Zirconium-based attapulgite composite solid acid catalyst for accelerating ripening of white spirit and preparation method of zirconium-based attapulgite composite solid acid catalyst

Abstract

The invention discloses a zirconium-based attapulgite composite solid acid catalyst for accelerating ripening of white spirit and a preparation method of the zirconium-based attapulgite composite solid acid catalyst, and belongs to the technical field of white spirit catalytic aging. The preparation method comprises the following steps: dispersing attapulgite powder in a zirconium salt solution, adding an agriophyllum squarrosum extract solution to assist precipitation, aging, washing and drying to obtain a precursor; and dipping with a sulfuric acid or ammonium sulfate solution, and finally roasting at a high temperature to prepare the SO4 < 2-> / ZrO2 / attapulgite composite solid acid catalyst. The catalyst has both Bronsted acid and Lewis acid sites, and is large in specific surface area and high in acid content. When being applied to the ripening acceleration of the white spirit, the solid acid site can efficiently catalyze the alcohol acid esterification reaction and promote the generation of beneficial esters, and the adsorption performance of the attapulgite can be utilized to remove irritant substances such as acetaldehyde and the like, so that the synergism of'catalytic aroma production 'and'adsorption impurity removal' is realized, the aging period of the white spirit is remarkably shortened, and the flavor of a white spirit body is improved. The method is simple in process, green and safe, and the catalyst is easy to separate and can be repeatedly used.

Description

Technical Field

[0001] This invention belongs to the field of catalytic aging technology of baijiu (Chinese liquor), specifically relating to a zircon-based attapulgite composite solid acid catalyst for baijiu aging and its preparation method, and particularly to a green composite catalyst with dual functions of adsorption and impurity removal and catalytic aroma generation, which is suitable for the green aging process of baijiu industrialization. Background Technology

[0002] The traditional aging process of Chinese baijiu primarily relies on long-term storage in earthenware jars, using slow physicochemical changes such as oxidation, esterification, and molecular association to improve the flavor of the liquor. This process typically takes several years, consuming significant storage space and capital costs, and is difficult to meet the demands of modern markets for production efficiency and stability. To shorten the aging cycle, existing technologies mainly employ two methods: physical aging and chemical aging. Brewing Technology, 2025, (09): 102-106+ 118. Physical ripening methods, including treatments such as ultrasound, microwaves, and electric fields, can accelerate molecular motion and reactions to some extent, but they usually rely on specialized equipment, consume a lot of energy, and have unstable effects, easily leading to an imbalance of flavor components in the wine, or even over-ripening or flavor distortion. Chemical ripening methods mainly include adsorbent treatment and catalyst addition (…). Food Science Journal of ... Among these methods, adsorbents such as activated carbon, zeolite, and natural clay selectively remove off-flavor substances like hydrogen sulfide and acrolein from new wine primarily through physical adsorption. However, their catalytic ability to promote the formation of beneficial flavor compounds is weak, making it impossible to achieve catalytic aroma development. On the other hand, while liquid acid catalysts can promote esterification reactions, they pose safety and process risks, such as difficulty in completely separating them from the wine, potential equipment corrosion, and residual harmful ions, thus failing to meet food safety production requirements.

[0003] Attapulgite, as a natural mineral material, possesses a large specific surface area and excellent adsorption properties, effectively adsorbing some irritating small-molecule impurities in new liquor. However, its surface acidity site density is low, and its catalytic activity is limited, making it insufficient for driving the key chemical reaction of "acid + alcohol → ester" in the aging of baijiu. Its aging effect is relatively singular and cannot fully simulate the natural aging path. Zirconia (ZrO2) is a solid acid material with good surface acidity, thermal stability, and environmental friendliness, and is widely used in the field of catalysis. However, pure zirconium oxide powder is prone to agglomeration and poor dispersibility in liquid systems, and is difficult to recover and has high usage costs, limiting its direct application in the aging of baijiu.

[0004] Therefore, combining the excellent adsorption properties of attapulgite with the high catalytic activity of zirconium oxide to construct a composite catalyst that has both adsorption and impurity removal and catalytic aroma generation functions, and makes it environmentally friendly, easy to separate, and cost-controllable, has become a key technological requirement for promoting the green and efficient development of the liquor industry, and has important practical significance. Summary of the Invention

[0005] This invention aims to provide a zircon-based attapulgite composite solid acid catalyst with strong acidity and good stability, suitable for the aging of baijiu (Chinese liquor), and its green and simple preparation method. Another objective of this invention is to provide the application of this catalyst in the aging of baijiu.

[0006] To achieve the above objectives, the present invention employs the following technical means: I. Preparation of Zirconium-based Attapulgite Composite Solid Acid Catalysts A method for preparing a zirconium-based attapulgite composite solid acid catalyst for accelerating the maturation of baijiu (Chinese liquor) includes the following steps: (1) Preparation of precursor: Add attapulgite powder to zirconium salt solution and stir at room temperature for 1 to 5 hours to allow the silanol groups on the surface of attapulgite to fully react with zirconium ions; then add sand pine extract solution, adjust the pH of the system to 4 to 8 with ammonia or sodium hydroxide solution, react at constant temperature for 1 to 4 hours, let stand at room temperature for 6 to 24 hours, centrifuge, wash with deionized water until neutral, and dry at 100 to 110℃ for 4 to 8 hours to obtain the precursor; wherein, the mass ratio of attapulgite to zirconium is 1:0.1 to 1:0.6; The zirconium salt is at least one of zirconium oxychloride, zirconium oxynitrate and zirconium oxyacetate. The zirconium element concentration in the zirconium salt solution is 0.01~5 mol / L. Selecting this type of zirconium salt can ensure that zirconium ions exist stably in the solution and can form a stable bond with the attapulgite carrier after hydrolysis. The preparation method of the *Polygonum cuspidatum* extract solution is as follows: *Polygonum cuspidatum* extract is dissolved in water at a solid-liquid ratio of 1:50 to 1:500; the mass ratio of *Polygonum cuspidatum* extract to attapulgite powder is 1:5 to 1:50. The *Polygonum cuspidatum* extract is prepared according to patent CN202411293564.9. The plant active ingredients in the *Polygonum cuspidatum* extract can effectively inhibit the aggregation of zirconium oxide particles and promote the formation of nano-sized ZrO2.

[0007] (2) Sulfonation treatment: Using a sulfuric acid or ammonium sulfate solution with a concentration of 0.1~1.0 mol / L as the sulfonating agent, the above precursor is impregnated for 1~3 hours to ensure SO4 2- It fully combines with the zircon species in the precursor, and after impregnation, it is centrifuged and dried. (3) Calcination and shaping: The sulfonated and dried material is placed in a muffle furnace and heated to 350-550°C at a rate of 5-10°C / min for 1-5 hours to obtain SO4. 2- / ZrO2 / attapulgite composite solid acid catalyst.

[0008] This invention also provides a zircon-based attapulgite composite solid acid catalyst for aging baijiu (Chinese liquor) prepared by the above method. This catalyst uses attapulgite as a support, and the surface of the support is loaded with SO4 in a nanoscale dispersed state. 2- The ZrO2 active phase exhibits no obvious aggregation and possesses both Brønsted and Lewis acid sites. Its acidity ranges from 0.8 to 1.35 mmol / g, and its specific surface area is 100 to 122 m² / g. It combines excellent catalytic activity with adsorption performance.

[0009] This invention also provides the application of the above-mentioned composite solid acid catalyst in the aging of baijiu, specifically: the catalyst is added to the new baijiu at 0.5‰~2% of the baijiu mass, and the baijiu is left to stand at room temperature for 30~180 days. No additional external force is required to achieve rapid aging of the baijiu.

[0010] The synthesis mechanism and synergistic working mechanism of the catalyst of this invention are as follows: Synthesis Mechanism: The abundant silanol groups (-Si-OH) on the surface of attapulgite act as anchoring sites, adsorbing zirconium ions (Zr) through electrostatic attraction and coordination. 4 ⁺), achieving initial fixation of active components; the extract of *Polygonum cuspidatum* contains abundant flavonoids, alkaloids, and saponins, which play a role in dispersion and stabilization. In the co-precipitation environment after pH adjustment, Zr 4 ⁺In-situ hydrolysis generates amorphous zirconium hydroxide (Zr(OH)4), which is tightly loaded onto the surface of attapulgite to form a stable precursor; after sulfonation treatment, SO4 2- The precursor forms coordination bonds with zirconium species, and then undergoes dehydration and phase transformation through high-temperature calcination, generating highly dispersed nanoscale ZrO2 crystals, which ultimately form SO4. 2- The ZrO2 / attapulgite composite structure effectively avoids ZrO2 particle agglomeration, ensuring the high dispersion and stable existence of active centers, thereby endowing the catalyst with abundant Brønsted acid and Lewis acid sites.

[0011] Synergistic ripening mechanism: The catalyst plays a synergistic role of "adsorption-catalysis" in the baijiu system: On the one hand, SO4 2-The Brønsted acid and Lewis acid sites in the ZrO2 active phase synergistically catalyze the esterification reaction of alcohols and acids, promoting the formation of key flavor esters such as ethyl acetate and ethyl hexanoate, thus achieving catalytic aroma enhancement. On the other hand, the large specific surface area and pore structure of the attapulgite carrier can selectively adsorb irritating impurities such as acetaldehyde and sulfides, and the adsorbed impurities can be transformed under the action of acid sites, further reducing the irritation of the wine. The two work together to accelerate the aging process of the wine and improve the flavor harmony and purity.

[0012] Compared with the prior art, the present invention has the following significant advantages: 1. Dual-function synergy for highly efficient ripening: For the first time, the solid acid catalytic properties of zirconium oxide are combined with the nanocarrier and adsorption properties of attapulgite through a specific plant-mediated synthesis and sulfonation process to successfully construct SO4 with ultra-strong acidity. 2- The ZrO2 active phase is highly dispersed on the attapulgite support. This structure provides abundant Brønsted and Lewis acid sites, achieving synergistic catalysis of the bifunctional acid centers. It can efficiently catalyze the esterification reaction of alcohols and esters to "catalyze aroma generation" and also rely on the adsorption properties of attapulgite to "adsorb and remove impurities." The two work together to fully simulate and accelerate the natural aging process, significantly improving the flavor harmony and purity of the wine.

[0013] 2. Stable structure and good dispersibility: By utilizing the precipitation aided by plant extracts and the confinement effect of attapulgite as a carrier, the aggregation of zirconium oxide nanoparticles is effectively prevented, ensuring the high dispersion and stable existence of the active centers, thereby obtaining a catalyst with high acidity and large specific surface area.

[0014] 3. Significant effect: This catalyst can significantly shorten the aging cycle of baijiu, reducing the traditional aging time of several years to 30-180 days, while reducing the loss of flavor esters. Tests have shown that the relative content of major flavor esters in the treated baijiu is significantly higher than that of the blank control group, and the content of irritating substances is significantly reduced.

[0015] 4. Green, safe and easy to separate: The catalyst is a solid particle that can be quickly separated from the wine through filtration. The amount of harmful substances leached is extremely low, which meets the requirements for food safety production. The preparation process uses natural minerals and plant extracts, which is clean and environmentally friendly, with no harmful waste emissions. The catalyst can be reused 3 to 5 times while maintaining high activity.

[0016] 5. Great industrialization potential: The raw material attapulgite is widely available and inexpensive. The preparation process is simple and the conditions are mild. No complicated equipment is required. The roasting temperature and time are controllable, making it easy to scale up production. It can effectively reduce the storage and time costs of liquor production, resulting in significant economic and social benefits. Attached Figure Description

[0017] Figure 1TEM characterization image of the catalyst prepared in Example 1 of this invention.

[0018] Figure 2 Comparison of ester content in the catalyst prepared in Example 1 of this invention for the aging of baijiu. Detailed Implementation

[0019] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] Example 1 (1) Preparation of precursor: Weigh 10.0 g of attapulgite powder and add it to a zirconium chloride solution containing 1.0 g of zirconium (zirconium concentration 0.05 mol / L, mass ratio of attapulgite to zirconium 1:0.1), stir at room temperature for 1.5 hours; add a solution of semperflorens extract (solid-liquid ratio 1:500) prepared by dissolving 0.2 g of semperflorens extract in 100 mL of deionized water, adjust the pH of the system to 4 with ammonia, react at constant temperature for 2 hours, and then age at room temperature for 8 hours; centrifuge, wash with deionized water until the filtrate is neutral, and dry at 105℃ for 6 hours to obtain the precursor; (2) Sulfonation treatment: The precursor was immersed in 0.3 mol / L ammonium sulfate solution for 2 hours at room temperature. After immersion, it was centrifuged and dried at 105℃ for 4 hours. (3) Calcination and molding: The sulfonated and dried material is placed in a muffle furnace and heated to 400°C at a rate of 8°C / min. After calcination for 3 hours, it is naturally cooled to room temperature and then ground through a 100-mesh sieve to obtain catalyst A-1.

[0021] The catalyst A-1 was determined to have an acidity of 0.8 mmol / g and a specific surface area of ​​102 m² / g; TEM characterization showed that ZrO2 nanoparticles were uniformly loaded on the surface of attapulgite. Figure 1 ).

[0022] Example 2 (1) Preparation of precursor: Weigh 10.0 g of attapulgite powder and add it to a zirconium nitrate solution containing 3.0 g of zirconium (zirconium concentration 0.1 mol / L, mass ratio of attapulgite to zirconium 1:0.3), stir at room temperature for 3 hours; add a solution of 1.0 g of *Polygonum cuspidatum* extract (solid-liquid ratio 1:300) prepared by dissolving 1.0 g of *Polygonum cuspidatum* extract in 300 mL of deionized water, adjust the pH of the system to 5 with sodium hydroxide solution, react at constant temperature for 3 hours, and then age at room temperature for 12 hours; centrifuge, wash with deionized water until neutral, and dry at 100°C for 8 hours to obtain the precursor; (2) Sulfonation treatment: The precursor was immersed in 0.5 mol / L sulfuric acid solution for 1.5 hours at room temperature. After immersion, it was centrifuged and dried at 100°C for 5 hours. (3) Calcination and shaping: The sulfonated and dried material was placed in a muffle furnace and heated to 450°C at a rate of 5°C / min. After calcination for 2 hours, it was naturally cooled to room temperature and then ground through an 80-mesh sieve to obtain catalyst A-2. The acid content of catalyst A-2 was determined to be 1.04 mmol / g and the specific surface area was 115 m² / g.

[0023] Example 3: (1) Preparation of precursor: Weigh 10.0 g of attapulgite powder and add it to a zirconium acetate solution containing 6.0 g of zirconium (zirconium concentration 0.15 mol / L, mass ratio of attapulgite to zirconium 1:0.6), stir at room temperature for 4 hours; add a solution of 2.0 g of *Polygonum cuspidatum* extract (solid-liquid ratio 1:200) prepared by dissolving 2.0 g of *Polygonum cuspidatum* extract in 400 mL of deionized water, adjust the pH of the system to 6 with ammonia, react at constant temperature for 4 hours, and then age at room temperature for 18 hours; centrifuge, wash with deionized water until neutral, and dry at 110°C for 4 hours to obtain the precursor; (2) Sulfonation treatment: The precursor was immersed in 1.0 mol / L ammonium sulfate solution for 1 hour at room temperature. After immersion, it was centrifuged and dried at 110°C for 3 hours. (3) Calcination and shaping: The sulfonated and dried material was placed in a muffle furnace and heated to 500°C at a rate of 10°C / min. After calcination for 2.5 hours, it was naturally cooled to room temperature and then ground through a 100-mesh sieve to obtain catalyst A-3. The acidity of catalyst A-3 was determined to be 1.28 mmol / g and the specific surface area was 100 m² / g.

[0024] Example 4: (1) Preparation of precursor: Weigh 10.0 g of attapulgite powder and add it to a zirconium chloride solution containing 2.0 g of zirconium (zirconium concentration 0.08 mol / L, mass ratio of attapulgite to zirconium 1:0.2), stir at room temperature for 2 hours; add a solution of 0.8 g of *Polygonum cuspidatum* extract (solid-liquid ratio 1:250) prepared by dissolving 0.8 g of *Polygonum cuspidatum* extract in 200 mL of deionized water, adjust the pH of the system to 7 with ammonia, react at constant temperature for 1 hour, and then age at room temperature for 6 hours; centrifuge, wash with deionized water until neutral, and dry at 105°C for 5 hours to obtain the precursor; (2) Sulfonation treatment: The precursor was immersed in 0.1 mol / L sulfuric acid solution for 3 hours at room temperature. After immersion, it was centrifuged and dried at 105°C for 4 hours. (3) Calcination and shaping: The sulfonated and dried material was placed in a muffle furnace and heated to 350°C at a rate of 7°C / min. After calcination for 4 hours, it was naturally cooled to room temperature and then ground through a 100-mesh sieve to obtain catalyst A-4. The acid content of catalyst A-4 was determined to be 1.22 mmol / g and the specific surface area was 115 m² / g.

[0025] Example 5: (1) Preparation of precursor: Weigh 10.0 g of attapulgite powder and add it to a mixed solution of zirconium oxychloride and zirconium oxynitrate containing 4.0 g of zirconium (zirconium concentration 0.12 mol / L, mass ratio of attapulgite to zirconium 1:0.4), stir at room temperature for 5 hours; add a solution of semperflorens extract (solid-liquid ratio 1:233) prepared by dissolving 1.5 g of semperflorens extract in 350 mL of deionized water, adjust the pH of the system to 8 with sodium hydroxide solution, react at constant temperature for 3 hours, and then age at room temperature for 24 hours; centrifuge, wash with deionized water until neutral, and dry at 105°C for 6 hours to obtain the precursor; (2) Sulfonation treatment: The precursor was immersed in 0.8 mol / L ammonium sulfate solution for 2 hours at room temperature. After immersion, it was centrifuged and dried at 105°C for 4 hours. (3) Calcination and shaping: The sulfonated and dried material was placed in a muffle furnace and heated to 550°C at a rate of 9°C / min. After calcination for 1 hour, it was naturally cooled to room temperature and then ground through a 100-mesh sieve to obtain catalyst A-5. The acidity of catalyst A-5 was determined to be 1.35 mmol / g and the specific surface area was 122 m² / g.

[0026] Evaluation of the ripening effect of baijiu: Freshly brewed strong-aroma baijiu (Chinese white liquor) from the same batch was divided into multiple ceramic jars. Experimental group: Catalyst A-1 prepared in Example 1 was added to the jars at a rate of 0.5% of the liquor's mass. Blank control group: No catalyst or adsorbent was added to the jars. The jars were sealed and stored naturally in a cool, dark warehouse for 90 days. After storage, the supernatant was collected and filtered through a 0.22 μm microporous membrane to thoroughly remove catalyst particles.

[0027] Seven major esters in the wine sample were quantitatively analyzed using gas chromatography-mass spectrometry (GC-MS). The results are as follows: Figure 2 As shown, compared to untreated new wine (initial value), after 90 days of storage, the content of all tested esters in the blank control group decreased to varying degrees. This is a normal phenomenon during the natural aging process, involving ester hydrolysis and volatilization. However, compared to the blank control group, the experimental group with added catalyst A-1 showed a significantly smaller decrease in the content of various esters and a higher relative retention rate. This indicates that the catalyst of this invention effectively promotes the equilibrium of esterification reactions in the wine, inhibits excessive hydrolysis and loss of esters, and thus better preserves the flavor structure of the baijiu within a shorter storage time, achieving the effect of accelerating maturation and improving quality.

Claims

1. A method for preparing a zirconium-based attapulgite composite solid acid catalyst for accelerating the maturation of baijiu (Chinese liquor), characterized in that, Includes the following steps: (1) Add attapulgite powder to zircon salt solution, stir, add sand pine extract solution, adjust pH to 4-8, react for 1-4 hours, let stand for 6-24 hours, centrifuge, wash and dry to obtain precursor; (2) The precursor is impregnated with sulfuric acid or ammonium sulfate solution to make SO4 2- Combined with zirconium species; (3) The impregnated material is roasted at 350~550℃ for 1~5 hours to obtain SO4. 2- / ZrO2 / attapulgite composite solid acid catalyst.

2. The preparation method according to claim 1, characterized in that, In step (1), the zirconium salt is at least one of zirconium oxychloride, zirconium oxynitrate, and zirconium oxyacetate; the concentration of zirconium in the zirconium salt solution is 0.01~5 mol / L.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of attapulgite powder to zirconium is 1:0.1 to 1:0.

6.

4. The preparation method according to claim 1, characterized in that, In step (1), the preparation method of the *Polygonum cuspidatum* extract solution is as follows: *Polygonum cuspidatum* extract is added to water at a solid-liquid ratio of 1:50 to 1:500 and dissolved to obtain the solution.

5. The preparation method according to claim 1, characterized in that, In step (1), the stirring time is 1 to 5 hours; the pH value of the system is adjusted by using ammonia or sodium hydroxide solution.

6. The preparation method according to claim 1, characterized in that, In step (2), the concentration of the sulfuric acid or ammonium sulfate solution is 0.1~1.0 mol / L; the immersion treatment time is 1~3 hours.

7. A zirconium-based attapulgite composite solid acid catalyst for accelerating the maturation of baijiu (Chinese liquor) prepared by the method according to any one of claims 1-6, characterized in that, Attapulgite was used as a carrier, and SO4 was loaded on the surface of the carrier. 2- / ZrO2 active phase, wherein the active phase is in a nanoscale dispersion state and has both Brønsted acid sites and Lewis acid sites.

8. The catalyst according to claim 7, characterized in that, The catalyst has an acidity of not less than 0.8 mmol / g and a specific surface area of ​​not less than 100 m² / g.

9. The application of the composite solid acid catalyst according to claim 7 in the aging process of baijiu (Chinese liquor).

10. The application according to claim 9, characterized in that, Add the catalyst to the new liquor at 0.5‰~2% of the liquor's mass and let it stand at room temperature for 30~180 days.

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