Modified solid base catalyst, preparation method and application

Abstract

The invention discloses a modified solid base catalyst, a preparation method and application, the preparation method comprises the following steps: potassium salt, magnesium-aluminum hydrotalcite and gamma-Al2O3 are used as raw materials, the modified solid base catalyst is prepared by an impregnation method, and the potassium salt comprises at least one of alkaline potassium salt and salt capable of being decomposed to obtain potassium oxide. The potassium salt is adopted to modify the magnesium-aluminum hydrotalcite solid base catalyst, hydrotalcite is an alkaline molecular sieve and has good catalytic activity due to a unique lamellar large-framework structure and a high specific surface area, and the alkalinity of the solid base catalyst can be further enhanced by introduction of the potassium salt, so that the solid base catalyst has good catalytic activity. Therefore, the yield of monoglyceride can be improved when the catalyst is applied to preparation of monoglyceride by a transesterification method; meanwhile, gamma-Al2O3 is introduced into the catalyst, so that the repeated use capability of hydrotalcite can be improved while the excellent catalytic performance of hydrotalcite is retained, and industrial application is facilitated.

Description

Technical Field

[0001] The invention relates to the fields of oil conversion and utilization and fine chemical technology, and in particular to a modified solid base catalyst, a preparation method and application thereof. Background Art

[0002] The surfactant raw materials used in industry are mostly extracted from fossil resources, and they are difficult to biodegrade, toxic and irritating. At the same time, the increasing shortage of fossil resources has brought about a series of environmental and energy problems. Biomass resources such as oils and fats have been widely studied and paid attention to due to their green renewable nature. At present, environmentally friendly oil-based surfactants have broad market prospects due to their advantages such as easy biodegradation, mildness, non-irritation and non-toxicity.

[0003] Monoglycerol fatty acid ester (abbreviated as monoglyceride, MAGs) is an additive widely used in the food, medicine, cosmetics, and detergent industries. It is a high-value-added chemical that is widely used and very important in industry. The synthesis methods of monoglyceride include enzyme catalysis and chemical methods. Although the reaction conditions of enzyme catalysis are mild, the reaction time is long and the cost is high, and it is still a long way from industrial application. The chemical method mainly includes direct esterification and glycerol ester exchange. Among them, the ester exchange method has lower reaction cost and simpler reaction process, and is a more suitable method for industrialization. Glycerol, as a by-product in the preparation of biodiesel, is widely used in the production of monoglyceride due to its price and environmental protection advantages.

[0004] In the process of industrial glycerol transesterification to produce monoglycerides, the catalysts generally used are mainly homogeneous alkaline catalysts such as NaOH and KOH. Although these catalysts are effective, they have problems such as corrosion of equipment, serious environmental pollution, and difficulty in separating catalysts. In recent years, in order to solve this problem, researchers have used solid base catalysts to replace homogeneous base catalysts. Solid base catalysts have the advantages of being easy to separate from the product, not corrosive to equipment, and recyclable. In the process of glycerol transesterification, the catalytic activity of conventional solid base catalysts such as MgO and CaO is still insufficient, which is caused by differences in their structure and alkalinity strength. In order to improve the catalytic effect of solid base catalysis in the preparation of monoglyceride, researchers have conducted a lot of research. The solid base catalysts prepared and used mainly include Zn-Mg composite oxide solid base catalyst (Jiang Wan, Zhou Yongsheng, et al. Zn-Mg composite oxide catalyzes the decomposition of soybean oil glycerol into monoglyceride [J]. Fine Chemicals, 2018, 35(03): 415-422+455.), KF-SnCl2 / Al2O3 supported solid base catalyst (CN201711000675.6), etc. However, in the process of solid base catalyst catalysis for the preparation of monoglyceride, there are still the following main problems: (1) The catalytic activity of existing solid base catalysts is low, and it is difficult to obtain monoglyceride with a high yield; (2) In current research work, some solid bases with excellent catalytic activity have poor recycling capacity. Therefore, it is particularly important to prepare a catalyst with high catalytic activity and recyclability. Summary of the invention

[0005] The purpose of the present invention is to provide a modified solid base catalyst, a preparation method and an application thereof, so as to overcome the problems of low catalytic activity and poor reusability of existing solid base catalysts.

[0006] The present invention is achieved in that:

[0007] In a first aspect, the present invention provides a method for preparing a modified solid base catalyst, comprising: using potassium salt, magnesium aluminum hydrotalcite and γ-Al2O3 as raw materials, and adopting an impregnation method to prepare a modified solid base catalyst, wherein the potassium salt includes at least one of a potassium salt with alkalinity and a salt that can be decomposed to obtain potassium oxide.

[0008] In an optional embodiment, the mass ratio of the potassium salt, magnesium aluminum hydrotalcite and γ-Al2O3 is 0.8:(0.5-1.5):(0.5-1.5).

[0009] In an optional embodiment, the potassium salt includes at least one of potassium nitrate and potassium carbonate.

[0010] In an optional embodiment, the process comprises: stirring, standing, oil bathing, drying, grinding and calcining a mixture comprising the raw materials and water in sequence to obtain the modified solid base catalyst.

[0011] In an optional embodiment, the stirring temperature is 40-60° C. and the stirring time is greater than 6 h;

[0012] and / or, the standing temperature is 40-60°C and the standing time is greater than 10 hours;

[0013] and / or, the oil bath temperature is 80-100° C., and the oil bath time is 4-6 h;

[0014] And / or, the calcination temperature is 650-750°C and the calcination time is 5-7h.

[0015] In a second aspect, the present invention provides a modified solid base catalyst, comprising a potassium-containing active ingredient and a carrier for loading the active ingredient, wherein the carrier is magnesium aluminum hydrotalcite and γ-Al2O3, and the potassium in the potassium-containing active ingredient is partially present in the form of potassium oxide or alkaline potassium salt, and partially bonded to the carrier by KO bonds.

[0016] In a third aspect, the present invention provides a method for preparing monoglyceride, comprising: heating a reaction solution comprising triolein, glycerol and the modified solid base catalyst described in the aforementioned embodiment to perform an ester exchange reaction to generate monoglyceride.

[0017] In an optional embodiment, the mass ratio of the modified solid base catalyst to triolein is (0.1-1.5) wt %.

[0018] In an alternative embodiment, the molar ratio of triolein to glycerol is 1:(2-4.5).

[0019] In an optional embodiment, the temperature of the transesterification reaction is 180-220° C., and the time is 1-4 hours.

[0020] The present invention has the following beneficial effects:

[0021] The present invention adopts potassium salt to modify the magnesium aluminum hydrotalcite solid base catalyst. Hydrotalcite is a basic molecular sieve. Due to its unique lamellar large skeleton structure and high specific surface area, it has good catalytic activity. The introduction of potassium salt can further enhance the basicity of the solid base catalyst, so that when it is applied to prepare monoglyceride by ester exchange method, the yield of monoglyceride can be improved. At the same time, gamma-Al2O3 is introduced into the catalyst, which can improve the reusability of the hydrotalcite while retaining the excellent catalytic performance of the hydrotalcite, which is more conducive to industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 This is the XRD pattern of the K / HT-Al2O3 modified solid base catalyst prepared in Example 1. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0025] An embodiment of the present invention provides a method for preparing a modified solid base catalyst, comprising: using potassium salt, magnesium aluminum hydrotalcite and γ-Al2O3 as raw materials, and adopting an impregnation method to prepare a modified solid base catalyst, wherein the potassium salt includes at least one of a potassium salt with alkalinity and a salt that can be decomposed to obtain potassium oxide.

[0026] The present invention adopts potassium salt to modify the magnesium aluminum hydrotalcite solid base catalyst. Hydrotalcite is a basic molecular sieve. Due to its unique lamellar large skeleton structure and high specific surface area, it has good catalytic activity. The introduction of potassium salt can further enhance the basicity of the solid base catalyst, so that when it is applied to prepare monoglyceride by ester exchange method, the yield of monoglyceride can be improved. At the same time, gamma-Al2O3 is introduced into the catalyst, which can improve the reusability of the hydrotalcite while retaining the excellent catalytic performance of the hydrotalcite, which is more conducive to industrial application.

[0027] In an optional embodiment, the mass ratio of the potassium salt, magnesium aluminum hydrotalcite and γ-Al2O3 is 0.8:(0.5-1.5):(0.5-1.5), preferably 0.8:1:1.

[0028] In an optional embodiment, the potassium salt includes at least one of potassium nitrate and potassium carbonate.

[0029] Among them, potassium nitrate can be decomposed to obtain alkaline oxide potassium oxide, which is beneficial to improve the alkalinity of the solid base catalyst, and then to improve the catalytic activity; potassium carbonate itself is alkaline, and even if it is not decomposed, it can increase the alkalinity of the solid base catalyst, and can also improve the catalytic activity.

[0030] In an optional embodiment, the process comprises: stirring, standing, oil bathing, drying, grinding and calcining a mixture comprising the raw materials and water in sequence to obtain the modified solid base catalyst.

[0031] In an optional embodiment, the stirring temperature is 40-60°C, and the stirring time is greater than 6 hours; preferably, the stirring temperature is 50°C, and the stirring time is 6 hours;

[0032] And / or, the standing temperature is 40-60°C, and the standing time is greater than 10 hours; preferably, the standing temperature is 50°C, and the standing time is 10 hours;

[0033] And / or, the oil bath temperature is 80-100°C, and the oil bath time is 4-6h; preferably, the oil bath temperature is 90°C, and the oil bath time is 5h;

[0034] And / or, the calcination temperature is 650-750° C., and the calcination time is 5-7 hours; preferably, the calcination temperature is 700° C., and the calcination time is 6 hours.

[0035] The embodiment of the present invention also provides a modified solid base catalyst, including a potassium-containing active ingredient and a carrier for loading the active ingredient, wherein the carrier is magnesium aluminum hydrotalcite and γ-Al2O3, and the potassium in the potassium-containing active ingredient is partially present in the form of potassium oxide or alkaline potassium salt, and partially bonded to the carrier by KO bonds.

[0036] The embodiment of the present invention also provides a method for preparing monoglyceride, comprising: heating a reaction solution comprising triolein, glycerol and the modified solid base catalyst described in the above embodiment to perform an ester exchange reaction to generate monoglyceride.

[0037] In an optional embodiment, the mass ratio of the modified solid base catalyst to triolein is (0.1-1.5) wt %.

[0038] In an alternative embodiment, the molar ratio of triolein to glycerol is 1:(2-4.5).

[0039] In an optional embodiment, the temperature of the transesterification reaction is 180-220° C., and the time is 1-4 hours.

[0040] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0041] Determination of monoglyceride content: GB / T22328-2008 method was used to determine the content of monoglyceride.

[0042] Calculation of monoglyceride yield: the amount of monoglyceride substance produced / the amount of triglyceride substance added.

[0043] Embodiment 1:

[0044] The present embodiment provides a method for preparing monoglyceride, which specifically comprises the following steps:

[0045] 8g KNO3, 10g magnesium aluminum hydrotalcite and 10g γ-Al2O3 were added to deionized water to soak all the solids, stirred at 50℃ for 6 hours, and then allowed to stand at 50℃ for 11 hours. Then, they were heated in a 90℃ oil bath for 5 hours, dried at 110℃ for 12 hours, and calcined at 700℃ for 6 hours to obtain a K / HT-Al2O3 (component ratios were 0.8:1:1) modified solid base catalyst. The XRD pattern is shown in the figure below. Figure 1 shown.

[0046] Then, 10 g of triolein and 4.2 g of glycerol were added to the reactor, and 0.1 g of K / HT-Al2O3 solid base catalyst (the component ratio was 0.8:1:1) was added, and the reaction was heated to 190°C. The reaction time was 2 hours. After the reaction, the solid and liquid products were separated, and the monoglyceride content in the liquid product was determined. The yield of monoglyceride was measured to be 55.4%.

[0047] Embodiment 2:

[0048] The present embodiment provides a method for preparing monoglyceride, which specifically comprises the following steps:

[0049] 8g KNO3, 5g magnesium aluminum hydrotalcite and 15g γ-Al2O3 were added to deionized water to soak all the solids, stirred at 50°C for 7 hours, and then allowed to stand for 12 hours. Then, the mixture was heated in a 90°C oil bath for 5 hours, dried at 110°C for 12 hours, and calcined at 700°C for 6 hours to obtain a K / HT-Al2O3 (component ratios were 0.8:0.5:1.5, respectively) modified solid base catalyst.

[0050] Then, 10 g of triolein and 4.2 g of glycerol were added to the reactor, and 0.1 g of K / HT-Al2O3 solid base catalyst (the component ratios were 0.8:0.5:1.5) was added, and the reaction was heated to 190°C. The reaction time was 2 hours. After the reaction was completed, the solid and liquid products were separated, and the monoglyceride content in the liquid product was determined. The yield of monoglyceride was measured to be 51.2%.

[0051] Embodiment 3:

[0052] The present embodiment provides a method for preparing monoglyceride, which specifically comprises the following steps:

[0053] 8g KNO3, 15g magnesium aluminum hydrotalcite and 5g γ-Al2O3 were added to deionized water to soak all the solids, stirred at 50°C for 6.5 hours, and then allowed to stand for 12 hours. Then, the mixture was heated in a 90°C oil bath for 5 hours, dried at 110°C for 13 hours, and calcined at 700°C for 6 hours to obtain a K / HT-Al2O3 (component ratios were 0.8:1.5:0.5, respectively) modified solid base catalyst.

[0054] Then, 10 g of triolein and 4.2 g of glycerol were added to the reactor, and 0.1 g of K / HT-Al2O3 solid base catalyst (the component ratios were 0.8:1.5:0.5) was added, and the reaction was heated to 190°C. The reaction time was 2 hours. After the reaction was completed, the solid and liquid products were separated, and the monoglyceride content in the liquid product was determined. The yield of monoglyceride was measured to be 53.1%.

[0055] Embodiment 4:

[0056] The present embodiment provides a method for preparing monoglyceride, which specifically comprises the following steps:

[0057] 10 g of triolein and 4.2 g of glycerol were added to a reactor, and 0.1 g of the K / HT-Al2O3 solid base catalyst prepared in Example 1 (the component ratio was 0.8:1:1) was added, and the reaction was heated to 200°C. The reaction time was 2 hours. After the reaction was completed, the solid and liquid products were separated, and the monoglyceride content in the liquid product was measured. The yield of monoglyceride was measured to be 58.4%.

[0058] Embodiment 5:

[0059] The present embodiment provides a method for preparing monoglyceride, which specifically comprises the following steps:

[0060] 10 g of triolein and 3.15 g of glycerol were added to a reactor, and 0.08 g of the K / HT-Al2O3 solid base catalyst prepared in Example 1 (the component ratio was 0.8:1:1) was added, and the mixture was heated to 200°C. The reaction time was 2 hours. After the reaction was completed, the product was separated into solid and liquid, and the K / HT-Al2O3 solid base catalyst that had undergone a single reaction was separated. The monoglyceride content in the liquid product was measured, and the yield of monoglyceride was found to be 56.5%.

[0061] The above steps were repeated with the K / HT-Al2O3 solid base catalyst that had undergone a primary reaction to obtain the K / HT-Al2O3 solid base catalyst that had undergone a secondary reaction. The monoglyceride content in the liquid product was measured, and the yield of monoglyceride was measured to be 54.7%.

[0062] The above steps were repeated with the K / HT-Al2O3 solid base catalyst that had undergone three reactions to obtain the K / HT-Al2O3 solid base catalyst that had undergone four reactions. The monoglyceride content in the liquid product was measured, and the yield of monoglyceride was measured to be 53.2%.

[0063] The above steps were repeated with the K / HT-Al2O3 solid base catalyst that had undergone five reactions to obtain the K / HT-Al2O3 solid base catalyst that had undergone six reactions. The monoglyceride content in the liquid product was measured, and the yield of monoglyceride was found to be 48.2%.

[0064] Embodiment 6:

[0065] This embodiment provides a method for preparing monoglyceride, which is different from Embodiment 4 in that the reaction temperature is changed.

[0066] When the reaction temperature was 180°C, the yield of monoglyceride was measured to be 47.8%.

[0067] When the reaction temperature was 210°C, the yield of monoglyceride was measured to be 58.5%.

[0068] When the reaction temperature was 220°C, the yield of monoglyceride was measured to be 58.7%.

[0069] Embodiment 7:

[0070] This embodiment provides a method for preparing monoglyceride, which is different from Embodiment 4 in that the reaction time is changed.

[0071] When the reaction time was 0.5 h, the yield of monoglyceride was measured to be 27.3%.

[0072] When the reaction time was 1 h, the yield of monoglyceride was measured to be 42.8%.

[0073] When the reaction time was 3 h, the yield of monoglyceride was measured to be 58.9%.

[0074] Embodiment 8:

[0075] This embodiment provides a method for preparing monoglyceride, which is different from Embodiment 4 in that the amount of catalyst used is changed.

[0076] When the amount of catalyst used was 0.01 g, the yield of monoglyceride was measured to be 27.3%.

[0077] When the amount of catalyst used was 0.04 g, the yield of monoglyceride was measured to be 42.8%.

[0078] When the amount of catalyst used was 0.2 g, the yield of monoglyceride was measured to be 58.9%.

[0079] Embodiment 9:

[0080] This embodiment provides a method for preparing monoglyceride, which is different from Embodiment 5 in that the amount of raw material glycerol is changed.

[0081] When the amount of glycerol used was 2.1 g, the yield of monoglyceride was measured to be 47.1%.

[0082] When the amount of glycerol used was 5.25 g, the yield of monoglyceride was measured to be 57.8%.

[0083] Comparative Example 1:

[0084] This comparative example provides a method for preparing monoglyceride, which is different from Example 4 in that no catalyst is used, and the yield of monoglyceride is measured to be 8.6%.

[0085] Comparative Example 2:

[0086] This comparative example provides a method for preparing monoglyceride, which differs from Example 4 in that 0.1 g of hydrotalcite (HT) solid base catalyst is used instead of K / HT-Al2O3 solid base catalyst (the component ratio is 0.8:1:1, respectively), and the yield of monoglyceride is measured to be 35.5%.

[0087] Comparative Example 3:

[0088] This comparative example provides a method for preparing monoglyceride, which is different from Example 4 in that 0.1 g of K / HT solid base catalyst (the component ratio is 0.8:2) is used instead of K / HT-Al2O3 solid base catalyst (the component ratio is 0.8:1:1), and the yield of monoglyceride is 51.4%;

[0089] The preparation method of K / HT solid base catalyst includes: adding 8g KNO3 and 20g magnesium aluminum hydrotalcite to an appropriate amount of deionized water (to fully soak the solid), stirring at 50°C for 6 hours, and standing for 11 hours after stirring. Then, heating in a 90°C oil bath for 5 hours, drying at 110°C for 12 hours, and calcining at 700°C for 6 hours to obtain K / HT (component ratios are 0.8:2) modified solid base catalyst.

[0090] Comparative Example 4:

[0091] This comparative example provides a method for preparing monoglyceride, which differs from Example 5 in that 0.1 g of the K / HT solid base catalyst prepared in Comparative Example 3 (the component ratio is 0.8:2) is used instead of the K / HT-Al2O3 solid base catalyst (the component ratio is 0.8:1:1), and after the reaction is completed, the product is separated into solid and liquid, and the K / HT solid base catalyst that has undergone one reaction is separated. The monoglyceride content in the liquid product is measured, and the yield of monoglyceride is measured to be 52.8%.

[0092] The above steps were repeated with the K / HT solid base catalyst that had undergone the primary reaction to obtain the K / HT solid base catalyst that had undergone the secondary reaction. The monoglyceride content in the liquid product was measured, and the yield of the monoglyceride was measured to be 43.9%.

[0093] The above steps were repeated with the K / HT solid base catalyst that had undergone three reactions to obtain the K / HT solid base catalyst that had undergone four reactions. The monoglyceride content in the liquid product was measured, and the yield of the monoglyceride was found to be 36.1%.

[0094] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a modified solid base catalyst, characterized in that: include: The modified solid base catalyst is prepared by using potassium salt, magnesium aluminum hydrotalcite and gamma-Al2O3 as raw materials through an impregnation method, wherein the potassium salt comprises at least one of potassium salt with alkalinity and salt that can be decomposed to obtain potassium oxide.

2. The method for preparing a modified solid base catalyst according to claim 1, characterized in that: The mass ratio of the potassium salt, magnesium aluminum hydrotalcite and γ-Al2O3 is 0.8:(0.5-1.5):(0.5-1.5).

3. The method for preparing a modified solid base catalyst according to claim 1, characterized in that: The potassium salt includes at least one of potassium nitrate and potassium carbonate.

4. The method for preparing a modified solid base catalyst according to claim 1, characterized in that: include: The mixture including the raw materials and water is stirred, allowed to stand, oil bathed, dried, ground and calcined in sequence to obtain the modified solid base catalyst.

5. The method for preparing a modified solid base catalyst according to claim 1, characterized in that: The stirring temperature is 40-60°C and the stirring time is greater than 6h; and / or, the standing temperature is 40-60°C and the standing time is greater than 10 hours; and / or, the oil bath temperature is 80-100° C., and the oil bath time is 4-6 h; And / or, the calcination temperature is 650-750°C and the calcination time is 5-7h.

6. A modified solid base catalyst, characterized in that: The invention comprises a potassium-containing active ingredient and a carrier for loading the active ingredient, wherein the carrier is magnesium aluminum hydrotalcite and γ-Al2O3, and the potassium in the potassium-containing active ingredient partially exists in the form of potassium oxide or alkaline potassium salt, and partially is bonded to the carrier by KO bond.

7. A method for preparing monoglyceride, characterized in that: include: The reaction solution including triolein, glycerol and the modified solid base catalyst according to claim 1 is heated to carry out an ester exchange reaction to generate monoglyceride.

8. The method for preparing monoglyceride according to claim 7, characterized in that: The mass ratio of the modified solid base catalyst to triolein is (0.1-1.5) wt %.

9. The method for preparing monoglyceride according to claim 7, characterized in that: The molar ratio of triolein to glycerol is 1:(2-4.5).

10. The method for preparing monoglyceride according to claim 7, characterized in that: The temperature of the transesterification reaction is 180-220° C. and the time is 1-4 hours.

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