TW201522320A - Process for removal of 1,2-epoxy-5-hexene from epichlorohydrin - Google Patents

Abstract

This invention concerns a process to remove 1,2-epoxy-5-hexene from epichlorohydrin which is produced by oxidation of un-purified allyl chloride comprising at least 1,5-hexadiene as impurity.

Description

Method for removing 1,2-epoxy-5-hexene from epichlorohydrin

The present invention relates to a process for removing 1,2-epoxy-5-hexene from epichlorohydrin, which is an unpurified allylic group containing at least 1,5-hexadiene as an impurity. Oxidation of the base chlorine.

Epichlorohydrin (ECH) is currently prepared from allyl chloride, chlorine and water followed by alkaline treatment (dehydrochlorination) to prepare ECH. Using this approach, ECH is contaminated with trichloropropane (TCP), which can cause problems when ECH is used in epoxy resin preparation. TCP is also a toxic compound and is harmful to the environment.

A good solution to avoid the presence of TCP is to prepare ECH by direct epoxidation of allyl chloride double bonds. However, the industrial grade allyl chloride used to prepare epichlorohydrin (ECH) contains impurities: 1,5-hexadiene.

When ECH is prepared by epoxidation of the allyl chloride, a portion of this impurity is converted to 1,2-epoxy-5-hexene. Unfortunately, 1,2-epoxy-5-hexene has a boiling point of 118 to 121 ° C and therefore cannot be separated from ECH (boiling temperature 118 ° C) by rectification.

When unreacted allyl chloride and its impurities are recycled in the process, the problem of 1,2-epoxy-5-hexene is enlarged in the process. Most of the 1,5-hexadiene was converted to 1,2-epoxy-5-hexene in these processes.

US 4,127,594 describes a method for purifying ECH by selective hydrogenation of olefinic impurities Effective method. The 5,6-epoxyhexene-1 present in a small amount in ECH is selectively converted by hydrogenation in the presence of a catalyst, and the minimum ECH is accompanied by destruction. The catalyst includes deposition on non-acidic, fire-resistant On the support, ruthenium, platinum or palladium. This process converts the unsaturated compound to its saturated analog and thereby removes the double bond, which is prone to side reactions in the subsequent preparation and use of the epoxy resin. However, since there is no detectable change in the boiling point of the new product formed after hydrogenation, it remains in the ECH after rectification.

More recently, CN 102417490 provides a process for purifying ECH containing 1,2-epoxy-5-hexene. In this reference, the contaminant 1,2-epoxy-5-hexene is treated with chlorine or bromine at a temperature in the range of 5 to 30 °C. The 1,2-epoxy-5-hexene is subsequently converted to a product having a significantly higher boiling temperature. The residual halogen was then removed by flushing with nitrogen. Subsequently, rectification is used to obtain an ECH having a purity higher than 99.8%.

The method of CN' 490 is a quality method. On the other hand, it has some obvious drawbacks. This method reduces the overall yield of the process due to the fact that the intermediate formed during the chlorination of 1,2-epoxy-5-hexene can attack the ECH to produce an addition product.

Furthermore, the reaction is carried out in a separate reactor where halogen is added to the ECH. Therefore, additional reactor equipment is required, thereby increasing capital costs. Chlorinated organic compounds are also formed which are generally environmentally harmful and have no direct application. The reaction is carried out at a temperature that requires active cooling of the ECH, even below ambient temperature. According to this reference, the reaction temperature is 0 to 30 ° C, preferably 0 to 15 ° C, more preferably 0 to 5 ° C.

In addition, this reference teaches in particular that an excess of halogen (halogen/1,2-epoxy-5-hexene ratio between 1/1 and 3/1) must be used.

Again, after the reaction, the excess halogen must be removed (here by passing nitrogen). This nitrogen stream needs to be treated to remove the halogen prior to release to the atmosphere. Therefore, this method has potential contamination problems. This will further increase the complexity and cost.

The inventors set out to solve the problem of impurities containing 1,5-hexadiene by an alternative method that is more economical, requires lower investment, and can be used to produce valuable by-products rather than waste. Allyl chloride causes problems.

Accordingly, the present invention provides a process for removing 1,2-epoxy-5-hexene and 1,5-hexadiene from ECH by the following method: a) catalytic oxidation by hydrogen peroxide is not purified a mixture of epichlorohydrin whereby at least 50 mole % of the 1,2-epoxy-5-hexene 1,5-hexadiene is further converted to 1,2,5,6-diepoxide Hexane and b) if necessary, remove the light boiling component from a) and c) further remove 1,2,5,6-diepoxide by the rectification step.

More specifically, the present invention provides a process for removing 1,2-epoxy-5-hexene from ECH, which is obtained by oxidation of unpurified allyl chloride, which comprises at least With 1,5-hexadiene of more than 0.05% by weight of 1,5-hexadiene as an impurity, the method is achieved by: a) comprising at least allyl chloride, ECH, 1,5-hexane a mixture of alkene, 1,2-epoxy-5-hexene is contacted with hydrogen peroxide and a transition metal complex-containing compound as a catalyst, b) unreacted allyl chloride is separated by distillation, unreacted 1,5-hexadiene and other low boiling components, c) separating 1,2,5,6-diepoxide from ECH and 1,2-epoxy-5-hexene by distillation and Possible other high boiling components.

The present invention allows the use of 1,5-hexadiene-contaminated allyl chloride starting materials in the epoxidation process. The product of this contaminant is 1,2,5,6-diepoxide, also known as 1,5-hexadiene diepoxide. 1,2,5,6-diepoxide has a boiling point of 188 ° C (62 ° C under a reduced pressure of 300 mm Hg). Therefore, its boiling point is clearly distinguished from ECH, which facilitates the separation of the product. 1,2,5,6-diethylene oxide can be used, for example, in a resin composition. The latter is a significant advantage over other processes such as chlorination, and the product formed by chlorination is considered useless.

Step (a) is preferably carried out by contacting an organic phase comprising at least a mixture of allyl chloride, epichlorohydrin, 1,5-hexadiene and 1,2-epoxy-5-hexene. The preferred oxidizing agent for this reaction is hydrogen peroxide. Other oxidizing agents (i.e., as a precursor to hydrogen peroxide) may be used, but hydrogen peroxide is preferred as the oxidizing agent in view of availability and environmental impact. Hydrogen peroxide has strong oxidizing properties. It is usually used in the form of an aqueous solution.

The oxidizing catalyst is preferably selected from transition metal catalysts which are active in an oxidation reaction or an epoxidation reaction using hydrogen peroxide as an oxidizing agent. Typical catalysts contain transition metals such as manganese, tungsten, titanium, molybdenum, niobium, silver, vanadium and iron.

The oxidation reaction is more preferably carried out using a homogeneous catalyst such as manganese or tungsten. However, there are many different suitable catalysts which have good solution in water or organic phase, desired reactivity to epoxidation and stability against decomposition. One of ordinary skill can obtain examples from review articles and books such as "Mechanisms in homogenous and heterogeneous epoxidation catalysis, T.S. Oyama."

A preferred catalyst class comprises a manganese complex complexed with a recycled nitrogen-containing compound, preferably containing a third substituted nitrogen ligand.

Another preferred class of catalysts includes the tungsten salt or its acid in the presence of phosphate. Phosphotungstate or its acid can also be used. These compounds are used in the absence of an organic ligand but in the presence of a phase transfer reagent. One of ordinary skill in the art can obtain variations in this tungsten-based catalytic epoxidation system from review articles or books such as "Modern Oxidation Methods, Jan-Erling Bäckvall" or "Mechanisms in homogenous and heterogenous epoxidation catalysis, T.S. Oyama." To ensure optimal oxidant efficiency, the oxidant is preferably added to the aqueous reaction medium at a rate equal to the rate of reaction of the catalytic oxidation. The catalytic oxidation reaction can be carried out in a batch process, in a continuous process or in a semi-continuous process. Preferably, step (a) is carried out in a conventional stirred tank reactor provided with a stirring member. The catalyst, aqueous reaction medium, and reactants may be added in portions or the reactants may be added over a period of time. If hydrogen peroxide is added during the reaction, it is added (mixed) to contain crude The organic phase of ECH or (stirred) aqueous reaction medium. In (semi) continuous operation, various recycle streams can be used to control reaction conditions and optimize production rates. In terms of process design, a settler can be added to optimize the gravity separation of the organic phase containing ECH. Also, membrane units can be used to recycle the aqueous reaction medium and reduce catalyst losses. The reaction is carried out at or above atmospheric pressure. As long as the reaction mixture is substantially maintained in a non-gaseous phase, the precise pressure is not critical. Typically the pressure will vary from about 1 to about 100 atmospheres. After step (a), the product comprising the crude ECH undergoes rectification steps (b) and (c). Distillation conditions, such as distillation and fractionation, are known in the art.

Preferably, unreacted allyl chloride (for recycle purposes) and light ends, such as 1,5-hexadiene, chloropropane and chloropropene, are first part of step (b) from crude ECH. One or more stages are removed. A typical ECH network (the crude product after the reaction) is as follows:

The crude ECH is subjected to distillation, preferably in a multi-well plate column, a blister plate column and/or a packed column. This can be a single column or a series of columns. The column is preferably provided with an evaporation or heating device (or evaporation or heating zone or zone) located at or near the bottom of the column (or below the first plate). It is provided with a member for introducing a feed stream at a point between the bottom and the top of the column, a member for extracting a low-boiling stream at or near the top of the column, and extracting a high-boiling stream at or near the bottom of the column. A member and a component that may extract a product stream at an intermediate point of the column.

Preferably, the low boiling point stream continues at the top of the column and the high boiling point stream continues to the column. Pull out at the bottom. Subsequently, 1,2,5,6-diepoxy-hexane and other heavy fractions having a boiling point higher than 118 ° C (for example, components such as monochlorohydrin and dichlorohydrin) are separated from the ECH. This process is again carried out in a distillation column or series of columns, but is operated at lower pressures and/or higher temperature conditions relative to lighter fraction removal conditions. In addition, the product is withdrawn at the top of the column or at an intermediate point between the feed point and the top of the column.

TCP is not detectable in this crude ECH. Further purification by distillation resulted in an ECH purity above 99% and further optimization to an ECH purity of 99.5%. According to the invention, the 1,2-epoxy-5-hexene in the ECH is converted to a higher boiling product by epoxidizing the monoepoxide to the corresponding diepoxide. This contaminant can be effectively removed by ensuring that 1,2-epoxy-5-hexene is converted to a high boiling product. In addition, this can result in the formation of 1,2,5,6-diepoxide, which can be completely separated and formed to replace the attractive epoxy-like products.

In a preferred embodiment, the reaction conditions during the epoxidation of the crude ECH are such that at least 45 mole % of the contaminant 1,5-hexadiene is converted to 1,2,5,6-diepylene oxide and thereby It can be collected in a fraction having a higher boiling point relative to ECH during distillation.

The desired reaction conditions according to the present invention are such that the continuous reaction rate is such that the reaction rate of 1,2,5,6-dihexylene oxide formed from 1,2-epoxy-5-hexene is 1, 5-hexadiene produces at least 0.50 times the reaction rate of 1,2-epoxy-5-hexene. One of ordinary skill in the art can obtain their conditions from theoretical analysis, such as those explained in Chemical Reactor Development, Dirk Thoenes, or changes in reactor type and reaction conditions such as ratio or residence time.

The optimum reaction conditions for maximizing the removal of 1,2-epoxy-5-hexene can result in a decrease in the peroxide yield defined as the molar ratio of the produced ECH to the hydrogen peroxide added. It may also result in a decrease in the number of flows of the generated ECH compared to the molar ratio of the added catalyst. Without being bound by any particular theory, it is reasonable to assume that the high conversion of 1,2-epoxy-5-hexene to 1,2,5,6-dione oxide is lower than that of the allyl chloride in the reaction medium. Concentration-related, which makes the side reactions of epoxidation more favorable, such as decomposition of peroxides and ECH Decomposition.

Therefore, the present invention can be optimally carried out when the removal rate of 1,2-epoxy-5-hexene is high, while the yield and the decrease in TON are almost no.

The invention of removing 1,2-epoxy-5-hexene via an epoxidation reaction can be combined with other techniques well known in the art. This includes the "exudation" of the allyl chloride recycle stream to remove low-boiling by-products from the preparation of allyl chloride, which will accumulate or chlorinate the 1,2-ring remaining in the epichlorohydrin. Oxy-5-hexene.

Since ECH synthesis is avoided by the addition of chlorine to allyl chloride and chlorination of allyl chloride by ECH, the latter ECH and all its derivatives will not contain detectable amounts of TCP, even in the coarsest grade or grade. . Since the main impurities 1,2-epoxy-5-hexene and 1,2,5,6-diepoxide contain (for example, ECH) epoxy groups, such compounds will be built into the derivative and thus It does not seep around when applied as an epoxy resin.

The following examples will more fully illustrate selected embodiments of the invention. All parts, percentages and ratios referred to herein and in the accompanying claims are by weight unless otherwise indicated.

Instance Example 1:

In a typical continuous reaction, the flow rate of the components was 0.24 moles per hour of hydrogen peroxide, 9.0 micromoles per hour of catalyst, 2.5 millimoles per hour of oxalic acid, and 0.79 moles per hour of crude ECH. The pH is maintained between pH 3.2 and 4.0. The temperature was set at 15 ° C and the reaction volume was controlled at about 200 ml. The catalyst used was [Mn ₂ (μ-O) ₃ {1,4,7-trimethyl-1,4,7-triazacyclononane} ₂ ] ²⁺ salt. The starting allyl chloride contained 0.4% by weight of 1,5-hexadiene as a starting material to prepare a crude ECH. This resulted in a steady state yield of 72% based on the added peroxide and a diepoxide/monoepoxide (DO/BO) ratio of 1.

Example 2:

As in Example 1, but allyl chloride contains 1.2% by weight of 1,5-hexadiene as a starting material. To prepare a crude ECH. This resulted in a steady state yield of 69% based on the added peroxide and a ratio of DO/BO of 1.

Example 3:

As in Example 1, allyl chloride contained 1.2% by weight of 1,5-hexadiene and the allyl chloride flow rate was 0.316 moles/hour. This resulted in a steady state yield of 72.9% based on the added peroxide, a flow number of 19,300 and a DO/BO ratio of 3.

Example 4:

The crude epichlorohydrin (126 g) containing 0.2% by weight of 1,2-epoxy-5-hexene was contained in 0.1 ml of 35 wt% hydrogen peroxide, [Mn ₂ (μ-O) ₃ {1 , 4,7-trimethyl-1,4,7-triazacyclononane} ₂ ] ²⁺ salt (240 mmol) and oxalic acid (20 mmol) in an aqueous medium (125 ml). A 35 wt% hydrogen peroxide solution was added at 30 ° C for 10 minutes at a rate of 4 ml/h. The pH was controlled between 3.4 and 3.8 by the addition of a small amount of oxalic acid and NaOH. The conversion of 1,2-epoxy-5-hexene by oxidation was 91%. The purity of ECH was >99.7 wt%.

Example 5:

As in Example 4, but using 25 ml of aqueous phase. The conversion of 1,2-epoxy-5-hexene by oxidation was 55.4%. The purity of the ECH is >99.5% by weight.

Example 6:

As in Example 4, but using 26 grams of ECH. The conversion of 1,2-epoxy-5-hexene by oxidation was 98%. The purity of the ECH was >99.8% by weight.

Example 7:

A solution of 1.2% by weight of allylic chloride (50 ml) of 1,5-hexadiene and 25 ml of hydrogen peroxide (35 wt%) was reacted in 150 ml of water. Add phosphotungstic acid and Aliquat® 128 and control the pH at pH 2. After 2 hours at 35 ° C, the organic phase was removed from the mixture and analyzed by gas chromatography. The organic phase contained 22% by weight of ECH and had a DO/BO ratio of 1.23.

Example 8:

The products of the organic phases of Examples 1 to 7 can be further purified by distillation according to the method given in the above description. The crude composition of the organic phase has the average composition given in the following table:

Distillation can be performed to further remove light (allyl chloride) and heavy boiling components. The distillation was carried out at 60 ° C under reduced pressure. The pressure is slowly reduced to obtain the purity of the ECH. The obtained ECH has the following composition, as measured by gas chromatography.

Example 9:

This ECH distillation can be further optimized. A typical technician can use Aspen simulation software to optimize the distillation. This optimization of the distillation from the mixture of Example 1 can result in the following composition:

The ECH purity obtained by the method given in the above examples was higher than 99.10% by weight and contained no trichloropropane.

Claims (15)

A method for removing 1,2-epoxy-5-hexene and 1,5-hexadiene from epichlorohydrin via 1,5-hexane having more than 0.05% A catalytic epoxidation reaction of an allyl chloride, which is achieved by the following steps: a) catalytically oxidizing the unpurified epichlorohydrin mixture with hydrogen peroxide, thereby at least 50 mole percent The reaction is 1,2-epoxy-5-hexene, 1,5-hexadiene is further converted to 1,2,5,6-diethylene oxide, and b) the light is removed from a) as appropriate The boiling component, and c) further removing 1,2,5,6-diepoxide by a rectification step. The method of claim 1, wherein the content of 1,2-epoxy-5-hexene in the isolated epichlorohydrin is less than 1.0% by weight. The method of claim 1, wherein the crude product before distillation contains at least 0.02% 1,2,5,6-diepoxide. The method of any one of claims 1 to 3, wherein the method is a continuous method and a molar ratio of 1,2,5,6-diepoxide to epichlorohydrin in the post-oxidation stream is a pre-oxidation stream The molar ratio of 1,5-hexadiene to allyl chloride is at least 0.45 times. The method of any one of claims 1 to 3, wherein the method is a batch method and a molar ratio of 1,2,5,6-diethylene oxide to epichlorohydrin at the end of the reaction The molar ratio of 1,5-hexadiene to allyl chloride is at least 0.45 times. An epichlorohydrin obtainable by the method of any one of claims 1 to 3, which has at least 97.5% by weight of epichlorohydrin and 0.689 to 0.001% by weight of allyl chloride and 0.059 to 0.001 by weight. % of butenyl ethylene oxide (BO) and from 0.047 to 0.001% by weight of 1,2-bis(oxiran-2-yl)ethane (DO) and undetectable trichloropropane. The epichlorohydrin of claim 6 which is further purified by distillation, which has the following Composition: at least 99.10% by weight of epichlorohydrin and 0.4 to 0.001% by weight of allyl chloride and 0.06 to 0.002% by weight of butenyl oxide (BO) and less than 0.006% by weight of 1,2- Di(ethylene oxide-2-yl)ethane (DO) and undetectable trichloropropane. The method of any one of claims 1 to 3, wherein the catalytic oxidation reaction is carried out at least in the presence of an aqueous medium. The method of any one of claims 1 to 3, wherein the catalytic oxidation comprises a homogeneous catalyst. The method of claim 9, wherein the homogeneous catalyst contains manganese. The method of claim 10, wherein the manganese compound contains a tertiary substituted nitrogen ligand. The method of claim 9, wherein the homogeneous catalyst contains tungsten. The method of claim 12, wherein the cationic phase transfer reagent is used in addition to the catalyst. The method of any one of claims 1 to 3, wherein the rectifying step is accomplished by fractional distillation. A use of purified 1,2,5,6-diepoxide as claimed in claim 12 in a resin composition.