Preparation process of high-acidity low-tar refined bamboo vinegar

Abstract

The invention relates to a preparation process of high-acidity low-tar refined bamboo vinegar. The invention discloses a bamboo vinegar refining process, which comprises the following steps: adding 3-8% of sodium chloride into a bamboo vinegar stock solution, salting out for 48 hours, filtering, and carrying out reduced pressure distillation at 75 DEG C and-0.06 Mpa, so that the pH value (less than or equal to 3) of the stock solution and the organic acid content (more than or equal to 95%) are remarkably reserved, and meanwhile, the tar content is reduced to 0.1% or below. The process solves the problems of large loss of active ingredients and high tar residue in the traditional distillation method, and is suitable for industrial production of the high-acidity low-tar refined bamboo vinegar.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomass separation and purification by pyrolysis of bamboo, and specifically relates to a preparation process of refined bamboo vinegar liquid with high acidity and low tar. Background Art

[0002] Bamboo vinegar liquid is an acidic liquid by-product generated during the pyrolysis of bamboo, rich in organic components such as aldehydes, phenols, alcohols, and ketones, and is widely used in the fields of food, medicine, and agriculture. Its original liquid contains harmful substances such as formaldehyde, methanol, heterocyclics, and tar, and it is necessary to remove impurities and retain active ingredients through a refining and purification process to finally prepare a product that is clear, transparent, low in tar, and has stable active ingredients. Traditional refining methods (such as direct distillation) have the following defects: Loss of active ingredients: High-temperature distillation causes the volatilization of organic acids, the pH value rises (usually above 3.5), and the content of organic acids drops below 3%. High tar residue: It is difficult to effectively separate tar by direct distillation, and the tar content is often higher than 0.5%, affecting the stability and application effect of the product. There are many studies and related patents on the refining method of bamboo vinegar liquid. Patent CN1397534A proposes a method for purifying bamboo vinegar liquid, which simply distills the bamboo vinegar liquid at 100-150°C and then stores it for several months. The disadvantage of this method is that a large amount of organic acids are lost due to high temperature, and the pH value rises. It is difficult to effectively remove tar by direct distillation, and the tar content is relatively high, affecting the stability and application effect of the product. The color is usually reddish-brown. Patent CN1931960A obtains light yellow refined bamboo vinegar liquid through activated carbon and resin adsorption method, but the resin dosage is large (about 20% of the weight of bamboo vinegar liquid), and a large amount of acid-base solution is required for resin regeneration, the operation is complex, and the tar content of the obtained bamboo vinegar liquid is still relatively high. Patent CN104164248A and Patent CN115125024A use the method of activated carbon adsorption combined with supercritical CO2 extraction to obtain high-purity bamboo vinegar liquid, but the preparation of supercritical CO2 is relatively complex and the cost is relatively high. Patent CN117903832A prevents bamboo vinegar liquid from turning yellow by adding stabilizers (ascorbic acid, sodium metabisulfite, sodium sulfite), but the inclusion of sodium sulfite is not conducive to the application of bamboo vinegar liquid in the fields of medicine and food to a certain extent. At the same time, it has been verified that antioxidants cannot completely prevent the discoloration reaction of bamboo vinegar liquid. Patent CN104232137A discloses a method for preparing food-grade bamboo vinegar liquid through static purification and multi-stage distillation. The bamboo vinegar liquid product obtained by this method has high purity and small property changes. However, the repeated distillation process not only consumes a large amount of energy, has a long production cycle, but also has a high equipment cost. Patent CN103980927A and CN1616600A respectively use ozone and hydrogen peroxide oxidation methods to treat bamboo vinegar liquid. This method can effectively remove polycyclic aromatic substances and part of the dissolved tar, significantly improving the purity of the vinegar liquid. However, the chemical method introduces other chemical substances and makes the composition of bamboo vinegar liquid change unpredictably, thereby reducing the safety and greenness of the vinegar liquid product. Summary of the Invention

[0003] The object of the present invention is to address the problems existing in the existing purification and refinement methods, such as high energy consumption, long process cycle, complex operation, large loss of organic acids, and high tar content. The present invention provides a preparation process for refined bamboo vinegar liquid, which reduces the solubility of harmful components such as tar through salting-out method, promotes the distillation of organic acids by utilizing the characteristic of the boiling point elevation of salt solution, and combines with vacuum distillation process to maintain the pH value and organic acid content of bamboo vinegar liquid while removing impurities and significantly reducing tar residue.

[0004] The technical solution of the present invention is a refinement process for bamboo vinegar liquid, which comprises the following steps:

[0005] Salting-out pretreatment: Add 3 - 8% sodium chloride (NaCl) to the original bamboo vinegar liquid, and use the salting-out effect to precipitate macromolecular impurities (such as colloid and tar precursors), and let it stand for 48 hours.

[0006] Filtration to remove impurities: Separate the precipitate after salting-out to obtain a clear filtrate.

[0007] Vacuum distillation: Perform vacuum distillation on the filtrate at 75°C, collect the condensed solution, and finally obtain refined bamboo vinegar liquid.

[0008] This process realizes purification through physical separation methods, completely retains the active components such as organic acids and phenols in the bamboo vinegar liquid, and at the same time removes macromolecular impurities such as tar.

[0009] Technical advantages: This process is applicable to the large-scale production of bamboo vinegar liquid.

[0010] Application fields: The refined bamboo vinegar liquid can be directly used as fine chemical raw materials for organic fertilizers, fungicides or cosmetics.

[0011] Data support: The comparison of data between the examples and the comparative examples is clear, verifying the significant progressiveness of the present invention. Brief Description of the Drawings

[0012] Figure 1 It is the process flow chart of the present invention. Detailed Description of the Invention

[0013] The present invention will be further described below in conjunction with specific embodiments.

[0014] Example 1:

[0015] (1) A preparation process for high-acidity and low-tar refined bamboo vinegar liquid, which comprises the following preparation steps:

[0016] Raw material preparation: Take 1L of original bamboo vinegar liquid (pH value 2.7, organic acid content 13.2%, tar content 0.6%)

[0017] Salting-out treatment: Add 50 g of NaCl, stir until completely dissolved, and let stand for 48 hours.

[0018] Filtration: Filter by suction using ordinary fast filter paper to remove the precipitates.

[0019] Vacuum distillation: Place the filtrate in a vacuum distillation apparatus and distill at 75 °C and -0.06 Mpa until the volume is reduced to 1 / 5 of the original volume. (2) Comparative example (activated carbon adsorption method):

[0020] Add activated carbon to adsorb the same bamboo vinegar stock solution, let stand for 20 min, and then filter through a plate and frame filter.

[0021] (3) Test results:

[0022] Test Items Raw Bamboo Vinegar Salting Out - Vacuum Distillation Method Activated Carbon Adsorption Method pH Value 2.7 2.7 2.8 Organic Acid Content 13.2％ 13.2％ 12.8％ Tar Content 0.6％ 0.06％ 0.3％

[0023] Example 2

[0024] (1) A preparation process for high-acidity and low-tar refined bamboo vinegar liquid, including the following preparation steps:

[0025] Raw material preparation: Take 1 L of bamboo vinegar stock solution (pH value 2.7, organic acid content 13.2%, tar content 0.6%)

[0026] Salting-out treatment: Add 50 g of NaCl, stir until completely dissolved, and let stand for 48 hours.

[0027] Filtration: Filter by suction using ordinary fast filter paper to remove the precipitates.

[0028] Vacuum distillation: Place the filtrate in a vacuum distillation apparatus and distill at 75 °C and -0.06 Mpa until the volume is reduced to 1 / 5 of the original volume. (2) Comparative example (activated carbon-ion exchange resin method)

[0029] Add 1% by weight of activated carbon to adsorb the same bamboo vinegar stock solution, stir for 1 hour, let stand for several hours, filter through a plate and frame filter, and then separate and purify with 20% by weight of D208 ion exchange resin.

[0030] (3) Test results:

[0031] Test Items Raw Bamboo Vinegar Salting Out - Vacuum Distillation Method Activated Carbon - Ion Exchange Resin Method pH Value 2.7 2.7 3.1 Organic Acid Content 13.2％ 13.2％ 10.5％ Tar Content 0.6％ 0.06％ 0.11％

[0032] Example 3

[0033] (1) A preparation process for high-acidity and low-tar refined bamboo vinegar liquid, including the following preparation steps:

[0034] Raw material preparation: Take 1 L of bamboo vinegar stock solution (pH value 2.7, organic acid content 13.2%, tar content 0.6%)

[0035] Salting-out treatment: Add 50 g of NaCl, stir until completely dissolved, and let stand for 48 hours.

[0036] Filtration: Filter by suction using ordinary fast filter paper to remove the precipitates.

[0037] Vacuum distillation: Place the filtrate in a vacuum distillation apparatus and distill at 75 °C and -0.06 Mpa until the volume is reduced to 1 / 5 of the original volume. (2) Comparative example (atmospheric distillation method):

[0038] Directly perform atmospheric distillation on the same original bamboo vinegar solution at 100 °C.

[0039] (3) Test results:

[0040] Test Items Raw Bamboo Vinegar Salting Out - Vacuum Distillation Method Atmospheric Distillation pH Value 2.7 2.7 3.5 Organic Acid Content 13.2％ 13.2％ 7.53％ Tar Content 0.6％ 0.06％ 0.12％

[0041] Example 4

[0042] (1) A preparation process for highly acidic and low-tar refined bamboo vinegar liquid, comprising the following preparation steps:

[0043] Raw material preparation: Take 1 L of original bamboo vinegar solution (pH value 2.7, organic acid content 13.2%, tar content 0.6%)

[0044] Salting-out treatment: Add 50 g of NaCl, stir until completely dissolved, and let stand for 48 hours.

[0045] Filtration: Filter by suction using ordinary fast filter paper to remove the precipitates.

[0046] Vacuum distillation: Place the filtrate in a vacuum distillation apparatus and distill at 75 °C and -0.06 Mpa until the volume is reduced to 1 / 5 of the original volume. (2) Comparative example (vacuum distillation without salting):

[0047] For the same original bamboo vinegar solution, without salting-out treatment, directly filter and then place it in a vacuum distillation apparatus, and distill at 75 °C and -0.06 Mpa until the volume is reduced to 1 / 5 of the original volume.

[0048] (3) Test results:

[0049] Test Items Raw Bamboo Vinegar Salting Out - Vacuum Distillation Method Salt - Free Vacuum Distillation pH Value 2.7 2.7 3.0 Organic Acid Content 13.2％ 13.2％ 9.2％ Tar Content 0.6％ 0.06％ 0.08％

[0050] Example 5:

[0051] (1) A preparation process for highly acidic and low-tar refined bamboo vinegar liquid, comprising the following preparation steps:

[0052] Raw material preparation: Take 1 L of original bamboo vinegar solution (pH value 2.7, organic acid content 13.2%, tar content 0.6%)

[0053] Salting-out treatment: Add 50 g of NaCl, stir until completely dissolved, and let stand for 48 hours.

[0054] Filtration: Filter by suction using ordinary fast filter paper to remove the precipitates.

[0055] Vacuum distillation: The filtrate was placed in a vacuum distillation apparatus and distilled at 75 °C and -0.06 Mpa until it reached 1 / 5 of the original volume. (2) Comparative example (hydrogen peroxide-vacuum distillation method):

[0056] The same volume of bamboo vinegar stock solution was added with 3% hydrogen peroxide by volume fraction, stirred for 1 hour, allowed to stand for 2 hours, and the solution was pumped into a vacuum distillation apparatus and distilled at 75 °C and -0.06 Mpa until it reached 1 / 5 of the original volume.

[0057] (3) Test results:

[0058] Test Items Raw Bamboo Vinegar Salting Out - Vacuum Distillation Method Hydrogen Peroxide - Vacuum Distillation Method pH Value 2.7 2.7 2.9 Organic Acid Content 13.2％ 13.2％ 8.8％ Tar Content 0.6％ 0.06％ 0.08％

[0059] Technical effects of the present invention:

[0060] pH value retention: The pH value of the refined liquid was stable below 3 (the pH value range of the bamboo vinegar stock solution was 2.5 - 3.0).

[0061] High retention of organic acids: The content of organic acids was retained above 95%, significantly higher than methods such as direct distillation (the retention of organic acids was 60 - 80%).

[0062] Low residual tar: The tar content was ≤0.1%, meeting the requirements of high-end applications.

[0063] Synergy of salting out and vacuum distillation: The boiling point of the distillate was increased by salting out pretreatment, and high-temperature destruction of active ingredients was avoided by vacuum distillation.

[0064] Optimization of process parameters: The key control points were a salting out standing time of 48 hours, a vacuum distillation temperature of 75 °C, and -0.06 Mpa, ensuring efficient separation and ingredient retention.

Claims

1. A refined process for bamboo vinegar liquor, characterized in that It includes the following steps: (1) Salting-out pretreatment: Add 3-8% sodium chloride to the original bamboo vinegar solution for salting-out, stir and dissolve it, and then let it stand for 48 hours; (2) Filtration for impurity removal: Filter to remove the precipitate generated by salting-out; (3) Vacuum distillation: Perform vacuum distillation on the filtrate at 75°C and -0.06 Mpa to obtain refined bamboo vinegar solution; Synergy of salting-out and vacuum distillation: Improve the boiling point of the distillate through salting-out pretreatment, and avoid the destruction of active ingredients at high temperature through vacuum distillation.

2. The process according to claim 1, characterized in that: The addition amount of the sodium chloride is 3-8% of the mass of the original bamboo vinegar solution.

3. The process according to claim 1, characterized in that: Utilize the salting-out effect to promote the precipitation of macromolecular impurity colloids and tar precursors, and let it stand for 48 hours.

4. The process according to claim 1, characterized in that: The temperature of the vacuum distillation is 75°C, and the negative pressure is -0.08 MPa to -0.1 MPa.

5. The process according to claim 1, characterized in that: The pH of the obtained refined bamboo vinegar solution is ≤3, the retention of organic acids is ≥95%, and the tar content is ≤0.1%.

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