JP4503021B2 - Process for producing N-vinylcarbazoles - Google Patents

Description

  The present invention relates to a method for producing N-vinylcarbazoles.

  N-vinyl carbazoles are very useful as a dye synthesis intermediate, a photoconductive material synthesis intermediate, a monomer for producing a thermoplastic resin, or the like.

  As a method for producing N-vinylcarbazole, a method in which carbazole and acetylene are reacted in a liquid phase is known as disclosed in, for example, JP-A-48-68564. However, since this method handles acetylene at high pressure, there is a risk of decomposition and explosion of acetylene, and sufficient safety measures are required from the viewpoint of facilities and operation. Moreover, since this reaction is a batch reaction, it cannot be said to be a method suitable for industrial production.

  On the other hand, as a method not using acetylene, for example, JP-A-49-9468 discloses a method for producing N-vinylcarbazole by dehydrating N- (2-hydroxyethyl) carbazole in the presence of a base. It is disclosed. However, since this reaction is also a batch reaction, productivity is low and it cannot be said that it is a method suitable for business. In addition, it is difficult to process strong base substances produced by the reaction.

  Japanese Patent Application Laid-Open No. 2002-220371 discloses a method for producing N-vinylcarbazole by deriving a hydroxyl group of N- (2-hydroxyethyl) carbazole to sulfonate and then removing the sulfonate in the presence of a base. It is disclosed. However, this method requires many steps for the treatment of the sulfonic acid derivative produced by the reaction in addition to many reaction steps and complicated operations.

  Further, JP-A-8-141402 uses tertiary N- (2-hydroxyalkyl) carboxylic acid amides as raw materials, and tertiary N-alkenylcarboxylic acid amides by intramolecular dehydration in the gas phase. A method of manufacturing is disclosed. However, the N- (2-hydroxyalkyl) compound used as a raw material in this method is a carboxylic acid amide and is different from N- (2-hydroxyethyl) carbazoles. In this document, an example of supplying the raw material in a gaseous state to the reactor is shown as an example, but there is no example of supplying the raw material to the reactor in a liquid state.

  Furthermore, JP-A-9-291069 uses an N- (1-alkoxyalkyl) compound as a raw material, and uses a solid oxide containing phosphorus and an alkali metal and / or an alkaline earth metal as a catalyst. And a method for producing an N-vinyl compound by dealcoholization reaction in a gas phase is disclosed. However, the N- (alkoxyalkyl) compounds shown here have a leaving group at the α-position, and the leaving group is an alkoxy group and does not correspond to N- (2-hydroxyethyl) carbazoles. Furthermore, since it is necessary to separate alcohols by-produced by the reaction, the process becomes complicated.

  The present invention has been made paying attention to the circumstances as described above, and its purpose is that there is no danger due to high-pressure conditions or the use of explosive substances, and the post-treatment such as waste treatment derived from by-products. The object is to establish a method that can produce N-vinylcarbazoles efficiently by a continuous method that is less problematic and suitable for industrialization.

  The production method of the present invention that was able to solve the above-mentioned problems is represented by the following general formula (1)

[Wherein R ^{1 to} R ⁸ each independently represents hydrogen or a substituent inert to the reaction]
In the presence of a catalyst, N- (2-hydroxyethyl) carbazoles were subjected to intramolecular dehydration reaction in the gas phase, and the following general formula (2)

[Wherein R ^{1 to} R ⁸ represent the same meaning as described above]
The present invention is summarized in that it is converted to N-vinylcarbazoles represented by

  According to the present invention, there is no danger due to the use of high-pressure conditions and explosive substances in the prior art, and there are few problems in post-treatment such as waste treatment derived from by-products, and N-by a continuous process suitable for industrialization. Vinylcarbazoles can be produced efficiently.

It is a conceptual diagram which shows one Example of this invention.

  The present invention relates to a method for obtaining N-vinylcarbazole by using N- (2-hydroxyethyl) carbazole as a raw material and subjecting it to intramolecular dehydration reaction in the gas phase as described above. This synthesis reaction is represented by the following formula.

[Wherein R ^{1 to} R ⁸ each independently represents hydrogen or a substituent inert to the reaction]
In the above definition, the “substituent inert to the reaction” refers to a substituent that does not adversely affect the reaction of intramolecular dehydration of N- (2-hydroxyethyl) carbazoles (1) by heating in the presence of a catalyst. . Examples of such a substituent include a halogen atom, a lower (C _1-6 ) alkyl group, a lower alkoxy group, a cyano group, and a nitro group.

 In general, when carrying out a gas phase synthesis reaction, a method is adopted in which a raw material is vaporized by an evaporator and then introduced into the reactor. However, since N- (2-hydroxyethyl) carbazoles used as a raw material in the present invention have a very low vapor pressure, it is difficult to vaporize with an evaporator. However, if this is vaporized by a method as described later and then passed through a suitable catalyst packed bed, the dehydration reaction proceeds rapidly, and N-vinylcarbazoles can be easily obtained in high yield.

  That is, in the present invention, in order to efficiently evaporate N- (2-hydroxyethyl) carbazoles having a low vapor pressure and rapidly proceed the gas phase reaction, the raw material is preferably diluted with a solvent to lower the concentration of the raw material compound. Thus, the partial pressure is lowered, and the diluted solution is directly vaporized by supplying it directly to the reactor, and is brought into contact with the catalyst charged in the reactor in a gas phase.

  At this time, the raw material solution diluted in the solvent can be heated and evaporated in advance and then supplied to the reactor. However, when this method is adopted, when the raw material solution is heated and evaporated with an evaporator, etc., the difference in vapor pressure between the raw material and the solvent is too large, so even if all of the solvent is vaporized, most of the raw material is vaporized. Do not remain. In addition, in order to completely vaporize the raw material, after all, it must be heated to a high temperature up to the vicinity of the boiling point of the raw material, which is not practical.

  However, when a solution in which the raw material is dissolved in the solvent as described above is supplied into the reactor in a liquid state, the solvent that volatilizes in the reactor reduces the partial pressure of the raw material to promote its volatilization and the action of the carrier gas. To enable rapid gas phase reaction.

  The solvent used in the present invention can be used without particular limitation as long as it is inert to the above-described dehydration reaction. However, considering the action of the solvent as described above, N- (2-hydroxyethyl) as a raw material is used. A solvent that can dissolve carbazoles, has a relatively low vapor pressure, and can be easily separated from water by-produced by a dehydration reaction is preferable. Specifically, it is a chain or cyclic hydrocarbon having 6 or more carbon atoms, more preferably an aromatic hydrocarbon, and most preferred are toluene, xylene, mesitylene and the like in consideration of cost and handleability. .

  In addition, it is possible to use an inert carrier gas (for example, nitrogen gas, argon gas, helium gas, etc.) in combination with the above solvent, but in that case, the reaction product collection efficiency generally tends to decrease. Therefore, the amount used should be kept as small as possible, and it is preferable not to use unless there is a special purpose.

  These solvents also have the effect of facilitating the cooling and collection of reaction products, in addition to the action of lowering the partial pressure of the raw material to promote its evaporation as described above. That is, for example, when a carrier gas is used for the gas phase reaction, the reaction product is released along with the carrier gas, and thus the cooling collection rate of the target product is reduced. By utilizing the vapor as a carrier gas during the dehydration reaction, the collection efficiency of the reaction product can be increased. In particular, when an aromatic hydrocarbon is used as a solvent, the advantage that water produced as a by-product by the reaction can be easily removed by oil-water separation can also be enjoyed.

  The dilution rate of the raw material with the solvent is preferably in the range of 0.1 to 10% in terms of the molar fraction of N- (2-hydroxyethyl) carbazoles. Incidentally, when the dilution ratio is too high, not only the consumption of the solvent increases, but also the reaction efficiency decreases due to the low concentration, and it is difficult to obtain a satisfactory yield. In view of reaction efficiency, handling property, solvent cost, etc., it is desirable to make it 0.5 mol% or more, more preferably about 1 mol% or more. On the other hand, the upper limit of the concentration does not exist, but if the amount of the solvent for the raw material is too small and exceeds the saturated dissolution amount of the raw material, the raw material remains as a solid substance and inhibits a uniform gas phase reaction. In a concentration not exceeding the amount, it is usually 10 mol% or less, preferably 8 mol% or less, more preferably 5 mol% or less.

  The compound diluted with the solvent is preferably supplied to the reactor in a liquid state and vaporized in the reactor. More specifically, the preheat diffusion layer is formed by filling the reactor with inert particles such as ceramic balls, rings, and saddle type fillers. As a result, the time from introduction of the raw material compound into the reactor to the catalyst layer becomes longer, and heat is more uniformly applied to the raw material compound, whereby sufficient vaporization is performed. The heating temperature is not particularly limited as long as the raw material compound is sufficiently vaporized, and may be adjusted as appropriate.

  The vaporized raw material compound is then subjected to an intramolecular dehydration reaction in the reactor. The intramolecular dehydration reaction in the gas phase of N- (2-hydroxyethyl) carbazoles in the reactor proceeds efficiently in the presence of a catalyst. The catalyst used is at least one oxide such as silica, alumina, titania, zirconia, and the like, and particularly preferred is a catalyst containing silica and an alkali metal element and / or an alkaline earth metal element. These include those in which an alkali metal or alkaline earth metal is supported using the oxide as a carrier, or the oxide formed a complex oxide with an alkali metal or alkaline earth metal, or a simple mixture thereof. Is included.

  Further, in the catalyst component, at least one selected from the group consisting of boron, aluminum, and phosphorus can be further contained as another component, and it is preferable because the life of the catalyst can be extended. These can be blended in the form of boric acid, aluminate, phosphoric acid or the like when the catalyst is produced.

Among the above catalysts, _a Si-containing catalyst satisfying the relationship of the general formula [M _a Si _b X _c O _d ] in terms of the atomic ratio of the mixture or the composite as a whole is particularly preferable.

  In the above general formula, M represents an alkali metal element and / or alkaline earth metal element, Si represents silicon, X represents at least one element selected from boron, aluminum, and phosphorus, and O represents oxygen. a, b, c and d represent the number of atoms of each element, d is a constant determined by the values of a, b and c and the bonding state of each constituent element, and when a = 1, b = 1 to 500, It can take c = 0-1.

  That is, the ratio of Si to the alkali metal element and / or alkaline earth metal element can be in a wide range of 1 to 500, preferably in the range of 5 to 200, depending on the type. In addition, the content of boron, aluminum, or phosphorus that may be blended as necessary depends on the type of alkali metal element or alkaline earth metal element, the content ratio of Si, etc., but the atomic ratio is 1 or less. preferable.

  The method for preparing the catalyst is not limited at all, and conventionally known methods can be applied. Alkali metals and alkaline earth metals, which are one of the essential components of the catalyst, are used as raw materials for oxides, hydroxides, halides and salts (carbonates, nitrates, carboxylates, phosphates, sulfates, etc.) Alternatively, the metal itself can be used. Si components include silicon oxide, silicon, silicates (alkali metal silicates, alkaline earth metal silicates, etc.), silicic acid-containing molecular sieves (aluminosilicates, silicoaluminophosphates, etc.), organosilicates, etc. Can be used. The raw materials for the third component X that can be blended as required include oxides, hydroxides, halides, salts (borate, aluminate, phosphate, etc.), or B, Al, P The element itself can be used.

  Although the calcination temperature at the time of manufacturing the said catalyst can be suitably selected from the wide range of 300-1000 degreeC according to the kind of raw material to be used, the range of 400-800 degreeC is preferable.

  In carrying out the present invention, either a fixed bed flow type or a fluidized bed type can be used as a reactor for performing an intramolecular dehydration reaction in a gas phase. This reaction is carried out under conditions where the raw material N- (2-hydroxyethyl) carbazole can maintain a gas phase state. The pressure can be normal or moderately reduced, and the reaction temperature depends on the pressure, but 300 is preferable for causing the intramolecular dehydration reaction to proceed efficiently without causing thermal decomposition of the raw material or target substance. It is 350 degreeC or more and 450 degrees C or less more preferably. Further, in order to promote vaporization of N- (2-hydroxyethyl) carbazoles, the pressure may be about 100 to 700 torr (about 13 to 93 kPa) in absolute pressure.

The feed rate of the raw material to the reactor varies depending on the kind of raw material compound, the kind of catalyst, the reaction temperature, the pressure, etc., but N- (2-hydroxyethyl) carbazole per unit catalyst volume charged in the reactor in the space velocity (GHSV) which represents the supply amount of the kind, the standard state of the raw material (25 ° C., the volume of a gas at 1 atm) at 1～50Hr ^-1, more preferably in the range of 1～10Hr ^-1 .

  After the intramolecular dehydration reaction, N-vinylcarbazoles can be easily recovered by cooling the product gas. That is, as described above, when an aromatic hydrocarbon solvent such as toluene is used as the solvent, the target product can be obtained in a solution state dissolved in the solvent when the reaction product gas is cooled and condensed. In addition, water produced by the dehydration reaction condenses at the same time, but water having low solubility in the aromatic hydrocarbon solvent is phase-separated. After removing this by oil-water separation, the solvent is removed from the oil phase by any method. When N is removed, N-vinylcarbazoles can be obtained in high yield. Depending on the reaction conditions, a small amount of unreacted material may remain or by-products (such as intermolecular dehydration products) may be generated. In such cases, for example, distillation, crystallization, extraction, etc. For example, a high-purity target product may be recovered by purification using any method.

  More specifically, it is preferable to first wash the solution obtained by cooling the reaction product gas with water or saline to remove water produced by the reaction or water-soluble impurities that cause coloring. . Further, when high boiling point impurities are mixed in the target compound, vacuum distillation is preferably used, and when low boiling point impurities are mixed, recrystallization is preferably performed. As a solvent that can be used for recrystallization, an organic solvent having a relatively high polarity such as an alcohol such as methanol or ethanol; an ether such as diethyl ether or tetrahydrofuran; or a mixed solvent thereof is preferable.

  FIG. 1 is a schematic process explanatory diagram for carrying out the present invention, wherein 1 is a raw material dissolution tank, 2 is a feed pump, 3 is a reaction tower, 4 is a heating tank, 5 is a condenser, and 6 is an oil-water separator. 7 indicate solvent separators, respectively.

  In the illustrated example, the raw material A and the solvent B are supplied into the raw material dissolution tank 1 at a predetermined ratio, and are uniformly dissolved by stirring, and sent to the reaction tower 3 by the feed pump 2. The reaction tower 3 is provided with a preheating diffusion layer 3a loaded with ceramic balls, rings, saddle-type fillers and the like inert to the reaction on the raw material solution blowing side, and on the downstream side of the catalyst as described above. A packed bed 3b is provided and configured to be heated by any heating means. In the illustrated example, a heating tank 4 charged with a molten salt is disposed on the outer surface side of the reaction tower 3, and the reaction tower 3 can be heated to a predetermined temperature from the outer surface side by heating the molten salt. . Of course, the heating means is not limited to the illustrated example, and any heating method such as a method of heating the bellows tube through a heat medium or an electric heating method can be adopted.

  A condenser 5 is provided on the downstream side of the reaction tower 3, and the target product generated by the intramolecular dehydration reaction is condensed in the condenser 5 together with the solvent and by-product water, and the target product is contained in the oil / water separator 6. Separated into solvent solution and water. The solvent solution is further separated into a target product and a solvent by a solvent separator 7, and the solvent is recycled as a solvent for dissolving the raw material if necessary. The target product may then be purified by any method such as crystallization, distillation or extraction.

  The illustrated example shows only typical steps in carrying out the present invention, and does not limit the present invention technically, but includes a mixing and supplying mechanism of a raw material and a solvent, a reaction tower 3 and a heating tank 4. The specific shape and structure, and the configuration of the condenser 5 and the oil / water separator 7 can be arbitrarily changed as necessary.

  Further, the N-vinylcarbazoles obtained by the present invention can be effectively used as a raw material for producing organic EL elements, organic transistors, polymer semiconductors, etc. by using them as polymerizable monomers utilizing vinyl groups in the molecules. .

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and is suitable as long as it can meet the purpose described above and below. It is also possible to carry out with modification, and any of them is included in the technical scope of the present invention.

  In addition, the yield and space velocity (GHSV) shown in the following examples are based on the following definitions.

Yield (%) = [(number of moles of N-vinylcarbazole formed) / (number of moles of N- (2-hydroxyethyl) carbazole supplied as raw material)] × 100
Space velocity (GHSV: hr ⁻¹ ) = [volume of N- (2-hydroxyethyl) carbazole fed as a raw material in the standard state (as a gas at 25 ° C. and 1 atm)] / catalyst capacity Example 1
Preparation of catalyst Lithium nitrate (3.45 g) was dissolved in water (250 g), and silicon oxide (30 g) was added with heating and stirring at 90 ° C, followed by heating and concentration, followed by drying at 120 ° C in an air atmosphere for 20 hours. did. The obtained solid was crushed to 9 to 16 mesh and further calcined in air at 500 ° C. for 2 hours to obtain a catalyst whose composition excluding oxygen was Li ₁ Si ₁₀ .

Synthesis reaction The catalyst obtained above (30 ml) was filled in a stainless steel reaction tube having an inner diameter of 15 mm, and then a silica gel ball for vaporization diffusion was filled thereon (raw material charging side). The reaction tube was immersed in a molten salt (mass ratio 1/1 mixture of sodium nitrite and potassium nitrate) bath, heated to 430 ° C., and N- (2-hydroxy) diluted to 3 mol% with toluene in the reaction tube. The ethyl) carbazole solution was supplied at a space velocity (GHSV) of 4.5 hr ⁻¹ and an absolute pressure of 200 torr (about 27 kPa, and the following pressure is an absolute pressure). The raw material supplied into the reaction tube is immediately vaporized in the silica gel ball filling part on the inlet side and sent toward the catalyst packed bed, and the intramolecular dehydration reaction proceeds.

  One hour after the start of the reaction, the outlet gas from the reaction tube was extracted, condensed and collected, and the yield of N-vinylcarbazole was determined by gas chromatographic analysis. As a result, it was 92.3 mol%.

Example 2
Preparation of catalyst In the above Example 1, except that lithium nitrate (3.45 g) was changed to sodium nitrate (4.25 g), a catalyst whose composition excluding oxygen was Na ₁ Si ₁₀ was obtained.

Synthesis Reaction Using the catalyst obtained above, a gas phase reaction and product analysis were performed in the same manner as in Example 1. As a result, the yield of N-vinylcarbazole after 1 hour from the start of raw material supply was 79 mol%.

Example 3
Preparation of catalyst A catalyst having a composition excluding oxygen and having a composition of K ₁ Si ₁₀ was obtained in the same manner as in Example 1 except that lithium nitrate (3.45 g) was changed to potassium nitrate (5.06 g).

Synthesis reaction The gas phase reaction and product analysis were performed in the same manner as in Example 1 except that the catalyst obtained above was used and the reaction temperature was changed to 450 ° C. As a result, the yield of N-vinylcarbazole after 1 hour from the start of raw material supply was 87 mol%.

Example 4
Preparation of Catalyst A spherical silica gel (30 g) having a particle size of 5 to 10 mesh was immersed in a solution of cesium carbonate (0.41 g) in water (40 g) for 2 hours, and then heated and dried on a hot water bath. Next, after calcining in air at 120 ° C. for 20 hours, further calcining in air at 800 ° C. for 2 hours to obtain a catalyst whose composition excluding oxygen is Cs ₁ Si ₂₀₀ .

Synthesis reaction The gas phase reaction and product analysis were performed in the same manner as in Example 1 except that the catalyst obtained above was used and the reaction temperature was changed to 440 ° C. As a result, the yield of N-vinylcarbazole after 1 hour from the start of raw material supply was 93 mol%.

Example 5
Catalyst Preparation Spherical silica gel (30 g) having a particle size of 5 to 10 mesh was immersed in a solution of barium sulfate (4.36 g) in water (100 g) for 2 hours, and then heated and dried on a hot water bath. Next, after calcining in air at 120 ° C. for 20 hours, further calcining in air at 500 ° C. for 2 hours to obtain a catalyst whose composition excluding oxygen was Ba ₁ Si ₃₀ .

Synthesis reaction The gas phase reaction and product analysis were performed in the same manner as in Example 1 except that the catalyst obtained above was used and the reaction temperature was changed to 450 ° C. As a result, the yield of N-vinylcarbazole after 1 hour from the start of raw material supply was 80 mol%.

Example 6
Preparation of catalyst To a solution of cesium oxide (19.5 g) and diammonium phosphate (9.2 g) dissolved in water (100 g), aluminum phosphate (1.2 g) and silicon oxide (30 g) were added. After heating and mixing uniformly on the bath, the mixture was heated to dryness. Next, after calcining in air at 120 ° C. for 20 hours, it is crushed to 9-19 mesh, and further calcined in air at 500 ° C. for 2 hours, so that the composition excluding oxygen consists of Cs ₁ Si ₅ Al _0.1 P _0.8. A catalyst was obtained.

Synthesis reaction The gas phase reaction and products were analyzed in the same manner as in Example 1 except that the catalyst obtained above was used and the space velocity (GHSV) was changed to 8.5 hr ^-1 . As a result, the yield of N-vinylcarbazole after 1 hour from the start of raw material supply was 59 mol%.

Example 7
Catalyst Preparation Silicon oxide (30 g) was added to a solution of cesium nitrate (19.5 g) and boric acid (4.9 g) dissolved in water (100 g), and the mixture was concentrated and dried while heating and mixing on a hot water bath. Next, after calcining in air at 120 ° C. for 20 hours, crushing to 9-16 mesh, and further firing in air at 500 ° C. for 2 hours, a catalyst whose composition excluding oxygen is Cs ₁ Si ₅ B _0.8 is obtained. Obtained.

Synthesis reaction The gas phase reaction and products were analyzed in the same manner as in Example 1 except that the catalyst obtained above was used and the space velocity (GHSV) was changed to 6.8 hr ^-1 . As a result, the yield of N-vinylcarbazole after 1 hour from the start of the raw material supply was 83 mol%.

Example 8
Preparation of catalyst After adding silicon oxide (30 g) to a solution of cesium nitrate (9.75 g) and diammonium phosphate (2.64 g) dissolved in water (100 g), and uniformly heating and mixing on a hot water bath, Heat to dryness. Next, after calcining in air at 120 ° C. for 20 hours, crushing to 9-19 mesh, and further firing in air at 600 ° C. for 2 hours, the composition excluding oxygen consists of Cs ₁ Si ₁₀ P _0.4. A catalyst was obtained.

Synthesis reaction The gas phase reaction and products were analyzed in the same manner as in Example 1 except that the catalyst obtained above was used and the space velocity (GHSV) was changed to 6.8 hr ^-1 . As a result, the yield of N-vinylcarbazole after 1 hour from the start of raw material supply was 77 mol%.

Example 9
Catalyst Preparation Silicon oxide (30 g) was added to a solution of cesium carbonate (8.15 g) in water (100 g), heated and mixed on a hot water bath, and then heated to dryness. Next, after calcining in air at 120 ° C. for 20 hours, it was crushed to 9-16 mesh and further calcined in air at 500 ° C. for 2 hours to obtain a catalyst whose composition excluding oxygen was Cs ₁ Si ₁₀ . .

Synthesis reaction The catalyst obtained above (30 ml) was filled in a stainless steel reaction tube having an inner diameter of 15 mm, and then a silica gel ball for vaporization diffusion was filled thereon (raw material charging side). This reaction tube was immersed in a molten salt bath and heated to 460 ° C., and an N- (2-hydroxyethyl) carbazole solution diluted to 3 mol% with toluene was added to the reaction tube with a space velocity (GHSV) of 4.5 hr. ^-1 and a pressure of 500 torr (about 67 kPa). The raw material supplied into the reaction tube is immediately vaporized in the silica gel ball filling part on the inlet side and sent toward the catalyst packed bed, and the reaction proceeds.

  One hour after the start of the reaction, the outlet gas from the reaction tube was extracted, condensed and collected, and the yield of N-vinylcarbazole was determined by gas chromatographic analysis. As a result, it was 84 mol%.

Example 10
Catalyst preparation A catalyst was prepared in exactly the same manner as in Example 9.

Synthesis reaction The catalyst obtained above (30 ml) was filled in a stainless steel reaction tube having an inner diameter of 15 mm, and then a silica gel ball for vaporization diffusion was filled thereon (raw material charging side). The reaction tube was immersed in a molten salt bath and heated to 480 ° C., and an N- (2-hydroxyethyl) carbazole solution diluted to 3 mol% with xylene was added to the reaction tube with a space velocity (GHSV) of 8.5 hr. ^-1 and a pressure of 200 torr (about 27 kPa). The raw material supplied into the reaction tube is immediately vaporized in the silica gel ball filling part on the inlet side and sent toward the catalyst packed bed, and the reaction proceeds.

  One hour after the start of the reaction, the outlet gas from the reaction tube was extracted, condensed and collected, and the yield of N-vinylcarbazole was determined by gas chromatographic analysis. As a result, it was 76 mol%.

Example 11
Preparation of catalyst Silicon oxide (30 g) was added to a solution of sodium nitrate (4.25 g) and diammonium phosphate (2.64 g) dissolved in 100 g of water, and heated and mixed uniformly on a hot water bath. Dried to dryness. Next, after calcining in air at 120 ° C. for 20 hours, crushing to 9-19 mesh, and further firing in air at 600 ° C. for 2 hours, a catalyst whose composition excluding oxygen is Na ₁ Si ₁₀ P _0.2 is obtained. Obtained.

Synthesis reaction The gas phase reaction and products were analyzed in the same manner as in Example 1 except that the catalyst obtained above was used and the space velocity (GHSV) was changed to 6.8 hr ^-1 . As a result, the yield of N-vinylcarbazole after 1 hour from the start of raw material supply was 74 mol%.

  According to the present invention, there is no danger due to high-pressure conditions or use of explosive substances, and there are few problems in post-treatment such as waste treatment derived from by-products, and N-vinylcarbazoles are produced by a continuous process suitable for industrialization. Therefore, the present invention is extremely useful industrially.

Claims (4)

The following general formula (1)
[Wherein, R ^{1 to} R ⁸ each independently represents hydrogen, a halogen atom, a C _1-6 alkyl group, a C _1-6 alkoxy group, a cyano group or a nitro group]
A reactor having a preheating diffusion layer and a catalyst packed layer continuously obtained by diluting N- (2-hydroxyethyl) carbazoles represented by the formula (1) to at least one solvent selected from the group consisting of toluene, xylene and mesitylene . The liquid is supplied to the preheating diffusion layer of the catalyst and subjected to intramolecular dehydration reaction in the gas phase in the presence of a catalyst.
[Wherein R ^{1 to} R ⁸ represent the same meaning as described above]
A process for producing N-vinylcarbazoles, which is converted to N-vinylcarbazoles represented by the formula:   The process according to claim 1, wherein the N- (2-hydroxyethyl) carbazoles are diluted with a solvent to a concentration of 0.1 to 10 molar and then supplied to the reactor.   The process according to claim 1 or 2, wherein a catalyst containing at least one selected from the group consisting of silica, alumina, titania and zirconia and an alkali metal and / or an alkaline earth metal is used as the catalyst.   The process according to claim 3, wherein the catalyst further comprises a catalyst containing at least one selected from the group consisting of boron, aluminum, and phosphorus.