Process for the preparation of electronic grade n-butyl acetate

Abstract

The application discloses a preparation method of electronic-grade n-butyl acetate and belongs to the field of electronic chemical purification. The method comprises the following steps: after industrial-grade n-butyl acetate is pretreated by activated carbon and anhydrous magnesium sulfate and filtered, the n-butyl acetate is sent into a BX packing rectification tower for segmental rectification, the front fraction is discarded, the main fraction is subjected to D001 macroporous strong acid cation exchange resin to remove Ca2+, Mg2+ and other metal ions, finally, the n-butyl acetate is subjected to terminal filtration through a 0.02-0.1 micrometer polytetrafluoroethylene filter element, and is stored under the protection of nitrogen. The ion exchange is arranged after the rectification, so that secondary refining is realized, the purity of the product is greater than or equal to 99.999%, the total content of metal ions is lower than 10 ppm, and the product is suitable for the fields of semiconductor cleaning and photoresist dilution.

Description

Technical Field

[0001] This invention belongs to the field of electronic chemical preparation technology, specifically relating to a method for preparing electronic-grade n-butyl acetate. Background Technology

[0002] Electronic-grade n-butyl acetate is a key auxiliary material in the semiconductor industry and panel display manufacturing, mainly used as a wafer and chip cleaning agent, photoresist solvent and diluent, and chip packaging adhesive solvent. Its key characteristics—high purity (≥99.999%), suitable evaporation rate, low surface tension, and excellent chemical stability—directly affect the yield and reliability of electronic devices. Trace amounts of metal ions (such as Ca²⁺, Mg²⁺, Fe³⁺) can form conductive paths or cause corrosion on the device surface, while tiny particulate impurities may lead to short circuits or photolithography defects.

[0003] Currently, the mainstream industrial production method for n-butyl acetate is the esterification method: using acetic acid and n-butanol as raw materials and concentrated sulfuric acid as a catalyst. This method involves numerous side reactions. n-Butanol readily forms n-butyl ether and 1-butene under the action of concentrated sulfuric acid. Concentrated sulfuric acid also easily triggers polymerization reactions such as sulfonation and carbonization, resulting in a complex composition of impurities in the product. In the post-treatment process, commonly used desiccants (anhydrous magnesium sulfate, anhydrous calcium chloride) and neutralizing agents (saturated sodium carbonate) introduce inorganic salt particles such as sodium sulfate and sodium acetate, which are difficult to completely remove using conventional distillation.

[0004] Existing purification literature primarily reports on conventional distillation, employing ordinary distillation columns with serpentine condensers, which has limited removal capabilities for metal ions and nanoscale particles. While recent studies have explored single methods such as activated carbon adsorption and ion exchange resins, these are mostly laboratory-scale, lacking sufficient synergy between units, making it difficult to stably produce electronic-grade products with a total metal ion content below 10 ppm and a purity ≥99.999%. Therefore, developing an efficient, continuous, and low-cost method for preparing electronic-grade n-butyl acetate has significant industrial value. Summary of the Invention

[0005] This invention provides a method for preparing electronic-grade n-butyl acetate, which integrates pretreatment, distillation, ion exchange, terminal filtration and nitrogen-protected storage in a specific order to achieve deep removal of metal ions, organic impurities and particulate matter.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] A method for preparing electronic-grade n-butyl acetate includes the following stages: S1: Preprocessing stage ① Add industrial-grade n-butyl acetate raw material to the pretreatment tank, wherein the mass content of n-butyl acetate in the raw material is not less than 97%; ② Add impurity removal additive to the pretreatment tank. The additive consists of activated carbon and anhydrous magnesium sulfate. Start the agitator and stir at a speed of 80-150 rpm for 2-3 hours. ③ The mixed materials are filtered through a multi-layer filter membrane in the outlet pipe of the pretreatment tank. The filter membrane pore size is 0.5 to 2 micrometers to obtain the pretreatment liquid.

[0008] S2: Distillation Stage ① The pretreated liquid obtained in S1③ is transported to the distillation column of the distillation unit, and the pressure inside the distillation column is controlled to be atmospheric pressure; ② Set the temperature of the bottom heater of the distillation column to 130-140℃, the temperature of the top of the column to 100-105℃, the reflux ratio to 10:3-5, and start collecting the fraction into the fore-fraction tank after reflux time of 3-5 hours; ③ Set the temperature of the bottom heater to 130-145℃, the temperature of the top heater to 105-110℃, and the reflux ratio to 10:3-5. Collect the distillate and enter the main fraction tank to obtain the distillate liquid.

[0009] S3: Ion exchange stage The distillate obtained in S2③ is transported to the ion exchange device under positive pressure, and passes through the cation exchange resin layer at a flow rate of 0.4 to 0.8 cubic meters per hour to remove Ca²⁺ and Mg²⁺ metal ions, thus obtaining the ion exchange solution.

[0010] S4: Filtering Stage The ion exchange solution obtained in S3 is transported to the filtration device under positive pressure. It is filtered through multiple layers of filter membranes in the upper layer of the filter box and a polytetrafluoroethylene filter element in the lower layer. The filter element has a size of 0.02 to 0.1 microns and the filtration pressure is 5 to 7 kPa, resulting in the filtrate.

[0011] S5: Storage Phase After purging the storage device three times with vacuum nitrogen, the filtrate obtained in S4 is transferred to the storage device and stored under high-purity nitrogen protection to obtain electronic-grade n-butyl acetate product.

[0012] Preferably, the mass ratio of activated carbon to anhydrous magnesium sulfate added in S1② is 0.2-0.5 kg of activated carbon and 1.5-2.5 kg of anhydrous magnesium sulfate per 300 kg of n-butyl acetate raw material.

[0013] Preferably, the BX metal wire mesh packing filled in the distillation column in S2 is a structured packing with an effective specific surface area of ​​500-700 m² / m³.

[0014] Preferably, the cation exchange resin in S3 is a D001 macroporous strong acid styrene-based cation exchange resin with a working exchange capacity of not less than 1300 mmol / L and a regenerator dosage of 40-100 kg / m³.

[0015] Preferably, the final electronic-grade n-butyl acetate product has a n-butyl acetate content of not less than 99.999% and a total metal ion content of less than 10 ppm.

[0016] The present invention also provides an electronic-grade n-butyl acetate preparation apparatus for implementing the above method, which is provided in sequence with a pretreatment device, a distillation device, an ion exchange device, a filtration device and a storage device. The material conveying pipelines between the devices are all made of EP-grade electropolished stainless steel and are equipped with inert gas protection interfaces.

[0017] Compared with the prior art, the present invention has the following significant advantages: (1) Innovative process flow sequence to achieve a "secondary purification" effect of ion exchange after distillation. Existing technologies usually place ion exchange before distillation as a pretreatment to remove impurities; this invention places ion exchange after distillation. The distillation column uses BX high-efficiency packing to remove most of the entrained metal ions and low-boiling substances, and the ion exchange column then uses D001 macroporous strong acid resin to deeply purify the distillate. The two functions are complementary rather than redundant. Comparative experiments show that placing ion exchange after distillation can reduce the total amount of calcium and magnesium ions in the final product to below 1 ppm, while the residual amount in the pretreatment scheme is >5 ppm under the same conditions.

[0018] (2) The synergistic matching of BX metal wire mesh packing with the fractional distillation parameters significantly improves the separation efficiency. The effective specific surface area of ​​BX structured packing reaches 500-700 m² / m³, with a high theoretical plate number and low pressure drop. This invention matches it with two-stage temperature distillation (first fraction 130-140℃ / 100-105℃, main fraction 130-145℃ / 105-110℃) and a reflux ratio of 10:3-5, which can efficiently separate n-butyl acetate from impurities with similar boiling points such as n-butanol and butyl ether. Compared with ordinary bulk packing, BX packing can reduce the residual amount of n-butanol from 0.05% to below 0.005% in the main fraction collection stage.

[0019] (3) The terminal precision filtration uses a hydrophobic PTFE filter element to ensure particulate matter and microbial control. The 0.02-0.1 micron PTFE filter element has excellent chemical compatibility and low metal ion release characteristics, which can effectively intercept fine particles that may be shed from ion exchange resin and dust particles in the environment. After terminal filtration, the number of particles ≥0.2μm in the product can be controlled to less than 10 particles per milliliter, which meets the SEMI standard for semiconductor wet electronic chemicals.

[0020] (4) The rational ratio of activated carbon and anhydrous magnesium sulfate in the pretreatment unit and the segmented filtration extend the life of subsequent units. Activated carbon adsorbs organic pigments and colloidal impurities, while anhydrous magnesium sulfate removes visible moisture. Combined with a 0.5-2 micron primary filter, coking in the reboiler of the distillation column and packing contamination can be prevented. Experiments show that after pretreatment according to this invention, the pressure drop increase of the distillation column during 500 hours of continuous operation is reduced by 60% compared to the untreated column, and the regeneration cycle is extended by 2 times.

[0021] (5) Precise selection of ion exchange resin and control of flow rate, taking into account both exchange capacity and effluent quality. D001 macroporous strong acid resin has high exchange capacity (≥1300mmol / L) and good mechanical strength. At a flow rate of 0.4~0.8m³ / h, the single-pass removal rate of Ca²⁺ and Mg²⁺ can reach over 99.5%, and the resin is not easily contaminated by organic matter. The amount of regenerant used is only 40~100kg / m³, resulting in low operating costs.

[0022] (6) The entire process is designed for continuous operation, making it suitable for large-scale industrial production. Each unit is connected sequentially, and materials flow continuously under positive pressure or gravity, eliminating the need for intermediate storage tanks and manual transfer. The pretreatment tank can be designed with jacketed temperature control and a built-in segmented adsorption bed, supporting online feeding and self-cleaning regeneration; the distillation column can be equipped with an automatic reflux ratio controller; the ion exchange column uses a one-in-one-out parallel switching system to achieve uninterrupted production. The entire system is easily automated with a DCS system, ensuring high batch stability of products.

[0023] (7) Green and environmentally friendly with high solvent recovery rate. This invention does not introduce additional toxic solvents. The pretreatment additives are conventional activated carbon and magnesium sulfate, resulting in low solid waste. The waste liquid generated in the distillation process is mainly the fore-distillate, which can be centrally recycled and treated. The terminal filter cartridge is replaced regularly, and there are no fluorine or heavy metal pollutants. According to calculations, the overall product yield is ≥92%, and the utilization rate of organic solvents is high. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments and comparative experiments, but the implementation of the present invention is not limited thereto.

[0025] Example 1 (Complete process using the preferred embodiment of the present invention) Raw material: 300 kg of industrial grade n-butyl acetate. The n-butyl acetate content was tested to be 97.5%, moisture 280 ppm, calcium ion 12 ppm, magnesium ion 8 ppm, iron ion 5 ppm. The appearance was slightly yellow, and the particle count (≥0.5μm) was about 850 particles / mL.

[0026] S1 Pretreatment: The raw materials were added to the pretreatment tank, along with 0.35 kg of activated carbon and 2.0 kg of anhydrous magnesium sulfate. The stirrer was started at 120 rpm and stirred for 2.5 hours. Then, the mixture was filtered through a 0.8-micron multilayer filter membrane to obtain the pretreated solution. Testing showed that the moisture content was reduced to 65 ppm, the color was colorless, and the particulate matter count was reduced to 120 particles / mL.

[0027] S2 Distillation: The pretreated liquid was continuously fed into a distillation column (300mm diameter, packed with BX wire mesh corrugated packing, 4.5m high). Under controlled atmospheric pressure, the bottom temperature was initially set to 135℃, the top temperature to 102℃, and the reflux ratio to 10:4. After reflux for 4 hours, the foremilk (approximately 8kg) was collected and discarded. Then, the bottom temperature was adjusted to 140℃, the top temperature to 107℃, and the reflux ratio to 10:4, and the main fraction was collected, yielding approximately 285kg of distillate. Online gas chromatography analysis revealed that the distillate contained 99.93% n-butyl acetate, 0.02% n-butanol, 22ppm water, 1.8ppm calcium ion residue, and 1.2ppm magnesium ion residue.

[0028] S3 Ion Exchange: The distillate was passed through an exchange column packed with D001 macroporous strong acid cation exchange resin (resin bed height 1.2m, column diameter 200mm) at a flow rate of 0.6m³ / h to obtain the ion exchange solution. ICPMS analysis showed that calcium ions <0.1ppm, magnesium ions <0.1ppm, iron ions <0.05ppm, and the total content of other metal ions <0.5ppm.

[0029] S4 filtration: The ion exchange solution is delivered to the filter chamber under positive pressure, passing sequentially through an upper 0.2-micron PP pre-filter membrane and a lower 0.05-micron PTFE filter element at a filtration pressure of 6 kPa. The resulting filtrate has a particle count (≥0.2 μm) ≤5 particles / mL.

[0030] S5 storage: Replace the storage tank three times with high-purity nitrogen (vacuum degree 80kPa, nitrogen filling to normal pressure), then connect the filter liquid and maintain a slight positive pressure nitrogen protection inside the tank.

[0031] Final product testing: Butyl acetate content 99.9996%, moisture 8 ppm, total metal ion content 0.8 ppm (of which Ca≤0.1, Mg≤0.1, Fe≤0.05, Na≤0.2, K≤0.2), particulate matter (≥0.2μm) ≤5 particles / mL, color (PtCo) ≤5. Fully meets electronic grade requirements.

[0032] Example 2 (Schemes using different parameter ranges) Except for the following parameters, the rest are the same as in Example 1: The pretreatment stirring speed was 80 rpm, the stirring time was 3 hours, and the ingredients were 0.25 kg of activated carbon and 2.2 kg of anhydrous magnesium sulfate. The bottom temperature of the first section of the distillation column is 132℃, the top temperature is 101℃, the reflux ratio is 10:3, and the reflux time is 5 hours; the bottom temperature of the second section is 138℃, the top temperature is 106℃, and the reflux ratio is 10:3. Ion exchange flow rate: 0.5 m³ / h; PTFE filter element specification 0.02 microns.

[0033] Final product: 99.9994% n-butyl acetate content, 12 ppm moisture, 1.2 ppm total metal ion content, and ≤3 particles (≥0.2 μm) / mL. It also meets electronic grade requirements.

[0034] Comparative Example 1 (Ion exchange pretreatment, otherwise the same as Example 1) The overall structure is consistent with Example 1, except that: The ion exchange unit was placed before the distillation unit, in the following sequence: pretreatment → ion exchange → distillation → filtration → storage. The final product contained 0.5 ppm calcium ions and 0.4 ppm magnesium ions, but trace amounts of n-butanol (0.02%) and moisture (25 ppm) were detected, and the n-butyl acetate content was only 99.992%. Furthermore, due to evaporation entrainment during the distillation process, a small amount of metal ions were again carried into the product, resulting in a final total metal ion content of 2.5 ppm. This indicates that pre-treatment with ion exchange cannot effectively prevent secondary contamination that may be introduced by the distillation unit.

[0035] Comparative Example 2 (The distillation column uses ordinary metal plate corrugated packing) The overall structure is consistent with Example 1, except that: The packing material in the distillation column was replaced with ordinary 304 stainless steel perforated corrugated packing (specific surface area 250 m² / m³). The results showed that the main fraction contained a high residue of n-butanol (0.08%) and 35 ppm of water. The removal efficiency of metal ions after distillation decreased significantly (calcium ion residue 3.2 ppm). This indicates that the ordinary packing material is insufficient for separating this system and cannot achieve electronic-grade purity.

[0036] Comparative Example 3 (No terminal PTFE filter) The overall structure is consistent with Example 1, except that: The S4 filtration step was omitted. The final product contained a particle count (≥0.2μm) as high as 280 particles / mL, and visible trace precipitates appeared after one week of storage (presumably fragments of ion exchange resin or pipe debris), failing to meet the electronic grade cleanliness requirements.

[0037] In summary, this invention achieves stable, efficient, and continuous production of industrial-grade n-butyl acetate into electronic-grade products through a specific sequence and parameter matching of "pretreatment (adsorption + dehydration) → precision distillation (BX packing + staged extraction) → ion exchange (post-purification) → terminal PTFE filtration → nitrogen sealing storage". There are significant synergistic effects between the steps, rather than simple functional superposition.

[0038] The above description is merely a preferred embodiment of the present invention and does not limit the scope of the patent. Any equivalent structural or procedural modifications made based on the content of this specification, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of this invention.

Claims

1. A method for preparing electronic-grade n-butyl acetate, characterized in that, Includes the following stages: S1: Preprocessing stage ① Add industrial-grade n-butyl acetate raw material to the pretreatment tank, wherein the mass content of n-butyl acetate in the raw material is not less than 97%; ② Add impurity removal additive to the pretreatment tank. The additive consists of activated carbon and anhydrous magnesium sulfate. Start the agitator and stir at a speed of 80-150 rpm for 2-3 hours. ③ The mixed materials are filtered through a multi-layer filter membrane in the outlet pipe of the pretreatment tank. The filter membrane has a pore size of 0.5-2 micrometers to obtain the pretreatment liquid. S2: Distillation Stage ① The pretreated liquid obtained in S1③ is transported to the distillation column of the distillation unit, and the pressure inside the distillation column is controlled to be atmospheric pressure; ② Set the temperature of the bottom heater of the distillation column to 130-140℃, the temperature of the top of the column to 100-105℃, the reflux ratio to 10:3-5, and start collecting the fraction into the fore-fraction tank after reflux time of 3-5 hours; ③ Set the bottom heater temperature to 130-145℃, the top temperature to 105-110℃, and the reflux ratio to 10:3-5. Collect the distillate and send it into the main fraction tank to obtain the distillate liquid. S3: Ion exchange stage The distillate obtained in S2③ is transported to the ion exchange device under positive pressure, and passes through the cation exchange resin layer at a flow rate of 0.4-0.8 cubic meters / hour to remove Ca²⁺ and Mg²⁺ metal ions, thus obtaining the ion exchange solution. S4: Filtering Stage The ion exchange solution obtained in S3 is transported to the filtration device under positive pressure. It is filtered through multiple layers of filter membranes in the upper layer of the filter box and polytetrafluoroethylene filter cartridges in the lower layer. The filter cartridges have a size of 0.02-0.1 microns and the filtration pressure is 5-7 kPa to obtain the filtrate. S5: Storage Phase After purging the storage device three times with vacuum nitrogen, the filtrate obtained in S4 is transferred to the storage device and stored under high-purity nitrogen protection to obtain electronic-grade n-butyl acetate product.

2. The preparation method according to claim 1, characterized in that, The mass ratio of activated carbon to anhydrous magnesium sulfate added in S1② is 0.2-0.5 kg of activated carbon and 1.5-2.5 kg of anhydrous magnesium sulfate per 300 kg of n-butyl acetate raw material.

3. The preparation method according to claim 1, characterized in that, The BX metal wire mesh packing filled in the distillation column described in S2 is a structured packing with an effective specific surface area of ​​500-700 m² / m³.

4. The preparation method according to claim 1, characterized in that, The cation exchange resin mentioned in S3 is a D001 macroporous strong acid styrene-based cation exchange resin with a working exchange capacity of not less than 1300 mmol / L and a regenerator dosage of 40-100 kg / m³.

5. The preparation method according to claim 1, characterized in that, The filtration device described in S4 is a filter box made of stainless steel. The filter box is divided into upper and lower layers. The upper layer contains multiple layers of filter membranes, and the lower layer contains filter elements.

6. The preparation method according to any one of claims 1-5, characterized in that, The final electronic-grade n-butyl acetate product has a n-butyl acetate content of not less than 99.999% and a total metal ion content of less than 10 ppm.

7. An apparatus for preparing electronic-grade n-butyl acetate for carrying out the method according to any one of claims 1-6, characterized in that, The equipment is arranged in the production sequence as follows: a pretreatment unit, a distillation unit, an ion exchange unit, a filtration unit, and a storage unit. The material conveying pipelines between the units are all made of EP-grade electropolished stainless steel and are equipped with inert gas protection interfaces.