阅读说明：本技术 一种六氯苯选择性加氢脱氯的方法 (Selective hydrogenation dechlorination method for hexachlorobenzene ) 是由 张志华 王煦 张馨艺 李磊 蒋达洪 崔宝臣 于 2020-12-10 设计创作，主要内容包括：本发明涉及氯代芳烃选择性加氢脱氯的方法技术领域,更具体地,涉及一种六氯苯选择性加氢脱氯的方法。一种六氯苯选择性加氢脱氯的方法,步骤为：在低于80℃的温度下将六氯苯完全溶解于溶剂中,形成六氯苯常温饱和溶液,再将六氯苯常温饱和溶液与氢气混合均匀,得到气液混合物；将气液混合物以液相进料方式泵入第一反应器内,反应得到第一反应物混合体；气液分离得到的第一液体产物再泵入第二反应器内,反应得到第二反应物混合体；气液分离,得到第二液体产物,用精馏塔分离得到二氯苯和氯苯。本发明通过两级反应器对六氯苯进行选择性加氢脱氯反应,第一反应器反应后得到的第一液体产物进入第二反应器内再次反应,提高产物的得率；选择性好,效率高,实用性强。(The invention relates to the technical field of a selective hydrogenation and dechlorination method of chlorinated aromatic hydrocarbon, and in particular relates to a selective hydrogenation and dechlorination method of hexachlorobenzene. A method for selective hydrogenation dechlorination of hexachlorobenzene comprises the following steps: completely dissolving hexachlorobenzene in a solvent at the temperature lower than 80 ℃ to form a normal-temperature saturated hexachlorobenzene solution, and uniformly mixing the normal-temperature saturated hexachlorobenzene solution with hydrogen to obtain a gas-liquid mixture; pumping the gas-liquid mixture into a first reactor in a liquid-phase feeding mode, and reacting to obtain a first reactant mixture; pumping a first liquid product obtained by gas-liquid separation into a second reactor, and reacting to obtain a second reactant mixture; gas-liquid separation to obtain a second liquid product, and separation by a rectifying tower to obtain dichlorobenzene and chlorobenzene. According to the invention, the hexachlorobenzene is subjected to selective hydrogenation and dechlorination reaction through the two-stage reactor, and a first liquid product obtained after the reaction of the first reactor enters the second reactor for reaction again, so that the yield of the product is improved; the selectivity is good, the efficiency is high, and the practicability is strong.)

1. A method for selective hydrogenation dechlorination of hexachlorobenzene is characterized by comprising the following steps:

completely dissolving hexachlorobenzene in a solvent at the temperature lower than 80 ℃ to form a normal-temperature saturated hexachlorobenzene solution, and uniformly mixing the normal-temperature saturated hexachlorobenzene solution with hydrogen to obtain a gas-liquid mixture;

loading a hydrogenation reaction catalyst into the first reactor and the second reactor, and activating the catalyst before/after loading into the reactors;

pumping the prepared gas-liquid mixture into a first reactor filled with an activated hydrogenation reaction catalyst in a liquid-phase feeding mode, and reacting to obtain a first reactant mixture;

carrying out gas-liquid separation on the first reactant mixture to obtain a first gas product and a first liquid product;

pumping the first liquid product into a second reactor filled with an activated hydrogenation reaction catalyst for reaction to obtain a second reactant mixture;

carrying out gas-liquid separation on the second reactant mixture to obtain a second gas product and a second liquid product;

and condensing the second liquid product, and separating in a rectifying tower to obtain the solvent, dichlorobenzene, chlorobenzene and polychlorinated benzene.

2. The selective hydrodechlorination of hexachlorobenzene according to claim 1, wherein the temperature at which said gas-liquid mixture is prepared is in the range of 25 ℃ to 80 ℃.

3. The process of claim 1, wherein the hydrogenation catalyst is supported on a carrier.

4. The selective hydrodechlorination process of hexachlorobenzene as claimed in claim 3, wherein the active component of the hydrogenation catalyst is one or two of platinum or palladium, or the carrier is any one of alumina, titania or magnesia.

5. The method for selective hydrodechlorination of hexachlorobenzene according to claim 1, wherein the mass content of active components in the hydrogenation catalyst is 0.1-1.0%.

6. The process according to claim 1, characterized in that the activation conditions are: the reducing gas is hydrogen, and the space velocity GHSV is 500-5000 h^-1The pressure is 0.1-3.0 MPa, the temperature is 200-300 ℃, and the activation time is 2-5 h.

7. The selective hydrodechlorination process of hexachlorobenzene according to claim 1, wherein the inlet temperature of the first reactor is 70-150 ℃, the pressure in the reactor is 0.1-1.0 MPa, and H is₂The molar ratio of the hexachlorobenzene to hexachlorobenzene is 10-20, and the weight space velocity of hexachlorobenzene is 1.0-2.0 h^-1；

Or, the inlet temperature of the second reactor is 80-120 ℃, and the reaction is carried outThe pressure in the device is 0.1-1.0 MPa, H₂The mol ratio of the first liquid product to the second liquid product is 1-10, and the weight space velocity of the hexachlorobenzene is 0.5-1.0 h^-1。

8. The selective hydrodechlorination process of hexachlorobenzene according to claim 1, wherein the solvent is any one of benzene, toluene, dichloromethane or chloroform.

9. The method for selective hydrodechlorination of hexachlorobenzene as claimed in claim 1, wherein the first reactant mixture is subjected to gas-liquid separation to obtain a first gas product and a first liquid product, and further comprising the steps of absorbing hydrogen chloride in the first gas product with a hydrogen chloride absorbing solution, and uniformly mixing the normal-temperature saturated solution of hexachlorobenzene with hydrogen in the remaining hydrogen;

or after the second reactant mixture is subjected to gas-liquid separation to obtain a second gas product and a second liquid product, the method also comprises the step of absorbing hydrogen chloride in the second gas product by using a hydrogen chloride absorption solution, and uniformly mixing the normal-temperature saturated solution of hexachlorobenzene and hydrogen with the residual hydrogen.

10. The selective hydrodechlorination method of hexachlorobenzene as claimed in claim 1, wherein the second liquid product is condensed and separated in a rectifying tower to obtain solvent, dichlorobenzene, chlorobenzene and polychlorinated benzene, and further comprising dissolving the separated polychlorinated benzene with the solvent, mixing the dissolved polychlorinated benzene with normal temperature saturated hexachlorobenzene solution, and feeding the mixture into the first reactor, wherein the separated solvent is recovered for dissolving hexachlorobenzene.

Technical Field

The invention relates to the technical field of a selective hydrogenation and dechlorination method of chlorinated aromatic hydrocarbon, and in particular relates to a selective hydrogenation and dechlorination method of hexachlorobenzene.

Background

Hexachlorobenzene (HCB) has a completely symmetrical structure, has the characteristics of long-term residue, bioaccumulation, semi-volatility, high toxicity and the like, can cause serious diseases such as endocrine disorders, reproductive and immune dysfunction, neurobehavioral and developmental disorders and cancers of organisms, and is one of the first 12 Persistent Organic Pollutants (POPs) requiring international action in the stockholm convention. In the environment, hexachlorobenzene is mainly derived from the production process of herbicides and bactericides (quintozene, dichlorvos, chlorothalonil and the like) and is widely applied to agricultural production. According to investigation, at least 600 tons of hexachlorobenzene are produced in the chemical production process every year in China, and the treatment method mainly comprises sealing and burning. The sealing has the risks of leakage, diffusion and the like, and has great hidden danger on the safety of the surrounding ecological environment; the incineration conditions are harsh, the energy consumption is high, and toxic and harmful substances such as dioxin and the like can be generated to cause secondary pollution. Domestic and foreign scholars mainly develop research on degradation of hexachlorobenzene by the following methods, for example: the method comprises the steps of photocatalytic oxidation, microbial degradation, irradiation, electrochemical method and catalytic hydrogenation, wherein the methods have a certain effect on the degradation of hexachlorobenzene, but most methods still stay in a laboratory and a theoretical research stage, and no method suitable for practical application exists at present due to various reasons and difficulties. Therefore, the active search for a highly efficient and environment-friendly hexachlorobenzene treatment method has very important significance.

The HCB catalytic hydrogenation treatment can be quickly converted in a large amount, the hydrogenated product is organic hydrocarbon which can be recycled, and the method has certain economic value, the treatment cost of the HCB is indirectly reduced. Chinese patents 201410246756.4 and 201410244652.X provide a catalyst and a method for catalytic hydrogenation degradation of hexachlorobenzene, the key of the method lies in the activity and stability of the catalyst, hexachlorobenzene is degraded into benzene and hydrogen chloride by a hydrodechlorination mode, the activity of the catalyst is high, and chlorine on hexachlorobenzene is directly and completely removed.

Dichlorobenzene refers to p-dichlorobenzene, o-dichlorobenzene and m-dichlorobenzene, is an important fine chemical raw material, is widely applied to the fields of medicines, solvents, dyes, mildewproof agents, mothproofing agents, deodorants and the like, wherein the demand of the p-dichlorobenzene and the o-dichlorobenzene is large, the p-dichlorobenzene is formally determined to be used as a third-generation novel mildewproof agent to replace naphthalene-made mothballs in 1993 countries, and then the p-dichlorobenzene is rapidly developed due to the advantages of low toxicity and good drug effect, and is also a main production raw material of polyphenylene sulfide in developed countries. The o-dichlorobenzene is a raw material and an intermediate of pesticides, medicines and dyes, is used for preparing chlorofluoroaniline, dichloroaniline, catechol, star-killing anti-gonorrhea drugs, trichloro-insecticidal ester and the like, and can also be used for producing TDI resin.

In fact, if the catalyst and the catalytic reaction process are modified and optimized, and the rate and amount of dechlorination are controlled, it is possible to obtain high value-added intermediates such as dichlorobenzene, chlorobenzene or polychlorinated benzene.

CN103977744A proposes a method for catalytic degradation of hexachlorobenzene, and proposes that a fixed bed is used as a reactor and Al is used₂O₃The technology for preparing benzene by using noble metal loaded with noble metal Pt, Pd, Ag, Ru or Rh as a catalyst and carrying out normal-pressure gas-phase hydrogenation catalysis on chlorinated aromatic hydrocarbon at the temperature of 320-400 ℃. CN103910598A reports a method for preparing cyclohexane by gas phase dechlorination and hydrogenation of chlorinated aromatic hydrocarbon, which is to perform catalytic dechlorination and hydrogenation reaction of hydrogen and chlorinated aromatic hydrocarbon under the action of a catalyst to prepare cyclohexane in one step. CN101037374A discloses a method for gas-phase catalytic hydrogenation and dechlorination of chlorinated aromatic hydrocarbon, which takes a fixed bed as a reactor and is catalyzed by load-type nickel phosphideAnd under the action of the agent, introducing hydrogen and chlorinated aromatic hydrocarbon into the reactor at normal pressure and at the temperature of 200-400 ℃ to perform gas phase reaction, and removing chlorine in the chlorinated aromatic hydrocarbon. CN109485540A discloses a method for producing chlorobenzene and dichlorobenzene by catalytic distillation and degradation of hexachlorobenzene, which comprises the steps of adopting a fixed bed catalytic distillation tower, gradually removing chlorine on hexachlorobenzene in a sectional catalytic hydrogenation mode, enabling hexachlorobenzene and hydrogen to enter from the bottom of the fixed bed catalytic distillation tower, carrying out dechlorination reaction through a catalyst bed layer, enabling low-boiling-point products to gradually move upwards and to be discharged from the top of the tower, and controlling the catalyst and catalytic reaction conditions to control the composition of products at the top of the tower, so that the purity of the obtained dichlorobenzene and chlorobenzene can reach more than 99%. The effect of dechlorination of Hexachlorobenzene (HCB) by a base catalytic decomposition technology (BCD) is researched by adopting base catalytic equipment which is independently designed and developed, and the research shows that the removal rate of hexachlorobenzene is 99.97% and the dechlorination efficiency reaches 91.08% when the adding mass ratio of hexachlorobenzene to sodium hydroxide is 1:5 at 360 ℃. When the reduced iron powder is used as a catalyst, after the reaction is carried out for 1h at 330 ℃, the dechlorination efficiency of hexachlorobenzene can be improved from 38.99% to 77.51% (research on dechlorination effect and influence factors of alkali catalytic decomposition of chlorinated aromatic hydrocarbon [ J]China environmental science 2012 (12)). The methods are all chlorinated aromatic hydrocarbon gas-phase catalytic hydrogenation and dechlorination processes, the reaction temperature is high, the energy consumption is high, hot spots are easy to generate to cause catalyst inactivation, the product components are complex, the separation is difficult, the catalyst stability is poor, and the large-scale industrial production is difficult.

Disclosure of Invention

The invention aims to overcome at least one defect of the prior art and provides a method for selective hydrogenation and dechlorination of hexachlorobenzene, which is used for solving the problems of high reaction temperature and high energy consumption in the process of gas-phase catalytic hydrogenation and dechlorination of chlorinated aromatic hydrocarbon.

The technical scheme adopted by the invention is that,

a method for selective hydrodechlorination of hexachlorobenzene comprises the following steps:

completely dissolving hexachlorobenzene in a solvent at the temperature lower than 80 ℃ to form a normal-temperature saturated hexachlorobenzene solution, and uniformly mixing the normal-temperature saturated hexachlorobenzene solution with hydrogen to obtain a gas-liquid mixture;

loading a hydrogenation reaction catalyst into the first reactor and the second reactor, and activating the catalyst before/after loading into the reactors;

pumping the prepared gas-liquid mixture into a first reactor filled with an activated hydrogenation reaction catalyst in a liquid-phase feeding mode, and reacting to obtain a first reactant mixture;

carrying out gas-liquid separation on the first reactant mixture to obtain a first gas product and a first liquid product;

pumping the first liquid product into a second reactor filled with an activated hydrogenation reaction catalyst for reaction to obtain a second reactant mixture;

carrying out gas-liquid separation on the second reactant mixture to obtain a second gas product and a second liquid product;

and condensing the second liquid product, and separating in a rectifying tower to obtain the solvent, dichlorobenzene, chlorobenzene and polychlorinated benzene.

According to the invention, the two-stage reactor is used for carrying out selective hydrogenation dechlorination on hexachlorobenzene, and the first liquid product obtained after the reaction of the first reactor enters the second reactor for reaction again, so that the yield of dichlorobenzene and chlorobenzene is improved. The technical scheme is different from the traditional gas-phase catalytic hydrodechlorination process, and the hexachlorobenzene does not need to be heated to about 230 ℃ first, and is dissolved by using a solvent at the temperature lower than 80 ℃, so that the temperature is low, and the energy consumption is low. The technical scheme is that in the low-temperature liquid-phase hydrogenation reaction process, the low-temperature solvent can also absorb reaction heat, so that the constant-temperature reaction is more facilitated, and compared with high-temperature gas-phase hydrogenation dechlorination, the low-temperature liquid-phase hydrogenation dechlorination is more conducive to improving the hydrogenation selectivity of hexachlorobenzene, so that severe carcinogen hexachlorobenzene is converted into dichlorobenzene and chlorobenzene which are products with high added values, and the method has the characteristics of good selectivity, high efficiency and strong practicability.

Preferably, the temperature at which the gas-liquid mixture is prepared is in the range of 25 to 80 ℃.

Preferably, the hydrogenation catalyst is supported on a carrier.

Preferably, the active component of the hydrogenation reaction catalyst is one or two of platinum or palladium, or the carrier is any one of alumina, titania or magnesia. In the technical scheme, the catalyst is at least one of platinum and palladium, any one of alumina, titanium dioxide or magnesium oxide is used as a carrier, and the selective hydrogenation and dechlorination reaction efficiency of hexachlorobenzene is high.

Preferably, the mass content of the active component in the hydrogenation reaction catalyst is 0.1-1.0%.

Preferably, the conditions of the activation are: the reducing gas is hydrogen, and the space velocity GHSV is 500-5000 h^-1The pressure is 0.1-3.0 MPa, the temperature is 200-300 ℃, and the activation time is 2-5 h.

Preferably, the inlet temperature of the first reactor is 70-150 ℃, the pressure in the reactor is 0.1-1.0 MPa, and H is₂The molar ratio of the hexachlorobenzene to hexachlorobenzene is 10-20, and the weight space velocity of hexachlorobenzene is 1.0-2.0 h^-1；

Or the inlet temperature of the second reactor is 80-120 ℃, the pressure in the reactor is 0.1-1.0 MPa, and H is₂The mol ratio of the first liquid product to the second liquid product is 1-10, and the weight space velocity of the hexachlorobenzene is 0.5-1.0 h^-1. In the technical scheme, the degree of dechlorination can be adjusted by controlling the catalytic reaction conditions, particularly the reaction temperature, the hydrogen ratio and other factors, so that chlorobenzene and dichlorobenzene can be selectively prepared.

Preferably, the reactor is a fixed bed reactor.

Preferably, the solvent is any one of benzene, toluene, dichloromethane or chloroform. More preferably, the solvent is benzene, and the benzene is a reaction product which is possibly generated in the hydrogenation process of the hexachlorobenzene and needs to be inhibited, so that the benzene can be effectively inhibited from being hydrogenated into the benzene after being added as the solvent, and the benzene in the product can be recycled after being separated.

Preferably, after the first reactant mixture is subjected to gas-liquid separation to obtain a first gas product and a first liquid product, the method further comprises the step of absorbing hydrogen chloride in the first gas product by using a hydrogen chloride absorption solution, and uniformly mixing the normal-temperature saturated solution of hexachlorobenzene and hydrogen by using the residual hydrogen;

or after the second reactant mixture is subjected to gas-liquid separation to obtain a second gas product and a second liquid product, the method also comprises the step of absorbing hydrogen chloride in the second gas product by using a hydrogen chloride absorption solution, and uniformly mixing the normal-temperature saturated solution of hexachlorobenzene and hydrogen with the residual hydrogen. In the technical scheme, the residual hydrogen after the reaction is recycled and mixed with the normal-temperature saturated solution of hexachlorobenzene, so that no hydrogen is discharged, the cost is reduced, and the process safety is improved.

Preferably, the second liquid product is condensed and separated in a rectifying tower to obtain the solvent, dichlorobenzene, chlorobenzene and polychlorinated benzene, and the separated polychlorinated benzene is dissolved by the solvent, mixed with a normal-temperature saturated solution of hexachlorobenzene and sent into the first reactor, and the separated solvent is recycled for dissolving hexachlorobenzene. In the technical scheme, the solvent separated from the rectifying tower is recycled and reused for dissolving hexachlorobenzene, so that the production cost is reduced. Meanwhile, in the technical scheme, after the reaction of the two-stage method, the unreacted polychlorinated benzene is separated from the rectifying tower and enters the first reactor again for hydrodechlorination reaction, so that the yield is improved.

Compared with the prior art, the invention has the beneficial effects that:

(1) according to the invention, the selective hydrogenation dechlorination reaction is carried out on hexachlorobenzene through the two-stage reactor, the first liquid product obtained after the reaction of the first reactor enters the second reactor for reaction again, and the yield of dichlorobenzene and chlorobenzene is improved;

(2) the invention is a low-temperature liquid phase hydrogenation reaction process, and the low-temperature solvent can also absorb reaction heat, so that the constant-temperature reaction is more facilitated, and the severe carcinogen hexachlorobenzene is converted into dichlorobenzene and chlorobenzene which are products with high added values, so that the selectivity is good, the efficiency is high, and the practicability is strong;

(3) the catalyst and the carrier selected by the invention ensure that the selective hydrogenation and dechlorination reaction efficiency of the hexachlorobenzene is high;

(4) the invention can adjust the degree of dechlorination and selectively prepare chlorobenzene and dichlorobenzene by controlling the catalytic reaction conditions, the hydrogen ratio and other factors;

(5) the hydrogen and the solvent can be recycled, so that the cost can be reduced;

(6) the semi-finished polychlorinated benzene can be separated from the rectifying tower and enters the reactor again for hydrodechlorination reaction, so that the yield is improved.

Drawings

FIG. 1 is a schematic diagram of the reaction scheme of the present invention.

The figure includes: 1 part of hydrogen; normal temperature saturated hexachlorobenzene solution 2; a hexachlorobenzene normal-temperature saturated solution feeding pump 3; a liquid flow meter 4; a first gas flow meter 5; a second gas flow meter 6; a first reactor 7; a first gas-liquid separator 8; a liquid feed pump 9; a first reactor 10; a second gas-liquid separator 11; a hydrogen chloride absorption tank 12; the hydrogen gas circulates the compressor 13.

Detailed Description

The drawings are only for purposes of illustration and are not to be construed as limiting the invention. For a better understanding of the following embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

Examples

FIG. 1 shows a schematic diagram of the reaction scheme of the present invention.

A method for selective hydrodechlorination of hexachlorobenzene comprises the following steps:

s1, completely dissolving hexachlorobenzene in a solvent at a temperature lower than 80 ℃ to form a normal-temperature saturated hexachlorobenzene solution 2, and uniformly mixing the normal-temperature saturated hexachlorobenzene solution 2 with a first gas flowmeter 5 through a normal-temperature saturated hexachlorobenzene solution feeding pump 3 and a liquid flowmeter 4 respectively and hydrogen 1 in a specific ratio to obtain a gas-liquid mixture;

s2, loading hydrogenation reaction catalysts into the first reactor 7 and the second reactor 8, and activating the catalysts before/after loading the catalysts into the reactors;

s3, pumping the prepared gas-liquid mixture into a first reactor 7 filled with an activated hydrogenation reaction catalyst in a liquid-phase feeding mode, and reacting to obtain a first reactant mixture;

s4, carrying out gas-liquid separation on the first reactant mixture through a first gas-liquid separator 8 to obtain a first gas product and a first liquid product;

s5, pumping the first liquid product into a second reactor 10 filled with an activated hydrogenation reaction catalyst through a liquid feed pump 9, simultaneously passing hydrogen 1 through a second gas flowmeter 6, uniformly mixing the hydrogen 1 with the first liquid product according to a specific proportion, and reacting in the second reactor 10 to obtain a second reactant mixture;

s6, performing gas-liquid separation on the second reactant mixture through a second gas-liquid separator 11 to obtain a second gas product and a second liquid product;

s7, absorbing hydrogen chloride in the first gas product and the second gas product by using a hydrogen chloride absorption solution in a hydrogen chloride absorption tank 12, and uniformly mixing the normal-temperature saturated solution of hexachlorobenzene and hydrogen by using the residual hydrogen through a hydrogen circulating compressor 13;

s8, condensing the second liquid product, and separating in a rectifying tower to obtain a solvent, dichlorobenzene, chlorobenzene and polychlorinated benzene;

s9, recovering the solvent separated from the rectifying tower for dissolving hexachlorobenzene;

s10, feeding the polychlorinated benzene separated from the rectifying tower into a first reactor.

In this embodiment, the operation sequence of step S1 and step S2 may be switched or synchronized, the operation sequence of step S9 and step S10 may be switched or synchronized, and the combination of steps S8-S9-S10 may be switched or synchronized with the operation sequence of step S7.

According to the invention, the two-stage reactor is used for carrying out selective hydrogenation dechlorination on hexachlorobenzene, and the first liquid product obtained after the reaction of the first reactor enters the second reactor for reaction again, so that the yield of dichlorobenzene and chlorobenzene is improved. Different from the traditional gas-phase catalytic hydrodechlorination process, the hexachlorobenzene does not need to be heated to about 230 ℃ first, and is dissolved by using a solvent at the temperature lower than 80 ℃, so that the temperature is low, and the energy consumption is low. The embodiment is a low temperature liquid phase hydrogenation reaction process, and the low temperature solvent also can absorb the reaction heat, so more be favorable to the constant temperature reaction, and compare with high temperature gaseous phase hydrogenation dechlorination, low temperature liquid phase hydrogenation dechlorination more is favorable to improving the hydrogenation selectivity of hexachlorobenzene to change severe carcinogen hexachlorobenzene into the product dichlorobenzene and chlorobenzene of high added value, the selectivity is good, efficient, the practicality is strong.

In this embodiment, the temperature for preparing the gas-liquid mixture is preferably 25 to 80 ℃. The hydrogenation catalyst is supported on a carrier.

The hydrogenation catalyst comprises one or two of platinum or palladium as active components, and the carrier is any one of alumina, titanium dioxide or magnesium oxide. In this embodiment, the catalyst is at least one of platinum and palladium, and any one of alumina, titania, and magnesia is used as the carrier, so that the efficiency of the selective hydrodechlorination of hexachlorobenzene is high.

The mass content of active components in the hydrogenation reaction catalyst is 0.1-1.0%.

The activation conditions are as follows: the reducing gas is hydrogen, and the space velocity GHSV is 500-5000 h^-1The pressure is 0.1-3.0 MPa, the temperature is 200-300 ℃, and the activation time is 2-5 h.

The inlet temperature of the first reactor is 70-150 ℃, the pressure in the reactor is 0.1-1.0 MPa, and H is₂The molar ratio of the hexachlorobenzene to hexachlorobenzene is 10-20, and the weight space velocity of hexachlorobenzene is 1.0-2.0 h^-1. In the technical scheme, the inlet temperature of the second reactor is 80-120 ℃, the pressure in the reactor is 0.1-1.0 MPa, and H is₂The mol ratio of the first liquid product to the second liquid product is 1-10, and the weight space velocity of the hexachlorobenzene is 0.5-1.0 h^-1. By controlling the catalytic reaction conditions, the hydrogen ratio and other factors, the degree of dechlorination can be adjusted, and chlorobenzene and dichlorobenzene can be selectively prepared.

The reactor is a fixed bed reactor.

The solvent is any one of benzene, toluene, dichloromethane or chloroform. Furthermore, the solvent is benzene, and the benzene is a reaction product which is possibly generated in the hydrogenation process of the hexachlorobenzene and needs to be inhibited, so that the benzene can be effectively inhibited from being hydrogenated into the benzene after being added as the solvent, and the benzene in the product can be recycled after being separated.

In the embodiment, the residual hydrogen after the reaction in the first reactor 7 and the second reactor 10 is recycled and mixed with the normal-temperature saturated solution of hexachlorobenzene, so that no hydrogen is discharged, the cost is reduced, and the process safety is improved. In the embodiment, the solvent separated from the rectifying tower is recycled and reused for dissolving hexachlorobenzene, so that the production cost is reduced. In this embodiment, the incompletely reacted polychlorobenzene is separated from the rectifying tower, dissolved in a solvent, mixed with a normal temperature saturated solution of hexachlorobenzene, and then enters the first reactor again for hydrodechlorination reaction, thereby increasing the yield.

It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the technical solutions of the present invention, and are not intended to limit the specific embodiments of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention claims should be included in the protection scope of the present invention claims.