阅读说明：本技术 一种对苯二甲酸二异辛酯连续法汽提脱醇方法 (Continuous stripping dealcoholization method of diisooctyl terephthalate ) 是由 曹正国 王福 荆晓平 李江华 储阳阳 于 2019-11-07 设计创作，主要内容包括：本发明公开了化工生产技术领域内的一种对苯二甲酸二异辛酯连续法汽提脱醇方法,其将对苯二甲酸与过量异辛醇催化酯化反应后的对苯二甲酸二异辛酯粗成品经过碱洗水洗后,经汽提进料加热器加热至于165-175℃后,通过进料分配器供入汽提脱醇塔内的上填料层和下填料层之间；维持塔体内压力1-6KPa,塔顶温度为140-150℃,经汽提后获得苯二甲酸二异辛酯。其具有产品质量好,脱醇效率高,安全系数高,能耗低的特点,该方法专用于对苯二甲酸二异辛酯的连续脱醇提纯生产。(The invention discloses a continuous stripping dealcoholization method of diisooctyl terephthalate, which belongs to the technical field of chemical production, and comprises the steps of washing crude diisooctyl terephthalate after catalytic esterification reaction between terephthalic acid and excessive isooctanol with alkali, heating the washed crude diisooctyl terephthalate to the temperature of 165-175 ℃ by a stripping feeding heater, and feeding the heated crude diisooctyl terephthalate to a position between an upper packing layer and a lower packing layer in a stripping dealcoholization tower through a feeding distributor; maintaining the pressure in the tower body at 1-6KPa and the temperature at the top of the tower at 140-. The method has the characteristics of good product quality, high dealcoholization efficiency, high safety coefficient and low energy consumption, and is specially used for continuous dealcoholization and purification production of the diisooctyl terephthalate.)

1. A continuous stripping dealcoholization method of diisooctyl terephthalate is characterized by comprising the following steps:

(1) after the crude product of diisooctyl terephthalate after the catalytic esterification reaction of terephthalic acid and excessive isooctanol is washed by alkali, heated to 165-175 ℃ by a stripping feeding heater and then fed into a stripping dealcoholization tower between an upper packing layer and a lower packing layer through a feeding distributor; the stripping dealcoholization tower comprises a tower body, an upper filler layer, a middle filler layer and a lower filler layer are respectively arranged at the upper section, the middle section and the lower section in the tower body, and the feeding distributor is positioned between the upper filler layer and the middle filler layer; the top of the tower body is provided with a gas phase outlet which is connected to a condenser; an overheated steam distributor and an upper heat-conducting oil heat exchange coil are arranged between the middle packing layer and the lower packing layer in the tower body, and the overheated steam distributor is positioned above the upper heat-conducting oil heat exchange coil; a lower layer heat conduction oil heat exchange coil is arranged below the lower packing layer in the tower body; a discharge hole at the bottom of the tower body is connected to a sealed buffer tank, and the sealed buffer tank is connected with a stripping discharge pump; the outlet of the condenser is connected to a front fraction receiving tank, and the top of the front fraction receiving tank is connected to a tail gas pipe through a vacuum pump;

(2) the vacuum pump continuously works, the pressure in the tower body is maintained to be 1-6KPa, the temperature at the top of the tower is 140-150 ℃, and light components from the gas phase outlet are condensed into liquid by the condenser and are pumped into the front fraction receiving groove;

(3) between the upper packing layer and the lower packing layer, water and isooctanol are evaporated, the water and isooctanol pass through the upper packing layer in an upward mode and continuously leave from the gas phase outlet, and diisooctyl terephthalate with gradually increased content passes through the middle packing layer in a downward mode;

(4) the superheated steam distributor continuously supplies superheated steam, the superheated steam uniformly stirs the surrounding diisooctyl terephthalate, and in the filler layer, the upward superheated steam is fully contacted with the downward diisooctyl terephthalate to promote the isooctanol to further evaporate;

(5) the diisooctyl terephthalate continuously descends to the upper-layer heat transfer oil heat exchange coil area, the temperature of the upper-layer heat transfer oil heat exchange coil is kept at 160-170 ℃, and water and isooctanol are further distilled and ascend;

(6) the diisooctyl terephthalate continuously descends and penetrates through the lower packing layer, then reaches the area of the heat transfer oil heat exchange coil at the lower layer, the temperature of the heat transfer oil heat exchange coil at the lower layer is kept at 175-180 ℃, and the residual water and isooctanol are further distilled and removed;

(7) the diisooctyl terephthalate after the steps leaves from the bottom of the tower and enters a sealed buffer tank, and is discharged by a stripping discharge pump after being filled with liquid.

2. The continuous process for stripping and dealcoholizing diisooctyl terephthalate as claimed in claim 1, wherein a defoaming net is arranged in the tower body above the upper packing layer.

3. The continuous diisooctyl terephthalate stripping dealcoholization method according to claim 1 or 2, characterized in that the sealed buffer tank is previously purged with nitrogen.

4. The continuous stripping dealcoholization method for diisooctyl terephthalate according to the claim 1 or 2, characterized in that the stripping dealcoholization tower is pre-filled with nitrogen before being started.

Technical Field

The invention relates to a stripping dealcoholization process, in particular to a continuous stripping dealcoholization process adopting diisooctyl terephthalate. Belongs to the technical field of chemical production.

Background

Diisooctyl terephthalate (DOTP) is a main plasticizer with excellent performance for polyvinyl chloride (PVC) plastics. Compared with the common di-isooctyl phthalate (DOP), the poly (p-dioctyl phthalate) has the advantages of high temperature resistance, low temperature resistance, difficult volatilization, seepage resistance, good flexibility, good electrical insulation property and the like, and shows excellent durability, soap water resistance and low-temperature flexibility in products. Due to the excellent performance of DOTP, the material can completely meet the requirement of temperature resistance grade of wires and cables, and is widely applied to the production of wire and cable materials (International electrotechnical Commission IEC standard) resistant to 70 ℃ and other various PVC soft products. DOTP can also be used in the production of artificial leather films. Further, it has excellent compatibility and is also useful for plasticizers of acrylonitrile derivatives, polyvinyl butyral, nitrile rubber, cellulose nitrate, synthetic rubber, etc., coating additives, lubricants, paper softeners, etc.

The existing industrial production process of diisooctyl terephthalate comprises the working procedures of esterification, alkali washing and water washing, dealcoholization and filtration. Wherein the dealcoholization process mainly adopts a batch still type vacuum dealcoholization method.

CN108530299A discloses a method for efficiently producing diisooctyl terephthalate, which comprises the following steps: a) adding isooctanol into a reaction kettle, stirring, adding terephthalic acid while stirring, heating the reaction kettle to 150-170 ℃, adding a catalyst, and performing esterification reaction to form a reaction solution; b) carrying out vacuum distillation treatment on the reaction solution; c) and filtering the reaction liquid after the vacuum distillation treatment to obtain the diisooctyl terephthalate.

CN108126364A discloses a rectifying still for production of diisooctyl terephthalate, including the cauldron body, cauldron body upper portion is equipped with the feed inlet, and the lower part is equipped with the row cinder notch, and the internal heating jacket that is equipped with of cauldron, heating jacket upper end are equipped with the one deck perforated plate.

CN108101782A discloses a preparation method of diisooctyl terephthalate, which comprises adding purified terephthalic acid and raw material alcohol into a reaction kettle, and then adding catalysts, namely tetrabutyl titanate and octanol into the reaction kettle in batches by stages along with the rise of temperature; and finally, adding SiO2 and Al2O3, dealcoholizing in vacuum after the reaction is finished, adding Na2CO3 after the dealcoholization is finished, and finally adding activated carbon and performing suction filtration to obtain the product.

CN108329206A discloses a preparation method of environment-friendly plasticizer diisooctyl terephthalate. Terephthalic acid and isooctyl alcohol are adopted as main raw materials, and are continuously added into a reaction kettle in the presence of a composite esterification catalyst for esterification reaction after being heated in a preheating kettle, and the specific operation flow comprises the steps of raw material preheating, esterification reaction, negative pressure dealcoholization, alkali addition neutralization, water washing, steam stripping, adsorption decoloration and filtration. Meanwhile, the invention particularly adopts a novel process of the composite catalyst, and has the advantages of high esterification conversion rate, small using amount of the catalyst and recycling.

The above patents all provide a batch vacuum dealcoholization process. The disadvantages are that: the existing diisooctyl terephthalate stripping dealcoholization process comprises the following steps: 1) the time of the stripping dealcoholization procedure is long; 2) the stripping dealcoholization process is easy to generate acid reversal, and the alcohol content is higher, so that the product quality is unstable.

Disclosure of Invention

The invention aims to provide a continuous stripping dealcoholization method of diisooctyl terephthalate, which can realize continuous dealcoholization and improve the stripping dealcoholization efficiency.

The purpose of the invention is realized as follows: a continuous stripping dealcoholization method of diisooctyl terephthalate comprises the following steps:

(1) after the crude product of diisooctyl terephthalate after the catalytic esterification reaction of terephthalic acid and excessive isooctanol is washed by alkali, heated to 165-175 ℃ by a stripping feeding heater and then fed into a stripping dealcoholization tower between an upper packing layer and a lower packing layer through a feeding distributor; the stripping dealcoholization tower comprises a tower body, an upper filler layer, a middle filler layer and a lower filler layer are respectively arranged at the upper section, the middle section and the lower section in the tower body, and the feeding distributor is positioned between the upper filler layer and the middle filler layer; the top of the tower body is provided with a gas phase outlet which is connected to a condenser; an overheated steam distributor and an upper heat-conducting oil heat exchange coil are arranged between the middle packing layer and the lower packing layer in the tower body, and the overheated steam distributor is positioned above the upper heat-conducting oil heat exchange coil; a lower layer heat conduction oil heat exchange coil is arranged below the lower packing layer in the tower body; a discharge hole at the bottom of the tower body is connected to a sealed buffer tank, and the sealed buffer tank is connected with a stripping discharge pump; the outlet of the condenser is connected to a front fraction receiving tank, and the top of the front fraction receiving tank is connected to a tail gas pipe through a vacuum pump;

(2) the vacuum pump continuously works, the pressure in the tower body is maintained to be 1-6KPa, the temperature at the top of the tower is 140-150 ℃, and light components from the gas phase outlet are condensed into liquid by the condenser and are pumped into the front fraction receiving groove;

(3) between the upper packing layer and the lower packing layer, water and isooctanol are evaporated, the water and isooctanol pass through the upper packing layer in an upward mode and continuously leave from the gas phase outlet, and diisooctyl terephthalate with gradually increased content passes through the middle packing layer in a downward mode;

(4) the superheated steam distributor continuously supplies superheated steam, the superheated steam uniformly stirs the surrounding diisooctyl terephthalate, and in the filler layer, the upward superheated steam is fully contacted with the downward diisooctyl terephthalate to promote the isooctanol to further evaporate;

(5) the diisooctyl terephthalate continuously descends to the upper-layer heat transfer oil heat exchange coil area, the temperature of the upper-layer heat transfer oil heat exchange coil is kept at 160-170 ℃, and water and isooctanol are further distilled and ascend;

(6) the diisooctyl terephthalate continuously descends and penetrates through the lower packing layer, then reaches the area of the heat transfer oil heat exchange coil at the lower layer, the temperature of the heat transfer oil heat exchange coil at the lower layer is kept at 175-180 ℃, and the residual water and isooctanol are further distilled and removed;

(7) the diisooctyl terephthalate after the steps leaves from the bottom of the tower and enters a sealed buffer tank, and is discharged by a stripping discharge pump after being filled with liquid.

Compared with the prior art, the invention is beneficial to rapid dealcoholization by increasing the evaporation area of materials, can effectively remove trace alcohol in products by steam stripping, improves the product quality, can obviously provide the production efficiency, and provides technical support for large-scale industrial production of diisooctyl terephthalate. The method has the characteristics of good product quality, high dealcoholization efficiency, high safety coefficient and low energy consumption. The test result of the finished product shows that the alcohol content is 20-60ppm, the acid value is 0.01-0.03mgKOH/g, and the method is specially used for the continuous dealcoholization and purification production of the diisooctyl terephthalate.

In order to prevent floating foam, a foam removing net is arranged above the upper packing layer in the tower body. The floating foam carrying with the diisooctyl terephthalate can be avoided flowing out from the gas phase outlet, and the recovery efficiency of the finished product is further reduced.

In order to prevent the high-temperature materials from being oxidized when contacting with air, the sealed buffer tank is previously purged by nitrogen.

In order to avoid the contact of the materials with air, nitrogen is filled in advance before the stripping dealcoholization tower is started. Under the protection of nitrogen, the material is heated and then enters a stripping dealcoholization tower, and the nitrogen is pumped by a vacuum pump, so that the material is prevented from being contacted with oxygen in the air.

Drawings

FIG. 1 is a flow chart of the present invention.

In the figure, 1 gas phase outlet, 2 defoaming nets, 3 upper packing layers, 4 feeding distributors, 5 packing layers, 6 superheated steam distributors, 7 upper heat transfer oil heat transfer coils, 8 lower packing layers, 9 lower heat transfer oil heat transfer coils, 10 emptying pipes, 11 nitrogen inlet pipes, R103 alkaline washing water washing kettles, H301 stripping feeding heaters, H302 steam heaters, T301 stripping dealcoholization towers, P301 stripping feeding pumps, P302 stripping discharging pumps, V301 sealing buffer tanks, W301 condensers, W101 vacuum pumps, V105 front fraction receiving tanks and V101 front fraction water sealing tanks.

Detailed Description