阅读说明：本技术 一种甲缩醛合成聚甲氧基二甲醚的系统及方法 (System and method for synthesizing polymethoxy dimethyl ether from methylal ) 是由 陈华 刘红喜 郁刘军 卢建华 李桂成 董云海 于 2020-04-27 设计创作，主要内容包括：本发明公开了一种甲缩醛合成聚甲氧基二甲醚的系统,包括依次连接的甲醛合成单元、甲醛吸收单元、醚化反应单元和精制分离单元甲醛合成单元包括脱氢反应器,以及与所述脱氢反应器连接的熔盐循环单元、甲缩醛预处理单元和产物冷却单元。本发明提供的一种甲缩醛合成聚甲氧基二甲醚的系统及方法,能够解决有效解决聚甲氧基二甲醚工业合成过程的问题,作为新型环保型柴油含氧组分,可加快低迷的煤化工行业迅速转型缓解产能过剩,弥补替代柴油的新能源行业技术空白短板,促进煤化工、石油化工向高效节能绿色化学发展。(The invention discloses a system for synthesizing polymethoxy dimethyl ether from methylal, which comprises a formaldehyde synthesis unit, a formaldehyde absorption unit, an etherification unit and a refining separation unit which are sequentially connected, wherein the formaldehyde synthesis unit comprises a dehydrogenation reactor, and a molten salt circulation unit, a methylal pretreatment unit and a product cooling unit which are connected with the dehydrogenation reactor. The system and the method for synthesizing the polymethoxy dimethyl ether by the methylal can solve the problem of the industrial synthesis process of the polymethoxy dimethyl ether, can be used as a novel environment-friendly oxygen-containing component of diesel oil, can accelerate the rapid transformation of the low-density coal chemical industry, relieve the excess of the capacity, make up the technical blank short board of the new energy industry for replacing the diesel oil, and promote the development of the coal chemical industry and the petrochemical industry to high-efficiency energy-saving green chemistry.)

1. A system for synthesizing polymethoxy dimethyl ether by methylal is characterized by comprising a formaldehyde synthesis unit, a formaldehyde absorption unit, an etherification reaction unit and a refining separation unit which are connected in sequence;

the formaldehyde synthesis unit comprises a tubular fixed bed reactor, and a heat conduction oil circulation unit, a methylal pretreatment unit and a product cooling unit which are connected with the tubular fixed bed reactor, wherein the methylal pretreatment unit and the product cooling unit exchange heat.

2. The system for synthesizing polymethoxy dimethyl ether from methylal according to claim 1, wherein the heat transfer oil circulation unit comprises a heat transfer oil storage tank, a heat transfer oil circulation pump, a heat transfer oil heater, a reactor heat transfer oil storage tank, a heat transfer oil condenser and a first steam generator;

the heat conduction oil storage tank is connected with the heat conduction oil heater through a heat conduction oil circulating pump;

the heat conducting oil heater is connected with the tubular fixed bed reactor;

the tubular fixed bed reactor is circularly connected with the reactor heat conducting oil storage tank;

the heat conducting oil storage tank of the reactor is connected with the heat conducting oil storage tank and is circularly connected with the heat conducting oil condenser;

the heat conducting oil condenser is circularly connected with the first steam generator, hot water is input into the first steam generator, and generated steam is input into the steam pipe network.

3. The system for synthesizing polymethoxy dimethyl ether from methylal according to claim 2, wherein the methylal pretreatment unit comprises a methylal evaporator, a mixer, a combined fan and a mixture preheater; methylal is introduced into the methylal evaporator, the methylal evaporator is connected with the steam pipe network to input steam, and the downstream of the methylal evaporator is connected with the mixer; the upstream of the mixer is respectively communicated with the outside and the circulating gas through the combined fan, and the downstream of the mixer is connected with the tubular fixed bed reactor through the mixture preheater; the mixture preheater is connected with the product cooling unit for heat exchange.

4. The system for synthesizing polymethoxy dimethyl ether from methylal according to claim 3, wherein the product cooling unit comprises a mixed product cooler and a second steam generator, the mixed product cooler is connected with the tubular fixed bed reactor at the upstream and connected with the formaldehyde absorption unit through the mixture preheater at the downstream, and is also connected with the second steam generator in a circulating manner, hot water is input into the second steam generator, and the generated steam is input into a steam pipe network.

5. The system for synthesizing polymethoxy dimethyl ether from methylal according to claim 4, wherein the formaldehyde absorption unit comprises a first absorption tower and a second absorption tower;

the tower kettle of the first absorption tower is connected with the mixture preheater, the tower bottom of the first absorption tower is connected with the etherification reaction unit, and the tower top of the first absorption tower is connected with the second absorption tower;

the tower kettle of the second absorption tower is connected with the tower top of the first absorption tower, the tower body is connected with the combined fan, the tower bottom is connected with a water formaldehyde methylal removing device, and the tower top is connected with an incinerator;

the device comprises a first absorption tower, a second absorption tower, a circulating pump, a formaldehyde heat exchanger, a liquid distributor, a liquid collecting disc and a plurality of filter layers, wherein the first absorption tower and the second absorption tower are internally provided with the plurality of layers of sieve plates and the plurality of layers of filter layers in sequence from top to bottom, the top of each layer of the filter layer is provided with the liquid distributor, the bottom of each layer of the filter layer is provided with the liquid collecting disc, and the liquid.

6. The system for synthesizing polymethoxy dimethyl ether from methylal according to claim 5, wherein the etherification reaction comprises a cluster reactor, a cluster reaction heat exchanger, a fine reaction regulation flowmeter, a forced circulation flowmeter and a forced circulation pump, wherein the upstream of the cluster reactor is connected with the bottom of the first absorption tower, the downstream of the cluster reactor is connected with the refining separation unit, the bottom of the cluster reactor is respectively connected with the fine reaction regulation flowmeter and the forced circulation flowmeter through the forced circulation pump, the fine reaction regulation flowmeter is connected with the top of the cluster reactor, and the forced circulation flowmeter is connected with the top of the cluster reactor through the cluster reaction heat exchanger.

7. The system for synthesizing polymethoxy dimethyl ether from methylal according to claim 6, wherein the refining and separating unit comprises a first refining tower, a second refining tower and a third refining tower; the upstream of the first refining tower is connected with the bundling reactor, a methylal outlet is arranged at the top of the tower, the bottom of the tower is connected with the second refining tower, and a neutralization dehydrating agent is input into the first refining tower; the top of the second refining tower is provided with a PODE2 outlet, and the bottom of the second refining tower is connected with the third refining tower; the third refining tower is provided with a PODE3 outlet at the top, a PODE4 outlet, a PODE5 outlet and a PODE6 outlet from top to bottom, and PODE7-8 outlets at the bottom.

8. The method for synthesizing polymethoxy dimethyl ether by methylal is characterized by adopting the system as claimed in any one of claims 1 to 7, and specifically comprises the following steps:

(1) introducing nitrogen into the formaldehyde synthesis unit to reduce the oxygen concentration, vaporizing methylal through the methylal pretreatment unit, mixing the vaporized methylal with circulating gas and air to obtain mixed gas, introducing the mixed gas into the tubular fixed bed reactor, and controlling the synthesis reaction temperature through the heat conduction oil circulation unit to enable the methylal to react under the action of a catalyst to generate formaldehyde; the obtained reaction product is sequentially cooled by a mixed product cooler and a second steam generator; introducing the cooled reaction gas into a first absorption tower, absorbing the reaction gas by absorption liquid, introducing a mixed solution of formaldehyde and methylal into a cluster reactor, introducing the residual gas into a second absorption tower, absorbing the residual gas by refined water to obtain a formaldehyde aqueous solution, and introducing the tail gas after washing into an incinerator for combustion;

(2) controlling the formaldehyde and the methylal to react in the cluster reactor, and refining and separating the products sequentially through a first refining tower, a second refining tower and a third refining tower to obtain PODE2, PODE3, PODE4, PODE5, PODE6 and PODE7-8 respectively.

9. The method for synthesizing polymethoxy dimethyl ether from methylal as claimed in claim 8, wherein the oxygen concentration in step (1) is <1000 ppm; the methylal is vaporized by steam of 40-90 kpa or hot water at 70-100 ℃; the catalyst is an iron-molybdenum catalyst; the reaction temperature is controlled to be 290-360 ℃, the pressure is controlled to be 40-700 kpa, the oxygen concentration in the circulating gas is controlled to be 6-9.6%, and the methylal concentration in the mixed gas is controlled to be 3-9%; the absorption liquid is methanol or methylal, the temperature of the top of the first absorption tower is 20-40 ℃, the temperature of the bottom of the first absorption tower is 60-90 ℃, and the tower pressure is 30-800 kPa; the temperature of the top of the second absorption tower is 20-30 ℃, the temperature of the bottom of the second absorption tower is 60-90 ℃, and the pressure of the second absorption tower is 30-70 kPa.

10. The method for synthesizing polymethoxy dimethyl ether from methylal according to claim 9, wherein the molar ratio of formaldehyde to methylal in step (2) is 1.3: 1-1.1: 1, the reaction temperature is 50-110 ℃, and the reaction pressure is 0.5-3 MPa; a neutralization dehydrating agent is input into the first refining tower, the tower top pressure of the first refining tower and the second refining tower is 3 kPa-30 kPa, and the tower top pressure of the third refining tower is-10 kPa-100 kPa; the top temperature of the first refining tower is controlled to be 41-45 ℃, the bottom temperature of the first refining tower is controlled to be 129-149 ℃, the top temperature of the second refining tower is controlled to be 97-109 ℃, the bottom temperature of the second refining tower is controlled to be 170-190 ℃, the top temperature of the third refining tower is controlled to be 79-99 ℃, and the bottom temperature of the third refining tower is controlled to be 240-260 ℃; the reflux ratio of the first refining tower is controlled to be 0.1-2.0, the reflux ratio of the second refining tower is controlled to be 0.1-1.3, and the reflux ratio of the third refining tower is controlled to be 0.1-1.5.

Technical Field

The invention relates to the technical field of chemical synthesis of new energy, in particular to a system and a method for synthesizing polymethoxy dimethyl ether from methylal.

Background

With the economic development, the consumption of non-renewable resources is increasing day by day, namely the problem of resource exhaustion is faced, and gasoline, diesel oil and the like are derived from petroleum and belong to non-renewable resources, which are the key of the problem of resource exhaustion; in addition, the waste gas generated after the combustion of diesel oil and the like pollutes the environment, becomes a main pollution source of urban atmosphere and is not beneficial to the development of the earth ecological environment. In order to solve the current situation, researchers seek new energy sources capable of replacing non-renewable resources such as diesel oil, but emerging nuclear energy, solar energy, wind energy, water energy and the like can only be used as supplementary energy sources at present and cannot be used as main energy sources for replacing oil. Therefore, clean diesel oil still needs to be developed at the present stage, the resource utilization rate is improved, the problem of exhaustion of non-renewable resources is relieved, and the problem of atmospheric pollution is solved from the source.

The polyoxymethylene dimethyl ether (PODE) is a novel environment-friendly diesel oil oxygen-containing component which is recognized at present and can promote diesel oil to fully combust and reduce exhaust emission, the cetane number of the polyoxymethylene dimethyl ether (PODE) is more than 76, the oxygen content is 47-50%, the boiling range is 153-268 ℃, the miscibility with diesel oil is excellent, the polyoxymethylene dimethyl ether can be blended into diesel oil in any proportion, the oxygen content of the diesel oil is increased, the combustion performance of the diesel oil is improved, the pollution and emission reduction of automobile exhaust gas are more than 50%, and particularly, the SO in the exhaust gas is greatly reduced₂、NO_xCO and C_mH_nIs discharged from

The preparation process of polyoxymethylene dimethyl ether (PODE) mainly comprises a method for synthesizing trioxymethylene and methylal, a method for synthesizing paraformaldehyde and methylal and a method for synthesizing formaldehyde and methylal. The above process route has the following problems: the process route is long, and the investment cost is high; the production energy consumption is large, the cost is high, and the practical application value is not realized; the quality of the obtained product is unstable by adopting the gap type reaction; the separation process is complicated and neutralization by water removal is difficult.

Therefore, a new system and method for synthesizing polymethoxy dimethyl ether is a problem to be solved by those skilled in the art.

Disclosure of Invention

In view of the above, the invention provides a system and a method for synthesizing polymethoxy dimethyl ether from methylal, which can effectively solve the problem of the industrial synthesis process of polymethoxy dimethyl ether, and the prepared polymethoxy dimethyl ether can be used as a novel environment-friendly diesel oil oxygen-containing component, can increase the oxygen content of diesel oil, improve the combustion performance of diesel oil, accelerate the transformation of low-carbon coal chemical industry, and promote the development of coal chemical industry and petrochemical industry to high-efficiency, energy-saving and green chemistry.

In order to achieve the purpose, the invention adopts the following technical scheme:

a system for synthesizing polymethoxy dimethyl ether by methylal comprises a formaldehyde synthesis unit, a formaldehyde absorption unit, an etherification reaction unit and a refining separation unit which are connected in sequence;

the formaldehyde synthesis unit comprises a tubular fixed bed reactor, and a heat conduction oil circulation unit, a methylal pretreatment unit and a product cooling unit which are connected with the tubular fixed bed reactor, wherein the methylal pretreatment unit and the product cooling unit exchange heat.

Preferably, the heat-conducting oil circulating unit comprises a heat-conducting oil storage tank, a heat-conducting oil circulating pump, a heat-conducting oil heater, a heat-conducting oil storage tank of the reactor, a heat-conducting oil condenser and a first steam generator;

the heat conduction oil storage tank is connected with the heat conduction oil heater through a heat conduction oil circulating pump;

the heat conducting oil heater is connected with the tubular fixed bed reactor;

the tubular fixed bed reactor is circularly connected with the reactor heat conducting oil storage tank;

the heat conducting oil storage tank of the reactor is connected with the heat conducting oil storage tank and is circularly connected with the heat conducting oil condenser;

the heat conducting oil condenser is circularly connected with the first steam generator, hot water is input into the first steam generator, and generated steam is input into the steam pipe network.

The beneficial effects of the preferred technical scheme are as follows: compared with the process for synthesizing polymethoxy dimethyl ether by paraformaldehyde or trioxymethylene and methylal, the process has the advantages of short flow, less equipment refining investment, low operation and maintenance cost, low energy consumption, less heavy components in reaction products and favorable product rectification and separation.

Preferably, the methylal pretreatment unit comprises a methylal evaporator, a mixer, a combined fan and a mixture preheater; methylal is introduced into the methylal evaporator, the methylal evaporator is connected with the steam pipe network to input steam, and the downstream of the methylal evaporator is connected with the mixer; the upstream of the mixer is respectively communicated with the outside and the circulating gas through the combined fan, and the downstream of the mixer is connected with the tubular fixed bed reactor through the mixture preheater; the mixture preheater is connected with the product cooling unit for heat exchange.

The beneficial effects of the preferred technical scheme are as follows: the invention can fully utilize cold and hot energy exchange, not only meets the requirements of heating of low-temperature media, but also meets the requirements of cooling of high-temperature media, and is beneficial to reducing energy consumption.

Preferably, the combined fan comprises a circulating fan, a fresh fan and a booster fan; the upstream of the circulating fan is connected with the second absorption tower, and the downstream of the circulating fan is connected with the mixer through the booster fan; the fresh air inlet is communicated with the outside, and the air outlet is connected with the mixer through the booster fan.

The beneficial effects of the preferred technical scheme are as follows: the invention adopts three fans to be used in different links, and is more electricity-saving compared with two fans or one fan, and is more beneficial to improving the productivity.

Preferably, the air outlet pipeline of the booster fan is connected with an oxygen concentration analyzer.

Preferably, the product cooling unit comprises a mixed product cooler and a second steam generator, the upstream of the mixed product cooler is connected with the tubular fixed bed reactor, the downstream of the mixed product cooler is connected with the formaldehyde absorption unit through the mixture preheater, the mixed product cooler is circularly connected with the second steam generator, hot water is input into the second steam generator, and generated steam is input into a steam pipe network.

The beneficial effects of the preferred technical scheme are as follows: wherein booster fan gas outlet pipeline is 3 way fan mixing main pipeline, connects oxygen concentration analysis appearance on mixing main pipeline, and it is more accurate to detect oxygen concentration, beneficial safety in production. By adopting the flow connection, cold and hot energy exchange can be fully utilized, the temperature rise of a low-temperature medium is met, the temperature reduction of a high-temperature medium is also met, redundant heat can generate steam to be supplied to a device, and the energy consumption is reduced beneficially.

Preferably, the formaldehyde absorption unit comprises a first absorption tower and a second absorption tower;

the tower kettle of the first absorption tower is connected with the mixture preheater, the tower body is connected with the combined fan, the tower bottom is connected with the etherification reaction unit, and the tower top is connected with the second absorption tower;

the tower kettle of the second absorption tower is connected with the tower top of the first absorption tower, the tower bottom of the second absorption tower is connected with a water formaldehyde methylal removing device, and the tower top of the second absorption tower is connected with an incinerator;

the device comprises a first absorption tower, a second absorption tower, a circulating pump, a formaldehyde heat exchanger, a liquid distributor, a liquid collecting disc and a plurality of filter layers, wherein the first absorption tower and the second absorption tower are internally provided with the plurality of layers of sieve plates and the plurality of layers of filter layers in sequence from top to bottom, the top of each layer of the filter layer is provided with the liquid distributor, the bottom of each layer of the filter layer is provided with the liquid collecting disc, and the liquid.

Preferably, the circulating fan is connected between the sieve plate of the second absorption tower and the filler layer through a pipeline.

Wherein, the circulating gas delivered by the circulating fan comprises 3.58 percent of carbon monoxide, 0.37 percent of methanol, 1.06 percent of water, 0.39 percent of formaldehyde, 0.07 percent of methyl formate, 0.07 percent of carbon dioxide, 87.99 percent of nitrogen, 6.02 percent of oxygen and 0.45 percent of dimethyl ether by volume percentage.

The beneficial effects of the preferred technical scheme are as follows: the invention adopts two towers to respectively absorb, the first absorption tower can efficiently recover high-concentration formaldehyde, and the second absorption tower can completely recover the formaldehyde which is not absorbed by the first absorption tower by water absorption and can also recover organic components discharged by tail gas, thereby improving the product yield. The absorption tower is internally provided with the sieve plate and the filler, so that the respective advantages of the sieve plate and the filler can be fully exerted, and the optimal absorption effect is achieved.

Preferably, the sieve plate comprises 5-20 layers, and the first layer, the second layer or the third layer are provided with feed inlets.

The beneficial effects of the preferred technical scheme are as follows: the invention arranges the feed inlet at the proper position of the sieve plate, which is beneficial to the absorption effect.

Preferably, the packing layer comprises 2-9 layers, the formaldehyde heat exchanger in the first layer of the packing layer is a chilled water heat exchanger, and the formaldehyde heat exchanger in the second layer of the packing layer is a circulating water heat exchanger. The beneficial effects of the preferred technical scheme are as follows: the tower top heat exchange medium adopts the frozen water energy to improve the absorption effect, and the heat exchange media of the other heat exchangers adopt the circulating water energy to effectively prevent the generation of formaldehyde scales.

Preferably, the etherification reaction comprises a cluster reactor, a cluster reaction heat exchanger, a fine reaction regulation flowmeter, a forced circulation flowmeter and a forced circulation pump, wherein the upstream of the cluster reactor is connected with the bottom of the first absorption tower, the downstream of the cluster reactor is connected with the refining separation unit, the bottom of the cluster reactor is respectively connected with the fine reaction regulation flowmeter and the forced circulation flowmeter through the forced circulation pump, the fine reaction regulation flowmeter is connected with the top of the cluster reactor, and the forced circulation flowmeter is connected with the top of the cluster reactor through the cluster reaction heat exchanger.

It should be noted that two streams of materials are arranged at the outlet of the forced circulation pump, one stream is forced circulation flow, the other stream is fine reaction adjustment flow, the fine reaction adjustment flow is the same as the feeding flow, the forced circulation flow is fixed flow, the flow is adjusted by an adjusting valve, and the raw material ratio is adjusted by absorption liquid methylal in the first absorption tower.

The beneficial effects of the preferred technical scheme are as follows: the etherification reaction unit adopts a cluster reactor system, and can effectively solve the problems that the existing reactor has larger volume, higher input cost, large reaction bed plugging system pressure and can not realize on-line blockage removal, the reaction time and the residence time can not be accurately controlled, and the batch reaction of one kettle and one kettle can not realize continuous industrial production.

Preferably, the polishing separation unit comprises a first polishing column, a second polishing column and a third polishing column; the upstream of the first refining tower is connected with the bundling reactor, a methylal outlet is arranged at the top of the tower, the bottom of the tower is connected with the second refining tower, and a neutralization dehydrating agent is input into the first refining tower; a PODE2 (polyoxymethylene dimethyl ether with a degree of polymerization n of 2) outlet is arranged at the top of the second refining tower, and the bottom of the second refining tower is connected with the third refining tower; the third refining tower is provided with a PODE3 (poly (methoxy dimethyl ether) outlet with the polymerization degree n being 3) at the top, a PODE4 (poly (methoxy dimethyl ether) outlet with the polymerization degree n being 4), a PODE5 (poly (methoxy dimethyl ether) outlet with the polymerization degree n being 5 and a PODE6 (poly (methoxy dimethyl ether) outlet with the polymerization degree n being 6) at the body from top to bottom, and PODE7-8 (poly (methoxy dimethyl ether) outlets with the polymerization degree n being 7-8) at the bottom.

The neutralizing/dehydrating agent is a basic solution, specifically, a bicarbonate solution, sodium methoxide, a hydroxide solution, dicyclohexylcarbodiimide, dimethylamine, diethylamine or triethylamine. Because the reaction liquid is acidic liquid, the reaction liquid can not be separated by rectification under the acidic condition, and the rectification requirement is met by adding a basic group solution for neutralization.

The beneficial effects of the preferred technical scheme are as follows: the polymethoxy dimethyl ether reaction product is a complex mixture, 5 to 8 towers are needed for separation by adopting a conventional tower, the production process is optimized, and the separation purpose can be achieved by only 3 towers, so that the process is shortened, the operation is simplified, and the operation cost and the investment cost are reduced.

The invention also provides a method for synthesizing polymethoxy dimethyl ether by methylal, which adopts the system and specifically comprises the following steps:

(1) introducing nitrogen into the formaldehyde synthesis unit to reduce the oxygen concentration, vaporizing methylal through the methylal pretreatment unit, mixing the vaporized methylal with circulating gas and air to obtain mixed gas, introducing the mixed gas into the tubular fixed bed reactor, and controlling the synthesis reaction temperature through the heat conduction oil circulation unit to enable the methylal to react under the action of a catalyst to generate formaldehyde; the obtained reaction product is sequentially cooled by a mixed product cooler and a second steam generator; introducing the cooled reaction gas into a first absorption tower, absorbing the reaction gas by absorption liquid, introducing a mixed solution of formaldehyde and methylal into a cluster reactor, introducing the residual gas into a second absorption tower, absorbing the residual gas by refined water to obtain a formaldehyde aqueous solution, and introducing the tail gas after washing into an incinerator for combustion;

(2) controlling the formaldehyde and the methylal to react in the cluster reactor, and refining and separating the products sequentially through a first refining tower, a second refining tower and a third refining tower to obtain PODE2, PODE3, PODE4, PODE5, PODE6 and PODE7-8 respectively.

The beneficial effects of the preferred technical scheme are as follows: the invention can effectively solve the problems of larger reaction system volume, long process flow and higher input cost, and has the advantages of reasonable device design, simple and convenient operation, high safety, higher reproducibility and stability and small amplification risk of the device.

Preferably, the oxygen concentration in step (1) is <1000 ppm; the methylal is vaporized by steam of 40-90 kpa or hot water at 70-100 ℃; the catalyst is an iron-molybdenum catalyst; the reaction temperature is controlled to be 290-360 ℃, the pressure is controlled to be 40-700 kpa, the oxygen concentration in the circulating gas is controlled to be 6-9.6%, and the methylal concentration in the mixed gas is controlled to be 3-9%; the absorption liquid is methanol or methylal, the temperature of the top of the first absorption tower is 20-40 ℃, the temperature of the bottom of the first absorption tower is 60-90 ℃, and the tower pressure is 30-800 kPa; the temperature of the top of the second absorption tower is 20-30 ℃, the temperature of the bottom of the second absorption tower is 60-90 ℃, and the pressure of the second absorption tower is 30-70 kPa.

Preferably, the iron-molybdenum catalyst comprises Fe, Cr and MOO₃The multi-component powdery compound is in a simple shape.

The beneficial effects of the preferred technical scheme are as follows: the invention can accurately control the production in a safe interval and deviate from an explosion range under the control of the optimal concentration, and is more beneficial to safe production. The formaldehyde scale can be effectively inhibited under the optimal temperature and pressure, the maximum conversion rate of the methylal can be ensured, and the yield of the formaldehyde can be ensured.

Preferably, the molar ratio of the formaldehyde to the methylal in the step (2) is 1.3: 1-1.1: 1, the reaction temperature is 50-110 ℃, and the reaction pressure is 0.5-3 MPa; a neutralization dehydrating agent is input into the first refining tower, the tower top pressure of the first refining tower and the second refining tower is 3 kPa-30 kPa, and the tower top pressure of the third refining tower is-10 kPa-100 kPa; the top temperature of the first refining tower is controlled to be 41-45 ℃, the bottom temperature of the first refining tower is controlled to be 129-149 ℃, the top temperature of the second refining tower is controlled to be 97-109 ℃, the bottom temperature of the second refining tower is controlled to be 170-190 ℃, the top temperature of the third refining tower is controlled to be 79-99 ℃, and the bottom temperature of the third refining tower is controlled to be 240-260 ℃; the reflux ratio of the first refining tower is controlled to be 0.1-2.0, the reflux ratio of the second refining tower is controlled to be 0.1-1.3, and the reflux ratio of the third refining tower is controlled to be 0.1-1.5.

Further preferably, the neutralization and dehydration agent is a base solution, and the base solution comprises bicarbonate solution, sodium methoxide, hydroxide solution, dicyclohexylcarbodiimide, dimethylamine, diethylamine or triethylamine. Because the reaction liquid is acidic liquid, the reaction liquid can not be separated by rectification under the acidic condition, and the rectification requirement is met by adding a basic group solution for neutralization.

The beneficial effects of the preferred technical scheme are as follows: the invention can effectively synthesize the product polymethoxy dimethyl ether and separate the product under the control of the optimized molar ratio, temperature, pressure and reflux ratio, and can improve the yield of the product polymethoxy dimethyl ether to the maximum extent.

According to the technical scheme, compared with the prior art, the invention discloses and provides a system and a method for synthesizing polymethoxy dimethyl ether by methylal, and the system and the method have the following beneficial effects:

(1) the system for synthesizing polymethoxy dimethyl ether by methylal disclosed by the invention has the advantages of simple structure, short production process flow and low investment;

(2) the synthetic polymethyl dimethyl ether has high synthetic conversion rate and yield, simple product separation and low production cost;

(3) the problem of the industrial synthesis process of polymethoxy dimethyl ether can be solved effectively, and as a novel environment-friendly diesel oil oxygen-containing component, the rapid transformation of the low-rank coal chemical industry can be accelerated, the excess of the productivity can be relieved, the technical blank short board of the new energy industry for replacing diesel oil is made up, and the development of the coal chemical industry and the petrochemical industry to high-efficiency energy-saving green chemistry is promoted.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a schematic flow chart of a system for synthesizing polymethoxy dimethyl ether from methylal according to embodiment 1 of the present invention;

FIG. 2 is a schematic flow diagram of a formaldehyde synthesis unit and a formaldehyde absorption unit provided in example 1 of the present invention;

FIG. 3 is a schematic flow diagram of an etherification reaction unit and a purification separation unit provided in example 1 of the present invention.

In the figure: 101 is a tubular fixed bed reactor; 102 is a methylal evaporator; 103 is a mixer; 104 is a fresh air blower; 105 is a circulating fan; 106 is a booster fan; 107 is an oxygen concentration analyzer; 108 is a heat conducting oil heater; 109 is a heat conducting oil circulating pump; 110 is a heat conducting oil storage tank; 111 is a reactor heat conducting oil storage tank; 112 is a heat conducting oil condenser; 113 is a first steam generator; 114 is a mixed product cooler; 115 is a second steam generator; 116 is a mixture preheater; 117 is a first absorption column; 118 is a second absorption column; 119 is a first absorption tower chilled water heat exchanger; 120 is a chilled water heat exchanger of a second absorption tower; 121 is a circulating pump; 122 is a first absorption tower circulating water heat exchanger; 123 is a second absorption tower circulating water heat exchanger; 201 is a cluster reactor; 202 is a heat exchanger; 203 is a fine reaction regulating flowmeter; 204 is a forced circulation flowmeter; 205 is a forced circulation pump; 206 is a dehydration neutralization tower; 207 is a first refining column; 208 is a second refining column; 209 is a third finishing column.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.