JPS60243031A - Production of isoprene - Google Patents

Abstract

PURPOSE:To produce isoprene from an isobutylene source and a formaldehyde source, economically, under specific condition, by using inexpensive spent BB fraction as the isobutylene source, and subjecting the source to the low-temperature reaction step, 4C compound removal step, high-temperature reaction step and purification step. CONSTITUTION:An isobutylene source is made to react with a formaldehyde source continuously in a liquid phase in the presence of an acidic catalyst and water to obtain isoprene. In the above process, the butane-butene fraction containing isobutylene and produced as a by-product of the catalytic cracking of petroleum is used as the isobutylene source, and is subjected to (1) the low-temperature reaction step 4 comprising the synthesis of isoprene precursor by reacting with a formaldehyde source at 50-140 deg.C, (2) the 4C compound removal step 13 to remove the 4C hydrocarbon from the liquid obtained by the step (1), (3) the high-temperature reaction step 16 to decompose the isoprene precursor in the liquid obtained by the step (2) to isoprene at 145-230 deg.C, and (4) the purification step 23 to purify the produced isoprene. Isoprene can be produced efficiently from an inexpensive raw material with a simple apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing isoprene by a liquid phase method, and more specifically, the present invention relates to a method for producing isoprene by a liquid phase method, and more specifically, a butane-butene fraction (hereinafter referred to as
A method for producing isoprene from formaldehyde and an isobutylene source such as inbutylene, tert-getanol, methyl tert-butyl ether and formaldehyde by a general liquid phase method is known. It is. In this case, it is common to use a highly purified source of inbutylene.
There have been few attempts to directly use the Spen) BB fraction, which is commercially available at low cost, as an isobutylene source.

Therefore, the present inventors conducted intensive studies to develop a new inglene synthesis process using spent BB fraction as an inbutylene source, and found that if a specific process is adopted,
The inventors discovered the possibility of using fraction B as an inbutylene source and completed the present invention.Thus, according to the present invention, an inbutylene source and a formaldehyde source are continuously mixed in the presence of an acidic catalyst and water. When manufacturing imprene through a liquid phase reaction, the manufacturing process includes imbutylene (spen); a low temperature reaction step (4) in which the BB fraction and a formaldehyde source are reacted in the presence of water to synthesize an isogrene precursor; A C4 removal step (B) in which 04 hydrocarbons are removed from the liquid derived from the process, a high temperature reaction step (B) in which the isoprene precursor in the liquid derived from this process is decomposed into isogrene.
), and a purification step (c) of refining the produced isoprene.

In the present invention, in the first step, the Spen) BB fraction and formaldehyde water bath liquid are fed together with an acidic catalyst to a low temperature reaction zone, and a liquid phase reaction is carried out at a temperature of 50 to 140°C in the presence of water (hereinafter referred to as low temperature reaction). ). The reaction pressure is increased to such an extent that the inside of the system is in a completely liquid phase state. Further, water is used in an amount of about 1 to 100 times the weight of formaldehyde.

In this step, 4,4-tmethyl-1,
Isogrene precursors such as 3-.quaxane, 3-methyl-1,3-butanediol, 3-methyl-3-buten-1-ol, 3-methyl-2-buten-1-ol, etc. are synthesized. C4 hydrocarbons other than isobutylene are
There is virtually no reaction in this step. At this time, t
- Isoprene precursors are formed more easily when alcohols such as butanol are added. In addition, in this reaction step, it is desirable to have a conversion rate of formaldehyde of 90% or more.The formaldehyde source used in the O reaction may be any source that can generate formaldehyde in the reaction system, and a specific example is methanol. Gases containing formaldehyde sources obtained by the oxidation of
3-soxane, glycol formal), etc. In addition, paraformaldehyde is dissolved in a formaldehyde aqueous solution to increase the formaldehyde content,
An aqueous formaldehyde solution containing methanol as a stabilizer can be used similarly.

Among these, 1 mol of formaldehyde is preferred from the viewpoint of ease of handling, availability, and the need for water in the reaction system.◎ The ratio of isobutylene and formaldehyde sources to be used is selected as appropriate depending on the reaction conditions. However, a range of from 0.5 to 2 moles of imbutylene in the Spen) BB fraction per stoichiometric mole of formaldehyde originating from the formaldehyde source is usually preferred.

Further, the acidic catalyst may be any substance that exhibits acidity in the presence of water, and specific examples thereof include sulfuric acid, phosphoric acid, and sulfuric acid.
Radruenesulfonic acid and the like are exemplified.

The reaction product liquid derived from the low temperature reaction step is fed to the 04 removal step to remove C4 hydrocarbons. The C4 removal step is not particularly limited as long as it can remove unreacted inbutylene, n-butene, and butanes, but is usually carried out as follows.

That is, the derived liquid is separated into an oil layer and an aqueous layer, an unreacted C4 hydrocarbon mixture is separated from the oil layer by distillation, and the resulting high-boiling substances are supplied to a low-temperature reaction process. On the other hand, the aqueous layer is sent to a high temperature reaction step after slightly dissolved C4 hydrocarbons are removed by evaporation if necessary. Of course, it is also possible to adopt a method in which C4 hydrocarbons are selectively removed by directly flushing the effluent into the pond of this method.

In the present invention, it is an essential requirement to provide this step (B), thereby stabilizing the reaction in the next step and making it possible to reduce the size of the reactor. is then supplied to a high temperature reaction zone to carry out a liquid phase reaction at a temperature of 145 to 230°C (hereinafter referred to as
(referred to as high temperature reaction). The reaction pressure is selected to be sufficient to maintain a liquid phase in the system. In this step, isogrene is produced by decomposition of an isoprene precursor produced by a low-temperature reaction.

During the high temperature reaction, a new source of inbutylene such as inbutylene and t-butanol is supplied as needed.

The amount supplied is preferably about 1 to 20 moles per mole of formaldehyde supplied as a raw material to the low-temperature reaction. Such an inbutylene source may be newly introduced from outside the system, but
Normally, the liquid recovered from the latter reactor in the next purification step is recycled and used. Therefore, once it is charged at the beginning of the reaction, it will not be consumed after that, but there is no problem in supplying it from outside the process if necessary. In such a high temperature reaction process, all formaldehyde is consumed in the reaction, And the isogrene precursor is efficiently converted to isoprene.

The effluent from the high temperature reaction step is then sent to a purification step,
Here, isoprene is purified. First, the derived liquid is separated into an oil layer and an aqueous layer, and isobutylene, isoprene, t-butanol, and high-boiling substances contained in the oil layer are separated by distillation according to the following order, and the recovered imbutylene and recovered t-butanol are , if necessary, are recycled to the above-mentioned high temperature reaction step.

On the other hand, the aqueous layer is returned to the low-temperature reaction step after water and t-butanol are evaporated as necessary to concentrate the catalyst concentration.

The present invention will be described in detail below with reference to the drawings, but the present invention is not limited thereto.

First, the Sven) BB fraction was passed into the low temperature reactor 4 through the tube 1,
An aqueous formaldehyde solution is supplied through tube 2 together with the catalyst water bath liquid from tube 3 to cause a reaction. The liquid discharged from the low temperature reactor is connected to decanter 6 via 5G5. Here, the reactor is separated into an oil layer and an aqueous layer. The oil layer consists of unreacted C4 hydrocarbons, 1-butanol, and isogrene precursors, and is supplied through pipe 8 to C4 distillation column 13, and unreacted C4 is taken out of the system through pipe 11 from the top of the column. On the other hand, the bottom liquid consisting of t-butanol and isogrene precursors is withdrawn through pipe 14 and supplied to high temperature reactor 16. The aqueous layer of the decanter 6 is fed to the degassing tower 10 via a small amount of unreacted C4 hydrocarbons, t-butanol, isoprene, aggregate, water, and catalyst at a concentration of %'7. Unreacted C4 hydrocarbons are taken out of the system through a pipe 9 at the top of the tower, while an aqueous catalyst solution containing t-butanol and isogrene precursors is supplied to a high-temperature reactor 16 through a pipe 15 at the bottom of the tower. Recovered t-butanol is introduced into the high temperature reactor 16 through pipe 27, and recovered isobutylene is supplied through pipe 22. The liquid discharged from the high temperature reactor 16 is introduced into a decanter 17 and separated into an oil layer and an aqueous layer. The oil layer contains isobutylene, imprene, t-butanol, and high-boiling substances, which are supplied to the inbutylene distillation column 20 to recover isobutylene from the top of the column. supplying the bottom liquid to the isogrene precursor 23 through the pipe 21;
High purity inbre/ is obtained from the top of the column. The bottom liquid is supplied to a t-butanol distillation column 26 through a pipe 25, and t-butanol is recovered from the top of the tower.
On the other hand, high-boiling substances are removed from the bottom of the column through a pipe 28.

The aqueous layer from the decanter 17 is aqueous with a catalyst aqueous solution containing a small amount of t-butanol, which, after being subjected to treatments such as concentration as necessary, is circulated through a pipe 18 to the low-temperature reactor.

Thus, according to the present invention, isoprene can be efficiently obtained with simple equipment using the inexpensive Sven)BB fraction as a raw material.

Next, Q
In addition, the parts in the examples are based on the weight of a continuous hook, and the numbers indicate the amount supplied per hour.

Example 1 (A) Low temperature reaction step: Spen containing 1150 parts of imbutylene in the low temperature reactor) B
Circulating catalyst liquid 6 from the purification process (c) consisting of 92,500 parts of BW, 1,178 parts of formaldehyde water containing 589 parts of formaldehyde, 390 parts of t-butanol, 5,000 parts of water, 1,250 parts of phosphorus, and 140 parts of sodium phosphate.
780 parts were continuously fed, the reaction temperature was 100°C, and the pressure was 2.
The reaction was carried out with stirring at a dyeing rate of 5 Y/a12 and a residence time of 50 minutes.

(B) C4 removal step: Step (The liquid derived from N is separated into an oil layer and an aqueous layer in a decanter. The oil layer is a BB containing unreacted isobutylene butane.
1400 parts of distillate, 310 parts of t-butanol, 900 parts of isozolene pre-collection, this is a C4g distillation column (packed column, pressure 4!I/cIn2, top 35℃, bottom 99℃)
1,400 parts of BB fraction was extracted from the top of the column.
The remainder of the pot is introduced into the next high temperature reaction step (C). The water layer in the decanter is separated from the degassing tower (empty tower, 100℃, 3kg/cr
After degassing in step n2), it is supplied to a high temperature reaction process.

(Q high-temperature reaction step: In a high-temperature reactor (packed tower), the liquid derived from the 04 removal step (B) and about 2 t-butanol recovered from the purification step (2) are
500 parts and about 5900 parts of imbutylene were supplied, reaction temperature was 160°C, pressure was 40 kg7cm2, and residence time was 30.
The reaction was carried out in minutes.

(2) Purification step: The liquid derived from step (C) is separated into an oil layer and an aqueous layer in a decanter. The separated oil layer was supplied to an inbutylene distillation column (packed column 5 kg/crn2, column top 48°C, column bottom 109°C), and isobutylene was recovered from the top of the column and recycled to the high temperature reaction step. Further, the bottom liquid derived from the bottom of the column was supplied to an isoprene distillation column (packed column, 0.2 kl/crn2, top of the column: 36°C, bottom of the column: 85°C), and 1000 parts of isoprene was distilled from the top of the column. The purity was 99.7%, and the yield based on formaldehyde was 74.6%. In addition, the bottom liquid derived from the bottom of the column is supplied to a t-butanol distillation column (packed column, normal pressure, top of the column: 79°C, bottom of the column: 135°C), and t-zotanol is recovered from the top of the column, which is then subjected to a high-temperature reaction. It was recycled to the container. The aqueous layer obtained from the 1 m decanter was concentrated and then circulated to the low temperature reaction step.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing a specific example of the present invention. 4...Low temperature reactor, 6...Decanter-113...
C4 distillation column, 16... high temperature reactor, 17... decanter 120... inbutylene distillation column, 24... isoprene distillation column, 26... t-butanol distillation column. Patent applicant Zeon Corporation

Claims (1)

[Claims] 1. When manufacturing isoprene by continuous liquid phase reaction of an imbutylene source and a formaldehyde source in the presence of an acidic catalyst and water, the manufacturing process includes imbutylene). Low-temperature reaction step (4) to synthesize isoprene precursor by reacting with
, a C4 removal step (B) for removing C4 hydrocarbons from the liquid derived from this process, a high temperature reaction process (C) for decomposing the isoprene precursor in the liquid derived from this process into isoprene, and a purification process for refining the produced isoprene. (b) A method for producing isoprene, characterized by comprising: