A green and efficient preparation process of OB acid for fluorescent whitening agent

Abstract

The present invention discloses a green and efficient preparation process of OB acid for fluorescent whitening agent. Specifically, it includes: monochlorination: mixing adipic acid and o-dichlorobenzene, passing chlorine gas to react, neutralizing and separating to obtain a neutralized solution; sulfidation: adding sodium sulfide to the neutralized solution, and controlling the conditions to carry out sulfidation reaction; dichlorination: cooling the product after sulfidation, passing chlorine gas to carry out dichlorination, and generating a target crude product; refining: dissolving the crude product, adjusting the pH, adding an adsorbent for decolorization, and filtering after acid precipitation to obtain a filter cake; drying: drying the filter cake, crushing and packaging to obtain an OB acid product. Compared with the numerous process flows of the prior art, such as dehydration, chlorination, hydrogenation, hydrolysis, sulfidation and oxidation, the preparation process of the present invention is green and efficient, with less pollution and fewer environmental problems.

Description

Technical Field

[0001] The invention relates to the technical field of synthesis of heterocyclic compounds, in particular to a green and efficient preparation process of OB acid for fluorescent whitening agent. Background Art

[0002] Fluorescent whitening agent OB is a chemical additive used to improve the whiteness and brightness of materials such as textiles, paper, and plastic products. It supplements the natural white spectrum of the material by absorbing ultraviolet light and emitting blue light, making the material look brighter and whiter. OB acid, the full name of which is 2,5-thiophenedicarboxylic acid, is an intermediate of fluorescent whitening agent OB and a key raw material for the synthesis of this whitening agent.

[0003] CN105906606A introduces a method for preparing OB acid, which comprises mixing adipic acid and thionyl chloride, adding a catalyst, reacting to generate an acyl chloride; hydrolyzing the acyl chloride, adjusting the pH, and obtaining a solid product; decolorizing and filtering to obtain a filtrate; acidifying with hydrochloric acid, centrifuging to obtain a crude product; refining the crude product, reflux filtering to obtain a refined product; drying and crushing the refined product to obtain a final product. The catalyst for the reaction is at least one of 3,5-lutidine, 2,6-lutidine, and 4-dimethylaminopyridine; or the catalyst is a combination of at least one of 3,5-lutidine, 2,6-lutidine, and 4-dimethylaminopyridine and pyridine. The use of reagents such as pyridine is likely to cause serious water pollution and does not meet environmental protection requirements. Summary of the invention

[0004] In view of the above-mentioned defects of the prior art, the present invention provides a green and efficient preparation process of OB acid for fluorescent whitening agent, which is more environmentally friendly, less polluting, and has no environmental problems. The simplification of the process steps can reduce the complexity and potential errors in the production process, and can also reduce production costs and improve efficiency.

[0005] The specific technical solutions are as follows:

[0006] A green and efficient preparation process of OB acid for fluorescent whitening agent comprises the following steps:

[0007] (1) Chloride

[0008] After adipic acid and o-dichlorobenzene are mixed evenly, the temperature is raised to 135-137°C and chlorine is introduced, and the reaction temperature is controlled at 135-137°C; after natural cooling, a 20-40wt% sodium carbonate aqueous solution is used to adjust the pH to 8.5-9.5; diatomaceous earth is added and stirred for 5-15 minutes, and insoluble matter and mechanical impurities are removed by centrifugation. After the filtrate is allowed to stand for 1-3 hours, stratification begins, and the upper neutralized liquid is taken for sulfurization;

[0009] (2) Vulcanization

[0010] At 30-35°C, add sodium sulfide solid to the upper neutralized liquid in batches until the pH stabilizes at 8-9; raise the temperature to 55-60°C, and continue to keep the temperature for 1-3 hours to obtain a sulfide liquid;

[0011] (3) Dichloride

[0012] The sulfide liquid is adjusted to pH 1-2 with hydrochloric acid at 0-30°C; cooled to -5~0°C, and chlorine is introduced at -5~0°C; then the temperature is raised to 96-100°C and kept warm for 1-3h; then the temperature is lowered to 20-25°C and kept warm for 0.5-2h, and the crude product is discharged and filtered;

[0013] (4) Refining

[0014] Mix the crude product and 30wt% sodium carbonate aqueous solution evenly, heat to 75-80℃ to ensure that the crude product is completely dissolved; then add diatomaceous earth and activated carbon, stir at 80-95℃ for 15-40 minutes, and filter press to decolorize;

[0015] The filtrate is treated with 30wt% hydrochloric acid at 80-95℃ to a pH of 1-2, cooled to 15-20℃, and kept warm for 0.5-2h; suction filtration is started, and the filter cake is washed with water until the pH reaches 6-7;

[0016] (5) Drying

[0017] The filter cake is dried at 100-110° C., crushed and packaged to obtain the OB acid for the fluorescent whitening agent.

[0018] Preferably, the green and efficient preparation process of OB acid for fluorescent whitening agent comprises the following steps:

[0019] (1) Chloride

[0020] 500-700 parts by weight of adipic acid and 2000-3000 parts by weight of o-dichlorobenzene are added to a reaction kettle, stirred evenly, heated to 135-137°C, chlorine is introduced, and the HCl absorption device is turned on. The reaction temperature is controlled at 135-137°C, and the reaction is carried out for 10-30 minutes. The material is transferred to an alkali-soluble neutralization kettle while hot; naturally cooled until the temperature drops to 10-30°C, and a 20-40wt% sodium carbonate aqueous solution is used to pH 8.5-9.5; 10-30 parts by weight of diatomaceous earth are added and stirred for 5-15 minutes, and the insoluble matter and mechanical impurities are removed by centrifugation, and the filtrate is sent to a stratification kettle; after standing for 1-3 hours, stratification begins, the lower mother liquor is sent to the mother liquor tank to be applied to monochlorine, and the upper neutralization liquid is transferred to a vulcanization kettle for vulcanization;

[0021] (2) Vulcanization

[0022] At 30-35°C, add sodium sulfide solid in batches to the upper neutralization liquid until the pH stabilizes at 8-9; raise the temperature to 55-60°C, continue to keep the temperature for 1-3 hours (during which the hydrogen sulfide tail gas absorption device is kept in normal operation), and transfer the sulfide liquid to the dichlorination kettle;

[0023] (3) Dichloride

[0024] The sulfide liquid is adjusted to pH 1-2 with hydrochloric acid at 0-30°C; after cooling to 0°C, the external circulation cooling device is turned on and the temperature is further lowered to -5°C; at -5~0°C, chlorine is passed for 10-20 minutes; then the temperature is raised to 96-100°C and kept warm for 2 hours; then the temperature is lowered to 20-25°C and kept warm for 0.5-2 hours, and the crude product is discharged and filtered (during which the hydrogen chloride tail gas absorption device is kept in normal operation);

[0025] (4) Refining

[0026] The crude product and 30wt% sodium carbonate aqueous solution are mixed evenly, and the temperature is raised to 75-80°C to ensure that the crude product is completely dissolved; then 10-30 parts by weight of diatomaceous earth and 30-50 parts by weight of activated carbon are added, and the mixture is stirred at 80-95°C for 15-40 minutes, and filter pressing and decolorization is started;

[0027] The filtrate is transferred to the acid precipitation kettle, and the filter residue is collected and transported to the hazardous waste station; at 80-95°C, 30wt% hydrochloric acid is used to reduce the pH to 1-2, and after cooling to 15-20°C, the temperature is kept for 0.5-2h; suction filtration is started, and the filter cake is washed with tap water until the pH reaches 6-7;

[0028] (5) Drying

[0029] The filter cake is dried at 100-110° C., crushed and packaged to obtain the OB acid for fluorescent whitening agent.

[0030] Furthermore, a catalyst may be added before passing chlorine in step (1). The amount of the catalyst added is 0.5-3wt% of adipic acid. The catalyst is any one of aluminum trichloride and phosphorus trichloride.

[0031] Preferably, the catalyst is a molecular sieve-supported AlCl3 catalyst.

[0032] The preparation method of the molecular sieve immobilized AlCl3 catalyst is as follows:

[0033] Place the ZSM-5 molecular sieve in a muffle furnace and roast at 500-600°C for 1-3h to activate and remove water; mix 0.5-2kg of the activated ZSM-5 molecular sieve, 3-6L of anhydrous ethanol and 0.1-0.8kg of anhydrous aluminum chloride evenly, reflux at 80-90°C for 2-5h, and naturally cool to room temperature; add 3-6L of water, stir, and filter; wash the filter cake twice with acetone, and then wash with water until there is no chloride ion; filter the filter cake and dry it to obtain the molecular sieve-supported AlCl3 catalyst.

[0034] Further preferably, the preparation method of the molecular sieve immobilized AlCl3 catalyst is:

[0035] The ZSM-5 molecular sieve is placed in a muffle furnace and roasted at 500-600°C for 1-3 hours to activate and remove water; 1-3 kg of the activated ZSM-5 molecular sieve, 0.1-0.3 kg of hafnium tetrachloride and 10-30 L of water are mixed and stirred at room temperature for 8-16 hours; filtered and dried; transferred to a muffle furnace, roasted at 500-600°C for 2-4 hours, cooled to room temperature, and ground to obtain a white solid powder, namely Hf / ZSM-5 molecular sieve;

[0036] Mix 0.5-2kg Hf / ZSM-5 molecular sieve, 3-6L anhydrous ethanol and 0.1-0.8kg anhydrous aluminum chloride evenly, reflux at 80-90°C for 2-5h, and cool naturally to room temperature; add 3-6L water, stir, and filter; wash the filter cake twice with acetone, and then wash with water until there is no chloride ion; filter the filter cake and dry it to obtain the molecular sieve-supported AlCl3 catalyst.

[0037] Beneficial effects of the present invention:

[0038] Compared with the steps of dehydration, chlorination, hydrogenation, hydrolysis, sulfidation and oxidation in the prior art, the process of the present invention is more environmentally friendly, less polluting and has no environmental problems. The simplification of the process steps can reduce the complexity and potential errors in the production process, and can also reduce production costs and improve efficiency. DETAILED DESCRIPTION

[0039] Example 1

[0040] A green and efficient preparation process of OB acid for fluorescent whitening agent comprises the following steps:

[0041] (1) Chloride

[0042] 600kg of adipic acid and 2400kg of o-dichlorobenzene were added to the reactor, stirred evenly, and then the temperature was raised to 135°C before chlorine was introduced, and the HCl absorption device was turned on. The reaction temperature was controlled at 135±2°C, the reaction time was 20min, and the chlorine consumption was 600kg; the material was transferred to the alkali solution neutralization kettle while hot; after natural cooling and the temperature dropped to 20°C, 30wt% sodium carbonate aqueous solution was used to pH 9, and the consumption of 30wt% sodium carbonate aqueous solution was 1200kg; 20kg of diatomaceous earth was added and stirred for 10 minutes, and the insoluble matter and mechanical impurities were removed by centrifugation, and the filtrate was sent to the stratification kettle; after standing for 2h, stratification began, the lower mother liquor was sent to the mother liquor tank to be applied to monochlorine, and the upper neutralization liquid was transferred to the vulcanization kettle for vulcanization;

[0043] (2) Vulcanization

[0044] Add solid sodium sulfide into the sulfiding kettle in batches at 30°C until the pH stabilizes at 8, with a solid sodium sulfide consumption of 330kg; raise the temperature to 60°C, continue to keep the temperature for 2h (during which the hydrogen sulfide tail gas absorption device is kept in normal operation), and transfer the sulfiding liquid to the dichlorination kettle;

[0045] (3) Dichloride

[0046] At 25°C, the sulfide liquid was adjusted to pH 1 with 30wt% hydrochloric acid, with a hydrochloric acid consumption of 260kg; after cooling to 0°C, the external circulation cooling device was turned on and the temperature was further cooled to -5°C; at -5°C, chlorine was passed for 15min, with a chlorine consumption of 500kg; then the temperature was raised to 96°C and kept warm for 2h; then the temperature was lowered to 25°C and kept warm for 1h, and the crude product was discharged and filtered (during which the hydrogen chloride tail gas absorption device was kept in normal operation); 390kg of crude product;

[0047] (4) Refining

[0048] 390 kg of crude product and 500 kg of 30 wt% sodium carbonate aqueous solution were put into the decolorization kettle, and the temperature was raised to 80°C to ensure that the crude product was completely dissolved; then 20 kg of diatomaceous earth and 40 kg of activated carbon were added, and the mixture was stirred at 90°C for 30 minutes, and filter pressing and decolorization was started;

[0049] The filtrate was transferred to the acid precipitation kettle, and the filter residue was collected and transported to the hazardous waste station; at 90°C, 30wt% hydrochloric acid was used to pH 1, and the hydrochloric acid consumption was 350kg; after cooling to 20°C, it was kept warm for 1h; suction filtration was started, and the filter cake was washed with tap water until the pH reached 7, and the tap water consumption was 200kg;

[0050] (5) Drying

[0051] The filter cake was dried at 100°C, crushed and packaged to obtain the OB acid for fluorescent whitening agent; the final product OB acid was 230 kg. The yield was calculated to be 32.54%.

[0052] Compared with the prior art which uses oxalic acid and thionyl chloride as raw materials and adopts pyridine as catalyst, this embodiment 1 avoids the use of pyridine, thereby minimizing the pollution problem.

[0053] Example 2

[0054] A green and efficient preparation process of OB acid for fluorescent whitening agent comprises the following steps:

[0055] (1) Chloride

[0056] 600kg of adipic acid, 2400kg of o-dichlorobenzene and 9kg of aluminum chloride were added to the reactor, stirred evenly, heated to 135°C, chlorine was introduced, and the HCl absorption device was turned on. The reaction temperature was controlled at 135±2°C, the reaction time was 20min, and the chlorine consumption was 600kg; the material was transferred to the alkali neutralization kettle while hot; naturally cooled until the temperature dropped to 20°C, 30wt% sodium carbonate aqueous solution was used to pH 9, and the consumption of 30wt% sodium carbonate aqueous solution was 1200kg; 20kg of diatomaceous earth was added and stirred for 10 minutes, insoluble matter and mechanical impurities were removed by centrifugation, and the filtrate was sent to the stratification kettle; after standing for 2h, stratification began, the lower mother liquor was sent to the mother liquor tank to be applied to monochlorine, and the upper neutralization liquid was transferred to the vulcanization kettle for vulcanization;

[0057] Aluminum trichloride as a catalyst can effectively improve the reaction efficiency, inhibit the generation of by-products, and increase the yield of the final product;

[0058] (2) Vulcanization

[0059] Add solid sodium sulfide into the sulfiding kettle in batches at 30°C until the pH stabilizes at 8, with a solid sodium sulfide consumption of 330kg; raise the temperature to 60°C, continue to keep the temperature for 2h (during which the hydrogen sulfide tail gas absorption device is kept in normal operation), and transfer the sulfiding liquid to the dichlorination kettle;

[0060] (3) Dichloride

[0061] At 25°C, the sulfide liquid was adjusted to pH 1 with 30wt% hydrochloric acid, with a hydrochloric acid consumption of 260kg; after cooling to 0°C, the external circulation cooling device was turned on and the temperature was further cooled to -5°C; at -5°C, chlorine was passed for 15min, with a chlorine consumption of 500kg; then the temperature was raised to 96°C and kept warm for 2h; then the temperature was lowered to 25°C and kept warm for 1h, and the crude product was discharged and filtered (during which the hydrogen chloride tail gas absorption device was kept in normal operation); 420kg of crude product;

[0062] (4) Refining

[0063] 420 kg of crude product and 500 kg of 30 wt% sodium carbonate aqueous solution were put into the decolorization kettle, and the temperature was raised to 80°C to ensure that the crude product was completely dissolved; then 20 kg of diatomaceous earth and 40 kg of activated carbon were added, and the mixture was stirred at 90°C for 30 minutes, and filter pressing and decolorization was started;

[0064] The filtrate was transferred to the acid precipitation kettle, and the filter residue was collected and transported to the hazardous waste station; at 90°C, 30wt% hydrochloric acid was used to reach a pH of 1, with a hydrochloric acid consumption of 350kg; after cooling to 20°C, the temperature was kept for 1h; suction filtration was started, and the filter cake was washed with tap water until the pH reached 7, with a tap water consumption of 230kg;

[0065] (5) Drying

[0066] The filter cake was dried at 100°C, crushed and packaged to obtain the OB acid for fluorescent whitening agent; the final product OB acid was 310 kg. The yield was calculated to be 43.86%.

[0067] Example 3

[0068] A green and efficient preparation process of OB acid for fluorescent whitening agent comprises the following steps:

[0069] (1) Chloride

[0070] 600kg of adipic acid, 2400kg of o-dichlorobenzene and 9kg of molecular sieve-supported AlCl3 catalyst were added to the reactor, stirred evenly, heated to 135°C and then chlorine was introduced, and the HCl absorption device was turned on. The reaction temperature was controlled at 135±2°C, the reaction time was 20min, and the chlorine consumption was 600kg; the material was transferred to the alkali-soluble neutralization kettle while hot; after natural cooling and the temperature dropped to 20°C, 30wt% sodium carbonate aqueous solution was used to pH 9, and the consumption of 30wt% sodium carbonate aqueous solution was 1200kg; 20kg of diatomaceous earth was added and stirred for 10 minutes, and the insoluble matter and mechanical impurities were removed by centrifugation, and the filtrate was sent to the stratification kettle; after standing for 2h, stratification began, the lower mother liquor was sent to the mother liquor tank to be applied to monochlorine, and the upper neutralization liquid was transferred to the vulcanization kettle for vulcanization;

[0071] (2) Vulcanization

[0072] Add solid sodium sulfide into the sulfiding kettle in batches at 30°C until the pH stabilizes at 8, with a solid sodium sulfide consumption of 330kg; raise the temperature to 60°C, continue to keep the temperature for 2h (during which the hydrogen sulfide tail gas absorption device is kept in normal operation), and transfer the sulfiding liquid to the dichlorination kettle;

[0073] (3) Dichloride

[0074] At 25°C, the sulfide liquid was adjusted to pH 1 with 30wt% hydrochloric acid, with a hydrochloric acid consumption of 260kg; after cooling to 0°C, the external circulation cooling device was turned on and the temperature was further cooled to -5°C; at -5°C, chlorine was passed for 15min, with a chlorine consumption of 500kg; then the temperature was raised to 96°C and kept warm for 2h; then the temperature was lowered to 25°C and kept warm for 1h, and the crude product was discharged and filtered (during which the hydrogen chloride tail gas absorption device was kept in normal operation); 475kg of crude product;

[0075] (4) Refining

[0076] 475 kg of crude product and 500 kg of 30 wt% sodium carbonate aqueous solution were put into the decolorization kettle, and the temperature was raised to 80°C to ensure that the crude product was completely dissolved; then 20 kg of diatomaceous earth and 40 kg of activated carbon were added, and the mixture was stirred at 90°C for 30 minutes, and filter pressing and decolorization was started;

[0077] The filtrate was transferred to the acid precipitation kettle, and the filter residue was collected and transported to the hazardous waste station; at 90°C, 30wt% hydrochloric acid was used to reach a pH of 1, and the consumption of hydrochloric acid was 350kg; after cooling to 20°C, it was kept warm for 1h; suction filtration was started, and the filter cake was washed with tap water until the pH reached 7, and the consumption of tap water was 245kg;

[0078] (5) Drying

[0079] The filter cake was dried at 100°C, crushed and packaged to obtain the OB acid for fluorescent whitening agent; the final product OB acid was 385 kg. The yield was calculated to be 54.47%.

[0080] The preparation method of the molecular sieve immobilized AlCl3 catalyst is as follows: placing a ZSM-5 molecular sieve in a muffle furnace and roasting it at 550°C for 2 hours to activate and remove water; evenly mixing 1 kg of the activated ZSM-5 molecular sieve, 5 L of anhydrous ethanol and 0.5 kg of anhydrous aluminum chloride, refluxed at 80°C for 4 hours, and naturally cooled to room temperature; adding 5 L of distilled water, stirring, and filtering; washing the filter cake twice with acetone, and then washing with distilled water until there is no chloride ion; and vacuum drying the filter cake at 80°C for 12 hours to obtain the molecular sieve immobilized AlCl3 catalyst.

[0081] The introduction of ZSM-5 molecular sieve can help AlCl3 disperse more evenly in the pores of the molecular sieve; it can increase the number of active sites and improve the catalytic efficiency. In addition, the AlCl3 catalyst immobilized on ZSM-5 molecular sieve has higher thermal stability and reduces the sublimation of AlCl3. Unlike ordinary molecular sieves, ZSM-5 molecular sieve has more acidic sites and can bind more AlCl3, improving the catalytic efficiency.

[0082] ZSM-5 molecular sieve, SiO2 / Al2O3: 30, source: Shandong Qilu Huaxin Hi-Tech Co., Ltd.

[0083] Example 4

[0084] A green and efficient preparation process of OB acid for fluorescent whitening agent comprises the following steps:

[0085] (1) Chloride

[0086] 600kg of adipic acid, 2400kg of o-dichlorobenzene and 9kg of molecular sieve-supported AlCl3 catalyst were added to the reactor, stirred evenly, heated to 135°C and then chlorine was introduced, and the HCl absorption device was turned on. The reaction temperature was controlled at 135±2°C, the reaction time was 20min, and the chlorine consumption was 600kg; the material was transferred to the alkali-soluble neutralization kettle while hot; after natural cooling and the temperature dropped to 20°C, 30wt% sodium carbonate aqueous solution was used to pH 9, and the consumption of 30wt% sodium carbonate aqueous solution was 1200kg; 20kg of diatomaceous earth was added and stirred for 10 minutes, and the insoluble matter and mechanical impurities were removed by centrifugation, and the filtrate was sent to the stratification kettle; after standing for 2h, stratification began, the lower mother liquor was sent to the mother liquor tank to be applied to monochlorine, and the upper neutralization liquid was transferred to the vulcanization kettle for vulcanization;

[0087] (2) Vulcanization

[0088] Add solid sodium sulfide into the sulfiding kettle in batches at 30°C until the pH stabilizes at 8, with a solid sodium sulfide consumption of 330kg; raise the temperature to 60°C, continue to keep the temperature for 2h (during which the hydrogen sulfide tail gas absorption device is kept in normal operation), and transfer the sulfiding liquid to the dichlorination kettle;

[0089] (3) Dichloride

[0090] At 25°C, the sulfide liquid was adjusted to pH 1 with 30wt% hydrochloric acid, with a hydrochloric acid consumption of 260kg; after cooling to 0°C, the external circulation cooling device was turned on and the temperature was further cooled to -5°C; at -5°C, chlorine was passed for 15min, with a chlorine consumption of 500kg; then the temperature was raised to 96°C and kept warm for 2h; then the temperature was lowered to 25°C and kept warm for 1h, and the crude product was discharged and filtered (during which the hydrogen chloride tail gas absorption device was kept in normal operation); 495kg of crude product;

[0091] (4) Refining

[0092] 495 kg of crude product and 500 kg of 30 wt% sodium carbonate aqueous solution were put into the decolorization kettle, and the temperature was raised to 80°C to ensure that the crude product was completely dissolved; then 20 kg of diatomaceous earth and 40 kg of activated carbon were added, and the mixture was stirred at 90°C for 30 minutes, and filter pressing and decolorization was started;

[0093] The filtrate was transferred to the acid precipitation kettle, and the filter residue was collected and transported to the hazardous waste station; at 90°C, 30wt% hydrochloric acid was used to reach a pH of 1, with a hydrochloric acid consumption of 350kg; after cooling to 20°C, the temperature was kept for 1h; suction filtration was started, and the filter cake was washed with tap water until the pH reached 7, with a tap water consumption of 260kg;

[0094] (5) Drying

[0095] The filter cake was dried at 100°C, crushed and packaged to obtain the OB acid for fluorescent whitening agent; the final product OB acid was 425 kg. The yield was calculated to be 60.13%.

[0096] The preparation method of the molecular sieve immobilized AlCl3 catalyst is as follows:

[0097] The ZSM-5 molecular sieve was placed in a muffle furnace and calcined at 550°C for 2h to activate and remove water; 2kg of the activated ZSM-5 molecular sieve, 0.18kg of hafnium tetrachloride and 20L of deionized water were mixed and stirred at room temperature for 12h; after filtering, the mixture was dried at 80°C for 2h; the mixture was transferred to a muffle furnace and calcined at 550°C for 3h, cooled to room temperature, and ground to obtain a white solid powder, namely Hf / ZSM-5 molecular sieve;

[0098] Mix 1kg Hf / ZSM-5 molecular sieve, 5L anhydrous ethanol and 0.5kg anhydrous aluminum chloride evenly, reflux at 80°C for 4h, and cool naturally to room temperature; add 5L distilled water, stir, and filter; wash the filter cake twice with acetone, and then wash with distilled water until there is no chloride ion; vacuum dry the filter cake at 80°C for 12h to obtain the molecular sieve-immobilized AlCl3 catalyst.

[0099] Practice has shown that the introduction of hafnium can improve catalytic efficiency. The possible reason is that the introduction of hafnium can enhance the acidity and catalytic activity of the molecular sieve, thereby improving the catalytic efficiency. The introduction of hafnium can help AlCl3 further reduce the activation energy, accelerate the reaction, and improve the catalytic effect.

[0100] ZSM-5 molecular sieve, SiO2 / Al2O3: 30, source: Shandong Qilu Huaxin Hi-Tech Co., Ltd.

[0101] Comparative Example 1

[0102] A green and efficient preparation process of OB acid for fluorescent whitening agent comprises the following steps:

[0103] (1) Chloride

[0104] 600kg of adipic acid, 2400kg of o-dichlorobenzene and 9kg of molecular sieve-supported AlCl3 catalyst were added to the reactor, stirred evenly, heated to 135°C and then chlorine was introduced, and the HCl absorption device was turned on. The reaction temperature was controlled at 135±2°C, the reaction time was 20min, and the chlorine consumption was 600kg; the material was transferred to the alkali-soluble neutralization kettle while hot; after natural cooling and the temperature dropped to 20°C, 30wt% sodium carbonate aqueous solution was used to pH 9, and the consumption of 30wt% sodium carbonate aqueous solution was 1200kg; 20kg of diatomaceous earth was added and stirred for 10 minutes, and the insoluble matter and mechanical impurities were removed by centrifugation, and the filtrate was sent to the stratification kettle; after standing for 2h, stratification began, the lower mother liquor was sent to the mother liquor tank to be applied to monochlorine, and the upper neutralization liquid was transferred to the vulcanization kettle for vulcanization;

[0105] (2) Vulcanization

[0106] Add solid sodium sulfide into the sulfiding kettle in batches at 30°C until the pH stabilizes at 8, with a solid sodium sulfide consumption of 330kg; raise the temperature to 60°C, continue to keep the temperature for 2h (during which the hydrogen sulfide tail gas absorption device is kept in normal operation), and transfer the sulfiding liquid to the dichlorination kettle;

[0107] (3) Dichloride

[0108] At 25°C, the sulfide liquid was adjusted to pH 1 with 30wt% hydrochloric acid, with a hydrochloric acid consumption of 260kg; after cooling to 0°C, the external circulation cooling device was turned on and the temperature was further cooled to -5°C; at -5°C, chlorine was passed for 15min, with a chlorine consumption of 500kg; then the temperature was raised to 96°C and kept warm for 2h; then the temperature was lowered to 25°C and kept warm for 1h, and the crude product was discharged and filtered (during which the hydrogen chloride tail gas absorption device was kept in normal operation); 445kg of crude product;

[0109] (4) Refining

[0110] 445 kg of crude product and 500 kg of 30 wt% sodium carbonate aqueous solution were put into the decolorization kettle, and the temperature was raised to 80°C to ensure that the crude product was completely dissolved; then 20 kg of diatomaceous earth and 40 kg of activated carbon were added, and the mixture was stirred at 90°C for 30 minutes, and filter pressing and decolorization was started;

[0111] The filtrate was transferred to the acid precipitation kettle, and the filter residue was collected and transported to the hazardous waste station; at 90°C, 30wt% hydrochloric acid was used to reach a pH of 1, and the hydrochloric acid consumption was 350kg; after cooling to 20°C, it was kept warm for 1h; suction filtration was started, and the filter cake was washed with tap water until the pH reached 7, and the tap water consumption was 235kg;

[0112] (5) Drying

[0113] The filter cake was dried at 100°C, crushed and packaged to obtain the OB acid for fluorescent whitening agent; the final product OB acid was 340 kg. The yield was calculated to be 48.10%.

[0114] The preparation method of the molecular sieve immobilized AlCl3 catalyst is as follows: placing an SBA-15 molecular sieve in a muffle furnace and roasting it at 550°C for 2 hours to activate and remove water; evenly mixing 1 kg of the activated SBA-15 molecular sieve, 5 L of anhydrous ethanol and 0.5 kg of anhydrous aluminum chloride, refluxed at 80°C for 4 hours, and naturally cooled to room temperature; adding 5 L of water, stirring, and filtering; washing the filter cake twice with acetone, and then washing with water until there is no chloride ion; and vacuum drying the filter cake at 80°C for 12 hours to obtain the molecular sieve immobilized AlCl3 catalyst.

[0115] Obviously, the use of SBA-15 molecular sieve as a carrier of AlCl3 does not improve the yield of the final product OB acid as much as that of ZSM-15 molecular sieve. The possible reasons are: there are more Lewis acid sites in the structure of ZSM-5 molecular sieve; at the same time, it also has higher thermal stability. Furthermore, the pore shape of ZSM-5 molecular sieve may help to form a specific reaction environment, which may have a promoting effect on the reaction of the present invention.

[0116] SBA-15 molecular sieve, specific surface area 600-800m 2 / g, pore size 6-11nm, source: Nanjing Jicang Nanotechnology Co., Ltd.

[0117] The synthetic route of OB acid for fluorescent whitening agent of the present invention is as follows:

[0118]

Claims

1. A process for preparing OB acid for fluorescent whitening agent, characterized in that: The steps include: (1) Chloride 500-700 parts by weight of adipic acid, 2000-3000 parts by weight of o-dichlorobenzene, and 2.5-15 parts by weight of molecular sieve-supported AlCl3 catalyst are added to a reaction kettle, stirred evenly, heated to 135-137°C, and then chlorine gas is introduced, and the HCl absorption device is turned on, and the reaction temperature is controlled at 135-137°C; After the central control is qualified, transfer the material to the alkali solution neutralization kettle while it is hot; cool naturally until the temperature drops to 10-30°C, use 20-40wt% sodium carbonate aqueous solution to pH 8.5-9.5; add 10-30 parts by weight of diatomaceous earth and stir for 5-15 minutes, centrifuge to remove insoluble matter and mechanical impurities, and the filtrate goes to the stratification kettle; after standing for 1-3 hours, start stratification, the lower mother liquor goes to the mother liquor tank to be applied to monochlorine, and the upper neutralization liquid is transferred to the sulfidation kettle for sulfidation; (2) Vulcanization At 30-35℃, add sodium sulfide solid to the upper neutralization liquid in batches until the pH stabilizes at 8-9; raise the temperature to 55-60℃, continue to keep the temperature for 1-3h, and after the central control is qualified, transfer the sulfide liquid to the dichlorination kettle; (3) Dichloride At 0-30℃, adjust the pH of the sulfide liquid to 1-2 with hydrochloric acid; after cooling to 0℃, start the external circulation cooling device and continue to cool to -5℃; at -5~0℃, pass chlorine until the central control is qualified; then heat to 96-100℃ and keep warm for 1-3h; then cool to 20-25℃ and keep warm for 0.5-2h, discharge and filter to obtain the crude product; (4) Refining The crude product and 30wt% sodium carbonate aqueous solution are mixed evenly, and the temperature is raised to 75-80°C to ensure that the crude product is completely dissolved; then 10-30 parts by weight of diatomaceous earth and 30-50 parts by weight of activated carbon are added, and the mixture is stirred at 80-95°C for 15-40 minutes, and filter pressing and decolorization is started; The filtrate is transferred to the acid precipitation kettle, and the filter residue is collected and transported to the hazardous waste station; At 80-95°C, add 30wt% hydrochloric acid to a pH of 1-2, cool to 15-20°C, and keep warm for 0.5-2h; start filtration, and wash the filter cake with tap water until the pH reaches 6-7; (5) Drying Dry the filter cake at 100-110° C., crush it and package it to obtain the OB acid for fluorescent whitening agent; The preparation method of the molecular sieve immobilized AlCl3 catalyst is as follows: The ZSM-5 molecular sieve is placed in a muffle furnace and roasted at 500-600°C for 1-3 hours to activate and remove water; 1-3 kg of the activated ZSM-5 molecular sieve, 0.1-0.3 kg of hafnium tetrachloride and 10-30 L of water are mixed and stirred at room temperature for 8-16 hours; filtered and dried; transferred to a muffle furnace, roasted at 500-600°C for 2-4 hours, cooled to room temperature, and ground to obtain a white solid powder, namely Hf / ZSM-5 molecular sieve; Mix 0.5-2kg Hf / ZSM-5 molecular sieve, 3-6L anhydrous ethanol and 0.1-0.8kg anhydrous aluminum chloride evenly, reflux at 80-90°C for 2-5h, and cool naturally to room temperature; add 3-6L water, stir, and filter; wash the filter cake twice with acetone, and then wash with water until there is no chloride ion; filter the filter cake and dry it to obtain the molecular sieve-supported AlCl3 catalyst.

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