JPH05132436A - Catalytic dehydrochlorination process - Google Patents

Abstract

PURPOSE:To obtain vinylidene chloride by contacting a chlorinated hydrocarbon with a catalyst comprising cesium nitrate supported on silica gel, thereby dehydrochlorinating 1,1,2-trichloroethane in high selectivity and conversion using a catalyst resistant to the lowering of activity. CONSTITUTION:An aqueous solution of cesium nitrate among various cesium salts is impregnated in a silica gel, formed by a tablet machine, crushed and left standing in air at 400 deg.C for 2hr and the obtained catalyst is packed to form a packed layer 1. A chlorinated hydrocarbon such as 1,1,2-trichloroethane is introduced into the packed catalyst layer 1 through a specimen inlet port 6 and made to contact with the catalyst under heating with an electric heater 3 at 300 deg.C controlled by a temperature controller 4 to effect the dehydrochlorination of the chlorinated hydrocarbon. A dehydrochlorination product of a chlorinated hydrocarbon such as vinylidene chloride can be produced in high conversion and selectivity using a catalyst causing little lowering of the catalytic activity after the use over a long period.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a catalyst for bringing a chlorinated hydrocarbon into contact with the chlorinated hydrocarbon when carrying out a dehydrochlorination reaction, and further improving its activity and selectivity.
The decrease in activity due to continuous use is extremely reduced, and the regeneration ability of the catalyst used for a long period of time is remarkably improved.
The present invention relates to a dehydrochlorination reaction catalyst.

[0002]

2. Description of the Related Art Conventionally, the dehydrochlorination reaction of chlorinated hydrocarbons, particularly the dehydrochlorination reaction of chlorinated saturated hydrocarbons, has been an industrially important reaction, and several industrialization processes have been adopted. ..

As a typical example, vinylidene chloride (hereinafter referred to as VDC) is 1,1,2-trichloroethane (hereinafter referred to as TCE) which is a chlorinated hydrocarbon serving as a reaction substrate.
Is written. ) And a strong base such as lime milk and sodium hydroxide, are widely produced by a stoichiometric reaction. In the production of this VDC, the hydrogen chloride by-produced by the dehydrochlorination reaction of TCE and the added strong base substance form a salt, so that both hydrogen chloride and the strong base are consumed. It will be.

On the other hand, vinyl chloride monomer (hereinafter referred to as VCM
Is written. ) Is 1,2-dichloroethane (hereinafter, EDC
Is written. The production by dehydrochlorination reaction by thermal decomposition of) is generally carried out. This thermal decomposition reaction is usually 10 to
It is carried out under a high pressure and high temperature of 50 Kg / cm ² , about 460 to 540 ° C., and it is not preferable to increase the amount of side reaction products such as butadiene and methyl chloride, and mainly carbon in the reaction tube for carrying out the thermal decomposition reaction. It is necessary to limit the conversion rate of EDC to 50 to 60% due to an increase in the amount of adhered coke. Therefore, in the thermal decomposition method of this EDC, the reaction step,
Furthermore, there are drawbacks in that not only the steps of recovering unreacted materials and the steps of separating products become complicated, but also a large amount of energy is required.

For these reasons, VDC manufacturing and VCM
In the production of methane, there is a strong demand for the development of an economical dehydrochlorination method using a catalyst as an alternative method to this conventional method. For example, a method using ZSM-5, silicalite or the like as a catalyst (JP-A-58-167526), or Y
Method using a catalyst obtained by treating or reacting type zeolite with Lewis acid (JP-A-54-79209), method using a catalyst in which rare earth metal chloride is deposited on zeolite (JP-A-61-30) In addition, there is a method of using offretite-erionite type zeolite (hereinafter referred to as OE type zeolite), L-type zeolite as a catalyst (JP-A-60-252433) and the like.

These methods show that the dehydrochlorination reaction of chlorinated saturated hydrocarbons, for example, the dehydrochlorination reaction of EDC, can be carried out at a lower reaction temperature than the dehydrochlorination reaction by thermal decomposition. There is.

However, in any of these methods, no mention is made of the life of the catalyst, which is particularly important in industrialization. Therefore, as the dehydrochlorination reaction progresses, it is considered to be caused by carbon deposition on the catalyst, and as a method of reducing this carbon deposition amount, OE-based zeolite exchanged with an alkali metal and an alkali metal salt were mixed. A method using a catalyst (JP-A-2-256630), a method using a catalyst in which an alkali metal-exchanged OE zeolite and an alkali are contacted (JP-A-3-81232), and the like are proposed.

[0008] In these methods, the amount of carbon deposited on the catalyst after the dehydrochlorination reaction for several hours is reduced, but the reduction in catalyst activity is not specified, and it is sufficiently compatible with industrialization. You don't get it.

Further, as a measure from the viewpoint of suppressing the decrease in catalytic activity, a method is used in which a catalyst exchanged with the same kind of alkali metal is used and the reaction is carried out at an olefin concentration of 25 vol% or less (JP-A-3-141232). Issue).

However, the olefin concentration of the desired product (which is the VCM concentration in this reference) is 25
Limiting at a low concentration of not more than vol% requires a conversion rate lower than that in the conventional thermal decomposition method, or requires a large amount of gas for dilution (inert gas such as nitrogen in the example of the cited example). As compared with the conventional method, the process becomes more complicated, and it is disadvantageous in terms of energy and materials, and industrialization is difficult.

Moreover, any of these methods (Japanese Patent Application Laid-Open No. 167536/58, Japanese Patent Application Laid-Open No. 54-79209,
JP-A-61-130, JP-A-60-252433, JP-A-2-256630, JP-A-3-81
No. 232 and JP-A No. 3-141232) also describe catalyst performance such as catalyst conversion rate, selectivity and life in the dehydrochlorination reaction of EDC, but TC
No specific description is made on the catalytic performance of E in the dehydrochlorination reaction, and further on the production of VDC.

Regarding the production of VDC by the dehydrochlorination reaction of TCE, a method using a chloride of potassium, cesium or rubidium as a catalyst (JP-A-48-627).
No. 06 gazette), VDC using alumina, chromia or titanium oxide as a catalyst and adding water, and by dehydrochlorination reaction
(JP-A-51-133207), and a method of carrying out in the presence of VCM using cesium, rubidium or a chloride of copper, or alumina as a catalyst (Japanese Patent Publication No. Sho 5).
7-51814) and the like have been proposed.

In any of these methods, the VDC due to the addition of additives, which has a low catalytic activity and a low VDC selectivity.
Also, it has not been industrialized due to difficulty in recovering hydrogen chloride.

Further, to improve the catalytic activity and selectivity, a method of using a catalyst in which cesium chloride is supported on silica gel (Japanese Patent Laid-Open No. 61-197531) is used. A method of alternately carrying out a hydrogen reaction and a desorption / regeneration operation of hydrogen chloride from a catalyst has been published (Japanese Patent Publication No. 12730/1990), but the catalytic activity is insufficient and its decay is suppressed. Practical application is difficult due to reasons such as complexity.

[0015]

Therefore, in the industrialization of the dechlorination reaction of chlorinated hydrocarbons, it was necessary to improve the catalyst performance such as activity, selectivity and life of the catalyst.

More specifically, in the dehydrochlorination reaction of TCE, it was necessary to find a catalyst having a high conversion and a high selectivity, and having a very small decrease in catalytic activity due to long-term use. In addition, in the dehydrochlorination reaction of EDC, a catalyst having a very small decrease in catalytic activity is essential.

[0017]

The present inventors have arrived at the present invention as a result of extensive studies to achieve industrialization of dehydrochlorination reaction by improving the catalytic performance of chlorinated hydrocarbons.

That is, in the present invention, as a catalyst for dehydrochlorination reaction, a catalyst in which cesium nitrate is supported on a silica gel carrier is used, and the catalyst and chlorinated hydrocarbon are brought into contact with each other to react.

More specifically, the catalyst and TCE are brought into contact with each other to produce VDC and hydrogen chloride by a dehydrochlorination reaction, and EDC is dehydrochlorinated by using the above catalyst to produce VCM and chlorine. It produces hydrogen.

As a result, in both cases of TCE dehydrochlorination reaction and EDC dehydrochlorination reaction, high activity and high selectivity of the catalyst can be achieved, and further, the activity associated with the continuation of the dehydrochlorination reaction can be achieved. , The attenuation of selectivity was extremely small. Even better, the activity of the catalyst, which has been reduced by long-term use, is such that heated nitrogen, helium, hydrogen, etc.
By circulation of a gas inert to the dehydrochlorination reaction (hereinafter referred to as an inert gas), regeneration such as initial activity and selectivity can be achieved at the same time, and the present invention has been completed.

[0021]

The present invention will be described in more detail below. The case where the present invention is applied to the production of VDC by the dehydrochlorination reaction of TCE and the production of VCM by the dehydrochlorination reaction of EDC will be described. However, other similar saturated chlorinated hydrocarbons are used as raw materials. To produce propylene oxide (hereinafter, referred to as PO) by dehydrochlorination reaction of propylene chlorohydrin (hereinafter, referred to as PCH), and to produce chloroprene by dehydrochlorination reaction of 3,4-dichloro-1-butene. It is natural that we can adapt.

In the method of the present invention, among various cesium salts, cesium nitrate is made into an aqueous solution with distilled water, and the aqueous solution is circulated and contact-impregnated with silica gel which is generally commercially available.

At this time, 1 wt% or more and 50 wt% or less of the total weight of the silica gel supporting cesium nitrate,
Preferably, the silica gel is impregnated until 10 wt% or more and 30 wt% or less becomes cesium nitrate.

Silica gel impregnated with cesium nitrate is once molded in a tablet molding machine and then crushed. After that, of the crushed cesium nitrate-impregnated silica gel, one having a particle size in the range of 0.7 to 1 mm was heated in air to 400 ° C., and water contained therein was removed by drying. Used as a catalyst for dehydrochlorination reaction.

Regarding the method for supporting cesium nitrate on silica gel, various known general methods can be used as long as the supported amount of cesium nitrate on silica gel is a regulated amount and is uniformly dispersed at each position of the catalyst. The supporting method does not matter.

In the present invention, the chlorinated hydrocarbon to be dehydrochlorinated has 2 to 4 carbon atoms and contains at least one hydrogen atom and one chlorine atom. For example, EDC, TCE, PCH.
Etc.

Contacting the chlorinated hydrocarbon with a catalyst,
As a method for carrying out the dehydrochlorination reaction, a catalyst is fixed inside a glass tube kept at a constant temperature by an electric heater, and a certain amount of chlorinated hydrocarbon is intermittently supplied to this, a so-called pulse reaction method. Similarly, a fixed bed flow reaction system was used in which a chlorinated hydrocarbon was continuously supplied at a constant flow rate to a glass tube reactor in which a constant temperature was maintained by an electric heater and a catalyst was filled inside.

At this time, the reaction temperature is usually 150 ° C.
The range of ≧ -450 ° C is better, and the range of ≧ 250 ° C-40
The range of 0 ° C. or lower is particularly preferable. If the reaction temperature is lower than 150 ° C, a sufficient reaction rate cannot be obtained, and if it exceeds 450 ° C, the desired product (for example, VDC in the case of TCE dehydrochlorination reaction, VCM in the case of EDC is It becomes economically disadvantageous that the selectivity of () falls, a heat source with high enthalpy is required, and energy consumption increases.

As a method of supplying the chlorinated hydrocarbon as a raw material to the reactor, in the case of a pulse reaction system, a certain amount of an inert gas is constantly circulated in the reactor and is placed at a position upstream of the reactor. , A syringe was used to inject a fixed amount at a fixed interval.

Further, in the fixed bed flow reaction system, chlorinated hydrocarbon as a raw material is mixed in advance with an inert gas until a predetermined concentration is reached, and this is then fed from the upstream portion of the reactor at a constant flow rate. Introduced.

The raw material supply method using an inert gas is intended to facilitate the gas chromatography described later. Even if the raw material chlorinated hydrocarbon is directly gasified and introduced into a reactor, particularly a fixed bed flow reactor. It doesn't matter.

Further, the reaction pressure is not particularly limited, and it can be carried out under normal pressure, increased pressure or reduced pressure, but in the embodiment of the present invention, the introduction of the raw material gas body is under increased pressure. ..

In any of the reaction systems, the amount of each product after the reaction and the unreacted residual amount of the raw material chlorinated hydrocarbons are introduced into the gas chromatography directly from the downstream side of the reactor, that is, the so-called outlet. Was measured, and the conversion rate and selectivity were calculated.

Further, as a method of regenerating the catalyst used for the long-time dehydrochlorination reaction, the introduction of only chlorinated hydrocarbons into the reactor is stopped and the inert gas is passed through the reaction by an electric heater. The temperature of the vessel is 350 ° C or higher, preferably 40
The temperature was raised to around 0 ° C., and the temperature was maintained for a certain period of time. After this catalyst regeneration treatment, the temperature was lowered to a predetermined reaction temperature again, the supply of the raw material chlorinated hydrocarbon was started, and the evaluation was performed by the conversion rate and the selectivity.

[0035]

EFFECTS OF THE INVENTION According to the method of the present invention, in the dechlorination reaction of chlorinated hydrocarbons, high activity, high selectivity, and very little reduction in activity and selectivity due to long-term use, etc. Was improved. Even better, the catalytic activity, which was slightly reduced by long-term use, was reproducible in a simple way (high temperature inert gas flow). Therefore, the method of the present invention is industrially extremely significant as compared with the conventional method.

[0036]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

In this specification, the conversion rate and the selectivity are calculated by the following equations. Conversion rate [%] = (F−R) / F × 100 F; Supply amount of chlorinated hydrocarbon [mol] R; Remaining amount of chlorinated hydrocarbon [mol] Selectivity [%] = P / C × 100 P: amount of target product produced [mol] C: amount of reaction product excluding hydrogen chloride [mol]

(Example 1) The dehydrochlorination reaction of TCE was carried out by the pulse reaction system shown in FIG.

Cesium nitrate was made into an aqueous solution with distilled water and impregnated on a commercially available silica gel. At this time, the aqueous solution concentration of cesium nitrate was cesium nitrate based on the combined weight of silica gel and cesium nitrate after removing water. The amount is 20
It was carried out while preparing so as to be wt%. Further, this cesium nitrate-impregnated silica gel was once molded with a tablet molding machine and then pulverized to have a particle size of 0.7 to 1 mm.
The catalyst was left to stand in the air at a temperature of 400 ° C. for 2 hours to dry and remove water.

The reactor has an inner diameter of 4 mm and a length of 200.
Using a glass tube of mm, 50 mg of the catalyst was filled and fixed therein. This reactor is further provided with a catalyst packed bed (1)
The temperature was measured with a thermocouple (2) and the temperature was adjusted with a temperature controller (4) so that a constant temperature of 300 ° C was maintained by the electric heater (3).

In this state, hydrogen gas, which is inactive to the dehydrochlorination reaction, was introduced so that the flow rate was constant at 60 ml / min. As a pretreatment of the catalyst, only hydrogen was circulated for 2 hours, and then 2 μl of TCE was intermittently supplied from the sample injection port (6) for a predetermined number of times at an interval of 15 minutes every 2 μl. A gas chromatography (5) was directly connected to the outlet of the reactor to measure the amount of various reaction products including VDC after the dehydrochlorination reaction and TCE remaining unreacted. I asked.

Further, in order to observe the state of catalyst regeneration, injection of only TCE as a raw material was stopped and hydrogen gas was circulated.
After the temperature of the catalyst packed bed was raised to 400 ° C. and kept in this state for 30 minutes, 2 μl of TCE was started again by the initial method, and changes in conversion rate and selectivity at that time were confirmed.

FIG. 3 shows the result of this pulse reaction.

Comparative Example 1 For comparison with Example 1 above,
Similarly, a case where cesium salt other than cesium nitrate is supported on silica gel in the pulse reactor shown in FIG. 1 will be described.

As the catalyst, cesium chloride, cesium carbonate, and cesium sulfate were loaded on silica gel in an amount of 20 wt% in the same manner as in Example 1 of the present specification, and were placed in a pulse reactor.
Similarly, 50 mg was filled and fixed. Also, the reaction conditions are the same as in Example 1 under the same conditions under the flow of hydrogen gas.
2 hours after the catalyst pretreatment, add 2μ of TCE with a syringe.
It was supplied intermittently at intervals of 15 minutes. Further, only the hydrogen gas was subjected to a regeneration treatment for 30 minutes while the temperature of the catalyst packed bed was raised to 400 ° C., and then the conversion rate and the selectivity were measured again.

FIG. 3 shows the results of the pulse reaction of this Comparative Example 1.

Example 2 The dehydrochlorination reaction of TCE was carried out by the fixed bed flow reaction system shown in FIG.

As the catalyst, the same silica gel supporting 20% by weight of cesium nitrate as in Example 1 was used, and a glass tube reactor having an inner diameter of 10 mm and a length of 200 mm was used.
1 g of the catalyst was filled and fixed. Furthermore, while the temperature of the catalyst packed bed (1) of this reactor is measured by the thermocouple (2), the temperature is controlled by the temperature controller (4) so that the predetermined temperature is maintained by the electric heater (3). did.

TCE as a raw material was continuously supplied in advance in a hydrogen gas by a micro feeder (7) so that a predetermined concentration (TCE partial pressure was constant) was obtained. This mixed gas of TCE and hydrogen was introduced into the catalyst packed bed (1) at a constant flow rate of 75 ml / min.

In this state, the dehydrochlorination reaction is continuously carried out, the reactor outflow gas is sampled from the sampling port (8) located at the outlet of the reactor every predetermined time, and the sample is analyzed by gas chromatography (5). The amounts of various reaction products including VDC after the dehydrochlorination reaction and TCE remaining unreacted were measured, and the conversion rate and the selectivity were calculated from the measured values. The temperature of the catalyst packed bed (1) is 300 ° C, 350 ° C, 400 ° C,
The results of carrying out the dehydrochlorination reaction of TCE at 450 ° C. are shown in FIG.

At this time, T in the mixed gas of TCE and hydrogen
CE concentration, that is, TCE partial pressure is 0.02-0.11 atm
However, there was no effect on the conversion rate and selectivity per unit contact time of TCE with the catalyst.
Therefore, in the second embodiment, the TCE partial pressure is set to 0.05 atm.
And Furthermore, in this state, the TCE dehydrochlorination reaction
There was no change in conversion rate and selectivity after continuing for 4 hours or more.

(Comparative Example 2) For comparison with Example 2 described above,
Similarly, in the fixed bed flow reactor shown in FIG. 2, cesium nitrate was loaded on silica-alumina other than silica gel, titania, and activated carbon in the same manner as in Example 1 above. Dehydrochlorination of TCE was carried out under the same fixed bed reactor and reaction conditions as in Example 2, but catalytic activity, so-called TCE dehydrochlorination, was hardly observed.

(Embodiment 3) The same as FIG.
The case where the amount of cesium nitrate supported on silica gel is changed from 5 wt% to 50 wt% in the fixed bed flow reactor shown in FIG.

As the catalyst, cesium nitrate was used in the same manner as in Example 1 above, and the amount of cesium nitrate was changed to silica gel.
They were supported and prepared so as to be 5% by weight, 10% by weight, 20% by weight and 50% by weight, respectively. With respect to each of these catalysts, the reaction temperature, that is, the temperature of the catalyst packed bed (1) was set to 300 ° C., the fixed bed reactor and the reaction conditions were the same as in Example 2 above, and the dehydrochlorination reaction of TCE was performed. The conversion rate and the selectivity were measured for each of these, and the results are shown in Table 1.

[0055]

[Table 1]

Example 4 The dehydrochlorination reaction of EDC was carried out by the pulse reaction system shown in FIG.

As the catalyst, the same silica gel supporting 20% by weight of cesium nitrate as in Example 1 was used, and 75 mg was fixed in the pulse reactor. The temperature of the catalyst packed bed (1) was kept constant at 350 ° C., and the other reaction conditions were exactly the same as in Example 1 above, under the same conditions under the flow of hydrogen gas, and the catalyst pretreatment was carried out. After 2 hours, 2 μl of EDC was intermittently supplied at intervals of 15 minutes by a syringe.

At the outlet of the reactor, the amounts of various reaction products including VCM after dehydrochlorination reaction and EDC remaining unreacted were measured by gas chromatography (5),
From this, the conversion rate and selectivity were determined. Furthermore, changes in the conversion rate and the selectivity were confirmed after carrying out a catalyst regeneration treatment for 30 minutes in a state where the catalyst packed bed was heated to 400 ° C. while flowing only hydrogen gas.

FIG. 5 shows the result of this pulse reaction.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a pulse reaction device used in Examples 1 and 4 of the present invention and Comparative Example 1.

FIG. 2 is an explanatory diagram of a fixed bed flow reactor used in Examples 2 and 3 of the present invention and Comparative Example 2.

FIG. 3 is an actual measurement diagram showing the results of Example 1 and Comparative Example 1.

FIG. 4 is an actual measurement diagram showing the results of Example 2.

FIG. 5 is an actual measurement diagram showing the results of Example 4.

[Explanation of symbols] 1 ... Catalyst packed bed 2 ... Thermocouple 3 ... Electric heater 4 ... Temperature controller 5 ... Gas chromatography 6 ... Sample injection port 7 ... Micro feeder 8 ... Sampling port

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location // C07B 61/00 300

Claims (4)

[Claims] 1. A dehydrochlorination method comprising contacting a chlorinated hydrocarbon with a catalyst in which cesium nitrate is supported on a silica gel carrier among various cesium salts. 2. The dehydrochlorination method according to claim 1, wherein the chlorinated hydrocarbon has 2 to 4 carbon atoms. 3. The dehydrochlorination method according to claim 1, wherein the product after the dehydrochlorination reaction with 1,1,2-trichloroethane as the chlorinated hydrocarbon is vinylidene chloride. 4. The dehydrochlorination method according to claim 1, wherein the product obtained after the dehydrochlorination reaction of chlorinated hydrocarbon with 1,2-dichloroethane is a vinyl chloride monomer.