A method for the synthesis of a cellulose-based acid-base indicator

Abstract

This invention relates to a method for synthesizing an acid-base indicator from cellulose. The method involves mixing a cellulose raw material with a non-volatile acid, heating and carbonizing the mixture in high-temperature air, washing the carbonized material with water, neutralizing the suspension with alkali, filtering to remove inorganic salts, and evaporating the water to obtain the acid-base indicator. The cellulose raw material is cellulose and / or materials containing cellulose, and the non-volatile acid includes one or more of sulfuric acid, phosphoric acid, perchloric acid, benzenesulfonic acid, p-toluenesulfonic acid, and benzoic acid. This invention utilizes non-toxic, harmless, and low-cost cellulose as a raw material to prepare the acid-base indicator through a simple and environmentally friendly production process. The synthesis technology has advantages such as low raw material price and easy availability, simple preparation process, no environmental pollution, and easy product separation.

Description

Technical Field

[0001] This invention relates to a method for synthesizing an acid-base indicator from cellulose, belonging to the field of chemical synthesis technology. Background Technology

[0002] Acid-base indicators are a class of structurally complex organic weak acids or bases. When they react with acids and bases, molecules and ions interconvert. Because their molecules and ions have different colors, the color of their solution changes with different pH values. Commonly used acid-base indicators include phenolphthalein, thymol blue, bromophenol blue, methyl orange, methyl yellow, methyl red, neutral red, and Congo red. All of these are synthesized from toxic raw materials through organic reactions, resulting in high costs and environmental pollution. Therefore, it is necessary to explore a method for synthesizing acid-base indicators using non-toxic raw materials and with ease. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for synthesizing an acid-base indicator, which can use non-toxic, harmless, and low-cost cellulose and cellulose-containing materials as raw materials to prepare the acid-base indicator through a simple and environmentally friendly production process.

[0004] The technical solution to the above-mentioned technical problem is: a method for synthesizing an acid-base indicator from cellulose, comprising the following steps: mixing cellulose raw material with a non-volatile acid at a mass ratio of 1:0.1 to 0.8, heating and carbonizing in high-temperature air at a carbonization temperature of 80℃ to 250℃ for a carbonization time of 0.2 to 6 hours, washing the carbonized material with water, neutralizing the suspension with alkali, filtering, collecting the filtrate, removing inorganic salts, evaporating the water to dryness, and obtaining the acid-base indicator.

[0005] The cellulose raw material is cellulose and / or a material containing cellulose, and the non-volatile acid includes one or more of sulfuric acid, phosphoric acid, perchloric acid, benzenesulfonic acid, p-toluenesulfonic acid, and benzoic acid.

[0006] Furthermore, cellulose-containing materials include one or more of woody plants, herbaceous plants, agricultural waste, paper, and bacterial cellulose.

[0007] Furthermore, the prepared acid-base indicator is colorless in acidic and neutral environments, and turns green in alkaline environments.

[0008] Furthermore, the cellulose raw material is mixed with the non-volatile acid at a mass ratio of 1:0.2 to 0.4.

[0009] Furthermore, the carbonization temperature is 170℃~230℃.

[0010] Furthermore, the carbonization time is 3 to 5 hours.

[0011] Furthermore, the procedure for washing the carbonized material with water is as follows: add water to the carbonized material to soak it, and stir it thoroughly. The amount of water used is calculated as 0.8 to 1.5 ml of water per 1 g of cellulose raw material.

[0012] Further, the operation to remove inorganic salts is as follows: after evaporating the water from the filtrate to obtain a concentrated solution, the concentrated solution is cooled to 0-5℃ to allow the inorganic salts to crystallize out, and then filtered to remove the inorganic salts.

[0013] The principle of synthesizing the acid-base indicator in this invention is as follows:

[0014] In a high-temperature, aerobic environment, cellulose undergoes dehydration, oxidation, and condensation reactions under the catalysis of acid, producing substances containing phenolic hydroxyl and carboxyl groups. After washing with water, these substances form a solution. These substances are weak acids, but they lose protons upon contact with a base, becoming basic molecular structures. Since acid and basic molecular structures exhibit different colors, they can indicate the acidity or alkalinity of the solution.

[0015] Compared with the prior art, the advantages of the present invention are:

[0016] Cellulose raw materials are inexpensive, widely available, easy to obtain, and can be rapidly regenerated. The carbonization process is simple, does not produce toxic gases or liquids, and the product separation is easy. Attached Figure Description

[0017] Figure 1 The ultraviolet-visible absorption spectrum of the acid-base indicator prepared in Example 1 of this invention.

[0018] Figure 2 The infrared-visible absorption spectrum of the acid-base indicator prepared in Example 1 of this invention.

[0019] Figure 3 Raman spectrum of the acid-base indicator prepared in Example 1 of this invention. Implementation

[0020] The required equipment includes: a heating furnace, a filtration device, and an evaporation device. Example 1

[0021] 1 gram of microcrystalline cellulose and 0.3 grams of sulfuric acid were thoroughly mixed. The mixture was placed in a muffle furnace and heated to 180°C for 4 hours. The carbonized material was removed, and 1 ml of water was added to soak it while stirring thoroughly. A 10% NaOH solution was added dropwise to adjust the pH of the suspension to 7. The mixture was filtered, and the filtrate was collected and evaporated in a rotary evaporator. The concentrate was cooled to 5°C to allow sodium sulfate to crystallize out. The sodium sulfate was removed by filtration, and the water in the filtrate was evaporated to dryness. The residue was the acid-base indicator product, with a yield of approximately 13%. The prepared indicator is colorless in acidic and neutral environments and green in alkaline environments. The UV-Vis absorption spectrum of the acid-base indicator product was tested (e.g., ...). Figure 1As shown in the figure, it was found that under acidic conditions (pH=2), there was no absorption peak in the visible light region (400–800 nm), corresponding to a colorless solution observed with the naked eye. Under alkaline conditions (pH=11), there was a significant absorption peak in the visible light region (400–800 nm), and the complementary light of green light was absorbed by the solution, so the solution appeared green to the naked eye. Infrared spectroscopy (such as...) Figure 2 As shown in the image, the product contains a large number of conjugated C=C and C=O groups, which are typical chromogenic groups and the structural basis for the green color of the target product. Figure 3 Raman spectroscopy showed that the sample had a strong fluorescence effect, indicating that the sample contained a large amount of substances that could absorb ultraviolet light, which also confirmed the presence of C=C and C=O unsaturated groups. Example 2

[0022] 1 gram of poplar sawdust and 0.3 grams of phosphoric acid were thoroughly mixed. The mixture was placed in a muffle furnace and heated to 220°C for 1 hour. The carbonized material was removed, and 1 ml of water was added to soak it while stirring thoroughly. A 10% NaOH solution was added dropwise to adjust the pH of the suspension to 7. The solution was filtered, and the filtrate was collected and evaporated in a rotary evaporator. The concentrate was cooled to 0°C to allow disodium hydrogen phosphate and sodium monohydrogen phosphate to crystallize out. The disodium hydrogen phosphate and sodium monohydrogen phosphate were removed by filtration, and the water was evaporated to dryness. The residue was the acid-base indicator product, with a yield of approximately 5%. The prepared indicator was colorless in acidic and neutral environments and green in alkaline environments, with the color deepening as the alkalinity increased. Example 3

[0023] 1 gram of air-dried barnyard grass and 0.3 grams of perchloric acid were thoroughly mixed. The mixture was placed in a muffle furnace and heated to 80°C for 6 hours. The carbonized material was removed, and 1 ml of water was added to soak it while stirring thoroughly. A 10% NaOH solution was added dropwise to adjust the pH of the suspension to 7. The solution was filtered, and the filtrate was collected and evaporated in a rotary evaporator. The concentrate was cooled to 0°C to allow sodium perchlorate to crystallize out. The sodium perchlorate was removed by filtration, and the water was evaporated to dryness. The residue was the acid-base indicator product, with a yield of approximately 6%. The prepared indicator was colorless in acidic and neutral environments and green in alkaline environments, with the color deepening as the alkalinity increased. Example 4

[0024] 1 gram of dry rice straw and 0.3 grams of benzenesulfonic acid were thoroughly mixed. The mixture was placed in a muffle furnace and heated to 130°C for 3 hours. The carbonized material was removed, and 1 ml of water was added to soak it while stirring thoroughly. A 10% NaOH solution was added dropwise to adjust the pH of the suspension to 7. The solution was filtered, and the filtrate was collected and evaporated in a rotary evaporator. The concentrate was cooled to 5°C to allow sodium benzenesulfonate to crystallize out. The sodium benzenesulfonate was removed by filtration, and the water was evaporated to dryness. The residue was the acid-base indicator product, with a yield of approximately 3%. The prepared indicator was colorless in acidic and neutral environments, and green in alkaline environments, with the color deepening as the alkalinity increased. Example 5

[0025] 1 gram of A4 printing paper and 0.3 grams of sulfuric acid were thoroughly mixed. The mixture was placed in a muffle furnace and heated to 220°C for 0.2 hours. The carbonized material was removed, and 1 ml of water was added to soak it while stirring thoroughly. A 10% NaOH solution was added dropwise to adjust the pH of the suspension to 7. The solution was filtered, and the filtrate was collected and placed in a rotary evaporator to evaporate the water. The concentrate was cooled to 5°C to allow sodium sulfate to crystallize out. The sodium sulfate was removed by filtration, and the water was evaporated to dryness. The residue was the acid-base indicator product, with a yield of approximately 4%. The prepared indicator was colorless in acidic and neutral environments and green in alkaline environments, with the color deepening as the alkalinity increased. Example 6

[0026] 1 gram of bacterial cellulose (produced by Acetobacter xylinum) and 0.3 grams of p-toluenesulfonic acid were thoroughly mixed. The mixture was placed in a muffle furnace and heated to 115°C for 4 hours. The carbonized material was removed, and 1 ml of water was added to soak it while stirring thoroughly. A 10% NaOH solution was added dropwise to adjust the pH of the suspension to 7. The solution was filtered, and the filtrate was collected and evaporated in a rotary evaporator. The concentrate was cooled to 5°C to allow sodium p-toluenesulfonate to crystallize out. The sodium p-toluenesulfonate was removed by filtration, and the water was evaporated to dryness. The residue was the acid-base indicator product, with a yield of approximately 5%. The prepared indicator was colorless in acidic and neutral environments, and green in alkaline environments, with the color deepening as the alkalinity increased. Example 7

[0027] 1 gram of dry sugarcane bagasse and 0.3 grams of benzoic acid were thoroughly mixed. The mixture was placed in a muffle furnace and heated to 205°C for 4 hours. The carbonized material was removed, and 1 ml of water was added to soak it while stirring thoroughly. A 10% NaOH solution was added dropwise to adjust the pH of the suspension to 7. The solution was filtered, and the filtrate was collected and evaporated in a rotary evaporator. The concentrate was cooled to 5°C to allow sodium benzoate to crystallize out. The sodium benzoate was removed by filtration, and the water was evaporated to dryness. The residue was the acid-base indicator product, with a yield of approximately 3%. The prepared indicator was colorless in acidic and neutral environments, and green in alkaline environments, with the color deepening as the alkalinity increased. Example 8

[0028] 1 gram of dried banana leaves and 0.3 grams of sulfuric acid were thoroughly mixed. The mixture was placed in a muffle furnace and heated to 250°C for 3 hours. The carbonized material was removed, and 1 ml of water was added to soak it while stirring thoroughly. A 10% NaOH solution was added dropwise to adjust the pH of the suspension to 7. The solution was filtered, and the filtrate was collected and evaporated in a rotary evaporator. The concentrate was cooled to 5°C to allow sodium sulfate to crystallize out. The sodium sulfate was removed by filtration, and the water was evaporated to dryness. The residue was the acid-base indicator product, with a yield of approximately 6%. The prepared indicator was colorless in acidic and neutral environments, and green in alkaline environments, with the color deepening as the alkalinity increased.

Claims

1. A method for synthesizing an acid-base indicator from cellulose, characterized in that: Includes the following steps: Cellulose raw material is mixed with a non-volatile acid at a mass ratio of 1:0.1 to 0.8, and then heated and carbonized in high-temperature air at a temperature of 80℃ to 250℃ for 0.2 to 6 hours. The carbonized material is washed with water, the suspension is neutralized with alkali, filtered, the filtrate is collected, inorganic salts are removed, and the water is evaporated to dryness to obtain an acid-base indicator. The cellulose raw material is cellulose and / or a material containing cellulose, and the non-volatile acid includes one or more of sulfuric acid, phosphoric acid, perchloric acid, benzenesulfonic acid, p-toluenesulfonic acid, and benzoic acid.

2. The method for synthesizing an acid-base indicator from cellulose according to claim 1, characterized in that: Materials containing cellulose include one or more of the following: woody plants, herbaceous plants, agricultural waste, paper, and bacterial cellulose.

3. A method for synthesizing an acid-base indicator from cellulose according to claim 1 or 2, characterized in that: The prepared acid-base indicator is colorless in acidic and neutral environments, and turns green in alkaline environments.

4. The method for synthesizing an acid-base indicator from cellulose according to claim 3, characterized in that: Cellulose raw materials and non-volatile acids are mixed at a mass ratio of 1:0.2 to 0.

4.

5. The method for synthesizing an acid-base indicator from cellulose according to claim 3, characterized in that: The carbonization temperature is 170℃~230℃.

6. The method for synthesizing an acid-base indicator from cellulose according to claim 3, characterized in that: The carbonization time is 3 to 5 hours.

7. The method for synthesizing an acid-base indicator from cellulose according to claim 3, characterized in that: The procedure for washing carbonized materials with water is as follows: add water to the carbonized materials to soak them, and stir thoroughly. The amount of water used is calculated as 0.8 to 1.5 ml of water per 1 g of cellulose raw material.

8. The method for synthesizing an acid-base indicator from cellulose according to claim 3, characterized in that: The procedure for removing inorganic salts is as follows: after evaporating the water from the filtrate, a concentrated solution is obtained. The concentrated solution is then cooled to 0-5℃ to allow the inorganic salts to crystallize and precipitate. Finally, the inorganic salts are removed by filtration.

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