Isoprene production process

FIELD: industrial organic synthesis.

SUBSTANCE: first stage of the process comprises synthesis of 4,4-dimethyl-1,3-dioxan via isobutylene/formaldehyde condensation in presence of acid catalyst at 80-100ºC and pressure 1.6-2.0 MPa. Product and high-boiling by-product mixture are isolated from oil layer of reaction mixture. 4,4-Dimethyl-1,3-dioxan is then decomposed on calcium phosphate catalyst at 290-380°C and pressure 0.12-0.16 MPa in presence of water steam. Contact gas is further processed to produce isoprene. High-boiling by-product mixture is distilled on two in series connected vacuum rectification columns. On the first column, 60-70% of distillate is recovered based on the weight of feed. Second distillation on the second column gives second distillate (75-90%) and bottom product, which is recycled into 4,4-dimethyl-1,3-dioxan synthesis zone. Second-column distillate is decomposed into isoprene on ceramic filling at 400-450°C and pressure 0.12-0.16 MPa in presence of water steam supplied at (2-5):1 weight ratio to high-boiling by-product mixture. Contact gas obtained after decomposition of this mixture is processed jointly with contact gas obtained after decomposition of dimethyldioxan.

EFFECT: reduced amount of process waste and increased production of isoprene without increase in consumed raw material.

3 cl, 1 dwg, 1 tbl, 4 ex

 

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

Isoprene is the monomer upon receipt composition of polyisoprene rubber, butyl rubber, isoprostanes polymers, which are used in the tire industry and in the manufacture of rubber products.

A known method of producing isoprene comprising a stage of liquid-phase synthesis of 4,4-dimethyl-1,3-dioxane (DMD) by the condensation of formaldehyde in aqueous solution with isobutylene in the form isobutylester fraction4in the presence as catalyst of sulfuric acid at a temperature of 85-95°C, pressure of 1.8-2.0 MPa, with separation of the reaction mass in water and oil layers. From the oil layer by distillation allocate DMD and a mixture of high-boiling by-products (WFP). The aqueous layer containing sulfuric acid and WFP, neutralized with alkali, and then evaporated. The residue after parki containing salt and WFP, is sent to waste water production. Received DMD further subjected to heterogeneous catalytic decomposition in the isoprene in the calcium phosphate catalyst at a temperature of 370-390°in the presence of water vapor. Contact the gas after decomposition of DME cooled, separated into water and hydrocarbon layers, from uglev the fat layer by distillation emit isoprene [OGO S. Kaliev and Idlis G.S. isoprene Production. - L.: Chemistry, 1973, p.48-63].

The disadvantages of this method are the availability of wastewater contaminated with salts and WFP, a significant amount of waste - runway, which is not used in the process.

A known method of producing isoprene comprising a stage of liquid-phase synthesis DMD condensation of formaldehyde in aqueous solution with isobutylene in the form isobutylester fraction4in the presence as catalyst of sulfuric acid at a temperature of 65-75°C, pressure of 1.0-1.2 MPa, with separation of the reaction mass in water and oil layers, with parcoy water layer, adding to the residue after parki source of an aqueous solution of formaldehyde and recycling the resulting mixture to a zone of condensation of formaldehyde with isobutylene, with the separation by distillation of the oil layer DMD and a mixture of the runway. Received DMD further subjected to heterogeneous catalytic decomposition in the isoprene in the phosphoric acid catalyst on the carrier at a temperature of 250-300°in the presence of water vapor. Contact the gas after decomposition of DME cooled, separated into water and hydrocarbon layers, from the hydrocarbon layer by distillation emit isoprene [OGO S. Kaliev and Idlis G.S. isoprene Production. - L.: Chemistry, 1973, p.64-70].

The disadvantages of this method are the formation of resins caused behold the Noah acid when Parke water layer, corrosion of the equipment in the presence of sulfuric acid, the complexity of the operation of the reactor decomposition DMD with the used catalyst, a significant amount of waste.

Closest to the claimed is known a method of producing isoprene comprising a stage of liquid-phase synthesis DMD condensation of formaldehyde in aqueous solution with isobutylene in the form isobutylester fraction4in the presence of oxalic acid as a catalyst at a temperature of 80-100°C, pressure of 1.6-2.0 MPa, with separation of the reaction mass in water and oil layers, with parcoy water layer, adding to the residue after parki source of an aqueous solution of formaldehyde and recycling the resulting mixture to a zone of condensation of formaldehyde with isobutylene, with the separation by distillation of the oil layer DMD and a mixture of the runway, including subsequent phase heterogeneous catalytic decomposition of DMD in the isoprene in the calcium phosphate catalyst at a temperature of 290-380°C, the pressure of 0.12 to 0.16 MPa in the presence of water vapor, cooling and separation of the contact of the gas after decomposition of the DMD on the water and hydrocarbon layers, emitting isoprene by distillation of the hydrocarbon layer [Kirpichnikov P.A., Beresnev V.V., Popova L. Album technological schemes the main production of the synthetic rubber industry. - L.:Chem which I 1986, p.36-53].

The disadvantages of the above method is the formation of significant amounts of waste that are not used in the process (number of runways is 440-460 kg per 1 t of the resulting isoprene), low production of isoprene from the feedstock - formaldehyde and isobutylene.

The objective of the proposed method is to reduce the amount of waste process for the production of isoprene and the increased production of isoprene from the same quantities of raw materials.

This task is solved by a method of producing isoprene comprising a stage of liquid-phase synthesis DMD condensation of formaldehyde in aqueous solution with isobutylene in the form isobutylester fraction4in the presence of acid catalyst at a temperature of 80-100°C, pressure of 1.6-2.0 MPa, with separation of the reaction mass in water and oil layers, with parcoy water layer, adding to the residue after parki source of an aqueous solution of formaldehyde and recycling the resulting mixture to a zone of condensation of formaldehyde with isobutylene, with the separation by distillation of the oil layer DMD and a mixture of the runway, including subsequent phase heterogeneous catalytic decomposition of DMD in the isoprene in the calcium phosphate catalyst at a temperature of 290-380°C, the pressure of 0.12 to 0.16 MPa in the presence of water vapor, with cooling and separation of the contact is about gas after decomposition of the DMD on the water and hydrocarbon layers, with the release of isoprene by distillation of the hydrocarbon layer, and the mixture runway, obtained at the stage of synthesis of DME, is distilled in two series-connected vacuum distillation columns, first column, then the resulting distillate in the amount of 60-70 wt.% from feeding the first column is distilled in a second column, where deduce the distillate in the amount of 75-90 wt.% from the power supply and the VAT residue, then the distillate of the second column is directed to heterogeneous catalytic decomposition of isoprene on the ceramic nozzle at a temperature of 400-450°C, the pressure of 0.12 to 0.16 MPa in the presence of water vapor, supplied in a mass ratio to the runway (2-5):1, contact the gas after decomposition of the runway contained in the distillate of the second column, is processed together with the contact gas after decomposition of the DMD, and the VAT residue of the second column refer to the zone of condensation of formaldehyde with isobutylene.

As a variant of the proposed method lies in the fact that, as the acid catalyst for the synthesis DMD use oxalic acid, phosphoric acid or a mixture of these acids.

Also as a variant of the proposed method lies in the fact that in the first distillation column distillation WFP carried out under the following conditions:

the temperature of the top,°155-170

the temperature of the cube°190-200

pressure, the PA 0,015-0,03

the number of plates 22-28

reflux the number of 1-1,5,

and on the second column under the following conditions:

the temperature of the top,°135-155

the temperature of the cube°165-180

the pressure of 0.002 MPa-0,007

the number of plates 22-28

reflux the number of 1-1,5.

Distinctive features of the prototype characteristics of the proposed method are the following:

the mixture runway, obtained at the stage of synthesis of DME, is distilled in two stages by two series-connected vacuum distillation columns;

after the first column distillation runway get the distillate in the amount of 60-70 wt.% from power, the resulting distillate is then distilled in a second column, where deduce the distillate in the amount of 75-90 wt.% from the power supply and the VAT residue;

WFP contained in the distillate of the second column, sent for heterogeneous catalytic decomposition of isoprene on the ceramic nozzle at a temperature of 400-450°C, the pressure of 0.12 to 0.16 MPa in the presence of water vapor, supplied in a mass ratio to the runway (2-5):1;

contact the gas after decomposition of the runway processed together with the contact gas after decomposition DMD;

VAT residue of the second distillation columns runway served in the zone of condensation of formaldehyde with isobutylene.

In the proposed method, the waste of the production of isoprene is VAT residue of the first distillation column of the distillation of the runway. The OS is the real number of runways, formed during the synthesis of DME, used in the process for production of isoprene.

VAT residue of the first distillation column distillation runway is a mixture of the most high molecular weight and high boiling components runway - dioxane derivatives of alcohols, polyols, polymers. Of these compounds under these conditions, heterogeneous catalytic decomposition yields only coke and tar, which lead to rapid deactivation of the catalyst. Even small amounts of these compounds reduced the activity, increase the coke formation and impair the catalyst for the decomposition of the runway. In connection with this decomposition directly the whole mass of the runway is almost difficult task.

When using distillation runway only one distillation column number of the distillate, containing components of the mixture runway, diminish the work of catalyst decomposition is only 30-35 wt.% from the supplied power.

Distillation of the runway in two stages allows to increase the number of distillate containing no components of the mixture runway, diminish the work of catalyst decomposition. In turn, this helps reduce the amount of waste process for the production of isoprene. The decrease in the share of distillate is less than 60 wt.% on the first column and less than 75 wt.% in the second column does not allow possible measures in order to reduce the amount of waste process as distills not all components runway useful from the point of view of their subsequent decomposition into isoprene. The increase in the proportion of distillate more than 70 wt.% on the first column and more than 90 wt.% in the second column leads to an increased content of high molecular weight components of the mixture runway in the distillate of the second column, which leads to deterioration of the catalyst in the decomposition of the runway.

Carrying out the distillation of the runway under vacuum (under reduced pressure) allows to reduce the operating temperature of the distillation column and to prevent resinification runway during distillation.

Used as catalyst for the decomposition of the ceramic nozzle provides sufficient depth transformation of the runway and adequate yield of isoprene. Water vapor supplied into the zone of decomposition in the mass ratio to the runway (2-5):1, is used as a coolant to reduce coke formation, maintaining the stability of the catalytic activity and to enhance the performance of the catalyst. When the reduction ratio less than 2:1 reduced yield of isoprene and increases the coke formation. The increase in the ratio more than 5:1 is impractical due to increased energy consumption.

Decreasing the decomposition temperature of less than 400°With reduced depth transformation of the runway, decreases the yield of isoprene and reduces the production of isoprene.

If temperatures rise more than 40° With reduced yield of isoprene and increases the coke formation.

Association contact gas after decomposition of the runway contact with the gas after decomposition DMD is facilitated by carrying out contact as decomposition of DME, and the runway under the same pressure. United contact the gas is further processed together, which simplifies the process.

As residue of the second distillation column distillation runway contains mostly dioxane alcohols. The submission of this VAT residue in the synthesis zone DMD allows you to get more number of DMD and accordingly to increase the production of isoprene.

The use of the above techniques, the proposed method is compared with the prototype allows to reduce the amount of waste process to 120-160 kg per 1 t of isoprene, to increase the production of isoprene by 9-10 wt.% from the same quantity of raw materials.

The method was verified experimentally in an industrial environment. The use of the method is illustrated by the flow chart of the process and examples, which do not exhaust all possible variants of realization of the invention, and possibly the use of other technical solutions, while respecting the essence of the invention set forth in the claims and the description.

The method is carried out by represented in the drawing process flow process is as follows.

In reactor unit 3, consisting of five tubular reactors, serves isobutane-isobutilene fraction from line 1 after the extractor 10 and formaldehyde mixture, line 2 from the mixer 13. In the reactor unit 3 carry out the synthesis of DME at a temperature of 80-100°C, pressure of 1.6-2.0 MPa. Under these conditions, the reaction mixture is in a liquid state. Formaldehyde mixture is an aqueous solution containing formaldehyde and an acid catalyst is a mixture of oxalic and phosphoric acids. In reactor unit 3 also serves recycle streams: MLA on line 31 from a bottom part of the distillation column 29 and trimethylquinoline faction on line 21 of the distillation column 20.

From the reaction unit 3, the reaction mass output line 4 in the tank 5, where the reaction mass is separated into water and oil layers.

The aqueous layer from the settling tank 5 is served by line 6 in column of parki 7. VAT residue columns of parki 7, containing an acid catalyst, serves on line 12 into the mixer 13 for the preparation of formaldehyde mixture. In the mixer 13 also serves fresh formalin on line 14 installation oxidation of methanol and return formalin on line 16 of column strengthening of formaldehyde 52.

The distillate of the column of parki 7, which is an aqueous solution containing formaldehyde, organic products (DME, trimethylarsine, prima who and WFP), line 9 is applied to the extractor 10. In the extractor 10 extracts from the distillate of parki organic products using fresh isobutane-isobutilene fraction, which is fed into the extractor 10 through line 11. After the extractor 10 isobutane-isobutilene faction on line 1 is directed to the synthesis of DMD in reactor unit 3. From the bottom of the extractor 10 output diluted aqueous solution of formaldehyde and then line 15 is fed to the column strengthening of formaldehyde 52.

The oil layer from the settling tank 5 through line 8 after pre-wash water (not shown) served in the distillation column 17, where the distilled waste isobutane-isobutilene fraction (neprevyshenie hydrocarbons), which are sent by line 18 for further processing known methods.

Cubic liquid of the distillation column 17 through line 19 serves in the distillation column 20, where distilled trimethylquinoline fraction, which is recycled through line 21 into reactor unit 3.

Cubic liquid of the distillation column 20 through line 22 is sent to a distillation column 23 where the DMD is distilled off from the mixture of the runway. Clubbed DMD-distillate of the column 23 output line 24, attached to it is delivered through a line 51 return DMD (neprevyshenie DMD after decomposition in isoprene) and the combined stream DMD on line 54 serves is as heterogeneous catalytic decomposition of isoprene in the reactor 34.

In reactors 34 (two alternately operating sectional reactor) conduct the decomposition of the DMD in the isoprene in the calcium phosphate catalyst at a temperature of 290-380°C, the pressure of 0.12 to 0.16 MPa in the presence of water vapor, which is fed to the reactor through line 35. Water vapor is served in a mass ratio to the DMD (of 1.5-1.9):1.

The resulting contact of the gas after the reactors 34 output line 36, then through line 38 for processing, which includes the following basic operations.

Contact the gas line 38 is fed to the cooling and condensation of 39 (HRSG, water cooler, air cooler, washing scrubber, ammonia refrigerator). The resulting liquid line 40 is directed into the sump 41, where it is separated into water and hydrocarbon layers.

The aqueous layer from the settling tank 41 is directed through line 42 into the distillation column 43, where the distilled light organic matter (DMD, unsaturated alcohols, and other), which is along the line 44 returns to the sump 41. Cubic liquid column 43, representing a diluted aqueous solution of formaldehyde, line 45 serves in a distillation column strengthening of formaldehyde 52. In column 52 serves also dilute aqueous solution of formaldehyde on line 15 after the extractor 10. From the top of the column 52 distillate - concentrated aqueous solution of formaldehyde (return formalin), the cat is who on the line 16 is sent to the mixer 13 for the preparation of formaldehyde mixture. Cubic liquid column 52 (vaselina water) in line 53 is sent to the wastewater process.

The hydrocarbon layer after sedimentation tank 41 through line 46 serves to install the isolation and purification of isoprene 47. After conducting transactions involving several consecutive rectificate, with installation 47 get targeted product - isoprene on line 48. Isoprene then used to obtain the composition of polyisoprene rubber.

In addition to isoprene with installation 47 get return isobutylene line 49, which is attached to the fresh isobutane-isobutilene fraction, receive return DMD on line 51, which together with the main stream DMD served then by line 54 to the decomposition of isoprene, and the by-products formed by the decomposition of DME, which lines 50 are sent to the warehouse.

The mixture of the runway from the bottom of column 23 through line 25 serves to distillation column 26, where the first stage of distillation of the runway. In column 26 supports the following modes:

the temperature of the top,°155-170

the temperature of the cube°190-200

pressure, MPa 0,015-0,03

the number of plates 22-28

reflux the number of 1-1,5.

From the top of the column 26 distillate in the amount of 60-70 wt.% the applied power, then this distillate in line 27 is sent to distillation column 29, where the second stage of distillation of the runway.

VAT residue columns 26 are the two which is the departure process for the synthesis of isoprene. This VAT residue assign line 28 and then disposed of by known methods.

In a distillation column 29 supports the following modes:

the temperature of the top,°135-155

the temperature of the cube°165-180

the pressure of 0.002 MPa-0,007

the number of plates 22-28

reflux the number of 1-1,5.

From the top of the column 29 distillate in the amount of 75-90 wt.% the applied power, then this distillate through line 30 serves on heterogeneous catalytic decomposition of isoprene in the reactor 32.

VAT residue column 29 is directed through line 31 to the stage of synthesis of DMD in reactor unit 3.

In reactors 32 (two alternately operating sectional reactor) conduct the decomposition of the runway, which are contained in the distillate of the column 29, isoprene. The decomposition is performed on the ceramic nozzle placed on the shelves of the reactor, at a temperature of 400-450°C, the pressure of 0.12 to 0.16 MPa in the presence of water vapor, which is fed to the reactor through line 33. Water vapor is served in a mass ratio to the runway (2-5):1.

The resulting contact of the gas after the reactors 32 output lines 37, then combine with the contact gas after the reactors 34 decomposition DMD coming on line 36. The combined stream contact gas then serves on line 38 at the joint processing described above.

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

How should the duty to regulate in the table data, the proposed method allows to reduce the number of runway - waste process for the production of isoprene to 120-160 kg per 1 t derived isoprene. In addition, compared with the known method the proposed method can improve the yield of isoprene on 9-10 wt.% without increasing the consumption of raw materials.

1. A method of producing isoprene comprising a stage of liquid-phase synthesis of 4,4-dimethyl-1,3-dioxane condensation of formaldehyde in aqueous solution with isobutylene in the form isobutylester fraction4in the presence of acid catalyst at a temperature of 80-100°C, pressure of 1.6-2.0 MPa with the separation of the reaction mass in water and oil layers, with parcoy water layer, adding to the residue after parki source of an aqueous solution of formaldehyde and recycling the resulting mixture to a zone of condensation of formaldehyde with isobutylene, with the separation by distillation of the oil layer 4,4-dimethyl-1,3-dioxane and a mixture of high-boiling by-products, including the next phase heterogeneous catalytic decomposition of 4,4-dimethyl-1,3-dioxane in the isoprene in the calcium phosphate catalyst at a temperature of 290-380°With, the pressure of 0.12 to 0.16 MPa in the presence of water vapor by cooling and separation of the contact of the gas after decomposition of 4,4-dimethyl-1,3-is Oksana water and hydrocarbon layers, with the release of isoprene by distillation of the hydrocarbon layer, characterized in that the mixture of high-boiling by-products obtained at the stage of synthesis of 4,4-dimethyl-1,3-dioxane, is distilled in two series-connected vacuum distillation columns, first column, then the resulting distillate in the amount of 60-70 wt.% from feeding the first column is distilled in a second column, where deduce the distillate in the amount of 75-90 wt.% from the power supply and the VAT residue, then the distillate of the second column is directed to heterogeneous catalytic decomposition of isoprene on the ceramic nozzle at a temperature of 400-450°C, the pressure of 0.12 to 0.16 MPa in the presence of water vapor supplied to the mass ratio of the high-boiling by-products (2-5):1, contact the gas after decomposition of high-boiling by-products contained in the distillate of the second column, is processed together with the contact gas after decomposition of 4,4-dimethyl-1,3-dioxane, and the VAT residue of the second column refer to the zone of condensation of formaldehyde with isobutylene.

2. The method according to claim 1, characterized in that as the acid catalyst for the synthesis of 4,4-dimethyl-1,3-dioxane use oxalic acid, phosphoric acid or a mixture of these acids.

3. The method according to claim 1, characterized in that the distillation of high-boiling by-products on the first of the distillation column is carried out at the following conditions:

The temperature of the top, °155-170

The temperature of the cube °190-200

Pressure, MPa 0,015-0,03

The number of plates 22-28

Reflux the number of 1-1,5

and on the second column under the following conditions:

The temperature of the top, °135-155

The temperature of the cube °165-180

The pressure of 0.002 MPa-0,007

The number of plates 22-28

Reflux the number of 1-1,5



 

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SUBSTANCE: invention relates to production of isoprene for use in synthesis of isoprene rubber and butyl rubber used in tire industry and manufacture of general mechanical rubber goods. In the method of invention, isoprene is obtained by decomposition of 4,4-dimethyl-1,3-dioxan on calcium phosphate catalyst comprising synthesis of 4,4-dimethyl-1,3-dioxan by interaction of isobutylene-containing C4 fraction with aqueous formaldehyde solution in presence of acid catalyst to form reaction medium composed of oil and water layers followed by separation of oil layer into unreacted C4-hydrocarbons and 4,4-dimethyl-1,3-dioxan by rectification leaving bottom residue containing dioxan alcohols (high-boiling dioxan alcohols to be processed into additional product), separation of water layer, condensation of contact gas, and recovery of desired isoprene. Low-boiling part of hydrocarbons distilled off in processing of bottom residue of 4,4-dimethyl-1,3-dioxan rectification is separated and thus obtained lower product is discharged as a mixture of high-boiling dioxan alcohols, which constitute additional desired product, whereas upper product is combined with formaldehyde-containing blend fed into 4,4-dimethyl-1,3-dioxan synthesis zone. Acid catalyst utilized in synthesis of 4,4-dimethyl-1,3-dioxan is mixture of oxalic and phosphoric acids at weight ratio between 2:1 and 1:1, whereas summary concentration of acids in formaldehyde-containing blend is maintained between 1.5 and 2.5 wt %. Remaining high-boiling fraction of hydrocarbons taken off in processing of bottom residue of 4,4-dimethyl-1,3-dioxan rectification, which are mixture of heavy residue and high-boiling alcohols, are taken off in the form of by-product.

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FIELD: industrial organic synthesis.

SUBSTANCE: invention relates to production of isoprene for use in synthesis of isoprene rubber, butyl rubber, and isoprene-containing polymers used in tire industry and manufacture of general mechanical rubber goods. In the method of invention, isoprene is obtained by decomposition of 4,4-dimethyl-1,3-dioxan on calcium phosphate catalyst comprising synthesis of 4,4-dimethyl-1,3-dioxan by interaction of isobutylene-containing C4 fraction with formaldehyde-containing blend based on methanol-free formalin obtained by oxidation of methanol followed by rectification of formalin, accomplished at elevated temperature and pressure in presence of acid catalyst followed by separation of reaction medium into oil and water layers including extraction of organic products from water layer, isolation of 4,4-dimethyl-1,3-dioxan, unreacted C4-hydrocarbons, and high-boiling by-products from oil layer, condensation of 4,4-dimethyl-1,3-dioxan decomposition contact gas and isolating from condensate isoprene, unreacted 4,4-dimethyl-1,3-dioxan, recycling isobutylene and formaldehyde-containing water, performing also withdrawal of extracted water layer to be vacuum evaporated followed by sending evaporated water layer to preparation of formaldehyde-containing blend. Evaporation of extracted water layer containing acid catalyst is carried out at temperature of boiler wall in rectification column 80-105°C and residual pressure 0.015-0.025 MPa. Distillate is mixed with above-indicated formaldehyde-containing water and resulting mixture is subjected to two-step concentration of formaldehyde. Second-step distillate, namely recycle methanol, is sent to oxidation zone. Bottom residues of the second step of formaldehyde concentration and those of the extracted water layer evaporation are combined with methanol-free formaldehyde and acid catalyst continuously supplied as replenishment, after which used as formaldehyde-containing blend in the 4,4-dimethyl-1,3-dioxan synthesis. Concentration of acid catalyst is maintained between 1.60 and 1.75 wt %.

EFFECT: increased productivity and reduced material and power consumption.

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FIELD: industrial organic synthesis.

SUBSTANCE: invention relates to production of isoprene for use in synthesis of isoprene rubber and butyl rubber used in tire industry and manufacture of general mechanical rubber goods. In the method of invention, isoprene is obtained by decomposition of 4,4-dimethyl-1,3-dioxan in reactors caused by interaction of isobutylene-containing C4 fraction with aqueous formaldehyde solution (prepared by oxidation of methanol) at elevated temperature and pressure in presence of acid catalyst to form reaction medium composed of oil and water layers followed by separation of oil layer into unreacted C4-hydrocarbons and 4,4-dimethyl-1,3-dioxan by rectification leaving bottom residue containing dioxan alcohols (high-boiling by-products to be processed into additional product), separation of water layer, condensation of 4,4-dimethyl-1,3-dioxan decomposition contact gas, and recovery of desired isoprene by rectification. Bottom residue is processed at residual pressure 0.002-0.010 MPa, elevated reflux ratio equal to 2.0-5.0, and continuous circulation of bottom fluid under lower plate of rectification column at weight ratio of circulating bottom fluid as additional product to bottom residue of 4,4-dimethyl-1,3-dioxan rectification equal to 20-35. Column distillate - low-boiling by-products are sent to 4,4-dimethyl-1,3-dioxan synthesis reactors or subjected to catalytic decomposition, separately or jointly with 4,4-dimethyl-1,3-dioxan.

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FIELD: industrial organic synthesis.

SUBSTANCE: invention relates to production of isoprene for use in synthesis of isoprene rubber, butyl rubber, and isoprene-containing polymers used in tire industry and manufacture of general mechanical rubber goods. In the method of invention, isoprene is obtained by decomposition of 4,4-dimethyl-1,3-dioxan on calcium phosphate catalyst comprising synthesis of 4,4-dimethyl-1,3-dioxan by interaction of isobutylene-containing C4 fraction with formaldehyde-containing blend based on methanol-free formalin obtained by oxidation of methanol followed by rectification of formalin, accomplished at elevated temperature and pressure in presence of acid catalyst followed by separation of reaction medium into oil and water layers including extraction of organic products from water layer, isolation of 4,4-dimethyl-1,3-dioxan, unreacted C4-hydrocarbons, and high-boiling by-products from oil layer, condensation of 4,4-dimethyl-1,3-dioxan decomposition contact gas and isolating from condensate isoprene, unreacted 4,4-dimethyl-1,3-dioxan, recycling isobutylene and formaldehyde-containing water, performing also withdrawal of extracted water layer to be vacuum evaporated followed by sending evaporated water layer to preparation of formaldehyde-containing blend. Evaporation of extracted water layer containing acid catalyst is carried out at temperature of boiler wall in rectification column 80-105°C and residual pressure 0.015-0.025 MPa. Distillate is mixed with above-indicated formaldehyde-containing water and resulting mixture is subjected to two-step concentration of formaldehyde. Second-step distillate, namely recycle methanol, is sent to oxidation zone. Bottom residues of the second step of formaldehyde concentration and those of the extracted water layer evaporation are combined with methanol-free formaldehyde and acid catalyst continuously supplied as replenishment, after which used as formaldehyde-containing blend in the 4,4-dimethyl-1,3-dioxan synthesis. Concentration of acid catalyst is maintained between 1.60 and 1.75 wt %.

EFFECT: increased productivity and reduced material and power consumption.

2 cl, 1 dwg, 5 ex

FIELD: industrial organic synthesis.

SUBSTANCE: invention relates to production of isoprene for use in synthesis of isoprene rubber and butyl rubber used in tire industry and manufacture of general mechanical rubber goods. In the method of invention, isoprene is obtained by decomposition of 4,4-dimethyl-1,3-dioxan on calcium phosphate catalyst comprising synthesis of 4,4-dimethyl-1,3-dioxan by interaction of isobutylene-containing C4 fraction with aqueous formaldehyde solution in presence of acid catalyst to form reaction medium composed of oil and water layers followed by separation of oil layer into unreacted C4-hydrocarbons and 4,4-dimethyl-1,3-dioxan by rectification leaving bottom residue containing dioxan alcohols (high-boiling dioxan alcohols to be processed into additional product), separation of water layer, condensation of contact gas, and recovery of desired isoprene. Low-boiling part of hydrocarbons distilled off in processing of bottom residue of 4,4-dimethyl-1,3-dioxan rectification is separated and thus obtained lower product is discharged as a mixture of high-boiling dioxan alcohols, which constitute additional desired product, whereas upper product is combined with formaldehyde-containing blend fed into 4,4-dimethyl-1,3-dioxan synthesis zone. Acid catalyst utilized in synthesis of 4,4-dimethyl-1,3-dioxan is mixture of oxalic and phosphoric acids at weight ratio between 2:1 and 1:1, whereas summary concentration of acids in formaldehyde-containing blend is maintained between 1.5 and 2.5 wt %. Remaining high-boiling fraction of hydrocarbons taken off in processing of bottom residue of 4,4-dimethyl-1,3-dioxan rectification, which are mixture of heavy residue and high-boiling alcohols, are taken off in the form of by-product.

EFFECT: enhanced isoprene production efficiency and reduced corrosion of technique, clogging with salts and tars, produced useful dioxan alcohols, and reduced specific consumption of raw materials.

1 dwg, 3 ex

FIELD: hydrogenation-dehydrogenation catalysts.

SUBSTANCE: invention relates to catalysts used in isoamylenes-into-isoprene dehydrogenation process and contains, wt %: iron oxide 62-75.4, potassium carbonate 12-21.5, chromium oxide 1-3, potassium hydroxide 0.5-2.5, sulfur 0.1-2.0, ammonium nitrate 0.1-2.0, silicon dioxide 1-5, calcium carbonate 1-5, and cerium nitrate 1-3.

EFFECT: increased mechanical strength, resistance to saturated steam and moisture, and stability during long-time operation.

3 ex

FIELD: industrial organic synthesis.

SUBSTANCE: first stage of the process comprises synthesis of 4,4-dimethyl-1,3-dioxan via isobutylene/formaldehyde condensation in presence of acid catalyst at 80-100ºC and pressure 1.6-2.0 MPa. Product and high-boiling by-product mixture are isolated from oil layer of reaction mixture. 4,4-Dimethyl-1,3-dioxan is then decomposed on calcium phosphate catalyst at 290-380°C and pressure 0.12-0.16 MPa in presence of water steam. Contact gas is further processed to produce isoprene. High-boiling by-product mixture is distilled on two in series connected vacuum rectification columns. On the first column, 60-70% of distillate is recovered based on the weight of feed. Second distillation on the second column gives second distillate (75-90%) and bottom product, which is recycled into 4,4-dimethyl-1,3-dioxan synthesis zone. Second-column distillate is decomposed into isoprene on ceramic filling at 400-450°C and pressure 0.12-0.16 MPa in presence of water steam supplied at (2-5):1 weight ratio to high-boiling by-product mixture. Contact gas obtained after decomposition of this mixture is processed jointly with contact gas obtained after decomposition of dimethyldioxan.

EFFECT: reduced amount of process waste and increased production of isoprene without increase in consumed raw material.

3 cl, 1 dwg, 1 tbl, 4 ex

FIELD: industrial organic synthesis.

SUBSTANCE: first stage of the process comprises synthesis of 4,4-dimethyl-1,3-dioxan via isobutylene/formaldehyde condensation in presence of acid catalyst at 80-100ºC and pressure 1.6-2.0 MPa. Product and high-boiling by-product mixture are isolated from oil layer of reaction mixture. 4,4-Dimethyl-1,3-dioxan is then decomposed on calcium phosphate catalyst at 290-380ºC and pressure 0.12-0.16 MPa in presence of water steam. Contact gas is further processed to produce isoprene. High-boiling by-product mixture is distilled on vacuum rectification column to give distillate in amount 30-35% of the weight of feed. Distillate is passed to heterogeneous-phase catalytic decomposition into isoprene on ceramic filling at 400-450°C and pressure 0.12-0.16 MPa in presence of water steam supplied at (2-5):1 weight ratio to high-boiling by-product mixture. Contact gas obtained after decomposition of this mixture is processed jointly with contact gas obtained after decomposition of dimethyldioxan.

EFFECT: reduced amount of process waste and increased production of isoprene without increase in consumed raw material.

3 cl, 1 tbl, 4 ex

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to technology for preparing isoprene that is a monomer in synthesis of polyisoprene, butyl rubber, isoprene-containing polymers used in tire industry and rubber-technical articles and can be used in petrochemical industry. Proposed method for preparing isoprene involves decomposition of 4,4-dimethyl-1,3-dioxane on calcium-phosphate catalyst and involves synthesis of 4,4-dimethyl-1,3-dioxane by interaction of isobutylene-containing C4-fraction with formaldehyde aqueous solution in the presence of acid catalyst to form reaction mass consisting of oily and aqueous layers. Then oily layer is separated to isolate unreacted C4-hydrocarbons and 4,4-dimethyl-1,3-dioxane by rectification and removal of vat residue containing high-boiling dioxane alcohols and other by-side products, separation by rectification and isolation of floating reagent-oxal and absorbent that involves also processing aqueous layer and the following isolation the main product - isoprene from hydrocarbon condensate. Vat residue after rectification of 4,4-dimethyl-1,3-dioxane is separated by rectification for two stages carried out successively in in-line connected columns and bottom product from the first stage - heavy residue with ignition point 130-155°C is removed as floating reagent-oxal. Upper product from the first stage is fed for processing to the second stage and upper product from the second stage - light-boiling part of high-boiling by-side products is fed for decomposition completely on calcium-phosphate catalysts separately or in common with 4,4-dimethyl-1,3-dioxane. Bottom product from the second stage is fed to the synthesis process of 4,4-dimethyl-1,3-dioxane as recycle. Upper product from the second stage in processing by rectification of vat residue of rectification of 4,4-dimethyl-1,3-dioxane is fed for preparing absorbent only in case of stopping decomposition reactors with high-boiling by-side products or reactors wherein 4,4-dimethyl-1,3-dioxane is decomposed. In stopping reactors with decomposition of high-boiling by-side products upper product of the second stage is removed as recycle to synthesis of 4,4-dimethyl-1,3-dioxane and as absorbent component removing in the amount 25-35% of mass of vat residue of rectification of 4,4-dimethyl-1,3-dioxane feeding to the first stage. In stopping reactors with decomposition of high-boiling products and if necessary a mixture of dioxane alcohols, in particular, hydroxyisopropyl-4,4-dioxane-1,3, methyl-4-hydroxyethyldioxane-1,3 and dimethyl-4,4-hydroxymethyl-5-dioxane-1,3 are removed additionally as a bottom product of the second stage. Invention provides enhancing effectiveness in using waste - high-boiling by-side products, preparing additional amount of isoprene from them and enhancing regulation of the process.

EFFECT: improved preparing method.

4 cl, 1 dwg, 6 ex

FIELD: petrochemical processes.

SUBSTANCE: tert-butyl alcohol, 4,4-dimethyl-1,3-dioxan and/or formaldehyde are fed into reaction zone in the form of homogenous mixture with recycled aqueous solution of acid catalyst, which mixture is preliminarily prepared in a separate apparatus at heated to 80-90°C and said aqueous acid solution freed of organics is preliminarily passed through cationite at volume flow rate 15-20 h-1. Process is conducted at elevated temperature and pressure exceeding pressure of water steam at this temperature, and at molar excess of tert-butyl alcohol relative to summary amount of formaldehyde in hollow apparatus mounted coaxially over shell-and-tube heat exchanger and provided with circulation pipe connecting top part of hollow apparatus to bottom part of shell-and-tube heat exchanger, diameter of this pipe being at least three times lass than that of hollow reactor. Circulating factor at least 100 h-1 is achieved with the aid of pump installed in feed supply line into bottom part of hollow apparatus. Reaction products and part of aqueous acid solution are removed from the top of hollow apparatus in one stream passed into separator.

EFFECT: simplified technology and increased yield of isoprene.

1 dwg, 3 tbl, 3 ex

FIELD: industrial organic synthesis and petrochemistry.

SUBSTANCE: isoprene is produced via reaction of tert-butyl alcohol with 4,4-dimethyl-1,3-dioxane and/or formaldehyde in one reaction zone, namely upright hollow apparatus with, disposed inside it, shell-and-tube heat exchanger dividing apparatus space into top and bottom parts. Reaction mixture circulates through tubes of this apparatus in liquid-phase mode in presence of aqueous acid catalyst solution, at elevated temperature and pressure exceeding water vapor pressure at the same temperature, using molar excess of tert-butyl alcohol relative to summary formaldehyde equivalent. Reaction products are continuously withdrawn from reaction zone and subjected to condensation. Water phase is extracted with condensed distillate to remove organics, wherefrom isobutylene is recovered and sent to production of tert-butyl alcohol. Hollow apparatus is provided with one or two external circulation tubes connecting top and bottom spaces of apparatus, volume ratio of which is (2-2.5):1, respectively. Diameter of external tubes is at least fivefold greater that that of heat exchanger tubes. Feed is supplied to reaction zone in the form of homogenous mixture, preliminarily prepared in a separate apparatus and preheated to 80-90°C, together with recycle aqueous catalyst solution, the latter having been preliminarily freed of organics and passed at flow rate 15-20 h-1 through cationite. Process is carried out at circulation rate at least 100 h-1.

EFFECT: simplified technology and increased yield of isoprene.

1 dwg, 2 tbl, 2 ex

FIELD: industrial organic synthesis and petrochemistry.

SUBSTANCE: isoamylenes are subjected to dehydrogenation in presence of overheated water steam and catalyst containing, wt %: potassium oxide and/or lithium oxide, and/or rubidium oxide, and/or cesium oxide, 10-40; cerium(IV) oxide 2-20; magnesium oxide 2-10; calcium carbonate 2-10; sulfur 0.2-5; and ferric oxide - the rest.

EFFECT: increased isoamylene dehydrogenation degree due to increased catalyst selectivity with regard to isoprene and prolonged service time of catalyst.

2 tbl, 22 ex

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