CN102702383A - A method for CO2 gas neutralization of alkaline substances in chitosan preparation process - Google Patents

Abstract

The invention relates to a method for neutralizing alkaline substances in the preparation process of chitosan with _CO2 gas, which is characterized in that it comprises the following steps: after the chitin raw material is subjected to deacetylation treatment with concentrated alkali solution, the chitin is injected under different pressures into _CO2 gas is passed into the mixture until the mixture is neutral, and the solid and liquid are separated, and the solid is the crude chitosan. The method for neutralizing alkaline substances in the preparation process of chitosan by _CO gas of the present invention adopts _CO gas under different pressures to neutralize the alkaline substances obtained by deacetylation of chitin raw materials in the preparation process of chitosan to replace In the traditional process, the method of washing alkaline substances with water to neutrality is simple and easy to operate, and reduces the consumption of a lot of time, manpower and water resources, reduces the cost of the enterprise, and is beneficial to the large-scale production of the enterprise.

Description

A method for CO2 gas neutralization of alkaline substances in chitosan preparation process

technical field

The invention belongs to the field of biochemical industry, and relates to a method for neutralizing alkaline substances obtained by deacetylating chitin raw materials in the preparation process of chitosan, especially a method for neutralizing alkaline substances in the preparation process of chitosan with _CO2 gas .

Background technique

Chitin widely exists in the shells of crustaceans such as shrimps, crabs, and insects, and in the cell walls of fungi, and is the second largest natural organic compound in storage after cellulose in nature. Chitosan, the deacetylated product of chitin, is widely used in food industry, pharmaceutical industry, light textile industry and environmental protection industries.

At present, the production of chitin and chitosan at home and abroad uses shrimp and crab shells as the main raw materials, and the process mainly includes several processes such as decalcification, deproteinization and decolorization. The basic process is divided into three steps: 1. Use dilute hydrochloric acid to remove calcium ions; 2. Use dilute NaOH to remove protein to obtain chitin; 3. Use concentrated NaOH solution to remove acetyl groups from chitin to obtain chitosan. The deacetylation of chitosan for the preparation of chitin raw materials requires the treatment of the sample with a high concentration of lye and the treatment of the obtained material to neutrality. The traditional method is to repeatedly wash with water, centrifuge or filter, and finally achieve neutrality. In this way, not only the reaction end point is not easy to control, but also consume a lot of manpower, time and water resources, the cost is high, and a large amount of lye wastewater is produced, which has caused serious pollution to the environment and is not conducive to large-scale production.

By searching, two patent publications related to this patent application were found, as follows:

1. A method for preparing chitosan (CN101838346A), which relates to a method for preparing chitosan through deacetylation of chitin, which includes pretreatment of chitin and strengthening deacetylation of chitin through a hydraulic cavitation device Reaction and the steps of centrifugal washing and drying of the reaction solution, the strengthening of the chitin deacetylation reaction through the hydraulic cavitation device is to add chitin particles to the NaOH solution to form a mixed solution, and add the mixed solution to the hydraulic cavitation device In the storage tank, and the temperature is controlled at 40-90°C through the circulating water tank, and the circulating treatment is carried out in the hydraulic cavitation device for 0.5h-20h until the chitin deacetylation degree of the mixed solution is 60-95%. When the chitin deacetylation reaction is carried out in the hydraulic cavitator, the mixed solution must meet the technical conditions such as cavitation number C<2; the method can achieve the effect of greatly shortening the preparation process time at low temperature (below 90°C).

2. A new method for preparing fly maggot chitosan (CN102321192A). The invention provides a new method for preparing fly maggot chitosan, which comprises the following steps: 1) pretreatment of maggot maggot: removing impurities; 2) maggot larvae Stirring, soaking and washing the shells with hydrochloric acid solution; 3) soaking the maggot shells washed in step 2) with sodium hydroxide solution to remove waste; 4) decolorizing the maggot shells obtained in step 3) to obtain crude maggot shells Chitin; 5) The crude fly maggot chitin is deacetylated by microwave heating to obtain chitosan. Utilize method described in the present invention to extract chitosan from fly maggot shell and have following advantage: 1) the degree of deacetylation of chitosan is brought up to 94.4%, compared with national relevant standard, has reached high degree of deacetylation, and product quality has promoted one. 2) The recovery rate of chitosan has increased; 3) The deacetylation process takes a short time and has low energy consumption.

By comparison, this patent application is substantially different from the above two patent publications.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, provide a kind of method simple, easy to operate, and can reduce the consumption of a large amount of time and water resources, and the _CO2 gas that does not pollute the environment neutralizes alkali in chitosan preparation process method of sexual substance.

The technical scheme that the present invention realizes purpose is:

A method for _CO2 gas to neutralize alkaline substances in the chitosan preparation process, comprising the following steps: after the chitin raw material is subjected to deacetylation treatment with concentrated alkali solution, _CO2 gas is passed into the mixture under different pressures , until the mixture is neutral, the solid and liquid are separated, and the obtained solid is crude chitosan.

Moreover, the chitin raw material includes shells of crustaceans, molluscs and fungi.

Furthermore, said crustaceans are shrimps, crabs and insects.

Moreover, the concentrated lye comprises a compound selected from the following: sodium hydroxide, potassium hydroxide or a combination thereof.

Moreover, the mass concentration of the lye is 20-60%.

Moreover, the solid-to-liquid ratio g:mL of the chitin raw material and the concentrated alkali solution is 1:8-50.

Moreover, the feeding pressure of the CO ₂ gas is 0-10MPa.

Advantage of the present invention and beneficial effect are:

1, _CO2 gas of the present invention neutralizes the method for alkaline substance in the chitosan preparation process, adopts _CO under different pressures Gas neutralizes the alkaline substance that chitin raw material obtains through deacetylation in the chitosan preparation process, with It replaces the method of washing alkaline substances with water to neutrality in the traditional process. The method is simple and easy to operate, and it reduces the consumption of a lot of time, manpower and water resources, reduces the cost of the enterprise, and is beneficial to the large-scale production of the enterprise.

2. The method of the present invention is aimed at the alkaline matter produced by deacetylation in the chitosan process prepared from chitin raw materials, and adopts the method of feeding _CO2 gas to carry out neutralization reaction. Since chitosan is soluble in dilute acid, if acid is used to neutralize alkaline substances, the solution will be partially acid-accepted unevenly, causing local acid to dissolve local chitosan before it is neutralized with lye, making chitosan sugar loss. However, this phenomenon can be avoided by passing _CO2 into the lye, so that the lye and _CO2 are neutralized, and the resulting sodium carbonate or sodium bicarbonate is soluble in water, while chitosan is insoluble in water and can be separated. This method provides a simple and green idea for the preparation process of chitosan.

Detailed ways

The present invention will be further described in detail below through the specific examples, the following examples are only descriptive, not restrictive, and cannot limit the protection scope of the present invention with this.

The invention is a new method for neutralizing alkaline substances in the preparation process of chitosan. The method includes introducing _CO2 gas to neutralize the alkaline substance obtained in the chitosan preparation process, that is, the neutralization method of the alkaline substance obtained through deacetylation of the chitin raw material.

Example 1:

(1) Weigh 10 g of fly maggot shells, grind them into pieces with a mortar, add 3% NaOH solution with a mass concentration of 1:8 (g/mL), and treat them in a boiling water bath for 2 hours for deproteinization;

(2) Add a mass concentration of 5% HCl solution to the reaction solution in step (1), the solid-to-liquid ratio is 1:8 (g/mL), and treat in a boiling water bath for 1 hour to obtain crude chitin;

(3) Add a mass concentration of 40% NaOH solution to the crude chitin in step (2), the solid-to-liquid ratio is 1:8 (g/mL), treat in a boiling water bath for 2 hours for deacetylation, and obtain the crude chitosan;

(4) The mixture in the separation step (3), and the liquid can be recycled. Measure the pH of the remaining alkaline substance to be 13.19, transfer it to a 5L autoclave, feed _CO2 gas under 4MPa pressure, release the pressure after 1 hour of reaction, measure the pH to be 7.07, wash away _{Na2CO3 and} NaHCO ₃ , until the measured conductivity does not change. The solid was separated to obtain the crude chitosan.

Comparative Experiment:

Three parallel experiments were done in each group, and the samples from alkaline to neutral obtained by deacetylation of chitin raw materials in the preparation process of water-washed chitosan were used as the control group.

Comparison of measurement results:

The sample control group uses water to wash alkaline substances to neutral, the final pH is 7.02, each sample uses 3200mL of water each time, and discharges a large amount of alkaline sewage;

The chitosan crude product of the present invention uses _CO gas to neutralize alkaline substances, the final pH is 7.07, and each sample uses 500 mL of water each time.

By comparison, it is found that the washing water consumption of the chitosan crude product in the method of the present invention is only 15.63% of that in the water washing method, which reduces the consumption of a large amount of water resources.

Example 2:

(1) Weigh 10 g of crab shells, grind them into pieces with liquid nitrogen, add 2% NaOH solution with a mass concentration of 1:10 (g/mL), and treat in a water bath at 90°C for 4 hours for deproteinization;

(2) Add a mass concentration of 3% HCl solution to the reaction solution in step (1), the solid-to-liquid ratio is 1:10 (g/mL), and treat in a water bath at 90°C for 2 hours to obtain crude chitin;

(3) Add a mass concentration of 50% NaOH solution to the crude chitin in step (2), the solid-to-liquid ratio is 1:10 (g/mL), and treat it in a water bath at 90°C for 4 hours for deacetylation to obtain the crude chitosan;

(4) The mixture in the separation step (3), and the liquid can be recycled. Measure the pH of the remaining alkaline substance to be 12.78, pass CO ₂ gas under normal pressure, measure the pH to 7.03 after 10 hours of reaction, wash away Na ₂ CO ₃ and NaHCO ₃ with water, and measure the conductivity until the conductivity remains unchanged. A solid, crude chitosan, was isolated.

Comparative Experiment:

Three parallel experiments were done in each group, and the samples from alkaline to neutral obtained by deacetylation of chitin raw materials in the preparation process of water-washed chitosan were used as the control group.

Comparison of measurement results:

The sample control group uses water to wash alkaline substances to neutral, the final pH is 7.01, each sample uses 3150mL of water each time, and discharges a large amount of alkaline sewage;

The chitosan crude product of the present invention uses _CO gas to neutralize alkaline substances, the final pH is 7.03, and each sample uses 500 mL of water each time.

By comparison, it is found that the washing water consumption of the chitosan crude product in the method of the present invention is only 15.87% of that in the water washing method, which reduces the consumption of a large amount of water resources.

Example 3:

(1) Weigh 10g of fly pupae, crush it into powder with a pulverizer, add 5% KOH solution with a mass concentration of 1:20 (g/mL), and treat it in a water bath at 110°C for 3 hours for deproteinization;

(2) Add a mass concentration of 3% HCl solution to the reaction solution in step (1), the solid-to-liquid ratio is 1:20 (g/mL), and treat in a water bath at 110°C for 2 hours to obtain crude chitin;

(3) Add KOH solution with a mass concentration of 60% to the crude chitin in step (2), the solid-to-liquid ratio is 1:50 (g/mL), and treat in a water bath at 110°C for 3 hours for deacetylation to obtain crude chitosan;

(4) The mixture in the separation step (3), and the liquid can be recycled. Measure the pH of the remaining alkaline substance to be 13.42, transfer it to a 5L autoclave, feed _CO2 gas under the pressure of 10MPa, release the pressure after 0.25 hours of reaction, measure the pH to be 7.05, wash away _{Na2CO3 and} NaHCO ₃ , until the measured conductivity does not change. A solid, crude chitosan, was isolated.

Comparative Experiment:

Three parallel experiments were done in each group, and the samples from alkaline to neutral obtained by deacetylation of chitin raw materials in the preparation process of water-washed chitosan were used as the control group.

Comparison of measurement results:

The sample control group uses water to wash alkaline substances to neutral, the final pH is 7.02, each sample uses 3500mL of water each time, and discharges a large amount of alkaline sewage;

The chitosan crude product of the present invention uses _CO gas to neutralize alkaline substances, the final pH is 7.04, and each sample uses 500 mL of water each time.

By contrast, it is found that the washing water consumption of the chitosan crude product in the method of the present invention is only 14.29% of that in the washing method, which reduces the consumption of a large amount of water resources.

Claims (7)

1. a kind of _CO The method for alkaline matter in the chitosan preparation process in gas neutralization, it is characterized in that: comprise the following steps: after the chitin raw material is carried out deacetylation process through concentrated lye, under different pressures, to mixture CO ₂ gas is introduced into the medium until the mixture is neutral, and the solid and liquid are separated, and the obtained solid is crude chitosan. 2. CO according to claim ₁ The method for gas neutralizing alkaline substances in the chitosan preparation process is characterized in that: the chitin raw material comprises crustacean shells, molluscs and fungi. 3. CO according to claim ₂ The method for gas neutralization and alkaline matter in the chitosan preparation process is characterized in that: the crustaceans are shrimps, crabs and insects. 4. CO according to claim ₁ the method for alkaline matter in gas neutralization and chitosan preparation process, is characterized in that: described concentrated lye comprises and is selected from following compound: sodium hydroxide, potassium hydroxide or their The combination. 5. CO according to claim ₁ The method for gas neutralization and alkaline matter in chitosan preparation process, is characterized in that: described lye mass concentration is 20-60%. 6. CO according to claim ₁ The method for alkaline matter in gas neutralization and chitosan preparation process is characterized in that: the solid-liquid ratio g of described chitin raw material and concentrated lye: mL is 1:8 -50. 7. CO according to claim ₁ gas neutralizes the method for alkaline matter in the chitosan preparation process, is characterized in that: described _CO The feeding pressure of gas is 0-10MPa.