CN103819307A - Method for preparing chlorobenzene, p-dichlorobenzene and o-dichlorobenzene in benzene chlorination - Google Patents

Abstract

The method for preparing chlorobenzene, p-dichlorobenzene and o-dichlorobenzene during chlorination of benzene relates to a method for preparing chemical raw materials. Selective catalyst for drying benzene and chlorine gas, benzene and chlorine gas should have sufficient residence time, react at a set reaction temperature, produce p-dichlorobenzene, and simultaneously obtain o-dichlorobenzene, and co-produce monochlorinated benzene ;Using an outer circulation reactor, using benzene and chlorine as raw materials, using metal sulfide as a catalyst to produce dichlorobenzene, and at the same time, it can co-produce monochlorinated benzene, and rely on the introduction of chlorine gas and the generated hydrogen chloride as power to make the material form a circulation In order to obtain good stirring, promote the mixing, diffusion, heat transfer and mass transfer between the reactants; the reaction speed is fast and the production capacity is high; the ratio of p-dichlorobenzene to o-dichlorobenzene is large, there is no by-product of polychlorinated benzene, and Adjust the proportion of monochlorinated benzene and dichlorobenzene in the product according to the demand, which has high flexibility and large operating flexibility.

Description

Method for preparing chlorobenzene, p-dichlorobenzene and o-dichlorobenzene during chlorination of benzene

technical field

The present invention relates to a method for preparing chemical raw materials, in particular to a method for simultaneously preparing chlorobenzene, p-dichlorobenzene and o-dichlorobenzene through chlorination of benzene.

Background technique

P-dichlorobenzene is an important raw material for organic chemical synthesis. It is widely used as a pesticide intermediate, as a fumigant insecticide, fabric mothproof agent, mildewproof agent, and air deodorizer. Most of it is used to make sanitary balls. For example, 32% of p-dichlorobenzene is used as deodorant in the United States. Western Europe accounted for 50%. In Japan, p-dichlorobenzene used for deodorant and anti-moth agents accounts for 70% of its total production capacity;

An important use of p-dichlorobenzene is as an intermediate of high-performance engineering plastic polyphenylene sulfide. Polyphenylene sulfide has excellent properties such as high temperature resistance, radiation resistance, ablation resistance, high toughness and high stability. It is used in electronics, Electrical, mechanical manufacturing and aerospace and other fields;

P-dichlorobenzene can also be used to synthesize 2,5-dichloronitrobenzene, which is an intermediate for the synthesis of dyes such as scarlet base GG, red base 3GL, active bright yellow and red RC, etc. 4-trichloro-2-hydroxydiphenyl ether) is the main raw material of new antibacterial agents;

A small amount of p-dichlorobenzene is also used in extreme pressure lubricants and corrosion inhibitors. This product can also be used as solvent, mutagen, etc.

Ortho-dichlorobenzene (1,2-dichlorobenzene) is an excellent solvent, which can be used as a solvent for wax, gum, resin, tar, rubber, oil and asphalt. It is used in dyes such as Shihlin black and Shihlin yellow brown The solvent 1,2-dichlorobenzene is used in the production of high-grade pigments, drug chlorhexidine, and polyurethane raw material TDI;

This product can be used to make insecticides for termites, locusts, and borers, for the production of triclosulphate, thriofen-methyl, and novyl, and for the synthesis of catechol, fluorochloroaniline, and 3, 4-Dichloroaniline and o-phenylenediamine.

As an anti-rust agent and degreasing agent, o-dichlorobenzene can remove carbon and lead on engine parts, remove coatings on metal surfaces without corroding metals, and remove sulfur in lighting gases. It can be used as an ingredient of metal polishing agent;

O-dichlorobenzene dyes are also used in the industry to manufacture vat blue CLB and vat blue CLG, etc.; polymer wet spinning solvents to reduce fiber heat shrinkage;

O-dichlorobenzene can also be used as epoxy resin diluent, coolant, heat exchange medium. Production of long-acting sulfonamides and other medicines.

The demand ratio of p-dichlorobenzene and o-dichlorobenzene should be at least 3 to 1, and the larger the proportion of p-dichlorobenzene, the better. The use of dichlorobenzene is still expanding and the amount is increasing day by day. The current production method of dichlorobenzene cannot meet the demand of the market. There are roughly methods for people to obtain dichlorobenzene: 1) It is separated from the heavy component by-products produced by chlorinated benzene, but the quantity is extremely limited; 2) Using ferric chloride as a catalyst, chlorinated benzene and chlorine gas are used as raw materials to further in-depth Dichlorobenzene is obtained by chlorination, and chlorobenzene is obtained after benzene chlorination, water washing, alkali washing, and rectification, which will greatly increase the raw material cost of dichlorobenzene, and the speed of generating dichlorobenzene by chlorination of chlorobenzene Also very slow, equipment investment is bigger; 3) generally all adopt batch reactor, in the benzene that contains ferric trichloride, feed chlorine continuously and make dichlorobenzene, this kind method scale is small, and product composition is unstable, and by-product The amount of polychlorobenzene increases, which is not conducive to post-treatment; 4) column continuous reactor, benzene, ferric chloride catalyst and chlorine are added continuously, due to the lack of necessary stirring and no suitable catalyst, the production capacity is low, and the production capacity is low. Neighborhood imbalance, equipment investment is large, not suitable for large-scale production. The key to producing dichlorobenzene is to choose a suitable reactor, which should have the characteristics of high production capacity, small volume and simple structure. It is more important to select high activity, high para-selectivity, cheap and non-toxic catalysts.

Contents of the invention

The object of the present invention is to provide a method for preparing chlorobenzene, p-dichlorobenzene and ortho-dichlorobenzene when benzene is chlorinated. The method uses benzene and chlorine as raw materials and metal sulfide as a catalyst to prepare dichlorobenzene. Fast speed, high production capacity, large ratio of p-dichlorobenzene to o-dichlorobenzene, no by-products of polychlorinated benzene, and the ratio of monochlorinated benzene and dichlorobenzene in the product can be adjusted according to demand, with high flexibility High performance and large operating flexibility.

The purpose of the present invention is achieved through the following technical solutions:

When benzene is chlorinated, prepare the method for chlorobenzene, p-dichlorobenzene and ortho-dichlorobenzene, said method comprises continuously passing into the dry benzene containing high activity, high p-dichlorobenzene selectivity catalyst in the outer loop reactor, Chlorine gas, benzene and chlorine gas should have sufficient residence time, react at a set reaction temperature, produce p-dichlorobenzene, and simultaneously obtain o-dichlorobenzene, and co-produce monochlorinated benzene;

Among them: the aspect ratio of the outer loop reactor = H/D is generally 10-30, preferably 20; the pipe diameter ratio = D/d is generally 1.5-0.5, preferably 1.0; the retention of benzene in the reactor The general residence time is 0.5-1.5h, preferably 0.8-1.2h, preferably 1.0h; the amount of benzene introduced per cubic meter of volume loop reactor, that is: air lift tube, can reach a maximum of 2.0 tons/ hours, preferably 1.5 tons/hour, preferably 0.8 tons/hour; the amount of chlorine gas should be between 250m3/h (11.20kmole) and 650m3/h (29.07kmole); Benzene-selective catalysts include but are not limited to antimony pentasulfide, antimony trisulfide, ferric trisulfide, ferric chloride+S, pyrite+S, and the ratio of the latter two to sulfur should meet the requirement of iron and sulfur. The molar ratio is 2:3; the catalyst used is crushed to less than 10 microns, preferably less than 5 microns, and the best less than 2 microns; the amount of catalyst used is 0.06 (W/%)-0.1 (W/%) of the amount of benzene added; the reaction The temperature should be between 40°C and 50°C;

In the method for preparing chlorobenzene, p-dichlorobenzene and o-dichlorobenzene during the chlorination of benzene, the water content in the benzene should be ≦100×10-6 weight fraction, preferably ≦50×10-6 weight fraction .

The method for preparing chlorobenzene, p-dichlorobenzene and o-dichlorobenzene during the chlorination of benzene, the method for dehydrating benzene, including but not limited to solid alkali drying, molecular sieve dehydration, anhydrous calcium chloride dehydration, salt dehydration . Advantage and effect of the present invention are.

Description of drawings

Figure 1 is a schematic diagram of the working state of the loop reactor of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the embodiments shown in the accompanying drawings.

The chlorination of benzene to dichlorobenzene is a reaction of gas (chlorine, hydrogen chloride), liquid (benzene, chlorobenzene, dichlorobenzene) and solid (catalyst), benzene and chlorine generate chlorobenzene and dichlorobenzene under the action of the catalyst, and release them at the same time Moles of hydrogen chloride, chlorobenzene and chlorine gas generate dichlorobenzene under the action of the catalyst and release equimolar hydrogen chloride at the same time. The volume of the gas does not change during the reaction, which creates conditions for the application of the loop reactor. In the upper and lower communication, the two sides of the reactor are separated in the middle, and there is an obvious gravity difference between the gas-saturated reactant and the gas-free product, which means that the static pressure difference in the fluid makes the material form a circulation and continuously enter the reactor. The high flow rate of chlorine produces a stronger driving force, which promotes the circulation. The loop reactor is conducive to the mixing, diffusion, heat transfer and mass transfer between the reactants, and can obtain good stirring without causing the safety problem of the sealant due to the additional transmission device.

Exothermic reaction during benzene chlorination reaction, too high reaction temperature will reduce the ratio of para-products in the product dichlorobenzene and increase the possibility of generating polychlorobenzene, so the heat of reaction should be removed in time to make the reaction at a certain temperature next. Compared with the inner loop reactor, the outer loop reactor has a larger heat exchange area, and the heat transfer requirements can be achieved with ordinary circulating cooling water, avoiding the complexity of cooling and heat transfer.

As shown in the attached figure, the loop reactor is mainly composed of 1) reactor main pipe (air lift pipe), 2) external circulation pipe, 3) material outlet, 4) chlorine gas nozzle, 5) benzene feed inlet, 6) gas-liquid Separator, 7) Exhaust gas discharge pipe and 8) Cooling jacket etc.

Several kinetic parameters that determine the effect of the reaction are:

Length-to-diameter ratio = H/D H is the total height of the reactor main pipe, in meters; D is the diameter of the reactor main pipe, in meters. The aspect ratio determines the circulation effect, generally 10-30, preferably 20.

Diameter ratio = D/d D is the diameter of the reactor main pipe, m; d is the diameter of the circulation pipe, m. The pipe diameter ratio determines the circulation volume, generally 1.5-0.5, preferably 1.0.

Residence time (h) = W/V W is the reactor volume, m3; V is the velocity of benzene entering the reactor, m3/h. The residence time is short, the reaction depth is not enough, the amount of benzene and chlorobenzene is large, and the proportion of polychloride increases if the residence time is too long. Generally, the residence time is 0.5-1.5h, preferably 0.8-1.2h, most preferably 1.0h.

Through benzene volume. If the amount of benzene added is too large, in one case, the reaction will be incomplete, which will increase the separation burden and increase energy consumption; in the other case, the heat exchange capacity will be insufficient, and a cryogenic medium will be used for heat exchange, which will increase the investment and increase the operation. complexity. For each cubic meter volume of the loop reactor (air lift tube), the maximum can be 2.0 tons/hour. It is preferably 1.5 tons/hour, most preferably 0.8 tons/hour.

Chlorine gas intake. The last thing you want is trichlorobenzene or even polychlorobenzene, and it will not make the tail gas hydrogen chloride contain free chlorine, which will increase the difficulty of post-treatment. The content of mixed dichlorobenzene in the product should not exceed 85 (W/%). If The content of dichlorobenzene in the product is too low, the yield is low, the reaction is incomplete, the burden of separation is increased, and the energy consumption is increased. The content of mixed dichlorobenzene in the product must not be lower than 40 (W/%). Therefore, according to the requirements for mixing dichlorobenzene and chlorobenzene, the amount of chlorine gas introduced should be between 250m3/h (11.20kmole) and 650m3/h (29.02kmole).

catalyst. Usually the production of chlorinated benzene by the chlorination of benzene uses ferric chloride or the direct reaction of iron and chlorine as a catalyst, but it is not applicable to the reaction of mixed dichlorobenzene as the main product. One is that the reaction rate is low, and the same amount of products It is necessary to greatly increase the volume of the equipment, which increases the land occupation and primary investment. On the other hand, the selectivity of the catalyst to p-dichlorobenzene is not high, and the ratio of p-position to ortho-dichlorobenzene is usually only about 2.2, which deviates greatly from the actual demand in the market and affects normal sales. The ratios of p- and o-dichlorobenzene produced by the catalysts used in the present invention are all above 3 to 1. These catalysts include but are not limited to antimony pentasulfide, antimony trisulfide, ferric trisulfide, ferric chloride+S , pyrite+S, etc., the ratio of sulfur added by the latter two should meet the molar ratio of iron to sulfur is 2:3; the catalyst used must be crushed to below 10 microns, preferably below 5 microns, and best below 2 microns, so In order to be evenly dispersed and suspended in the raw material benzene, it is convenient to add and beneficial to the reaction; the amount of catalyst used in the present invention is 0.06 (W/%)-0.1 (W/%) of the amount of benzene added.

The reaction temperature also has a great influence on the production of dichlorobenzene. When the chlorination reaction temperature is 30°C, 40°C, 50°C, 60°C, and 70°C, the chlorination depth (the number of moles of chlorine reacted and the moles of benzene added) The ratio of the number) is mostly at 1.74, which basically remains unchanged, indicating that the reaction temperature has little influence on the reaction rate. However, the ratios of p-dichlorobenzene and o-dichlorobenzene obtained are quite different, which are 3.42, 3.33, 3.24, 3.13 and 2.86 respectively, so the reaction temperature should be selected between 30°C and 60°C, because the temperature of circulating water in summer is high At 30°C, the heat cannot be removed. In order to obtain a larger pair ratio, the reaction temperature should be selected between 40°C and 50°C.

Coking benzene (conforming to GB/T 2283-2008) can be used in the production of mixed dichlorobenzene, but it must be dehydrated before adding to the reactor, so that the water content in benzene is ≦100×10-6 weight fraction, preferably ≦50 ×10-6 weight fraction. Dehydration methods include but are not limited to solid alkali drying, molecular sieve dehydration, anhydrous calcium chloride dehydration, salt dehydration, etc.

The specific process is as follows: In the outer loop reactor with an aspect ratio of 10-30 and a pipe diameter ratio of 1.5-0.5, the volume of the loop reactor (air lift tube) per cubic meter is 0.8-1.5 tons/ Benzene with a water content of ≦100×10-6 weight fraction after drying is fed at a speed of one hour, and the catalyst is antimony pentasulfide, antimony trisulfide, ferric trisulfide, ferric chloride+S, pyrite+S, etc. Suspend in benzene at 0.06(W/%)-0.1(W/%). At the same time, feed chlorine gas into the reactor at a speed of 250m3/h (11.16kmole)-650m3/h(29.02kmole), and open the jacket to cool The water is used to adjust the amount of cooling water to control the temperature of the material in the reactor between 40°C and 50°C. The chlorinated liquid is continuously extracted from the discharge port of the side line of the gas-liquid separator on the upper part of the reactor, and the discharge valve continuously adjusts the discharge volume to ensure The liquid level of the gas-liquid separator is at a certain position. The hydrogen chloride produced by the reaction is separated into gas and liquid, and enters the graphite condenser to separate the entrained benzene and chloride solution. The benzene and chloride solution are returned to the reactor, and the hydrogen chloride is absorbed by water into hydrochloric acid for other users. The chlorinated solution is washed with water, washed with alkali and dried, and rectified to separate unreacted benzene and chlorinated benzene. The mixed dichlorobenzene is crystallized to obtain p-dichlorobenzene, and pure o-dichlorobenzene is obtained through rectification.

Embodiment one:

The main products are p-dichlorobenzene and o-dichlorobenzene.

In the outer loop reactor with an aspect ratio of 20 and a tube diameter ratio of 1, the water (anhydrous calcium chloride) dried For benzene with water content ≦100×10-6 weight fraction, the catalyst is ferric trisulfide, 0.08 (W/%) is suspended in benzene, and at the same time, the volume of loop reactor (air lift tube) per cubic meter is 400m3/h ( Chlorine gas was introduced into the reactor at a speed of 17.9kmole), and the jacket cooling water was opened to adjust the amount of cooling water to control the temperature of the material in the reactor at 45°C. Liquid, the discharge valve continuously adjusts the discharge volume to ensure that the liquid level of the gas-liquid separator is at a certain position. The hydrogen chloride produced by the reaction is separated into gas and liquid, and enters the graphite condenser to separate the entrained benzene and chloride solution. The benzene and chloride solution are returned to the reactor, and the hydrogen chloride is absorbed by water into hydrochloric acid for other users. The chlorinated solution is washed with water, washed with alkali and dried, and rectified to separate unreacted benzene and chlorinated benzene. The mixed dichlorobenzene is crystallized to obtain p-dichlorobenzene, and then pure o-dichlorobenzene is obtained through rectification.

The composition (W/%) of the obtained chlorinated solution is:

Benzene Monochlorinated Benzene p-Dichlorobenzene o-Dichlorobenzene p/o

3.01 12.04 65.23 19.72 3.31

Embodiment two:

The main products are p-dichlorobenzene and o-dichlorobenzene, and the co-production of chlorinated benzene has a large proportion.

In the outer loop reactor with an aspect ratio of 20 and a tube diameter ratio of 1, the water is passed through (anhydrous calcium chloride) drying For benzene with water content ≦100×10-6 weight fraction, the catalyst is ferric trisulfide, 0.07 (W/%) is suspended in benzene, and at the same time, the volume of the loop reactor (air lift tube) per cubic meter is 609m3/h ( Chlorine gas is introduced into the reactor at a speed of 27.20 kmole), and the jacket cooling water is opened to adjust the amount of cooling water to control the temperature of the material in the reactor at 50°C. Liquid, the discharge valve continuously adjusts the discharge volume to ensure that the liquid level of the gas-liquid separator is at a certain position. The hydrogen chloride produced by the reaction is separated into gas and liquid, and enters the graphite condenser to separate the entrained benzene and chloride solution. The benzene and chloride solution are returned to the reactor, and the hydrogen chloride is absorbed by water into hydrochloric acid for other users. The chlorinated solution is washed with water, washed with alkali and dried, and rectified to separate unreacted benzene and chlorinated benzene. The mixed dichlorobenzene is crystallized to obtain p-dichlorobenzene, and then pure o-dichlorobenzene is obtained through rectification.

The composition (W/%) of the obtained chlorinated solution is:

Benzene Monochlorinated Benzene p-Dichlorobenzene o-dichlorobenzene p/o

9.86 50.01 30.78 9.35 3.29

Claims (3)

1. The method for preparing chlorobenzene, p-dichlorobenzene and ortho-dichlorobenzene during benzene chlorination, is characterized in that, described method comprises in the external circulation reactor, continuously passes into the selectivity that contains high activity, high p-dichlorobenzene Dry benzene and chlorine gas as a catalyst, benzene and chlorine gas should have sufficient residence time, and react at a set reaction temperature to produce p-dichlorobenzene, simultaneously obtain o-dichlorobenzene, and co-produce monochlorinated benzene; Among them: the aspect ratio of the outer loop reactor = H/D is generally 10-30, preferably 20; the pipe diameter ratio = D/d is generally 1.5-0.5, preferably 1.0; the retention of benzene in the reactor The general residence time is 0.5-1.5h, preferably 0.8-1.2h, preferably 1.0h; the amount of benzene introduced per cubic meter of volume loop reactor, that is: air lift tube, can reach a maximum of 2.0 tons/ hours, preferably 1.5 tons/hour, preferably 0.8 tons/hour; the amount of chlorine gas should be between 250m3/h (11.20kmole) and 650m3/h (29.07kmole); Benzene-selective catalysts include but are not limited to antimony pentasulfide, antimony trisulfide, ferric trisulfide, ferric chloride+S, pyrite+S, and the ratio of the latter two to sulfur should meet the requirement of iron and sulfur. The molar ratio is 2:3; the catalyst used is crushed to less than 10 microns, preferably less than 5 microns, and the best less than 2 microns; the amount of catalyst used is 0.06 (W/%)-0.1 (W/%) of the amount of benzene added; the reaction The temperature should be between 40°C and 50°C. 2. the method for preparing chlorobenzene, p-dichlorobenzene and ortho-dichlorobenzene during benzene chlorination according to claim 1, is characterized in that, water content should be less than or equal to 100 * 10-6 weight fraction in the described benzene, most Preferably ≦50×10-6 weight fraction. 3. the method for preparing chlorobenzene, p-dichlorobenzene and ortho-dichlorobenzene during the chlorination of benzene according to claim 2, is characterized in that, the method for described benzene dehydration includes but not limited to solid alkali drying, molecular sieve dehydration , Anhydrous calcium chloride dehydration, salt dehydration.

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