A catalyst and its use in the production of ethanol by hydrogenation of esters

Abstract

The present application relates to the technical field of catalyst, and proposes a catalyst and application thereof in preparation of ethanol by ester hydrogenation. The catalyst is a core-shell catalyst, and raw materials of the core-shell catalyst include an inner core carrier and an outer shell active component precursor. The outer shell active component precursor includes a water-soluble copper salt, a water-soluble lanthanum salt and a water-soluble manganese salt. The inner core carrier includes halloysite. The weight ratio of the water-soluble lanthanum salt and the water-soluble manganese salt to the water-soluble copper salt is 1:3-4. Through the technical solution, the problem of low ester conversion rate and ethanol selectivity caused by low catalytic activity and poor stability of the catalyst in the process of preparing ethanol by ester hydrogenation in the related art is solved.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a catalyst and its application in the hydrogenation of esters to produce ethanol. Background Technology

[0002] Ethanol, as an important basic chemical and fuel additive, has wide applications in organic synthesis, medicine, food, and energy. Industrial production methods for ethanol mainly include fermentation using sugars or starch as raw materials, hydration using petroleum-based ethylene as raw material, and indirect synthesis routes based on coal chemical processes using syngas.

[0003] With the development of green chemical technology, the ester catalytic hydrogenation route to produce ethanol has received widespread attention and has become one of the important ways to produce ethanol.

[0004] Many esters containing two-carbon groups can be hydrogenated to produce ethanol, including ethyl acetate, methyl acetate, and isopropyl acetate. However, the commonly used catalysts in existing ester hydrogenation ethanol production technologies mainly include copper-based and noble metal (such as Ru and Pd) catalysts. While noble metal catalysts can provide effective hydrogenation capabilities, they exhibit high activity towards both C=O and C=C bonds, which reduces the selectivity of the target alcohol. Furthermore, the high cost of noble metal catalysts limits their large-scale industrial application. Copper-based catalysts are less expensive and show good selective hydrogenation of C=O bonds in ester hydrogenation reactions. However, they generally suffer from problems such as easy aggregation and migration of the copper-based active component, leading to decreased catalytic activity and stability during the reaction. This weakens the catalyst's activity and selectivity, thus affecting the ester conversion rate and the selectivity of the target product, ethanol.

[0005] Therefore, the present invention provides a catalyst with good catalytic activity and stability, thereby improving the conversion rate of esters and the selectivity of target ethanol, which is of great significance for meeting the process production requirements. Summary of the Invention

[0006] This invention proposes a catalyst and its application in the hydrogenation of esters to ethanol, which solves the problems of low ester conversion rate and low ethanol selectivity in the hydrogenation of esters to ethanol due to the low catalytic activity and poor stability of the catalyst in related technologies.

[0007] The technical solution of the present invention is as follows:

[0008] This invention proposes a catalyst, which is a core-shell catalyst, wherein the raw materials of the core-shell catalyst include a core support and a shell active component precursor;

[0009] The shell active component precursor includes water-soluble copper salt, water-soluble lanthanum salt, and water-soluble manganese salt;

[0010] The core carrier includes halloysite;

[0011] The weight ratio of the water-soluble lanthanum salt, the water-soluble manganese salt, and the water-soluble copper salt is 1:3~4.

[0012] As a further technical solution, the weight ratio of the water-soluble manganese salt to the water-soluble lanthanum salt is 1 to 9:1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, or 9:1, preferably 3 to 4:1.

[0013] In the catalyst of this invention, by optimizing the ratio of water-soluble manganese salt to water-soluble lanthanum salt, when the weight ratio of water-soluble manganese salt to water-soluble lanthanum salt is 3~4:1, the stability and catalytic activity of the catalyst can be further improved, thereby further improving the ester conversion rate and the selectivity of ethanol.

[0014] As a further technical solution, the water-soluble copper salt includes one or more of copper nitrate, copper acetate, and copper sulfate, preferably copper nitrate;

[0015] The water-soluble lanthanum salt includes one or more of lanthanum chloride, lanthanum nitrate hexahydrate, and lanthanum acetate, preferably lanthanum nitrate hexahydrate;

[0016] The water-soluble manganese salt includes one or more of manganese acetate tetrahydrate, manganese nitrate, and manganese chloride tetrahydrate, preferably manganese acetate tetrahydrate.

[0017] This invention proposes a method for preparing a catalyst, comprising the following steps:

[0018] A1. Dissolve the shell active component precursor in water to obtain a mixed solution;

[0019] A2. Add ammonium nitrate to the mixed solution, mix well, add precipitant and the core carrier, carry out hydrothermal reaction, cool to obtain precipitate, wash, dry, calcine, crush and shape the precipitate to obtain catalyst.

[0020] As a further technical solution, the amount of ammonium nitrate added is 30% to 50% of the weight of the core carrier.

[0021] As a further technical solution, the precipitant includes one of ammonia and urea, preferably urea;

[0022] The amount of the precipitant added is 1.3 to 1.6 times the weight of the precursor of the shell active component, for example, it can be 1.3 times, 1.4 times, 1.5 times, or 1.6 times, preferably 1.3 times or 1.6 times.

[0023] As a further technical solution, the amount of the shell active component precursor added is 40% to 50% of the weight of the core carrier.

[0024] As a further technical solution, in step A1, the weight ratio of the shell active component precursor to the water is 1:50~100.

[0025] As a further technical solution, in step A2, the temperature of the hydrothermal reaction is 90~120℃ and the time is 4~12h.

[0026] As a further technical solution, in step A2, the drying temperature is 70~80℃ and the time is 5~8h.

[0027] As a further technical solution, in step A2, the calcination temperature is 350~450℃ and the time is 2~3h.

[0028] As a further technical solution, the particle size of the catalyst is 4-50 mesh.

[0029] As a further technical solution, the halloysite is modified halloysite, and the raw materials for the modified halloysite include halloysite and aluminum acetylacetone in a weight ratio of 20:2~7.

[0030] In the catalyst of this invention, before the halloysite is coated with active components, aluminum acetylacetonate is used to modify its surface, thereby enhancing the adhesion between the halloysite inner shell support and the outer shell active components. This further reduces the migration and aggregation of the outer shell active metal during the reaction process, further improving the stability of the catalyst and ultimately increasing the conversion rate of the ester.

[0031] In the catalyst of this invention, the weight ratio of halloysite to aluminum acetylacetonate is adjusted to 20:2 to 7, for example, it can be 20:2, 20:3, 20:4, 20:5, 20:6, or 20:7, preferably 20:3 to 5. When the weight ratio of halloysite to aluminum acetylacetonate is 20:3 to 5, the conversion rate of the ester can be further improved.

[0032] As a further technical solution, the preparation method of the modified halloysite includes the following steps:

[0033] The aluminum acetylacetone was dispersed in an ethanol solution, the pH was adjusted to 5-6, halloysite was added and mixed, concentrated and dried to obtain the modified halloysite.

[0034] As a further technical solution, during the mixing process, the stirring speed is 300~400 rpm, the temperature is 40~50℃, and the time is 20~40 min.

[0035] As a further technical solution, when adjusting the pH value to 5-6, a nitric acid solution with a mass fraction of 10%-15% is used.

[0036] This invention proposes the application of the catalyst described above in the hydrogenation of esters to prepare ethanol.

[0037] As a further technical solution, the method for preparing ethanol includes the following steps:

[0038] The ester and hydrogen are hydrogenated under the catalyst to obtain the ethanol.

[0039] In this invention, esters are mixed with hydrogen in a certain proportion and catalytically hydrogenated under the action of a specific catalyst, at a certain temperature and pressure to finally obtain ethanol. This route has a short reaction path, relatively high ethanol selectivity, and low reaction energy consumption.

[0040] As a further technical solution, the hydrogenation reaction is carried out at a temperature of 150~250℃, a pressure of 1~5MPa, and a volume hourly space velocity of 500~4000mL·g. cat -1 ·h -1 .

[0041] As a further technical solution, the ester includes one of methyl acetate, ethyl acetate, and isopropyl acetate, preferably ethyl acetate.

[0042] As a further technical solution, the hydrogen-ester ratio of the ester to the hydrogen gas is 1:10~100.

[0043] The working principle and beneficial effects of this invention are as follows:

[0044] In this invention, the catalyst is a core-shell catalyst. The active component precursor, formed by combining water-soluble copper salt, water-soluble lanthanum salt, and water-soluble manganese salt, is coated on the core support of halloysite to form a shell structure coated with the catalytic active component. The resulting core-shell catalyst can be used in the reaction of ester hydrogenation to prepare ethanol, which can effectively improve the conversion rate of ester and the selectivity of ethanol. In core-shell catalysts, the core support is halloysite, which has the advantages of readily available raw materials, low cost, and stable chemical properties. Its high specific surface area not only disperses catalytic active sites but also provides a relatively stable catalytic environment for the catalytic active components. Water-soluble copper salts are the main precursors of the catalytic active components. The copper-based active components in the shell structure exhibit high selectivity for C=O bonds in ester groups and relative inertness towards C=C bonds, thus improving the selectivity of alcohol components and reducing side reactions. Furthermore, the introduction of manganese-based and lanthanum-based active components into the shell structure can, to some extent, hinder the aggregation and growth of copper-based active component particles, reducing the decrease in catalyst stability and catalytic activity caused by the migration and agglomeration of copper-based active components. In addition, the introduction of manganese-based and lanthanum-based active components increases the number of oxygen vacancies on the catalyst surface, which facilitates the adsorption of carbonyl groups in esters, thereby effectively improving the catalyst's stability and catalytic activity. Therefore, by using halloysite as the core support and coating its outer shell with catalytically active components, a core-shell catalyst is obtained. In the process of ester hydrogenation to ethanol, the catalytic activity is improved while the occurrence of side reactions is reduced, ultimately improving the conversion rate of ester feedstock and the selectivity of final ethanol. Detailed Implementation

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0046] In the following embodiments and comparative examples:

[0047] The average particle size of the catalyst is 30 mesh;

[0048] The purity of ethyl acetate is 99.8%;

[0049] The purity of the hydrogen gas is 99.99%.

[0050] Halloysite, with an average grain size of 325 mesh;

[0051] Aluminum acetylacetonate, CAS number 13963-57-0, purity 99%.

[0052] Example 1

[0053] The catalyst is a core-shell catalyst, and its preparation method includes the following steps:

[0054] A1. Dissolve 7.5g of copper nitrate, 1.25g of lanthanum nitrate hexahydrate, and 1.25g of manganese acetate tetrahydrate in 500g of water to obtain a mixed solution;

[0055] A2. Add 7.5g of ammonium nitrate to the above mixed solution, mix well, then add 13g of urea and 25g of halloysite, and carry out a hydrothermal reaction at 90℃ for 12h. After cooling, a precipitate is obtained. The precipitate is washed twice with deionized water and twice with anhydrous ethanol. Then it is dried at 70℃ for 8h, calcined at 400℃ for 3h, pulverized and shaped to obtain the catalyst.

[0056] The method for preparing ethanol includes the following steps:

[0057] Ethyl acetate with a hydrogen-to-ester ratio of 1:100 and hydrogen gas were mixed under 10g of the above catalyst at 150℃, 5MPa, and 500mL·g. cat -1 ·h -1 The hydrogenation reaction is carried out under volume hourly space velocity conditions to produce ethanol.

[0058] Example 2

[0059] The catalyst is a core-shell catalyst, and its preparation method includes the following steps:

[0060] A1. Dissolve 8g of copper nitrate, 1g of lanthanum nitrate hexahydrate, and 1g of manganese acetate tetrahydrate in 1000g of water to obtain a mixed solution;

[0061] A2. Add 10g of ammonium nitrate to the above mixed solution, mix well, add 16g of urea and 20g of halloysite, and carry out hydrothermal reaction at 120℃ for 4h. After cooling, a precipitate is obtained. The precipitate is washed twice with deionized water and twice with anhydrous ethanol. Then it is dried at 80℃ for 5h, calcined at 450℃ for 2h, crushed and shaped to obtain the catalyst.

[0062] The method for preparing ethanol includes the following steps:

[0063] Ethyl acetate with a hydrogen-to-ester ratio of 1:10 and hydrogen gas were mixed under 10 g of the above catalyst at 250 °C, 1 MPa, and 4000 mL·g. cat -1 ·h -1 The hydrogenation reaction is carried out under volume hourly space velocity conditions to produce ethanol.

[0064] Example 3

[0065] The only difference between this embodiment and Example 2 is that in the preparation method of the catalyst in this embodiment, 0.2g of lanthanum nitrate hexahydrate and 1.8g of manganese acetate tetrahydrate are added.

[0066] Example 4

[0067] The only difference between this embodiment and Example 2 is that in the preparation method of the catalyst in this embodiment, 0.5g of lanthanum nitrate hexahydrate and 1.5g of manganese acetate tetrahydrate are added.

[0068] Example 5

[0069] The only difference between this embodiment and Example 2 is that in the preparation method of the catalyst in this embodiment, 0.4g of lanthanum nitrate hexahydrate and 1.6g of manganese acetate tetrahydrate are added.

[0070] Example 6

[0071] The only difference between this embodiment and Example 5 is that the preparation method of the catalyst in this embodiment is different, specifically:

[0072] The catalyst is a core-shell catalyst, and its preparation method includes the following steps:

[0073] A0. Disperse 2g of aluminum acetylacetonate in a 75% ethanol solution, adjust the pH to 5 with a 15% nitric acid solution, add 20g of halloysite, stir at 300rpm for 40min at 40℃, concentrate, and dry to obtain modified halloysite.

[0074] A1. Dissolve 8g of copper nitrate, 0.4g of lanthanum nitrate hexahydrate, and 1.6g of manganese acetate tetrahydrate in 1000g of water to obtain a mixed solution;

[0075] A2. Add 10g of ammonium nitrate to the above mixed solution, mix well, then add 16g of urea and 20g of modified halloysite, and carry out a hydrothermal reaction at 120℃ for 4h. After cooling, a precipitate is obtained. The precipitate is washed twice with deionized water and twice with anhydrous ethanol. Then it is dried at 80℃ for 5h, calcined at 450℃ for 2h, pulverized, and shaped to obtain the catalyst.

[0076] Example 7

[0077] The only difference between this embodiment and Example 5 is that the preparation method of the catalyst in this embodiment is different, specifically:

[0078] The catalyst is a core-shell catalyst, and its preparation method includes the following steps:

[0079] A0. Disperse 2g of aluminum acetylacetonate in a 75% ethanol solution, adjust the pH to 6 with a 15% nitric acid solution, add 20g of halloysite, stir at 400rpm for 20min at 50℃, concentrate, and dry to obtain modified halloysite.

[0080] A1. Dissolve 8g of copper nitrate, 0.4g of lanthanum nitrate hexahydrate, and 1.6g of manganese acetate tetrahydrate in 1000g of water to obtain a mixed solution;

[0081] A2. Add 10g of ammonium nitrate to the above mixed solution, mix well, then add 16g of urea and 20g of modified halloysite, and carry out a hydrothermal reaction at 120℃ for 4h. After cooling, a precipitate is obtained. The precipitate is washed twice with deionized water and twice with anhydrous ethanol. Then it is dried at 80℃ for 5h, calcined at 450℃ for 2h, pulverized, and shaped to obtain the catalyst.

[0082] Example 8

[0083] The only difference between this embodiment and Example 7 is that in the preparation method of the catalyst in this embodiment, 3g of aluminum acetylacetonate is added.

[0084] Example 9

[0085] The only difference between this embodiment and Example 7 is that in the preparation method of the catalyst in this embodiment, 5g of aluminum acetylacetonate is added.

[0086] Example 10

[0087] The only difference between this embodiment and Example 7 is that in the preparation method of the catalyst in this embodiment, 7g of aluminum acetylacetonate is added.

[0088] Comparative Example 1

[0089] The only difference between this comparative example and Example 2 is that, in the preparation method of the catalyst in this comparative example, lanthanum nitrate hexahydrate is replaced with an equal amount of manganese acetate tetrahydrate.

[0090] Comparative Example 2

[0091] The only difference between this comparative example and Example 2 is that in the preparation method of the catalyst in this comparative example, manganese acetate tetrahydrate is replaced with an equal amount of lanthanum nitrate hexahydrate.

[0092] Comparative Example 3

[0093] The only difference between this comparative example and Example 2 is that in the preparation method of the catalyst in this comparative example, manganese acetate tetrahydrate and lanthanum nitrate hexahydrate are replaced with an equal amount of copper nitrate.

[0094] Comparative Example 4

[0095] The only difference between this comparative example and Example 2 is that the preparation method of the catalyst in this comparative example is different, specifically:

[0096] The catalyst is a core-shell catalyst, and its preparation method includes the following steps:

[0097] A1. Dissolve 8g of copper nitrate, 1g of lanthanum nitrate hexahydrate, and 1g of manganese acetate tetrahydrate in 1000g of water to obtain a mixed solution;

[0098] A2. Add 16g of sodium carbonate to the above mixed solution, adjust the pH to 9.0, and carry out a co-precipitation reaction at a stirring speed of 600rpm for 3h to obtain a precipitate. After aging the precipitate for 24h, wash it twice with deionized water and twice with anhydrous ethanol. Then dry it at 80℃ for 5h, calcine it at 450℃ for 2h, crush it, and shape it to obtain the catalyst.

[0099] Experimental Example

[0100] The catalytic performance of the catalysts prepared in Examples 1-10 and Comparative Examples 1-4 for the hydrogenation of esters to ethanol was evaluated. The reaction products were analyzed by gas chromatography, and the conversion rate of ethyl acetate and the selectivity of ethanol were calculated according to the following formulas: Ethyl acetate conversion rate = (moles of ethyl acetate feedstock - moles of ethyl acetate in the product) / moles of ethyl acetate feedstock × 100%; Ethanol selectivity = moles of ethanol in the product / (moles of ethyl acetate feedstock - moles of ethyl acetate in the product × 2) × 100%. The results are shown in Table 1.

[0101] Table 1. Ethyl acetate conversion and ethanol selectivity results for Examples 1-10 and Comparative Examples 1-4.

[0102]

[0103] As can be seen from Table 1, compared with Comparative Examples 1-4, using the catalysts prepared in Examples 1-10 in the hydrogenation of ethyl acetate to ethanol can improve the conversion rate of ethyl acetate feedstock and the selectivity of the target product ethanol. This indicates that when using ethyl acetate to prepare ethanol, the co-precipitation and coating of the shell active component precursors of water-soluble copper salt, water-soluble lanthanum salt, and water-soluble manganese salt on the halloysite core support to form catalytic active components ultimately forms a core-shell catalyst with good stability and catalytic activity. When used in the hydrogenation of ester to prepare ethanol, it can effectively improve the conversion rate of ethyl acetate and the selectivity of ethanol. The conversion rate of ethyl acetate reaches more than 98.5%, and the selectivity of ethanol reaches more than 99.2%.

[0104] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A catalyst, characterized in that, The catalyst is a core-shell catalyst, and the raw materials for the core-shell catalyst include a core support and a shell active component precursor. The shell active component precursor includes water-soluble copper salt, water-soluble lanthanum salt, and water-soluble manganese salt; The core carrier includes halloysite; The weight ratio of the water-soluble lanthanum salt, the water-soluble manganese salt, and the water-soluble copper salt is 1:3~4. The weight ratio of the water-soluble manganese salt to the water-soluble lanthanum salt is 3~4:1; The halloysite is a modified halloysite, and the raw materials for the modified halloysite include halloysite and aluminum acetylacetone in a weight ratio of 20:2~7.

2. The catalyst according to claim 1, characterized in that, The water-soluble copper salt includes one or more of copper nitrate, copper acetate, and copper sulfate; The water-soluble lanthanum salt includes one or more of lanthanum chloride, lanthanum nitrate hexahydrate, and lanthanum acetate; The water-soluble manganese salt includes one or more of manganese acetate tetrahydrate, manganese nitrate, and manganese chloride tetrahydrate.

3. The catalyst according to claim 1, characterized in that, The method for preparing the modified halloysite includes the following steps: The aluminum acetylacetone was dispersed in an ethanol solution, the pH was adjusted to 5-6, halloysite was added and mixed, concentrated and dried to obtain the modified halloysite.

4. The catalyst according to claim 3, characterized in that, During the mixing process, the stirring speed is 300~400 rpm, the temperature is 40~50℃, and the time is 20~40 min.

5. The application of a catalyst according to any one of claims 1 to 4 in the hydrogenation of esters to prepare ethanol.

6. The application according to claim 5, characterized in that, The method for preparing ethanol includes the following steps: The ester and hydrogen are hydrogenated under the catalyst to obtain the ethanol.

7. The application according to claim 6, characterized in that, The hydrogenation reaction is carried out at a temperature of 150–250 °C, a pressure of 1–5 MPa, and a volume hourly space velocity of 500–4000 mL·g. cat -1 ·h -1 .

8. The application according to claim 6, characterized in that, The ester includes one of methyl acetate, ethyl acetate, and isopropyl acetate.

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