) After solid-liquid separation, the product of step (3) is obtained as potassium nepheline precursor.

[0018] Further, in step (1), the silicon source is selected from at least one of tetraethyl orthosilicate and methyl orthosilicate; the potassium salt is selected from at least one of potassium nitrate, potassium acetate, and potassium carbonate; and the aluminum salt is selected from at least one of aluminum nitrate and aluminum acetate.

[0019] Further, in step (1), in solution A, the concentration of the silicon source is 0.2–1.0 mol / L, the concentration of KOH is 0.5–2.0 mol / L, and the concentration of the potassium salt (based on potassium atoms) is 0.25–1.0 mol / L. In solution B, the concentration of the aluminum salt (based on aluminum atoms) is 0.1–0.35 mol / L. In solution B, the mass ratio of the alcohol to water is 20–5:1.

[0020] Furthermore, in step (1), the molar ratio of the aluminum salt in solution B (calculated as aluminum atoms) to the potassium salt in solution A (calculated as potassium atoms) is 1:2 to 6.

[0021] Furthermore, in steps (1) and (3), each alcohol is independently selected from at least one of methanol, ethanol, propanol, ethylene glycol, 1,3-butanediol, isopropanol, and 1,4-butanediol.

[0022] Furthermore, in step (2), the reaction temperature is 20–60°C and the reaction time is 2–10 min.

[0023] Further, in step (3), the mass concentration of the modifier in the mixture of the modifier and the alcohol is 40-200 g / L.

[0024] Furthermore, in step (3), the reaction temperature is 20–60°C and the reaction time is 0.5–3 h.

[0025] Further, in step (3), the modifier is a silane coupling agent with amino groups grafted onto its surface, preferably selected from (3-aminopropyl)trimethoxysilane, tert-butylpropylaminotrimethoxysilane, N-methylaminopropyltris(trimethylsiloxy)silane, 3-aminopropyldi(trimethylsiloxy)methylsilane, N-(6-aminohexyl)aminomethyltriethoxysilane, 4-amino-3,3-dimethylbutyltrimethoxysilane, [2-[[3-(trimethoxysilyl)propyl] [2-[[3-(trimethoxysilyl)propyl]ethylenediamine, 3-aminopropyldimethoxymethylsilane, 3-[bis(2-hydroxyethyl)amino]propane-triethoxysilane, preferably at least one of (3-aminopropyl)trimethoxysilane, N-[3-(trimethoxysilyl)propyl]ethylenediamine, 3-aminopropyldi(trimethylsiloxy)methylsilane, and [2-[[3-(trimethoxysilyl)propyl]amino]ethyl]urea.

[0026] Furthermore, in step (4), the solid-liquid separation can be performed using conventional solid-liquid separation methods such as centrifugation and filtration.

[0027] Further, in step (4), the solid phase obtained after solid-liquid separation is washed and dried to obtain potassium nepheline precursor. The washing can be performed 1 to 5 times using one or more of methanol, ethanol, isopropanol, etc., and the drying temperature is 40 to 90°C.

[0028] The fourth aspect of the present invention provides a method for preparing a potassium nepheline precursor dispersion, comprising the following steps: dispersing the potassium nepheline precursor described in the first aspect or the potassium nepheline precursor prepared by the method described in the third aspect into a dispersion medium to obtain the potassium nepheline precursor dispersion.

[0029] The fifth aspect of the present invention provides a method for preparing a potassium nepheline catalyst, comprising: impregnating a support with a potassium nepheline precursor dispersion prepared by the method of the second aspect or the method of the fourth aspect, and then drying and calcining the support to obtain a potassium nepheline catalyst.

[0030] Furthermore, when the solid content of the potassium nepheline precursor dispersion is greater than 20 wt%, the potassium nepheline precursor dispersion is generally diluted with water to a solid content of 1 wt% to 20 wt% before being impregnated with the carrier.

[0031] Furthermore, the carrier is selected from at least one of activated carbon, silicon dioxide, NaZSM-5 molecular sieve, manganese oxide, zirconium oxide, and alumina.

[0032] Furthermore, the drying temperature is 90–150°C and the time is 1–8 hours, the calcination temperature is 1000–1400°C and the time is 2–5 hours, and the calcination atmosphere is at least one of air, nitrogen, argon, and helium.

[0033] Furthermore, based on the mass of the potassium nepheline catalyst, the potassium nepheline content is 5wt% to 20wt%, and the support content is 80wt% to 95wt%.

[0034] A sixth aspect of the present invention provides a potassium nepheline catalyst prepared by the method described in the fifth aspect.

[0035] A seventh aspect of the present invention provides the application of the potassium nepheline catalyst in the preparation of biodiesel from oils and alcohols.

[0036] Furthermore, the application is as follows: biodiesel is obtained by transesterification of oils and alcohols under the action of the potassium nepheline catalyst.

[0037] Furthermore, the application specifically involves: adding alcohol and the potassium nepheline catalyst into a reactor, purging with nitrogen and / or inert gas, stirring and heating to the reaction temperature, adding oil, and reacting to obtain biodiesel.

[0038] Further, the alcohol is at least one selected from methanol, ethanol, propanol, ethylene glycol, butanol, 1,3-butanediol, isopropanol, and 1,4-butanediol. The oil is selected from at least one selected from soybean oil, palm oil, soybean seed oil, corn oil, and cottonseed oil.

[0039] Furthermore, the mass ratio of the alcohol to the oil is 1 to 5:1, and the mass ratio of the oil to the potassium nepheline catalyst is 1 to 20:1.

[0040] Furthermore, the reactor is generally a high-pressure magnetically stirred tank.

[0041] Furthermore, the reaction temperature is 40–120°C, and the reaction time is 30–180 min.

[0042] Furthermore, after the reaction is complete, the product is cooled, filtered, and distilled to obtain biodiesel.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] 1. In the potassium nepheline precursor of the present invention, a silane coupling agent containing amino groups is grafted onto the surface of potassium nepheline particles in the form of covalent bonds, thereby reducing the surface energy of the potassium nepheline precursor and enabling it to be highly dispersed in the water medium.

[0045] 2. The potassium nepheline precursor dispersion of this invention retains the dispersibility of nanoparticles, ensuring the advantages of nanomaterials for subsequent applications. By preparing the potassium nepheline precursor into a dispersion, loading it onto a support via impregnation, and then calcining it to obtain a monodisperse potassium nepheline supported catalyst, its basic active sites can be fully utilized for corresponding catalytic reactions.

[0046] 3. The supported catalyst prepared by the method of the present invention using potassium nepheline precursor dispersion is particularly suitable for liquid-phase catalytic transesterification reactions of oils and low-carbon alcohols. It can improve the product yield, and the catalyst is stable, has high recycling activity, and is easy to recover. Attached Figure Description

[0047] Figure 1 This is a transmission electron microscope image of the potassium nepheline precursor dispersion in Example 1 of the present invention;

[0048] Figure 2 The image shows the XRD pattern of the potassium nepheline supported catalyst in Example 1 of this invention. Detailed Implementation

[0049] To more clearly illustrate the present invention, the following description, in conjunction with embodiments and accompanying drawings, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0050] In this invention, a Hitachi HT7700 transmission electron microscope (TEM) was used to observe the morphology, size, and dispersibility of the samples. When observing nanoparticles, a sample of appropriate concentration was dropped onto a carbon film, allowed to air dry naturally, and then injected for observation.

[0051] In this invention, an XRD-7000 X-ray diffractometer from Shimadzu Corporation of Japan was used to analyze the crystal form of the product. The scanning range was 2θ = 5° to 80°, and the scanning speed was 10° / min.

[0052] Example 1

[0053] (1) Preparation of potassium nepheline precursor and potassium nepheline precursor dispersion: 1 L of a methanol-water mixture (containing 0.2 mol of aluminum nitrate, with a methanol-to-water mass ratio of 10:1) was added to 1 L of methanol solution (containing 1 mol of KOH, 0.5 mol of KNO3, and 0.4 mol of TEOS). After reacting at 50 °C for 5 min, 100 mL of a methanol solution containing 100 g / L 3-aminopropylbis(trimethylsiloxy)methylsilane was added dropwise. The reaction was continued at 50 °C for 2 h. After the reaction was completed, the mixture was separated into solid and liquid phases, washed three times with methanol, and dried at 50 °C to obtain the potassium nepheline precursor. The obtained potassium nepheline precursor was dispersed in water to obtain a transparent potassium nepheline precursor dispersion with a solid content of 30 wt% and an average particle diameter of 8 nm. The dispersion did not settle after standing for 1 month. Its transmission electron microscopy image is shown below. Figure 1 .

[0054] (2) Preparation of potassium nepheline supported catalyst: 70 g of 15 wt% potassium nepheline precursor dispersion (after dilution with water) was added to 100 g of activated carbon. After impregnation, the mixture was dried at 110 °C for 2 h and calcined at 1100 °C under a nitrogen atmosphere for 3 h to obtain a nano-potassium nepheline supported activated carbon catalyst. Its XRD pattern is shown in [Figure number missing]. Figure 2 .

[0055] (3) Catalyst evaluation: 2g of the catalyst prepared in step (2) and 30g of methanol were added to a high-pressure magnetic stirring vessel. After nitrogen replacement, the mixture was stirred and heated to 60°C. 20g of soybean oil was introduced and stirred for 1 hour. After cooling, the mixture was filtered and distilled to obtain biodiesel. The biodiesel yield of the product was analyzed. The specific results are shown in Table 1.

[0056] Example 2

[0057] Compared with Example 1, the difference lies in step (1), before adding 100 mL of a methanol solution of 100 g / L 3-aminopropylbis(trimethylsiloxy)methylsilane, the reaction was carried out at 50 °C for 3 min. The resulting potassium nepheline precursor dispersion had a solid content of 35 wt%, an average particle diameter of 6 nm, and did not settle after standing for 1 month.

[0058] The catalyst evaluation conditions were the same as in Example 1, and the specific results are shown in Table 1.

[0059] Example 3

[0060] Compared with Example 1, the difference lies in step (1), before adding 100 mL of a methanol solution of 100 g / L 3-aminopropylbis(trimethylsiloxy)methylsilane, the reaction was carried out at 50 °C for 9 min. The resulting potassium nepheline precursor dispersion had a solid content of 15 wt%, an average particle diameter of 15 nm, and did not settle after standing for 1 month.

[0061] The catalyst evaluation conditions were the same as in Example 1, and the specific results are shown in Table 1.

[0062] Example 4

[0063] Compared with Example 1, the difference lies in step (1), where the methanol solution of 3-aminopropylbis(trimethylsiloxy)methylsilane is replaced with a methanol solution of (3-aminopropyl)trimethoxysilane. The resulting potassium nepheline precursor dispersion has a solid content of 32 wt%, an average particle diameter of 7 nm, and does not settle after standing for 1 month.

[0064] The catalyst evaluation conditions were the same as in Example 1, and the specific results are shown in Table 1.

[0065] Example 5

[0066] Compared with Example 1, the difference lies in step (1), where the methanol solution of 3-aminopropyldi(trimethylsiloxy)methylsilane is replaced with a methanol solution of N-[3-(trimethoxysilyl)propyl]ethylenediamine. The resulting potassium nepheline precursor dispersion has a solid content of 20 wt%, an average particle diameter of 14 nm, and does not settle after standing for 1 month.

[0067] The catalyst evaluation conditions were the same as in Example 1, and the specific results are shown in Table 1.

[0068] Example 6

[0069] Compared with Example 1, the difference lies in step (2), where activated carbon is replaced with silicon oxide. The catalyst evaluation conditions are the same as in Example 1, and the specific results are shown in Table 1.

[0070] Example 7

[0071] Compared with Example 1, the difference lies in step (2), where activated carbon is replaced with zirconium oxide. The catalyst evaluation conditions are the same as in Example 1, and the specific results are shown in Table 1.

[0072] Example 8

[0073] Compared with Example 1, the difference lies in step (2), where activated carbon is replaced with alumina. The catalyst evaluation conditions are the same as in Example 1, and the specific results are shown in Table 1.

[0074] Example 9

[0075] Compared with Example 1, the difference lies in step (3), where the reaction temperature is 120°C and the reaction time is 0.5 h. The biodiesel yield results are shown in Table 1.

[0076] Example 10

[0077] Compared with Example 1, the difference lies in step (3), where the reacting oil is palm oil, the reaction temperature is 80°C, and the reaction time is 1 hour. The biodiesel yield results are shown in Table 1.

[0078] Example 11

[0079] Compared with Example 1, the difference lies in step (3), where the reacting oil is rapeseed oil, the reaction temperature is 120℃, and the reaction time is 1h. The biodiesel yield results are shown in Table 1.

[0080] Example 12

[0081] (1) Preparation of potassium nepheline precursor and potassium nepheline precursor dispersion: 1L of a mixed ethanol and water solution (containing 0.17mol of aluminum acetate, with a mass ratio of ethanol to water of 9:1) was added to 1L of ethanol solution (containing 0.8mol of KOH, 0.3mol of K2CO3, and 0.3mol of TMOS). After reacting at 60℃ for 5min, 100mL of an ethanol solution of 80g / L 3-aminopropylbis(trimethylsiloxy)methylsilane was added dropwise, and the reaction was continued for 1.5h. After the reaction was completed, the product was separated into solid and liquid components, washed twice with methanol, and dried at 70℃ to obtain the potassium nepheline precursor. The obtained potassium nepheline precursor was dispersed in water to obtain a transparent potassium nepheline precursor dispersion with a solid content of 25wt% and an average particle diameter of 12nm. The dispersion did not settle after standing for 1 month.

[0082] (2) Preparation of potassium nepheline supported catalyst: 100g of 15wt% dispersion (the above dispersion was diluted with water) was added to 100g of silica. After impregnation, it was dried at 120℃ for 3h and calcined at 1200℃ in air atmosphere for 3h to obtain nano-potassium nepheline supported silica catalyst.

[0083] (3) Catalyst evaluation: 2g of the catalyst prepared in step (2) and 30g of methanol were added to a high-pressure magnetic stirring vessel. After nitrogen purging, the mixture was stirred and heated to 80°C. 10g of soybean oil was introduced and stirred for 0.5h. After cooling, the biodiesel yield of the product was analyzed and shown in Table 1.

[0084] Comparative Example 1

[0085] 1 L of a methanol-water mixture (containing 0.2 mol of aluminum nitrate, with a methanol-to-water mass ratio of 10:1) was added to 1 L of a methanol solution (containing 1 mol of KOH, 0.5 mol of KNO3, and 0.4 mol of TEOS). After reacting at 50 °C for 15 min, 100 mL of a methanol solution containing 100 g / L 3-aminopropylbis(trimethylsiloxy)methylsilane was added dropwise. The reaction was continued at 50 °C for 2 h, but no dispersion was obtained. The resulting material was directly added to activated carbon at the loading rate of Example 1. After impregnation, the carbon was dried at 110 °C for 2 h and calcined at 1100 °C under a nitrogen atmosphere for 3 h to obtain the supported catalyst. The catalyst evaluation was the same as in Example 1. The biodiesel yield is shown in Table 1.

[0086] Comparative Example 2

[0087] 1 L of a methanol-water mixture (containing 0.2 mol of aluminum nitrate, with a methanol-to-water mass ratio of 10:1) was added to 1 L of a methanol solution (containing 1 mol of KOH, 0.5 mol of KNO3, and 0.4 mol of TEOS). After reacting at 80 °C for 5 min, 100 mL of a methanol solution containing 100 g / L 3-aminopropylbis(trimethylsiloxy)methylsilane was added dropwise. The reaction was continued at 50 °C for 2 h, but no dispersion was obtained. The resulting material was directly added to activated carbon at the loading rate of Example 1. After impregnation, the carbon was dried at 110 °C for 2 h and calcined at 1100 °C under a nitrogen atmosphere for 3 h to obtain the supported catalyst. The catalyst evaluation was the same as in Example 1. The biodiesel yield is shown in Table 1.

[0088] Comparative Example 3

[0089] Take 70g of 15wt% KOH solution and add it to 100g of activated carbon. After impregnation, dry at 110℃ for 2h and calcine at 1200℃ under nitrogen atmosphere for 3h to obtain KOH-supported activated carbon catalyst.

[0090] Comparative Example 4

[0091] Take 70g of 15wt% K2CO3 solution and add it to 100g of activated carbon. After impregnation, dry at 110℃ for 2h and calcine at 1200℃ under nitrogen atmosphere for 3h to obtain K2CO3 supported activated carbon catalyst.

[0092] Comparative Example 5

[0093] 1 L of a methanol-water mixture (containing 0.2 mol of aluminum nitrate, with a methanol-to-water mass ratio of 10:1) was added to 1 L of a methanol solution (containing 1 mol of KOH, 0.5 mol of KNO3, and 0.4 mol of TEOS). After reacting at 50 °C for 135 min, a turbid liquid of potassium nepheline precursor was obtained. The obtained material was directly added to activated carbon at the loading rate of Example 1, impregnated, dried at 110 °C for 2 h, and calcined at 1100 °C under a nitrogen atmosphere for 3 h to obtain the supported catalyst. The catalyst evaluation was the same as in Example 1. The biodiesel yield is shown in Table 1.

[0094] Comparative Example 6

[0095] Compared with Example 1, the difference is that in step (1), the methanol solution of 3-aminopropylbis(trimethylsiloxy)methylsilane was not added, and the resulting turbid liquid of potassium nepheline precursor was obtained. It was not loaded on activated carbon and the resulting turbid liquid was directly used to catalyze the production of biodiesel from soybean oil. The biodiesel yield is shown in Table 1.

[0096] Table 1 Biodiesel yield of each example and comparative example

[0097] serial number Biodiesel yield, % Example 1 95 Example 2 96 Example 3 93 Example 4 96 Example 5 93 Example 6 93 Example 7 94 Example 8 93 Example 9 100 Example 10 96 Example 11 98 Example 12 93 Comparative Example 1 46 Comparative Example 2 38 Comparative Example 5 21 Comparative Example 6 20

[0098] The catalysts from Examples 1, 4, 11, 3, and 4 were recycled and biodiesel was prepared again under the same conditions (same as Example 1). The biodiesel yield is shown in Table 2.

[0099] Table 2 Catalyst lifetime evaluation

[0100]

[0101]

[0102] As shown in Table 2, the catalyst of this application still maintains a high biodiesel yield after multiple cycles, indicating good catalyst stability. In contrast, the catalysts of Comparative Examples 3 and 4 showed a significant decrease in biodiesel yield after recycling, indicating low catalytic activity during recycling.

Claims

1. A potassium nepheline precursor dispersion, the dispersion comprising a potassium nepheline precursor and a dispersion medium, wherein the average diameter of the potassium nepheline precursor is 5-20 nm; and the surface of the potassium nepheline precursor is grafted with a silane coupling agent containing an amino group. The amino-containing silane coupling agent is selected from at least one of (3-aminopropyl)trimethoxysilane, tert-butylpropylaminotrimethoxysilane, N-methylaminopropyltris(trimethylsiloxy)silane, 3-aminopropyldi(trimethylsiloxy)methylsilane, N-(6-aminohexyl)aminomethyltriethoxysilane, 4-amino-3,3-dimethylbutyltrimethoxysilane, [2-[[3-(trimethoxysilyl)propyl]amino]ethyl]urea, N-[3-(trimethoxysilyl)propyl]ethylenediamine, 3-aminopropyldimethoxymethylsilane, and 3-[bis(2-hydroxyethyl)amino]propane-triethoxysilane.

2. The potassium nepheline precursor dispersion according to claim 1, characterized in that, The amino-containing silane coupling agent is at least one of (3-aminopropyl)trimethoxysilane, N-[3-(trimethoxysilyl)propyl]ethylenediamine, 3-aminopropyldi(trimethylsiloxy)methylsilane, and [2-[[3-(trimethoxysilyl)propyl]amino]ethyl]urea.

3. The potassium nepheline precursor dispersion according to claim 1, characterized in that, In the potassium nepheline precursor, the amino-containing silane coupling agent accounts for 5 wt% to 30 wt% of the potassium nepheline precursor mass.

4. The potassium nepheline precursor dispersion according to claim 1, characterized in that, The solid content of the dispersion is 1wt% to 40wt%.

5. The potassium nepheline precursor dispersion according to claim 4, characterized in that, The solid content of the dispersion is 5wt% to 35wt%.

6. The potassium nepheline precursor dispersion according to claim 1, characterized in that, The dispersion medium is water.

7. The potassium nepheline precursor dispersion according to claim 1, characterized in that, The method for preparing the potassium nepheline precursor includes the following steps: (1) Mix silicon source, KOH, potassium salt and alcohol to obtain solution A, and dissolve aluminum salt in alcohol and water to obtain solution B; (2) Add solution B to solution A to allow the reaction to proceed; (3) Add a mixture of modifier and alcohol to the mixture after the reaction in step (2) and continue the reaction; (4) After solid-liquid separation, the product of step (3) is used to obtain potassium nepheline precursor; The modifier is a silane coupling agent with amino groups grafted onto its surface.

8. The potassium nepheline precursor dispersion according to claim 7, characterized in that: In step (1), the silicon source is selected from at least one of tetraethyl orthosilicate and methyl orthosilicate; the potassium salt is selected from at least one of potassium nitrate, potassium acetate and potassium carbonate; and the aluminum salt is selected from at least one of aluminum nitrate and aluminum acetate.

9. The potassium nepheline precursor dispersion according to claim 7, characterized in that: In step (1), in solution A, the concentration of silicon source is 0.2~1.0 mol / L, the concentration of KOH is 0.5~2.0 mol / L, and the concentration of potassium salt (calculated as potassium atoms) is 0.25~1.0 mol / L; in solution B, the concentration of aluminum salt (calculated as aluminum atoms) is 0.1~0.35 mol / L; in solution B, the mass ratio of alcohol to water is 20~5:1; the molar ratio of aluminum salt in solution B (calculated as aluminum atoms) to potassium salt in solution A (calculated as potassium atoms) is 1:2~6.

10. The potassium nepheline precursor dispersion according to claim 7, characterized in that: In steps (1) and (3), each alcohol is independently selected from at least one of methanol, ethanol, propanol, ethylene glycol, 1,3-butanediol, isopropanol, and 1,4-butanediol.

11. The potassium nepheline precursor dispersion according to claim 7, characterized in that: In step (2), the reaction temperature is 20~60℃ and the reaction time is 2~10min.

12. The potassium nepheline precursor dispersion according to claim 7, characterized in that: In step (3), the mass concentration of the modifier in the mixture of the modifier and alcohol is 40~200g / L; the reaction temperature is 20~60℃ and the reaction time is 0.5~3h.

13. The potassium nepheline precursor dispersion according to claim 7, characterized in that: The modifier is at least one of (3-aminopropyl)trimethoxysilane, N-[3-(trimethoxysilyl)propyl]ethylenediamine, 3-aminopropyldi(trimethylsiloxy)methylsilane, and [2-[[3-(trimethoxysilyl)propyl]amino]ethyl]urea.

14. A method for preparing the potassium nepheline precursor dispersion according to any one of claims 1-13, comprising the following steps: The potassium nepheline precursor is dispersed in a dispersion medium to obtain a potassium nepheline precursor dispersion.

15. A method for preparing a potassium nepheline catalyst, comprising: The potassium nepheline catalyst is obtained by impregnating the support with the potassium nepheline precursor dispersion as described in any one of claims 1-13 or the potassium nepheline precursor dispersion prepared by the method described in claim 14, followed by drying and calcination.

16. A potassium nepheline catalyst, characterized in that, Prepared using the method described in claim 15.

17. The use of a potassium nepheline catalyst according to claim 16 in the preparation of biodiesel from oils and alcohols.

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