CN107286001B - Method for separating polymethoxy dimethyl ether - Google Patents
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- CN107286001B CN107286001B CN201610223605.6A CN201610223605A CN107286001B CN 107286001 B CN107286001 B CN 107286001B CN 201610223605 A CN201610223605 A CN 201610223605A CN 107286001 B CN107286001 B CN 107286001B
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Abstract
The invention relates to a polymethoxy dimethyl ether separation method, mainly solve the problem that water and methanol can not be removed at the same time in crude PODE2 supplies in the prior art, the invention separates in the system including PODE crude knockout tower (A), PODE2 knockout tower (B), PODE product tower (C), DMM high-pressure knockout tower (D), low-pressure methanol tower (E), recycle PODE2 high-pressure utilization tower (F), low-pressure dehydration tower (G) through adopting raw materials (1) to be refined containing DMM, PODE2, PODE3-8, water and methanol; the operating pressure of the DMM high pressure separation column (D) is higher than the operating pressure of the low pressure methanol column (E); the operation pressure of the high-pressure utilization tower (F) of the circulating PODE2 is higher than that of the low-pressure dehydration tower (G), and the circulating PODE2 can be used for separating the polymethoxy dimethyl ether.
Description
Technical Field
The invention relates to a method for separating and refining polymethoxy dimethyl ether and a method for recycling an unreacted product DMM and a byproduct PODE 2.
Background
Polyoxymethylene dimethyl ether (PODE) is a generic term for a class of substances, whose brief formula can be represented as CH3O(CH2O)nCH3. PODE has high oxygen content (42-51% is different) and cetane number (more than 30), can improve the combustion condition of diesel oil in an engine, improve the thermal efficiency, and simultaneously reduce the emission of solid pollutants, COx and NOx. It is reported that 5-30% of CH is added3OCH2OCH3Can reduce NOx emission by 7-10% and PM by 5-35%. Thus, PODE is considered to be a novel methanol derivative with great application prospect and can be used for diesel oil blending.
PODE can be synthesized from methanol and formaldehyde by acid-catalyzed dehydration. The industrial synthesis of synthesis gas from coal gasification, methanol from synthesis gas and formaldehyde from methanol oxidation are all relatively mature routes. The addition amount of PODE in diesel oil can be very high (up to 30%), and the addition of PODE can not only replace part of diesel oil, but also improve the combustion efficiency and emission performance of diesel oil. In 2006, the diesel consumption of China is 1.16 million tons, and if 30% of diesel is replaced by PODE, the import dependence of China's petroleum can be reduced by 3400 ten thousand tons, which is a very considerable number. Therefore, the research on the synthesis of PODE has great significance for relieving the environmental protection pressure of China, developing and utilizing coal resources and further on national energy safety.
Under the situation that petroleum resources are increasingly scarce, compared with the routes of preparing olefin from coal through methanol, preparing ethylene glycol from coal through synthesis gas and the like, the synthesis of coal-based PODE is a novel coal chemical industry route with great application potential. Domestic related PODEnThe research on the synthesis technology of (2) has been gradually carried out in recent years, and the research on PODE (PODE-based pod) by the national institute of chemistry and physics, Shanghai institute of petrochemical engineering, Shanxi institute of coal chemical engineering, and the university of eastern ChinanThe synthesis of (2) was studied in the related art and a few patents were filed. From the reports of published documents, the reaction route has started to be concerned by academia, but related basic or application researches are few, and the problems of low catalyst activity, difficult regeneration, low product selectivity, complex process and the like exist.
Currently, only Shandong (Neze) Xin new energy company and Zhongkojie Langhua institute are seen as industrialized reports to build ten-thousand-ton PODEnThe device, its hundred tons class device, in 2012 completed the pilot test at gansu silver pilot base. The technology takes methanol as raw material and ionic liquid as catalyst to synthesize PODE (potassium iodide) by trioxymethylenen. The related research mainly focuses on a homogeneous reaction system taking ionic liquid as a catalyst, and the process has the inherent defects of homogeneous catalytic reaction, such as high price of the ionic liquid catalyst, difficulty in complete separation of the ionic liquid catalyst and a product in the recycling process and the like.
Since in the synthesis of PODEn, individual components of n-1-6 are produced. When the value of n is 1, the polymethoxy dimethyl ether is methylal (DMM), and the methylal serving as the vehicle fuel additive component can improve the energy utilization rate and reduce the exhaust emission, but can still cause air resistance. When n is 2, the flash point of polyoxymethylene dimethyl ether (namely polyoxymethylene dimethyl ether 2 or PODE2 for short) is too low to facilitate compression ignition, so that the n is a component of 3-6 in common use.
Synthesis and isolation of PODE was first reported in patents, but until recently, attention was drawn due to the rising price of petroleum and the stricter requirements for environmental protection. As can be seen from the international patent that has been filed, the patents filed after 1998 are the most important. Most patents obtain PODE through dehydration reaction of methanol and formaldehyde, but the presence of water in the system can increase the separation energy consumption, cause hydrolysis reaction of hemiacetal as an intermediate product of the reaction, and reduce the yield of PODE products.
In the presence of an acid catalyst, methylal and trioxymethylene (and/or paraformaldehyde) are used as raw materials to produce PODE, a reaction product is firstly separated into a top component containing DMM and a DMM tower bottom material containing PODE with n being more than or equal to 2, a small amount of water, a small amount of methanol and a small amount of trioxymethylene through a DMM separation tower at the operation pressure of 100-150 kPa, the DMM tower bottom material containing DMM is separated into a bottom component containing PODE2, a small amount of water (1-3 w%) and a small amount of methanol (1-4 w%) (sometimes containing negligible DMM) at the operation pressure of 35-60 kPa through a PODE product separation tower, and the bottom component of the PODE separation tower contains a product component with n being 3-6. In order to reduce cost and increase efficiency, PODE2 and/or DMM in the top component of the PODE separation column needs to be returned to the reactor for further reaction, but water and methanol in the top component of the PODE separation column are unfavorable for the reaction process, and water and methanol need to be removed.
W02006/045506a1 introduces a method of synthesizing paraformaldehyde dimethyl ether by BASF using a methanol derivative instead of methanol and using methylal and trioxymethylene as raw materials to obtain a series of products with n being 1-10, wherein: DMM 33.5%, PODE223.6 percent of the total weight of the active additive, namely PODE3-8Less than 28.3%; the starting material methylal of the process is not a bulk chemical, and PODE is used2The solvent as the unreacted material is recycled into the reactor, so the cost is high, the product yield is low, and the industrialized production is not facilitated.
CN 104447221a (purification method of polyoxymethylene dimethyl ether) specifically discloses a method for removing methanol in PODE2 by using cyclohexane, n-hexane, methyl formate, ethyl acetate, methyl propionate or n-heptane as an azeotropic solvent. But there is no specific disclosure of a method for separating light materials including DMM, PODE2-7, water and methanol, and how to utilize unreacted DMM and byproduct PODE2, nor is there any disclosure of a problem of water separation and a problem of separation of an acceptable product PODE 3-5.
Disclosure of Invention
The invention aims to solve the problems that in the prior art, water and methanol in a crude PODE2 material cannot be removed simultaneously in the PODE product refining process, so that a high-quality PODE2 recycled material cannot be guaranteed to be used in the PODE synthesis reaction, and the polymethoxy dimethyl ether separation method is provided, can simultaneously remove water and methanol in PODE2, and guarantees that a high-quality PODE2 recycled material is used in the PODE synthesis reaction.
In order to solve the technical problems, the technical scheme of the invention is as follows:
a polymethoxy dimethyl ether separation method, wherein a raw material 1 to be refined containing DMM, PODE2, PODE3-8, water and methanol is separated in a system comprising a PODE crude separation tower A, PODE2 separation tower B, PODE product tower C, DMM high-pressure separation tower D, a low-pressure methanol tower E, a circulating PODE2 high-pressure utilization tower F and a low-pressure dehydration tower G; the method comprises the following steps:
(a) rectifying the raw material 1 to be refined in a PODE (packed bed enhanced oil) rough separation tower A to obtain a tower top material 3 and a tower bottom material 2 which does not contain DMM basically; by way of non-limiting example, the DMM content of the essentially DMM-free bottoms 2 is 0-1% by weight; preferably greater than 0 and 0.5% or less;
(b) separating the bottom material 2 obtained in the step (a) by a PODE2 separation tower B to obtain a top material 5 and a bottom material 4 which is basically PODE 3-8; by way of non-limiting example, the content of PODE3-8 in the essentially PODE3-8 bottom material 4 is 99 to 100% by weight, preferably 99.5 to 100% by weight;
(c) feeding the tower top material 3 in the step (a) into a DMM high-pressure separation tower D to obtain a tower top material and a tower bottom material 10 which is basically DMM; part or all of the obtained bottom material 10 by weight enters a circulating PODE2 high-pressure utilization tower F; by way of non-limiting example, the DMM content of the substantially DMM bottoms 10 is 99 to 100%, preferably 99.5 to 100%, by weight; by way of non-limiting example, the proportion of the bottoms 10 entering the circulating PODE2 high pressure utilization column F is 10-80%, preferably 20-60%, more preferably 20-40% by weight;
(d) separating the tower top material obtained in the step (c) by a low-pressure methanol tower E to obtain a tower top material and a tower bottom material 11 which is basically methanol, and returning the obtained tower top material to a DMM high-pressure separation tower D; by way of non-limiting example, the methanol content of the substantially methanol bottoms 11 is 98.0 to 99.9%, preferably 99.2 to 99.9%, more preferably 99.5 to 99.9% by weight;
(e) feeding the tower top material obtained in the step (b) into a circulating PODE2 high-pressure utilization tower F; recycling PODE2 high pressure utilization column F to obtain a top material and a bottom material 8 which is basically PODE2 and DMM through separation operation; by way of non-limiting example, the base material 8, which is essentially PODE2 and DMM, has as its weight: the content of PODE2 is 40-90%, and the content of DMM is 5-40%; preferably, the content of PODE2 is 60-90%, and the content of DMM is 5-30%; more preferably, the content of PODE2 is 70-88%, and the content of DMM is 10-30%;
(f) separating the tower top material obtained in the step (e) by a low-pressure dehydrating tower G to obtain a tower top material and a tower bottom material 9 which is basically methanol and water, and returning the obtained tower top material to a circulating PODE2 high-pressure utilization tower F; by way of non-limiting example, the essentially methanol and water bottoms 9 comprises by weight: the methanol content is 20-60%, and the water content is 40-80%; preferably, the content of methanol is 20-50%, and the content of water is 50-80%; more preferably, the content of methanol is 30-40%, and the content of water is 60-80%;
(g) separating the bottom material 4 obtained in the step (b) by a PODE product tower C to obtain a product material 7 which is basically PODE3-4 and a bottom material 6 which is basically PODE 5-8; by way of non-limiting example, the content of PODE3-4 in the product material 7 which is basically PODE3-4 is 99.5-100% by weight, preferably 99.7-100% by weight; by way of non-limiting example, the content of PODE5-8 in the bottom material 6 of the substantially PODE5-8 is 99.6 to 100% by weight, preferably 99.7 to 100% by weight;
the operating pressure of the DMM high-pressure separation column D is higher than that of the low-pressure methanol column E; the recycle PODE2 high pressure utilization column F is operated at a higher pressure than the low pressure dehydration column G.
In the above technical solution, it is preferable that the operating pressure of the DMM high-pressure separation column D and the recycle PODE2 high-pressure utilization column F is at least 470 kPa; the higher the operating pressure of the DMM high-pressure separation column D and the circulating PODE2 high-pressure utilization column F is, the better the effect is, but in consideration of equipment materials and operation difficulty, 450-700 kPa is preferred.
In the above technical solution, the operating pressure of the low-pressure methanol tower E and the low-pressure dehydration tower G is preferably 200kPa or less; the pressure is preferably 100 to 200kPa because the lower the pressure is, the better the effect is, but the equipment investment is increased when the low-pressure operation reaches a negative pressure.
In the above technical solution, the operation pressure of the PODE crude separation column A is preferably 80-110kPa, the operation temperature at the top of the column is preferably 35-50 ℃, and the operation temperature at the bottom of the column is preferably 100-130 ℃.
In the above technical solution, the operation pressure of the PODE2 separation column B is preferably 30-50kPa, the operation temperature at the top of the column is preferably 70-90 ℃, and the operation temperature at the bottom of the column is preferably 125-150 ℃.
In the above technical solution, the operation pressure of the PODE product column C is preferably 35-55kPa, the operation temperature at the top of the column is 140-160 ℃ and the operation temperature at the bottom of the column is 200-240 ℃.
In the technical scheme, the tower top operation temperature of the DMM high-pressure separation tower D is preferably 85-120 ℃, and the tower bottom operation temperature is preferably 90-130 ℃.
In the technical scheme, the tower top operating temperature of the low-pressure methanol tower E is preferably 38-48 ℃, and the tower bottom operating temperature is preferably 55-75 ℃.
In the above technical solution, the operation temperature at the top of the separation column F is preferably 80-120 ℃, and the operation temperature at the bottom of the separation column F is preferably 130-170 ℃.
In the technical scheme, the operation temperature of the top of the separation tower G is preferably 38-48 ℃, and the operation temperature of the bottom of the separation tower G is preferably 75-95 ℃.
The DMM high-pressure separation tower D and the low-pressure methanol tower E can remove methanol in DMM crude materials in a high-low pressure matching operation mode, and the circulating PODE2 high-pressure utilization tower F and the low-pressure dehydration tower G can simultaneously remove water and methanol in the PODE2 crude materials in a high-low pressure matching operation mode and recover DMM.
And (b) rectifying the methanol in the raw material 1 to be refined by using the PODE crude separation tower A in the step (a), preferably, 50-95% of the total weight of the methanol enters a tower top material 3, and 5-50% of the methanol enters a tower bottom material 2.
When the raw material 1 to be refined contains impurities of trioxymethylene, the raw material is rectified by a PODE crude separation tower A in the step (a) and enters a tower bottom material 2, is separated by a PODE2 separation tower B in the step (B) and enters a tower top material 5, is separated by a circulating PODE2 high pressure utilization tower F in the step (e) and enters a tower bottom material 8, and then can be returned to the PODE synthesis process together with PODE2 and DMM.
By adopting the technical scheme of the invention, the qualified PODE3-4 can be obtained by separation, the contents of methanol and water in the returned material of PODE2 can be reduced simultaneously, and the content of methanol in the returned material DMM can also be reduced. The invention can obtain qualified PODE products and the requirements of returned materials PODE2 and DMM on methanol and water, obtains beneficial technical effects, and can be used for the refining production of PODE products.
The invention is further illustrated by the following examples in conjunction with the accompanying drawings.
Drawings
FIG. 1 is a schematic flow diagram of one embodiment of the present invention.
In fig. 1: the method comprises the following steps of 1, raw materials to be refined, wherein the raw materials comprise DMM, PODE2, PODE3-8, water and methanol, 2 is a PODE crude product basically not containing DMM, 3, column top materials are obtained by rectifying the PODE crude separation column A, 4, bottom materials basically containing PODE3-8 are obtained by separating the PODE2 separation column B, 5, column top materials are obtained by separating the PODE2 separation column B, 6, bottom materials basically containing PODE5-8 are obtained by separating the PODE product column C, 7, product materials basically containing PODE3-4 are obtained by separating the PODE product column C, 8, bottom materials basically containing PODE2 and DMM are obtained by separating the high-pressure utilization column F of circulating E2, 9, bottom materials basically containing methanol and water are obtained by separating the low-pressure dehydration column G, 10, bottom materials basically containing DMM are obtained by separating the high-pressure separation column D, and 11, and bottom materials basically containing methanol are obtained by separating the low-methanol.
A is PODE coarse separation tower, B is PODE2 separation tower, C is PODE product tower, D is DMM high-pressure separation tower, E is low-pressure methanol tower, F is circulating PODE2 high-pressure utilization tower, and G is low-pressure dehydration tower.
Detailed Description
[ example 1 ]
The operation is carried out according to the flow shown in fig. 1, and the steps are as follows:
(a) rectifying the raw material 1 to be refined in a PODE (packed bed) rough separation tower A to obtain a tower bottom material 2 and a tower top material 3 which basically do not contain DMM;
(b) separating the bottom material 2 obtained in the step (a) by a PODE2 separation tower B to obtain a top material 5 and a bottom material 4 which is basically PODE 3-8;
(c) feeding the tower top material 3 in the step (a) into a DMM high-pressure separation tower D to obtain a tower top material and a tower bottom material 10 which is basically DMM; 10 percent of the weight of the obtained tower bottom material enters a circulating PODE2 high-pressure utilization tower F;
(d) separating the tower top material obtained in the step (c) by a low-pressure methanol tower E to obtain a tower top material and a tower bottom material 11 which is basically methanol, and returning the obtained tower top material to a DMM high-pressure separation tower D;
(e) feeding the tower top material obtained in the step (b) into a circulating PODE2 high-pressure utilization tower F; recycling PODE2 high pressure utilization column F to obtain a top material and a bottom material 8 which is basically PODE2 and DMM through separation operation;
(f) separating the tower top material obtained in the step (e) by a low-pressure dehydrating tower G to obtain a tower top material and a tower bottom material 9 which is basically methanol and water, and returning the obtained tower top material to a circulating PODE2 high-pressure utilization tower F;
(g) separating the bottom material 4 obtained in the step (b) by a PODE product tower C to obtain a product material 7 which is basically PODE3-4 and a bottom material 6 which is basically PODE 5-8;
the operation pressure of the PODE rough separation tower A is 102kPa, the operation temperature of the top of the tower is 42 ℃, and the operation temperature of the bottom of the tower is 111 ℃; the operation pressure of the PODE2 separation tower B is 40kPa, the operation temperature of the tower top is 77 ℃, and the operation temperature of the tower bottom is 137 ℃; the operation pressure of a PODE product tower C is 45kPa, the operation temperature of the tower top is 151 ℃, and the operation temperature of the tower kettle is 222 ℃; the operation pressure of the DMM separation tower D is 505kPa, the operation temperature of the tower top is 93 ℃, and the operation temperature of the tower kettle is 98 ℃; the operating pressure of the methanol tower E is 101kPa, the operating temperature of the tower top is 42 ℃, and the operating temperature of the tower kettle is 65 ℃; the operation pressure of the circulating PODE2 utilization tower F is 505kPa, the operation temperature of the tower top is 95 ℃, and the operation temperature of the tower bottom is 141 ℃; the operating pressure of the dehydration column G was 102kPa, the operating temperature at the top of the column was 42 ℃ and the operating temperature at the bottom of the column was 90 ℃.
The feed composition and separation effect in example 1 are shown in tables 1 and 2. In normal operation, the methanol content of the returned PODE2 is generally limited to below 2% and the water below 1%. From tables 1 and 2, it can be seen that almost no methanol and water were contained in the returned material PODE2, and that the returned DMM contained no methanol, while an acceptable PODE3-4 product was obtained by the present invention. Therefore, the method of the invention completely meets the separation requirement required by the system and has obvious advantages.
[ example 2 ]
The operation is carried out according to the flow shown in fig. 1, and the steps are as follows:
(a) rectifying the raw material 1 to be refined in a PODE (packed bed) rough separation tower A to obtain a tower bottom material 2 and a tower top material 3 which basically do not contain DMM;
(b) separating the bottom material 2 obtained in the step (a) by a PODE2 separation tower B to obtain a top material 5 and a bottom material 4 which is basically PODE 3-8;
(c) feeding the tower top material 3 in the step (a) into a DMM high-pressure separation tower D to obtain a tower top material and a tower bottom material 10 which is basically DMM; 30 percent of the weight of the obtained tower bottom material enters a circulating PODE2 high-pressure utilization tower F;
(d) separating the tower top material obtained in the step (c) by a low-pressure methanol tower E to obtain a tower top material and a tower bottom material 11 which is basically methanol, and returning the obtained tower top material to a DMM high-pressure separation tower D;
(e) feeding the tower top material obtained in the step (b) into a circulating PODE2 high-pressure utilization tower F; recycling PODE2 high pressure utilization column F to obtain a top material and a bottom material 8 which is basically PODE2 and DMM through separation operation;
(f) separating the tower top material obtained in the step (e) by a low-pressure dehydrating tower G to obtain a tower top material and a tower bottom material 9 which is basically methanol and water, and returning the obtained tower top material to a circulating PODE2 high-pressure utilization tower F;
(g) separating the bottom material 4 obtained in the step (b) by a PODE product tower C to obtain a product material 7 which is basically PODE3-4 and a bottom material 6 which is basically PODE 5-8;
the operation pressure of the PODE rough separation tower A is 102kPa, the operation temperature of the top of the tower is 42 ℃, and the operation temperature of the bottom of the tower is 111 ℃; the operation pressure of the PODE2 separation tower B is 40kPa, the operation temperature of the tower top is 77 ℃, and the operation temperature of the tower bottom is 137 ℃; the operation pressure of a PODE product tower C is 45kPa, the operation temperature of the tower top is 151 ℃, and the operation temperature of the tower kettle is 222 ℃; the operation pressure of the DMM separation tower D is 505kPa, the operation temperature of the tower top is 93 ℃, and the operation temperature of the tower kettle is 98 ℃; the operating pressure of the methanol tower E is 101kPa, the operating temperature of the tower top is 42 ℃, and the operating temperature of the tower kettle is 65 ℃; the operation pressure of the circulating PODE2 utilization tower F is 505kPa, the operation temperature of the tower top is 95 ℃, and the operation temperature of the tower bottom is 141 ℃; the operating pressure of the dehydration column G was 102kPa, the operating temperature at the top of the column was 42 ℃ and the operating temperature at the bottom of the column was 90 ℃.
The feed composition and separation effect in example 2 are shown in tables 3 and 4. In normal operation, the methanol content of the returned PODE2 is generally limited to below 2% and the water below 1%. From tables 3 and 4, it can be seen that there was almost no methanol and water in the returned material PODE2, and that the returned DMM contained no methanol, while an acceptable PODE3-4 product was obtained by the present invention. Therefore, the method of the invention completely meets the separation requirement required by the system and has obvious advantages.
[ example 3 ]
The operation is carried out according to the flow shown in fig. 1, and the steps are as follows:
(a) rectifying the raw material 1 to be refined in a PODE (packed bed) rough separation tower A to obtain a tower bottom material 2 and a tower top material 3 which basically do not contain DMM;
(b) separating the bottom material 2 obtained in the step (a) by a PODE2 separation tower B to obtain a top material 5 and a bottom material 4 which is basically PODE 3-8;
(c) feeding the tower top material 3 in the step (a) into a DMM high-pressure separation tower D to obtain a tower top material and a tower bottom material 10 which is basically DMM; 10 percent of the weight of the obtained tower bottom material enters a circulating PODE2 high-pressure utilization tower F;
(d) separating the tower top material obtained in the step (c) by a low-pressure methanol tower E to obtain a tower top material and a tower bottom material 11 which is basically methanol, and returning the obtained tower top material to a DMM high-pressure separation tower D;
(e) feeding the tower top material obtained in the step (b) into a circulating PODE2 high-pressure utilization tower F; recycling PODE2 high pressure utilization column F to obtain a top material and a bottom material 8 which is basically PODE2 and DMM through separation operation;
(f) separating the tower top material obtained in the step (e) by a low-pressure dehydrating tower G to obtain a tower top material and a tower bottom material 9 which is basically methanol and water, and returning the obtained tower top material to a circulating PODE2 high-pressure utilization tower F;
(g) separating the bottom material 4 obtained in the step (b) by a PODE product tower C to obtain a product material 7 which is basically PODE3-4 and a bottom material 6 which is basically PODE 5-8;
the operation pressure of the PODE rough separation tower A is 110kPa, the operation temperature of the top of the tower is 44 ℃, and the operation temperature of the bottom of the tower is 115 ℃; the operation pressure of the PODE2 separation tower B is 50kPa, the operation temperature of the tower top is 84 ℃, and the operation temperature of the tower bottom is 144 ℃; the operation pressure of a PODE product tower C is 55kPa, the operation temperature of the tower top is 156 ℃, and the operation temperature of the tower kettle is 228 ℃; the operation pressure of the DMM separation tower D is 700kPa, the operation temperature of the tower top is 106 ℃, and the operation temperature of the tower kettle is 113 ℃; the operating pressure of the methanol tower E is 100kPa, the operating temperature of the tower top is 41 ℃, and the operating temperature of the tower kettle is 65 ℃; the operating pressure of the circulating PODE2 utilization tower F is 700kPa, the tower top operating temperature is 109 ℃, and the tower bottom operating temperature is 156 ℃; the operating pressure of the dehydration column G was 102kPa, the operating temperature at the top of the column was 42 ℃ and the operating temperature at the bottom of the column was 90 ℃.
The feed composition and separation effect in example 3 are shown in tables 5 and 6. In normal operation, the methanol content of the returned PODE2 is generally limited to below 2% and the water below 1%. From tables 5 and 6, it can be seen that there was almost no methanol and water in the returned material PODE2, and that the returned DMM contained no methanol, while an acceptable PODE3-4 product was obtained by the present invention. Therefore, the method of the invention completely meets the separation requirement required by the system and has obvious advantages.
[ COMPARATIVE EXAMPLE 1 ]
The operation is carried out according to the flow shown in fig. 1, and the steps are as follows:
(a) rectifying the raw material 1 to be refined in a PODE (packed bed) rough separation tower A to obtain a tower bottom material 2 and a tower top material 3 which basically do not contain DMM;
(b) separating the bottom material 2 obtained in the step (a) by a PODE2 separation tower B to obtain a top material 5 and a bottom material 4 which is basically PODE 3-8;
(c) feeding the tower top material 3 in the step (a) into a DMM high-pressure separation tower D to obtain a tower top material and a tower bottom material 10 which is basically DMM; 10 percent of the weight of the obtained tower bottom material enters a circulating PODE2 high-pressure utilization tower F;
(d) separating the tower top material obtained in the step (c) by a low-pressure methanol tower E to obtain a tower top material and a tower bottom material 11 which is basically methanol, and returning the obtained tower top material to a DMM high-pressure separation tower D;
(e) feeding the tower top material obtained in the step (b) into a circulating PODE2 high-pressure utilization tower F; recycling PODE2 high pressure utilization column F to obtain a top material and a bottom material 8 which is basically PODE2 and DMM through separation operation;
(f) separating the tower top material obtained in the step (e) by a low-pressure dehydrating tower G to obtain a tower top material and a tower bottom material 9 which is basically methanol and water, and returning the obtained tower top material to a circulating PODE2 high-pressure utilization tower F;
(g) separating the bottom material 4 obtained in the step (b) by a PODE product tower C to obtain a product material 7 which is basically PODE3-4 and a bottom material 6 which is basically PODE 5-8;
in comparative example 3, the operating conditions of other towers are not changed, and only the operating pressure of the DMM separation tower D is changed, namely the operating pressure of the PODE rough separation tower A is 110kPa, the operating temperature of the tower top is 44 ℃, and the operating temperature of the tower bottom is 115 ℃; the operation pressure of the PODE2 separation tower B is 50kPa, the operation temperature of the tower top is 84 ℃, and the operation temperature of the tower bottom is 144 ℃; the operation pressure of a PODE product tower C is 55kPa, the operation temperature of the tower top is 156 ℃, and the operation temperature of the tower kettle is 228 ℃; the operation pressure of the DMM separation tower D is 450kPa, the operation temperature of the top of the tower is 83 ℃, and the operation temperature of the bottom of the tower is 89 ℃; the operating pressure of the methanol tower E is 100kPa, the operating temperature of the tower top is 41 ℃, and the operating temperature of the tower kettle is 65 ℃; the operating pressure of the circulating PODE2 utilization tower F is 700kPa, the tower top operating temperature is 109 ℃, and the tower bottom operating temperature is 156 ℃; the operating pressure of the dehydration column G was 102kPa, the operating temperature at the top of the column was 42 ℃ and the operating temperature at the bottom of the column was 90 ℃.
The feed composition and separation effect of the feed in comparative example 1 are shown in tables 7 and 8. In normal operation, the methanol content of the DMM is typically limited to below 2% and water below 1% for the returned PODE 2. From tables 7 and 8, it can be found that the recycle PODE2 has almost no methanol and water in the returned material PODE2 because the high pressure operation of the column F and the dehydration column G meets the requirements of the invention conditions, but the high pressure of the DMM separation column D is only 450kPa, which results in higher methanol content of DMM returned in the combined operation with the subsequent methanol column E, which cannot meet the requirements of the methanol content in the returned material DMM, and the DMM cannot be recycled, so that each column must be operated strictly in accordance with the requirements of the invention, and the separation requirements required by the system can be met based on the process and condition requirements of the invention.
[ COMPARATIVE EXAMPLE 2 ]
The operation is carried out according to the flow shown in fig. 1, and the steps are as follows:
(a) rectifying the raw material 1 to be refined in a PODE (packed bed) rough separation tower A to obtain a tower bottom material 2 and a tower top material 3 which basically do not contain DMM;
(b) separating the bottom material 2 obtained in the step (a) by a PODE2 separation tower B to obtain a top material 5 and a bottom material 4 which is basically PODE 3-8;
(c) feeding the tower top material 3 in the step (a) into a DMM high-pressure separation tower D to obtain a tower top material and a tower bottom material 10 which is basically DMM; 10 percent of the weight of the obtained tower bottom material enters a circulating PODE2 high-pressure utilization tower F;
(d) separating the tower top material obtained in the step (c) by a low-pressure methanol tower E to obtain a tower top material and a tower bottom material 11 which is basically methanol, and returning the obtained tower top material to a DMM high-pressure separation tower D;
(e) feeding the tower top material obtained in the step (b) into a circulating PODE2 high-pressure utilization tower F; recycling PODE2 high pressure utilization column F to obtain a top material and a bottom material 8 which is basically PODE2 and DMM through separation operation;
(f) separating the tower top material obtained in the step (e) by a low-pressure dehydrating tower G to obtain a tower top material and a tower bottom material 9 which is basically methanol and water, and returning the obtained tower top material to a circulating PODE2 high-pressure utilization tower F;
(g) separating the bottom material 4 obtained in the step (b) by a PODE product tower C to obtain a product material 7 which is basically PODE3-4 and a bottom material 6 which is basically PODE 5-8;
comparative example 3, the operating conditions of the other columns were not changed, and only the operating pressure of the high-pressure utilization column F of the circulating PODE2 was changed, that is, the operating pressure of the crude separation column a of the PODE was 110kPa, the operating temperature of the top of the column was 44 ℃, and the operating temperature of the bottom of the column was 115 ℃; the operation pressure of the PODE2 separation tower B is 50kPa, the operation temperature of the tower top is 84 ℃, and the operation temperature of the tower bottom is 144 ℃; the operation pressure of a PODE product tower C is 55kPa, the operation temperature of the tower top is 156 ℃, and the operation temperature of the tower kettle is 228 ℃; the operation pressure of the DMM separation tower D is 700kPa, the operation temperature of the tower top is 106 ℃, and the operation temperature of the tower kettle is 113 ℃; the operating pressure of the methanol tower E is 100kPa, the operating temperature of the tower top is 41 ℃, and the operating temperature of the tower kettle is 65 ℃; the operating pressure of the circulating PODE2 utilization tower F is 450kPa, the tower top operating temperature is 85 ℃, and the tower bottom operating temperature is 130 ℃; the operating pressure of the dehydration column G was 102kPa, the operating temperature at the top of the column was 42 ℃ and the operating temperature at the bottom of the column was 90 ℃.
The feed composition and separation effect in comparative example 2 are shown in tables 9 and 10. In normal operation, the methanol content of the DMM is typically limited to below 2% and water below 1% for the returned PODE 2. From tables 9 and 10, it can be found that the returned material DMM has almost no methanol because the high and low pressure operation of the DMM separation column D and the methanol column E satisfies the requirements of the invention conditions, but the recycle PODE2 uses the high pressure of the column F of only 450kPa, which results in higher methanol and water content in the PODE2 returned in the combined operation with the subsequent dehydration column G, cannot satisfy the requirements of the returned material PODE2 for methanol and water content, and cannot recycle the PODE2, so that each column must be operated strictly in accordance with the requirements of the invention, and the separation requirements required by the system can be achieved based on the process and condition requirements of the invention.
TABLE 1 Material Mass composition Structure
TABLE 2 Material Mass fraction composition Structure
TABLE 3 Material Mass composition Structure
TABLE 4 composition of mass fractions of materials
TABLE 5 Material Mass constitution Structure
TABLE 6 composition of mass fractions of materials
TABLE 7 Material Mass constitution Structure
TABLE 8 composition of mass fractions of materials
TABLE 9 Material Mass constitution Structure
TABLE 10 composition of mass fractions of materials
Claims (8)
1. A method for separating polymethoxy dimethyl ether comprises the following steps of separating a raw material (1) to be refined, which contains DMM, PODE2, PODE3-8, water and methanol, in a system comprising a PODE crude separation tower (A), a PODE2 separation tower (B), a PODE product tower (C), a DMM high-pressure separation tower (D), a low-pressure methanol tower (E), a circulating PODE2 high-pressure utilization tower (F) and a low-pressure dehydration tower (G), wherein the steps are as follows:
(a) rectifying the raw material (1) to be refined in a PODE (propylene glycol ether) crude separation tower (A) to obtain a tower top material (3) and a tower bottom material (2) basically containing no DMM;
(b) separating the bottom material (2) obtained in the step (a) by a PODE2 separation tower (B) to obtain a top material (5) and a bottom material (4) which is basically PODE 3-8;
(c) feeding the tower top material (3) in the step (a) into a DMM high-pressure separation tower (D) to obtain a tower top material and a tower bottom material (10) which is basically DMM; part or all of the obtained tower bottom materials enter a circulating PODE2 high-pressure utilization tower (F);
(d) separating the tower top material obtained in the step (c) by a low-pressure methanol tower (E) to obtain a tower top material and a tower bottom material (11) which is basically methanol, and returning the obtained tower top material to a DMM high-pressure separation tower (D);
(e) feeding the tower top material obtained in the step (b) into a circulating PODE2 high-pressure utilization tower (F); recycling the PODE2 high pressure utilization column (F) to obtain a top material and a bottom material (8) which is substantially PODE2 and DMM;
(f) separating the tower top material obtained in the step (e) by a low-pressure dehydration tower (G) to obtain a tower top material and a tower bottom material (9) which is basically methanol and water, and returning the obtained tower top material to a circulating PODE2 high-pressure utilization tower (F);
(g) separating the bottom material (4) obtained in the step (b) by a PODE product tower (C) to obtain a product material (7) which is basically PODE3-4 and a bottom material (6) which is basically PODE 5-8;
the DMM high pressure separation column (D) and the recycle PODE2 high pressure utilization column (F) are operated at a pressure of at least 470 kPa;
the operating pressure of the low-pressure methanol column (E) and the low-pressure dehydration column (G) is 200kPa or less.
2. The separation process of polymethoxy dimethyl ether according to claim 1, wherein the operation pressure of the PODE crude separation column (A) is 80-110kPa, the operation temperature of the column top is 35-50 ℃, and the operation temperature of the column bottom is 100-130 ℃.
3. The process according to claim 1, wherein the PODE2 separation column (B) is operated at 30-50kPa, the top temperature is 70-90 ℃ and the bottom temperature is 125-150 ℃.
4. The separation process of polymethoxy dimethyl ether according to claim 1, wherein the PODE product column (C) has an operating pressure of 35-55kPa, an operating temperature at the top of the column of 140-160 ℃ and an operating temperature at the bottom of the column of 200-240 ℃.
5. The process for separating polymethoxy dimethyl ether according to claim 1, wherein the DMM high-pressure separation column (D) has an operation temperature of 85 to 120 ℃ at the top and an operation temperature of 90 to 130 ℃ at the bottom.
6. The process according to claim 1, wherein the operating temperature of the low-pressure methanol column (E) is 38-48 ℃ at the top and 55-75 ℃ at the bottom.
7. The method for separating polymethoxy dimethyl ether according to claim 1, wherein the operation temperature of the separation column F is 80-120 ℃ at the top of the column and 130-170 ℃ at the bottom of the column.
8. The process for separating polymethoxy dimethyl ether according to claim 1, wherein the separation column G has an operation temperature of 38 to 48 ℃ at the top and 75 to 95 ℃ at the bottom.
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| WO2006045506A1 (en) * | 2004-10-25 | 2006-05-04 | Basf Aktiengesellschaft | Method for producing polyoxymethylene dimethyl ethers |
| CN104058940A (en) * | 2014-06-30 | 2014-09-24 | 西安市尚华科技开发有限责任公司 | Method for synthesizing PODE through condensation, oxidation, polycondensation and etherification of methyl alcohol |
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| WO2006045506A1 (en) * | 2004-10-25 | 2006-05-04 | Basf Aktiengesellschaft | Method for producing polyoxymethylene dimethyl ethers |
| CN104058940A (en) * | 2014-06-30 | 2014-09-24 | 西安市尚华科技开发有限责任公司 | Method for synthesizing PODE through condensation, oxidation, polycondensation and etherification of methyl alcohol |
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