CN113045374A - Reaction device and reaction method for producing p-xylene through alkylation of toluene and methanol - Google Patents
Reaction device and reaction method for producing p-xylene through alkylation of toluene and methanol Download PDFInfo
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- C07C2/86—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon
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- C07C2/864—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon the non-hydrocarbon contains only oxygen as hetero-atoms the non-hydrocarbon is an alcohol
Abstract
The invention provides a reaction device and a reaction method for producing p-xylene by alkylation of toluene and methanol, wherein the reaction device comprises a fixed bed reactor provided with at least 3 reaction sections; the reaction method comprises the following steps: mixing toluene and partial methanol, and then carrying out first-stage gas-phase feeding from the top end of the fixed bed reactor, and simultaneously carrying out at least 2-stage gas-phase feeding on the residual methanol from the side wall of the fixed bed reactor, wherein the feeding amount of the methanol at the first stage is gradually reduced along with the reaction time, but the total feeding amount of the methanol is ensured to be unchanged; obtaining p-xylene after reaction; the reaction method improves the conversion rate of toluene and the selectivity of xylene by methanol sectional gas phase feeding, adjusting the feeding amount along with the reaction time and introducing cooling substances in sections, and has good industrial application prospect.
Description
Technical Field
The invention belongs to the technical field of aromatic hydrocarbon synthesis, and particularly relates to a reaction device and a reaction method for producing p-xylene through toluene and methanol alkylation.
Background
Para-xylene (PX) is mainly used for producing Purified Terephthalic Acid (PTA), which is a main raw material for synthesizing polyester fibers and plastics. Besides being used as an important petrochemical basic raw material, the p-xylene also has extremely wide application in the fields of medicines, pesticides, dyes, solvents and the like. The domestic and foreign para-xylene production process mainly comprises a toluene disproportionation and C9 hydrocarbon transalkylation process, a xylene isomerization process, a toluene selective disproportionation process and a toluene methanol alkylation process. Under the influence of thermodynamic equilibrium, the target products of the first two processes have low content of p-xylene in xylene isomers, and the products are not easy to separate; the concentration of the p-xylene in the toluene selective disproportionation product is higher, but the byproduct of the toluene is higher in content, and the utilization rate of the toluene is lower.
Compared with the traditional PX production process, the toluene utilization rate of the route is high, the toluene raw material can be converted into a xylene product to the maximum extent, and compared with the traditional toluene disproportionation technology for increasing the yield of xylene by using toluene, the toluene methanol shape-selective alkylation technology has the characteristic of high benzene ring utilization rate; the methanol is used as the alkylation production raw material, has cost advantage and is a technology for high-value utilization of the methanol. Therefore, the technology for preparing p-xylene by selective alkylation of methanol and toluene is bound to attract more extensive attention as a new key technology for converting aromatic hydrocarbon in the future.
The toluene methanol alkylation reactor is divided into a fixed bed, a fluidized bed and a moving bed reactor, wherein the PX prepared by toluene methanol alkylation belongs to a gas-solid phase reaction process, and the regeneration period of the catalyst and related indexes can be integrated to select the reactor. The regeneration period of the catalyst is more than half a year, and a fixed bed reactor can be selected preferentially; when the regeneration period is short, a fluidized bed reactor is suitable for being adopted; if the regeneration period is hundreds of hours, and a moving bed reactor is selected, the advantages of the fixed bed reactor and the fluidized bed reactor can be obtained.
CN102746099A discloses a method for preparing xylene by alkylating benzene, toluene and methanol, which comprises the following process steps: (1) mixing raw material benzene and methylbenzene, circulating benzene and methylbenzene recovered by rectification and methanol together, performing heat exchange on the mixed material and an alkylation reactor outlet material, heating to reach an alkylation reaction temperature, then feeding the mixture into an alkylation reactor, and performing alkylation reaction in the presence of a catalyst to obtain a product; (2) the resultant enters a benzene removing tower for rectification and separation, the mixture of benzene, toluene and water at the tower top is cooled and then subjected to oil-water separation, the oil phase returns to an alkylation reactor for circular reaction, and the water phase is treated and recycled; the method adopts an alkylation reactor which is a reactor consisting of two reaction sections and is a liquid phase one strand of feed, has low conversion rate of methanol and toluene, and has the problems of uneven gasification distribution and local carbonization of the liquid phase methanol feed.
CN102464559A discloses a method for producing alkylated aromatic hydrocarbon, which adopts alkylation reagent multi-stage feeding, takes aromatic hydrocarbon material and alkylation reagent as raw materials, and the total molar ratio of the aromatic hydrocarbon material to the alkylation reagent is1: 10-10: 1, weight space velocity of 1-10 hr-1Carrying out alkylation reaction on the raw materials on an equilibrium type catalyst under the conditions that the reaction temperature is 300-500 ℃, the reaction pressure is 0.1-5.0 MPa and the molar ratio of the carrier gas to the raw materials is 0-8; although the method uses a multi-bed reactor and carries out multi-stage feeding on the alkylating reagent, the upper layer and the lower layer of the catalyst bed are provided with inert layers made of inert ceramic balls or glass beads, so that the production cost is increased, and the liquid-phase feeding of the alkylating reagent is easy to generate local carbonization.
In summary, how to provide a method for producing paraxylene by toluene alkylation with methanol, which can improve the overall conversion rate of methanol and prolong the refining and online regeneration periods, is a problem to be solved at present.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a reaction device for producing p-xylene by alkylating toluene with methanol and a reaction method thereof, wherein the reaction device improves the utilization efficiency of a catalyst in a reactor by arranging a multi-section fixed bed reactor; according to the reaction method, methanol is fed in a segmented gas phase manner, and the feeding amount is adjusted, so that the toluene conversion rate is improved, the safety performance of the device is improved, and the method has a good industrial application prospect.
In order to achieve the purpose, the invention adopts the following technical scheme:
in one aspect, the invention provides a reaction device for producing paraxylene by alkylation of toluene with methanol, which comprises a fixed bed reactor, wherein the fixed bed reactor comprises at least 3 reaction sections;
the fixed bed reactor is provided with a top feeding hole and side wall feeding holes, and two groups of side wall feeding holes are arranged between two adjacent reaction sections in the fixed bed reactor; except the first reaction section, each reaction section is provided with a temperature controller.
According to the invention, the reaction device improves the utilization efficiency of the catalyst in the reactor through the design of a plurality of reaction sections, further improves the toluene conversion rate, improves the yield of p-xylene, and has a good industrial application prospect.
In the invention, the top end of the fixed reactor is taken as a first reaction section, and the rest reaction sections are arranged from top to bottom in sequence.
In the invention, a plurality of sets of fixed bed reactors can also be connected in series, and each set of reactor is a section.
The following technical solutions are preferred technical solutions of the present invention, but not limited to the technical solutions provided by the present invention, and technical objects and advantageous effects of the present invention can be better achieved and achieved by the following technical solutions.
As a preferred technical scheme of the invention, each reaction section of the fixed bed reactor is filled with a catalyst.
As a preferable technical scheme of the invention, the side wall feed inlets comprise a methanol feed inlet and a cooling substance feed inlet.
Preferably, the methanol feed inlet is at least 2, such as 2, 3, 4, 5, 6 or 7, etc., but is not limited to the recited values, and other values not recited within this range are equally applicable.
Preferably, the cooling material feed openings are at least 2, such as 2, 3, 4, 5, 6 or 7, etc., but are not limited to the recited values, and other values not recited within this range are equally applicable.
Preferably, the feed pipelines connected with the cooling material feed inlets are respectively and independently provided with control valves.
Preferably, each of said temperature controllers controls the opening of a control valve on its corresponding cooling substance feed line.
As the preferable technical scheme of the invention, the reaction device also comprises a heat exchange unit, a toluene separation unit and a xylene separation unit; a cold fluid outlet of the heat exchange unit is connected with the top end of the fixed bed reactor; and the bottom outlet of the fixed bed reactor is connected with the hot fluid inlet of the heat exchange unit, the hot fluid outlet of the heat exchange unit is connected with the inlet of the toluene separation unit, and the outlet of the toluene separation unit is connected with the inlet of the xylene separation unit.
In another aspect, the present invention provides a reaction method for producing paraxylene using the above reaction apparatus, the reaction method comprising the steps of:
mixing toluene, partial methanol and steam, and then carrying out first-stage gas-phase feeding from the top end of the fixed bed reactor, and simultaneously carrying out at least 2-stage gas-phase feeding on the residual methanol from the side wall of the fixed bed reactor, wherein the feeding amount of the methanol at the first stage is gradually reduced along with the reaction time, but the total feeding amount of the methanol is ensured to be unchanged; obtaining the p-xylene after reaction.
According to the invention, the reaction method adopts methanol multi-section gas phase feeding, so that the problems of uneven gasification distribution and local carbonization during liquid phase methanol feeding are avoided; and a reaction time program is established according to the properties of the catalyst, the methanol feeding amount of each section is gradually adjusted according to the reaction duration, the activity of the catalyst is fully utilized, the utilization efficiency of the catalyst is improved, the regeneration period of the catalyst is reduced, the manpower and the operation cost are reduced, the large-scale production is facilitated, and the method has a good industrial application prospect.
In the present invention, the total reaction section of the reaction process is the first section plus the number of methanol feed sections on the side wall.
In a preferred embodiment of the present invention, the residual methanol is fed from the sidewall of the fixed bed reactor in a gas phase in not more than 6 stages, for example, 2, 3, 4, 5 or 6 stages, but the residual methanol is not limited to the values listed, and other values not listed in the range of the values are also applicable.
In a preferred embodiment of the present invention, the molar ratio of toluene, methanol and steam in the first-stage gas-phase feed is 1 (0.7 to 0.98): (0.55 to 1.1), for example, 1:0.7:0.55, 1:0.75:0.6, 1:0.8:0.8, 1:0.85:0.9, 1:0.9:1 or 1:0.98:1.1, but not limited to the above-mentioned values, and other values not listed in the above-mentioned values are also applicable.
Preferably, the temperature of the first stage gas phase feed is in the range of 450 to 500 ℃, such as 450 ℃, 460 ℃, 470 ℃, 480 ℃, 490 ℃ or 500 ℃ and the like, but is not limited to the recited values, and other values not recited in this range of values are equally applicable.
Preferably, the amount of methanol fed to the first stage gas phase feed is 18 to 42% of the total methanol feed, for example 18%, 20%, 25%, 30%, 35%, 40% or 42%, but not limited to the recited values, and other values not recited within the range of values are equally applicable.
In the present invention, the ratio of the first stage methanol feed to the total methanol feed is controlled. If the proportion is too large, the selectivity of p-xylene is low, more tail gas is generated, and the deactivation of the first-stage catalyst is accelerated; if the ratio is too small, the conversion of toluene is lowered and the yield of p-xylene is reduced.
Preferably, the amount of methanol fed to each stage, other than the first stage, is from 2 to 35%, such as 2%, 5%, 10%, 15%, 20%, 25%, 30% or 35%, etc., of the total amount of methanol fed, but not limited to the recited values, and other values not recited within the range of values are equally applicable.
In the present invention, the ratio of the methanol feed amount of each stage to the total methanol feed amount is controlled. If the proportion is too high, the selectivity of the p-xylene is low, more tail gas is generated, and the deactivation of the catalyst is accelerated; if the ratio is too low, the toluene conversion is lowered and the yield of p-xylene is impaired.
In a preferred embodiment of the present invention, the reaction temperature is 450 to 500 ℃, for example, 450 ℃, 460 ℃, 470 ℃, 480 ℃, 490 ℃ or 500 ℃, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.
According to the invention, the temperature of each section of catalyst bed layer is ensured to be maintained at 450-500 ℃ by adjusting the amount of hydrogen, and compared with the method of controlling the temperature by adopting liquid-phase methanol feeding, the method can avoid the phenomenon of non-uniform liquid-phase distribution, reduce the carbon deposition of methanol and reduce the blocking phenomenon.
Preferably, the reaction pressure is 0.2 to 0.5MpaG, such as 0.2MpaG, 0.3MpaG, 0.4MpaG or 0.5MpaG, but not limited to the recited values, and other values not recited within the range are equally applicable.
In the present invention, the pressure of the reaction is controlled. If the pressure is too high, the isomerization reaction and the deep alkylation reaction of the paraxylene can be promoted, so that the selectivity of the paraxylene is reduced, and the carbon deposition rate is increased; if the pressure is too low, the amount of the catalyst used and the equipment specifications are increased, and the investment is increased.
Preferably, the catalyst used for the reaction comprises a shape selective catalyst comprising platinum metal.
In the invention, the shape-selective catalyst is mainly obtained by modifying Mg, P and Si.
As a preferable technical scheme of the invention, a cooling substance is introduced in the reaction process to control the reaction temperature.
Preferably, the cooling material is at least 2 stages of feed, such as 2, 3, 4, 5, or 6 stages, and the like, but is not limited to the recited values, and other values not recited within the range of values are equally applicable.
Preferably, the cooling substance comprises a cooling gas.
Preferably, the cooling gas comprises hydrogen.
Preferably, the hydrogen is recycled.
Preferably, the reaction is followed by isolation.
Preferably, the tail gas obtained in the separation process is used as a circulating gas to return to the top end of the fixed bed reactor for the first-stage gas-phase feeding.
Preferably, the hydrogen molar content of the recycle gas is greater than 65%, for example 65.5%, 66%, 67%, 68%, 69%, or 70%, etc., but is not limited to the recited values, and other values not recited within this range are equally applicable.
As a preferred technical scheme of the invention, the reaction method comprises the following steps:
mixing toluene, methanol and water vapor in a molar ratio of 1 (0.7-0.98) (0.55-1.1), and then carrying out first-stage gas-phase feeding from the top end of the fixed bed reactor, and simultaneously carrying out at least 2-stage gas-phase feeding on the residual methanol from the side wall of the fixed bed reactor, wherein the feeding amount of the methanol in the first stage is gradually reduced along with the reaction time, but the total feeding amount of the methanol is ensured to be unchanged; products obtained after reaction sequentially enter a heat exchange unit, a toluene separation unit and a xylene separation unit for heat exchange and separation to obtain p-xylene, tail gas obtained by each unit in the reaction process is used as circulating gas to return to the top end of the fixed bed reactor for first-stage gas phase feeding, and the molar content of hydrogen in the circulating gas is more than 65%; and introducing at least 2 sections of feeding cooling substances in the reaction process to control the reaction temperature of each reaction section to be 450-500 ℃ and the reaction pressure to be 0.2-0.5 MPaG.
Compared with the prior art, the invention has the following beneficial effects:
(1) the reaction device improves the utilization efficiency of the catalyst in the reactor through the design of a plurality of reaction sections;
(2) according to the reaction method, methanol is fed in a multi-section gas phase manner, the methanol feeding amount of each section is gradually adjusted according to the reaction duration, the activity of the catalyst is fully utilized, the catalyst regeneration period is shortened, the catalyst regeneration period is prolonged by 150-300 h, the toluene conversion rate is improved by 5-10%, the selectivity of p-xylene is improved by more than 5%, the labor and operation cost is reduced, and the economy of the device is improved;
(3) the reaction method also utilizes the circulating hydrogen as a cooling substance to control the reaction temperature, and the methanol feeding adopts gas-phase feeding instead of liquid-phase feeding, thereby avoiding the problems of uneven gasification distribution and local carbonization caused by liquid-phase methanol feeding, simultaneously improving the safety of the device and having better industrial application prospect.
Drawings
FIG. 1 is a block diagram of a fixed bed reactor for the alkylation of toluene with methanol to produce para-xylene according to example 1 of the present invention;
wherein, 1-a reaction section, 2-a temperature controller, 3-a methanol feeding port and 4-a cooling material feeding port.
Detailed Description
In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the present invention, which is defined by the claims.
The following are typical but non-limiting examples of the invention:
example 1:
the embodiment provides a reaction device and a reaction method for producing p-xylene by alkylation of toluene and methanol, wherein the reaction device comprises a fixed bed reactor, and the fixed bed reactor comprises 4 reaction sections 1;
a top feeding hole and a side wall feeding hole are formed in the fixed bed reactor, and two groups of side wall feeding holes are formed between every two adjacent reaction sections 1 in the fixed bed reactor; each of the reaction sections 1 is provided with a temperature controller 2 in addition to the first reaction section.
Each reaction section 1 of the fixed bed reactor is filled with a catalyst.
The side wall feed inlets comprise 3 methanol feed inlets 3 and 3 cooling material feed inlets 4, wherein the number of the methanol feed inlets 3 is 3, and the number of the cooling material feed inlets 4 is 3; control valves are respectively and independently arranged on the feeding pipelines connected with the cooling material feeding port 4; each temperature controller 2 controls the opening of a control valve on the corresponding cooling material feeding pipeline.
The reaction device also comprises a heat exchange unit, a toluene separation unit and a xylene separation unit; and a cold fluid outlet of the heat exchange unit is connected with the top end of the fixed bed reactor, a bottom outlet of the fixed bed reactor is connected with a hot fluid inlet of the heat exchange unit, a hot fluid outlet of the heat exchange unit is connected with an inlet of the toluene separation unit, and an outlet of the toluene separation unit is connected with an inlet of the xylene separation unit.
The reaction method comprises the following steps:
mixing toluene, methanol and water vapor in a molar ratio of 1:0.86:0.9, and then carrying out first-stage gas phase feeding from the top end of the fixed bed reactor, and simultaneously carrying out 3-stage gas phase feeding on the residual methanol from the side wall of the fixed bed reactor, wherein the feeding amount of the methanol in the first stage is gradually reduced along with the reaction time, but the total feeding amount of the methanol is ensured to be unchanged; products obtained after reaction sequentially enter a heat exchange unit, a toluene separation unit and a xylene separation unit for heat exchange and separation to obtain p-xylene, tail gas obtained in the reaction process is used as circulating gas to return to the top end of the fixed bed reactor for first-stage gas phase feeding, and the molar content of hydrogen in the circulating gas is 67%; and introducing 3 sections of fed circulating hydrogen in the reaction process to control the reaction temperature of each reaction section 1 to be 450-500 ℃ and the reaction pressure to be 0.3 MPaG.
Wherein, the specific ratio of the methanol feeding amount of each section to the total methanol feeding amount along with the reaction time is shown in table 1:
TABLE 1
| Time (h) | First stage (%) | Second stage (%) | Third stage (%) | Fourth stage (%) |
| 0-500 | 41 | 30 | 19 | 10 |
| 500-1000 | 34 | 32 | 23 | 11 |
| 1000-1300 | 30 | 25 | 30 | 15 |
| 1300-1550 | 27 | 22 | 28 | 23 |
After reaction 1550h, catalyst regeneration was carried out.
Example 2:
this example provides a reaction apparatus for producing p-xylene by alkylation of toluene with methanol and a reaction method thereof, which are similar to the reaction apparatus of example 1 except that: the fixed bed reactor comprises 3 reaction sections 1; the number of the methanol feeding openings is 2, and the number of the cooling material feeding openings is 2.
The reaction method using the reaction device comprises the following steps:
mixing toluene, methanol and steam in a molar ratio of 1:0.7:0.55, and then carrying out first-stage gas phase feeding from the top end of the fixed bed reactor, and simultaneously carrying out 2-stage gas phase feeding on the methanol from the side wall of the fixed bed reactor, wherein the feeding amount of the methanol at the first stage is gradually reduced along with the reaction time, but the total feeding amount of the methanol is ensured to be unchanged; products obtained after reaction sequentially enter a heat exchange unit, a toluene separation unit and a xylene separation unit for heat exchange and separation to obtain p-xylene, tail gas obtained in the reaction process is used as circulating gas to return to the top end of the fixed bed reactor for first-stage gas phase feeding, and the molar content of hydrogen in the circulating gas is 66%; and introducing 2 sections of fed circulating hydrogen in the reaction process to control the reaction temperature of each reaction section 1 to be 450-500 ℃ and the reaction pressure to be 0.2 MPaG.
Wherein the specific ratio of the methanol feed to the total methanol feed over the reaction time is shown in Table 2:
TABLE 2
| Time (h) | First stage (%) | Second stage (%) | Third stage (%) |
| 0-400 | 50 | 30 | 20 |
| 400-750 | 45 | 35 | 20 |
| 750-1050 | 36 | 39 | 25 |
| 1050-1275 | 30 | 43 | 27 |
| 1275-1500 | 25 | 45 | 30 |
After 1500h of reaction, catalyst regeneration was carried out.
Example 3:
this example provides a reaction apparatus for producing p-xylene by alkylation of toluene with methanol and a reaction method thereof, which are different from the reaction apparatus of example 1 only in that: the fixed bed reactor comprises 7 reaction sections 1; the number of the methanol feeding openings is 6, and the number of the cooling material feeding openings is 6.
The reaction method using the reaction device comprises the following steps:
mixing toluene, methanol and steam in a molar ratio of 1:0.98:1.1, and then carrying out first-stage gas phase feeding from the top end of the fixed bed reactor, and simultaneously carrying out 6-stage gas phase feeding on the methanol from the side wall of the fixed bed reactor, wherein the feeding amount of the methanol at the first stage is gradually reduced along with the reaction time, but the total feeding amount of the methanol is ensured to be unchanged; products obtained after reaction sequentially enter a heat exchange unit, a toluene separation unit and a xylene separation unit for heat exchange and separation to obtain p-xylene, tail gas obtained in the reaction process is used as circulating gas to return to the top end of the fixed bed reactor for first-stage gas phase feeding, and the molar content of hydrogen in the circulating gas is 67%; and introducing 6 sections of fed circulating hydrogen in the reaction process to control the reaction temperature of each reaction section 1 to be 450-500 ℃ and the reaction pressure to be 0.5 MPaG.
Wherein the specific ratio of the methanol feed to the total methanol feed over the reaction time is shown in Table 3:
TABLE 3
After 1650h of reaction, catalyst regeneration was carried out.
Comparative example 1:
this comparative example provides a reaction apparatus for producing p-xylene by alkylation of toluene with methanol and a reaction method thereof, the reaction apparatus being referred to the reaction apparatus of example 1.
The reaction method using the reaction device comprises the following steps:
mixing toluene, methanol and steam with a molar ratio of 1:0.86:0.9, then carrying out first-stage gas phase feeding from the top end of the fixed bed reactor, meanwhile, carrying out 3-stage gas phase feeding on the methanol from the side wall of the fixed bed reactor, keeping the feeding amount of the methanol at each stage unchanged, sequentially feeding products obtained after reaction into a heat exchange unit, a toluene separation unit and a xylene separation unit for heat exchange and separation to obtain p-xylene, returning tail gas obtained in the reaction process as circulating gas to the top end of the fixed bed reactor for first-stage gas phase feeding, wherein the molar content of hydrogen in the circulating gas is 67%; and introducing 3 sections of feed circulating hydrogen in the reaction process to control the reaction temperature of each reaction section 1 to be 450-500 ℃ and the reaction pressure to be 0.3 MPaG.
Wherein, the specific ratio of the methanol feeding amount of each section to the total methanol feeding amount is shown in Table 4:
TABLE 4
| Time (h) | First stage (%) | Second stage (%) | Third stage (%) | Fourth stage (%) |
| 1350 | 34 | 32 | 23 | 11 |
After 1350h of reaction, catalyst regeneration was carried out.
The toluene conversion, the p-xylene selectivity and the catalyst regeneration period in examples 1 to 3 and comparative example 1 were measured and calculated, and the results are shown in table 5.
TABLE 5
| Conversion of toluene/% | P-xylene selectivity/%) | Regeneration period/h of catalyst | |
| Example 1 | 30 | 96 | 1550 |
| Example 2 | 29 | 95 | 1500 |
| Example 3 | 34 | 98 | 1650 |
| Comparative example 1 | 24 | 90 | 1350 |
It can be seen from the above examples and comparative examples that, the reaction method of the present invention utilizes the activity of the catalyst fully by feeding methanol in multiple stages of gas phase and gradually adjusting the methanol feeding amount of each stage according to the reaction duration, thereby improving the utilization efficiency of the catalyst in the reactor, reducing the catalyst regeneration period, prolonging the catalyst regeneration period by 150-300 h, increasing the toluene conversion rate by 5-10%, increasing the selectivity of p-xylene by more than 5%, reducing the labor and operation costs, and increasing the economy of the apparatus; the reaction method also utilizes the circulating hydrogen as a cooling substance to control the reaction temperature, and the methanol feeding adopts gas-phase feeding instead of liquid-phase feeding, thereby avoiding the problems of uneven gasification distribution and local carbonization caused by liquid-phase methanol feeding, simultaneously improving the safety of the device and having better industrial application prospect.
The applicant states that the present invention is illustrated by the above examples to show the products and detailed methods of the present invention, but the present invention is not limited to the above products and detailed methods, i.e. it is not meant that the present invention must rely on the above products and detailed methods to be carried out. It will be apparent to those skilled in the art that any modifications to the present invention, equivalents thereof, additions of additional operations, selection of specific ways, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. The reaction device for producing p-xylene through alkylation of toluene and methanol is characterized by comprising a fixed bed reactor, wherein the fixed bed reactor comprises at least 3 reaction sections;
the fixed bed reactor is provided with a top feeding hole and side wall feeding holes, and two groups of side wall feeding holes are arranged between two adjacent reaction sections in the fixed bed reactor; except the first reaction section, each reaction section is provided with a temperature controller.
2. The reactor apparatus as claimed in claim 1, wherein each reaction section of the fixed bed reactor is packed with a catalyst.
3. The reactor apparatus of claim 1 or 2, wherein the sidewall feed openings comprise a methanol feed opening and a cooling material feed opening;
preferably, the methanol feed inlet is at least 2;
preferably, the number of the cooling material inlets is at least 2;
preferably, the feed pipelines connected with the cooling material feed inlets are respectively and independently provided with control valves;
preferably, each of said temperature controllers controls the opening of a control valve on its corresponding cooling substance feed line.
4. The reaction apparatus according to any one of claims 1 to 3, further comprising a heat exchange unit, a toluene separation unit, and a xylene separation unit; and a cold fluid outlet of the heat exchange unit is connected with the top end of the fixed bed reactor, a bottom outlet of the fixed bed reactor is connected with a hot fluid inlet of the heat exchange unit, a hot fluid outlet of the heat exchange unit is connected with an inlet of the toluene separation unit, and an outlet of the toluene separation unit is connected with an inlet of the xylene separation unit.
5. A reaction method for producing paraxylene by using the reaction apparatus according to any one of claims 1 to 4, characterized by comprising the steps of:
mixing toluene, partial methanol and steam, and then carrying out first-stage gas-phase feeding from the top end of the fixed bed reactor, and simultaneously carrying out at least 2-stage gas-phase feeding on the residual methanol from the side wall of the fixed bed reactor, wherein the feeding amount of the methanol at the first stage is gradually reduced along with the reaction time, but the total feeding amount of the methanol is ensured to be unchanged; obtaining the p-xylene after reaction.
6. The reaction process according to claim 5, wherein the remaining methanol is fed in a gas phase from the side wall of the fixed bed reactor in not more than 6 stages.
7. The reaction process of claim 5 or 6, wherein the molar ratio of toluene, methanol and water vapor in the first stage gas phase feed is 1 (0.7-0.98) to (0.55-1.1);
preferably, the temperature of the first stage gas phase feeding is 450-500 ℃;
preferably, the feeding amount of the methanol in the first section gas phase feeding accounts for 18-50% of the total feeding amount of the methanol;
preferably, the methanol feeding amount of each section except the first section is 2 to 45% of the total methanol feeding amount.
8. The reaction process according to any one of claims 5 to 7, wherein the temperature of the reaction is 450 to 500 ℃;
preferably, the pressure of the reaction is 0.2-0.5 MPaG;
preferably, the catalyst used for the reaction comprises a shape selective catalyst comprising metal platinum.
9. The reaction method according to any one of claims 5 to 8, wherein a cooling material is introduced during the reaction to control the reaction temperature;
preferably, the cooling material is at least 2 stage feed;
preferably, the cooling substance comprises a cooling gas;
preferably, the cooling gas comprises hydrogen;
preferably, the hydrogen is recycled;
preferably, the reaction is followed by separation;
preferably, tail gas obtained in the separation process is used as circulating gas to return to the top end of the fixed bed reactor for first-stage gas phase feeding;
preferably, the molar content of hydrogen in the recycle gas is greater than 65%.
10. The reaction process according to any one of claims 5 to 9, characterized in that it comprises the following steps:
mixing toluene, methanol and water vapor in a molar ratio of 1 (0.7-0.98) (0.55-1.1), and then carrying out first-stage gas-phase feeding from the top end of the fixed bed reactor, and simultaneously carrying out at least 2-stage gas-phase feeding on the residual methanol from the side wall of the fixed bed reactor, wherein the feeding amount of the methanol in the first stage is gradually reduced along with the reaction time, but the total feeding amount of the methanol is ensured to be unchanged; products obtained after reaction sequentially enter a heat exchange unit, a toluene separation unit and a xylene separation unit for heat exchange and separation to obtain p-xylene, tail gas obtained in the reaction process is used as circulating gas to return to the top end of the fixed bed reactor for first-stage gas phase feeding, and the molar content of hydrogen in the circulating gas is more than 65%; and introducing at least 2 sections of feeding cooling substances in the reaction process to control the reaction temperature of each reaction section to be 450-500 ℃ and the reaction pressure to be 0.2-0.5 MPaG.
Priority Applications (1)
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| WO2023064684A1 (en) * | 2021-10-12 | 2023-04-20 | Exxonmobil Chemical Patents Inc. | Staged alkylation for producing xylene products |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2023064684A1 (en) * | 2021-10-12 | 2023-04-20 | Exxonmobil Chemical Patents Inc. | Staged alkylation for producing xylene products |
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