RU2458900C1 - Method of producing isoprene - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing isoprene, involving liquid-phase condensation of isobutylene in form of an isobutylene-containing C₄ fraction with aqueous formaldehyde solution in the presence of an acid catalyst at high temperature and pressure to form 4,4-dimethyl-1,3-dioxane and a mixture of high-boiling by-products, followed by liquid-phase decomposition of the obtained 4,4-dimethyl-1,3-dioxane to isoprene in the presence of trimethyl carbinol and/or isobutylene and an aqueous solution of an acid catalyst at high temperature and pressure. The method is characterised by that 4,4-dimethyl-1,3-dioxane and a mixture of high-boiling by-products are separated from the condensation products by fractionation, where said mixture is then distilled on a vacuum fractionation column with collection of distillate in amount of 10-50 wt % from the column feed, followed by feeding the collected distillate for liquid-phase decomposition to isoprene in the presence of trimethyl carbinol and/or isobutylene and aqueous solution of the acid catalyst at temperature 150-200°C, pressure 0.6-1.7 MPa together with 4,4-dimethyl-1,3-dioxane and/or in a separate reactor.

EFFECT: method simplifies the process by eliminating gum formation and increases output of isoprene from the same amount of raw material.

3 cl, 4 ex, 1 tbl

Description

The invention relates to the petrochemical industry, more specifically to the field of monomers for the synthesis of polymers. More specifically, the invention relates to the field of isoprene production.

Isoprene is a monomer in the production of polyisoprene rubber, butyl rubber, isoprene-containing polymers, which are used in the tire industry and in the manufacture of rubber products.

A known method of producing isoprene, including the condensation of isobutylene in the form of isobutylene-containing fraction C ₄ with an aqueous solution of formaldehyde in the presence of an acid catalyst at a temperature of 80-100 ° C and a pressure of 1.6-2.0 MPa, separation of the reaction mass into water and oil layers, evaporation aqueous layer, adding formaldehyde to the residue after evaporation of the initial aqueous solution and recirculating the resulting mixture into the condensation zone, isolation of 4,4-dimethyl-1,3-dioxane (DMD) and a mixture of high-boiling by-products from the oil layer (WFP), followed by heterogeneous-catalytic decomposition of the resulting DMD into isoprene on a calcium phosphate catalyst at a temperature of 290-380 ° C, a pressure of 0.12-0.16 MPa in the presence of water vapor [P. Kirpichnikov, V. Beresnev. V., Popova L.M. The album of technological schemes of the main industries of the synthetic rubber industry. - L .: Chemistry, 1986, p. 36-53]. The disadvantage of this method is the high energy costs associated with the consumption of water vapor for the heterogeneous catalytic decomposition of DMD and for the release of formaldehyde from the resulting dilute aqueous solutions. Another disadvantage is the significant runway yield - process wastes. Runways are formed in the amount of 440-460 kg per 1 ton of isoprene.

A similar method for producing isoprene is known, including condensation of isobutylene in the form of an isobutylene-containing C ₄ fraction with an aqueous solution of formaldehyde in the presence of an acid catalyst at a temperature of 80-100 ° C and a pressure of 1.6-2.0 MPa, separation of the reaction mixture into water and oil layers, evaporation of the aqueous layer, adding formaldehyde to the residue after evaporation of the initial aqueous solution and recirculation of the resulting mixture into the condensation zone, isolation of DMD and the runway mixture by distillation from the oil layer, followed by heterogeneous catalytic he decomposition of the obtained DMD in isoprene on a calcium phosphate catalyst at a temperature of 290-380 ° C, a pressure of 0.12-0.16 MPa in the presence of water vapor. Moreover, the resulting runway mixture is distilled in a vacuum distillation column and distillate in an amount of 30-35% wt. from the feed columns are sent for heterogeneous catalytic decomposition into isoprene on a ceramic nozzle at a temperature of 400-450 ° C, a pressure of 0.12-0.16 MPa in the presence of water vapor [RU 2255929 C1, publ. 07/10/2005]. The disadvantage of this method is also the high energy consumption associated with the consumption of water vapor for the heterogeneous catalytic decomposition of DMD, runway and for the release of formaldehyde from the resulting dilute aqueous solutions. Another disadvantage is the decomposition of the runway separately from DMD and in various conditions.

Known methods for producing isoprene, including the liquid-phase interaction of isobutylene or isobutylene-containing C ₄ hydrocarbon mixture with an aqueous solution of formaldehyde in the presence of an acid catalyst with intermediate formation of an intermediate product - DMD and its subsequent liquid-phase decomposition into isoprene, carried out in the presence of isobutylene, TMC and an aqueous solution of an acid catalyst at elevated temperature and pressure [RU 2131863 C1, 06/20/1999; RU 2167138 C2, 05.20.2001; RU 2202530 C2, 04/20/2003].

Closest to the claimed is a known method for producing isoprene, comprising the condensation of isobutylene in the form of isobutylene-containing fraction C ₄ with an aqueous solution of formaldehyde in the presence of an acid catalyst at a temperature of 70-90 ° C, a pressure of 1.5-2.0 MPa with the intermediate formation of DMD and the subsequent liquid-phase decomposition of DMD into isoprene in the presence of isobutylene, TMK and an aqueous solution of an acid catalyst at a temperature of 150-170 ° C, a pressure of 0.5-0.7 MPa. Moreover, the reaction mixture obtained at the condensation stage after distillation of unconverted C ₄ hydrocarbons from it is fed to isoprene for decomposition into isoprene [RU 2230054 C2, 06/10/2004 - prototype].

The disadvantage of the above method is the increased formation and accumulation of resins during decomposition into the isoprene of the reaction mass of the condensation stage, which leads to clogging of the equipment and shutdown of the process. Another disadvantage is the increased yield of runways formed in the process at the stage of condensation of isobutylene with formaldehyde. The number of runways is 280-290 kg per 1 ton of isoprene.

The objective of the proposed method is to simplify the process technology by eliminating gum formation and increasing the production of isoprene from the same amount of raw material.

This problem is solved by the method of producing isoprene, including liquid-phase condensation of isobutylene in the form of isobutylene-containing fraction C ₄ with an aqueous solution of formaldehyde in the presence of an acid catalyst at elevated temperature and pressure. DMD and a runway mixture are isolated from condensation products by rectification. The resulting DMD is fed to isoprene for liquid phase decomposition in the presence of TMC and / or isobutylene and an aqueous solution of an acid catalyst at elevated temperature and pressure. The resulting runway mixture is distilled on a vacuum distillation column with the selection of distillate in an amount of 10-50% wt. from the power of the column. The selected distillate is sent for liquid phase decomposition into isoprene in the presence of TMC and / or isobutylene and an aqueous solution of an acid catalyst at a temperature of 150-200 ° C, a pressure of 0.6-1.7 MPa together with DMD and / or in a separate reactor.

The condensation of isobutylene with formaldehyde is preferably carried out at a temperature of 80-110 ° C and a pressure of 1.3-2.5 MPa.

The decomposition of DMD is preferably carried out at a temperature of 150-200 ° C and a pressure of 0.6-1.7 MPa.

As the acid catalyst in the process, various water-soluble strong mineral and / or organic acids, mixtures of acids, for example phosphoric, oxalic, and a mixture of phosphoric and oxalic acids are used.

In the proposed method, resin formation and clogging of the equipment with resins do not occur. The distilled part (10-50% wt.) Of the runway mixture is used in the process itself to obtain additional isoprene. The waste of the process is the bottom residue of the distillation distillation column of the runway.

The difference between the proposed method and the prototype is that DMD and a runway mixture are isolated from the condensation products, which is then distilled on a vacuum distillation column with a selection of distillate in the amount of 10-50% wt. from the power of the column. Another difference is that the selected distillate is sent for liquid phase decomposition into isoprene in the presence of TMC and / or isobutylene and an aqueous solution of an acid catalyst at a temperature of 150-200 ° C, a pressure of 0.6-1.7 MPa together with DMD and / or in a separate reactor.

The proposed method in comparison with the prototype allows to simplify the process technology, as well as reduce the amount of waste in the form of runways to 140-255 kg per 1 ton of isoprene and increase the production of isoprene by 1.3-4.8% from the same amount of feedstock.

Industrial application of the proposed method is illustrated by examples.

Example 1

In the tubular reactor for the synthesis of DMD serves isobutane-isobutylene fraction containing 41.3% wt. isobutylene, with a speed of 10100 kg / h, as well as a formaldehyde mixture, which is an aqueous solution containing 26.5% wt. formaldehyde, 1.2% wt. oxalic acid and 1.8% wt. phosphoric acid, with a speed of 14800 kg / h.

The synthesis of DMD is carried out in liquid-phase conditions, the temperature is maintained in the reactor at 100 ° C, and a pressure of 2.0 MPa. The conversion of formaldehyde in the reactor is 81.6%, the conversion of isobutylene 80.7%.

Coming out of the reactor, the reaction mass is separated into water and oil layers.

The aqueous layer was evaporated, the residue after evaporation was mixed with the initial aqueous solution of formaldehyde, then the resulting mixture was recycled to the reactor as a formaldehyde charge.

The oil layer is washed with water, then subjected to distillation processing to isolate the products of the synthesis of DMD.

At the first (along the flow of the oil layer) distillation column, the spent isobutane-isobutylene fraction is distilled off, which is sent to the isobutane dehydrogenation process.

The bottom liquid of the first column is fed to the second distillation column, where the trimethylcarbinol fraction is distilled off, which is recycled to the DMD synthesis reactor.

The bottom liquid of the second column is fed to the third distillation column, where 4860 kg / h of DMD are distilled off, which is sent to isoprene for liquid phase decomposition.

The residue obtained after distillation of DMD in an amount of 1100 kg / h is a runway mixture, which is fed to a vacuum distillation column, from which the selected distillate is sent for liquid phase decomposition into isoprene.

4860 kg / h of DMD, as well as 14500 kg / h of TMK and 15200 kg / h of an aqueous solution containing 5.8% by weight are fed to the DMD decomposition reactor, which is a steam-heated shell-and-tube heat exchanger. phosphoric acid. The reactor is maintained at a temperature of 160 ° C and a pressure of 0.9 MPa. A vapor-liquid stream of reaction products containing isoprene and part of the water is discharged from the top of the reactor. This stream is cooled, condensed and isoprene is released. After processing the reaction products, 3830 kg / h of isoprene are obtained. Before vacuum distillation, the number of runways (1100 kg / h) per 1 ton of isoprene obtained is 287 kg.

1100 kg / h runway mixture is fed into a vacuum distillation column, where they support the following mode of operation:

top temperature, ° С 110-125 cube temperature, ° С 150-165 pressure, MPa 0.002-0.005.

110 kg / h of distillate are taken from the top of this column. The fraction of the selected distillate is 10% wt. from the power of the column. From the bottom of the column, 990 kg / h of bottoms are removed, which is a waste of the process.

110 kg / h of the selected distillate of the runway distillation column is sent for liquid phase decomposition into isoprene into a separate shell-and-tube reactor heated by steam, which also serves 310 kg / h of TMK and 320 kg / h of an aqueous solution containing 5.8% wt. phosphoric acid. The reactor is maintained at a temperature of 150 ° C and a pressure of 0.6 MPa. A vapor-liquid stream of reaction products containing isoprene and part of the water is discharged from the top of the reactor. This stream is cooled, condensed and isoprene is released. After processing the reaction products, 50 kg / h of isoprene are obtained, which is combined with the main stream of isoprene obtained by decomposition of DMD, and then used to produce polyisoprene rubber.

Thus, as a result of the process with liquid-phase decomposition of the specified distilled part of the runway mixture, the total amount of isoprene obtained from the same amount of feedstock increases to 3880 kg / h or 1.3% wt. The amount of waste in the form of a runway is reduced from 287 to 255 kg per 1 ton of isoprene. Gumming and plugging of the equipment with resins do not occur.

Example 2

The process is carried out analogously to example 1, however, there are the following differences.

220 kg / h of distillate are distilled off on the runway distillation column, the proportion of which is 20% of the column feed. The amount of bottoms in the column is 880 kg / h.

Runway distillation distillate in an amount of 220 kg / h is fed to isoprene for decomposition together with DMD, i.e., the selected distillate is decomposed at a temperature of 160 ° C, a pressure of 0.9 MPa

As a result of the process with liquid-phase decomposition of the selected runway distillate, the total amount of isoprene obtained from the same amount of feedstock increases to 3920 kg / h or by 2.3%. The amount of waste in the form of a runway is reduced to 224 kg per 1 ton of isoprene. Gumming and plugging of the equipment with resins do not occur.

Example 3

The process is carried out analogously to example 1, however, there are the following differences.

On the runway distillation column, 330 kg / h of distillate is distilled off, the proportion of which is 30% of the column feed. The amount of bottoms in the column is 770 kg / h.

A part of the distillate in an amount of 100 kg / h is sent for decomposition into the reactor together with DMD.

Another part of the distillate in an amount of 230 kg / h is fed for decomposition into isoprene in a separate reactor. The reactor is maintained at a temperature of 180 ° C and a pressure of 1.3 MPa.

As a result of the process with liquid-phase decomposition of these distilled parts of the runway mixture, the total amount of isoprene obtained from the same amount of feedstock increases to 3955 kg / h or by 3.3%. At the same time, the amount of process waste is reduced to 195 kg per 1 ton of isoprene. Gumming and plugging of the equipment with resins do not occur.

Example 4

The process is carried out analogously to example 1, however, there are the following differences.

550 kg / h of distillate are distilled off on the runway distillation column, the proportion of which is 50% of the column feed. The amount of VAT residue is 550 kg / h.

A portion of the distillate in an amount of 150 kg / h is sent for decomposition into the reactor together with DMD.

Another part of the distillate in an amount of 400 kg / h is fed for decomposition into isoprene in a separate reactor. The reactor is maintained at a temperature of 200 ° C and a pressure of 1.7 MPa.

As a result of the process with liquid-phase decomposition of these distilled parts of the runway mixture, the total amount of isoprene obtained from the same amount of feedstock increases to 4015 kg / h or 4.8%. The amount of process waste is reduced to 137 kg per 1 ton of isoprene. Gumming and plugging of the equipment with resins do not occur.

The indicators of examples of the method are summarized in table.

Table Indicators of the process of obtaining isoprene Example 1 Example 2 Example 3 Example 4 1. Supply of fraction C4 to the DMD synthesis reactor, kg / h 10100 10100 10100 10100 2. The concentration of isobutylene in fractions With ₄ ,% wt. 41.3 41.3 41.3 41.3 3. The supply of formaldehyde charge in the synthesis reactor DMD, kg / h 14800 14800 14800 14800 4. The content in the formaldehyde mixture,% wt .: - formaldehyde 26.5 26.5 26.5 26.5 - oxalic acid 1,2 1,2 1,2 1,2 - phosphoric acid 1.8 1.8 1.8 1.8 5. Indicators for the synthesis of DMD: - temperature in the reactor, ° C one hundred one hundred one hundred one hundred - pressure in the reactor, MPa 2.0 2.0 2.0 2.0 - formaldehyde conversion,% 81.6 81.6 81.6 81.6 - isobutylene conversion,% 80.7 80.7 80.7 80.7 - production of DMD, kg / h 4860 4860 4860 4860 - runway production, kg / h 1100 1100 1100 1100 6. Indicators for the decomposition of DMD in isoprene: - temperature in the reactor, ° C 160 160 160 160 - pressure in the reactor, MPa 0.9 0.9 0.9 0.9 - the concentration of phosphoric acid in an aqueous solution,% wt. 5.8 5.8 5.8 5.8 - isoprene production, kg / h 3830 3830 3830 3830 7. Performance indicators runway distillation columns: - amount of distillate, kg / h 110 220 330 550 - the proportion of distillate from the power of the column,% wt. 10 twenty thirty fifty - the amount of bottoms, kg / h 990 880 770 550 8. Indicators for the decomposition of distillate
Isoprene runway distillation columns:
- runway distillate feed for decomposition, total, kg / h

110

220

330

550 - including kg / h 110 - for decomposition into a separate reactor ^*) 220 - for decomposition together with DMD ^**) 100 - for decomposition together with DMD ^**) ; 230 - for decomposition into a separate reactor ^*) 150 - for decomposition together with DMD ^**) ; 400 - for decomposition into a separate reactor ^*) - temperature in the reactor ^*) , ° С 150 ^*) 160 ^**) 180 ^*) 200 ^*) - pressure in the reactor *), MPa 0.6 ^*) 0.9 ^**) 1.3 ^*) 1.7 ^*) - the concentration of phosphoric acid in an aqueous solution,% wt. 5.8 5.8 5.8 5.8 - additional production of isoprene due to decomposition of the runway, kg / h fifty 90 125 185 9. The total amount of isoprene obtained in the process, kg / h 3880 3920 3955 4015 10. The increase in the production of isoprene due to decomposition
runway distillate,% 1.3 2,3 3.3 4.8 11. The amount of process waste in the form of the bottom residue of the runway distillation column per 1 ton of isoprene obtained, kg 255 224 195 137

Claims (3)

1. A method of producing isoprene, including liquid-phase condensation of isobutylene in the form of an isobutylene-containing fraction C ₄ with an aqueous solution of formaldehyde in the presence of an acid catalyst at elevated temperature and pressure to form 4,4-dimethyl-1,3-dioxane and a mixture of high-boiling by-products, followed by liquid-phase decomposition of the obtained 4,4-dimethyl-1,3-dioxane in isoprene in the presence of trimethylcarbinol and / or isobutylene and an aqueous solution of an acid catalyst at elevated temperature and pressure, characterized in that 4.4-dimethyl-1,3-dioxane and a mixture of high-boiling by-products are distilled from the condensation products, which are then distilled on a vacuum distillation column to select distillate in the amount of 10-50 wt.% from the column feed, followed by supplying the selected distillate to liquid phase decomposition into isoprene in the presence of trimethylcarbinol and / or isobutylene and an aqueous solution of an acid catalyst at a temperature of 150-200 ° C, a pressure of 0.6-1.7 MPa together with 4,4-dimethyl-1,3-dioxane and / or separate reactor. 2. The method according to claim 1, characterized in that the condensation of isobutylene with formaldehyde is carried out at a temperature of 80-110 ° C and a pressure of 1.3-2.5 MPa. 3. The method according to claim 1, characterized in that the decomposition of 4,4-dimethyl-1,3-dioxane is carried out at a temperature of 150-200 ° C and a pressure of 0.6-1.7 MPa.