Method and system for preparing ethylbenzene through liquid phase alkylation

Abstract

The invention discloses a method and system for preparing ethylbenzene through liquid phase alkylation, and the method adopts the technical scheme of an external circulation multi-stage series-parallel fixed bed reactor with interstage heat exchange, and has the advantages that the pressure drop of a reaction system is reduced, the reaction feeding temperature is low, the interstage temperature rise is low, and the ethylbenzene yield is high. The method has the characteristics of low concentration of high-boiling-point substances, diethylbenzene and triethylbenzene in reaction products, can reduce the total benzene-to-olefin ratio of alkylation reaction, and reduces the number of sections of the reactor.

Description

Technical Field

[0001] The invention belongs to the field of chemical technology, and in particular relates to ethylbenzene preparation, and specifically, to a method and system for preparing ethylbenzene by liquid phase alkylation. Background Art

[0002] Ethylbenzene is one of the most important basic organic chemical raw materials, mainly used in the production of benzene and ethylene, and has a large market capacity.

[0003] Commercial ethylbenzene production methods are mainly divided into the dilute ethylene method and the pure ethylene method. The dilute ethylene method is mainly used in situations where raw material ethylene is scarce. It is a value-added utilization technology for low-quality raw materials. It uses a high-temperature, low-pressure gas phase process. The concentration of ethylbenzene and xylene produced is relatively high, usually greater than 600ppm, with high energy and material consumption, and the scale is generally small. The pure ethylene method is mainly used in large-scale ethylbenzene units, with production accounting for about 90% of the market. It is divided into gas phase method and liquid phase method. The gas phase method has a high reaction temperature, a high content of impurities such as ethylbenzene and xylene produced, and high energy and material consumption, and is gradually being eliminated by the market. The liquid phase alkylation process for ethylbenzene has outstanding advantages such as low reaction temperature, high purity of ethylbenzene products, and low energy and material consumption. It is the preferred process for large-scale ethylbenzene production.

[0004] Currently, the most commercialized liquid-phase ethylbenzene production processes are Lummus / UOP's EBone and ExxonMobil / Washinton's EBMAX. The two processes are relatively similar and both use multi-stage catalyst beds in cascade operation. Benzene enters from one end of the reactor, and ethylene enters from each catalyst bed in multiple stages. Heat is taken every two stages. Usually the catalyst bed has 6 to 8 stages. The lower the total benzene and ethylene molar ratio, the more stages there are.

[0005] CN1045284C relates to a process for producing ethylbenzene by liquid phase method of benzene and ethylene of the Petroleum Research Institute. The raw materials are mixed outside the reactor, and the partial reaction product is circulated externally to increase the local benzene-ethylene ratio. The alkylation reaction is divided into multiple catalyst beds, and heat is taken once every two catalyst stages. The catalyst beds are operated in cascade.

[0006] CN103539599B introduces a method of changing the distance between catalyst sections and gradually increasing the distance between catalyst bed sections to solve the problem of uneven alkylation feed. This problem can also be solved by changing the distributor structure and other methods. The alkylation reactor is the same as the traditional process.

[0007] CN1230405C introduces a method for the simultaneous alkylation of ethylene and benzene in the gas-liquid phase. The gas-liquid-solid three-phase alkylation reaction has relatively high requirements for the alkylation catalyst, the catalyst is easily pulverized, and the subsequent separation process is also relatively complicated. No industrial reports have been seen.

[0008] The alkylation process involved in the above prior art usually has an alkylation feed temperature of more than 200°C, and adopts a multi-stage catalyst cascade setting, and heat removal is performed every two or three stages to reduce the number of steam generators. In order to control the alkylation reaction to be liquid phase, ethylene multi-stage feeding and control of the outlet temperature of the material between stages are often used. The multi-stage catalyst cascade setting makes the alkylation reaction system pressure drop large, usually 0.3-0.4MPa. The pressure reduction will affect the solubility of ethylene in the subsequent reactors, thereby increasing the process risk of gas-phase ethylene, which is not conducive to the control of the molar ratio of benzene and ethylene in each stage. Using two or three stages to remove heat once makes the temperature rise of the material between stages larger than that of the feed, usually at 35-60°C. The higher feed temperature and larger temperature rise are not conducive to the control of diethylbenzene, triethylbenzene and high boiling points. Summary of the invention

[0009] The technical problem to be solved by the present invention is that the alkylation reaction temperature in the prior art is high, the temperature rise between stages is large, the concentration of high boiling points, diethylbenzene and triethylbenzene in the reaction product is high, the benzene-olefin ratio is high, the number of stages of the alkylation reactor is large, and the pressure drop in the reaction part is large. The present invention provides a method and system for preparing ethylbenzene by liquid phase alkylation, wherein, through the technical scheme of an external circulation multi-stage series-parallel fixed bed reactor with inter-stage heat exchange, the pressure drop of the reaction system is reduced, the reaction feed temperature is low, the temperature rise between stages is low, and the concentration of high boiling points, diethylbenzene and triethylbenzene in the reaction product is low, the total benzene-olefin ratio of the alkylation reaction can be reduced, and the number of reactor stages can be reduced.

[0010] In one aspect, the present invention provides a method for preparing ethylbenzene by liquid phase alkylation, the method comprising: reacting raw materials including liquid ethylene and benzene in a guard bed and m reaction sections connected in series, the liquid ethylene being divided into m+1 streams and the benzene being divided into one stream; wherein: (1) one stream of liquid ethylene and one stream of benzene enter the guard bed as feeds for the guard bed; (2) the output of the guard bed, one stream of liquid ethylene and one stream of optional alkylation product recycling material enter the first reaction section as feeds for the first reaction section; (3) the output of the previous reaction section, one stream of liquid ethylene and one stream of optional alkylation product recycling material enter the next reaction section as feeds for the next reaction section; (4) the output of the logical last reaction section is fully or partially taken out as an alkylation product, and when part of the output is taken out, the untaken portion is divided into 1 to m streams as the alkylation product recycling material in steps (1) to (3) and recycled to at least one of the first to (m-1) reaction sections.

[0011] In the preferred technical solution of the present invention, each reaction section independently comprises an upper bed layer and a lower bed layer arranged up and down, wherein the feed of each reaction section is fed between the upper bed layer and the lower bed layer of the section, and the feed is further divided into two streams, one stream of feed passes through the upper bed layer from bottom to top to form an upper bed layer discharge, and the other stream of feed passes through the lower bed layer from top to bottom to form a lower bed layer discharge, and the upper bed layer discharge and the lower bed layer discharge are mixed to form the discharge of the reaction section.

[0012] In a preferred technical solution of the present invention, the discharge of the previous reaction stage enters the next reaction stage after heat exchange; and / or the discharge of the logical last reaction stage is collected and / or recycled after heat exchange.

[0013] In a preferred technical solution of the present invention, the m reaction sections are arranged in one or more reactors; preferably, in each reactor, the reaction sections are arranged in series from bottom to top; more preferably, m=2-10.

[0014] In the preferred technical scheme of the present invention, the feed temperature of each reaction section is independently controlled to be 140-230°C, and the total feed pressure is controlled to be 2.5-3.5MPa; preferably, the feed temperature of each reaction section is independently controlled to be 180-210°C, and the total feed pressure is controlled to be 3.0-3.4MPa.

[0015] In a preferred technical solution of the present invention, the molar ratio of the total benzene feed amount to the total liquid phase ethylene feed amount in the method is controlled to be 2-6, preferably 2-4, and more preferably 2.5-3.

[0016] In a preferred technical solution of the present invention, based on 100 wt% of the total liquid ethylene feed used in the method, the liquid ethylene entering the guard bed accounts for 1 to 6 wt%, preferably 2 to 4 wt%; and / or, the feed amount of the liquid ethylene entering the first reaction zone is or The remaining liquid phase ethylene is evenly distributed to the remaining reaction sections (ie, the 2nd to mth reaction sections).

[0017] On the other hand, the present invention provides a system for preparing ethylbenzene by liquid phase alkylation, which is preferably used to carry out the method, and the system comprises a guard bed, m reaction sections, optionally m heat exchange units and pipelines; wherein each reaction section independently comprises an upper bed layer and a lower bed layer arranged up and down; according to the material flow direction, the upper bed layer and the lower bed layer in each reaction section are arranged in parallel; a reaction section is connected to a heat exchange unit to form an alkylation zone, and each alkylation zone is arranged in series in sequence along the material flow direction.

[0018] In a preferred technical solution of the present invention, according to the material flow direction, the guard bed is arranged before the m reaction stages; and / or, a benzene feed pipeline and a liquid ethylene feed pipeline are arranged below the guard bed, and a purified material discharge pipeline is arranged above the guard bed; and / or, m=2-10, preferably, m=3-6.

[0019] In the preferred technical solution of the present invention, for each reaction section: a feed port is arranged between the upper bed layer and the lower bed layer; preferably, for each reaction section, an upper bed layer feed pipeline is arranged between its feed port and the lower part of the upper bed layer, and a lower bed layer feed pipeline is arranged between its feed port and the upper part of the lower bed layer; more preferably, for each reaction section, an upper bed layer discharge pipeline is arranged at the upper part of its upper bed layer, and a lower bed layer discharge pipeline is arranged at the lower part of its lower bed layer.

[0020] In a preferred technical solution of the present invention, in the i-th reaction section, the pipeline formed by merging the upper bed discharge pipeline and the lower bed discharge pipeline is connected to the heat source inlet of the i-th heat exchange unit as a heat source feed pipeline, and the heat source outlet of the heat exchange unit is connected to the feed port of the next reaction section, wherein i=1 to (m-1); and / or, in the m-th reaction section, the pipeline formed by merging the upper bed discharge pipeline and the lower bed discharge pipeline is connected to the heat source inlet of the m-th heat exchange unit as a heat source feed pipeline, and an alkylation product delivery pipeline is arranged at the heat source outlet of the heat exchange unit.

[0021] In a preferred technical solution of the present invention, the system further comprises (m+1) liquid-phase ethylene feed pipelines, and the feed port of each reaction section and the bottom of the guard bed are each independently connected to an ethylene feed pipeline; and / or, a benzene feed pipeline is further arranged below the guard bed, and a discharge pipeline is arranged above the guard bed.

[0022] In a preferred technical solution of the present invention, a circulation pump, a product external collection pipeline and 1 to m circulating material transportation pipelines arranged in parallel are arranged on the alkylation product transportation pipeline, wherein the 1 to m circulating material transportation pipelines are connected to the feed port of at least one of the 1 to m reaction stages.

[0023] The endpoints and any values ​​of the scope disclosed in the present invention are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, the endpoint values ​​of each scope, the endpoint values ​​of each scope and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be regarded as specifically disclosed in this article.

[0024] Compared with the prior art, the present invention has the following beneficial effects: the reaction feed is fed from the middle of each reaction section, and the series and parallel operation of each bed layer is controlled, thereby reducing the pressure drop of the reaction system; the external circulation of the reaction product can flexibly adjust the molar ratio of benzene and ethylene in each reaction section and the temperature rise between sections, thereby achieving the purpose of reducing the reaction temperature and the temperature rise between reaction sections, and the concentrations of high boiling points, diethylbenzene and triethylbenzene in the reaction product are low, thereby achieving better technical effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the structure of the system of the present invention is shown.

[0026] 1-guard bed; 2-reactor; 3-heat exchange unit (such as steam generator); 4-circulation pump. DETAILED DESCRIPTION

[0027] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0028] One of the purposes of the present invention is to provide a method for preparing ethylbenzene by liquid phase alkylation, the method comprising: reacting raw materials including liquid phase ethylene and benzene in a guard bed and m reaction sections connected in series, the liquid phase ethylene is divided into m+1 strands, and the benzene is one strand; wherein:

[0029] (1) a stream of liquid ethylene and a stream of benzene are fed into the guard bed as feeds to obtain a purified material;

[0030] (2) the output of the guard bed (i.e. the purified material) and a stream of liquid ethylene and an optional stream of alkylation product recycling material are fed into the first reaction stage as feeds for the first reaction stage;

[0031] (3) the discharge from the previous reaction stage, a stream of liquid ethylene and an optional stream of alkylation product recycling feed are fed into the next reaction stage as feeds to the next reaction stage;

[0032] (4) All or part of the output of the logically last reaction stage (i.e., the mth reaction stage) is extracted as an alkylation product. When part of the output is extracted, the unextracted part is divided into 1 to m streams and used as the alkylation product recycling material of steps (1) to (3) to be recycled back to at least one of the 1st to (m-1)th reaction stages.

[0033] Wherein, the feed of the first (or first logical position) reaction section includes a stream of liquid ethylene, the output of the guard bed, i.e., the purified material, and an optional stream of alkylation product recycling material; the feed of the i-th (or i-th logical position) reaction section includes a stream of liquid ethylene, the output of the (i-1)th reaction section (i.e., the output of the i-1st logical position reaction section), and an optional stream of alkylation product recycling material, i=2 to m. The logical position of the present invention is to arrange the m reaction sections in series order, excluding the guard bed.

[0034] In a preferred embodiment, the guard bed is fed from bottom to top.

[0035] In a preferred embodiment, the m reaction sections are connected in series along the material flow direction, and are sequentially the first (ie, logical first) to mth (ie, logical last) reaction sections in series order or along the material flow direction.

[0036] In a further preferred embodiment, each reaction section independently comprises an upper bed layer and a lower bed layer arranged up and down, wherein the feed of each reaction section is fed between the upper bed layer and the lower bed layer of the section, and then the feed is divided into two streams, one stream of feed passes through the upper bed layer from bottom to top to form an upper bed layer discharge, and the other stream of feed passes through the lower bed layer from top to bottom to form a lower bed layer discharge, and the upper bed layer discharge and the lower bed layer discharge are mixed to form the discharge of the reaction section.

[0037] In a preferred embodiment, the discharge of the previous reaction stage enters the next reaction stage after heat exchange; and / or the discharge of the logical last reaction stage is collected and / or recycled after heat exchange.

[0038] In a further preferred embodiment, the temperature of the discharge from the previous reaction stage is reduced to the feed requirement for the next reaction stage after the heat exchange.

[0039] In a preferred embodiment, a steam generator is used for the heat exchange.

[0040] In a further preferred embodiment, the upper bed discharge and the lower bed discharge of each reaction stage are used as heat sources for a steam generator to generate low-pressure steam, and the pressure of the low-pressure steam is 0.25-0.35 MPa.

[0041] In a preferred embodiment, the output of the logical last reaction stage is collected or circulated by a circulation pump after heat exchange, wherein the collected part is sent to a subsequent separation unit.

[0042] In a preferred embodiment, the m reaction sections are arranged in one or more reactors.

[0043] In a further preferred embodiment, each reaction section is arranged in series from bottom to top in each reactor.

[0044] In a preferred embodiment, m=2-10, preferably, m=3-6, more preferably, m=4-5, for example, m=2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0045] In a preferred embodiment, the upper bed layer and the lower bed layer are each independently loaded with a liquid-phase alkylation catalyst for producing ethylbenzene.

[0046] The liquid phase alkylation catalyst for preparing ethylbenzene can be any catalyst disclosed in the prior art for preparing ethylbenzene by liquid phase alkylation, preferably but not limited to the EBC series alkylation catalyst or an alkylation catalyst with equivalent performance. EBC is a commercialized catalyst in China.

[0047] In a further preferred embodiment, a liquid phase alkylation catalyst for producing ethylbenzene is loaded on the guard bed. A benzene material reaching the alkylation reaction feed temperature is mixed with a liquid phase ethylene and then enters the guard bed, where the basic nitrogen compounds in the raw materials are removed under the action of the catalyst and a preliminary reaction of ethylene and benzene is carried out.

[0048] In a further preferred embodiment, the guard bed is loaded with the same catalyst as that in the reaction section.

[0049] In a preferred embodiment, the feed temperature of each reaction stage is independently controlled to be 140-230° C., the total feed pressure is controlled to be 2.5-3.5 MPa, and the molar ratio of benzene to ethylene is 10-50.

[0050] For example, the feed temperature of each reaction zone is independently controlled to be 140°C, 160°C, 180°C, 200°C, 220°C or 230°C, the pressure is 2.5, 2.6, 2.8, 3.0, 3.2, 3.4 or 3.5 MPa, and the molar ratio of benzene to ethylene is 10, 20, 30, 40 or 50.

[0051] In a further preferred embodiment, the feed temperature of each reaction stage is independently controlled to be 180-210° C., the total feed pressure is controlled to be 3.0-3.4 MPa, and the molar ratio of benzene to ethylene is 10-40, preferably 15-40 or 18-40.

[0052] Among them, the inventors found in a large number of experiments that when the molar ratio of benzene to ethylene in each reaction section is lower than the above limit, it will lead to a large temperature rise and pressure drop in the section, and an increase in the impurity content of the alkylation product. Therefore, it is necessary to control the benzene / ethylene molar ratio of each section. After experiments, the inventors found that the alkylation product extracted from the logical last reaction section contains unreacted benzene. Therefore, recycling part of the alkylation product back to the reaction section can increase the benzene / ethylene molar ratio therein, thereby improving the quality of the alkylation product; in addition, the larger the benzene-ethylene ratio, the smaller the temperature rise between sections, the lower the outlet temperature, the higher the saturated solubility, and the lower the process risk of the gas phase.

[0053] In a preferred embodiment, the molar ratio of the total benzene feed to the total liquid ethylene feed in the method is controlled to be 2-6, preferably 2-4, more preferably 2.5-3, for example 2, 2.5, 3, 3.5 or 4.

[0054] In a preferred embodiment, based on 100 wt% of the total liquid ethylene feed used in the method, the liquid ethylene entering the guard bed accounts for 1 to 6 wt%, preferably 2 to 4 wt% (e.g., 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt% or 6 wt%), and the liquid ethylene feed entering the first reaction zone is or The remaining liquid phase ethylene is evenly distributed to the remaining reaction sections (ie, the 2nd to mth reaction sections).

[0055] In a preferred embodiment, the weight ratio of the alkylation product recycling material in each reaction stage feed to the total benzene feed is 0 to 1, for example, 1, 0.2, 0.4, 0.6, 0.8 or 1, wherein the control of this ratio is mainly to control the temperature rise between stages and the total benzene-olefin ratio, because excessive temperature rise between stages will affect product quality, and the total benzene-olefin ratio affects energy consumption and is a key indicator of process technology advancement.

[0056] Among them, the recycled material can be recycled back to one or more or each of the 1st to mth reaction stages. The main purpose is to control the molar ratio of benzene and ethylene in each reaction stage, so as to achieve the purpose of controlling the temperature rise and ethylene solubility of each stage and avoid the vaporization of ethylene in the alkylation reactor.

[0057] In a preferred embodiment, the alkylation product recycle material is recycled back to the first reaction stage.

[0058] The inventors have found through a large number of experiments that recycling the alkylation product recycling material back to the first reaction stage has the best effect.

[0059] In a preferred embodiment, an upper bed discharge pipeline is provided above each reaction section for discharging the upper bed; and a lower bed discharge pipeline is provided below each reaction section for discharging the lower bed.

[0060] In a further preferred embodiment, a flow control valve and a pressure detector are independently provided on the upper bed layer discharge pipeline and the lower bed layer discharge pipeline, and the flow control valve is electrically connected to the pressure detector.

[0061] Among them, the upper and lower discharge pipelines of each reaction section are equipped with pressure control to control the difference between the feed pressure and the discharge pressure of the reaction section respectively. By fine-tuning the upper and lower discharge pressures to be equal, the flow rate through the upper and lower layers of catalyst is achieved to be the same.

[0062] In a further preferred embodiment, the upper bed discharge pipeline and the lower bed discharge pipeline are both connected to the heat source inlet of the steam generator.

[0063] In the present invention, the discharge of each bed layer in each reaction section can be directly used for heat exchange, so that the feed temperature entering each bed layer is relatively low. Specifically, after a large number of experimental studies, the inventors found that the use of materials flowing in parallel-series mode can not only reduce the use of steam generators, but also ensure the temperature rise of each reaction section without increasing steam generation, further reduce the impurity content in the alkylation product, and improve the quality of the alkylation product. If a technical solution is to add a steam generator after a bed layer, it will not only increase the cost, but also seriously complicate the process flow, which is not suitable for wide field application.

[0064] A second object of the present invention is to provide a system for preparing ethylbenzene by liquid phase alkylation, preferably for carrying out the method described in one of the objects of the present invention, wherein the system comprises a guard bed, m reaction sections, optionally m heat exchange units and pipelines; wherein each reaction section independently comprises an upper bed layer and a lower bed layer arranged up and down; according to the material flow direction, the upper bed layer and the lower bed layer in each reaction section are arranged in parallel; a reaction section is connected to a heat exchange unit to form an alkylation zone (a total of m alkylation zones), and each alkylation zone is arranged in series in sequence along the material flow direction.

[0065] The m reaction sections are sequentially arranged from bottom to top in one reactor or are arranged in series in multiple reactors.

[0066] In a preferred embodiment, according to the material flow direction, the guard bed is arranged before the m reaction stages.

[0067] In a preferred embodiment, the m heat exchange units are sequentially the 1st to the mth heat exchange units along the material flow direction, wherein the ith reaction section is connected to the ith heat exchange unit to form the ith alkylation zone, i=1-m.

[0068] Wherein, one reaction section and one heat exchange unit are connected in series to form one alkylation zone, that is, the system includes m alkylation zones.

[0069] In a preferred embodiment, for each reaction stage: a feed inlet is provided between the upper bed layer and the lower bed layer.

[0070] Among them, when there are m reaction sections, there are m feed inlets.

[0071] In a further preferred embodiment, for each reaction stage, an upper bed feed pipeline is provided between its feed port and the lower part of the upper bed layer, and a lower bed feed pipeline is provided between its feed port and the upper part of the lower bed layer.

[0072] Wherein, the upper bed layer feed pipeline and the lower bed layer feed pipeline are arranged in parallel.

[0073] In a further preferred embodiment, for each reaction stage, an upper bed discharge pipeline is arranged at the upper part of the upper bed layer, and a lower bed discharge pipeline is arranged at the lower part of the lower bed layer.

[0074] Among them, the long bed layer feed pipeline is connected in series with the upper bed layer discharge pipeline, the lower bed layer feed pipeline is connected in series with the lower bed layer discharge pipeline, and the upper bed layer discharge pipeline is arranged in parallel with the lower bed layer discharge pipeline.

[0075] In a preferred embodiment, in a preferred embodiment, each heat exchange unit independently includes a heat source inlet and a heat source outlet, and the heat source outlet of the i-th heat exchange unit is connected to the feed inlet of the (i+1)-th reaction section, i=1~(m-1).

[0076] In a further preferred embodiment, in the i-th reaction stage, the pipeline formed by the merging of the upper bed discharge pipeline and the lower bed discharge pipeline is connected to the heat source inlet of the i-th heat exchange unit as a heat source feed pipeline, and the heat source outlet of the heat exchange unit is connected to the feed port of the next reaction stage, wherein i=1~(m-1).

[0077] In a further preferred embodiment, in the mth reaction section, the pipeline formed by the merging of the upper bed discharge pipeline and the lower bed discharge pipeline is connected to the heat source inlet of the mth heat exchange unit as a heat source feed pipeline, and an alkylation product delivery pipeline is provided at the heat source outlet of the heat exchange unit.

[0078] In a preferred embodiment, each heat exchange unit independently includes a heat source inlet and a heat source outlet.

[0079] In a further preferred embodiment, for the i-th alkylation zone, the heat source inlet of the i-th heat exchange unit is connected to the upper bed discharge pipeline and the lower bed discharge pipeline, i=1-m.

[0080] In a further preferred embodiment, for the i-th alkylation zone, a control valve and a pressure detector are independently provided on the upper bed discharge pipeline and the lower bed discharge pipeline, and the control valve is electrically connected to the pressure detector.

[0081] In a preferred embodiment, a circulation pump, a product external collection pipeline and 1 to m circulating material conveying pipelines arranged in parallel are arranged on the alkylation product conveying pipeline, and the 1 to m circulating material conveying pipelines are arranged in parallel (the 1st to mth circulating material conveying pipelines in sequence), wherein the 1 to m circulating material conveying pipelines are connected to the feed port of at least one of the 1 to m reaction stages.

[0082] In the present invention, when m reaction sections are arranged in one reactor, the reaction sections, heat exchange units, and circulating material conveying pipelines are sequentially 1, 2, 3...i...m from bottom to top.

[0083] In a further preferred embodiment, a flow control valve and a pressure detector are provided on the circulating material conveying pipeline, and the flow control valve is electrically connected to the pressure detector.

[0084] In a preferred embodiment, the system further comprises (m+1) liquid-phase ethylene feed pipelines, and the feed inlet of each reaction section and the bottom of the guard bed are each independently connected to an ethylene feed pipeline.

[0085] In this way, the feed inlet of each reaction section is connected to the ethylene feed pipeline, the circulating material conveying pipeline and the heat source outlet of the heat exchange unit.

[0086] In a preferred embodiment, a benzene feed pipeline is further arranged below the guard bed layer, and a (purified material) discharge pipeline is arranged above the guard bed layer.

[0087] In a further preferred embodiment, the purified material discharge pipeline is connected in series with the first reaction stage, preferably connected with the feed inlet of the first reaction stage.

[0088] In a preferred embodiment, the heat exchange unit is a steam generator.

[0089] In a preferred embodiment, m=2-10, preferably, m=3-6, for example, m=2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0090] In a preferred embodiment, the guard bed and the alkylation bed are each independently loaded with a liquid-phase alkylation catalyst for producing ethylbenzene for liquid-phase alkylation.

[0091] The catalyst may be any catalyst disclosed in the prior art for liquid phase alkylation to produce ethylbenzene, preferably but not limited to EBC series alkylation catalysts.

[0092] Example

[0093] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0094] It should also be noted that the various specific technical features described in the following specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0095] In addition, the various embodiments of the present invention may be arbitrarily combined as long as they do not violate the concept of the present invention. The technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0096] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0097] The protective bed of the following examples and comparative examples is filled with the same catalyst as the reaction section, and the catalyst prepared in Example 1 of the patent CN112705252A is used. The specific preparation process is as follows: 1.87g aluminum sulfate, 2.02g sodium hydroxide, 1.48g sodium metaborate, 6.93g hexamethyleneimine, 8.40g white carbon black, and 61.64g water are mixed evenly under vigorous stirring, aged at 40°C for 6h to obtain a white uniform gel. The gel is transferred to a stainless steel reactor lined with polytetrafluoroethylene, crystallized at 140°C for 5d (days) under stirring, and the crystallization stirring speed is 200r / min. After the crystallization is completed, it is cooled to room temperature with water, washed, dried at 110°C for 4h, and then 30% by weight of alumina binder is added, extruded, and roasted at 500°C for 6h to obtain particles. The above particles were placed in a 1 mol / kg ammonium nitrate solution, with a solid-liquid weight ratio (weight ratio of boron-containing MWW molecular sieve to ammonium salt solvent) of 1:20, exchanged twice at 30°C, each time for 2.5 hours, washed, dried at 110°C for 4 hours, and calcined at 500°C in an air atmosphere for 6 hours, and marked as A. Based on the total weight of the liquid phase alkylation catalyst A, the content of the molecular sieve with the MWW topology structure was 70% by weight, and the content of the binder was 30% by weight.

[0098] [Example 1]

[0099] A 650,000 t / a benzene and ethylene liquid phase alkylation unit (8,000 operating hours per year) uses Figure 1The liquid phase alkylation system for producing ethylbenzene shown in the figure uses EBC-3 commercial catalyst as the catalyst, and the total benzene and ethylene molar ratio is 2.8. The total feed amount of raw benzene is 172 tons / hour, the temperature is 180℃, and the pressure is 3.4MPa. The total feed amount of liquid phase ethylene is 21.7t / h, the temperature is 120℃, the pressure is 3.4MPa, and it is divided into six streams, the first stream is 0.65t / h, the second stream is 3.69t / h, and the other four streams are fed with 4.34t / h. The alkylation reactor 2 is divided into 5 reaction sections, each reaction section independently includes two upper and lower catalyst beds, and the reaction feed is fed from the middle of the two catalyst beds. The 5 reaction sections are operated in cascade. The raw benzene and the first stream of ethylene are mixed and then enter the guard bed, and the outlet temperature is 186.4℃. The discharge from the guard bed is mixed with the second stream of ethylene and the alkylation product recycling material and then fed from the middle of the first reaction stage. The discharge temperature of the first reaction stage is 201°C. The upper and lower discharges of the first reaction stage are mixed and used as the heat source of the steam generator to generate 0.35MPa low-pressure steam. After taking heat, the temperature is 180°C, and it is mixed with the third stream of ethylene as the feed for the second reaction stage. The subsequent three reaction stages have the same process as the second reaction stage. The discharge from the alkylation reactor (i.e., the discharge from the fifth reaction stage) is partially sent to the separation unit as the alkylation product through the circulation pump, and partially sent to the first reaction stage as the recycling material. The other groups of reaction stages are not provided with recycling materials, and the recycling material amount / total benzene feed amount is 1.0.

[0100] The total pressure drop of the reaction system is 0.2MPa. The high boiling substances in the alkylation material are 0.08wt%, diethylbenzene is 5.39wt%, and triethylbenzene is 0.34wt%. 39t / h of 0.35MPa low-pressure steam is generated. The feed temperature of each reaction section is 180°C, the temperature rise of each section is 20°C, and the molar ratio of benzene to ethylene in each reaction section is 19.1-26.4.

[0101] [Example 2]

[0102] A 650,000 t / a benzene and ethylene liquid phase alkylation unit (8,000 operating hours per year) uses Figure 1 The liquid phase alkylation technology for producing ethylbenzene shown in the embodiment uses commercial EBC-3 catalyst, the total benzene and ethylene molar ratio is 2.8, no circulation pump 4 is provided (i.e. all external collection is not circulated), the discharge temperature of each reaction section is 220-230°C, and the rest is the same as in Example 1.

[0103] The total pressure drop of the reaction system is 0.2MPa, the high boiling point substances in the alkylation material are 0.11wt%, diethylbenzene is 5.95wt%, and triethylbenzene is 0.37wt%, 0.35MPa low-pressure steam is generated at 39t / h, the feed temperature of each reaction section is 180°C, the temperature rise between sections is 40°C to 50°C, and the molar ratio of benzene to ethylene in each reaction section is 10.5 to 16.4.

[0104] [Example 3]

[0105] A 650,000 t / a benzene and ethylene liquid phase alkylation unit (8,000 operating hours per year) uses Figure 1 The liquid phase alkylation technology for preparing ethylbenzene shown in the embodiment adopts commercial EBC-3 catalyst, and the molar ratio of total benzene to ethylene is 3. The total feed amount of raw benzene is 184 tons / hour, and the liquid phase ethylene is divided into five streams, the first stream is 0.87 t / h, the second stream is 4.56 t / h, and the other three streams are fed with 5.43 t / h. The alkylation reactor 2 is divided into 4 reaction sections. The raw benzene and the first stream of ethylene are mixed and then enter the guard bed layer. The outlet temperature is 188°C, and the discharge temperature of each reaction section is 205-207°C. The discharge of the alkylation reactor is partially sent to the separation unit as the alkylation product through the circulation pump, and partially enters the first reaction section as the alkylation product circulation material. The other reaction sections are not provided with the alkylation product circulation material, and the alkylation product circulation material amount / total benzene feed amount is 0.8. The rest is the same as Example 1.

[0106] The total pressure drop of the reaction system is 0.16MPa, the high boiling point substances in the alkylation material are 0.09wt%, diethylbenzene is 5.23wt%, and triethylbenzene is 0.33wt%. 32t / h of 0.35MPa low-pressure steam is generated, the feed temperature of each reaction section is 180°C, the temperature rise between sections is 25°C to 27°C, and the molar ratio of benzene to ethylene in each reaction section is 15.5 to 21.4.

[0107] [Example 4]

[0108] A 650,000 t / a benzene and ethylene liquid phase alkylation unit (8,000 operating hours per year) uses Figure 1 The liquid phase alkylation technology for preparing ethylbenzene shown in the embodiment adopts commercial EBC-3 catalyst, and the molar ratio of total benzene to ethylene is 2.5. The total feed amount of raw benzene is 153 tons / hour, and the liquid phase ethylene is divided into six strands, the first strand is 0.43t / h, the second strand is 3.91t / h, and the other four strands are fed with 4.34t / h. The alkylation reactor 2 is divided into 5 reaction sections. The raw benzene and the first strand of ethylene are mixed and then enter the guard bed layer. The outlet temperature is 185°C, and the discharge temperature of each reaction section is 208°C to 211°C. The discharge of the alkylation reactor is partially sent to the separation unit as an alkylation product through a circulation pump, and partially enters the first reaction section as a circulating material. The other groups of reaction sections are not provided with circulating materials, and the circulating material amount / total benzene feed amount is 0.5. The rest is the same as Example 1.

[0109] The total pressure drop of the reaction system is 0.2MPa, the high boiling point substances in the alkylation material are 0.10wt%, diethylbenzene is 5.26wt%, and triethylbenzene is 0.35wt%, 0.25MPa low-pressure steam is generated at 38t / h, the feed temperature of each reaction section is 180°C, the temperature rise between sections is 28°C to 31°C, and the molar ratio of benzene to ethylene in each reaction section is 12.6 to 17.8.

[0110] [Example 5]

[0111] A 650,000 t / a benzene and ethylene liquid phase alkylation unit (8,000 operating hours per year) uses Figure 1 The liquid phase alkylation technology for producing ethylbenzene shown in the embodiment adopts commercial EBC-3 catalyst, and the molar ratio of total benzene to ethylene is 2.8. The pressure of raw benzene is 3.2MPa, the outlet temperature of the first three reaction stages is 218-220°C, and the outlet temperature of the last two reaction stages is 212°C. The outlet of the alkylation reactor is partially sent to the separation unit as an alkylation product through a circulation pump, and partially sent to the fourth reaction stage as a circulation material. The other reaction stages are not provided with circulation materials, and the circulation material amount / total benzene feed amount is 0.2. The rest is the same as in Example 1.

[0112] The total pressure drop of the reaction system is 0.2 MPa. The high boiling point substances in the alkylation material are 0.10 wt%, diethylbenzene is 5.39 wt%, and triethylbenzene is 0.35 wt%. 39 t / h of 0.35 MPa low-pressure steam is generated. The feed temperature of each reaction section is 180°C. The temperature rise between the first three groups of reaction sections is 38-40°C, and the temperature rise between the last two reaction sections is 32°C. The molar ratio of benzene to ethylene in each reaction section is 12.2-16.4.

[0113] [Comparative Example 1]

[0114] A 650,000 tons / year ethylbenzene unit (8,000 operating hours per year) uses conventional benzene and ethylene liquid phase ethylbenzene technology (i.e., each bed is connected in series in sequence, and every two beds are connected in series as a reaction section), uses EBC-3 commercial catalyst, and the total benzene and ethylene molar ratio is 2.8. The total feed rate of raw benzene is 172 tons / hour, the temperature is 205℃, and the pressure is 3.4MPa. The total feed rate of liquid phase ethylene is 21.7t / h, the temperature is 120℃, the pressure is 3.4MPa, and it is divided into 11 strands, the first strand is 0.65t / h, the second strand is 1.52t / h, and the other nine strands are fed at 2.17t / h. The alkylation reactor is divided into 10 catalyst beds, and each catalyst bed is fed from the bottom and discharged from the top, and operates in cascade. The raw benzene and the first strand of ethylene are mixed and enter the guard bed, and the outlet temperature is 211℃. The output from the guard bed is mixed with the second stream of ethylene and fed from below the first catalyst bed. After every two catalyst beds (i.e. a reaction stage) are connected in series, inter-stage heat extraction is carried out to generate 1.2MPa low-pressure steam. The temperature after heat extraction is 205°C. After mixing with ethylene, it is fed from the bottom of the catalyst layer into the catalyst bed as the next logical position.

[0115] The total pressure drop of the reaction system is 0.4MPa. The high boiling substances in the alkylation material are 0.17wt%, diethylbenzene is 6.58wt%, and triethylbenzene is 0.41wt%. 35t / h of 1.2MPa low-pressure steam is generated. The feed temperature of each catalyst layer is 205-210℃, and the temperature rise between stages is 35℃.

[0116] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing ethylbenzene by liquid phase alkylation, the method comprising: Raw materials including liquid ethylene and benzene react in a guard bed and m reaction sections connected in series, the liquid ethylene is divided into m+1 strands, and the benzene is one strand; wherein: (1) a stream of liquid ethylene and a stream of benzene as feeds to the guard bed enter the guard bed; (2) the output of the guard bed, a stream of liquid ethylene and an optional stream of alkylation product recycling feed are fed into the first reaction stage as feeds for the first reaction stage; (3) the discharge from the previous reaction stage, a stream of liquid ethylene and an optional stream of alkylation product recycling feed are fed into the next reaction stage as feeds to the next reaction stage; (4) The output of the logically last reaction stage is entirely or partially produced as an alkylation product. When a portion of the output is produced, the unproduced portion is divided into 1 to m streams and used as the alkylation product recycling material of steps (1) to (3) to be recycled to at least one of the 1st to (m-1)th reaction stages.

2. The method according to claim 1, characterized in that Each reaction section independently comprises an upper bed layer and a lower bed layer arranged up and down, wherein the feed of each reaction section is fed between the upper bed layer and the lower bed layer of the section, and the feed is further divided into two streams, one stream of feed passes through the upper bed layer from bottom to top to form upper bed layer discharge, and the other stream of feed passes through the lower bed layer from top to bottom to form lower bed layer discharge, and the upper bed layer discharge and the lower bed layer discharge are mixed to form the discharge of the reaction section.

3. The method according to claim 1, characterized in that The discharge of the previous reaction stage enters the next reaction stage after heat exchange; and / or the discharge of the logical last reaction stage is collected and / or recycled after heat exchange.

4. The method according to claim 1, characterized in that: The m reaction sections are arranged in one or more reactors; preferably, in each reactor, the reaction sections are arranged in series from bottom to top; more preferably, m=2-10.

5. The method according to claim 1, characterized in that The feed temperature of each reaction section is independently controlled to be 140-230°C, and the total feed pressure is controlled to be 2.5-3.5MPa; preferably, the feed temperature of each reaction section is independently controlled to be 180-210°C, and the total feed pressure is controlled to be 3.0-3.4MPa.

6. The method according to claim 1, characterized in that The molar ratio of the total benzene feed amount to the total liquid phase ethylene feed amount in the method is controlled to be 2-6, preferably 2-4, and more preferably 2.5-3.

7. The method according to any one of claims 1 to 6, characterized in that: Based on 100 wt% of the total liquid ethylene feed used in the method, the liquid ethylene entering the guard bed accounts for 1 to 6 wt%, preferably 2 to 4 wt%; and / or, The feed rate of liquid ethylene into the first reaction section is or The remaining liquid ethylene is evenly distributed to the remaining reaction stages.

8. A system for preparing ethylbenzene by liquid phase alkylation, preferably for carrying out the method according to any one of claims 1 to 7, the system comprising a guard bed, m reaction sections and optionally m heat exchange units; wherein: Each reaction section independently comprises an upper bed layer and a lower bed layer arranged up and down; the upper bed layer and the lower bed layer in each reaction section are arranged in parallel according to the material flow direction; a reaction section is connected with a heat exchange unit to form an alkylation zone, and each alkylation zone is arranged in series in sequence along the material flow direction.

9. The system according to claim 8, characterized in that According to the material flow direction, the guard bed is arranged before the m reaction stages; and / or, A benzene feed pipeline and a liquid ethylene feed pipeline are arranged below the guard bed layer, and a purified material discharge pipeline is arranged above the guard bed layer; and / or, m=2-10, preferably, m=3-6.

10. The system according to claim 8, characterized in that For each reaction section: a feed port is arranged between the upper bed layer and the lower bed layer; preferably, for each reaction section, an upper bed layer feed pipeline is arranged between its feed port and the lower part of the upper bed layer, and a lower bed layer feed pipeline is arranged between its feed port and the upper part of the lower bed layer; more preferably, for each reaction section, an upper bed layer discharge pipeline is arranged at the upper part of the upper bed layer, and a lower bed layer discharge pipeline is arranged at the lower part of the lower bed layer.

11. The system according to claim 10, characterized in that In the i-th reaction stage, the pipeline formed by the confluence of the upper bed discharge pipeline and the lower bed discharge pipeline is connected to the heat source inlet of the i-th heat exchange unit as the heat source feed pipeline, and the heat source outlet of the heat exchange unit is connected to the feed port of the next reaction stage, wherein i=1 to (m-1); and / or, In the mth reaction section, the pipeline formed by merging the upper bed discharge pipeline and the lower bed discharge pipeline is connected to the heat source inlet of the mth heat exchange unit as a heat source feed pipeline, and an alkylation product delivery pipeline is arranged at the heat source outlet of the heat exchange unit.

12. The system according to any one of claims 9 to 11, characterized in that: The system further comprises (m+1) liquid-phase ethylene feed pipelines, and the feed port of each reaction section and the bottom of the guard bed are each independently connected to an ethylene feed pipeline; and / or, A benzene feed pipeline is further arranged below the guard bed layer, and a discharge pipeline is arranged above the guard bed layer.

13. The system according to claim 12, characterized in that The alkylation product delivery pipeline is provided with a circulation pump, a product external collection pipeline and 1 to m circulating material delivery pipelines arranged in parallel, wherein the 1 to m circulating material delivery pipelines are connected to a feed port of at least one of the 1 to m reaction sections.

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