CN103159703A - Method of continuously producing epichlorohydrin by directly epoxidizing chloropropene - Google Patents

Abstract

The invention discloses a method for continuously producing epichlorohydrin through the direct epoxidation of allyl chloride. The chloropropene, hydrogen peroxide, catalyst slurry, or solvent are transported to the reactor through the metering pump respectively. The reactor is a single reactor or a series of multi-stage reactors, and the reaction pressure is 0.1-1.0MPa. The reaction liquid can be homogeneous phase or heterogeneous state. A filter is installed at the upper end of the discharge port in the reactor to separate the clear liquid containing the product, and the unreacted material containing the catalyst that is not filtered out at the lower end of the filter is transported back to the reactor at the bottom of the reactor by a metering pump. In the continuous production process, there is no need to recover the catalyst, and the gas phase part is condensed and refluxed through the condenser on the top of the reactor. This method has the advantages of stable reaction temperature, simple process flow, no need for catalyst to be reacted after separation and re-pulping configuration, high effective utilization rate of hydrogen peroxide and The high yield of epichlorohydrin can be used in industrial production.

Description

A kind of method for direct epoxidation of propylene chloride to continuously produce epichlorohydrin

technical field

The invention relates to production equipment and a production method of the chemical product epichlorohydrin. Specifically, the present invention uses hydrogen peroxide as an oxidant, and a heteropolyacid salt with reaction-controlled phase transfer characteristics as a catalyst to directly catalyze the epoxidation of chloropropene for continuous preparation of epichlorohydrin.

technical background

Epichlorohydrin (Epichlorohydrin, ECH) is an important basic chemical raw material, mainly used in the production of epoxy resin, epichlorohydrin rubber, glycerin, and surfactants, medicines, pesticides, coatings, ion exchange resins, plasticizers And other products. Industrial production methods mainly include the chlorohydrin method and the allyl alcohol method. The main raw materials of the chlorohydrin method are propylene, chlorine and lime. Chloropropanol is saponified to obtain epichlorohydrin in three steps. Chlorohydrin method process features: it has the characteristics of large-scale production, continuous operation and automation, and has the advantages of mature process and stable operation, but there are low conversion rate, many by-products, high unit consumption, easy corrosion of equipment, and a large amount of Disadvantages such as calcium chloride and organic chlorine wastewater. The main raw materials of the allyl alcohol method are propylene, oxygen and acetic acid. The main reaction process consists of four steps: propylene gas-phase catalyzed oxyacetic acid to produce allyl acetate, hydrolysis to produce allyl alcohol, addition of chlorine to synthesize dichloropropanol, and saponification and dehydrochlorination. . Although the allyl alcohol process has mild reaction conditions, less by-products, and halved the consumption of chlorine and lime raw materials, it has disadvantages such as lengthy process, high equipment investment, and many wastes. In order to effectively solve the problems of serious pollution and easy corrosion of equipment in the production of allyl chloride and allyl alcohol, the development of a clean production process for the preparation of epichlorohydrin by the direct oxidation of allyl chloride came into being. At present, the direct oxidation of chloropropene to prepare epichlorohydrin mainly uses titanium silicon molecular sieve or phosphotungstate as catalyst, and hydrogen peroxide as oxidant to carry out the reaction.

In 1988, Carlo Venturello et al first reported the epoxidation of allyl chloride catalyzed by heteropolyacids. During the reaction, [R ₄ N ⁺ ] ₃ {PO ₄ [WO(O ₂ ) ₂ ] ₄ } ^3- It is a catalytically active species, hydrogen peroxide aqueous solution is an oxidant, and benzene is a solvent. After 2.5 hours of reaction, the yield of epichlorohydrin is 85%. CN1298876 discloses a method for preparing epichlorohydrin by catalytic epoxidation of propene chloride with molecular oxygen. Molecular oxygen is used as an oxidant and a transition metal heteropolyacid salt is used as a catalyst. Compared with the traditional process, the amount of waste water produced is greatly reduced. The catalyst can Recycle. CN1900071 discloses the method that hydrogen peroxide directly oxidizes chloropropene to prepare epichlorohydrin. Although the reaction-controlled phase-transfer catalyst disclosed in the literature has good activity in catalyzing the direct oxidation of chloropropene to epichlorohydrin by hydrogen peroxide, due to the solid-liquid-solid phase transfer characteristics of the catalyst itself during the reaction process , the conventional reaction process is difficult to achieve its large-scale continuous production.

EP065473A1 discloses a trickle bed reactor for the epoxidation of propylene chloride and its production process. The large-particle catalyst is filled in the trickle bed reactor in four sections, and gas pipes and liquid collection plates are arranged between the sections. The first three sections of the layer are the main reaction section, and each section is equipped with a condenser for heat exchange. The reactor has a complex structure, high operating pressure, and relies on large circulation materials to control the temperature. The catalyst particles are too large, which increases the diffusion resistance and reduces the catalyst effective utilization rate.

US4833260 discloses a method for preparing epichlorohydrin by direct epoxidation of allyl chloride, using titanium-silicon molecular sieve as a catalyst, hydrogen peroxide as an oxidant, and direct catalytic oxidation of allyl chloride to selectively produce epichlorohydrin. The problem of environmental pollution caused by a large amount of waste water in the traditional process, but because the catalyst titanium-silicon molecular sieve needs to have high catalytic activity in polar solvents such as alcohols, the introduction of a large amount of polar solvents leads to partial hydrolysis of epichlorohydrin and ring-opening to form ether Class products, the product selectivity is low. Patents such as US4824976, US5675026, CN1319099, and CN1219536A disclose that the catalyst is improved by adding basic organic or nonpolar compounds, thereby improving the selectivity of epichlorohydrin.

CN1769277A discloses a production process of epichlorohydrin. After the liquid-phase chloropropene and titanium-silicon molecular sieve catalyst are prepared, they are added to the spiral channel type rotating bed or rotating packed bed supergravity reactor, and the liquid-phase or gas-phase chloropropene is continuously added at the same time. And hydrogen peroxide, allyl chloride and hydrogen peroxide directly carry out epoxidation reaction under the action of catalyst. Unreacted chloropropene and a small amount of produced gas are condensed and returned to the batching tank for continued use. The slurry in the reactor flows into the batching tank, and part of the material is circulated into the reactor after being pressurized. Part of the material is sent to the separator, and the separated epichlorohydrin is produced Sent to refining, the slurry containing the catalyst is returned to the batching tank for continued use. Since the method does not use a solvent, the dispersion of the catalyst is poor in the reaction process, and the activity and life of the catalyst will be adversely affected. In addition, the catalyst is separated by a hydrocyclone separation technology, and the operation process is cumbersome and complicated, which is not conducive to industrial production.

CN101172970A discloses a method for producing epichlorohydrin, using titanium silicon molecular sieve as a catalyst, hydrogen peroxide as an oxidant, acetonitrile as a solvent, and a fixed bed as a reactor to catalyze the oxidation of chloropropene to produce epichlorohydrin. But must make reaction liquid be homogeneous, therefore need to use a large amount of solvents to increase separation energy consumption, in addition the catalyzer reaction process in the fixed-bed reactor is easy to clog, easily causes yield low, and exothermic concentration is concentrated in catalyst during the reaction process. On the bed, it is easy to lead to the increase of by-products and the decrease of selectivity in the production process.

CN1275952C discloses a kind of production method of epichlorohydrin, allyl chloride, hydrogen peroxide, solvent and titanium-silicon molecular sieve catalyst fine particles are put into reaction still, and solvent and unreacted allyl chloride directly return to reaction still through fractional distillation reflux, After the slurry in the reaction kettle is filtered, the obtained clear liquid is separated to obtain epichlorohydrin products, and the obtained catalyst concentrated slurry is returned to the reaction still, and the solvent and allyl chloride separated from the clear liquid are also returned to the reaction still for continued use. The disadvantage of this method is that the exothermic reaction easily leads to difficult control of the reaction temperature, and the process of reconfiguring the slurry of the catalyst is complicated.

CN101481364B discloses a continuous production method for preparing epichlorohydrin by the hydrogen peroxide method, which is characterized in that the reactor is a single kettle, or a series of slurry bed reactors with the same or different volumes in multiple stages; the reaction solution does not need to be homogeneous The slurry particles of allyl chloride, solvent and titanium-silicon molecular sieve catalyst are added into the first reaction kettle with a metering pump, and hydrogen peroxide is added dropwise in the first reaction kettle or each level of reaction kettle, and the reaction is carried out under weakly acidic conditions. After that, the material is separated into oil and water through the intermediate storage tank, and is divided into oil phase and water phase slurry; the catalyst is suspended in the water phase, and the oil phase is sent to the rectification tower to separate allyl chloride, epichlorohydrin and trace methanol; the water phase slurry is passed through After filtration, the catalyst filter cake or concentrated slurry is directly beaten with a solvent and then pumped into the first-stage epoxidation reaction kettle. After filtration, the water phase contains methanol, a small amount of epichlorohydrin, water produced by reaction and water brought in by hydrogen peroxide. , a small amount of methanol and epichlorohydrin are separated by negative pressure rectification, and the recovered methanol is used for the configuration of catalyst slurry. The disadvantage of this method is that the operation process in the process of filtering the catalyst and reconfiguring the slurry is complicated, and the catalyst is easy to be lost.

Contents of the invention

The purpose of the present invention is to solve the problems of difficult separation and recovery of catalysts and unstable operation in the prior art for the production of epichlorohydrin by direct epoxidation of chloropropene under reaction control and phase transfer catalysis, and to provide a new direct epoxidation of chloropropene A continuous production method for preparing epichlorohydrin, the method has the advantages of stable reaction temperature, simple process flow, no need for catalyst reaction, separation and re-beating configuration.

In order to solve the above-mentioned technical problems, the present invention adopts following technical scheme to realize:

A method for direct epoxidation of allyl chloride to continuously produce epichlorohydrin, which uses a reactor to react, and the reaction raw materials, allyl chloride, hydrogen peroxide aqueous solution, catalyst slurry, or solvent, are respectively passed through the lower part of the reactor through a metering pump. The feed port is transported to the reactor. The reactor is a single reactor or a series of multi-stage reactors. The reactor is a multi-stage stirred tank reactor with a stirring level of 8-10; the reaction temperature is 25-95 °C, and the reaction pressure is 0.1-1.0MPa, the reaction liquid can be in a homogeneous or heterogeneous state; there is a clear liquid outlet with a built-in filter on the upper part of the reactor, which can separate the clear liquid containing the product and place it under the clear liquid outlet 1. There is a slurry return outlet on the side wall of the upper part of the reactor, and the unfiltered unreacted materials containing catalyst are transported back to the reactor through the slurry pump at the bottom of the reactor through the slurry return inlet, which is not required in the continuous production process. The catalyst is recovered, and the catalyst does not need to be separated, filtered and re-beaten. This kind of catalyst circulation in the body simplifies the process flow, reduces the production cost, and improves the work efficiency; the gas phase part is condensed and refluxed through the condenser on the top of the reactor.

The reactor can be a single reactor, or a multi-stage reactor connected in series through a pipeline, and the volume of the multi-stage reactor can be different or the same;

Single reactor structure: The upper side wall of the reactor is provided with a clear liquid outlet with a built-in filter, and a slurry return outlet is provided below the clear liquid outlet and on the middle and upper side wall of the reactor. The lower side of the reactor The wall is provided with a feed inlet and a slurry return inlet, and the slurry return outlet and the slurry return inlet are connected by pipes, and a slurry pump is arranged on their connecting pipes; a reflux condenser is provided at the top of the reactor;

The multi-stage reactor is composed of more than two pipeline reactors in series, and the structure is: the top of each reactor in the multi-stage reactor is equipped with a reflux condenser;

A feed inlet and a slurry return inlet are provided on the lower side wall of the first-stage reactor; an overflow port is provided on the upper side wall of the first-stage reactor; on the upper side wall of the last-stage reactor A clear liquid discharge port with a built-in filter is provided, and a slurry return outlet is provided below the clear liquid discharge port and on the upper side wall of the reactor. A slurry pump is installed on the pipeline;

An overflow port is provided on the upper side wall of each reactor before the last reactor, and an overflow is provided on the lower side wall of each reactor from the second to the last reactor. The material inlet, the overflow port of the adjacent secondary reactor and the overflow material inlet are connected by pipes, and the material flows out from the overflow port of the upper-stage reactor through the pipeline and flows into the next stage through the overflow material inlet of the next-stage reactor. inside the reactor.

When a single reactor is used for direct epoxidation of propylene chloride to produce epichlorohydrin, after the reaction materials are added into the reactor through a metering pump, the clear liquid containing the product and the unreacted material containing the catalyst are filtered out through the built-in filter at the upper end of the reactor. It can be refluxed to the reactor through the metering pump. In the continuous production process, there is no need to recover the catalyst. The gas phase is condensed and refluxed through the condenser on the top of the reactor. The direct epoxidation of chloropropene to produce epichlorohydrin uses a series of multi-stage reactors. At this time, the reaction material overflows from the upper end of the first-stage reactor to the lower end of the second-stage reactor, and the built-in filter at the upper end of the second-stage reactor filters out the clear liquid containing the product, and the unreacted material containing the catalyst can be refluxed through the metering pump into the first stage reactor.

The reaction process is an exothermic reaction. A jacketed heat exchange layer is provided outside the condenser and the reaction to carry away the heat generated by the reaction. The gas phase part is condensed and refluxed through the condenser on the top of the reactor.

The process flow provided by the invention is suitable for the phosphotungstic heteropolysalt catalyst with the characteristic of reaction-controlled phase transfer.

The ratio of the amount of heteropolyacid to hydrogen peroxide used as catalyst is 5-50g/1mol; the molar ratio of chloropropene and hydrogen peroxide is 1-1000:1;

The filter needs to be installed at the upper end of the reactor. The filter can be any one of ceramic membrane filter and sintered metal filter; the pore size of the filter depends on the particle size of the applicable catalyst. Generally, the pore size of the filter It should be 1-5μm larger than the particle size of the catalyst, and the product discharge method adopts the internal pressure of the reaction higher than the external pressure so that the clear liquid flows out from the filter, and the product analysis and separation of the outflow clear liquid can obtain the selectivity of epichlorohydrin And data such as the conversion rate of hydrogen peroxide.

The method has the characteristics of stable reaction temperature, simple process flow, separation and re-beating configuration of the catalyst after no reaction, high effective utilization rate of hydrogen peroxide and high yield of epichlorohydrin. Can be used in industrial production.

Description of drawings

Figure 1 is a schematic diagram of a single reactor process flow diagram for the direct epoxidation of propylene chloride to produce epichlorohydrin.

Fig. 2 is a schematic flow diagram of two reactors connected in series to produce epichlorohydrin by direct epoxidation of propylene chloride.

Among them, 1 is a chloropropene metering pump, 2 is a hydrogen peroxide metering pump, 3 is a catalyst slurry metering pump, 4 is a circulating slurry metering pump, 5 is a reactor, 6 is a filter, 7 is a condenser, and 8 is a solvent Metering pumps.

The present invention will be further described below through specific examples, but the scope of the present invention is not limited to the given examples.

Detailed ways

【Example 1】

By two reactor series epichlorohydrin production techniques shown in Fig. 2;

The secondary reactor is composed of two reactors connected in series, and the structure is as follows: a reflux condenser is provided at the top of each reactor in the secondary reactor;

A feed inlet and a slurry return inlet are provided on the lower side wall of the first-stage reactor; an overflow port is provided on the upper side wall of the first-stage reactor; on the upper side wall of the last-stage reactor A clear liquid discharge port with a built-in filter is provided, and a slurry return outlet is provided below the clear liquid discharge port and on the upper side wall of the reactor. A slurry pump is installed on the pipeline;

An overflow port is provided on the upper side wall of the first-stage reactor, and an overflow material inlet is provided on the lower side wall of the last-stage reactor. The overflow port and the overflow material inlet of the second-stage reactor Through pipeline connection, the material flows out from the overflow port of the first-stage reactor and flows into the second-stage reactor through the overflow material inlet of the second-stage reactor through the pipeline.

Each reactor has a volume of 30L, and the total volume is 60L. Add 2.5kg of phosphotungstic heteropoly salt catalyst and 40L of chloropropene into the reactor in advance through a metering pump. When the reaction temperature reaches 45°C, the reaction pressure is 0.8MPa. , start continuous production, allyl chloride and hydrogen peroxide are delivered to the first-stage reactor by metering pumps, the feed flow rate of allyl chloride is 10L/h, the feed flow rate of 50% hydrogen peroxide is 2L/h, and the stirring speed is 300r/min.

The reaction material overflows from the upper end of the first-stage reactor to the lower end of the second-stage reactor. The built-in filter at the upper end of the second-stage reactor filters out the clear liquid containing the product, and the unreacted material containing the catalyst can be returned to the second-stage reactor through the metering pump. In the primary reactor, there is no need to recover the catalyst during the continuous production process, and the gas phase is condensed and refluxed through the condenser on the top of the reactor. The reaction process is an exothermic reaction, and the condenser 7 and the outside of the reaction are equipped with a jacketed heat exchange layer, which can carry out heat exchange and carry away the heat generated by the reaction.

The separated clear liquid is analyzed to obtain the yield of epichlorohydrin, the selectivity of epichlorohydrin, and the conversion rate of hydrogen peroxide.

[Example 2]

By the single reactor epichlorohydrin production process shown in Fig. 1;

Single reactor structure: The upper side wall of the reactor is provided with a clear liquid outlet with a built-in filter, and a slurry return outlet is provided below the clear liquid outlet and on the middle and upper side wall of the reactor. The lower side of the reactor The wall is provided with a feed inlet and a slurry return inlet, and the slurry return outlet and the slurry return inlet are connected by pipes, and a slurry pump is arranged on their connecting pipes; a reflux condenser is provided at the top of the reactor;

The volume of the reactor is 45L, and the total volume is 45L. Add 2.5kg of phosphotungstic heteropoly salt catalyst and 35L of chloropropene into the reactor through a metering pump in advance. When the reaction temperature is 50°C and the reaction pressure is 0.1MPa, start For continuous production, allyl chloride and hydrogen peroxide are transported to the first-stage reactor through metering pumps, the feed flow rate of allyl chloride is 8L/h, the feed flow rate of 50% hydrogen peroxide is 2L/h, and the stirring speed is 150r/min.

After the reaction materials are fed into the reactor through the metering pump, the clear liquid containing the product is filtered through the built-in filter at the upper end of the reactor, and the unreacted materials containing the catalyst can be returned to the reactor through the metering pump, which is not required in the continuous production process. The catalyst is recovered, and the gas phase is condensed and refluxed through the condenser on the top of the reactor. The reaction process is an exothermic reaction. The condenser 7 and the outside of the reaction are equipped with a jacketed heat exchange layer to carry away the heat generated by the reaction.

The separated clear liquid is analyzed to obtain the yield of epichlorohydrin, the selectivity of epichlorohydrin, and the conversion rate of hydrogen peroxide.

Claims (9)

1. A method for direct epoxidation of allyl chloride to continuously produce epichlorohydrin, adopting reactor (5) to react, and reacting allyl chloride, aqueous hydrogen peroxide solution, catalyst slurry, or solvent through metering pump respectively Transported in the reactor (5) through the feed inlet of the lower part of the reactor (5), the reactor (5) is a single reactor or a series of multi-stage reactors, the reaction temperature is 25-95 ° C, the reaction pressure is 0.1-1.0MPa, The reaction liquid can be in a homogeneous or heterogeneous state; a clear liquid discharge port with a built-in filter (6) is provided on the upper part of the reactor (5), and the clear liquid containing the product can be separated, and the clear liquid discharge port A slurry reflux outlet is provided on the side wall of the lower part and the upper part of the reactor (5), and the unfiltered unreacted material containing catalyst is refluxed at the bottom end of the reactor (5) through the slurry reflux inlet through the circulating slurry metering pump (4). Transported to the reactor (5), no need to recover the catalyst in the continuous production process, the gas phase part is condensed and refluxed through the condenser (7) at the top of the reactor. 2. The method according to claim 1, characterized in that: said reactor (5) can be a single reactor, or multistage reactors connected in series through pipelines, and the volumes of multistage reactors can be different or the same; Single reactor structure: the upper side wall of the reactor (5) is provided with a clear liquid outlet with a built-in filter (6), and below the clear liquid outlet, on the upper side wall of the reactor (5) is provided with The slurry reflux outlet, the lower side wall of the reactor (5) is provided with a feed inlet and a slurry reflux inlet, the slurry reflux outlet and the slurry reflux inlet are connected by a pipeline, and a circulating slurry metering pump ( 4); The top of the reactor (5) is provided with a reflux condenser (7); The multi-stage reactor is composed of more than two reactors connected in series, and the structure is: a reflux condenser (7) is provided at the top of each reactor (5) in the multi-stage reactor; A feed inlet and a slurry return inlet are provided on the lower side wall of the first-stage reactor; an overflow port is provided on the upper side wall of the first-stage reactor; on the upper side wall of the last-stage reactor A clear liquid discharge port containing a built-in filter (6) is provided, and a slurry return outlet is arranged below the clear liquid discharge port and on the upper side wall of the reactor. The slurry return flow outlet and the slurry return flow inlet are connected by a pipeline, and A circulating slurry metering pump is arranged on their connecting pipes; An overflow port is provided on the upper side wall of each reactor before the last reactor, and an overflow is provided on the lower side wall of each reactor from the second to the last reactor. The material inlet, the overflow port of the adjacent secondary reactor and the overflow material inlet are connected by pipes, and the material flows out from the overflow port of the upper-stage reactor through the pipeline and flows into the next stage through the overflow material inlet of the next-stage reactor. inside the reactor. 3. The method according to claim 1 or 2, characterized in that: the reactor (5) is a multi-stage stirred tank reactor with a stirring level of 8-10. 4. method according to claim 1, it is characterized in that: described reaction catalyst is the phosphotungstic heteropoly salt with reaction control phase transfer characteristic; Reaction catalyst selects its consumption of phosphotungstic heteropoly salt and hydrogen peroxide The ratio is 5-50g/1mol; the molar ratio of allyl chloride to hydrogen peroxide is 1-1000:1. 5. The method according to claim 1, characterized in that: the reaction temperature is 25-55° C., the pressure is 0.1-1.0 MPa, an inert gas is selected as the protective gas and the reaction pressure is maintained. 6. The method according to claim 1, characterized in that: the built-in filter is a ceramic membrane filter or a sintered metal filter core, and the aperture of the filter is 1-5 μm smaller than the particle diameter of the catalyst; The connection between the built-in filter and the supernatant outlet on the side wall of the reactor is a detachable pipeline connection. 7. The method according to claim 6, characterized in that: the porosity of the sintered metal filter element installed in the reactor is required to be between 0.1-100 μm, and the quantity is required to be between 2-32, and the sintered metal filter element The shape of the core is hollow cylinder, and the required ratio range of the diameter of the sintered metal filter core to the inner diameter of the reactor is 1:4-12. 8. The method according to claim 1, characterized in that: the concentration of allyl chloride is required to be more than 95%, the concentration range of aqueous hydrogen peroxide solution is between 27%-75%, and the solvent consumption is the mass consumption of allyl chloride Between 0-8 times. 9. according to the described method of claim 1 or 2, it is characterized in that: reaction is exothermic reaction, is provided with jacket heat exchange layer outside reactor, condenser (7) and the jacket that reactor outside is provided with The heat exchange layer can conduct heat exchange and carry away the heat generated by the reaction.

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