Method for recycling epoxidation wastewater of hydrogen peroxide method epichlorohydrin process

Abstract

The application discloses a method for recycling of epoxidation wastewater in a hydrogen peroxide method epichlorohydrin process, which comprises the following steps: sequentially subjecting the epoxidation wastewater in the hydrogen peroxide method epichlorohydrin process to condensation and sedimentation, impurity removal by filtration and oil removal by filtration, so that the colloidal polymer and solid corrosion impurities in the wastewater can be completely removed, and most of 3-chloro-1,2-propanediol and chloropropylene glycol monomethyl ether in the wastewater can be removed at the same time; and the treated wastewater can be directly recycled to a crude epichlorohydrin extraction and separation process for recycling, and the recycling process is simple in operation and stable in continuous control.

Description

TECHNICAL FIELD

[0001] The application relates to a method for recycling of epoxidation wastewater in a hydrogen peroxide method epichlorohydrin process, and belongs to the field of petrochemical industry. BACKGROUND

[0002] Epichlorohydrin is an important basic organic chemical raw material and intermediate, and is widely used in the synthesis of epoxy resin, chlorohydrin rubber, medicines, pesticides, surfactants, plasticizers and various industrial products. At present, the most studied process is the process for preparing epichlorohydrin by directly epoxidizing 3-chloropropylene with hydrogen peroxide, with titanium-silicon molecular sieve as a catalyst. A large amount of methanol is generally used as a solvent to dissolve excessive 3-chloropropylene in methanol and react with hydrogen peroxide, so as to ensure high hydrogen peroxide conversion rate and epichlorohydrin selectivity, and realize efficient and clean synthesis of epichlorohydrin.

[0003] Chinese patent CN101293882A discloses a method for economically and efficiently separating epichlorohydrin from the epoxidation reaction product of 3-chloropropylene and hydrogen peroxide. The method mixes a solution containing epichlorohydrin, methanol, 3-chloropropylene and water with an extractant, and then separates to obtain a liquid phase rich in epichlorohydrin and a liquid phase rich in methanol. The liquid phase rich in epichlorohydrin is separated by ordinary rectification to separate 3-chloropropylene and epichlorohydrin, and the liquid phase rich in methanol is recovered by rectification to separate 3-chloropropylene and methanol. However, a certain amount of epoxidation wastewater is also produced at the same time.

[0004] At present, it is found in the pilot production process that the separation of methanol and 3-chloropropylene in the rectification tower at high temperature produces a part of gummy polymer of chloropropylene and epichlorohydrin. The polymer is mixed with impurities in the rectification tower to form corrosive acid mud which accumulates in the wastewater. The polymer can also be formed in the epoxidation reaction process, a part of which is adsorbed in the pore channel of the titanium-silicon molecular sieve catalyst to cause catalyst plugging and deactivation, and most of which enters the crude product, is recovered by separation and rectification, and finally enters the wastewater to accumulate, causing the increase of wastewater acidity and viscosity and even the generation of viscous adhesion. At the same time, the wastewater also contains a certain amount of by-product chloropropylene glycol monomethyl ether and 3-chloro-1,2-propanediol. The accumulation of these organic matters seriously affects the stability of the extraction in the wastewater recycling process.

[0005] As disclosed in Chinese patents CN106630007A and CN106630083A, the above-mentioned epoxidation wastewater also contains 0.24-0.92 wt.% of 3-chloro-1,2-propanediol and 0.78-1.61 wt.% of chloropropyl glycol monomethyl ether, and a method for converting the toxic and harmful 3-chloro-1,2-propanediol and chloropropyl glycol monomethyl ether in the epoxidation wastewater into non-toxic and harmless glycerol and glycerol monomethyl ether is respectively disclosed. The method can reduce the content of organic matter in the wastewater to a certain extent, but the newly introduced strong alkali and the generated glycerol and glycerol monomethyl ether are not removed, and cannot be reused.

[0006] Further, as disclosed in Chinese patent CN112645402A, a method for continuously treating and reducing the COD value of epoxidation wastewater by fixed bed adsorption of organic matter can convert high-COD epoxidation wastewater with a COD of 8000-30000 mg / L into epoxidation wastewater substantially free of 3-chloro-1,2-propanediol and chloropropyl glycol monomethyl ether and with a COD of less than 600 mg / L, thereby achieving continuous treatment of epoxidation wastewater while substantially reducing the COD of the epoxidation wastewater. However, the method is only for treating 3-chloro-1,2-propanediol and chloropropyl glycol monomethyl ether in wastewater, and the fixed bed adsorbent is easily blocked by the gummy polymer accumulated in the wastewater, and the adsorbate needs to be desorbed at high temperature, which has a long regeneration time and complicated operation.

[0007] In summary, the existing technologies have the problems of easy adhesion and blockage of condensation alcohol ethers in epoxidation wastewater, which is not conducive to direct reuse, complex wastewater treatment system, and high energy consumption. SUMMARY

[0008] In view of the defects in the prior art, the purpose of the present application is to provide a method for reusing epoxidation wastewater produced by the hydrogen peroxide method of epichlorohydrin process, which can efficiently and quickly remove the gummy polymer and other corrosive impurities in the epoxidation wastewater produced by the hydrogen peroxide method of epichlorohydrin process, partially remove 3-chloro-1,2-propanediol and chloropropyl glycol monomethyl ether in the epoxidation wastewater produced by the hydrogen peroxide method of epichlorohydrin process, reduce the concentration of organic matter in the epoxidation wastewater, and achieve sustainable reuse of the epoxidation wastewater, which is beneficial to resource saving and water treatment cost, and is suitable for industrial production.

[0009] In order to achieve the above technical purpose, the present application provides a method for reusing epoxidation wastewater produced by the hydrogen peroxide method of epichlorohydrin process, which is to condense and settle the epoxidation wastewater produced by the hydrogen peroxide method of epichlorohydrin process, and then filter the upper aqueous phase with a filter having a filter core size of 5-50 μm to remove impurities, and then use a coalescence oil removal filter having a filter core size of 5-20 μm to coalesce and remove oil, and then reuse the oil-removed aqueous phase to a crude epichlorohydrin extraction and separation process.

[0010] The treatment process of the epoxidation wastewater produced by the hydrogen peroxide method of epichlorohydrin process mainly includes condensation settling, impurity removal by filtration and oil removal by filtration coalescence. The condensation settling process can effectively remove most of the colloidal polymer and corrosion impurities contained in the epoxidation wastewater by reducing the temperature to make the solubility of the colloidal polymer and corrosion impurities lower. The physical properties and water phase containing 3-chloro-1, 2-propanediol and chloropropanediol monomethyl ether of the colloidal polymer and corrosion impurities in the epoxidation wastewater are different, such as solubility, density, etc. Most of the colloidal polymer and corrosion impurities are settled under the action of condensation to avoid the blockage of the subsequent filter. The water phase is further filtered by a filter with a filter core level of 5-50 μm to remove trace amounts of colloidal polymer and corrosion impurities. By selecting a filter core with a suitable pore size, the colloidal polymer and corrosion impurities can be efficiently intercepted. When passing through the oil removal filter by coalescence, 3-chloro-1, 2-propanediol and chloropropanediol monomethyl ether penetrate through the filter cylinder wall and gather in the outer space of the filter cartridge. In the flow process, they collide and coalesce with other organic matters in the epoxidation wastewater to form large oil droplets, which fall off from the surface of the filter core under the action of gravity and finally coalesce rapidly in the outer space of the filter cartridge. The organic matter-containing epoxidation wastewater is discharged through the outer cylinder discharge port, and the remaining epoxidation wastewater containing less organic matter meets the standard for normal use in the subsequent crude epichlorohydrin extraction and separation process.

[0011] As a preferred scheme, the content of colloidal polymer and corrosion impurities in the epoxidation wastewater produced by the hydrogen peroxide method of epichlorohydrin process is 0.1-1.5 wt.%, the content of chloropropanediol monomethyl ether is 0.5-3 wt.%, and the content of 3-chloro-1, 2-propanediol is 0.1-3 wt.%. When the epoxidation wastewater is directly reused, the content of by-products and impurities will continue to accumulate.

[0012] As a preferred scheme, the temperature of the condensation settling is 5-20°C. The condensation settling process uses a water bath jacket type condensation settling tank. If the condensation temperature is too high, the colloidal polymer and corrosion impurities cannot be effectively settled, and if the condensation temperature is too low, the settling effect is not significantly improved, but the refrigeration energy consumption is increased.

[0013] As a preferred scheme, the filter core of the filter with a filter core level of 5-50 μm is a ceramic membrane, a metal membrane, a PTFE membrane or a metal multilayer sintered mesh. Further preferably, it is a metal multilayer sintered mesh, which can better filter the trace amounts of colloidal suspended impurities in the wastewater and is easy to clean.

[0014] As a preferred scheme, the filter core of the oil removal filter by coalescence is composed of at least two layers of fiber membranes wound on a metal mesh.

[0015] As a preferred scheme, the fiber membrane is at least one of metal composite fiber, glass composite fiber, polytetrafluoroethylene composite fiber, polypropylene composite fiber. Further preferably, the fiber membrane is at least one of oleophobic hydrophobic composite fiber, polytetrafluoroethylene composite fiber, polypropylene composite fiber, which can realize rapid and efficient removal of a small amount of organic matter in wastewater.

[0016] As a preferred scheme, the pressure of the coalescence oil removal filter in the oil removal process is controlled to be 0-0.3 MPa. If the pressure is too large, the hydrophobic function disappears, resulting in a large amount of water overflowing to the outside of the filter cartridge along with the oil agent, which weakens the oil-water separation effect.

[0017] As a preferred scheme, the water phase after oil removal is reused in the crude epichlorohydrin extraction separation process, and the density difference between the reused water phase and the extractant at normal temperature is 50-100 kg / m 3 . If the density difference is too small, the two phases are difficult to mix or clarify well only by gravity in the extraction process, the extraction phase separation time is prolonged, and the phase separation is unclear. If the density difference is too large, the mixing emulsification and dissolution effect of the extractant and the extracted substance are affected, and the extraction efficiency is poor. If the reuse temperature is too high, the solubility between the two phases of the extractant increases, and the stratification area decreases, which is not conducive to extraction. If the temperature is too low, the viscosity of the fluid increases, the fluidity becomes poor, and the mixing emulsification and sedimentation stratification of the extraction are affected.

[0018] As a preferred scheme, the extractant is 3-chloropropylene. 3-chloropropylene is a raw material for directly preparing epichlorohydrin by epoxidation, and as an extractant, it does not introduce new impurities.

[0019] Compared with the prior art, the technical scheme of the present application has the following beneficial technical effects:

[0020] The method of the present application can completely remove the colloidal polymer and corrosion and sediment impurities through condensation sedimentation and a filter with a filter core grade of 5-50 μm, prevent the polymer from accumulating in the rectification and extraction processes and entering the reaction to block the pore channels of the titanium-silicon molecular sieve catalyst, improve the separation effect of rectification and the service life of the catalyst, and reduce the content of chloropropanediol monomethyl ether and 3-chloro-1,2-propanediol through a coalescence oil removal filter with a filter core grade of 5-20 μm. The water bath jacket type wastewater sedimentation tank, the impurity removal filter and the coalescence oil removal filter are simply connected in series, and the continuous reuse of epoxidation wastewater is realized.

[0021] The method of the present application is simple in operation, remarkable in effect, and easy to realize industrialization. DETAILED DESCRIPTION

[0022] The technical scheme of the present application is further described below in combination with specific embodiments.

[0023] In the following examples and comparative examples, the composition contents of the water phase product and the organic phase product extracted and separated were determined by gas chromatography (Agilent 6890N gas chromatograph, capillary column, internal standard method for quantitative determination); the contents of the gummy polymer and the corrosion impurities were determined by gravimetric method.

[0024] Example 1

[0025] The epoxidation wastewater produced in the process of preparing epichlorohydrin by directly epoxidizing 3-chloropropylene with hydrogen peroxide using titanium silicalite as catalyst was detected and analyzed to contain 0.720 wt.% of gummy polymer and corrosion impurities, 2.08 wt.% of chloropropanediol monomethyl ether and 1.35 wt.% of 3-chloro-1,2-propanediol. The process wastewater was condensed at a flow rate of 8 kg / h through a settling tank, the condensation temperature was set to 10°C, and after filtration through a 50 μm impurity removal filter (made of ceramic membrane, metal membrane, PTFE and metal multilayer sintered mesh respectively), it was detected that the wastewater contained gummy polymer and solid corrosion impurities, chloropropanediol monomethyl ether and 3-chloro-1,2-propanediol, the contents of which are shown in the following table.

[0026] Table 1. Data of wastewater filtration using different filter materials for impurity removal filter

[0027]

[0028] As can be seen from the results of the above examples, the metal multilayer sintered mesh filter has the best effect on filtering gummy polymer and corrosion impurities in wastewater, and the inert filter membrane without special treatment has no filtering effect on chloropropanediol monomethyl ether and 3-chloro-1,2-propanediol.

[0029] Example 2

[0030] The epoxidation wastewater produced in the process of preparing epichlorohydrin by directly epoxidizing 3-chloropropylene with hydrogen peroxide using titanium silicalite as catalyst was detected and analyzed to contain 0.64 wt.% of gummy polymer and corrosion impurities, 1.81 wt.% of chloropropanediol monomethyl ether and 1.25 wt.% of 3-chloro-1,2-propanediol. The process wastewater was condensed at a flow rate of 8 kg / h through a settling tank, the condensation temperature was set to 10°C, and after filtration through a 50 μm metal multilayer sintered mesh filter, it was further filtered through a 20 μm coalescence oil removal filter (made of metal fiber, glass fiber, polytetrafluoroethylene fiber, polypropylene fiber and inert metal mesh combined with oleophilic hydrophobic composite fiber respectively) at a pressure of 0.3 MPa, and it was detected that the wastewater contained gummy polymer and solid corrosion impurities, chloropropanediol monomethyl ether and 3-chloro-1,2-propanediol, the contents of which are shown in the following table.

[0031] Table 2. Data of wastewater filtration using different filter materials for coalescence oil removal filter

[0032]

[0033]

[0034] From the results of the above examples, it can be seen that different composite materials, including inorganic and organic materials, all have coalescing effect on chloropropanediol monomethyl ether and 3-chloro-1,2-propanediol, and the polytetrafluoroethylene composite fiber and polypropylene composite fiber with lipophilicity and hydrophobicity have better coalescing effect on chloropropanediol monomethyl ether and 3-chloro-1,2-propanediol.

[0035] Example 3

[0036] The epoxy wastewater generated in the process of preparing epichlorohydrin by directly epoxidizing 3-chloropropylene with hydrogen peroxide and titanium silicalite molecular sieve as catalyst was detected and analyzed. The wastewater contains 0.16 wt.% of gummy polymer and corrosion and precipitation impurities, 0.65 wt.% of chloropropanediol monomethyl ether and 0.16 wt.% of 3-chloro-1,2-propanediol. The wastewater is condensed at a flow rate of 8 kg / h through a settling tank with a condensation temperature of 10°C, and after being filtered through a 50 μm metal multi-layer sintered mesh filter, no gummy polymer and corrosion and precipitation impurities are detected in the wastewater, and 0.65 wt.% of chloropropanediol monomethyl ether and 0.16 wt.% of 3-chloro-1,2-propanediol are still detected after the impurity removal filter. Then, the wastewater is filtered through a coalescing oil removal filter with a polytetrafluoroethylene composite fiber filter core material of 15 μm filter core grade, and the pressure is controlled to be below 0.3 MPa. The chloropropanediol monomethyl ether and 3-chloro-1,2-propanediol at the outlet of the coalescing oil removal filter are reduced to 0.40 wt.% and 0.14 wt.%, respectively. The treated wastewater is directly reused in the crude epichlorohydrin extraction unit. The crude epichlorohydrin stream is fed at a flow rate of 12 kg / h, the 3-chloropropylene stream is fed at a flow rate of 8 kg / h, the epoxidation wastewater stream is fed at a flow rate of 6.5 kg / h, and the extraction temperature is 20°C under normal pressure. The data of continuous reuse for a period of time are shown in the following table.

[0037] Extraction rate of epichlorohydrin (%) = (1 - lost epichlorohydrin) / epichlorohydrin contained in the feed to be separated;

[0038] Extraction rate of methanol (%) = (1 - lost methanol) / methanol contained in the feed to be separated;

[0039] Table 3. Data record of continuous reuse of treated epoxidation wastewater

[0040]

[0041]

[0042] From the above example results, it can be seen that the method of the present application can completely remove the gummy polymer and corrosion and precipitation impurities in the wastewater, and partially remove the chloropropanediol monomethyl ether and 3-chloro-1,2-propanediol, and can completely achieve continuous treatment of the epoxidation wastewater, and the extraction separation process is automatically controlled stably, the phase separation interface is clear, and the content of organic matter in the epoxidation wastewater can be greatly reduced.

[0043] Comparative Example 1

[0044] Epoxy chloropropane wastewater produced in the process of directly epoxidizing 3-chloropropylene with hydrogen peroxide and 3-chloropropylene using titanium silicalite molecular sieve as catalyst was detected and analyzed, and it was found that the wastewater contained 0.150wt.% of gummy polymer and corrosion and precipitation impurities, 0.67wt.% of chloropropanediol monomethyl ether, and 0.17wt.% of 3-chloro-1,2-propanediol. The process wastewater was not treated and was directly reused to the crude epoxy chloropropane extraction unit, the crude epoxy chloropropane stream was fed at a flow rate of 12kg / h, the 3-chloropropylene flow rate was 8kg / h, the epoxidation wastewater flow rate was 6.5kg / h, and the reuse temperature was 20℃ under normal pressure. The data of continuous reuse for a period of time are shown in the following table.

[0045] Extraction rate of epoxy chloropropane (%) = (1 - lost epoxy chloropropane) / epoxy chloropropane contained in the feed to be separated

[0046] Extraction rate of methanol (%) = (1 - lost methanol) / methanol contained in the feed to be separated

[0047] Table 4. Data record of continuous reuse of wastewater to be treated

[0048]

[0049]

[0050] From the above example results, it can be seen that the untreated epoxidation wastewater directly reused has the phenomenon of continuously accumulating and increasing gummy polymer and corrosion and precipitation impurities, chloropropanediol monomethyl ether content, and 3-chloro-1,2-propanediol content, thereby affecting the effect of separating crude epoxy chloropropane after the wastewater is reused as an extractant, the extraction rates of epoxy chloropropane and methanol are both reduced, the extraction process control is unstable, and there is flocculent accumulation in the interface phase separation. The method of the present application can achieve continuous treatment of the epoxidation wastewater, can quickly and greatly reduce the content of organic matter in the epoxidation wastewater, and is simple to operate.

Claims

1. A method for reusing epoxidation wastewater from a hydrogen peroxide-based epichlorohydrin process, characterized in that: The epoxidation wastewater from the hydrogen peroxide method epichlorohydrin process is condensed and settled. The upper aqueous phase is first filtered to remove impurities using a filter with a filter element size of 5~50μm, and then coalesced and removed from oil using a coalescing oil removal filter with a filter element size of 5~20μm. The oil-removed aqueous phase is then reused in the crude epichlorohydrin extraction and separation process. The epoxidation wastewater from the hydrogen peroxide-based epichlorohydrin process contains 0.1-1.5 wt.% colloidal polymers and corrosive impurities, 0.5-3 wt.% chloropropanediol monomethyl ether, and 0.1-3 wt.% 3-chloro-1,2-propanediol. The temperature of the condensation and sedimentation is 5~20℃.

2. The method for reusing epoxidation wastewater from the hydrogen peroxide-based epichlorohydrin process according to claim 1, characterized in that: The filters with a filter element grade of 5~50μm use ceramic membranes, metal membranes, or PTFE membranes.

3. The method for reusing epoxidation wastewater from the hydrogen peroxide-based epichlorohydrin process according to claim 1, characterized in that: The filter with a filter element size of 5~50μm uses a multi-layer sintered metal mesh as the filter element.

4. The method for reusing epoxidation wastewater from the hydrogen peroxide-based epichlorohydrin process according to claim 1, characterized in that: The filter element of the coalescing oil removal filter is composed of at least two layers of fiber membrane wound on a metal wire mesh.

5. A method for reusing epoxidation wastewater from a hydrogen peroxide-based epichlorohydrin process according to claim 4, characterized in that: The fiber membrane is composed of at least one of metal composite fiber, glass composite fiber, polytetrafluoroethylene composite fiber, and polypropylene composite fiber.

6. The method for reusing epoxidation wastewater from the hydrogen peroxide-based epichlorohydrin process according to claim 1, characterized in that: During the oil removal process, the pressure of the coalescing oil removal filter is controlled at 0~0.3MPa.

7. A method for reusing epoxidation wastewater from a hydrogen peroxide-based epichlorohydrin process according to any one of claims 1 to 6, characterized in that: The de-oiled aqueous phase is reused in the crude epichlorohydrin extraction and separation process. The density difference between the reused aqueous phase and the extractant at room temperature is 50~100 kg / m³. 3 The reuse temperature is 10~20℃.

8. A method for reusing epoxidation wastewater from a hydrogen peroxide-based epichlorohydrin process according to claim 7, characterized in that: The extractant is 3-chloropropene.

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