WO2005066110A1

WO2005066110A1 - Combined production of dialkyl carbonate and diol

Info

Publication number: WO2005066110A1
Application number: PCT/CN2003/001093
Authority: WO
Inventors: Wende Xiao
Original assignee: East China University Of Science And Technology
Priority date: 2003-10-16
Filing date: 2003-12-19
Publication date: 2005-07-21
Also published as: AU2003296198A1; CN1528735A; CN1241900C

Abstract

This invention relates to a process for combined production of dialkyl carbonate and diol with low energy consumption, which comprises the synthesis of alkylene carbonate, the generation of dialkyl carbonate and diol and the recovery of catalyst. This invention adopts petrochemical route, and optimizes the process flow and operating parameters on the basis of the prior art by using the whole synthetic process as a large-scale energy coupling usage system. This invention utilizes reaction heat of alkylene carbonate and heat pump technique, thereby the requisite amount of steam in said combined process is controlled below 1.0 ton per ton product. This invention optimizes the production process for the combined production of dialkyl carbonate and diol, and can greatly reduce the energy loss and the amount of cooling water. Compared to the same scale of manufacturing apparatus, said process can reduce the amounts of steam and cooling water by 50-90% and 40-60% respectively.

Description

Method for co-producing dialkyl carbonate and diol

Technical field

The present invention relates to a method for preparing a dialkyl carbonate (DAC), including dimethyl carbonate (DMC), diethyl carbonate (DEC), etc. ) alkyl, monohydric alcohols, such as methanol and ethanol, carbon dioxide and greenhouse exhaust gas as raw materials and power b (c) a diol and a dialkyl carbonate. Background technique

Dialkyl carbonates, such as dimethyl carbonate (DMC), are an "environmentally friendly", versatile organic chemical with low toxicity and are basically called a non-toxic chemical. It can replace dimethyl sulfate (hypertoxic) as a methylating agent and phosgene (hypertoxic) as a carbonylating agent. It can also be used as a gasoline additive to increase the octane number and oxygen content of gasoline (instead of methyl tert-butyl ether, of MTBE), may also be used as paint solvents, such as xylene and the like in place of ethyl or butyl acetate, which has high industrial application value.

There are many synthetic methods of dialkyl carbonate, but there are three main methods of industrial significance. The first is the petrochemical route, which synthesizes ethylene (propylene) carbonate, and then uses an alkyl alcohol for transesterification, and co-produces ethylene glycol or propylene glycol, also known as the transesterification method; the second is the coal chemical route, It is produced by the carbonylation reaction of a monovalent lower alcohol, such as methanol, with oxygen and carbon monoxide, also known as the carbonylation oxidation method. The third is the fertilizer route, which uses urea and a monovalent lower alcohol, such as methanol, to undergo an alcoholysis reaction. At the same time, ammonia is produced as a by-product.

Problems with traditional technology:

Synthesis of alkenyl carbonate, including propylene carbonate (PC) or ethylene carbonate (EC): The synthesis of alkenyl carbonate is a reversible reaction with a large amount of heat. The catalyst is tetraethylammonium bromide (C ₂ H ₅ ) ₄ N¾r- or KI. Thus, an effective measure to improve the conversion rate of the reaction is carried out with continuously lowering the reaction temperature. Traditional methods, such as US Patent No. 4,314,945, use the product alkenyl carbonate itself as a solvent, or diluent, where the alkenyl carbonate accounts for 85-99.6% (wt), and the reactor is a plurality of adiabatic reactions for heat exchange between sections.器 series connected. Due to the large exothermic reaction of the synthesis of alkenyl carbonate, which is 23 kcal / mol, a unit with an annual output of 100,000 tons of DMC is equivalent to 5 tons of steam per hour, and because of the temperature range of the reaction Wide, between 100-200 ° C, low pressure steam can be by-produced, but in the traditional technology, the heat of reaction is not well utilized.

Synthesis of difluorenyl carbonate: The synthesis of difluorenyl carbonate is based on the transesterification reaction of alkenyl carbonate and monoalcohol. The catalyst is a strong alkali sodium alkoxide dissolved in the reaction liquid, which belongs to a homogeneous catalytic reaction. There is a catalyst and a reaction material. Points Isolate and recycle the problem. Although a number of patents or literatures propose the use of insoluble solid bases, which constitute a heterogeneous catalytic process, such as US Patent No. 4,661,609, and Applied Catalysis: A, 2001, 259-266, there is no problem of catalyst separation. However, the reaction speed of a heterogeneous process is much lower than that of a homogeneous process. In the homogeneous case, the reaction equilibrium is accessible in about 10 minutes, and in the case of heterogeneous, typically takes several hours. Therefore, the heterogeneous process cannot meet the needs of large-scale production, and the homogeneous process can achieve large-scale production. However, one problem with the homogeneous process is the separation and recycling of the catalyst.

The second problem is that, corresponding to the allyl carbonate ester and a dihydric alcohol, such as propylene carbonate + propylene glycol, form an azeotrope, carbonic acid ester and the corresponding embankment monoalcohol also form an azeotrope, such as methanol and dimethyl carbonate Ester azeotrope has more complicated product separation problems. China patent ZL94112211.5 in the prior invention of the applicant, discloses a plate tower as the distillation column preclude the use of reaction distillation technology, can dilute carbonate ester starting material in the case of a monohydric alcohol in a stoichiometric ratio of more than complete conversion, the reaction at the bottom of the rectification column, there may be no allyl carbonate ester, PC / EC, eliminating the allyl carbonate ester diol and the corresponding azeotrope. However, in the original patent, the reaction temperature of the tower kettle was too high, being 185-190 ° F, which easily caused side reactions of ethylene glycol or propylene glycol at the bottom of the column.

When the amount of the monohydric alcohol is excessive, the top of the reaction distillation column can obtain a monohydric alcohol and a difluorenyl carbonate, such as a mixture of dimethyl carbonate and methanol. The two form an azeotrope, and there is a difficulty in separating the same. For the dimethyl carbonate process, the dimethyl carbonate content of the dimethyl carbonate + methanol azeotrope is 30%, the methanol is 70% (wt), and the azeotropic point is 63.8 ° C under normal pressure. A number of separation methods have been proposed in the prior art. Chinese Patent ZL94112211.5 in the prior invention of the applicant, discloses a technique to extractive distillation allyl carbonate ester extraction solvent. However, the published operating conditions have not been optimized. The molar ratio of the feed of the extractant to the azeotrope is relatively high, which is 1 to 2. The reflux ratio of the extraction refinery column is too large, and the energy consumption is still relatively high.

The third problem in the synthesis of dimethyl carbonate is that, due to the excessive use of monohydric alcohols, the molar ratio of alcohol to alkenyl carbonate is about 10, so the large amount of monohydric alcohols inevitably brings relatively high energy consumption, so The use of coupled heat utilization technologies such as heat pumps to recycle energy is significant for reducing production costs. Summary of the invention

The technical problem to be solved by the present invention is to disclose a method for co-producing dialkyl carbonate and diol to solve the problem of high energy consumption in the process through optimization of the process and process conditions.

The technical idea of the present invention is this-the technology of the present invention belongs to the petrochemical route, and on the basis of the original technology (such as the technology disclosed in the ZL94112211.5 patent), the process and operating parameters are optimized. Propylene Oxide, PO) or Ethylene Oxide (EO) with. ₀₂ as starting material, the whole process of synthesis of the dialkyl carbonate as a large use of energy coupling system, by using allyl carbonate ester reaction heat, and the heat pump technology, the synthetic co-production of dialkyl carbonate and two yuan The steam requirement of alcohol is controlled at a level of less than 1.0 ton per ton of product (total of difluorenyl carbonate and diol). Taking Propylene Oxide (PO) as an example, the basic reaction principle is as follows:

-OCH ₃

As a full process divided into two steps: (1). ₀₂ reacts with PO to form Propylene Carbonate (PC); (2) The transesterification reaction between methanol and PC simultaneously generates propylene glycol (Propylene Glycol, PG) and DMC. These two reactions are actually exothermic reversible reactions that are limited by equilibrium. The equilibrium constant of reaction (1) is about 1000, the heat of reaction is about 23 kcal / mol, and the heat of reaction (2) is about 0.01. The heat of reaction is very small. 2- 3kcal / moL

Therefore, the total reaction is 1 molecule of C0 ₂ , 1 molecule of propylene oxide and 2 molecules of methanol to generate 1 molecule of DMC and 1 molecule of PG. This process has the following two characteristics:

(1) Atomic utilization of 100%, a chemical reaction with zero emissions;

(2) Take greenhouse gas. ₀₂ as a raw material, recycling Po;

The method of the present invention includes the following steps:

Synthesis of alkenyl carbonate:

Reasonable use of reaction heat, by-product of 0.4-0.6Mpa (temperature around 150 ° C) steam, can be used as a heat source for the reboiler of the dialkyl carbonate synthesis part.

Synthesis of difluorenyl carbonate:

(1) The monoalcohol cycle uses steam instead of liquid. The azeotrope of the dialkyl carbonate and the monoalcohol entering the bottom of the extractive distillation column from the top of the reaction distillation column is steam, that is, the reaction distillation column is partially condensed. The product and reflux at the top of the extractive distillation column are first produced in the form of steam, without using a condenser. Alcohol vapor product after pressing unit directly to the bottom of the rectifying column reactor, as a reaction material recycled; monohydric alcohol vapor return portion of the compressed heated after rectification column as a reaction column kettle reboiler heat source, All alcohol cycles are used Heat pump makes full use of heat;

(2) Increasing the molar ratio of monoalcohol to alkenyl carbonate in the reaction distillation column, lowering the temperature of the column kettle, and lowering the temperature to 70 ° C-90 ° F. Since the temperature of the top of the reaction distillation column and the extraction rectification column is about 64 ° C, the pressure of the steam at the top of the column can be increased to 90-110 ° C by pressurization, which can be used as a column reheater. Heat source.

(3) Reduce the extractive / azeotrope molar ratio of the extractive distillation column, thereby reducing the temperature of the extractive distillation column kettle, and provide guarantee for making full use of the reaction heat of the alkylene carbonate synthesis part. The extractive distillation column reactor temperature controlled at 120 ~ 140 ° C, the use of low-pressure steam of about heat of reaction by-product from the alkylene carbonate is 140 ~ 160 ° C.

The above three technical improvements can significantly reduce the steam energy consumption and cooling circulating water volume of the process.

Catalysts for the transesterification of alkenyl carbonate and monohydric alcohols generally use sodium alkoxides, such as sodium methoxide or sodium ethoxide, which are soluble in both monohydric and dihydric alcohols. Therefore, as long as the sodium alkoxide is not converted to sodium carbonate, the catalyst can be recycled for a long period of time. use. However, in the presence of a trace amount of water-containing catalyst, the alkenyl carbonate can easily react with sodium alkoxide to become sodium carbonate which is insoluble in the reaction material, resulting in deactivation. In the present invention, after the liquid in the reaction distillation column tower kettle is first evaporated and concentrated, the concentration of the catalyst in the solution is concentrated from 1-3% (wt) to 10-50%, and after mixing with the monohydric alcohol, the concentration is reduced to 0.5-5% Insoluble impurities such as sodium carbonate are removed through a filter, and fresh catalyst is appropriately replenished to maintain the circulating catalyst concentration.

The method of the present invention, to optimize the generation and carbonic acid ester production process embankment diol, can significantly reduce energy consumption and cooling water consumption, compared with the same size device production, steam consumption can be reduced 60-90%, Reduce cooling water consumption by 40-70%. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a flow chart of the synthesis of alkenyl carbonate.

Figure 2 is a flow chart of transesterification synthesis of dialkyl carbonate and diol.

Figure 3 is a flow chart of catalyst recovery and glycol. detailed description

Referring to FIG. 1, FIG. 2 and FIG. 3, the method of the present invention includes the following steps:

(1) Synthesis of alkenyl carbonate:

Ethylene oxide (PO, abbreviated as below) or ethylene oxide (EO, abbreviated as below) and C0 ₂ react first in the first adiabatic reactor 101, and the reaction product enters the external heat exchanger 102, using the reaction heat temperature of 145 to yield the low pressure steam 160 'C, and continued for the extractive distillation tower reboiler kettle, then partially recycled into the first adiabatic The reactor 101 partially enters the reaction in the second first adiabatic reactor 103, and the ratio of the flow rate of the heat exchanger 102 to the weight flow rate entering the second reactor 103 is 5 to 30, preferably 10 to 20, and preferably 15 or so. The inlet temperature of the first reactor 101 is 140-160 ° C, the outlet temperature is 175-190 ° C, and the temperature of entering the second reactor is 130-145 V, preferably 135-140 ° C. ₀

Other reaction conditions are:

The pressure of the first reactor is P = 2 ~ 8Mpa, generally 3 ~ 6Mpa, preferably 4 ~ 4.5Mpa.

The raw material ratio C0 ₂ / PO or EO = 1.01—1.1, and generally 1.03—1.05 (molar ratio).

The catalyst is tetraethylammonium bromide / PO or EO = 0.01 ~ 1.0%, generally 0.1% ~ 0.5% (molar ratio).

After the reaction system, the total conversion of PO or EO is greater than 99%, and even greater than 99.5%.

The alkene carbonate product from the second reactor 103 contains unconverted. And PO or EO _02, and a catalyst tetraethylammonium bromide, referred to as crude enester. The crude ene ester enters the decompression flash tank 104. The pressure of the flash tank 104 is 70 ~ 120kPa, the temperature is 130 ~ 180 ° C, preferably between 160 ~ 170 ° C, the excess CO ₂ and PO are removed, and then enter negative purifying column 105, overhead alkylene carbonate ester, carbonate and catalyst bottoms enester (allyl carbonate ester herein as a solvent to dissolve the catalyst), recycled into the first reactor 101. Because the by-products of the polymer may be generated, which affects the catalyst's activity to some extent, it is also possible to periodically lead out a small part to remove the polymer, that is, catalyst regeneration.

Negative pressure purifying column 105 is l ~ 15kPa, usually 5 ~ 10kPa. Enester carbonate ester return flow and the amount of allyl carbonate recovery ratio control between 0.1~0.5 (molar ratio), is generally between 0.2 and 0.3. The temperature difference between the top of the negative pressure refining tower 105 and the tower kettle is not much, generally between 1 ~ 10 ° C, the temperature of the tower kettle is between 140 ~ 180 ° C, and generally between 15 (60 ° C, Between 150 ~ 160 ° C.

The product of the negative pressure refining tower 105 enters the heat exchanger at the top of the tower and produces low-pressure steam as a by-product. The low-pressure steam in this part can be directly used for the primary evaporation of the liquid in the reactor distillation column. Thus, the steam heat allyl carbonate carbonate purifying column top (allyl carbonate ester may be viewed as a catalyst recovery heat consumption) may be used for the dialkyl carbonate catalyst recovery.

In this way, the reaction heat of the reactor of the alkylene carbonate synthesis section and the secondary steam of the purification column can be effectively used in the dialkyl carbonate synthesis section.

In addition, the catalyst for the synthesis of alkenyl carbonate mainly uses tetraethylammonium bromide, which is directly synthesized from triethylammonium and ethyl bromide in an alkenyl carbonate solution. The concentration is 10-20% (wt), and the temperature is 60-120 °. C.

(2) dialkyl carbonate (referred to as DAC, the same below) and the diol was prepared:

The alkenyl carbonate first enters the extractive distillation column 202 as an extractant, and separates the monoalcohol and DAC azeotrope from the reaction rectification column 201, and the monoalcohol is extracted from the top of the extractive rectification column 202, and partly passes through the compressor 204 Heated compressed boosted reactive distillation column 201 as a bottoms reboiler heat source, and then condensed to reflux the rear portion of the monohydric alcohol warmed pressurized by the compressor 204 is recycled into the reactive distillation column 201 as a reaction starting material, the reactive distillation column The top of 201 is partially condensed, and the condensate is used as reflux liquid. Uncondensed steam enters extractive distillation column 202; the extractive distillation column 202 is a crude DAC in the distillation column and enters the diester column 203. The kettle is an alkene carbonate. The material extracted from the tower kettle is divided into two strands, one of which is recycled to the extractive distillation column 202, and the other is used as the raw material of the reactive distillation column 201. The molar ratio of the material entering the extraction rectification column 202 and the material entering the reaction rectification column 201 is 2-8; the main feature of this step is that the azeotrope entering the extraction rectification column 202 from the reaction rectification column 201 is steam The reflux at the top of the extractive distillation column 202 is first used as a heat source for the reboiler of the reaction distillation column 201 in the form of steam after being compressed and pressurized to heat up, and then refluxed after condensation; the product monoalcohol is extracted in the form of steam and then passed After being heated under pressure, it is circulated into the reaction distillation column 201 as the reaction raw material;

The temperature of the reaction distillation column 201 tower kettle is 70 ~ 80 ° C. The purpose is to raise the latent heat of the steam in the reflux part of the extraction distillation tower 202 to 90 ~ 100 ° C under pressure, and reboil it as the reaction distillation tower 201. Part of the heater heat source.

The top steam of the reaction distillation tower adopts partial condensation, and the uncondensed steam is used as the raw material of the downstream extraction distillation tower 202, which is steam, which can reduce the steam consumption of the reaction distillation tower 201 and the amount of cooling circulating water.

The reaction distillation column 201 uses a plate column, and the total vapor phase resistance is between 10-30 kPa, and is generally controlled between 12-16 kPa. The top operating pressure of the extractive distillation column 202 is normal pressure, which is 101-105kPa, and is generally between 101-102kPa. The extractive distillation column 202 can also use a plate column, with a total vapor phase resistance between 5-15 kPa, and generally between 8-10 kPa. In this way, the total pressurized head of the alcohol in the circulation unit is 20-25 kPa.

The main operating parameters of the reactive distillation column 201 are as follows:

Total feed monohydric alcohol and allyl carbonate ester molar ratio of 10 to 20, the best molar ratio of 10 to 13.

The circulation amount of the catalyst is converted into 100% of sodium ions, and the content in the liquid phase in the reaction refinement tower 201 is 0.05 to 0.5% (wt).

The recycled catalyst is preferably mixed with all the fresh monohydric alcohols, rather than the recycled unit alcohols, into the reaction refinery 201, and the molar ratio of the amount of the fresh monohydric alcohol to the difluorenyl carbonate is 2-4.

The reflux ratio of the reaction distillation column 201 is 0.2 to 0.6.

The reaction fractionator 201 bottoms temperature of 60~150 ° C, preferably a temperature of 70 ~ 90 ° C.

Reactive distillation column 201 operating pressure of column top 70 ~ 120kPa, generally between 101 ~ 105kPa.

In the reaction rectification column 201, the liquid phase flows through each tray, especially the trays where the reaction and distillation coexist. The average residence time of the liquid is controlled between 0.1-20 minutes, and generally between 1 and 5 minutes. Fortunately, 2-3 minutes. The residence time is controlled to ensure sufficient reaction residence time for the transesterification reaction of the synthesis of difluorenyl carbonate. At the same time, the reaction speed of side reactions must also be limited. The side reaction is mainly an etherification reaction between a diol and a monohydric alcohol. In the reaction distillation 201 column, the alkenyl carbonate can be completely converted. Dialkyl carbonate and monoalcohol of azeotrope are obtained at the top of the column;

For extractive distillation column 202 and column 203 diesters, the main operating parameters are as follows:

The higher purity alkenyl carbonate from the synthetic part of alkenyl carbonate has a purity of more than 99.9%.

Extractant and feed molar ratio of the azeotrope is 0.2 to 1.0, preferably between 0.3-0.5, the rectification column can be maintained between the extraction column bottom temperature 110 ~ 160 ° C, to facilitate the synthesis reaction using allyl carbonate ester Low pressure steam produced by the generator.

After extractive distillation column 201 overhead recovery monohydric alcohol recycled to the reactive distillation column 201 pressure, head pressure of 20

30kPa, the methanol refluxed at the top of the extractive distillation column 202 is heated to 90 ~ 100 ° C under pressure and the pressure is 200 ~ 300kPa, as the heat source of the reboiler of the 201 column of the reactive distillation column;

The extractive distillation column 202 is operated at normal pressure, and the diester column 203 is operated at negative pressure. The pressure at the top of the column is between 3 and 30 kPa, generally between 5 and 10 kPa. The temperature of the column kettle is 110 to 160 ° C.

(3) catalyst recovery and glycol refining:

The glycol liquid product stream from the reaction distillation column 201 tower kettle contains the monohydric alcohol, the glycol and the catalyst, and also contains a small amount of ether, and enters the evaporation flash tank 301. The feed liquid of the evaporation flash tank 301 is a concentrated catalyst solution, wherein the concentration of the catalyst in terms of sodium 5 ~ 30% (wt), is fed through the heater 301 of the loop circulation pump 302, to return to the evaporator flash tank 301, another portion 303 can be formulated into the circulating catalyst. Bian monohydric alcohol starting material with a reactive rectification column is required in the formulation as a diluent tank 303, the formulated catalyst concentration between 0.2 ~ 2% (wt). Formulated catalyst circulation through the filter 304 to remove the undissolved solids circulation into the reaction distillation column 201 which, in the unit and add fresh catalyst to maintain the concentration of sodium alkoxide catalyst.

The use of such arrangements and evaporation forms is particularly suitable for the process to which the invention relates. Since the sodium containing metal alkoxide in the feed solution is evaporated, the undissolved even contain sodium carbonate, the form may be prevented or mitigate fouling the heating tube wall due to the salting out effect.

Diol and monoalcohol steam boiler 301 enters the top of the flash tank diol product column 305 in the column bottoms product diol 305 to obtain a high purity diol product, the line may be extracted at a side near the tower bottom, Can prevent the product from appearing color.

The glycol product column 305 is partially condensed at the top, and the output is monoalcohol vapor, which also contains the dihydric alcohol and ether and enters the monoalcohol recovery tower 306. In the monoalcohol recovery tower 306, the purity of the top of the tower is very high. High monohydric alcohols, tower kettles give ethers and glycols.

The output of the mono-alcohol recovery tower 306 tower kettle enters the ether refining tower 307. A highly pure ether was obtained.

Flash evaporator 301 is disposed above the filling cycle of the heater 302 at a distance of 0.1 ~ 10m.

The main operating parameters are as follows:

Pressure of the evaporator 301 is 5 ~ 30kPa, the temperature is 120 ~ 140 ° C;

The overhead pressure of the glycol product column 305 is between 5-30 kPa, and generally between 15-20 kPa. The temperature of the tower kettle is controlled between 130-150 ° C, preferably between 135-140 ° C, to prevent the condensation side reactions of the glycol as much as possible.

The pressure at the top of the monohydric alcohol recovery tower 306 is 5 to 30 kPa. However, in order for the steam at the top of the monohydric alcohol product tower 305 to flow directly to the monohydric alcohol recovery tower 306, the pressure at the top of the monohydric alcohol recovery tower 306 should be higher than that of the dihydric alcohol. The pressure at the top of the product column 305 is 1-3 kPa lower, and the tower kettle of the monoalcohol recovery column 306 is 50-65 ° C.

The ether refining tower 307 generally adopts batch refining, and the operating pressure at the top of the tower is 5-30 kPa. First, take out the low boiling point monohydric alcohol (usually containing a small amount of monohydric alcohol), and then take out the ether. The glycol product column 305 recovers the glycol.

According to a preferred solution of the present invention, the heat released by the reactor 101 and the heat of the top steam of the negative pressure refining tower 105 are used to extract the bottom reboiler of the rectification tower 202 and the evaporation heat exchanger 302 for catalyst recovery as heating. Heat source.

Example 1

Take a unit that produces 60,000 tons of dimethyl carbonate and 50,000 tons of propylene glycol each year as an example:

Raw materials: PO = 87.5kmol / h, C0 ₂ = 91.85kmol / h, methanol = 178.5kmol / h.

The operating conditions of the alkenyl carbonate part are:

PO overall conversion of alkylene carbonate ester moiety 99.64%, PC 99.5% yield.

(1) the amount of catalyst cycle (100% calculated Huan tetraethylammonium) is 0.18km _O l / _h;

(2) The inlet temperature of the first reactor R101 is 153 ° C, the pressure is 4.2MPa, the outlet temperature is 178 ° C, the circulation ratio is 15.7, and the heat of the by-product steam is 8.6X 10¾J / h _;

(3) the inlet temperature of the second reactor is 137 ° C;

Pressure (4) is atmospheric flash tank 110 kPa, a temperature of 155 ° _C;

(5) The top pressure of the refining tower T101 is 10kPa, the top temperature is 164 ° F, the reflux ratio is 0.3, the tower temperature is 167, and the heat required by the tower is 5.8 X 10¾J / h, which is provided by external steam. The heat is 6.1 X 10¾J / h.

The main operating conditions for the co-production part of dialkyl carbonate and diol are: (1) Total methanol / PC of reactive distillation column = 11.8;

(2) The reflux ratio is 0.4;

(3) The temperature of the tower kettle is 75 ° C _;

(4) the total number of plate 45, a catalyst, a mixture of fresh methanol feed and PC from the top, the first plate 5, by the extractive distillation column looped back plate of the methanol vapor feed direction of the tower reactor by 10 pieces

(5) Under normal operation, the reaction does not require additional rectifying column reboiler steam as a heat source, which heat provided solely by the extractive distillation column overhead of methanol vapor;

(6) A mixture of methanol and DMC is obtained at the top of the column, the methanol content is 71% (wt), the DMC is 29% (wt), and the total flow rate is 27.02 tons / h _;

(7) A mixture of methanol, propylene glycol, propylene glycol monomethyl ether and catalyst is obtained in the tower kettle, and the flow rate of each component is: methanol = 8080 kg / h, propylene glycol = 6551.2 kg / h, propylene glycol monomethyl ether = 77.625 kg / h, sodium methoxide catalyst = 100kg / _h;

(8) The total PC / azeotrope molar ratio of the extractive distillation column is 0.5;

(9) of the extractive distillation column bottoms temperature is 138Ό;

(10) recycled to the fractionator overhead methanol reaction the compressor shaft power of 56kW, the circulation amount of 19.2 t / _h;

(11) The reflux steam at the top of the column is compressed to 200 kPa, the temperature is 105.8 ° C, the shaft power required by the compressor is 78.5 kW, and the amount of compressed methanol is 9.6 tons / h, which is equivalent to the reflux ratio of the extractive distillation column of 0.5;

(12) The boiler reboiler of the extractive distillation column requires heat of 8.4X 10¾J7h, and the temperature of the by-product steam from the alkylene carbonate synthesis reactor is 150 ° C, and the heat is 8.6X 10¾J / h. All are obtained here use;

(13) The operating pressure at the top of the diester column (that is, the extractant recovery column) is 10 kPa, the reflux ratio is 1.0, the temperature of the tower kettle is 161 Ό, and the heat required by the tower kettle is 5.9X 10¾J / h, which is provided by external steam. ;

(14) The diester tower kettle obtained 99.8% (wt) dimethyl carbonate with a mass flow rate of 7851 kg /, which is equivalent to an annual dimethyl carbonate production of 62810 tons / h.

The main operating conditions of catalyst recovery and PG refining section-

(1) The operating pressure of the evaporator is 15kPa, the temperature is 132 ° C, the required heat is 12.2X 10¾J h, the heat of steam produced by-product from the top of the tower is 5.75 X 10¾J / h, and the remaining heat is 6.45 X 10¾J / h by external steam;

(2) The operating pressure of the PG refining tower is 14kPa, the temperature of the tower kettle is 135 Ό, the required heat is 2.8 X 10 ⁶ kJ / h, and it is provided by externally supplied steam. The tower kettle obtains propylene glycol with a purity of 99.9% (wt). The mass flow rate is 6538kg / h, which is equivalent to an annual propylene glycol production of 52305 tons / h; (3) the operating pressure of the methanol recovery column overhead is 12kPa, tower bottom temperature of 65. C, the amount of heat required is 2.5 X 10 ⁶ kJ / h, which is provided by externally supplied steam, and the purity of 99.5% (wt) methanol is obtained from the top of the tower, and the mass flow rate is 8080 kg / h _;

(4) an ether of batch distillation column, available 77kg / h from the top of propylene glycol monomethyl ether, having a purity of 99.5% (wt). Therefore, the total heat required by the externally supplied steam is:

5.75 + 5.94 + 6.45 + 2.8 + 2.5 = 23.44X 10 ⁶ kJ / h,

Equivalent to 11.2 tons of steam / h.

As the total output per hour is 7851 +6538 = 14389kg / h, the steam demand per ton of product is: 11.2 / 14.389 = 0.7785 tons, which is less than 1 ton / h.

Claims

Claim

What is claimed is: 1. A method for co-producing difluorenyl carbonate and a diol, comprising the synthesis of an alkenyl carbonate, the preparation of a difluorenyl carbonate and a diol, and a catalyst recovery, characterized in that the synthesis of the alkenyl carbonate includes glycidoxy purified embankment embankment or ethylene carbonate and the reaction with alkylene carbonate co _2, glycidoxy or embankment ₂ is first reacted with ethylene oxide in co first adiabatic reactor (101), the reaction product into the external a heat exchanger (102), a low pressure steam byproduct, the resulting reaction enester carbonate purifying column into the negative pressure (105), the molar ratio of overhead reflux flow allyl carbonate ester and preclude the allyl carbonate ester is an amount of 0.1 to 0.5, The temperature difference between the top of the negative pressure refining tower (105) and the tower kettle is 1 ~ 10 ° C. The product of the top of the negative pressure refining tower (105) enters the top heat exchanger, and the low-pressure steam is by-produced.

2. The method according to claim 1, characterized in that the preparation of the dialkyl carbonate and the diol includes a reaction distillation of a monohydric alcohol and an alkenyl carbonate, and an extraction essence using the alkenyl carbonate as an extractant. ;

The monohydric alcohol is extracted from the top of the extractive distillation column (202), and part of it is used as a heat source for the reboiler of the reaction distillation column (201) after being heated by compression and pressure, and then refluxed after being condensed. Recycle into the reaction rectification column (201) as the reaction raw material, the top of the reaction rectification column (201) is partially condensed, the condensate is used as the reflux liquid, and the uncondensed steam enters the extraction rectification column (202);

The molar ratio of the material of the monohydric alcohol vapor entering the extractive distillation column (202) to the material entering the reactive distillation column (201) is 0.5-2.0.

3. The method according to claim 2, characterized in that the extractive distillation column 201 overhead recovery unit boosting an amplitude of 20-30 kPa alcohol, extractive distillation column (202) overhead reflux in methanol was added The temperature is raised to 90 ~ 100 ° C, and the pressure is 200 ~ 300kPa.

The method according to claim 2, characterized in that the reflux ratio of the reaction distillation column (201) is 0.2 to 0.6.

The method according to claim 2, characterized in that the total feed molar ratio of the monohydric alcohol to the alkenyl carbonate of the reaction distillation column (201) is 10-20.

The method according to claim 5, characterized in that the total feed molar ratio of the monohydric alcohol to the alkenyl carbonate of the reactive distillation column (201) is 10-13.

The method according to claim 4, characterized in that the temperature of the reaction distillation column (201) is 60 150

° C.

8. The method according to claim 4, characterized in that the reactive distillation column (201) bottoms temperature of from 70 to 90 . C.

9. The method according to claim 2, wherein the molar ratio of the feed of the extractant to the azeotrope is 0.2 to 0.85.

The method according to claim 2, characterized in that the temperature of the column kettle of the extractive distillation column (202) is 110-160. C.

The method according to claim 2, characterized in that the operating pressure at the top of the extractant recovery tower (203) is 3 to 30 kPa, and the temperature of the tower kettle is 110 to 160 ° C.

The method according to claim 2, characterized in that the catalyst recovery and the purification of the glycol include the following steps: a liquid product comprising a glycol, a monohydric alcohol and a catalyst from a reaction distillation column (201) tower kettle; The stream enters the evaporation flash tank (301), and is sent to the circulation heater (302) by the circulation pump (301), and then returns to the evaporation flash tank (301), and the other part enters the circulation catalyst preparation tank (303). After mixing with fresh monohydric alcohol, it enters the reaction refinery tower (201).

The product glycol is directly extracted from the tower kettle or the lower side line of the glycol refining tower (305), and the product at the top of the tower 305 is extracted as steam and directly enters the monohydric alcohol recovery tower.

The method according to claim 2, characterized in that the evaporative flash irrigation (301) is arranged above the circulation heater (302) at a distance of 0.1 to 10 m.

14. The method according to any one of claims 1 to 13, characterized in that the heat released from the reactor (101) and the heat of the overhead steam of the negative pressure refining tower (105) are used for the extraction distillation column ( The bottom reboiler of 202) and the evaporative heat exchanger (302) for catalyst recovery serve as heat sources for heating.