A modified starch and preparation method thereof

Abstract

The present application discloses a method for preparing modified starch, comprising the following steps: 1) dispersing starch in a liquid, adding biological enzymes for enzymolysis, centrifuging, washing and drying to obtain porous starch; 2) dispersing porous starch in a liquid under alkaline conditions, reacting with epichlorohydrin, centrifuging, washing and drying to obtain porous cross-linked starch; 3) dispersing porous cross-linked starch in a liquid under acidic conditions, reacting with hydrogen peroxide, centrifuging, washing and drying to obtain porous oxidized starch; 4) dispersing porous oxidized starch in a liquid, reacting with diethylenetriamine, centrifuging, washing and drying to obtain porous amino starch. The present application also provides a modified starch. The preparation method provided by the present application has a simple preparation process and low manufacturing cost. The prepared modified starch is non-toxic and pollution-free, environmentally friendly, and has excellent effects in adsorption, stability, safety, etc., providing an effective way for treating flue gas containing harmful gases.

Description

Technical Field

[0001] The present application relates to the technical field of modified materials, and in particular to a modified starch and a preparation method thereof. Background Art

[0002] Starch is a biodegradable natural material with the advantages of being abundant, cheap and renewable. It is widely used in medicine, food, textile, papermaking, chemical industry, etc. In order to meet the demand for starch in industrial development, people also use physical, chemical or biological methods to modify starch. Among the many modified starches, adsorbed starch has attracted extensive attention from researchers due to its excellent adsorption performance.

[0003] At present, many scholars at home and abroad have used bio-enzyme method to modify starch to improve the adsorption performance of starch. The research results show that the specific surface area of ​​the modified starch increases, and some fine pores are formed, which improves the adsorption effect. However, in the existing research, few people have reported on the adsorption of harmful gases by modified starch.

[0004] Therefore, how to develop a modified starch that has a significant adsorption capacity for harmful substances, especially harmful substances in flue gas, is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] In order to solve the above technical problems, the first purpose of the present invention is to provide a method for preparing modified starch; the second purpose of the present invention is to provide modified starch prepared by the above method; the preparation method provided by the present application has a simple preparation process and low manufacturing cost, the prepared modified starch is non-toxic and pollution-free, environmentally friendly, and has excellent adsorption, stability, safety and other effects, providing an effective way for the treatment of flue gas containing harmful gases.

[0006] The technical solution provided by the present invention is as follows:

[0007] A method for preparing modified starch comprises the following steps:

[0008] 1) Starch is dispersed in liquid, enzymatically hydrolyzed by adding biological enzymes, centrifuged, washed and dried to obtain porous starch;

[0009] 2) under alkaline conditions, the porous starch is dispersed in a liquid, reacted with epichlorohydrin, centrifuged, washed and dried to obtain the porous cross-linked starch;

[0010] 3) under acidic conditions, dispersing the porous cross-linked starch in a liquid, reacting with hydrogen peroxide, centrifuging, washing and drying to obtain the porous oxidized starch;

[0011] 4) The porous oxidized starch is dispersed in a liquid, reacted with diethylenetriamine, centrifuged, washed and dried to obtain the porous amino starch.

[0012] Preferably, the starch is made from one or more of corn, wheat, potato, and cassava;

[0013] The biological enzyme is one or more of α-amylase, β-amylase, γ-amylase, isoamylase, and saccharifying enzyme;

[0014] The weight ratio of starch to biological enzyme is 100:(1-5).

[0015] Preferably, in step 2), the weight ratio of porous starch to epichlorohydrin is 100:(5-8);

[0016] In step 3), the weight ratio of porous cross-linked starch to hydrogen peroxide is 100:(60-65);

[0017] In step 4), the weight ratio of porous oxidized starch to diethylenetriamine is 100:(40-60).

[0018] Preferably, the enzymolysis is carried out in a constant temperature water bath at 25-60° C., and the enzymolysis time is 3-8 hours.

[0019] Preferably, in step 1), the starch is dispersed in a buffer solution with a pH of 4-5 to form a starch dispersion, biological enzymes are added for hydrolysis, and then alkali is added to terminate the reaction, centrifuged, washed and dried to obtain porous starch.

[0020] Preferably, in step 2), the porous starch is dispersed in a sodium hydroxide solution with a pH of 11-12 to form a porous starch dispersion, epichlorohydrin is added, and the mixture is reacted in a constant temperature water bath at 25-30° C. for 5-6 hours, centrifuged, washed, and dried to obtain porous cross-linked starch.

[0021] Preferably, in step 3), the porous cross-linked starch is dispersed in an acidic buffer solution to form a porous cross-linked starch dispersion, the pH is adjusted to 5-6, hydrogen peroxide is added, and the reaction is carried out in a constant temperature water bath at 45-50°C for 3-4h, sodium thiosulfate is added to terminate the reaction, the solution is centrifuged, washed and dried to obtain porous oxidized starch.

[0022] Preferably, the porous oxidized starch is dispersed in a buffer solution, the pH is adjusted to neutral, diethylenetriamine is added, the mixture is reacted in a constant temperature water bath at 45-50° C. for 3-4 hours, centrifuged, washed and dried to obtain the porous amino starch.

[0023] Preferably, the centrifugation is specifically: centrifugal treatment at a speed of 4000-5000 r / min for 5-10 min.

[0024] Preferably, washing and drying specifically include: washing with deionized water for 2-3 times, centrifuging again after each washing, and then drying at 60-65° C. for 12-14 hours. The modified starch obtained by any of the above preparation methods.

[0025] The present application provides a method for preparing modified starch, wherein starch is sequentially subjected to enzymatic hydrolysis, reaction with epichlorohydrin, reaction with hydrogen peroxide, and reaction with diethylenetriamine to obtain porous amino starch. The method for preparing modified starch provided by the present application uses two modification methods, biological method and chemical method, to cooperate with each other, and creatively finds that the prepared porous amino starch can effectively adsorb harmful gases (such as phenol, etc.) in flue gas. Specifically, starch is modified by biological enzyme method to form a porous structure of starch, which can generate a large attraction, adsorb the adsorbate into the small pores, and the adsorption is firm, and the adsorbate is not easy to detach; enzymatic hydrolysis treatment improves the adsorption on the one hand, and increases the action sites in the chemical modification process on the other hand, which is convenient for introducing amino groups; the present application also uses cross-linking and oxidation methods to introduce amino groups in porous starch. Since starch contains -NH2 active groups in its molecular structure, it is easy to form stable complexes with substances such as phenol in flue gas, thereby achieving effective adsorption of phenol.

[0026] The preparation method provided in the present application fully combines the characteristics of absorptive starch and comprehensive application requirements, and carries out targeted process design, thereby achieving excellent results in terms of adsorption, stability, safety, etc., and provides an effective way to treat flue gas containing harmful gases.

[0027] The present application also provides modified starch prepared by the above method, which is non-toxic, pollution-free, environmentally friendly, safe and reliable, and has excellent characteristics such as good stability, simple preparation process, and low manufacturing cost.

[0028] In the preparation method provided in the present application, the reaction of starch with biological enzymes, the reaction of porous starch with epichlorohydrin, and the reaction of porous cross-linked starch with hydrogen peroxide are preferably carried out in a buffer solution, and the pH is adjusted within a suitable range. The buffer solution preferably uses a sodium hydrogen phosphate-citric acid buffer solution, and the pH is adjusted by HCl or NaOH. In addition, a buffer solution such as citric acid-sodium citrate can also be used.

[0029] Preferably, in step 1), a biological enzyme is added for enzymolysis, and then a base is added to terminate the reaction. The amount of the base is determined according to actual needs, and the pH of the solution is adjusted from acidic to neutral. Preferably, sodium hydroxide is added to terminate the reaction. Sodium hydroxide is preferably used in the form of a solution, and the concentration can be 0.8-1.2 mol / L, more preferably 1.0-1.1 mol / L.

[0030] In step 3), after the porous cross-linked starch reacts with hydrogen peroxide, sodium thiosulfate is added to terminate the reaction. Preferably, the weight ratio of hydrogen peroxide to sodium thiosulfate is 10:(1-1.5). BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 X-ray diffraction patterns (XRD) of Example 1 and Comparative Example 1 of the present invention;

[0033] Figure 2 The scanning electron microscope (SEM) images of Example 1 and Comparative Example 1 of the present invention are shown;

[0034] Figure 3 The infrared spectra (FTIR) of Example 1 and Comparative Example 1 of the present invention are as follows;

[0035] Figure 4 This is the adsorption performance spectrum of Example 1 of the present invention;

[0036] Figure 5 This is the adsorption performance spectrum of Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0038] Example 1

[0039] 1) Dispersing 100 parts of starch (corn starch) by weight in a sodium hydrogen phosphate-citric acid buffer solution with a pH of 4 to form a starch dispersion, adding 1 part of a biological enzyme (α-amylase), stirring in a constant temperature water bath at 25° C. for 3 hours, then adding 10 parts of a sodium hydroxide solution (concentration 1 mol / L) to terminate the reaction, and obtaining porous starch after centrifugal washing and drying;

[0040] 2) dispersing 100 parts of the prepared porous starch in a sodium hydroxide solution with a pH of 11 to form a porous starch dispersion, then adding 5 parts of epichlorohydrin, stirring in a constant temperature water bath at 25° C. for 5 hours, and obtaining porous cross-linked starch after centrifugal washing and drying;

[0041] 3) dispersing 100 parts of porous cross-linked starch in a sodium hydrogen phosphate-citric acid buffer solution to form a porous cross-linked starch dispersion, adjusting the pH to 5, adding 60 parts of hydrogen peroxide, stirring in a constant temperature water bath at 45° C. for 3 hours, then adding 6 parts of sodium thiosulfate to terminate the reaction, and obtaining porous oxidized starch after centrifugal washing and drying;

[0042] 4) dispersing 100 parts of porous oxidized starch in a disodium hydrogen phosphate-citric acid buffer solution to form a porous oxidized starch dispersion, adjusting the pH to 7, adding 40 parts of diethylenetriamine, stirring in a constant temperature water bath at 45° C. for 3 hours, and washing by centrifugation and drying to obtain porous amino starch;

[0043] In the above operation, centrifugation is specifically: centrifugation at a speed of 4000 r / min for 5 minutes; washing and drying are specifically: washing with deionized water for 3 times, centrifuging again after each washing, and then drying at 60° C. for 12 hours.

[0044] Example 2

[0045] 1) Dispersing 100 parts by weight of starch (obtained by mixing wheat starch and corn starch in a weight ratio of 1:1) in a disodium hydrogen phosphate-citric acid buffer solution with a pH of 4 to form a starch dispersion, adding 3 parts of biological enzymes (α-amylase, β-amylase and isoamylase in a weight ratio of 1:1:1), stirring in a constant temperature water bath at 50° C. for 6 hours, then adding 10 parts of sodium hydroxide solution (concentration of 1 mol / L) to terminate the reaction, and obtaining porous starch after centrifugal washing and drying;

[0046] 2) dispersing 100 parts of the prepared porous starch in a sodium hydroxide solution with a pH of 11 to form a porous starch dispersion, then adding 5 parts of epichlorohydrin, stirring in a constant temperature water bath at 25° C. for 5 hours, and obtaining porous cross-linked starch after centrifugal washing and drying;

[0047] 3) dispersing 100 parts of porous cross-linked starch in a sodium hydrogen phosphate-citric acid buffer solution to form a porous cross-linked starch dispersion, adjusting the pH to 5, adding 60 parts of hydrogen peroxide, stirring in a constant temperature water bath at 45° C. for 3 hours, then adding 6 parts of sodium thiosulfate to terminate the reaction, and obtaining porous oxidized starch after centrifugal washing and drying;

[0048] 4) dispersing 100 parts of porous oxidized starch in a disodium hydrogen phosphate-citric acid buffer solution to form a porous oxidized starch dispersion, adjusting the pH to 7, adding 50 parts of diethylenetriamine, stirring in a constant temperature water bath at 45° C. for 3 hours, and washing by centrifugation and drying to obtain porous amino starch;

[0049] In the above operation, centrifugation is specifically: centrifugation at a speed of 4000 r / min for 5 minutes; washing and drying are specifically: washing with deionized water for 3 times, centrifuging again after each washing, and then drying at 60° C. for 12 hours.

[0050] Example 3

[0051] 1) Dispersing 100 parts of starch (potato starch) in a sodium hydrogen phosphate-citric acid buffer solution with a pH of 4 to form a starch dispersion, adding 5 parts of biological enzymes (β-amylase and isoamylase weight ratio of 2:1), stirring in a constant temperature water bath at 60° C. for 8 hours, then adding 10 parts of sodium hydroxide solution (concentration of 1 mol / L) to terminate the reaction, and obtaining porous starch after centrifugal washing and drying;

[0052] 2) dispersing 100 parts of the prepared porous starch in a sodium hydroxide solution with a pH of 11 to form a porous starch dispersion, then adding 5 parts of epichlorohydrin, stirring in a constant temperature water bath at 25° C. for 5 hours, and obtaining porous cross-linked starch after centrifugal washing and drying;

[0053] 3) dispersing 100 parts of porous cross-linked starch in a sodium hydrogen phosphate-citric acid buffer solution to form a porous cross-linked starch dispersion, adjusting the pH to 5, adding 60 parts of hydrogen peroxide, stirring in a constant temperature water bath at 45° C. for 3 hours, then adding 6 parts of sodium thiosulfate to terminate the reaction, and obtaining porous oxidized starch after centrifugal washing and drying;

[0054] 4) dispersing 100 parts of porous oxidized starch in a sodium hydrogen phosphate-citric acid buffer solution to form a porous oxidized starch dispersion, adjusting the pH to 7, adding 60 parts of diethylenetriamine, stirring in a constant temperature water bath at 45° C. for 3 hours, and washing by centrifugation and drying to obtain porous amino starch;

[0055] In the above operation, centrifugation is specifically: centrifugation at a speed of 4000 r / min for 5 minutes; washing and drying are specifically: washing with deionized water for 3 times, centrifuging again after each washing, and then drying at 60° C. for 12 hours.

[0056] In order to demonstrate the excellent effect of the present invention, the raw material natural starch (corn starch) was selected as comparative example 1 and compared with the above-mentioned embodiment 1.

[0057] XRD test, SEM test, FTIR test, adsorption test and safety test were performed on Example 1 and Comparative Example 1 respectively. The adsorption test method is as follows: the example sample and the comparative example sample were placed in a Mettler ToledoTGDSC 3+ synchronous thermal analyzer respectively, first heated to 150°C under a nitrogen atmosphere, kept constant temperature until the mass was stable, then cooled to 70°C, introduced a mixed atmosphere of nitrogen and phenol, kept constant temperature until the mass was stable, and compared the mass changes before and after adsorption. The results are as follows Figure 1-5 shown.

[0058] pass Figure 1 From the XRD test results, it can be found that the peaks of the XRD spectrum curves of natural starch and biological / chemically aminated modified starch are exactly the same, and the peak intensities are also exactly the same. There are strong diffraction peaks at 15°, 17°, 18° and 23°, showing a typical starch crystal form, indicating that biological / chemical aminated modification does not affect the crystal structure and crystal form of starch.

[0059] pass Figure 2 The SEM test results show that there are obvious differences in the morphology of natural starch and biological / chemically aminated modified starch particles. The surface of natural starch particles is smooth and compact, with some inconspicuous depressions and irregular polygons, but basically no holes. Most of the particles are irregular, with relatively gentle edges and corners. Many small holes appear on the surface and inside of the starch modified by biological / chemical amination, distributed on the entire surface of the particles, and present a honeycomb hollow structure. In addition, the edges and corners of the modified starch become blurred from sharp, and the starch particles become smoother as a whole.

[0060] pass Figure 3 The FTIR test results show that the positions of the corresponding peaks of the spectra of natural starch and biological / chemically aminated modified starch are almost the same, indicating that no new functional groups are generated during the preparation of biological / chemically aminated modified starch, but the biological / chemically aminated modified starch has a peak at 3300cm -1 and 1650cm -1 The characteristic absorption peak of amino-NH2 at the wavenumber was enhanced, indicating that the amino group was successfully introduced into the product.

[0061] pass Figure 4-5The adsorption test results show that the modified starch shown in Example 1 has a stable mass of 0.8941g, i.e. a=0.8941g, at a constant temperature of 150°C, and is cooled to 70°C. At the same time, a mixed atmosphere of nitrogen and phenol is introduced. After 897s, the mass is stable at 0.9120g, i.e. b=0.9120g, and the adsorption amount is 2.00%; while the natural starch shown in Comparative Example 1 has a stable mass of 0.9112g, i.e. a=0.9112g, at a constant temperature of 150°C, and is cooled to 70°C. At the same time, a mixed atmosphere of nitrogen and phenol is introduced. After 1175s, the mass is stable at 0.9265g, i.e. b=0.9265g, and the adsorption amount is 1.68%. By comparing the adsorption amounts of the two, it can be seen that the modified starch provided by the present invention has significantly improved adsorption properties and adsorption rate.

[0062] In summary, the adsorption performance of the modified starch provided by the present invention is better than that of Comparative Example 1. By introducing amino groups on the basis of the porous starch prepared by the bioenzymatic method, effective adsorption of harmful substances such as phenol and tar in flue gas can be achieved.

[0063] Example 4

[0064] 1) Dispersing 100 parts of starch (corn starch) by weight in a sodium hydrogen phosphate-citric acid buffer solution with a pH of 4.5 to form a starch dispersion, adding 1 part of a biological enzyme (α-amylase), stirring in a constant temperature water bath at 25° C. for 3 hours, then adding a sodium hydroxide solution (concentration of 1 mol / L) to adjust the pH to neutral to terminate the reaction, and obtaining porous starch after centrifugal washing and drying;

[0065] 2) dispersing 100 parts of the prepared porous starch in a sodium hydroxide solution with a pH of 11.5 to form a porous starch dispersion, then adding 8 parts of epichlorohydrin, stirring in a constant temperature water bath at 30° C. for 6 hours, and obtaining porous cross-linked starch after centrifugal washing and drying;

[0066] 3) dispersing 100 parts of porous cross-linked starch in a sodium hydrogen phosphate-citric acid buffer solution to form a porous cross-linked starch dispersion, adjusting the pH to 5.5, adding 65 parts of hydrogen peroxide, stirring in a constant temperature water bath at 48° C. for 4 hours, then adding 8 parts of sodium thiosulfate to terminate the reaction, and obtaining porous oxidized starch after centrifugal washing and drying;

[0067] 4) dispersing 100 parts of porous oxidized starch in a disodium hydrogen phosphate-citric acid buffer solution to form a porous oxidized starch dispersion, adjusting the pH to 7, adding 40 parts of diethylenetriamine, stirring in a constant temperature water bath at 48° C. for 4 hours, and washing by centrifugation and drying to obtain porous amino starch;

[0068] In the above operation, centrifugation is specifically: centrifugation at a speed of 4500 r / min for 8 minutes; washing and drying are specifically: washing with deionized water for 3 times, centrifuging again after each washing, and then drying at 62° C. for 14 hours.

[0069] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing modified starch for absorbing harmful substances in flue gas, characterized in that: The following steps are involved: 1) dispersing starch in a buffer solution with a pH of 4-5 to form a starch dispersion, adding a biological enzyme for enzymolysis, then adding an alkali to terminate the reaction, centrifuging, washing and drying to obtain porous starch; the enzymolysis is carried out in a constant temperature water bath at 25-60° C. for 3-8 hours; 2) dispersing the porous starch in a sodium hydroxide solution with a pH of 11-12 to form a porous starch dispersion, adding epichlorohydrin, reacting in a constant temperature water bath at 25-30° C. for 5-6 hours, centrifuging, washing and drying to obtain a porous cross-linked starch; 3) dispersing the porous cross-linked starch in an acidic buffer solution to form a porous cross-linked starch dispersion, adjusting the pH to 5-6, adding hydrogen peroxide, reacting in a constant temperature water bath at 45-50° C. for 3-4 hours, adding sodium thiosulfate to terminate the reaction, centrifuging, washing and drying to obtain porous oxidized starch; 4) dispersing the porous oxidized starch in a liquid, reacting with diethylenetriamine, centrifuging, washing and drying to obtain the porous amino starch; The starch is made from one or more of corn, wheat, potato, and cassava; the biological enzyme is one or more of α-amylase, β-amylase, γ-amylase, isoamylase, and saccharifying enzyme; the weight ratio of starch to biological enzyme is 100:(1-5); In step 2), the weight ratio of porous starch to epichlorohydrin is 100:(5-8); In step 3), the weight ratio of porous cross-linked starch to hydrogen peroxide is 100:(60-65); In step 4), the weight ratio of porous oxidized starch to diethylenetriamine is 100:(40-60).

2. The method for preparing modified starch according to claim 1, characterized in that: The porous oxidized starch is dispersed in a buffer solution, the pH is adjusted to neutral, diethylenetriamine is added, and the reaction is carried out in a constant temperature water bath of 45-50° C. for 3-4 hours, and the reaction is centrifuged, washed and dried to obtain the porous amino starch.

3. The method for preparing modified starch according to claim 1, characterized in that: The centrifugation is specifically as follows: centrifugation at a speed of 4000-5000 r / min for 5-10 min.

4. The method for preparing modified starch according to claim 3, characterized in that: The washing and drying are specifically as follows: washing with deionized water for 2-3 times, centrifuging again after each washing, and then drying at 60-65° C. for 12-14 hours.

5. The modified starch obtained by the preparation method according to any one of claims 1 to 4.

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