A method for deactivating a modified starch and cyclododecatriene synthesis reaction solution

Abstract

The invention discloses a method for deactivating an active catalyst of a modified starch and cyclododecatriene (CDT) reaction liquid. The method uses starch molecules as a skeleton, and obtains a modified starch containing hydroxyl and amino groups on a molecular chain through gelatinization reaction, oxidation reaction and amino modification reaction. The modified starch is used as a quencher to deactivate the active catalytic groups in the reaction liquid, and the active catalytic groups can be removed by a simple centrifugal filtration physical operation, thereby improving the stability of the CDT product and realizing low-cost, continuous and stable operation of the device.

Description

Technical Field

[0001] The invention relates to the field of chemical industry, and in particular to a modified starch and a method for deactivating an active catalyst of a cyclododecatriene (CDT) reaction liquid by using the modified starch. Background Art

[0002] Cyclododecatriene (CDT) is an important chemical raw material for the synthesis of nylon dodecacarbon. In addition, it can also be used to produce flame retardants (hexabromocyclododecane, HBCD), fragrances (cyclododecanol, CDON) and other products.

[0003] In the prior art, 1,3-butadiene (BD) is often used in industry to prepare cyclododecatriene through trimerization liquid phase reaction. The catalyst is generally a Ziegler-Natta system. Titanium compounds are often used as the main catalytic agent in industry, and a certain proportion of organic aluminum compounds are added as co-catalysts. In addition, a small amount of auxiliary agents are added to provide electrons to improve catalytic activity. Usually, the catalyst needs to be quenched after the reaction to prevent the catalyst from continuing to catalyze the side reactions of cyclododecatriene to generate isomeric products or polymer products that are difficult to separate, affecting the product yield and quality.

[0004] The Invista CDT unit in the United States uses ammonia to deactivate aluminum-titanium catalysts. The deactivated catalyst has the problem of evaporation of amide aluminum chloride complex during the heating process, and needs to be treated with a two-stage scraper to remove the catalyst. Repeated experiments have shown that the pre-cooling of the evaporating gas during the deweighting process of the ammonia quenching reaction liquid will precipitate solids to clog the scraper. In addition, the scraper deweighting area required for this scheme is relatively large. Usually, a CDT production capacity of 10,000 tons requires a scraper area of ​​>25m 2 The equipment cost is high, and the quenching product contains solids that are easy to clog the equipment, making it difficult to achieve long-term stable operation.

[0005] In the Chinese patent CN105793214A, a method for treating a CDT reaction liquid containing a catalyst deactivated after ammonia quenching is disclosed, in which water is added for secondary deactivation of the catalyst, and the catalyst is removed by filtration and evaporation. However, the Ziegler-Natta catalyst used in the CDT reaction system needs to strictly control the water content during the reaction. Excessive water content will lead to reduced catalyst activity or even complete failure. The water content usually allowed is ppm level. The introduction of water here will be accompanied by the evaporation of the solvent during the evaporation process. Sufficient fractionation and distillation methods are required to ensure that the water content in the recycled solvent is qualified. It is even necessary to introduce other water removal measures such as molecular sieves to remove trace amounts of water, and the process cost is relatively high.

[0006] Chinese patent publication CN111153761A discloses a catalyst solution using a quencher combined with a chelating resin tower for secondary adsorption. However, it is difficult to regenerate the resin tower after it is saturated with adsorption.

[0007] Other quenching schemes, such as the use of small molecule quenchers such as ethanol, usually have weak binding forces between hydroxyl groups and aluminum-titanium active centers, and can only play a deactivation role, but it is difficult to achieve complete inactivation. Subsequent separation requires the removal of the catalyst first to prevent the residual catalyst activity in the distillation process from continuing to catalyze the product to undergo side reactions. In addition, it is difficult to completely separate small molecule quenchers from conventional solvents (toluene, etc.), and there is a problem of quencher entrainment when the solvent is fully reused, which will affect the reaction activity. Part of the solvent needs to be discharged regularly to prevent the accumulation of the inactivator, and the long-term operation cost is high.

[0008] Therefore, how to efficiently deactivate the catalyst and simply and cost-effectively remove the introduced quencher is an urgent optimization item for the long-term stable operation of this process. Summary of the invention

[0009] The purpose of the present invention is to provide a modified starch, which modifies the starch skeleton and can be used as a quencher to effectively inactivate the active groups in the catalyst. The catalyst and the modified starch can be removed by a simple physical operation of centrifugal filtration.

[0010] Another object of the present invention is to provide a post-treatment method for an active catalyst in a reaction solution containing cyclododecatriene (CDT), using modified starch as a quencher to effectively inactivate the active groups in the catalyst, improve the stability of the CDT product, and achieve low-cost, continuous and stable operation of the device.

[0011] In order to achieve the above technical effects, the specific technical solutions of the present invention are as follows:

[0012] A modified starch comprises hydroxyl and amino groups, wherein the hydroxyl and amino groups are obtained by taking starch molecules as the skeleton through gelatinization reaction, oxidation reaction and amino modification reaction.

[0013] In the present invention, the gelatinization reaction temperature is 75-100° C., preferably 80-95° C., and the gelatinization time is 20-60 min, preferably 30-45 min.

[0014] In the present invention, the oxidant in the oxidation reaction is selected from one or more of sodium hypochlorite aqueous solution and potassium hypochlorite aqueous solution, preferably sodium hypochlorite aqueous solution. Based on 100g of starch, the mass concentration of the oxidant is 5-20%, the dosage is 20-200mL, and the preferred dosage is 80-150mL.

[0015] In the present invention, the amine compound for the amino modification reaction is preferably ethylenediamine, hexamethylenediamine, and ethanolamine. Based on 100g of starch, the amount of solvent added is 400-600g, the amount of amine compound added is 50-150g, the reaction temperature of the amino modification reaction is 20-60°C, preferably 30-50°C, the reaction time is 1-3h, preferably 1.5-2h, and the reaction pH is 5-8, preferably 6-7.

[0016] As a preferred solution, the method for preparing modified starch comprises the following steps:

[0017] (1) Starch is dissolved in water to form a slurry, a pH adjuster is added to adjust the pH to 5 to 8, preferably 6 to 7, and the temperature is raised for gelatinization. After gelatinization, an oxidant is added dropwise for oxidation reaction to obtain oxidized starch.

[0018] (2) An amine compound is added to the oxidized starch to carry out an amino modification reaction to obtain amino-modified oxidized starch.

[0019] (3) After the reaction is completed, the reaction liquid slurry obtained in step (2) is added to a spray dryer for drying to obtain dried solid particles.

[0020] Preferably, in step (1), the mass ratio of starch to water is 1:2 to 1:6, preferably 1:3 to 1:5, the pH regulator is an acid or a base, the acid is one or more of hydrochloric acid, sulfuric acid, and acetic acid, the base is one or more of sodium hydroxide, potassium hydroxide, and ammonia water, the gelatinization temperature is 75 to 100°C, preferably 80 to 95°C, and the gelatinization time is 20 to 60 minutes, preferably 30 to 45 minutes. The oxidant is selected from one or more of sodium hypochlorite aqueous solution and potassium hypochlorite aqueous solution, preferably sodium hypochlorite aqueous solution. Based on 100g of starch, the mass concentration of the oxidant is 5 to 20%, the amount is 20 to 200mL, and the preferred amount is 80 to 150mL. The reaction temperature of the oxidation reaction is 20 to 60°C, preferably 30 to 50°C; the reaction time is controlled to be 0.5 to 2h, preferably 1 to 1.5h.

[0021] Preferably, the oxidized starch is dissolved in a solvent before the amine compound is added. In step (2), the solvent is one or two of ethylene glycol and ethanol. The amine compound is preferably one or more of ethylenediamine, hexamethylenediamine and ethanolamine. Based on 100g of starch, the amount of solvent added is 400-600g, the amount of amine compound added is 50-150g, the reaction temperature of the amino modification reaction is 20-60°C, preferably 30-50°C, the reaction time is 1-3h, preferably 1.5-2h, and the reaction pH is 5-8, preferably 6-7.

[0022] Preferably, the drying temperature of the spray drying is 80 to 150° C., preferably 100 to 120° C., and the drying time is 1 to 10 min, preferably 3 to 7 min.

[0023] A method for inactivating a cyclododecatriene reaction solution comprises the following steps: adding a modified starch quencher to the cyclododecatriene (CDT) reaction solution and mixing the mixture thoroughly.

[0024] The cyclododecatriene (CDT) reaction liquid contains a catalyst of an organic aluminum and a titanium compound, preferably the organic aluminum compound is selected from one or more of Al2(C2H5)6, Al2Cl3(C2H5)3 and AlCl(C2H5)2, and the titanium compound is selected from one or more of titanium tetrachloride and titanium acetylacetonate. The quenching reaction is carried out in a quenching kettle, and the quenching kettle is provided with stirring, and the stirring form is set to a shearing paddle and / or an axial flow paddle, preferably a lower three-wide blade inclined paddle combined with an upper three-blade swept paddle. The amount of modified starch used is (1g~100g) / 1kg of reaction liquid, and the preferred amount is (3g~20g) / 1kg of reaction liquid.

[0025] The reaction temperature of the quenching reactor is controlled to be 25-90°C, preferably 40-60°C; the reaction pressure is controlled to be 1-3 barG, preferably 1-2 barG, and the quenching reaction time is 10-100 min, preferably 30-60 min.

[0026] As a preferred solution, the process further includes centrifuging and / or filtering to remove solids after quenching.

[0027] The post-treatment method of the quenched liquid can be centrifugation and / or filtration, preferably a centrifugal combined filtration method, more preferably a solid removal method of a centrifuge combined with candle filtration.

[0028] The quenched reaction liquid first enters the centrifuge to concentrate the modified starch, and the concentrate is then filtered by candle to form a filter cake layer to further recover CDT in the wet material and improve the product yield. The operating temperature of centrifugation and filtration is consistent with the quenching temperature, and no cooling treatment is required.

[0029] Compared with the prior art solutions, the advantages of the present invention are as follows:

[0030] (1) The modified starch proposed in the present invention has the characteristics of large particle size, multiple pores, multiple depressions, and rough surface, and can fully contact and react with the reaction solution; at the same time, during the reaction process, the modified starch introduces amino groups into the starch molecules, and the polyhydroxyl groups of the starch molecules combined with the amino groups enhance the coordination binding force with the aluminum and titanium active centers in the catalyst, thereby enhancing the quenching effect.

[0031] (2) The reaction liquid after quenching is relatively stable. The quenching product is insoluble in the reaction liquid and can be removed by simple solid removal methods. The subsequent separation operation does not need to remove the catalyst first. The solvent can be removed first and then the product can be refined, and the product separation cost is low.

[0032] (3) Quenching raw materials are widely available, non-toxic, and low in cost; waste solids are easily biodegradable and environmentally friendly. DETAILED DESCRIPTION

[0033] The present invention is explained in more detail with reference to the following examples, which do not limit the scope of the present invention.

[0034] The present invention relates to reagents and samples as follows:

[0035] Cyclododecatriene (CDT) reaction liquid: produced by the device, the composition is: 47% toluene, 45% CDT, 2% vinylcyclohexene, 2% cyclooctadiene, 500ppm Ziegler-Natta catalyst (titanium tetrachloride-triethylaluminum) component, and the rest are heavy components such as polymers.

[0036] Starch: food grade corn starch, Binzhou Jinhui Corn Development Co., Ltd.;

[0037] Sodium hydroxide (AR), hydrochloric acid (AR), sodium hypochlorite solution (10% m / v, AR), potassium hypochlorite solution (10% m / v, AR), ethylenediamine (AR), hexamethylenediamine (AR), ethanolamine (AR), anhydrous ethanol (AR), ethylene glycol (AR), the above reagents were purchased from the official website of Aladdin Reagent.

[0038] The CDT loss rate is calculated using the following formula:

[0039] CDT loss rate % = (CDT initial mass - CDT mass after heating experiment) / CDT initial mass * 100%

[0040] The present invention adopts the following instrument conditions:

[0041] GC analysis instrument and conditions Instrument model: Shimadzu 2010PLUS; Chromatographic column: DB-5 (30m×0.25mm×0.25μm); Temperature program: 50°C for 2min, increase the temperature to 80°C at 5°C / min, maintain for 10min, then increase the temperature to 300°C at 20°C / min, maintain for 15min; Inlet temperature: 280°C; FID detector temperature: 300°C; Split ratio 30:1.

[0042] Example 1

[0043] Take 100g of starch, add 350g of water and start stirring, prepare the starch liquid into slurry, and use 1mol / L HCl to adjust the pH to 5. Gelatinize at 90℃ for 30min. Add 50mL of 10% (w / v) NaClO for oxidation. Control the reaction temperature to 50℃ and the reaction time to 1h. Add 500g of ethylene glycol as the reaction solvent to the above reaction solution, add 70g of ethylenediamine for reaction, and control the reaction time to 1.5h.

[0044] After the reaction was completed, the reaction liquid slurry was added into a spray dryer, and the drying temperature was controlled at 120° C. and the drying time was 5 min to obtain dried solid particles.

[0045] Example 2

[0046] Take 100g of starch, add 350g of water and start stirring, prepare the starch liquid into slurry, and use 1mol / L HCl to adjust the pH to 6. Gelatinize at 90℃ for 30min. Add 50mL of 10% (w / v) KClO for oxidation. Control the reaction temperature to 50℃ and the reaction time to 1.5h. Add 600g of ethanol as the reaction solvent to the above reaction solution, add 140g of ethanolamine for reaction, and control the reaction time to 2h.

[0047] After the reaction was completed, the reaction liquid slurry was added into a spray dryer, and the drying temperature was controlled at 120° C. and the drying time was 5 min to obtain dried solid particles.

[0048] Example 3

[0049] Take 100g of starch, add 350g of water and start stirring, prepare the starch liquid into slurry, and use 1mol / L NaOH to adjust the pH to 8. Gelatinize at 90℃ for 30min. Add 140mL of 10% (w / v) NaClO for oxidation. Control the reaction temperature to 50℃ and the reaction time to 1.5h. Add 600g of ethanol as the reaction solvent to the above reaction liquid, add 130g of hexamethylenediamine for reaction, and control the reaction time to 1.8h.

[0050] After the reaction was completed, the reaction solution slurries of Examples 1-3 were respectively added into a spray dryer, and the drying temperature was controlled at 120° C. and the drying time was 5 min to obtain dried solid particles.

[0051] Example 4

[0052] A 10L reactor was used as a quenching reaction vessel, and a stirring paddle was set. A three-wide blade oblique propeller was used for the lower layer, and a three-blade swept propeller was used for the upper layer. The speed of the stirring kettle was maintained at 300rpm, and the reaction solution was added at one time, with a total amount of 5kg. Stirring was turned on, and 20g of the modified starch obtained in Example 1-3 was added to carry out the quenching reaction. The temperature of the quenching kettle was controlled to 60°C and the pressure to 1barG. After reacting for 1h, an inactivated reaction solution was obtained. The reaction solution was heated to 180°C, kept warm for 48h, and sampled for analysis to track the effect of the quenching reaction. The samples were analyzed for CDT loss using GC.

[0053] Example 5

[0054] A 10L reactor was used as a quenching reaction vessel, and a stirring paddle was set. A three-wide blade oblique propeller was used for the lower layer, and a three-blade swept propeller was used for the upper layer. The speed of the stirring kettle was maintained at 300rpm, and the reaction solution was added at one time, with a total amount of 5kg. Stirring was turned on, and 50g of the modified starch obtained in Example 1-3 was added to carry out the quenching reaction. The temperature of the quenching kettle was controlled to 50°C and the pressure to 1barG. After reacting for 0.75h, an inactivated reaction solution was obtained. The reaction solution was heated to 180°C, kept warm for 48h, and sampled for analysis to track the effect of the quenching reaction. The samples were analyzed for CDT loss using GC.

[0055] The quenched reaction solution in Example 4 and Example 5 can be concentrated by a disc centrifuge, and the heavy phase composition is a starch solution in which CDT accounts for 50%. The heavy phase concentrate is then filtered by candle filtration to form a filter cake layer, and CDT in the wet material is further recovered to improve the product yield. The light phase of the centrifuged and the light phase of the filter enter the subsequent separation system for separation operations such as desolventization to purify CDT.

[0056] Comparative Example 1

[0057] A 10L reactor was used as the quenching reaction vessel. A stirring paddle was set up, with a three-blade inclined paddle on the lower layer and a three-blade swept paddle on the upper layer. The stirring kettle speed was maintained at 300rpm. The reaction liquid was added at one time, with a total amount of 5kg. Stirring was turned on, and 20g of ethanol was added to quench the reaction. The temperature of the quenching kettle was controlled to 60℃ and the pressure to 1barG. After reacting for 1h, the inactivated reaction liquid was obtained. The reaction liquid was heated to 180℃, kept warm for 48h, and samples were taken to analyze the CDT loss.

[0058] Comparative Example 2

[0059] Ammonia is introduced as a quenching agent: A 10L reactor is used as a quenching reaction vessel, and a stirring paddle is set, with a three-blade inclined paddle on the lower layer and a three-blade swept paddle on the upper layer. The stirring kettle speed is maintained at 300rpm, and the reaction liquid is added at one time, with a total amount of 5kg. Turn on the stirring, add 15g of ammonia, and quench the reaction. Control the temperature of the quenching kettle to 50℃ and the pressure to 2barG. After reacting for 1h, the inactivated reaction liquid is obtained. Heat the reaction liquid to 180℃, keep it warm for 48h, and take samples to analyze the CDT loss.

[0060] Table 1 CDT loss rate of products in Examples / Comparative Examples

[0061] Examples and Comparative Examples CDT Loss Rate % Example 4 (using modified starch of Example 1) 0.95 Example 4 (using modified starch from Example 2) 0.75 Example 4 (using modified starch of Example 3) 0.51 Example 5 (using modified starch of Example 1) 0.46 Example 5 (using modified starch from Example 2) 0.52 Example 5 (using modified starch from Example 3) 0.28 Comparative Example 1 3.11 Comparative Example 2 2.20

[0062] It can be seen from the above table that, compared with the existing ammonia and water quenchers, the modified starch quencher of the present invention has a low CDT loss rate after quenching, the reaction solution is stable, and the quenching product is insoluble in the reaction solution and can be removed by simple solid removal means.

Claims

1. A method for deactivating a cyclododecatriene reaction solution, characterized in that: The method comprises the following steps: adding a modified starch quencher to a cyclododecatriene (CDT) reaction solution and mixing the mixture thoroughly to perform a quenching reaction; and after the quenching is completed, performing a centrifugal and / or filtering treatment to remove solids. The modified starch molecular chain comprises hydroxyl and amino groups, and the hydroxyl and amino groups are obtained by gelatinization reaction, oxidation reaction and amino modification reaction with starch molecules as the skeleton. The cyclododecatriene (CDT) reaction solution comprises a catalyst of organic aluminum and titanium compounds.

2. The inactivation method according to claim 1, characterized in that The preparation method of modified starch comprises the following steps: (1) dissolving starch in water to form a slurry, adding a pH adjuster to adjust the pH to 5-8, and heating to gelatinize; after the gelatinization is completed, an oxidant is added dropwise to perform an oxidation reaction to obtain oxidized starch; (2) adding an amine compound to the oxidized starch to carry out an amino modification reaction to obtain an amino-modified oxidized starch; (3) After the amino modification reaction is completed, the reaction liquid slurry obtained in step (2) is dried to obtain dried solid particles.

3. The inactivation method according to claim 2, characterized in that: In step (1), the pH regulator is an acid or a base, the acid is selected from one or more of hydrochloric acid, sulfuric acid, and acetic acid, the base is selected from one or more of sodium hydroxide, potassium hydroxide, and ammonia water, and / or the oxidant is selected from one or more of sodium hypochlorite aqueous solution and potassium hypochlorite aqueous solution.

4. The inactivation method according to claim 2 or 3, characterized in that: In the step (1), the mass ratio of starch to water is 1:2-1:6; the gelatinization temperature is 75-100°C, and the gelatinization time is 20-60 min; and / or the mass concentration of the oxidant is 5-20%, and the amount of the oxidant is 20-200 mL based on 100 g of starch; the reaction temperature of the oxidation reaction is 20-60°C; and the reaction time is 0.5-2 h.

5. The inactivation method according to claim 4, characterized in that: In the step (1), the mass ratio of starch to water is 1:3-1:5; the gelatinization temperature is 80-95°C, and the gelatinization time is 30-45min; and / or the amount of the oxidant is 80-150mL; the reaction temperature of the oxidation reaction is 30-50°C; and the reaction time is 1-1.5h.

6. The inactivation method according to claim 2 or 3, characterized in that: In the step (2), before adding the amine compound, the oxidized starch is first dissolved with a solvent, the solvent is one or two of ethylene glycol and ethanol, the amine compound is selected from one or more of ethylenediamine, hexamethylenediamine, and ethanolamine, and / or, based on 100g of starch, the amount of solvent added in the step (2) is 400-600g, the amount of amine compound added is 50-150g, and / or, the reaction temperature of the amino modification reaction is 20-60°C, the reaction time is 1-3h, and the reaction pH is 5-8.

7. The inactivation method according to claim 2 or 3, characterized in that: The drying method in step (3) is spray drying, the drying temperature is 80-150° C., and the drying time is 1-10 min.

8. The inactivation method according to any one of claims 1 to 3, characterized in that: The amount of modified starch used is (1g-100g) / 1kg of cyclododecatriene reaction solution; and / or, the quenching reaction temperature is 25-90°C; the quenching reaction pressure is 1-3 barG, and the quenching reaction time is 10-100min.

9. The inactivation method according to claim 8, characterized in that: The amount of modified starch used is (3g-20g) / 1kg of cyclododecatriene reaction solution; and / or, the quenching reaction temperature is 40-60°C; the quenching reaction pressure is 1-2 barG, and the quenching reaction time is 30-60min.

10. The inactivation method according to any one of claims 1 to 3, characterized in that: The organic aluminum compound is selected from one or more of Al2(C2H5)6, Al2Cl3(C2H5)3 and AlCl(C2H5)2, and the titanium compound is selected from one or more of titanium tetrachloride and titanium acetylacetonate.

11. The inactivation method according to any one of claims 1 to 3, characterized in that: The quenching reaction is carried out in a quenching kettle, and after the quenching is completed, the solid is removed by a centrifugal combined filtration method.