阅读说明：本技术 一种环己醇脱氢原料的精制方法 (Refining method of cyclohexanol dehydrogenation raw material ) 是由 周小文 刘洪武 潘罗其 黎树根 余卫勋 邓琼 肖泽威 于 2019-03-06 设计创作，主要内容包括：本发明公开了一种环己醇脱氢原料的精制方法,包括以下步骤：1)在一个带侧线采出的粗酮塔之中对来自粗醇槽中的粗环己醇溶液进行减压精馏,粗酮塔塔顶馏出液返回至粗醇酮槽,侧线采出液进入常压塔,粗酮塔釜液返回至粗醇槽；2)所述侧线采出液在常压塔中进行常压精馏分离,常压塔塔顶馏出液返回至粗醇槽中,常压塔釜液排出。该方法能逐渐降低粗环己醇中的环己酮和中间组分的含量,减少其在环己醇脱氢系统的无效循环,提高脱氢过程中环己醇的转化率和环己酮的选择性,提高环己醇脱氢装置的产能。(The invention discloses a refining method of cyclohexanol dehydrogenation raw materials, which comprises the following steps: 1) carrying out reduced pressure rectification on a crude cyclohexanol solution from a crude alcohol tank in a crude ketone tower with a side line extraction, returning the distillate at the top of the crude ketone tower to the crude alcohol ketone tank, feeding the side line extraction liquid to an atmospheric tower, and returning the residue of the crude ketone tower to the crude alcohol tank; 2) and the side-draw liquid is subjected to normal-pressure rectification separation in the normal-pressure tower, the distillate at the top of the normal-pressure tower returns to the crude alcohol tank, and the kettle liquid of the normal-pressure tower is discharged. The method can gradually reduce the content of cyclohexanone and intermediate components in the crude cyclohexanol, reduce the ineffective circulation of the crude cyclohexanol in a cyclohexanol dehydrogenation system, improve the conversion rate of cyclohexanol and the selectivity of cyclohexanone in the dehydrogenation process, and improve the capacity of a cyclohexanol dehydrogenation device.)

1. A refining method of cyclohexanol dehydrogenation raw materials comprises the following steps:

1) carrying out reduced pressure rectification on a crude cyclohexanol solution from a crude alcohol tank in a crude ketone tower with a side line extraction, returning the distillate at the top of the crude ketone tower to the crude alcohol ketone tank, feeding the side line extraction liquid to an atmospheric tower, and returning the residue of the crude ketone tower to the crude alcohol tank;

2) and the side-draw liquid is subjected to normal-pressure rectification separation in the normal-pressure tower, the distillate at the top of the normal-pressure tower returns to the crude alcohol tank, and the kettle liquid of the normal-pressure tower is discharged.

2. The method of claim 1, wherein: in the step 1), the crude ketone tower is a clapboard rectifying tower.

3. The method of claim 1, wherein: in the step 1), the amount of the crude cyclohexanol solution from the crude alcohol tank is 1-10% of cyclohexanol dehydrogenation feeding amount in the production device.

4. The method of claim 1, wherein: in the step 1), the pressure at the top of the crude ketone tower is 1-10 kPa; the reflux ratio is 10-100; the temperature of the tower top is 40-80 ℃; the temperature of the tower kettle is 70-120 ℃.

5. The method of claim 4, wherein: the distillate at the top of the crude ketone tower mainly contains cyclohexanone, and the total content of the cyclohexanol and the intermediate components is not higher than 3%; cyclohexanol is mainly used in the crude ketone tower bottom liquid, the content of the cyclohexanone is not higher than 1%, and the total content of the intermediate components is not higher than 3%; the side-draw liquid mainly comprises cyclohexanol and intermediate components, wherein the total content of the intermediate components is not less than 20%, and the content of cyclohexanone is not more than 1%.

6. The method of claim 1, wherein: in the step 2), the tower top pressure of the atmospheric tower is normal pressure, and the reflux ratio is 5-20; the temperature of the tower top is 155-165 ℃; the temperature of the tower kettle is 200-220 ℃.

7. The method of claim 6, wherein: in the step 2), the reflux ratio of the atmospheric tower is 10-15.

8. The method of claim 6, wherein: in the step 2), the temperature of a tower kettle of the atmospheric tower is 205-215 ℃.

9. The method according to any one of claims 6-8, wherein: the total content of the intermediate components in the distillate at the top of the atmospheric tower is not higher than 3%, and the content of cyclohexanol in the bottom liquid of the atmospheric tower is not higher than 3%.

Technical Field

The invention relates to a refining method of cyclohexanol dehydrogenation raw materials, belonging to the field of cyclohexanone preparation.

Background

Cyclohexanone is produced by oxidation of cyclohexane, typically by the following steps:

(1) oxidizing cyclohexane with molecular oxygen-containing gas to produce cyclohexane oxidizing liquid containing cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone and other matters;

(2) treating cyclohexane oxidation liquid with alkaline solution to decompose cyclohexyl hydroperoxide therein to produce cyclohexanol and cyclohexanone, while neutralizing acid in the oxidation liquid and saponifying ester;

(3) evaporating unreacted cyclohexane for recycling, and feeding the rectification kettle liquid without cyclohexane and a cyclohexanol dehydrogenation product into a crude alcohol ketone tank;

(4) the material extracted from the crude alcohol ketone groove enters a light tower for vacuum rectification, the component which is easier to volatilize than cyclohexanone is separated from the top of the tower, and the cyclohexanone, the cyclohexanol and the component which is harder to volatilize than cyclohexanone are discharged from the bottom of the tower;

(5) the material in the light tower bottom enters a ketone tower for vacuum rectification, the product cyclohexanone is obtained from the tower top, and cyclohexanol and components which are more difficult to volatilize than cyclohexanone are discharged from the tower bottom;

(6) the ketone tower bottom liquid enters an alcohol tower for vacuum rectification, the component which is more volatile than cyclohexanol is distilled out from the top of the tower together with the cyclohexanol, the distilled component is sent to a crude alcohol tank, and the component which is less volatile than the cyclohexanol is discharged from the tower bottom;

(7) and (3) leading out the material from the crude alcohol tank to a cyclohexanol dehydrogenation process, wherein part of cyclohexanol is dehydrogenated into cyclohexanone, and a dehydrogenation product is led into the crude alcohol ketone tank and is used as a raw material of the light tower together with the bottom liquid of the alkane tower.

As can be seen from the above typical process for cyclohexanone production, substances produced from cyclohexane oxidation and cyclohexanol dehydrogenation and having volatility between cyclohexanone and cyclohexanol under the operating conditions of the respective rectification columns cannot be removed from the rectification process, and are gradually accumulated in the rectification system, which affects cyclohexanone production, and these substances are collectively referred to as intermediate components.

These volatility components in the intermediate between cyclohexanone and cyclohexanol are mostly impurities with a higher boiling point than cyclohexanol at atmospheric pressure, which distill together with cyclohexanol from the top of the column due to azeotropy with cyclohexanol under column rectification conditions, resulting in a gradual increase in the content of the intermediate components in the crude alcohol tank feed, often exceeding 10% in total. In the existing method, when a device is overhauled or stopped, a component with higher content of an intermediate component in a crude alcohol ketone tank and a crude alcohol tank is treated as a waste material, and the content of the intermediate component in a rectification material is gradually increased after normal driving. These intermediate components, when present in high amounts, can adversely affect cyclohexanone production: firstly, the substances are evaporated in an alcohol tower, energy is consumed, then the substances enter a cyclohexanol dehydrogenation process along with cyclohexanol, return to a crude alcohol ketone tank after evaporation, temperature rise, reaction and temperature reduction, and enter a light tower, a ketone tower and the alcohol tower again, so that ineffective circulation of the materials is caused, the energy consumption is increased, and the equipment space is occupied by extrusion; secondly, when the content of the impurities is high, a small amount of the impurities enter a cyclohexanone product at the top of the ketone tower, so that the quality of the cyclohexanone is reduced; thirdly, in order to ensure the quality of the cyclohexanone, the content of the cyclohexanone in the material in the ketone tower bottom has to be increased, so that excessive cyclohexanone is brought into the cyclohexanol dehydrogenation raw material, the conversion rate of the cyclohexanol in the dehydrogenation process is reduced, the condensation side reaction of the cyclohexanone is increased, and the selectivity of cyclohexanol dehydrogenation is reduced; and fourthly, the crude alcohol ketone material with higher content of the intermediate components and the crude alcohol material are treated as waste materials during the parking period, so that the material consumption of cyclohexanone production is increased.

The amount of the intermediate components produced is small, and in the case of a 10 ten thousand ton/year cyclohexanone device, the amount of the intermediate components produced is about 40 tons/year, and 5kg/h, so that the concentration of the intermediate components in the rectification system can be kept constant only by removing the intermediate components at a rate of 5 kg/h.

Wushohui, petrochemical 1983,12(10):642-649, states that the impurities contained in cyclohexanol increase the thermal instability of cyclohexanol itself, and that the high-boiling-point content increases by 3-4% when 90-91% of industrially rectified cyclohexanol is passed through a superheater, while almost no change occurs when 98-98.8% of cyclohexanol is used. When industrially rectified cyclohexanol is used, the dehydrogenation selectivity is reduced by about 4% as compared with pure cyclohexanol, so that the cyclohexanol dehydrogenation feed should be refined to minimize the impurity content of cyclohexanol, for example, by adding a cutting column to the rectification system of ketone alcohol, but no specific method is given.

Chinese patent 201620707871.1 discloses a device for removing impurities in butyl cyclohexyl ether in the production process of cyclohexanone, which is to add a rectifying tower behind a cyclohexanol evaporator to carry out normal pressure or pressure rectification on crude cyclohexanol, and discharge part of butyl cyclohexyl ether from the tower bottom to a recombination separation tank, thereby achieving the purpose of reducing the content of intermediate components in the crude cyclohexanol. But the content of the butyl cyclohexyl ether in the discharged tower bottom liquid is only 25-35%, and the rest of the components are cyclohexanol, which means that cyclohexanol which is 2-3 times of the butyl cyclohexyl ether is treated as a byproduct, and the material consumption is increased. In addition, the problem of too high a content of cyclohexanone in the crude cyclohexanol still remains.

Chinese patent 201610837394.5 discloses a process for preparing cyclohexanone by cyclohexanol dehydrogenation, wherein the equipment of the cyclohexanol dehydrogenation process consists of a cyclohexanol evaporator, a vapor-liquid separator, a normal-pressure or pressurized rectifying tower and a cyclohexanol dehydrogenation reactor; the rectifying tower is only provided with a stripping section, and the tower kettle is provided with a reboiler. The process can greatly reduce the concentration of the methylcyclohexanone, the heptanone and the analogues thereof contained in the materials of the cyclohexanone rectification process and the cyclohexanol dehydrogenation process, and reduce the circulation and accumulation of the methylcyclohexanone, the heptanone and the analogues thereof in the cyclohexanone rectification process and the cyclohexanol dehydrogenation process. However, the process can not reduce the content of cyclohexanone in the cyclohexanol raw material, and the material discharged from the tower still contains about 30% of cyclohexanol, so that the material consumption is increased. In addition, the removal of these impurities from the column bottom at very low levels under atmospheric or pressurized conditions requires high energy consumption.

The common point of the patents is that the intermediate components are removed from the tower bottom only by normal pressure or pressure rectification, and under the condition that the content of the intermediate components in the raw materials is not high, the impurities are removed from the tower bottom, and more energy is consumed, for example, when the material containing 90 percent of cyclohexanol and 10 percent of intermediate components is rectified under normal pressure or pressure, the reflux ratio is set to be 4, and at least 45 parts of cyclohexanol is required to be evaporated when 1 part of the intermediate components is removed; if the reflux ratio is 4 during the normal pressure or pressurized rectification of the material containing 96% cyclohexanol and 4% intermediate component, at least 120 parts of cyclohexanol need to be evaporated every 1 part of intermediate component is removed, and the energy consumption is increased sharply.

Meanwhile, cyclohexanol dehydrogenation is an endothermic equilibrium reaction, and increasing the concentration of cyclohexanone in the raw material can shift the equilibrium towards the raw material direction, so that the productivity of cyclohexanol dehydrogenation is reduced, and therefore, the concentration of cyclohexanone in the raw material should be reduced as much as possible. Limited by the separation capacity of the intermediate product and the ketone tower, in order to ensure the quality of cyclohexanone as a ketone top product, the concentration of cyclohexanone in the material in the bottom of the ketone tower is often controlled to be more than 4%, sometimes as high as 8%, even as high as 10%, so that the cyclohexanone in the material in the bottom of the ketone tower needs to be separated.

Disclosure of Invention

Aiming at the problem that the content of cyclohexanone and intermediate components in the conventional cyclohexanol dehydrogenation raw material is too high, the invention aims to provide a method for refining the cyclohexanol dehydrogenation raw material.

In order to achieve the above object, the present invention provides a method for refining cyclohexanol dehydrogenation raw material, comprising the steps of:

1) carrying out reduced pressure rectification on a crude cyclohexanol solution from a crude alcohol tank in a crude ketone tower with a side line extraction, returning the distillate at the top of the crude ketone tower to the crude alcohol ketone tank, feeding the side line extraction liquid to an atmospheric tower, and returning the residue of the crude ketone tower to the crude alcohol tank;

2) and the side-draw liquid is subjected to normal-pressure rectification separation in the normal-pressure tower, the distillate at the top of the normal-pressure tower returns to the crude alcohol tank, and the kettle liquid of the normal-pressure tower is discharged.

Preferably, in the step 1), the crude ketone column is a baffle distillation column. The partition is positioned in the middle of the crude ketone tower and is vertically arranged to divide the crude ketone tower into four areas, the upper part of the partition is a public rectification section, the left side of the partition is a feeding section, the right side of the partition is a lateral line extraction section, and the lower part of the partition is a public stripping section.

The invention preferably adopts the clapboard rectifying tower, saves equipment investment and energy consumption, and can better separate the side-draw liquid of the distillate at the top of the tower and the tower bottom liquid, thereby better achieving the purpose of impurity removal and purification of the invention.

Preferably, in the step 1), the amount of the crude cyclohexanol solution from the crude alcohol tank is 1-10 wt%, preferably 1-5 wt% of cyclohexanol dehydrogenation feeding amount in the production device.

Preferably, in the step 1), the pressure at the top of the crude ketone tower is 1-10 kPa, preferably 2-5 kPa; the reflux ratio is 10-100, preferably 30-60; the temperature at the top of the tower is 40-80 ℃, and preferably 45-60 ℃; the temperature of the tower kettle is 70-120 ℃, and preferably 85-105 ℃.

More preferably, the crude ketone tower top distillate is mainly cyclohexanone, and the total content of the cyclohexanol and the intermediate components is not higher than 3 wt%; cyclohexanol is mainly used in the crude ketone tower bottom liquid, the content of the cyclohexanone is not higher than 1 wt%, and the total content of the intermediate components is not higher than 3%; the side-draw liquid mainly comprises cyclohexanol and intermediate components, wherein the total content of the intermediate components is not less than 20 wt%, and the content of the cyclohexanone is not more than 1 wt%.

Preferably, in the step 2), the top pressure of the atmospheric tower is normal pressure, the reflux ratio is 5-20, and preferably 10-15; the tower top temperature is 155-165 ℃, and preferably 158-163 ℃; the temperature of the tower kettle is 200-220 ℃, preferably 205-215 ℃.

More preferably, the total content of the intermediate components in the atmospheric tower overhead distillate is not more than 3 wt%, and the cyclohexanol content in the atmospheric tower bottoms is not more than 3 wt%.

Compared with the prior art, the technical scheme of the invention has the beneficial technical effects that:

1) according to the technical scheme of the invention, the material extracted from the crude alcohol tank only accounts for 1-10 wt% of the total amount of the material, the treated refined cyclohexanol solution returns to the crude alcohol tank, the original process is not required to be changed, the influence on an original production device is small, the content of intermediate components in the crude cyclohexanol solution can be gradually reduced and finally maintained in a lower content range, the material composition in the rectification process and the cyclohexanol dehydrogenation process tends to be stable, and the stable operation of the device is facilitated.

2) According to the technical scheme of the invention, the content of the intermediate component in the crude cyclohexanol solution can be maintained in a lower range, the content of cyclohexanone in the material in the ketone tower kettle can be properly reduced while the quality of cyclohexanone in the ketone tower top product is ensured, and the content of cyclohexanone in the cyclohexanol dehydrogenation raw material is reduced, so that the cyclohexanol content in the cyclohexanol dehydrogenation raw material is improved, the processing capacity of a cyclohexanol dehydrogenation device is increased, the dimerization of cyclohexanone is reduced, and the selectivity of the dehydrogenation process is improved.

3) According to the technical scheme of the invention, the content of the intermediate components in the crude cyclohexanol solution is low, and the content of cyclohexanone is reduced, so that the caused ineffective evaporation and the heat loss in the processes of temperature rising and temperature lowering are reduced, and the energy consumption is reduced.

4) According to the technical scheme of the invention, the ketone removal and the concentration of the intermediate components are carried out in one rectifying tower, so that the number of equipment is reduced, the flow is simplified, and the energy consumption is reduced.

5) According to the technical scheme of the invention, by utilizing the characteristic that the intermediate component and cyclohexanol are subjected to azeotropic distillation in a certain vacuum range, the intermediate component is concentrated to more than 20 wt% and then is subjected to normal-pressure rectification, compared with the direct normal-pressure or pressurized rectification of a crude cyclohexanol solution, the processing capacity of a normal-pressure tower is greatly reduced, the energy consumption is greatly reduced, and meanwhile, the cyclohexanol content in the intermediate component discharged from the kettle of the normal-pressure tower is also greatly reduced, and the material consumption is also greatly reduced.

Drawings

FIG. 1 is a schematic process flow diagram of the present invention;

wherein: 1. crude alcohol tank, 11, alcohol tower top distillate, 12, material of cyclohexanol dehydrogenation process, 13, crude cyclohexanol solution, 2, crude ketone tower, 21, crude ketone tower top distillate, 22, crude ketone tower bottom liquid, 23, side-draw liquid, 3, atmospheric tower, 31, atmospheric tower top distillate, 32, atmospheric tower bottom liquid.

Detailed Description

The following examples are intended to further illustrate the present disclosure in conjunction with the accompanying drawings and not to limit the scope of the claims of the present disclosure.

In the embodiment of the invention, the diameter of a crude ketone tower 2 is 1.2m, 250Y fillers are filled in the crude ketone tower, a partition plate is arranged in the crude ketone tower or not arranged in the crude ketone tower, when the partition plate is arranged, the whole crude ketone tower is divided into 4 areas, the upper part of the partition plate is a common rectification section, the height of the fillers is 12m, the left side of the partition plate is a feeding section, the upper and lower parts of the partition plate are respectively filled with 6m fillers, the right side of the partition plate is a side line extraction section, the upper and lower parts of the partition plate are respectively filled with 6m fillers, the lower part of the partition plate is a common stripping section. The diameter of the atmospheric tower 3 is 0.3m, 250Y fillers are filled in the tower, the total height of the fillers is 24m, the tower is divided into an upper section and a lower section, the heights of the fillers are 10m and 14m in sequence, and the feeding materials are positioned between the two sections of the fillers.

Unless otherwise specified, the percentages in the following embodiments are by mass.