RU2203878C2 - Isoprene production process - Google Patents

Abstract

FIELD: industrial organic synthesis. SUBSTANCE: invention provides process consisting in liquid-phase reaction of formaldehyde and optionally formaldehyde precursor(s) with tert-butanol and optionally isobutene in isoprene-synthesis reaction zone in presence of strong acid catalyst and water at elevated temperature and molar excess of tert-butanol supplied relative to summary amount of formaldehyde fed into indicated reaction zone and possibly that released by indicated formaldehyde precursor(s), in which process synthesized isoprene and isobutene and a part of water are continuously distilled off the reaction zone, after which isoprene and isobutene are isolated. Vertical isoprene-synthesis reaction zone, with its height at least fourfold exceeding its diameter, connected from below to boiler, is operated at pressure maintained at a level preventing condensation of isoprene whereas larger part of water and formaldehyde and considerable part of tert-butanol are in liquid phase. Vapors and liquid in reaction zone move predominantly in bottom-up direction. From the top part of reaction zone, one or two liquid streams are withdrawn with boiling temperatures higher than that of isoprene. At least part of recovered isobutene is subjected to reaction with water and resulting tert-butanol is reused in isoprene synthesis. EFFECT: simplified technology. 11 cl, 3 dwg, 4 tbl, 11 ex

Description

 The invention relates to the field of production of isoprene from isobutene and / or tert-butanol and formaldehyde.

 More specifically, the invention relates to the field of the production of isoprene from isobutene and / or tert-butanol and formaldehyde without intermediate recovery of intermediates that are precursors of isoprene, for example 4,4-dimethyldioxane and / or 3-methylbutane-1,3-diol.

 The known method [US 4593145, 06/03/1986] for the production of isoprene by chemical interaction of alkyl tert-butyl ether with formaldehyde in an acidic aqueous solution, characterized in that the specified alkyl tert-butyl ether, a source of formaldehyde and water and isoprene, water, unreacted starting materials, isobutene, tert-butanol and other low-boiling components are distilled off from the indicated reaction zone, the amount of alkyl tert-butyl ether being supplied to the reaction zone and of formaldehyde is such that the molar ratio of alkyl tert-butyl ether: formaldehyde in the diet is at least 2 and the pressure is maintained from 1.2 to 3.5 times higher than the pressure of the aqueous acid solution existing in the reaction zone at the reaction temperature.

 The disadvantage of this method is that when using alkyl tert-butyl ether (s), a large amount of the corresponding alkyl (s) alcohol (s) and various esters are formed, the separation of which from the target product is very difficult.

 Known and closest to our proposed method [US 4511751, 04.16.1985] producing isoprene by chemical reaction of isobutene and / or tert-butanol with formaldehyde in the reaction zone in an acid-aqueous solution, characterized in that isobutene and / or tert-butanol , the formaldehyde source and water are fed continuously or periodically to said reaction zone and isoprene, water, unreacted starting materials and other low boiling components are distilled off from the reaction zone, the amount of isobutene and / or tert-butano being fed and formaldehyde and / or its source are such that the molar ratio of isobutene and / or tert-butanol (total) to formaldehyde is at least 3 and the pressure in the reaction zone is maintained at a level of 1.1-2.5 times higher than the acid pressure aqueous solution at the temperature of the reaction zone.

 Alternatively, US 4,511,751 proposes to carry out the process in several reaction zones, with isobutene and / or tert-butanol being fed to the first reaction zone, and a source of formaldehyde and water being supplied to each reaction zone continuously or periodically.

 The method according to US 4511751 has several disadvantages.

 It does not provide for effective vertical contacting of steam and liquid streams. In all examples, US 4,511,751 shows the use of agitators as reactors, which is difficult for technological implementation in highly corrosive environments.

 There is no effective system for removing high-boiling by-products (WFP) from the reaction zone. The withdrawal of the acid-water solution from the bottom of the reaction apparatus (with recirculation to the boiler) leads to the runway entering the hot walls of the boiler tubes and the formation of deposits.

 The pressure in the reaction apparatus (zone) specified in US 4,511,751 (1.1-2.5 times higher than the pressure of an acid-water solution at the reaction temperature) can lead to the presence of a part of isoprene in a condensed (partially dissolved) state, which leads to the formation of a runway and related negative phenomenon.

 On the other hand, the fact that unreacted starting materials (including tert-butanol are distilled off (“distilled”) from the reaction zone) can lead to the absence or insufficient content of tert-butanol in the reaction zone liquid necessary for the chemical binding of formaldehyde, leading to increased formation of high molecular weight products clogging equipment deposits.

The method according to US 4511751 allows for the absence of tert-butanol in the reaction zone (isobutene and / or tert-butanol are claimed). Since the isobutene feed is a very light product (normal. Bp = -6.9 ^° C) and will be practically absent in the liquid phase under synthesis conditions, effective chemical “binding” of formaldehyde is not guaranteed and the possibility of formation of high molecular weight products with it clogging equipment deposits.

 We propose a method for producing isoprene, including the liquid-phase interaction of formaldehyde and possibly substances (a), which is their source of formaldehyde with tert-butanol and possibly isobutene in the reaction zone of isoprene synthesis in the presence of a strong acid catalyst and water at elevated temperature and a molar excess supplied tert-butanol in relation to the total amount of formaldehyde supplied to the specified reaction zone for the synthesis of isoprene and possibly emitted by the specified source of formaldehyde, with continuously the distillation of the resulting isoprene, isobutene and part of the water from the reaction zone for the synthesis of isoprene and the subsequent separation of isoprene and isobutene, according to which the process is carried out in a vertical reaction zone for the synthesis of isoprene, having a height of at least 4 times the diameter connected to the bottom of the boiler, support it has a pressure at which there is no condensation of isoprene, but most of the water, formaldehyde and a significant part of tert-butanol are in the liquid phase, the vapor and liquid move in the reaction in the isoprene synthesis zone mainly from the bottom up, one or two liquid streams containing substances with higher boiling points than isoprene are withdrawn from the upper part of the zone, and at least part of the isolated isobutene is reacted with water and the resulting tert-butanol reused in the synthesis of isoprene.

 Alternatively, a method is proposed, according to which, at least in the part of the reaction zone for the synthesis of isoprene mass transfer devices and / or mass transfer nozzle are arranged.

 As a variant, a method is proposed according to which the isoprene synthesis reaction zone and the multi-tube boiler are connected so that they form a single apparatus and each of the boiler tubes is directly connected to the isoprene synthesis reaction zone, and the annular space into which the heating agent enters is separated from her.

Alternatively, a method is proposed according to which a part of tert-butanol and / or isobutene, possibly mixed with other hydrocarbons, is subjected to transformation in the liquid-phase reaction zone for the synthesis of intermediate products - isoprene precursors in the presence of formaldehyde, water and a strong acid catalyst, and the reaction mixture is led, possibly after distillation of the unreacted C ₄ hydrocarbons into the reaction zone for the synthesis of isoprene and / or the boiler connected to it.

 Alternatively, a method is proposed according to which the isolated isobutene or a part thereof is reacted with water and possibly formaldehyde in a separate conversion zone of the isolated isobutene in the presence of a strong acidic catalyst and the resulting tert-butanol or reaction mixture, possibly after isobutene is distilled off, is fed into the isoprene synthesis reaction zone and / or a boiler connected to it, and / or into a liquid-phase reaction zone for the synthesis of intermediates - isoprene precursors.

Alternatively, a method is proposed whereby the isolated isobutene or a portion thereof is reacted with water and possibly formaldehyde in the presence of a strong acidic catalyst together with a raw isobutene-containing hydrocarbon mixture and the resulting tert-butanol or reaction mixture, preferably after distillation of unreacted C ₄ hydrocarbons, is sent to the reaction the isoprene synthesis zone and / or the boiler connected to it, and / or into the liquid-phase reaction zone for the synthesis of intermediates - precursors of iso prena.

 Alternatively, a method is proposed according to which formaldehyde and / or tert-butanol and / or the reaction mixture (s) obtained by reacting isobutene and / or isobutene-containing mixture with water and possibly formaldehyde are supplied in two or more streams at different levels the reaction zone for the synthesis of isoprene, but not higher than 3/4 of its height.

 Alternatively, a method is proposed according to which a strong acid is used as the acid catalyst, preferably in the presence of a corrosion inhibitor (s), or acid cation exchanger.

 Alternatively, a method is proposed according to which a liquid stream is withdrawn from the upper part of the isoprene synthesis reaction zone, containing mainly water and a strong acidic catalyst, which is preferably after delamination of undissolved organic substances and possibly after extraction of high-boiling by-products with substances or mixtures that do not form aqueous acid a stream of a homogeneous mixture, sent to the lower part of the reaction zone for the synthesis of isoprene and / or the boiler connected to it, and / or the interaction zone (s) I isobutene with water and / or precursors of isoprene synthesis zone.

 Alternatively, a method is proposed according to which a process in an isoprene synthesis reaction zone is carried out in the presence of a high boiling inert solvent that does not form a homogeneous mixture with water, and a liquid stream containing said inert solvent and high boiling point by-products is withdrawn from the upper part of the isoprene synthesis zone.

 Alternatively, a method is proposed according to which, when using a strong acid as a catalyst in an aqueous solution, at least part of the specified solution is distilled off excess water in a separate apparatus, after which the solution is again used in the process.

К числу других веществ можно отнести диоксановые и алкилдиоксановые спирты, формали диоксановых спиртов, метиловые и трет-бутиловые эфиры диоксановых спиртов.As substances that are the source of formaldehyde, substances that are formed during the interaction of formaldehyde with isobutene and / or tert-butanol and which in the reaction zone of isoprene synthesis in the presence of a strong acid catalyst and water at an elevated temperature can be converted with the release of free formaldehyde can be used . The main representative of such substances is 4,4-dimethyl-1,3-dioxane, decomposing mainly by reaction:

Other substances include dioxane and alkyldioxane alcohols, formaldes of dioxane alcohols, methyl and tert-butyl ethers of dioxane alcohols.

All of the above sources of formaldehyde:
- can be formed directly in the process under consideration, stand out from the reaction mass and return to the reaction (s) zone (s);
- can be obtained in a separate process, for example, as was implemented in industry at stage I of a two-stage process for the synthesis of isoprene from isobutylene and formaldehyde, and the installation for their preparation can be located either at another enterprise or at the same enterprise as the proposed process ;
- can be obtained by combining both of the previous options.

 The implementation of the invention is illustrated by drawings (Fig. 1-3) and examples 1-10.

 These figures and examples do not exhaust all possible embodiments of the invention and other technical solutions are possible subject to its essence set forth in the claims.

 According to FIG. 1 tert-butanol (TB) flows through line 1 and an aqueous solution of formaldehyde (Ф) - through line 2. These flows are sent to the lower part of the vertical reaction zone for the synthesis of isoprene P1 via line 3. Some of the flows may be directed to a higher level (or) zone P1 (line 4 is shown). The stream received through line 5 is also directed to the vertical zone P1, obtained after reacting with water in the reaction zone P2 of isobutene isolated in the separation unit of the BR and containing tert-butanol.

 Below, the vertical reaction zone for the synthesis of isoprene P1 is connected to the boiler ("boiler") B by liquid (to the entrance to B) and vapor-liquid (from B to P1) flows. The boiler is heated with TA. It is possible that water stream 6 is preferably supplied to boiler B, preferably in a superheated steam state, as well as a recycle stream containing an aqueous acid solution (stream 7), recycle isobutene (stream 8), and a portion of the recycle stream obtained after reaction with isobutene water in reaction zone P2 (stream 9).

 On top of the vertical reaction zone for the synthesis of isoprene P1, a stream 10 is withdrawn in the vapor state, which is sent, possibly after condensation, to the BR separation unit. One or two liquid streams 11 and 11a are also discharged from the upper part of P1, which (e) is sent to a separator-settler C. From the top, C is discharged from a stream 12 containing high-boiling impurities, and from the bottom, a stream 13 containing mainly an aqueous acid solution.

 Stream 13 may be subjected to heterogeneous contacting in stream E with stream 14, capable of dissolving high boiling point by-products, which are discharged via line 15. Stream 14 can serve (after condensation) in whole or in part stream 10. In this case, stream 15 is sent to the BR unit. Next, the water-acid stream is withdrawn through line 16 and recycled to boiler B via line 7 (possibly in P1) and / or via line 17 to reactor P2, where it is contacted with the isobutene stream removed from the BR.

 From the BR unit having at least isobutene distillation (rectification) and isoprene distillation (rectification) columns, a stream of IPR isoprene (stream 18), IB isobutene (stream 19), water B (stream 20) and PP by-products (shown as one stream 21).

 Isobutene, discharged from the BR through line 19, is preferably sent to the hydration reactor P2 (the supply option to P2 is shown below) and possibly partially directed to the boiler B along line 8. An additional stream of water can be directed to P2 (stream 22).

 From P2, a stream 23 containing tert-butanol and concentrated isobutene is withdrawn, and a stream 24 containing water or an aqueous acid solution, which is cooled and recycled to the inlet of P2 through line 25 and / or sent via line 26 to the vertical isoprene synthesis reaction zone P1 and / or boiler B.

 Stream 23 is sent to P1 and / or B and / or to node K (line 27), where isobutene is distilled off via line 28, which is then preferably sent to boiler B and / or used as an extractant of high-boiling by-products in the extractor E. From K from the bottom along line 29, a stream containing tert-butanol is withdrawn, which is sent to P1 (along lines 30 and 5) and possibly to boiler B (line 9).

 The aqueous acidic solution can be sent via line 31 and / or 26 to node O, where the excess water removed via line 32 is distilled off. A more concentrated aqueous acidic solution is removed via line 33 and then sent to B and / or P1, and / or P2.

 A stream 34 containing formaldehyde F can be additionally introduced into the reactor P2. In this case, streams 23 and 24 withdrawn from P2, in addition to tert-butanol, contain 4,4-dimethyl-1,3-dioxane, 3-methylbutane-1, 3-diol and possibly other substances that are intermediates - precursors of isoprene.

In FIG. 2 in contrast to FIG. 1 shows the use of a vertical reaction zone for the synthesis of isoprene P1, which has a boiler B in the lower part, the tubes of which directly communicate with the overlying space P1. Also unlike FIG. 1, not only isobutene discharged from the BR unit via line 19, but also an isobutene-containing mixture of hydrocarbons (mainly C ₄ ) via line 35 is fed to reactor P2.

The organic stream withdrawn from P2 is fed via line 27 to a distillation column K. On top of it, a mixture of unreacted C ₄ hydrocarbons is withdrawn via line 28. Bottom line 29 output stream containing tert-butanol, which on line 30 and then on line 5 is sent to P1. Part of the stream 30 along line 9 can be fed into boiler B.

 The functional purpose of the remaining devices, nodes and lines coincides with that shown in FIG. 1 and the foregoing in its description.

 Formaldehyde F solution can be fed to reactor P2 (line 34). This contributes to a more complete conversion of isobutene to P2. At the same time, streams 23 and 24 removed from P2 (hereinafter streams 29 and 26) contain, in addition to tert-butanol, also the resulting intermediates - isoprene precursors: 4,4-dimethyl-1,3-dioxane, 3-methylbutane-1,3- diol and others

 In FIG. 3 in contrast to FIG. 1 and 2, the stream containing isobutylene (IB) is sent through line 8 to an additional reactor P3. In P3, an aqueous-acidic solution is fed through line 17 and formaldehyde F solution is fed through line 34. In P3, intermediates are formed - isoprene precursors (4,4-dimethyl-1,3-dioxane, etc.).

 From P3, stream 36 containing tert-butanol, isoprene and isobutene precursors is sent, which is sent to P1 and / or boiler B, and an aqueous acidic solution is sent via line 37, which is sent to P1 and / or B.

EXAMPLE 1
The synthesis of isoprene is carried out according to FIG. 1. The reaction zone for the synthesis of isoprene P1 has a height of 600 mm and a diameter of 100 mm. Below, the reaction zone for the synthesis of isoprene is connected with boiler B. Most of the reaction zone above the inlet stream from the boiler and below the outlet of the liquid stream is filled with mass transfer devices — an inert nozzle.

 The stream containing the starting formaldehyde, the starting tert-butanol and water is fed into the isoprene synthesis reaction zone 0.1 m higher than the feed from the boiler B. The recycled stream containing the aqueous acid solution is fed into the boiler B.

 Isobutene released in the separation unit BR interacts with water in the reactor P2. The resulting tert-butanol is returned to the isoprene synthesis reaction zone together with the starting reagents.

 At the top of the reaction zone for isoprene synthesis, a stream is sent to the BR in a vapor state, where isobutylene, isoprene, a by-product fraction and a fraction of high boiling impurities are separated from it, and in a liquid state, a stream that, after settling from high boiling impurities, is recycled to boiler B.

 In the table. 1 presents the operating parameters P1 and P2.

 In the table. 2 shows the main results of the reaction zone for the synthesis of isoprene.

EXAMPLES 2-7
The synthesis of isoprene is carried out analogously to example 1, changing the parameters of the reaction zone for the synthesis of isoprene P1 and the reaction conditions.

 The parameters P1 and the reaction conditions in P1 are presented in Table 3.

 In example 5, compared with example 1, we additionally used the method of feeding an aqueous solution of formaldehyde at three levels located 100 mm along the height of the isoprene synthesis reaction zone, starting from the point of entry of the remaining starting products, while the entire amount of formaldehyde was divided into three equal parts. The acidic aqueous layer taken from the top of the reaction zone was extracted with vapor phase condensate.

 In example 6, in comparison with example 1, an inert hydrocarbon solvent, n-octane, in an amount of 150 g / h was additionally used, and two liquid streams were taken from the top of the isoprene synthesis reaction zone.

 In example 7, in comparison with example 1, a reactor was used with a boiler installed in it.

 In the table. Figure 4 shows the main results of the reaction zone for the synthesis of isoprene.

EXAMPLE 8
The synthesis of isoprene is carried out according to FIG. 2. The reaction zone for the synthesis of isoprene P1 has a height of 1000 mm and a diameter of 100 mm and has a built-in boiler B in the lower part, the tubes of which directly communicate with the overlying space P1. Most of the reaction zone above the boiler is filled with mass transfer devices - an inert nozzle.

 A stream containing an initial 36% solution of formaldehyde in water in an amount of 350 g / h is fed into an area located 50 mm above the built-in boiler, and in an amount of 350 g / h is fed into a zone located 400 mm above the built-in boiler.

 A stream containing 88 wt.% Tert-butanol and 12 wt.% Water from a cube of distillation column K in an amount of 2800 g / h is fed into a zone located 50 mm above the built-in boiler. In the lower part of the boiler is fed in an amount of 17,400 g / h aqueous acidic solution containing 4.8 wt.% Phosphoric acid, 2.1 wt. % tert-butanol, 0.05 wt.% high boiling point by-products, 0.2 wt. % isoprene precursor intermediates, corrosion inhibitor and water (the rest is up to 100 wt.%) and isobutylene isolated in the separation unit BR is also supplied in an amount of 1411 g / h.

 The molar ratio of tert-butanol and formaldehyde supplied to the reaction unit (including as part of intermediates) is 4.5: 1.

The reaction zone for the synthesis of isoprene P1 operates at a pressure of 6.0 atm, a top temperature of 152 ^o C and a bottom temperature of 159 ^o C. The conversion of formaldehyde is 98.5%, the selectivity for the formation of isoprene based on the starting formaldehyde is 82.9%, calculated on total formaldehyde (starting plus formaldehyde contained in recycled isoprene precursor products) is 73.8%. A steam stream containing 53.6 wt.% Isobutylene, 11.2 wt.% Isoprene, 21.2 wt.% Tert-butanol, 0.5 wt.% Isoprene precursors was taken from the top of P1 in an amount of 4214 g / h 0.2 wt.% MDHP and 13.3 wt.% Water. This stream after condensation and delamination of the water is directed to extraction contacting with a stream discharged from the top of zone P1 in a liquid state in an amount of 18014 g / h and containing 1.2 wt. % tert-butanol, 0.3 wt.% isoprene precursor intermediates, 0.1 wt. % MDHP, 0.4 wt.% High boiling point by-products, 4.8 wt.% Phosphoric acid, corrosion inhibitor and water (the rest is up to 100 wt.%). As a result of extraction from a liquid aqueous acidic stream, 27 rel.% Isoprene precursor intermediates, 80 rel.% MDHP and 89 rel.% High boiling point by-products and the extracted aqueous acid stream are transferred to P1.

The hydrocarbon condensate with the extracted products is then sent to the BR separation unit, where 1118 g / h of isobutylene, 474 g / h of isoprene, 753 g / h of tert-butanol, 34 g / h of isoprene precursors, 25 g / h are isolated by rectification. MDHP and 68 g / h of high boiling point by-products. Isobutylene isolated in the BR is mixed with 3565 g / h of the initial isobutane-isobutylene fraction containing 46 wt.% Isobutylene, and the resulting mixture is reacted with water at the top of reactor P2. The P2 reactor has a diameter of 100 mm and a height of 1000 mm and is filled with the Amberlist-15 ion-exchange catalyst. The reactor P2 operates at a pressure of 20.0 atm, a top temperature of 75 ^o C and a bottom temperature of 95 ^o C. Water is also introduced into the reactor in the form of three side inlets, maintaining the total molar ratio water: isobutylene equal to 5. Conversion of isobutylene in reactor P2 75 %, selectivity for the formation of tert-butanol 99%. The reaction mixture is stratified at the bottom of reactor P2, the exfoliated water is returned to the top of P2, and the hydrocarbon layer is sent for separation to distillation column K, where a stream containing tert-butanol is separated from it as a still product (line 29), which is then fed to P1, and in the form of distillate is the residual (outgoing) mixture of C ₄ hydrocarbons.

 The isoprene precursors isolated (stream 29) are also returned to P1 to the tert-butanol feed zone.

EXAMPLE 9
The synthesis of isoprene is carried out according to FIG. 2. The reaction zone for the synthesis of isoprene P1 has a height of 1000 mm and a diameter of 100 mm and has a built-in boiler B in the lower part, the tubes of which directly communicate with the overlying space P1. Most of the reaction zone above the boiler is filled with mass transfer devices - an inert nozzle.

 A stream containing an initial 36% solution of formaldehyde in water in an amount of 400 g / h is fed to a zone located 50 mm above the built-in boiler.

 A stream containing 42 wt.% Tert-butanol, 6 wt.% Water and 52 wt.% Isoprene precursors from the cube of the distillation column K in the amount of 3780 g / h is fed into the zone located 50 mm above the built-in boiler B. In the lower part of boiler B, an aqueous acidic solution containing 3.6 wt.% Phosphoric acid, 0.5 wt.% Tert-butanol, 0.05 wt. % high boiling point by-products, 0.2 wt.% isoprene precursor intermediates, corrosion inhibitor and water (the rest is up to 100 wt.%) and isobutylene isolated in the separation unit BR is also supplied in an amount of 2170 g / h.

 The total molar ratio of tert-butanol and formaldehyde supplied to the reaction unit (including its content in intermediates) is 1.13: 1.

The reaction zone for the synthesis of isoprene P1 operates at a pressure of 7.0 at, a top temperature of 156 ^o C and a bottom temperature of 164 ^o C. The conversion of formaldehyde is 98.5%, the selectivity for the formation of isoprene based on the total formaldehyde (starting formaldehyde plus formaldehyde contained in the composition recycled isoprene precursor products) is 84.1%. 5607 g / h steam stream containing 42.8 wt.% Isobutylene, 34.8 wt. % isoprene, 11.1 wt.% tert-butanol, 2.2 wt.% isoprene precursor intermediates, 2.2 wt.% MDHP and 6.7 wt.% water. This stream, after condensation and exfoliation from water, is sent to unit E for extraction contact with a stream discharged from the top of zone P1 via line 13 in a liquid state in the amount of 18900 g / h and containing 0.2 wt.% Tert-butanol, 0.2 wt.% isoprene precursor intermediates, 0.1 wt.% MDHP, 2.0 wt. % high boiling point by-products, 3.6 wt.% phosphoric acid, corrosion inhibitor and the rest water up to 100 wt.%. As a result of extraction from a liquid aqueous acid stream into a hydrocarbon condensate (line 15), 95 rel. % of high-boiling by-products and the extracted aqueous acidic stream (line 16) after evaporation of excess water in the amount of 1880 g / h are sent to P1.

The hydrocarbon condensate with the extracted products is then sent to the separation unit of the BR, where 2400 g / h of isobutylene, 1950 g / h of isoprene, 620 g / h of tert-butanol, 123 g / h of isoprene precursors, 135 g / h are isolated by rectification. MDHP and 372 g / h of high boiling point by-products. The isobutylene isolated in BR partially in the amount indicated above (2170 g / h) is fed into boiler B and the remaining part is mixed with 5000 g / h of the initial isobutane-isobutylene fraction containing 46 wt.% Isobutylene, and the resulting mixture is reacted with water containing 19.5% formaldehyde to the top of reactor P2. The P2 reactor has a diameter of 100 mm and a height of 3000 mm and is filled with the Amberlist-15 ion-exchange catalyst. The reactor P2 operates at a pressure of 17.0 atmospheres, a top temperature of 55 ^o C and a bottom temperature of 65 ^o C. In the upper part of the reactor also serves a water stream in an amount of 5212 g / h. The conversion of isobutylene in reactor P2 is 88%, the selectivity for the formation of tert-butanol is 55%. The conversion of formaldehyde in a P2 reactor is 96%, the selectivity of formaldehyde conversion: to isoprene - 3.7%, to isoprene precursor intermediates - 83.2%, to MDGP - 5.8%, to high-boiling by-products - 7.3%. The reaction mixture is stratified at the bottom of reactor P2, the aqueous layer is returned to the top of P2, and the hydrocarbon layer is sent for separation into distillation column K, where bottoms are separated from it (stream 29), which contains mainly tert-butanol and isoprene precursors, which then served in P1, and the residual (spent) mixture of C ₄ hydrocarbons (stream 28) is removed as a distillate.

 The tert-butanol and isoprene precursors isolated in the BR are also returned to P1 in the feed zone of column bottoms K.

EXAMPLE 10
The synthesis of isoprene is carried out according to FIG. 3. The reaction system for the synthesis of isoprene P1 has a height of 1000 mm and a diameter of 100 mm and has a built-in boiler B in the lower part, the tubes of which directly communicate with the overlying space P1. Most of the reaction zone above the boiler is filled with mass transfer devices - an inert nozzle.

 A stream containing an initial 36% solution of formaldehyde in water in an amount of 700 g / h is fed to a zone located 50 mm above the built-in boiler.

 A stream containing 88 wt.% Tert-butanol and 12 wt.% Water from the cube of the distillation column K in the amount of 4180 g / h is fed into the zone located 50 mm above the built-in boiler B, and in the amount of 1000 g / h is fed into the lower part of the boiler B. In the lower part of the boiler B serves in the amount of 12044 g / h aqueous acidic solution containing 5.0 wt.% phosphoric acid, 0.5 wt. % tert-butanol, 0.05 wt.% high boiling point by-products, 0.2 wt.% isoprene precursor intermediates, and the rest up to 100 wt.% water, from unit O, in which excess water was distilled from the aqueous acid stream.

 An organic stream in an amount of 2743 g / h, containing 24.7% by weight of isobutylene, 14.9% by weight of tert-butanol, 52.7% by weight of substances being a source of isoprene and formaldehyde (mainly 4,4-dimethyldioxane-1,3), 1.6 wt. % MDHP, 4.5 wt.% Water and 1.6 wt.% High boiling point by-products, and preferably an aqueous stream in an amount of 15070 g / h, containing 0.5 wt.% Formaldehyde, 6.3 wt.% Tert-butanol 9.6% by weight of isoprene precursor intermediates (mainly 3-methylbutanediol-1,3 and isoamylene alcohols), 0.1% by weight of MDHP, 3.6% by weight of phosphoric acid, 0.7% by weight of high boilers by-products and water (the rest is up to 100%) leaving the liquid-phase reaction zone for the synthesis of precursors of isoprene P3 precursors.

 Recycled tert-butanol in the amount of 1090 g / h and recycle isoprene precursors in the amount of 245 g / h are fed from the BR separation unit to the zone 300 mm above the built-in boiler.

 The total molar ratio of tert-butanol fed to the B + P1 reaction system to the amount of free formaldehyde and formaldehyde supplied as a source of formaldehyde (taking into account that 1 mol of formaldehyde is released during decomposition of 1 mol of DMD) is 3.5: 1 .

The reaction zone for the synthesis of isoprene P1 operates at a pressure of 7.0 at, a top temperature of 156 ^o C and a bottom temperature of 164 ^o C. The conversion of formaldehyde is 98.5%, the selectivity for the formation of isoprene based on the total formaldehyde (starting formaldehyde plus formaldehyde contained in the composition recycled isoprene precursor products) is 84.2%. A steam stream containing 35.0% by weight of isobutylene, 42.4% by weight of isoprene, 14.8% by weight of tert-butanol and 1.0% by weight of isoprene precursors was taken from the top of P1 in an amount of 8799 g / h. 0.6 wt.% MDHP and 6.2 wt.% Water. This stream, after condensation and delamination of the water, is directed to extraction contact with a stream discharged from the top of zone P1 in a liquid state in an amount of 28274 g / h and containing 1.1 wt.% Tert-butanol, 0.7 wt.% Isoprene precursors , 0.4 wt.% MDHP, 1.6 wt.% High boiling point by-products, 3.6 wt.% Phosphoric acid and water (the rest is up to 100 wt.%). As a result of extraction from the liquid aqueous acidic stream, 97 rel.% Of high boiling point by-products are transferred to the hydrocarbon condensate, and the extracted aqueous acidic stream is divided into two streams. The first in the amount of 17613 g / h is sent to node O, where 5569 g / h of excess water is distilled off and the remaining water-acid stream remaining after evaporation in the amount and composition indicated above is sent to B. The second in the amount of 10153 g / h is sent to the lower part of the liquid-phase reaction zone for the synthesis of isoprene P3 precursor intermediates.

 The hydrocarbon condensate with the extracted products is sent further to the BR separation unit, where 3078 g / h of isobutylene, 3727 g / h of isoprene, 1090 g / h of tert-butanol, 245 g / h of isoprene precursors, 173 g / h are isolated by rectification. MDHP and 432 g / h of high boiling point by-products. Isobutylene isolated in BR in the amount indicated above is fed to the lower part of the liquid-phase reaction zone for the synthesis of isoprene P3 precursor intermediates. A stream containing the initial 36% solution of formaldehyde in water in an amount of 4584 g / h is also fed there.

The reaction zone for the synthesis of isoprene P3 precursor intermediates has a height of 1000 mm and a diameter of 100 mm, operates at a pressure of 22.0 at, a top temperature of 105 ^o C and a bottom temperature of 95 ^o C. The formaldehyde conversion is 95.0%, the formaldehyde conversion selectivity is: isoprene precursors (mainly in 4,4-dimethyldioxane-1,3) - 94.4%, in MDGP - 2.5%, in high-boiling by-products - 3.1%, isobutylene conversion is 78.0%, the selectivity for the formation of tert-butanol is 37.0%. From the top of P3, hydrocarbon and aqueous reaction layers are selected in the amount and composition presented above, which are fed to P1.

The initial isobutane-isobutylene fraction containing 46 wt.% Isobutylene in an amount of 10,000 g / h is fed into the upper part of reactor P2 for interaction with water. The P2 reactor has a diameter of 100 mm and a height of 1500 mm and is filled with the Amberlist-15 ion-exchange catalyst. The reactor P2 operates at a pressure of 22.0 at, a top temperature of 75 ^o C and a bottom temperature of 95 ^o C. In the upper part of the reactor also serves water in an amount of 451 g / h from the separator C and 1280 g / h of steam condensate. The conversion of isobutylene in reactor P2 is 75%, the selectivity for the formation of tert-butanol is 98%. The reaction mixture exfoliates at the bottom of reactor P2, exfoliated water is returned to the top of P2, and the hydrocarbon layer is sent for separation to distillation column K, where tert-butanol is recovered from it in the amount and composition described above, which is then fed to P1.

EXAMPLE 11
The synthesis of isoprene is carried out according to FIG. 2. The reaction zone for the synthesis of isoprene P1 has a height of 1000 mm and a diameter of 100 mm and has a remote boiler B. Most of the reaction zone P1 is filled with mass transfer devices - an inert nozzle.

 A stream containing an initial 36% solution of formaldehyde in water in an amount of 700 g / h is fed to the lower part of the reaction zone P1.

 A stream containing 51.7 wt.% Tert-butanol, 36.9 wt.% Isoprene precursor intermediates (mainly 4.4-dimethyldioxane-1.3), 1.1 wt.% MDHP, 0.6 wt. % of high boiling point by-products and 9.7% by weight of water are fed from the bottom of the distillation column K in the amount of 5404 g / h to the lower part of the reaction zone P1. In the lower part of the boiler B, an aqueous acidic solution containing 3.7 wt.% Phosphoric acid, 15.5 wt. % tert-butanol, 0.7 wt.% high boiling point by-products, 4.7 wt.% isoprene precursor intermediates, 1.7 wt.% formaldehyde, 0.1 wt.% MDHP and water (the rest is up to 100 wt.% ), from reactor P2.

 In the lower part of the boiler B, a part of the isobutylene isolated in the separation unit BR is also fed in an amount of 1743 g / h.

 To the zone located at a height of 500 mm in reaction zone P1, recycled tert-butanol in the amount of 1435 g / h and recycled isoprene precursors in the amount of 269 g / h are fed from the BR separation unit.

 The molar ratio of tert-butanol and formaldehyde (including those contained in intermediates) fed to the P1 + B reaction unit is 2.7: 1.

The reaction zone for the synthesis of isoprene P1 operates at a pressure of 7.0 at, a top temperature of 156 ^o C and a bottom temperature of 164 ^o C. The conversion of formaldehyde is 98.5%, the selectivity for the formation of isoprene based on the total formaldehyde (starting formaldehyde plus formaldehyde contained in the composition recycled isoprene precursor products) is 84.8%. A steam stream containing 36.1% by weight of isobutylene, 42.8% by weight of isoprene, 13.6% by weight of tert-butanol and 0.9% by weight of isoprene precursors was taken from the top of P1 in an amount of 9655 g / h 0.6 wt.% MDHP and 6.0 wt.% Water. This stream, after condensation and exfoliation of water, is directed to extraction contact with a stream discharged from the top of zone P1 in a liquid state in an amount of 17823 g / h and containing 1.8 wt.% Tert-butanol, 1.1 wt.% Isoprene precursors , 0.8 wt.% MDHP, 2.6 wt.% High boiling point by-products, 3.7 wt. % phosphoric acid and water (the rest is up to 100 wt.%). As a result of extraction from the liquid aqueous acidic stream, 97 rel.% Of high-boiling by-products are transferred to the hydrocarbon condensate and the extracted aqueous acidic stream is sent to unit O, where 4902 g / h of excess water is distilled off and the remaining aqueous acidic stream in the amount of 12,622 g / h are sent to the bottom of reactor P2.

 The hydrocarbon condensate with the extracted products is sent further to the separation unit of the BR, where 3486 g / h of isobutylene, 4145 g / h of isoprene, 1435 g / h of tert-butanol, 269 g / h of isoprene precursors are separated from it by rectification (mainly 4, 4-dimethyldioxane-1,3), 205 g / h MDGP and 473 g / h high boiling point by-products. Isobutylene isolated in BR in the amount indicated above is fed to the lower part of boiler B, the remaining part is fed to the lower part of reactor P2. A stream containing the initial 36% solution of formaldehyde in water in an amount of 5187 g / h is also fed there.

 The initial isobutane-isobutylene fraction containing 46 wt.% Isobutylene, in an amount of 10,000 g / h is fed into the lower part of reactor P2 to react with water and formaldehyde.

The P2 reactor has a height of 2000 mm and a diameter of 100 mm, operates at a pressure of 22.0 at, a top temperature of 105 ^o C and a bottom temperature of 95 ^o C. The conversion of formaldehyde is 83.0%, the selectivity of the conversion of formaldehyde into isoprene precursors (in mainly in 4,4-dimethyldioxane-1,3) - 93.6%, in MDGP - 2.9%, in high-boiling by-products - 3.5%, the conversion of isobutylene is 88.0%, the selectivity for the formation of tert-butanol is 73.0%. From the top of P2, hydrocarbon and aqueous reaction layers are selected. The aqueous layer, which is an aqueous acidic solution in the amount and composition presented above, is fed to B.

 The hydrocarbon layer is sent for separation to a distillation column K, where a mixture of tert-butanol with isoprene precursor intermediates, which in the amount and composition presented above, is fed to P1, is isolated from it as a still product.

Claims (11)

 1. A method of producing isoprene, including the liquid-phase interaction of formaldehyde and possibly substances (a), which is their source of formaldehyde, with tert-butanol and possibly isobutene in the reaction zone of isoprene synthesis in the presence of a strong acid catalyst and water at elevated temperature and molar excess of tert-butanol supplied in relation to the total amount of formaldehyde supplied to the specified reaction zone for the synthesis of isoprene and possibly emitted by the specified source of formaldehyde, with continuous distillation isoprene, isobutene and part of the water from the isoprene synthesis reaction zone and the subsequent isolation of isoprene and isobutene, characterized in that the process is carried out in a vertical reaction zone of isoprene synthesis, having a height of at least 4 times the diameter connected to the bottom of the boiler, support the pressure at which there is no condensation of isoprene, but most of the water, formaldehyde and a significant part of tert-butanol are in the liquid phase, the vapor and liquid move in the reaction zone with isoprene synthesis mainly from the bottom up, one or two liquid streams containing substances with higher boiling points than isoprene are withdrawn from the upper part of the indicated zone, and at least part of the isolated isobutene is reacted with water and the resulting tert-butanol is reused in the synthesis isoprene.  2. The method according to p. 1, characterized in that at least part of the reaction zone for the synthesis of isoprene have mass transfer devices and / or mass transfer nozzle.  3. The method according to p. 1, characterized in that the reaction zone for the synthesis of isoprene and the boiler, which is multi-tubular, are connected so that they form a single apparatus and each of the tubes of the boiler directly communicates with the reaction zone for the synthesis of isoprene, and the annular space into which heating agent, separated from her. 4. The method according to p. 1, characterized in that part of the tert-butanol and / or isobutene is possibly mixed with other hydrocarbons, subjected to transformation in the liquid-phase reaction zone for the synthesis of isoprene precursor intermediates in the presence of formaldehyde, water and a strong acid catalyst and the resulting reaction mixture possibly direct after distillation of unreacted C ₄ hydrocarbons into the reaction zone for the synthesis of isoprene and / or the boiler connected to it.  5. The method according to p. 1, characterized in that the isolated isobutene or part of it is reacted with water and possibly formaldehyde in a separate conversion zone of the isolated isobutene in the presence of a strong acid catalyst, and the resulting tert-butanol or reaction mixture is possibly fed to the reaction after distillation of isobutene an isoprene synthesis zone, and / or a boiler connected to it, and / or into a liquid-phase reaction zone for the synthesis of isoprene precursors. 6. The method according to p. 1, characterized in that the isolated isobutene or part of it is reacted with water and possibly formaldehyde in the presence of a strong acidic catalyst together with a raw isobutene-containing hydrocarbon mixture, the resulting tert-butanol or reaction mixture is preferably sent after distillation of unreacted C ₄ hydrocarbons into the reaction zone for the synthesis of isoprene, and / or the boiler connected to it, and / or in the liquid-phase reaction zone for the synthesis of isoprene precursors.  7. The method according to p. 1, characterized in that formaldehyde and / or tert-butanol and / or the reaction mixture (s) obtained by reacting isobutene and / or isobutene-containing mixture with water and possibly formaldehyde are fed by two or several streams to different levels of the reaction zone for the synthesis of isoprene, but not higher than 3/4 of its height.  8. The method according to PP. 1-5, characterized in that the acidic catalyst is a strong acid, preferably in the presence of a corrosion inhibitor (s) or acidic cation exchanger.  9. The method according to p. 1, characterized in that from the upper part of the reaction zone for the synthesis of isoprene a liquid stream is removed, containing mainly water and a strong acid catalyst, which is preferably after peeling off insoluble organic substances and possibly after extraction of high-boiling by-products with substances or mixtures, not generators with a water-acid flow of a homogeneous mixture are sent to the lower part of the reaction zone for the synthesis of isoprene, and / or the boiler connected to it, and / or the zone (s) of interaction of isobutene with water, and / or the synthesis zone of isoprene precursors.  10. The method according to p. 1, characterized in that the process in the reaction zone of isoprene synthesis is carried out in the presence of a high boiling inert solvent that does not form a homogeneous mixture with water, and a liquid stream containing said inert solvent and high boiling liquids is removed from the upper part of the reaction zone of isoprene synthesis by-products.  11. The method according to p. 1, characterized in that when using a strong acid as a catalyst in an aqueous solution, at least part of the specified solution is distilled off excess water in a separate apparatus, after which the solution is again used in the process.

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