RU2564420C2 - Method of producing dimethyl ehter from methanol - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method includes contacting methanol with a dehydrating catalyst in a reaction zone and separating components of the reaction mixture by fractionation while returning unreacted methanol into the reaction zone, wherein dehydration of methanol and formation of ether are carried out in the presence of a catalyst at a high temperature. The catalyst used is zeolite-type molecular sieves with large pores, selected from a group consisting of FAU structure zeolites, which are type-X zeolites or modifications thereof; dehydration is carried out in a gaseous state at temperature in the reaction zone of 280-330°C and pressure of 17-22 atm; in the first fractionation column, a fraction consisting of methanol and dimethyl ether is distilled from water, and in the second fractionation column, dimethyl ether is distilled from unreacted methanol and the methanol is returned to the reaction zone.

EFFECT: method enables to obtain dimethyl ether with high output and purity.

1 dwg, 1 tbl, 4 ex

Description

Technical field

This invention relates to the chemical industry, specifically to the field of production of dimethyl ether (DME), used as a refrigerant and a gas displacer aerosol packaging.

The quality of gas purification of the displacer determines its use in those industries where the gas requirements for the content of mercaptans and moisture are very high (perfumes and cosmetics, medical aerosols, production of car cosmetics, foam, paint and varnish products).

State of the art

Many processes are known in which DME is produced by the dehydration of methanol using various catalysts.

According to the patent [1] [patent RU 2459799, C2, publication date 08/27/2012] molecular zeolite and / or non-zeolite molecular sieves can be used as catalysts. As molecular sieves, one or more sieves are used, with an FAU structure selected from the group consisting of Y-type zeolites that have large pores. The non-zeolitic molecular sieve may be silicoaluminophosphate.

The disadvantages of this method include a high tendency to oblique catalysts at the reaction temperature.

In the patent [2] [patent RU 2282613, C2, publication date 08/27/2006], methanol dehydration is carried out in the presence of a sulfoionite catalyst at elevated temperature and pressure in a combined reactive distillation apparatus.

The closest in its technical essence and the achieved technical result is the invention "A method for producing dimethyl ether" [3], [patent RU No. 2256645, C2, publication date 07/20/2005]. According to the invention, the methanol-containing stream is contacted with a dehydrating catalyst in one or more reaction zones. The components of the reaction mixture by distillation and / or rectification are separated with the return of unreacted methanol to the reaction zone. Methanol dehydration and ether formation are carried out in liquid and / or vapor-liquid state in the presence of acidic cation exchange resin at a temperature of 100-460 ° C and the concentration of water in the returned reaction zone of the methanol stream is less than 12 wt%, preferably less than 5 wt%.

The main disadvantages of the prototype are:

- the use of a two-reactor scheme for dehydration;

- the use of water washing the selected stream of dimethyl ether from methanol and supplying the water-methanol mixture to the rectification zone from water;

- the use of a reactive distillation apparatus will complicate the technological scheme.

The objective of the proposed method is to create an environmentally friendly technology for the production of DME by methanol dehydration on a zeolite type molecular sieve, which will make it possible to obtain products of the required quality for use as a gas displacer for aerosol packages and significantly reduce operating and capital costs for the implementation and implementation of the process.

Disclosure of invention

The problem is achieved in that in the method for producing dimethyl ether from methanol, by contacting it with a dehydrating catalyst in the reaction zone and separating the components of the reaction mixture by distillation, the unreacted methanol is returned to the reaction zone, in which methanol is dehydrated in the presence of a catalyst at elevated temperature , unlike the prototype, molecular sieves of the zeolite type with large pores selected from the group consisting of consisting of zeolites of the FAU structure, which are type X zeolites and their modifications, dehydration is carried out in a gaseous state at a temperature in the reaction zone of 280 ÷ 380 ° C and a pressure of 17 ÷ 22 atm, in the first distillation column, the fraction consisting of methanol and dimethyl is distilled from water ether, in the second distillation column dimethyl ether is distilled off from unreacted methanol and methanol is returned to the reaction zone. The proposed method for producing dimethyl ether is carried out on the installation, which is presented in the drawing, which shows a schematic diagram of the installation.

Installation works as follows.

To obtain DME, methanol concentrations of not less than 99.5%, mass fraction of sulfur not more than 0.0001%, mass fraction of water not more than 0.05%, mass fraction of aldehydes and ketones not more than 0.003% are used.

According to the installation diagram in the drawing, methanol enters through line 1. It is mixed with recirculated methanol stream 11 coming from the bottom of column 14, heated in a heat exchanger to a temperature of 300-350 ° C, and sent via line 2 to the reaction zone of reactor 12 containing zeolite type X The reaction mixture is withdrawn from the reaction zone of the reactor 12 through line 3, which is fed to the distillation zone of column 13 via line 3. The distillation zone of column 13 is a distillation column.

At the top of the distillation column 13, a steam stream is removed via line 5, containing mainly DME and methanol. Next, the stream is cooled in a condenser and reflux condenser and enters the column 14 via line 7. Part of the condensed stream through line 6 is returned to the column 13 in the form of reflux. From the bottom of the column 13, a stream containing mainly water is discharged along line 4. Distillation column 14 is designed to separate DME from methanol. At the top of the distillation column 14, a steam stream containing DME is discharged via line 8. Next, the flow is cooled in a condenser reflux condenser and enters line 10 to the warehouse. Part of the condensed stream through line 9 is returned to the column 14 in the form of reflux. From the bottom of column 14, a stream containing predominantly methanol is discharged along line 11.

Examples 1-4 show the implementation of the present invention by a method for producing dimethyl ether by contacting it with dehydrating catalysts using various options for loading large pore zeolite type molecular sieves into the reaction zone selected from the group consisting of zeolites of the FAU structure, which are type X zeolites .

Example 1. This example illustrates the implementation of the method for producing dimethyl ether using a large pore zeolite type molecular sieve as a catalyst selected from the group consisting of zeolites of the FAU structure, which is NaX zeolite.

The method of obtaining DME is implemented on the installation, see drawing.

According to the installation scheme in the drawing, methanol in the amount of 463.3 kg / h is supplied via line 1. It is mixed with the recirculated methanol stream 11 coming from the bottom of the column 14, heated in the heat exchanger mainly to a temperature of 310 ° C and sent to line 2 in the reaction zone reactor 12 containing a NaX type zeolite, granule size 1.8 ÷ 2.2 mm, in an amount of 0.5 m ³ . The reactor is an adiabatic type apparatus. The dehydration reaction is carried out at a temperature of 300 ° C and a pressure of 2.0 MPa. Methanol conversion per passage 90%. The reaction mixture is withdrawn from the reaction zone through line 3. The reaction mixture from the reactor 12 in an amount of 1000 kg / h is fed into the distillation column 13 via line 3. Stream 3 contains 32.31% DME; 53.67% methanol and 14.02% water. The rectification process is carried out at an absolute pressure in the cube of the column 13 equal to 0.37 MPa, the top of the column 13 equal to 0.32 MPa. Temperature: cuba - 140 ° C; food plates - 55 ° C; top - 40 ° C.

At the top of the distillation column 13, a steam stream containing DME and methanol is discharged along line 5. Next, the stream is cooled in a condenser and reflux condenser and enters column 14, 859.8 kg / h of product containing 37.60% DME and 62.40% methanol are discharged through line 7. Part of the condensed stream through line 6 is returned to the column 13 in the form of reflux. From the bottom of the column 13, a stream is discharged along line 4, containing mainly water in an amount of 140.2 kg / h. Distillation column 14 is designed to separate DME from methanol. At the top of the distillation column 14, a steam stream containing DME is discharged via line 8. Next, the flow is cooled in a condenser and reflux condenser and enters via line 10 to the warehouse in the amount of 323.1 kg / h. Part of the condensed stream through line 9 is returned to the column 14 as reflux. Bottom of column 14 along line 11 is a stream containing predominantly methanol in an amount of 536.7 kg / h.

Example 2. This example illustrates the implementation of the method for producing dimethyl ether analogously to example 1, characterized in that the catalyst used is a large-pore zeolite type molecular sieve selected from the group consisting of zeolites of the FAU structure, which is HX zeolite.

Example 3. This example illustrates the implementation of the method for producing dimethyl ether analogously to example 1, characterized in that the catalyst used is a large-pore zeolite type molecular sieve selected from the group consisting of zeolites of the FAU structure, which are LiX zeolite.

Example 4. This example illustrates the implementation of the method for producing dimethyl ether analogously to example 1, characterized in that the catalyst used is a large-pore zeolite type molecular sieve selected from the group consisting of zeolites of the FAU structure, which are HLiX zeolite.

The quality indicators of the obtained dimethyl ethers are shown in table 1.

Achievable technical result

The advantage of the claimed installation over the prototype are:

- obtaining DME of a high concentration of 99.99% and higher without an odor, which will allow it to be used as a gas displacer aerosol packaging;

- obtaining high quality DME with a low water content of up to 0.0001%;

- obtaining DME with a low content of sulfur compounds up to 0.0001%;

- a catalyst for the methanol dehydration in the form of large-pore zeolite type molecular sieves selected from the group consisting of zeolites of the FAU structure, which are type X zeolites and their modifications, which allowed increasing the DME conversion to 90% and higher, was proposed.

Claims (1)

 A method of producing dimethyl ether from methanol by contacting it with a dehydrating catalyst in the reaction zone and separating the components of the reaction mixture by distillation to return unreacted methanol to the reaction zone, in which methanol dehydration and ether formation are carried out in the presence of a catalyst at an elevated temperature, characterized in that molecular sieves of the zeolite type with large pores selected from the group consisting of zeolites of the structure are used as a catalyst FAUs, which are type X zeolites and their modifications, dehydration is carried out in a gaseous state at a temperature in the reaction zone of 280 ÷ 330 ° C and a pressure of 17 ÷ 22 atm, in the first distillation column, a fraction consisting of methanol and dimethyl ether is distilled off from water, in the second dimethyl ether is distilled off from the unreacted methanol by a distillation column and methanol is returned to the reaction zone.

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