WO2007126329A1

WO2007126329A1 - Isoprene producing method

Info

Publication number: WO2007126329A1
Application number: PCT/RU2006/000481
Authority: WO
Inventors: Vladimir Fedorovich BOGATYREV
Original assignee: Bogatyrjov Vladimir Fjodorovic
Priority date: 2006-05-02
Filing date: 2006-09-14
Publication date: 2007-11-08
Also published as: RU2330010C2; RU2006115196A

Abstract

The invention relates to the petrochemical industry. Isoprene is produced by a liquid-phase interaction of formaldehyde with isobutylene comprising isobuthylene-containing fractions of isobutane dehydrogenation and oil fractions of catalytical cracking or pyrolyse. The process is carried out in two stages in a running water medium containing phosphoric acid in the form of a catalyst. The first stage consists in producing a mixture of methylbutainediol and dimethyldioxane which are converted, at the second stage, into isoprene extractable from the reaction medium by means of flowing organic solvent. The use of a countercurrent scheme for bringing into contact organic products partially soluble in water phase makes it possible to use the isobuthylene-containing fractions. For carrying out said method, the structural design for an isothermic countercurrent liquid-phase case-tubular column reactor is disclosed. A regular spiral nozzle is used in the form of a contacting device in reactors and in other process heat-mass-exchange equipment. The use of isobuthylene-containing raw material in said process extends a raw material resource base and improves the efficiency of the method. Said method makes it possible to simultaneously produce highly-pure isoprene and isobuthylene products.

Description

DESCRIPTION OF THE INVENTION

Title of invention: METHOD FOR PRODUCING ISOPRENE.

1. The technical field to which the invention relates.

The invention relates to the petrochemical industry. 2. The level of technology.

The prototype of the invention METHOD FOR PRODUCING ISOPRENE is the method described in patent RU 2116286. The method consists in a liquid-phase two-stage interaction of formaldehyde with isobutylene or with mixtures of isobutylene with tert-butyl alcohol (TBS) and / or methyl tert-butyl ether (MTBE) in an aqueous medium in the presence of an aqueous catalyst in an aqueous medium which use phosphoric acid. In the first stage, a mixture of the main intermediate products is obtained: methylbutanediol (MBD), dimethyldioxane (DMD). An inert organic solvent is introduced into the second stage of the process to isolate the resulting isoprene, which is used as a hydrocarbon or a mixture of hydrocarbons with a boiling point in the range of 70-90 ⁰ C. The concentration of formaldehyde, calculated on the total flow supplied to the first stage, is maintained at 2- 10 wt.%. The total amount of isobutylene supplied to both stages is 1.5-5 moles per 1 mol of the starting formaldehyde. From it, according to the options: 40-99% is fed to the first step or all isobutylene is fed to the first step so that its conversion is 40-99% and unconverted isobutylene is then fed to the second step. The total amount of TBS and / or MTBE supplied to the first and / or second stages of the process is 0.5-3 moles per 1 mol of the starting formaldehyde. The concentration of phosphoric acid, calculated on the total flow supplied to the first stage, is maintained at the level of 5-50%. An inert organic solvent is introduced in an amount of 0.2-3 May. parts calculated on May 1. part of the water. The process is carried out at temperatures: at the first stage 30-90 ⁰ C, at the second - 110-145 ⁰ C; and a total pressure of 10-40 atm. Reagents are fed to the reactors of the first and second stages in a direct flow through rotary and / or static type mixers.

After the second stage, the reaction mixture is separated by settling at a temperature of 50-90 ⁰ C into an oil layer containing the target product and an aqueous layer. The aqueous layer containing phosphoric acid is evaporated

SUBSTITUTE SHEET (RULE 26) with a residual pressure of 5-100 mm Hg and before recirculation to the first step of the process is mixed with the original aqueous solution of formaldehyde. The oil layer after washing with water is separated by distillation with the release of isobutylene and isoprene, and 0.1-0.9 wt.h. the residue is recycled to the second stage of the process.

The disadvantage of the described prototype is the low efficiency of the process in once-through reactors, forcing the use of concentrated products of processing and isobutylene-containing raw materials (isobutylene, TBS, SCHE), which affects the technical and economic performance of the process.

3. Disclosure of the invention.

The claimed invention is directed to the intensification of reaction processes.

The technical result of the invention is the possibility of using isobutylene-containing raw materials in the process, which expands the raw material base and improves the efficiency of the method.

The essence of the invention lies in the fact that a two-stage process for producing isoprene by liquid-phase interaction of isobutylene with formaldehyde in an aqueous medium in the presence of an acid catalyst and the introduction of an inert organic solvent into the second stage is proposed to be carried out in a countercurrent reactor system.

An essential distinguishing feature of the invention is the use of countercurrent reactors for carrying out reaction processes. Countercurrent reaction processes allow the rational use of the kinetics of the processes occurring at each stage, which makes it possible to use isobutylene-containing raw materials, expand the raw material base and improve the process efficiency indicators. In addition, the isolation and purification of intermediate products after the first step helps to improve the quality of isoprene.

To implement the proposed method for producing isoprene, the invention provides:

• As reactors in the first stage, use an adiabatic countercurrent liquid-phase column reactor or an isothermal countercurrent liquid-phase column-type shell and tube reactor, and in the second stage only an isothermal counter-flow liquid-phase column-type shell and tube reactor.

• Use phosphoric acid as an acid catalyst.

SUBSTITUTE SHEET (RULE 26) • To ensure effective phase contact in reactors and other heat and mass transfer equipment of the process, it is preferable to use a regular SPIRAL NOZZLE FOR HEAT AND MASS EXCHANGE AND CHEMICAL PROCESSES COMBINED WITH THEM (registration number of the application for invention 2004115769, filing date 24.05.2004).

• Use isobutylene-containing fractions of isobutane dehydrogenation, catalytic cracking or pyrolysis of petroleum fractions or mixtures thereof as raw materials.

• The oil layer leaving the top of the 1st stage reactor, in the stage of separation of intermediate products, is washed sequentially from acid in a water washing column and separated by rectification with the conclusion of a hydrocarbon fraction (isobutane or butylene depending on the origin of the used isobutylene-containing raw materials), a mixture of intermediate products and recycle isobutylene fraction to the reactor.

• The saturated solvent leaving the top of the 2nd stage reactor is washed sequentially from the acid in the water washing column during separation of isoprene and separated by distillation to isolate isobutylene, isoprene, depleted solvent and high boiling point by-products (WFP).

• Isobutylene from the isoprene separation stage, partially recycle under the lower distribution plate of the adiabatic zone in the still bottom of the 2nd stage reactor, and withdraw the balance excess as a qualified product.

• Put the depleted solvent from the isoprene separation stage together with the intermediate product mixture from the intermediate separation stage under the upper distribution plate installed under the lower tube sheet of the isothermal zone of the second stage reactor.

• A portion of the aqueous phase from the cube of the 1st stage reactor, together with the aqueous phases of the washing stages of the separation of intermediate products and the isolation of isoprene, as well as with the reinforcement with acid reinforced from the evaporator, should be sent to the top of the 2nd stage reactor.

• The aqueous phase leaving the cube of the 2nd stage reactor together with the remaining part of the aqueous phase from the cube of the 1st stage reactor is fed to the concentration of phosphoric acid in the evaporator.

SUBSTITUTE SHEET (RULE 26) • Drive away organic products from the distillate of the evaporator in the distillation treatment unit by distillation for disposal. 4. A brief description of the drawings.

Figure l is a sketch of an isothermal reactor Figure 2 is a process diagram of the method. 5. The implementation of the invention.

The process under consideration, the chemical interaction and destruction of the reagents in which they take place in the continuous aqueous phase, includes an important component - the transport of poorly soluble reagents of the hydrocarbon phase to the aqueous phase and the conclusion of the intermediate and target product from it into the hydrocarbon phase. The most efficient interfacial transport is solved by using a countercurrent extraction scheme [1, p. 445–449], which allows the use of isobutylene-containing raw materials [2, p. 47].

Both stages of the process pass with thermal manifestations: in the first stage exothermic, in the second - endothermic. Therefore, for carrying out the process in the most favorable temperature conditions, minimizing the yield of by-products, an isothermal reactor design is provided. In the 1st stage, it is permissible to use a less complex adiabatic countercurrent liquid-phase column reactor, which allows the use of part of the heat of the exothermic reaction, which is mainly removed with the aqueous phase to the 2nd stage and to the evaporator.

An analogue of a countercurrent isothermal reactor is the industrial isothermal DMD synthesis reactor described in [2, p. 47], the design of which is based on the principle of a spray column. The process uses the isobutanisobutylene fraction. The design drawback of this reactor is a large breakthrough of isobutylene (over 20% in the return fraction), • as a result of the rapid coalescence of polydispersed “dust”. A rapid and significant decrease in the contact surface correspondingly decreased the rate of extraction of isobutylene into the aqueous phase.

Since the processes in both steps are determined by the kinetic region, a fine dispersion of the organic phase should not be achieved. It is enough to ensure that the dispersion is maintained in the entire reaction volume under gravitational conditions with the use of disk devices or regular packing.

SUBSTITUTE SHEET (RULE 26) To this end, the invention provides for the use, as a dispersing device, in reactors, as well as in other heat and mass transfer equipment, of predominantly regular SPIRAL NOZZLE FOR HEAT AND MASS EXCHANGE AND CHEMICAL PROCESSES COMBINED WITH THEM. The advantages of this nozzle in the largest free section, low holding capacity and the possibility of its design optimization for processes by selection of geometric characteristics and surface structure.

Countercurrent reaction processes in reactors with a spiral nozzle make it possible to rationally use the kinetics of the processes occurring at each stage, which makes it possible to use isobutylene-containing raw materials, expand the raw material base and improve the process efficiency indicators.

The drawing of Fig. L shows a sketch of an isothermal countercurrent liquid-phase shell-and-tube column thorn reactor.

In the pipe space 1 and in the adiabatic zones 2, a spiral nozzle is installed in the form of layer packets.

The dispersible phases are introduced using tubular distributors 3 (an upper distributor is not required for the 1st stage reactor), above which the distributor 4 and 5 are placed. The distributor 4 can serve to install packages of spiral nozzles of the lower adiabatic zone on it. In the strainer 5 to distribute the dispersible phase in the pipes, the holes are localized opposite each pipe, and the pipes of the continuous phase (not shown) are evenly distributed over the area between the pipe axes. The sieve distributor 5 is spaced from the tube sheet 6 at a distance that excludes the possibility of unacceptable deviation of the jets of the dispersed phase by the flow of a continuous phase. In the strainer 4 openings and drain pipes are evenly distributed over the area.

The arrangement of the upper and lower adiabatic zones 2 significantly reduces the metal consumption of the reactor due to the possibility of reducing the length of the tube bundle with an allowable temperature effect of up to 10 ⁰ C. In addition, the lower adiabatic zones provide a minimum breakthrough of formalin and intermediate products with aqueous layers going to be strengthened in the evaporator .

Above the upper adiabatic zone 2 there is a tubular distributor of a continuous phase 7. The upper nozzle 8 and the lower 9 serve respectively for the output of the oil and water layers, and the nozzles 10 -

SUBSTITUTE SHEET (RULE 26) to determine the level of phase separation in the settling zone of the reactor. For the input and output of heat and refrigerants into the annulus of the reactor, appropriate fittings (not shown) are provided.

The drawing of figure 2 presents the process diagram of a method for producing isoprene.

Isobutylene in the composition of isobutylene-containing fractions of isobutane dehydrogenation, catalytic cracking or pyrolysis of oil fractions (or mixtures thereof) along line 11 together with the recycle isobutylene fraction from the stage of separation of intermediate products through line 12 is fed to the lower tube distributor 3 of the reactor of the first stage of the process (or under adiabatic reactor nozzle).

The technical formalin coming in through line 13 is combined with phosphoric acid coming in through line 14 from the evaporator and is fed to the top of the reactor through a tube distributor 7 (or to the nozzle of the adiabatic reactor).

The molar consumption of isobutylene in the composition of the isobutylene-containing fraction to isoprene is maintained within 1.2 ÷ 1.4: 1, and the molar ratio of isobutylene: formalin, respectively, 0.8 ÷ l, 2: l. The acid concentration at the inlet to the reactor is maintained at the level of 15–40%, and the consumption is 3–8 t / t of isoprene. The temperature of the continuous aqueous phase in the reactor 50 ÷ 80 ° C support the supply of refrigerant into the annular space of the isothermal reactor (or the temperature of the incoming flows into the adiabatic reactor). The pressure in the system is maintained at a level corresponding to the guaranteed content of the reaction medium in the liquid phase.

The oil layer leaving line 15 from the top of the l * -th stage reactor, in the stage of separation of intermediate products, is successively washed from acid in a water washing column and separated by distillation with the conclusion of hydrocarbon fractions (isobutane or butylene depending on the origin of the used isobutylene-containing raw materials), mixture intermediate products and recycle isobutylene fraction. Isolation and purification of intermediate products after the first step contributes to the production of isoprene with a mass purity of more than 99%.

Return hydrocarbon fraction through line 16 is sent for further processing. The mixture of intermediate products through line 17 is fed under the upper distribution plate through the upper tubular distributor 3 in the still bottom of the second stage reactor. Recycle

SUBSTITUTE SHEET (RULE 26) the isobutylene fraction along line 12 is fed into the lower tubular distributor 3 of the reactor of the first stage (or under the nozzle of the adiabatic reactor). The aqueous phase of the washing line 18 is fed into the reactor of the 2nd stage.

The aqueous phase from the bottom part of the reactor of the first stage of the process is partially fed through line 19 to the upper part of the reactor of the second stage of the process through a tubular distributor of the aqueous phase 7. Into the same stream, the aqueous phases of the washing are introduced from the stage of separation of intermediate products through line 18 and from the stage of isolation of isoprene along line 20.

The concentration of phosphoric acid is 15–40% and the consumption of 3–8 tn / t of isoprene in the total stream 21 is supported by the supply of fortified phosphoric acid from the evaporator via line 22 with the adjustment of the balanced removal of the aqueous phase from the first stage reactor via line 23 to the evaporator.

The intermediate products from the stage of separation of intermediate products through line 17 and the circulating stream of depleted solvent from the stage of separation of isoprene through line 24 are directed under the upper distribution plate of the bottom stage reactor of the 2nd stage through the dispersed phase 3 distributor. The depleted solvent flow rate is maintained at 4 ÷ 7 t / t isoprene. Under the lower distribution plate of this reactor, isobutylene is circulated through line 25 from the isoprene recovery stage through a dispersed phase 3 tube distributor. The flow rate of circulating isobutylene is maintained within 0.5-KL, 5 t / t of isoprene.

The isothermal process for producing isoprene with its extraction with a solvent is carried out at a temperature of a continuous aqueous phase of 110 ÷ 125 ° C, which is ensured by supplying a coolant to the annulus of the reactor.

The aqueous phase from the cube of the reactor via line 26 is fed to the strengthening of phosphoric acid in the evaporation unit.

The saturated solvent (oil layer) from the top of the 2nd stage reactor is sent via line 27 to the isoprene separation stage, where it is washed with water in a water washing column and separated in the distillation system with the release of isobutylene, isoprene, high boiling by-products (WFP) and depleted solvent .

SUBSTITUTE SHEET (RULE 26) Isobutylene is partially fed to the bottom of the 2nd stage reactor via line 25, and the rest through line 28 is discharged as a qualified product. The removal of isobutylene is regulated by the supply of formalin to the system.

The depleted solvent is supplied via line 24 along with intermediate products through line 17 to the upper distribution plate 5 of the second stage reactor.

Isoprene is sent via line 29 as the target product, and high boiling point by-products (WFP) are sent via line 30 for further processing.

The aqueous phases from the cubes of the reactors of both stages are fed through lines 23 and 26 to the evaporator, where at a temperature of 40–50 ° C and a residual pressure of 50–100 mm Hg. Art. acid is strengthened to 40 ÷ 60% concentration. The fortified phosphoric acid in line 31 is diluted in the reactors.

The distillate of the evaporator through line 32 is fed to the wastewater treatment unit, where the organic substances discharged through line 33 are distilled off by distillation for further processing, and the water, after neutralization with alkali, is sent to the sewage of factory sewage.

Bibliographic data:

1. V.B. Kogan. Theoretical foundations of typical processes of chemical technology. Chemistry 1977.

2. S.K. Ogorodnikov, G.S. Idlis. Isoprene production. Chemistry 1973.

SUBSTITUTE SHEET (RULE 26)

Claims

CLAIM

1. A method of producing isoprene, comprising the liquid-phase interaction of formaldehyde with isobutylene in a circulating aqueous medium in the presence of an acid catalyst in two stages, using a circulating inert organic solvent in the second stage to isolate isoprene, characterized in that the process in both stages is countercurrent reactors.

2. The method according to p. 1, characterized in that phosphoric acid is used as the acid catalyst.

3. The method according to p. 1, characterized in that the reactors in the first stage use an adiabatic countercurrent liquid-phase column reactor or an isothermal countercurrent liquid-phase shell-and-tube column reactor, and in the second stage only an isothermal counter-current liquid-phase shell-and-tube column-type reactor.

4. The method according to p. 1, characterized in that the reactors and other heat and mass transfer equipment of the process mainly use a regular SPIRAL NOZZLE FOR HEAT AND MASS EXCHANGE AND CHEMICAL PROCESSES COMBINED WITH THEM (registration number of the application for the invention 2004115769, filing date 24.05.2004).

5. The method according to p. 1, characterized in that as raw materials use isobutylene-containing fractions of isobutane dehydrogenation, catalytic cracking or pyrolysis of oil fractions or mixtures thereof.

6. The method according to p. 1, characterized in that the oil layer emerging from the top of the 1st stage reactor, in the stage of separation of intermediate products, is sequentially washed from the acid in the water washing column and separated by rectification with the conclusion of the hydrocarbon fraction (isobutane or butylene depending from the origin of the used isobutylene-containing raw materials), a mixture of intermediate products and the isobutylene fraction recycle to the reactor.

7. The method according to p. 1, characterized in that the saturated solvent leaving the top of the reactor of the 2nd stage, in the stage of separation of isoprene is successively washed from the acid in the column

SUBSTITUTE SHEET (RULE 26) water washing and separated by distillation with the release of isobutylene, isoprene, depleted solvent and boiling by-products.

8. The method according to p. 1, characterized in that the isobutylene from the isoprene separation stage is partially recycled under the lower distribution plate of the adiabatic zone in the still bottom of the second stage reactor, and the balance excess is withdrawn as a qualified product.

9. The method according to p. 1, characterized in that the depleted solvent from the stage of separation of isoprene together with a mixture of intermediate products from the stage of separation of intermediate products is fed under the upper distribution plate installed under the lower tube sheet of the isothermal zone of the second stage reactor.

10. The method according to p. 1, characterized in that a part of the aqueous phase from the cube of the 1st stage reactor, together with the aqueous phases of the washing stages of the separation of intermediate products and the isolation of isoprene, as well as fed with fortified acid from the evaporator are fed to the top of the 2nd reactor steps.

11. The method according to p. 1, characterized in that the aqueous phase leaving the bottom of the second stage reactor along with the remaining part of the aqueous phase from the first stage reactor is fed to the concentration of phosphoric acid in the evaporator.

12. The method according to p. 1, characterized in that the organic products for distillation are distilled off from the distillate of the evaporation unit in the effluent treatment unit by distillation.

SUBSTITUTE SHEET (RULE 26)