JP2009107969A - Method for producing vinyl chloride - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing vinyl chloride by which vinyl chloride can be produced with a high conversion rate and high selectivity by catalytic cracking of 1,2-dichloroethane that is practicable in a lower temperature region than a conventionally known thermal decomposition method, and miniaturization of an apparatus or simplification of a process can be achieved. <P>SOLUTION: The method for producing vinyl chloride comprises using a molybdenum chloride cluster as a dehydrochlorination catalyst and carrying out dehydrochlorination of 1,2-dichloroethane in the presence of the catalyst at 250-540°C reaction temperature, to thereby produce vinyl chloride. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a process for producing vinyl chloride by dehydrochlorination using 1,2-dichloroethane.

  Vinyl chloride is a monomer of polyvinyl chloride used in various plastic molded articles, and is an industrially extremely useful compound.

  Such vinyl chloride is produced by, for example, a method of thermally decomposing 1,2-dichloroethane at a high temperature of about 450 to 540 ° C. under a high pressure of 1 to 5 MPa, using 1,2-dichloroethane as a starting material. Yes. However, in this thermal decomposition method, the conversion rate (decomposition rate) of 1,2-dichloroethane is limited to about 50% in order to suppress the formation of by-products that are difficult to separate such as butadiene, chloroethane, and coking. There's a problem. When the conversion rate of 1,2-dichloroethane increases, the amount of by-products that are difficult to separate as described above increases, and thus the conversion rate cannot be increased. Therefore, in such a thermal decomposition method, there is a large amount of unreacted 1,2-dichloroethane. For this reason, in this production line, in addition to the reactor main body, there are complicated steps such as a recovery step for unreacted components and a product separation step. It is necessary to provide a simple process, and a large amount of energy is required at the time of production, and there is a demand for a method that replaces the thermal decomposition method.

As an alternative to the thermal decomposition method as described above, there is a catalytic decomposition method in which vinyl chloride is produced by dehydrochlorinating 1,2-dichloroethane (hereinafter sometimes simply referred to as EDC) in the presence of a catalyst. Various proposals have been made.
For example, Patent Document 1 describes the removal of EDC using a catalyst comprising a reaction product of H-Y type or Y-type zeolite exchanged with Na and Ca ions and a Lewis acid such as TiCl ₄ , SbCl ₅ , and PCl _3. Catalytic cracking with hydrogen chloride has been proposed.
Patent Document 2 proposes a catalytic cracking method using synthetic zeolite made of siliceous zeolite such as ZSM-5 or silicalite as the catalyst.
Patent Document 3 proposes a catalytic cracking method using offretite-erionite-based zeolite or L-type zeolite as a catalyst.
Patent Document 4 proposes a catalytic cracking method using a catalyst in which a rare earth metal chloride is supported on zeolite.
Patent Document 5 proposes a catalytic cracking method using a catalyst in which an offtite-erionite-based zeolite and an alkali metal salt are mixed.
Patent Document 6 proposes a catalytic cracking method using a catalyst in which a metal chloride or a metal oxide is supported on a porous carrier.
Patent Document 7 proposes a catalytic cracking method using fibrous activated carbon as a catalyst.

  In addition, it has been reported that a halide cluster which is a metal cluster having a halogen as a ligand is used as a dehydrohalogenation catalyst for 1-chloropentane (Non-patent Document 1).

JP-A-54-79209 JP 58-167526 A JP-A-60-252433 JP-A-61-30 JP-A-2-256630 JP-A-8-103657 Japanese Patent Laid-Open No. 9-249590 S. Kamiguchi etc., J.A. Mol, Catal, A, 203, (2003), p. 153-163

The method for producing vinyl chloride by catalytic cracking of 1,2-dichloroethane proposed in Patent Documents 1 to 7 as described above can significantly reduce the reaction temperature as compared with the thermal cracking method. In addition, the conversion rate can be increased and the production of by-products that are difficult to separate such as butadiene, chloroethane, and caulking can be suppressed. Therefore, the amount of energy required during production can be reduced, and it has been used more industrially than before. It is expected that the size of the existing equipment can be reduced or the process can be simplified.
However, the above-described methods by catalytic cracking of 1,2-dichloroethane are still unsatisfactory in both conversion and selectivity, and further improvement is required, and both have a remarkable catalyst life. It is unsatisfactory and is not implemented industrially.

  In addition, halide clusters as disclosed in Non-Patent Document 1 are stable against heat and extremely stable electronically, so that they can be used stably for a long period of time as a catalyst. However, the catalytic activity for the dehydrochlorination reaction is unsatisfactory, the conversion rate and selectivity are low, and many by-products are generated. For example, Table 1 on page 159 of Non-Patent Document 1 shows the conversion rate and selectivity when various halide clusters are used as the dehydrochlorination catalyst for 1-chloropentane. The conversion rate is 62%. However, most of them are 10% or less, and the selectivity to 1-pentene is about 54 to 55% at maximum, which is extremely low. For this reason, use of a halide cluster in the process of producing vinyl chloride by dehydrochlorination of 1,2-dichloroethane has not been studied.

  Therefore, the object of the present invention is to produce vinyl chloride at a high conversion and high selectivity by catalytic cracking of 1,2-dichloroethane, which can be carried out in a low temperature region as compared with a conventionally known pyrolysis method, An object of the present invention is to provide a method for producing vinyl chloride, which can realize downsizing of the apparatus or simplification of processes.

  As a result of intensive studies on the production method of vinyl chloride by catalytic cracking of 1,2-dichloroethane using a catalyst, the present inventors have found that, among various types of halide clusters, in particular, chlorine cluster molybdenum is used as a dehydrochlorination catalyst. The inventors have found a new finding that the conversion rate and selectivity can be increased, and vinyl chloride can be produced stably and efficiently over a long period of time, and the present invention has been completed.

  That is, according to the present invention, vinyl chloride is obtained by dechlorinating 1,2-dichloroethane at a reaction temperature of 250 to 540 ° C. using chlorine cluster molybdenum as a dehydrochlorination catalyst in the presence of the catalyst. A method for producing vinyl chloride is provided.

In the production method of the present invention,
(1) To support chlorine cluster molybdenum on a porous carrier and use it as a dehydrochlorination catalyst;
(2) using activated carbon, alumina, titania or zeolite as the carrier;
(3) performing dehydrochlorination at the reaction temperature of 300 to 450 ° C .;
Is preferred.

  In the present invention, it is important to use chlorine cluster molybdenum as a dehydrochlorination catalyst for 1,2-dichloroethane (EDC). By using such a catalyst, a dechlorination reaction can be performed in a low temperature region. Not only is it advantageous in terms of thermal energy, but also increases the conversion rate, reduces the amount of unreacted EDC, and improves the selectivity of the reaction, not only carbides, but also butadiene, acetylene, ethylene, chloroethane, etc. The production of by-products that are difficult to separate can be effectively suppressed, the load required for separation and recovery of raw materials and purification can be significantly reduced, and the catalyst life is long, and vinyl chloride can be produced stably over a long period of time. Is very advantageous.

In the production method of the present invention, 1,2-dichloroethane (EDC) is used as a starting material, and this EDC gas is brought into contact with chlorine cluster molybdenum as a catalyst at a predetermined temperature to produce vinyl chloride by a dehydrochlorination reaction. Yes, this reaction is represented by the following formula: In the formula, chlorine cluster molybdenum is represented as Mo cluster.

In the present invention, the chlorine cluster molybdenum used as a dehydrochlorination catalyst is one in which Cl atoms are coordinated to an octahedral skeleton formed by Mo atoms, and a part of the coordinated Cl atoms is replaced with water. For example, it is represented by the following general formula (I) or (II).
[Mo ₆ Cl ₁₄ ] [H ₃ O] (I)
[Mo ₆ Cl ₁₂ (H ₂ O) _n ] (II)

  That is, in the above-mentioned chlorine cluster molybdenum, the chlorine atoms exist in a loosely coordinated form outside the molybdenum skeleton, and when heated to a predetermined temperature, the chlorine atoms are desorbed, and the coordination is free in the cluster. Site is formed. The chlorine atom of EDC is coordinated to this vacant site, and as a result, the dehydrochlorination reaction of EDC is promoted, and the conversion rate and selectivity are improved.

  In the present invention, it is important to use chlorine cluster molybdenum among various metal clusters. When other clusters are used, the conversion rate and selectivity are not improved as in the present invention. For example, as understood from Table 1 showing experimental results of Examples and Comparative Examples described later, in a cluster in which a chlorine atom is coordinated to niobium, the conversion rate of EDC is 41.5%, and vinyl chloride (VCM ) Is 65.3% (Comparative Example 3), but when using the chlorine cluster molybdenum according to the present invention, the conversion of EDC is about 60% or more, The selectivity is about 96% or higher, which is remarkably high. Further, in a cluster in which a chlorine atom is coordinated to rhenium (Re), the conversion rate of EDC is extremely high at 85.0%, but the selectivity to vinyl chloride is considerably low at 67.5%.

  Thus, in the present invention, by using chlorine cluster molybdenum as a dehydrochlorination catalyst, the conversion rate of EDC can be increased and the selectivity to vinyl chloride can be remarkably improved. The function of molybdenum as a dehydrochlorination catalyst is not observed in clusters in which chlorine atoms are coordinated to other metal atoms, and is selectively exerted in the dehydrochlorination of EDC (1,2-dichloroethane). This is not exhibited by dehydrochlorination from other halogenated hydrocarbons. That is, as shown in Non-Patent Document 1 described above, when chlorine cluster molybdenum is applied to a halogenated hydrocarbon such as 1-chloropentane, the conversion rate and selectivity are low, and the unreacted product And many by-products are generated. The reason for this has not been clearly clarified, but perhaps the phenomenon that the chlorine atom bonded to the hydrocarbon re-coordinates to the vacant site caused by the detachment of the chlorine atom from the above-mentioned cluster is due to the bonding of the chlorine atom. The combination of chlorine cluster molybdenum and 1,2-dichloroethane is the best match for the re-coordination of the chlorine atom, depending on the size of the hydrocarbon molecules and the metal atoms that form the cluster skeleton. It seems to be for this.

  The dehydrochlorination reaction of EDC using the catalyst as described above is carried out in a fixed bed flow system in which, for example, the EDC gas as a raw material is continuously supplied to a stainless steel reactor filled with the catalyst. .

  In the above reaction, the reaction temperature is set in the range of 250 to 500 ° C, particularly 300 to 450 ° C. When the reaction temperature is lower than the above range, the conversion rate of EDC is low, the yield is reduced, and the load required for recovering unreacted EDC is increased, which is unsuitable for industrial implementation. . Furthermore, if the reaction temperature is higher than the above range, the amount of by-products such as acetylene, carbide, ethylene, and chloroethane increases even if the conversion rate of EDC is improved, and the selectivity of vinyl chloride decreases, resulting in an increase in yield. The reduction in the rate and the load required for purification become large, which is not only unsuitable for industrial implementation, but also causes a problem that the catalyst life is reduced and the catalyst needs to be frequently replaced.

  In the present invention, the reactor filled with the catalyst is heated to the above-mentioned predetermined temperature range by a heater or the like. A preheater is disposed upstream of the reactor, and EDC gas is supplied through the preheater. It is preferred to feed continuously into the reactor. That is, the EDC gas supplied into the reactor is heated to an appropriate temperature in advance before filling the reactor, thereby increasing the reaction rate, increasing the EDC gas supply rate, and increasing the productivity. Can do. The supply rate of EDC gas is set so that EDC can contact the catalyst for a sufficient time to complete the reaction, depending on the size of the reactor (length of the catalyst layer) and the like.

  The pressure during the reaction is not particularly limited, but is preferably in the range of normal pressure to 3 MPaG in order to improve the selectivity to vinyl chloride.

In addition, the chlorine-molybdenum cluster can be used alone as a catalyst as a solid powder, but it is preferable to use it as a catalyst by holding it on a porous carrier in terms of its handleability and cost. . Such a porous carrier is not particularly limited as long as it is a particle having an appropriate size that does not adversely affect the dechlorination reaction and allows the passage of EDC gas. In general, activated carbon, alumina, titania, silica, various zeolites (for example, A-type zeolite) having a specific surface area of, for example, a BET specific surface area of 350 g / m ² or more can be preferably used. From the standpoint that high affinity can be firmly supported, and that a large specific surface area can be obtained at low cost, activated carbon is most suitable. In addition, activated carbon itself has a high function as a dehydrochlorination catalyst, and the conversion of EDC and the selectivity to vinyl chloride can be maximized by using activated carbon carrying a chloromolybdenum cluster.

  In addition, the loading of the chlorine-molybdenum cluster on the porous carrier is facilitated by, for example, immersing the porous carrier in a solution obtained by suspending and dispersing the chlorine-molybdenum cluster in an organic solvent or in a hydrochloric acid solution of the chlorine-molybdenum cluster and then drying. Can be done. Further, when the chloromolybdenum cluster is supported on the above-mentioned carrier, the amount supported is generally in the range of 0.01 to 20% by mass, particularly 0.01 to 5% by mass, based on the porous carrier.

  The reaction gas continuously discharged from the reactor is once introduced into a reaction liquid trap tank cooled to −10 ° C., and liquefied and condensed after unreacted EDC is recovered and then generated by a dehydrochlorination reaction. The introduced hydrogen chloride is introduced into a removal trap tank in which an aqueous NaOH solution or the like is stored and then removed, and then introduced into a known purification process. By-products are separated by distillation or the like, and the desired vinyl chloride is obtained. .

  Hereinafter, the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

The conversion rate of 1,2-dichloroethane (EDC) and the selectivity to vinyl chloride by the dehydrochlorination reaction of the following examples and comparative examples were calculated by the following equations.
Conversion rate (mol%)
= (Feed EDC (mol) -unreacted EDC (mol)) / feed EDC (mol) × 100 selectivity (mol%)
= Vinyl chloride (mol) / (feed EDC (mol) -unreacted EDC (mol)) × 100

  In the following Examples and Comparative Examples, the fixed bed flow reactor was used in FIG. 1, and the dehydrochlorination reaction of EDC was performed as follows.

  First, in this fixed bed flow reactor, a reactor 5 comprising a stainless steel tube having an inner diameter of 7.1 mm and a length of 300 mm is disposed, and the reactor 5 is filled with a dehydrochlorination catalyst. An electric heater 4 is disposed on the outside of 5. Further, on the upstream side of the reactor 5, a preheater 3 made of a stainless steel tube having an inner diameter of 2.2 mm and a length of 2000 mm, to which an external heater 2 is attached, is arranged. EDC is preheated by the metering pump 1. EDC supplied to the reactor 3 and vaporized and preheated is continuously supplied into the reactor 5. Further, a nitrogen supply port 7 is provided in the pipe between the metering pump 1 and the preheater 3, and a predetermined amount of nitrogen gas is supplied via the flow rate controller 6. Further, a reaction liquid trap 13 and an exclusion trap 14 are arranged on the downstream side of the reactor 5, and the reaction gas continuously discharged from the reactor 5 passes through the reaction liquid trap 13 and the exclusion trap 14. It is designed to be recovered together with the generated vinyl chloride.

  In order to adjust the gas temperature in the preheater 3 and the reactor 5 to a predetermined temperature, temperature sensors 12 and 13 are provided, respectively, and a pressure sensor 11 is provided on the inlet side of the reactor 5. The pressure in the reactor 5 can be detected. In addition, sampling ports 9 and 8 are provided on the inlet side and the outlet side of the reactor 5, respectively.

  In each example and comparative example, 10 ml of the catalyst prepared in each example was charged, and then the preheater was 190 ° C., the reactor was 400 ° C., and the mass flow controller (6) was used at 100 ml / min. The amount of nitrogen gas adjusted to the amount was continuously supplied from the nitrogen supply port (7) for 1 hour to pretreat the catalyst.

  Next, the supply of nitrogen gas is stopped, the temperatures of the preheater 3 and the reactor 5 are maintained as they are, and EDC is continuously supplied into the reactor 5 from the metering pump 1 at an amount of 0.3 ml / min. Then, dehydrochlorination reaction of EDC was performed.

The product obtained by the reaction collects the gas after reaction from the sampling port 8 attached to the outlet of the reactor 5 and analyzes it by gas chromatography to obtain the conversion rate of EDC and the selectivity to vinyl chloride. In addition, the by-product type and selectivity were determined.
In each example, the gas supplied to the reactor 5 is collected from the sampling port 9 attached to the inlet of the reactor 5, analyzed by gas chromatography, and dechlorination of the supplied EDC in the preheater 3. It was confirmed that no hydrogen reaction occurred.

  Further, the dehydrochlorination reaction as described above was continuously continued for 10 hours, during which time the product was analyzed at intervals of 30 minutes, and the conversion rate and selectivity were determined. From the change over time in the EDC conversion rate, Since about 2 hours after the start, the EDC conversion rate was almost constant and was considered to be in a steady state. Therefore, the experimental results of each Example and Comparative Example were as follows: Table 1 shows the conversion and selectivity with this catalyst.

<Example 1>
Molybdenum chloride (V) 50.0 g and molybdenum 150.0 g are mixed well in a solid state, heated in a quartz reactor at 600 ° C. in a nitrogen stream, reacted for 8 hours, and unreacted molybdenum from the reaction mixture. And recrystallizing with 20% hydrochloric acid to prepare chlorine cluster molybdenum in a yield of 52.3%.
This chlorine cluster molybdenum is represented by the following formula.
(H ₃ O) ₂ [(Mo ₆ Cl ₈ ) Cl ₆ ] · 6H ₂ O

99.5 g of activated carbon (BET specific surface area: 1100 g / m ² ) is added as a porous carrier to a solution obtained by dissolving 0.5 g of this chlorine cluster molybdenum in 150 ml of 25% hydrochloric acid, and the chlorine cluster molybdenum is stirred gently for 12 hours. Was impregnated. In this way, the chlorine cluster molybdenum supported on the activated carbon was taken out and dried at 110 ° C. for 12 hours to prepare a dehydrochlorination catalyst (catalyst A) supporting the chlorine cluster molybdenum.
The catalyst A is charged into the reactor 5 as described above, dehydrochlorination is performed by supplying EDC, and the conversion rate of EDC and the selectivity to vinyl chloride (VCM) are determined. The results are shown in Table 1.
In Table 1, chlorine cluster molybdenum is shown as Mo cluster.

<Example 2>
A dehydrochlorination catalyst (catalyst B) carrying chlorine cluster molybdenum was prepared in the same manner as in Example 1 except that alumina (BET specific surface area; 420 g / m ² ) was used instead of activated carbon as the porous carrier. The dehydrochlorination reaction was carried out in the same manner as in Example 1 except that this catalyst B was used, and the conversion rate, selectivity and the like were determined. The results are shown in Table 1.

<Example 3>
A dehydrochlorination catalyst (catalyst C) carrying chlorine cluster molybdenum was prepared in the same manner as in Example 1 except that titania (BET specific surface area; 480 g / m ² ) was used instead of activated carbon as the porous carrier. The dehydrochlorination reaction was carried out in the same manner as in Example 1 except that this catalyst C was used, and the conversion rate, selectivity and the like were determined. The results are shown in Table 1.

<Example 4>
A dehydrochlorination catalyst (catalyst D) on which chlorine cluster molybdenum was supported was carried out in the same manner as in Example 1 except that A-type zeolite (BET specific surface area; 550 g / m ² ) was used instead of activated carbon as the porous carrier. The dehydrochlorination reaction was carried out in the same manner as in Example 1 except that this catalyst D was prepared and the conversion rate, selectivity, etc. were determined. The results are shown in Table 1.

<Example 5>
A dehydrochlorination catalyst (catalyst E) carrying chlorine cluster molybdenum was prepared in the same manner as in Example 1 except that silica (BET specific surface area: 400 g / m ² ) was used instead of activated carbon as the porous carrier. The dehydrochlorination reaction was carried out in the same manner as in Example 1 except that this catalyst E was used, and the conversion rate, selectivity and the like were determined. The results are shown in Table 1.

<Comparative example 1 (blank test)>
The reactor 5 was not charged with a catalyst, and a dehydrochlorination reaction was carried out in the same manner as in Example 1 without using a catalyst, and the conversion rate, selectivity and the like were determined. The results are shown in Table 1.

<Comparative example 2>
The dehydrochlorination reaction was carried out in the same manner as in Example 1 except that only the activated carbon used for supporting the chlorine cluster molybdenum was used as a catalyst without using the chlorine cluster molybdenum, and the conversion rate, selectivity, etc. were obtained. Is shown in Table 1.

<Comparative Example 3>
Niobium chloride (V) 5.0 g, niobium 8.0 g, and sodium chloride 1.6 g are mixed well in a solid state, heated to 850 ° C. in a quartz reactor in a nitrogen stream, and allowed to react for 18 hours. Chlorine cluster niobium was prepared by removing unreacted niobium from the mixture and recrystallizing with 20% hydrochloric acid (yield 45.0%).
This chlorine cluster niobium is represented by the following formula.
(H ₃ O) ₂ [(Nb ₆ Cl ₁₂ ) Cl ₂ (H ₂ O) ₄ ] · 4H ₂ O

A catalyst F was prepared in the same manner as in Example 1 except that the above-described chlorine cluster niobium was used, and a dehydrochlorination reaction was carried out in the same manner as in Example 1 except that this catalyst F was used. The results are shown in Table 1.
In Table 1, chlorine cluster niobium is shown as Nb cluster.

<Comparative example 4>
A catalyst G was prepared in the same manner as in Example 1 except that a commercially available chlorine cluster rhenium (Re ₃ Cl ₉ ) was used instead of the chlorine cluster molybdenum, and in the same manner as in Example 1 except that this catalyst G was used. A dehydrochlorination reaction was carried out to determine the conversion rate, selectivity, etc., and the results are shown in Table 1.
In Table 1, chlorine cluster rhenium is shown as Re cluster.

<Comparative Example 5>
A catalyst H in which iron (III) chloride was used instead of chlorine cluster molybdenum and iron chloride (III) was supported on activated carbon was prepared in the same manner as in Example 1, and Example 1 was used except that this catalyst H was used. The dehydrochlorination reaction was carried out in the same manner to determine the conversion rate, selectivity, etc., and the results are shown in Table 1.

<Comparative Example 6>
A catalyst I was prepared in the same manner as in Comparative Example 5 except that iron oxide (III) was supported on activated carbon instead of iron chloride (III), and in the same manner as in Example 1 except that this catalyst I was used. A dehydrochlorination reaction was carried out to determine the conversion rate, selectivity, etc., and the results are shown in Table 1.

It is explanatory drawing of the fixed bed flow reaction apparatus used by the Example and comparative example of this specification.

Explanation of symbols

1: Metering pump 2: Heater for preheater 3: Preheater 4: Heater for reactor 5: Reactor 6: Mass flow controller 7: Nitrogen supply port 8: Outlet sampling port 9: Inlet sampling port 10: Temperature sensor 11: Pressure sensor 12 : Temperature sensor 13: Reaction liquid trap 14: Detoxification trap

Claims (4)

  Chlorine cluster molybdenum is used as a dehydrochlorination catalyst, and vinyl chloride is produced by dehydrochlorination of 1,2-dichloroethane at a reaction temperature of 250 to 540 ° C. in the presence of the catalyst. A method for producing vinyl.   The production method according to claim 1, wherein chlorine cluster molybdenum is supported on a porous carrier and used as a dehydrochlorination catalyst.   The production method according to claim 2, wherein activated carbon, alumina, titania or zeolite is used as the carrier.   The production method according to any one of claims 1 to 3, wherein dehydrochlorination is performed at a reaction temperature of 300 to 450 ° C.

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