CN114349589A - Method for preparing p-methyl ethyl benzene by using toluene and ethylene - Google Patents
Method for preparing p-methyl ethyl benzene by using toluene and ethylene Download PDFInfo
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- CN114349589A CN114349589A CN202111641309.5A CN202111641309A CN114349589A CN 114349589 A CN114349589 A CN 114349589A CN 202111641309 A CN202111641309 A CN 202111641309A CN 114349589 A CN114349589 A CN 114349589A
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Abstract
The invention discloses a method for preparing p-methyl-ethyl benzene by utilizing toluene and ethylene, which relates to the technical field of preparation of p-methyl-ethyl benzene and comprises the following steps of obtaining toluene which is in a gaseous state and is in a temperature range of 200-240 ℃, dividing the toluene into two paths, wherein one path is taken as main stream toluene, heating the toluene to 330-370 ℃ through a furnace, the other path is taken as quenching toluene, dividing the quenching toluene into a plurality of sections, additionally obtaining ethylene, and dividing the ethylene into a plurality of sections. The alkylation reaction adopts five-section feeding, and the temperature is increased and then reduced to ensure that the initial temperature and the temperature rise of each section are the same, so that the reaction temperature rise is avoided to be overhigh, the reaction can be carried out more thoroughly, the service life of the catalyst is prolonged, the reaction conversion rate is improved, and the side reaction is reduced.
Description
Technical Field
The invention relates to the technical field of preparation of p-methyl-ethylbenzene, in particular to a method for preparing p-methyl-ethylbenzene by using toluene and ethylene.
Background
Para-methyl ethyl benzene is also called ethyl methyl benzene, is mainly used as a raw material for producing para-methyl styrene, is an important unsaturated monomer, and has attracted extensive attention for important application in the field of resins.
However, as a raw material for producing p-methyl ethylbenzene by p-methyl styrene, the existing production process is difficult to obtain a high-purity p-methyl ethylbenzene raw material, or the catalyst development difficulty is high, or the process is relatively complex, the energy consumption is high, and the investment is large.
Disclosure of Invention
The invention mainly aims to provide a method for preparing p-methyl-ethyl benzene by utilizing toluene and ethylene, which simplifies the process steps for preparing the p-methyl-ethyl benzene, ensures that the purity of the prepared p-methyl-ethyl benzene is higher, and further reduces the preparation cost.
The purpose of the invention can be achieved by adopting the following technical scheme:
a method for preparing p-methyl ethyl benzene by using toluene and ethylene comprises the following steps
Step 1, obtaining gaseous methylbenzene within the temperature range of 200-240 ℃, and dividing the gaseous methylbenzene into two paths, wherein one path is used as main methylbenzene and is heated to 330-370 ℃ through a furnace, the other path is used as quenching methylbenzene and is used as a cooling source, the quenching methylbenzene is divided into multiple sections, ethylene is obtained, and the ethylene is divided into multiple sections;
step 2, mixing mainstream toluene and first-stage ethylene, then feeding the mixed mainstream toluene and first-stage ethylene into a first reactor, controlling the temperature rise to be 20-25 ℃, and then carrying out first-stage reaction in the first reactor, wherein the reaction temperature is 350-395 ℃;
step 3, mixing the first-stage quenched toluene and the second-stage ethylene, allowing the mixture to enter a first reactor, controlling the temperature to be 20-25 ℃, controlling the reaction temperature to be 330-370 ℃, and then performing a second-stage reaction in the first reactor;
step 4, mixing the second-stage quenched toluene and the third-stage ethylene, allowing the mixture to enter a first reactor, controlling the temperature rise to be 20-25 ℃, and then performing a third-stage reaction in the first reactor;
step 5, mixing the third-stage quenched toluene and the fourth-stage ethylene, feeding the mixture into a first reactor, controlling the temperature rise to be 20-25 ℃, and then carrying out a fourth-stage reaction in the first reactor;
step 6, mixing the fourth-stage quenched toluene and the fifth-stage ethylene, feeding the mixture into a first reactor, controlling the temperature rise to be 20-25 ℃, and then carrying out a fifth-stage reaction in the first reactor;
step 7, after the fifth-stage reaction, the reaction gas in the first reactor enters a high-temperature heat exchanger to exchange heat with gaseous toluene, and then enters a reboiler of a toluene recovery tower to serve as a heat source of the toluene recovery tower;
step 8, after the reaction product enters a toluene recovery tower, the toluene recovered from the tower top is circulated back to a toluene evaporator through a circulating pump to participate in the reaction again, and the reaction byproduct non-condensable gas enters a furnace to be burnt as fuel after passing through a toluene tower tail cooler and a water seal tank;
and 9, mixing the materials in the tower kettle of the toluene recovery tower with methyl ethyl benzene, directly feeding the mixed materials into an ethyl-based position transfer reactor for reaction, and rectifying the reaction discharge materials to obtain the p-methyl ethyl benzene with the purity of more than 98%.
Preferably, in the step 8, a 0.32MPa steam boiler is used for gas phase condensation of the toluene recovery tower, and the heat generated by the reaction is converted into self-produced steam which is used as a heat source of other devices.
Preferably, in the step 7, the pressure of an inlet of the reaction gas into the high-temperature heat exchanger is controlled to be 0.4-0.6 MPa, and the pressure difference of the inlet and the outlet of the reaction gas is controlled to be below 0.08 MPa.
Preferably, the condensed water of the toluene evaporator in the step 8 is used as a soft water source for self-producing steam of the toluene recovery tower.
Preferably, a rectifying tower is used for rectifying in the step 9, and light and heavy mixed aromatic hydrocarbons obtained in the rectifying process are collected, wherein the pressure of the rectifying tower is 1-10kpa, and the temperature of the rectifying tower is 70-120 ℃.
Preferably, the mass ratio of the circulating toluene to the ethylene in the step 6 is 24-26, and the reaction space velocity is 0.2-0.7.
Preferably, the amount of the gaseous toluene entering the high-temperature heat exchanger in the step 7 is used for adjusting the heating amount of the toluene recovery tower.
Preferably, in the step 2-6, m-p-mixed methyl ethyl benzene is generated by catalyzing toluene and ethylene by using a selective alkylation catalyst.
The invention has the beneficial technical effects that:
1. the invention adopts toluene circulation reaction to achieve high utilization rate of ethylene, which is close to 100%, and the p-methyl-ethyl benzene produced by two-step reaction and separation has high quality, and the concentration can reach more than 98%.
2. In the reaction process, the step of cooling, cooling and re-reacting is used for four times, so that the catalyst is protected to a certain extent, the reaction is diluted, the partial pressure is reduced, and the reaction conversion rate is improved; the reaction of the invention adopts positive pressure reaction, improves the conversion rate of the reaction, and simultaneously takes the tail gas as fuel to be sent to a heating furnace for combustion, thereby further reducing energy consumption and pollution; the rectification system (light and heavy component removal tower) adopts reduced pressure rectification, thereby reducing the energy consumption and energy quality and reducing the pollution to the environment.
3. The alkylation reaction adopts five-section feeding, and the temperature is increased and then reduced to ensure that the initial temperature and the temperature rise of each section are the same, so that the reaction temperature rise is avoided to be overhigh, the reaction can be carried out more thoroughly, the service life of the catalyst is prolonged, the reaction conversion rate is improved, and the side reaction is reduced.
4. The fractionation waste heat is used as a heat source for the ethyl-position transfer feeding; the process method sends the tail gas of the reaction to a heating furnace for combustion, and can save more than 30% of natural gas.
Drawings
FIG. 1 is a schematic flow diagram of a method according to an embodiment of the invention.
Detailed Description
In order to make the technical solutions of the present invention more clear and definite for those skilled in the art, the present invention is further described in detail below with reference to the examples and the accompanying drawings, but the embodiments of the present invention are not limited thereto.
As shown in FIG. 1, the process for preparing p-methyl-ethyl benzene from toluene and ethylene provided in this example comprises the following steps,
step 1, after being changed into a gas state, raw material methylbenzene enters a high-temperature heat exchanger to exchange heat with a reactor, the temperature is 220 ℃, and then the raw material methylbenzene is divided into two paths, wherein one path is used as main methylbenzene and is heated to 350 ℃ through a heating furnace, the other path is used as quenching methylbenzene and is used as a cooling source, the two paths are divided into a plurality of sections according to the mass ratio of 1:1, ethylene is obtained, the ethylene is divided into a plurality of sections, and the raw material methylbenzene is industrial methylbenzene and industrial ethylene;
step 2, mixing main stream toluene and first section ethylene, then feeding the mixture into a first reactor, controlling the temperature rise to be 20-25 ℃, then carrying out first section reaction in the first reactor, wherein the reaction temperature is 375 ℃, the reaction of the toluene and the ethylene is carried out under the action of a catalyst, and the mixed mixture is fed into the reactor, and the two can be fully contacted with the catalyst at the same time, so that the conversion rate and the selectivity are improved;
step 3, mixing the first-stage quenched toluene and the second-stage ethylene, allowing the mixture to enter a first reactor, controlling the temperature to be 20-25 ℃, controlling the reaction temperature to be 350 ℃, and then performing a second-stage reaction in the first reactor;
step 4, mixing the second-stage quenched toluene and the third-stage ethylene, allowing the mixture to enter a first reactor, controlling the temperature rise to be 20-25 ℃, and then performing a third-stage reaction in the first reactor;
step 5, mixing the third-stage quenched toluene and the fourth-stage ethylene, feeding the mixture into a first reactor, controlling the temperature rise to be 20-25 ℃, and then carrying out a fourth-stage reaction in the first reactor;
step 6, mixing the fourth-stage quenched toluene and the fifth-stage ethylene, allowing the mixture to enter a first reactor, controlling the temperature rise to be 20-25 ℃, and then performing a fifth-stage reaction in the first reactor, wherein the mass ratio of the circulating toluene to the ethylene is 25, and the reaction space velocity is 0.2-0.7;
after the step 7 and the fifth stage of reaction, the reaction gas in the first reactor enters a high-temperature heat exchanger to exchange heat with gaseous toluene, the gaseous toluene is the 'quenching toluene' in the step 1, the heat exchange can reduce the load of a heating furnace, and simultaneously the reaction gas is also used as a heat source of a recovery tower, if the heat exchange is not carried out, the temperature of the reaction gas is too high, the reaction gas enters the recovery tower and is not suitable, the reaction gas is a mixture after the final reaction, mainly comprises methyl ethyl benzene, excessive toluene and a small amount of byproducts,
enters a reboiler of a toluene recovery tower, the heat of the reaction gas after heat exchange is used as a heat source of the toluene recovery tower,
the amount of gaseous toluene entering the high-temperature heat exchanger is used for adjusting the heat of the toluene recovery tower, the inlet pressure of reaction gas entering the high-temperature heat exchanger is controlled to be 0.5MPa, and the inlet-outlet pressure difference of the reaction gas is controlled to be below 0.08 MPa;
step 8, after the reaction product enters a toluene recovery tower, the reaction product is specifically methyl ethyl benzene, excessive toluene and trace byproducts including light aromatic hydrocarbon, heavy aromatic hydrocarbon and organic noncondensable gas, the toluene recovered at the tower top is circulated back to a toluene evaporator through a circulating pump to take part in the reaction again, the noncondensable gas of the reaction byproduct enters a furnace to be burnt as fuel after passing through a toluene tower tail cooler and a water seal tank, and the noncondensable gas of the reaction byproduct mainly refers to a light organic mixture with carbon less than three carbon atoms;
step 9, mixing methyl ethyl benzene with a tower kettle material of a toluene recovery tower, wherein the toluene recovery tower is a separation tower, the boiling point of the mixed methyl ethyl benzene is higher than that of the tower kettle, the mixed methyl ethyl benzene directly enters an ethyl displacement reactor for reaction, the ethyl displacement reactor is a second reactor, the reaction discharge material is rectified to obtain p-methyl ethyl benzene with the purity of more than 98%, and the ethyl displacement reaction adopts the waste heat of the mixed methyl ethyl benzene as a heat source for direct feeding;
in the embodiment, the excessive toluene is separated, recovered and recycled to participate in the reaction, the separated m-p-mixed methyl-ethyl benzene enters a second reactor after heat exchange, most of the m-methyl-ethyl benzene is converted into p-methyl-ethyl benzene under the action of an ethyl-position transfer catalyst, and the p-methyl-ethyl benzene with the content of more than 98 percent is obtained by light-weight removal, heavy-weight removal and rectification.
In the embodiment, in the combined steps of reaction, recovery pre-separation, re-reaction and rectification, high-temperature reaction gas and reaction process water are cleanly recovered.
In this embodiment, as shown in fig. 1, in steps 2 to 6, toluene and ethylene are catalyzed by a selective alkylation catalyst to generate meta-para-methyl-ethyl benzene mixture;
the alkylation reaction adopts high-temperature low-pressure excessive toluene to react with ethylene, ensures that the ethylene completely participates in the reaction, avoids ethylene waste, and is convenient for pressure self-control.
In this embodiment, the toluene and ethylene are discharged through alkylation reaction and subjected to heat exchange, and then enter a toluene reflux cylinder, and then enter a toluene evaporator, and are heated by using 3.8MPa steam, and condensed water enters a condensed water tank.
In this example, the two reactors are fixed beds, and the catalysts used are the novel alkylation catalyst and ethyl transfer catalyst developed by the national institute.
In this example, toluene and ethylene were used to produce m-p-mixed methyl-ethyl benzene over a selective alkylation catalyst (o-methyl-ethyl benzene is very small, and the m-to-p-mixed methyl-ethyl benzene is about 0.6).
In this embodiment, the mixed methylethylbenzene in the bottom of the column enters an ethyl-position transfer reactor, and the reaction liquid enters a light component removal column and then is subjected to light component removal;
the operation parameters of the rectifying tower A are that the pressure is 1-10Kpa, the temperature of a tower kettle is 70-120 ℃, and the temperature of a tower top is 50-70 ℃;
the kettle is discharged and enters a rectification B tower, heavy components are removed from the rectification B tower, the para-methyl ethyl benzene with the product content of more than 98 percent is ejected out, and the operation parameters of the rectification B tower are as follows: the pressure is 1-10Kpa, the temperature of the tower bottom is 70-120 ℃, and the temperature of the tower top is 50-70 ℃.
In this example, in the step 8, a 0.32MPa steam boiler was used for the gas phase condensation in the toluene recovery column, and the heat generated by the reaction was converted into self-produced steam, which was used as a heat source for other devices.
In this example, the condensed water from the toluene evaporator in step 8 was used as the source of soft water for the self-steam production of the toluene recovery column.
In this embodiment, the temperature of the toluene recovery tower can be controlled by the amount of heat exchange between vaporized toluene and the reaction gas, the mainstream toluene enters a heating furnace to be heated and react with vaporized ethylene, the reaction temperature is adjusted to 20-25 ℃ by the amount of ethylene, the reaction temperature is reduced to the initial temperature of the first stage reaction by quenching toluene, the second stage ethylene is added to react to control temperature rise, the temperature rise control of each stage is the same, quenching toluene is not added after the fifth stage reaction, the quenched toluene enters a high-temperature heat exchanger to exchange heat with vaporized toluene, and after the reaction product after heat exchange enters the toluene recovery tower, toluene is ejected out of the toluene recovery tower and then is recycled to the reactor again.
In this embodiment, in step 9, a rectifying tower is used for rectification, and the light and heavy mixed aromatics obtained in the rectification process are collected, and the light and heavy mixed aromatics obtained in the rectification process are sold or used for other purposes, wherein the pressure of the rectifying tower is 1-10kpa, and the temperature of the rectifying tower is 70-120 ℃.
In this example, the amount of gaseous toluene entering the high temperature heat exchanger in step 7 was used to adjust the amount of heat added in the toluene recovery column.
In summary, in this embodiment, the utilization rate of ethylene by the toluene recycling reaction is high, which is close to 100%, and the quality of p-methyl-ethyl benzene produced by two-step reaction and separation is high, and the concentration can reach more than 98%.
The above description is only for the purpose of illustrating the present invention and is not intended to limit the scope of the present invention, and any person skilled in the art can substitute or change the technical solution of the present invention and its conception within the scope of the present invention.
Claims (8)
1. A method for preparing p-methyl ethyl benzene by utilizing toluene and ethylene is characterized by comprising the following steps: comprises the following steps
Step 1, obtaining gaseous methylbenzene within the temperature range of 200-240 ℃, and dividing the gaseous methylbenzene into two paths, wherein one path is used as main methylbenzene and is heated to 330-370 ℃ through a furnace, the other path is used as quenching methylbenzene and is used as a cooling source, the quenching methylbenzene is divided into multiple sections, ethylene is obtained, and the ethylene is divided into multiple sections;
step 2, mixing mainstream toluene and first-stage ethylene, then feeding the mixed mainstream toluene and first-stage ethylene into a first reactor, controlling the temperature rise to be 20-25 ℃, and then carrying out first-stage reaction in the first reactor, wherein the reaction temperature is 350-395 ℃;
step 3, mixing the first-stage quenched toluene and the second-stage ethylene, allowing the mixture to enter a first reactor, controlling the temperature to be 20-25 ℃, controlling the reaction temperature to be 330-370 ℃, and then performing a second-stage reaction in the first reactor;
step 4, mixing the second-stage quenched toluene and the third-stage ethylene, allowing the mixture to enter a first reactor, controlling the temperature rise to be 20-25 ℃, and then performing a third-stage reaction in the first reactor;
step 5, mixing the third-stage quenched toluene and the fourth-stage ethylene, feeding the mixture into a first reactor, controlling the temperature rise to be 20-25 ℃, and then carrying out a fourth-stage reaction in the first reactor;
step 6, mixing the fourth-stage quenched toluene and the fifth-stage ethylene, feeding the mixture into a first reactor, controlling the temperature rise to be 20-25 ℃, and then carrying out a fifth-stage reaction in the first reactor;
step 7, after the fifth-stage reaction, the reaction gas in the first reactor enters a high-temperature heat exchanger to exchange heat with gaseous toluene, and then enters a reboiler of a toluene recovery tower to serve as a heat source of the toluene recovery tower;
step 8, after the reaction product enters a toluene recovery tower, the toluene recovered from the tower top is circulated back to a toluene evaporator through a circulating pump to participate in the reaction again, and the reaction byproduct non-condensable gas enters a furnace to be burnt as fuel after passing through a toluene tower tail cooler and a water seal tank;
and 9, mixing the materials in the tower kettle of the toluene recovery tower with methyl ethyl benzene, directly feeding the mixed materials into an ethyl-based position transfer reactor for reaction, and rectifying the reaction discharge materials to obtain the p-methyl ethyl benzene with the purity of more than 98%.
2. The process of claim 1 for preparing p-methyl-ethylbenzene from toluene and ethylene, wherein: and (3) in the step (8), a 0.32MPa steam boiler is adopted for gas phase condensation of the toluene recovery tower, and heat generated by the reaction is converted into self-produced steam which is used as a heat source of other devices for utilization.
3. The process of claim 1 for preparing p-methyl-ethylbenzene from toluene and ethylene, wherein: and in the step 7, the pressure of the inlet of the reaction gas into the high-temperature heat exchanger is controlled to be 0.4-0.6 MPa, and the pressure difference of the inlet and the outlet of the reaction gas is controlled to be below 0.08 MPa.
4. The process of claim 1 for preparing p-methyl-ethylbenzene from toluene and ethylene, wherein: and (3) the condensed water of the toluene evaporator in the step 8 is used as a soft water source for self-producing steam of the toluene recovery tower.
5. The process of claim 1 for preparing p-methyl-ethylbenzene from toluene and ethylene, wherein: and 9, rectifying by using a rectifying tower, and collecting light and heavy mixed aromatic hydrocarbon obtained in the rectifying process, wherein the pressure of the rectifying tower is 1-10kpa, and the temperature of the rectifying tower is 70-120 ℃.
6. The process of claim 1 for preparing p-methyl-ethylbenzene from toluene and ethylene, wherein: the mass ratio of the circulating toluene to the ethylene in the step 6 is 24-26, and the reaction space velocity is 0.2-0.7.
7. The process of claim 1 for preparing p-methyl-ethylbenzene from toluene and ethylene, wherein: the heating quantity of the toluene recovery tower is adjusted by the quantity of the gaseous toluene entering the high-temperature heat exchanger in the step 7.
8. The process of claim 1 for preparing p-methyl-ethylbenzene from toluene and ethylene, wherein: and 2-6, catalyzing the toluene and the ethylene by adopting a selective alkylation catalyst to generate meta-para mixed methyl ethyl benzene.
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