Tandem reaction system for generating alkyl olefine acid ester compound through gas phase condensation

Abstract

The utility model provides a cascade reaction system for generating an alkyl gadoleic acid ester compound through gas phase condensation, relates to the technical field of organic synthesis, and synthesizes the alkyl gadoleic acid ester compound by performing gas phase condensation reaction under proper process conditions through a multi-stage cascade reaction system. The operation, switching and regeneration of the new and old reaction systems are periodically carried out according to corresponding rules, so that the fluctuation of the content of the product alkyl gadoleic acid ester compound in each reaction period process is reduced, and the basic stability of the content of the alkyl gadoleic acid ester compound is kept; stable raw material conditions are provided for further rectification and purification of alkyl olefine acid ester compounds in a subsequent separation section; in a word, the device solves the technical problem of large fluctuation of the content of the alkyl olefine acid ester compound in the product, and achieves the technical effects of effectively reducing the fluctuation of the content of the alkyl olefine acid ester compound, improving the operation stability of the subsequent separation and rectification section and prolonging the single activity period of the catalyst.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of organic synthesis especially relates to a series reaction system of alkyl alkenoate compound generated by gas phase condensation. BACKGROUND

[0002] Alkyl alkenoate compound is an important organic chemical raw material, and typical common and relatively important is acrylate compound, such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, n-pentyl methacrylate, ethyl methyl acrylate, ethyl acrylate, ethyl acrylate, ethyl acrylate, and butyl acrylate and each isomer etc.. Because alkyl alkenoate compound contains unsaturated olefin double bond, is active, can occur self-polymerization, or copolymerization with other monomers, and the polymer generated by polymerization has excellent physical properties such as transparency, low toxicity, easy to prepare and wide bonding, and has good chemical properties such as weather resistance, heat resistance, water resistance, ultraviolet light resistance, so it is widely used in paint, adhesive, leather, chemical fiber, papermaking and printing industries, and is an important raw material for producing adhesive, synthetic resin, special rubber, plastic and high molecular coating.

[0003] Taking the production process technology of methyl methacrylate (MMA) as an example, the most economical and most potential development of methyl methacrylate product production is ethylene two-step process, which can obtain methyl methacrylate through two-step reaction, the first step is that ethylene, carbon monoxide and methanol are synthesized into methyl propionate by carbonyl synthesis, and the second step is that methyl propionate and formaldehyde are subjected to gas phase condensation reaction to obtain methyl methacrylate. The raw material of ethylene two-step process is widely available, cheap and safe, the process flow is extremely short, the production process is green and environmental protection, and the product selectivity is high.

[0004] The difficulty of the two-step ethylene process mainly lies in the second step reaction, i.e. the aldol condensation reaction of methyl propionate and formaldehyde. The reaction is generally carried out in a fixed bed with basic oxides as catalysts and requires a high reaction temperature. Since the aldol condensation reaction produces water, which can hydrolyze with methyl propionate to generate propionic acid, the propionic acid is adsorbed on the basic active center of the catalyst, causing chemical deactivation of the catalyst and leading to a continuous decrease in activity. At the same time, decarboxylation and polycondensation reactions of formaldehyde may occur in the reactor, producing carbon deposition or large molecular organic matter attached to the catalyst bed, which also leads to a continuous decrease in catalytic activity. Under the influence of the above factors, the service life of the catalyst for the second step reaction is generally short, and periodic repeated decoking is required to restore the catalytic activity, which is a heavy workload. The most unfavorable factor is that for a single reactor, the MMA content in the product is continuously decreasing with the extension of the reaction time, and the unstable MMA composition brings great difficulty to the further rectification and purification in the subsequent separation section.

[0005] The prior art CN111574369 A and CN212532806 U provide a method for preparing methyl methacrylate by aldol condensation of methyl propionate and formaldehyde and a multi-stage reaction system. The method attempts to reduce the change range of the reaction product composition at the initial and final stages of the reaction by using multiple parallel reactors. The method uses time-division and section-by-section opening of the reactors. When the activity of the first-stage reactor decreases to a certain extent, the second-stage reactor is opened to compensate for the decrease in the MMA content in the product. Although this method has a certain effect on the stability of the MMA content in the product compared with a single reactor, it still has the problem of large fluctuation of the MMA content, which is very unfavorable for the stable operation of the subsequent methyl methacrylate rectification and purification section.

[0006] The prior art CN212549490 U provides an integrated reactor, which includes three relatively independent catalyst beds and has a compact and reasonable structure. However, the catalyst beds are still essentially connected in parallel, and the problem of large fluctuation of the MMA content in the product still exists, which brings inconvenience to the stable operation of the subsequent methyl methacrylate rectification and purification section.

[0007] The prior art CN102775302 B provides a method for preparing methyl methacrylate from methyl propionate and formaldehyde. The method effectively solves the problem of rapid deactivation of the catalyst by coupling a fluidized bed reactor and a catalyst regenerator, realizes the continuity of production, and reduces the fluctuation of the MMA product concentration. However, the fluidized bed reactor used in this method has many shortcomings, such as high strength requirement for the gas-phase condensation catalyst. During the continuous circulation process, the active components are easily pulverized and lost, and the economic efficiency is poor.

[0008] The prior art CN109232247 A provides a method for preparing methyl methacrylate by condensation of methyl acetate, methyl propionate and formaldehyde, which adopts a fluidized bed reactor, utilizes the internal circulation movement characteristics of the fluidized bed material in a fluidized state, introduces a small amount of oxygen to form a local oxygen-containing area at the lower part of the fluidized bed to periodically regenerate the catalytic bed material, can avoid serious side reactions under the presence of a large amount of oxygen and insufficient and uneven regeneration of the fluidized bed material, realizes the regeneration of the catalyst in the aldol condensation, maintains the long-term high activity of the catalyst, and solves the problems of easy carbon deposition and short service life of the catalyst; however, the method adopts the fluidized bed reactor, has a very high requirement on the strength of the gas phase condensation catalyst, and the loss and pulverization of the catalyst are relatively serious, and the production cost is relatively high.

[0009] The prior art CN113877560 A discloses a synthesis method of methyl acrylate, which adopts methyl acetate and formaldehyde as raw materials to generate methyl acrylate through a gas phase condensation reaction, and solves the problems of short service life of the catalyst in the traditional gas phase condensation reaction, easy carbon deposition and frequent regeneration through a catalyst reaction-regeneration coupling system.

[0010] The prior art CN113574046 A discloses a method for synthesizing methyl acrylate from acrylate and methanol acid catalysis, which adopts an esterification reaction, has a low efficiency, needs a large amount of washing water and has a high energy consumption.

[0011] The prior art CN115724741 A discloses a preparation process of tert-butyl (meth) acrylate, which adopts an acid-alkene addition method, and (meth) acrylate, a catalyst, a polymerization inhibitor, isobutene and an inert substance are jointly fed into a reaction kettle to generate tert-butyl (meth) acrylate, although the reaction conversion rate is improved and the production cost is reduced, but the method can only be produced intermittently and cannot realize continuous production.

[0012] Therefore, the utility model is provided. Utility model content

[0013] The utility model discloses a series reaction system for generating alkyl enoate compounds by gas phase condensation, solves the technical problem that the content of alkyl enoate compounds in the product fluctuates greatly, effectively reduces the content fluctuation of alkyl enoate compounds, improves the operation stability of the subsequent separation rectification section, and improves the single activity period of the catalyst.

[0014] The utility model provides a series reaction system for generating methyl methacrylate by aldol condensation, comprising n series reactors, wherein n is greater than or equal to 3.

[0015] The series reaction system is provided with a raw material gas main pipe for distributing raw material gas to each reactor for gas phase condensation reaction.

[0016] The raw material feeding pipe of each stage reactor is independently provided with a polymerization inhibitor injection system for injecting polymerization inhibitor into the reactor;

[0017] The series reaction system is provided with a reaction product main pipe, and the reaction product outlet of each stage reactor is connected to the feeding port of the next stage reactor and the reaction product main pipe;

[0018] The series reactor for carrying out the gas phase condensation reaction in the series reaction system is i stage, wherein 2≤i

[0019] Further, the series reaction system is further provided with a regeneration gas main pipe for distributing the regeneration gas into each stage reactor for in-situ catalyst regeneration.

[0020] Further, the series reaction system is further provided with a regeneration tail gas main pipe for collecting the regeneration tail gas of each stage reactor.

[0021] Further, the reactor comprises a vertical cylindrical adiabatic fixed bed type reactor.

[0022] Further, the adiabatic fixed bed type reactor comprises, from top to bottom, a feeding distribution zone, a reaction isothermal zone and a discharging collection zone.

[0023] Further, the feeding distribution zone is provided with an inlet distributor, a distribution tray, a support beam and a support grid, and the support grid and the distribution tray are filled with inert fillers.

[0024] Further, the reaction isothermal zone is filled with a gas phase condensation reaction catalyst.

[0025] Further, the discharging collection zone is provided with an outlet distribution tray, a support beam, a support grid and an outlet collector, and the support grid and the outlet distribution tray are filled with inert fillers.

[0026] Compared with the prior art, the utility model has at least the following beneficial effects:

[0027] The series reaction system for generating alkyl alkenyl ester compounds by gas phase condensation provided by the utility model is a reaction system composed of n-stage reactors (n≥3) in series, wherein the series reactors participating in the condensation reaction are i-stage (2≤i BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the specific embodiments of the utility model or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the utility model, and those skilled in the art can also obtain other drawings according to these drawings without any creative effort.

[0029] Figure 1 The schematic diagram of the multistage series reaction system provided for one embodiment of the utility model.

[0030] Figure: 1 - first raw material tank;2 - second raw material tank;3 - preheating furnace;4 - raw material gas main;5 - polymerization inhibitor;6 - first reactor;7 - second reactor;8 - third reactor;9 - i reactor;10 - n reactor;11 - reaction product main;12 - regeneration tail gas main;13 - regeneration gas main. DETAILED DESCRIPTION

[0031] The technical solution of this utility model will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0032] This invention provides a series reaction system for gas-phase condensation to generate alkyl acrylate compounds, comprising n-stage series reactors, wherein n≥3;

[0033] The series reaction system is equipped with a feed gas main pipe to distribute the feed gas to each stage reactor for gas-phase condensation reaction;

[0034] Meanwhile, each reactor has an independent polymerization inhibitor injection system on its feed pipes to inject polymerization inhibitors into the reactor.

[0035] The series reaction system is equipped with a reaction product main pipe, and the reaction product outlets of each reactor are connected to the feed inlet of the next reactor and the reaction product main pipe.

[0036] In a series reaction system, the reactors that carry out gas-phase condensation reactions are of stage i, where 2 ≤ i < n, and at least one reactor is in regeneration or standby mode.

[0037] During normal production, fresh feed gas from the feed gas main can enter each stage reactor according to a certain flow distribution ratio. Gas-phase condensation reactions occur in each stage reactor. The gas-phase condensation products of each stage reactor can be mixed with the fresh feed gas of the next stage reactor as feed for the next stage reactor. The gas-phase condensation products of the last stage reactor can enter the reaction product main and flow into the next rectification section. At the same time, the old and new reaction systems can be periodically operated, switched, and regenerated based on the analysis results of periodic sampling at the reaction product main. For example, when it is found that the content of alkyl acrylate compounds in the product has decreased to 80% to 85% of the initial value, and trace amounts of aldehyde compounds begin to appear in the sample, the old and new reaction systems can be switched and regenerated.

[0038] In summary, this series reaction system, with appropriate operating mode, can effectively ensure the basic stability of the content of alkyl acrylate compounds throughout the entire reaction cycle when using basic oxides as the catalyst for gas-phase condensation reaction. This creates excellent raw material conditions for further distillation and purification of alkyl acrylate compounds in the subsequent separation section, effectively improves the operational stability of the separation and distillation section, and increases the single-activity cycle of the catalyst to about 240 hours.

[0039] In this invention, each stage of the reactor can be equipped with a system for injecting a polymerization inhibitor solution on the raw material pipeline before entering the reactor. The polymerization inhibitor can be one or more of phenols, quinones, ethers, aromatic amines and nitro compounds, or other compounds that can inhibit polymerization. It is more preferably at least one of phenols, quinones and aromatic amines, and even more preferably phenols.

[0040] In a preferred embodiment, the multi-stage series reaction system of this invention may also be provided with a regeneration gas main pipe for distributing regeneration gas to each stage reactor for in-situ catalyst regeneration; at the same time, the multi-stage series reaction system may also be provided with a regeneration tail gas main pipe for collecting the regeneration tail gas from each stage reactor.

[0041] In multi-stage series reaction systems, see Figure 1 The solutions in the first raw material tank 1 and the second raw material tank 2 can be pumped into the preheating furnace 3. After being heated in the preheating furnace, they are mixed together and enter the reaction system. Inhibitor 5 is injected into the reaction system. Each stage reactor of this reaction system can have its own raw material gas feed pipeline system drawn from the raw material gas main pipe 4. Each stage reactor can have its own regeneration gas pipeline system drawn from the regeneration gas main pipe 13. The regeneration tail gas of each stage reactor can enter the regeneration tail gas main pipe 12. Each stage reactor has a corresponding next-stage reactor. The next-stage reactor of reactor number 1 (first reactor) is reactor number 2 (second reactor), the next-stage reactor of reactor number 2 is reactor number 3 (third reactor), and so on. The next-stage reactor of reactor number n-1 is reactor number n (nth reactor), and the next-stage reactor of reactor number n is reactor number 1. At the same time, the reaction product outlet of each stage reactor can be connected to two process flows: one is connected to the feed inlet of the next stage reactor, and the other is connected to the reaction product main pipe 11.

[0042] In this invention, a main valve and a main flow meter can be installed on the main feed gas pipeline; a heater, valve, nitrogen flow regulating valve and flow meter, and oxygen flow regulating valve and flow meter can be installed on the main regeneration gas pipeline to facilitate temperature and flow control during the regeneration of the deactivated catalyst; in addition, a separate shut-off valve, flow regulating valve and flow meter can be installed on the fresh feed gas inlet pipeline of each reactor to facilitate individual control and metering of the fresh feed gas entering each reactor.

[0043] In a preferred embodiment, each stage of the multi-stage series reaction system can be a vertical cylindrical adiabatic fixed-bed reactor with the same structure. The reactor is divided into three zones: the top can be a feed distribution zone, the middle can be a reaction isothermal zone, and the bottom can be a discharge collection zone.

[0044] In a preferred embodiment, the feed distribution area may be provided with an inlet distributor, a distribution tray, a support beam and a support grid, and inert ceramic balls or other fillers may be filled between the support grid and the distribution tray.

[0045] In this invention, the reaction isothermal zone can be filled with a gas-phase condensation reaction catalyst.

[0046] In a preferred embodiment, the discharge collection area may be provided with an outlet distribution tray, a support beam, a support grid, and an outlet collector, and inert ceramic balls or other fillers may be filled between the support grid and the outlet distribution tray.

[0047] A method for synthesizing alkyl acrylate compounds using the tandem reaction system described in any one of the above claims, comprising the following steps:

[0048] A feed gas consisting of a mixture of alkyl acids or esters and aldehydes is fed into a series reaction system. Simultaneously, a polymerization inhibitor is injected into the reactor, causing the feed gas to undergo a gas-phase condensation reaction in the series reaction system to obtain alkyl acrylates.

[0049] Aldehyde compounds can be one or more of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, pentanal, and C6 and above aldehydes (sources). For example, formaldehyde sources can be one or more of formaldehyde, trioxymethylene, paraoxymethylene, methyl acetal, polyoxymethylene, and other formaldehyde sources that can depolymerize or react to generate formaldehyde. Preferably, trioxymethylene is supplied in situ as a formaldehyde raw material for gas-phase condensation after depolymerization reaction, and more preferably, anhydrous formaldehyde is prepared in situ from methanol oxidative dehydrogenation.

[0050] The solvent for dissolving aldehyde compounds can be one or more of alcohols, alkanes, benzene rings, and other solvents that can dissolve formaldehyde sources. It is more preferably at least one of methanol, ethanol, propanol, butanol, and 1,3-propanediol, and even more preferably methanol.

[0051] Alkyl acids can be formic acid, acetic acid, propionic acid, butyric acid, valeric acid, and C6 or higher alkyl acids or isomers of the above alkyl acids.

[0052] Esters can be methyl esters, ethyl esters, propyl esters, butyl esters, pentyl esters, and C6 and above alkyl esters or isomers of the above esters.

[0053] Alkyl ester compounds are one or more of a series of compounds formed by any combination of the alkyl acids and esters described above. For example, acetate ester compounds are one or more of a series of compounds such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate, pentyl acetate, and C6 or higher alkyl acetate esters or isomers, preferably methyl acetate, ethyl acetate, or butyl acetate, and more preferably methyl acetate; propionate ester compounds are one or more of a series of compounds such as methyl propionate, ethyl propionate, propyl propionate, butyl propionate, and C6 or higher alkyl propionate esters or isomers, preferably methyl propionate, ethyl propionate, or butyl propionate, and more preferably methyl propionate.

[0054] Alkyl olefins can be methalic acid, ethylene acrylate, acrylic acid, butenoic acid, pentenoic acid, and C6 or higher alkyl olefins or isomers of the above alkyl olefins.

[0055] The alkyl acrylate compounds mentioned above are one or more of a series of compounds formed by any combination of the alkyl acrylates and the esters mentioned above. For example, acrylate compounds include methyl acrylate, ethyl acrylate, propyl acrylate, allyl propionate, pentyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, n-pentyl methacrylate, etc.

[0056] A typical method for synthesizing alkyl acrylate compounds using any of the above-described tandem reaction systems includes the following steps:

[0057] The first feed gas is fed into the first-stage reactor for gas-phase condensation reaction. The gas-phase condensation product obtained from the first-stage reactor is fed together with the second feed gas into the second-stage reactor for gas-phase condensation reaction. The gas-phase condensation product obtained from the second-stage reactor is fed together with the third feed gas into the third-stage reactor for gas-phase condensation reaction, and so on. The gas-phase condensation product obtained from the j-th stage reactor is fed together with the (j+1)-th feed gas into the (j+1)-th stage reactor for gas-phase condensation reaction, where 1 ≤ j < i, until the gas-phase condensation product obtained from the last stage reactor is fed into the reaction product header to obtain methyl methacrylate.

[0058] In normal production, the multi-stage series reaction system has i-stage series reactors (2≤i<n) for gas-phase condensation reaction to synthesize methyl methacrylate. Each reactor is in series. Metered fresh feed gas enters from reactor j as the feed for the first-stage reactor. The gas-phase condensation product of reactor j is mixed with the separately metered fresh feed gas of its next stage reactor (j+1; if j+1 is greater than n, the reactor number here automatically becomes 1, the same below) and used as the feed for reactor j+1, i.e., the second-stage reactor. The gas-phase condensation product of reactor j+1 is mixed with the separately metered fresh feed gas of its next stage reactor (j+2) and used as the feed for reactor j+2, i.e., the third-stage reactor. And so on, the multi-stage series reaction system consisting of reactors j, j+1, j+2... performs gas-phase condensation reaction to synthesize methyl methacrylate. The gas-phase condensation product of the last stage reactor enters the reaction product header.

[0059] During the production process, the temperature and pressure of each stage reactor in the multi-stage series reaction system are controlled as follows: the first stage reactor is not lower than the second stage reactor, the second stage reactor is not lower than the third stage reactor, and the j-th stage reactor is not lower than the (j+1)-th stage reactor (where 1≤j<i<n).

[0060] The method for synthesizing alkyl acrylate compounds using any of the above-described tandem reaction systems further includes the step of periodically switching between the old and new reaction systems:

[0061] During the operation of the i-th stage series reactor, when the periodic switching criteria between the old and new reaction systems are met, the first-stage reactor is removed from the original reaction system and regenerated in situ. The second-stage reactor in the original reaction system is used as the first-stage reactor in the new reaction system, the third-stage reactor in the original reaction system is used as the second-stage reactor in the new reaction system, and so on. The j-th stage reactor in the original reaction system is used as the (j-1)-th stage reactor in the new reaction system, where 2≤j≤i. The next stage reactor after the i-th stage reactor in the original reaction system is used as the i-th stage reactor in the new reaction system.

[0062] Specifically, the operation and switching of the old and new reaction systems in a multi-stage series reaction system can be governed by the following rules: During the operation of the i-th stage series reactor, when the switching criteria for the old and new reaction systems are met, the first-stage reactor, with the largest fresh feed gas flow and highest reaction temperature, exhibits the greatest activity decrease among all operating i-th reactors. Therefore, the first-stage reactor needs to be removed from the original reaction system and regenerated in situ. The second-stage reactor of the original reaction system is then used as the first-stage reactor of the new reaction system, and adjustments are made according to the process conditions such as temperature, pressure, and feed gas flow of the first-stage reactor in the original reaction system. The original third-stage reactor is used as the second-stage reactor of the new reaction system, and its process conditions, such as temperature, pressure, and feed quantity, are adjusted according to those of the original second-stage reactor. Similarly, the original j-th stage reactor is used as the (j-1)-th stage reactor of the new reaction system (2≤j≤i), and its process conditions, such as temperature, pressure, and feed quantity, are adjusted according to those of the original (j-1)-th stage reactor. The next stage reactor after the original i-th stage reactor is used as the i-th stage reactor of the new reaction system, and its process conditions, such as temperature, pressure, and feed quantity, are controlled and adjusted according to those of the original i-th stage reactor.

[0063] The criteria for switching between the old and new reaction systems are: when periodically sampling and analyzing the reaction product header, the content of alkyl acrylate compounds is found to have decreased to 80%-85% of the initial value, and trace amounts of aldehyde compounds begin to appear in the sample.

[0064] Example 1

[0065] A tandem reaction system for gas-phase condensation to produce alkyl acrylate compounds, see [link to tandem reaction system]. Figure 1 , including n-stage reactors in series, where n≥3;

[0066] The series reaction system is equipped with a main feed gas pipe 4. Each stage reactor has its own feed gas pipeline system led out from the main feed gas pipe 4, thereby distributing the feed gas to each stage reactor for gas phase condensation reaction.

[0067] Meanwhile, each reactor has an independent polymerization inhibitor injection system on its feed pipes to inject polymerization inhibitors into the reactor.

[0068] The series reaction system is equipped with a regeneration gas main pipe 13. Each stage reactor has its own regeneration gas pipeline system led out from the regeneration gas main pipe 13, thereby distributing the regeneration gas to each stage reactor for in-situ catalyst regeneration.

[0069] Furthermore, the series reaction system is equipped with a regeneration tail gas main pipe 12 for collecting the regeneration tail gas from each stage reactor;

[0070] Each reactor level has a corresponding next-level reactor. The next-level reactor of reactor number 1 (first reactor) is reactor number 2 (second reactor), the next-level reactor of reactor number 2 is reactor number 3 (third reactor), and so on. The next-level reactor of reactor number n-1 is reactor number n (nth reactor), and the next-level reactor of reactor number n is reactor number 1.

[0071] The series reaction system is equipped with a reaction product manifold 11, and the reaction product outlets of each reactor are connected to the feed inlet of the next reactor and the reaction product manifold 11.

[0072] All reactors at each stage are vertical cylindrical adiabatic fixed-bed reactors with the same structure. They are divided into three zones: the top is the feed distribution zone, the middle is the reaction isotherm zone, and the bottom is the discharge collection zone.

[0073] The feed distribution area is equipped with an inlet distributor, a distribution tray, a support beam, and a support grid. Inert filler is placed between the support grid and the distribution tray.

[0074] A gas-phase condensation reaction catalyst is packed in the reaction isotherm zone;

[0075] The discharge collection area is equipped with an outlet distribution tray, a support beam, a support grid, and an outlet collector. Inert filler is installed between the support grid and the outlet distribution tray.

[0076] In this embodiment, the series reactors that carry out gas-phase condensation reactions in the series reaction system are stage i, where 2≤i<n, and there is at least one reactor in the regeneration or standby state.

[0077] Experimental Example 1

[0078] The method for synthesizing methyl acrylate using the tandem reaction system of Example 1 includes the following steps:

[0079] [1] Weigh 2.5 kg of trioxymethylene and dissolve it in 10 kg of methanol solvent. After stirring evenly, a 20% mass fraction of trioxymethylene methanol solution is formed. Add the above trioxymethylene methanol solution to the first raw material tank.

[0080] [2] Weigh 10 kg of high-purity methyl propionate (≥99.9 wt%) and add it to the second raw material tank;

[0081] [3] The solution in the first raw material tank is pumped into the preheating furnace, and the flow rate here is controlled to be 100g / h;

[0082] [4] The solution in the second raw material tank is pumped into the preheating furnace, and the flow rate here is controlled at 245g / h;

[0083] [5] The temperature of the preheating furnace is controlled at 150℃~300℃. After the raw material solution is heated, it is mixed together and enters the reaction system. At this time, the total flow rate of fresh raw material is 345g / h.

[0084] [6] The flow distribution ratio of fresh raw materials entering reactor No. 1 and reactor No. 2 is set to 7:3. That is, the flow rate of fresh raw materials entering reactor No. 1 is controlled at 240 g / h by regulating valve and flow meter. The temperature of reactor No. 1 is controlled at 370℃ and the pressure is controlled at 0.25 MPa. Methyl acetate and formaldehyde undergo gas-phase condensation reaction in reactor No. 1 to generate methyl acrylate. All reaction products flow into reactor No. 2 to continue to participate in the reaction.

[0085] [7] The flow rate of fresh raw material entering reactor No. 2 is controlled at 105 g / h by regulating valve and flow meter. At the same time, it is mixed with all the reaction products of reactor No. 1 and used as feed for reactor No. 2. The temperature of reactor No. 2 is controlled at 360℃ and the pressure is controlled at 0.2 MPa. Methyl acetate and formaldehyde continue to undergo gas-phase condensation reaction in reactor No. 2 to produce methyl acrylate. All reaction products flow into the reaction product manifold and are sent to the next distillation section.

[0086] 【8】At this time, the status of each reactor in the reaction system is as follows: Reactor No. 1 is the first-stage reactor in operation, Reactor No. 2 is the second-stage reactor in operation, the product of the first-stage reactor enters the second-stage reactor in series, and the product of the second-stage reactor enters the reaction product header; Reactor No. 3 is in standby status.

[0087] [9] After running for about 240 hours, when taking samples from the reaction product main pipe for periodic analysis, it will be found that the methyl acrylate content has dropped to 80% to 85% of the initial value, and trace amounts of formaldehyde will begin to appear in the sample. At this time, it is necessary to switch the old and new reaction systems, cut off reactor No. 1, and put reactor No. 3 into operation.

[0088]

[10] Reactor No. 1, as the first-stage reactor, has the highest reaction temperature and processes the largest amount of fresh raw materials, resulting in the greatest decrease in its activity. Therefore, reactor No. 1 needs to be isolated and prepared for regeneration. At this time, reactor No. 2 will serve as the first-stage reactor of the new reaction system and will be adjusted according to the process conditions of the original first-stage reactor: the fresh raw material flow rate will be increased from 105 g / h to 240 g / h, the reaction temperature will be increased from 360℃ to 370℃, and the reaction pressure will be increased from 0.2 MPa to 0.25 MPa. The newly added reactor No. 3 will serve as the second-stage reactor of the new reaction system and will be controlled according to the process conditions of the original second-stage reactor: the fresh raw material flow rate will be 105 g / h, the reaction temperature will be 360℃, and the reaction pressure will be 0.2 MPa.

[0089]

[11] At this time, the status of each reactor in the new reaction system after the switch is as follows: Reactor No. 2 is the first stage reactor in the new reaction system, Reactor No. 3 is the second stage reactor in the new reaction system, the product of the first stage reactor enters the second stage reactor in series, and the product of the second stage reactor enters the reaction product header; Reactor No. 1 is in the preparation for regeneration.

[0090]

[12] In-situ regeneration of reactor No. 1 was carried out. The regeneration gas was a certain proportion of nitrogen and air. The reactor temperature was controlled at about 400℃. After the temperature stabilized, air was introduced. The total feed of air and nitrogen was controlled at 200L / h. The air volume was gradually increased until the maximum air volume was 50L / h. The temperature of the reactor bed was controlled not to exceed 500℃ throughout the regeneration process. When the temperature of the upper and lower bed of the reactor did not change and the tail gas analysis confirmed that there was no oxygen consumption, the regeneration was stopped and reactor No. 1 was cooled down for standby.

[0091]

[13] After running for about 240 hours again, when taking samples from the reaction product header for analysis, it will be found that the methyl acrylate content has dropped to 80% to 85% of the initial value, and trace amounts of formaldehyde will begin to appear in the sample. At this time, it is necessary to switch the old and new reaction systems again, cut off reactor number 2, and put reactor number 1 into use.

[0092]

[14] Reactor No. 2, as the first-stage reactor, has the highest reaction temperature and processes the largest amount of fresh raw materials, resulting in the greatest decrease in its activity. Therefore, reactor No. 2 needs to be isolated and prepared for regeneration. At this time, reactor No. 3 will serve as the first-stage reactor of the new reaction system, and its process conditions will be adjusted according to those of the original first-stage reactor: the fresh raw material flow rate will be increased from 105 g / h to 240 g / h, the reaction temperature will be increased from 360℃ to 370℃, and the reaction pressure will be increased from 0.2 MPa to 0.25 MPa. Reactor No. 1 will serve as the second-stage reactor of the new reaction system, and its process conditions will be controlled according to those of the original second-stage reactor: the fresh raw material flow rate will be 105 g / h, the reaction temperature will be 360℃, and the reaction pressure will be 0.2 MPa.

[0093]

[15] At this time, the status of each reactor in the new reaction system after the switch is as follows: Reactor No. 3 is the first stage reactor in the new reaction system, Reactor No. 1 is the second stage reactor in the new reaction system, the product of the first stage reactor enters the second stage reactor in series, and the product of the second stage reactor enters the reaction product header; Reactor No. 2 is in the preparation for regeneration.

[0094]

[16] In-situ regeneration of reactor No. 2 was carried out. The regeneration gas was a certain proportion of nitrogen and air. The reactor temperature was controlled at about 400℃. After the temperature stabilized, air was introduced. The total feed of air and nitrogen was controlled at 200L / h. The air volume was gradually increased until the maximum air volume was 50L / h. The temperature of the reactor bed was controlled not to exceed 500℃ throughout the regeneration process. When the temperature of the upper and lower bed of the reactor did not change and the tail gas analysis confirmed that there was no oxygen consumption, the regeneration was stopped and reactor No. 2 was cooled down for standby.

[0095]

[17] After running for about 240 hours again, when taking samples from the reaction product main pipe for periodic analysis, it will be found that the methyl acrylate content has dropped to 80% to 85% of the initial value, and trace amounts of formaldehyde will begin to appear in the sample. At this time, it is necessary to switch the old and new reaction systems again, cut off reactor No. 3, and put reactor No. 2 into use.

[0096]

[18] Reactor No. 3, as the first-stage reactor, has the highest reaction temperature and processes the largest amount of fresh raw materials, resulting in the greatest decrease in its activity. Therefore, reactor No. 3 needs to be isolated and prepared for regeneration. At this time, reactor No. 1 will be used as the first-stage reactor of the new reaction system, and the process conditions of the original first-stage reactor will be adjusted: the fresh raw material flow rate will be increased from 105 g / h to 240 g / h, the reaction temperature will be increased from 360℃ to 370℃, and the reaction pressure will be increased from 0.2 MPa to 0.25 MPa. Reactor No. 2 will be used as the second-stage reactor of the new reaction system, and the process conditions of the original second-stage reactor will be controlled: the fresh raw material flow rate will be 105 g / h, the reaction temperature will be 360℃, and the reaction pressure will be 0.2 MPa.

[0097]

[19] At this time, the status of each reactor in the new reaction system after the switch is as follows: Reactor No. 1 is the first stage reactor in the new reaction system, Reactor No. 2 is the second stage reactor in the new reaction system, the product of the first stage reactor enters the second stage reactor in series, and the product of the second stage reactor enters the reaction product header; Reactor No. 3 is in the preparation for regeneration.

[0098]

[20] In-situ regeneration of reactor No. 3 was carried out. The regeneration gas was a certain proportion of nitrogen and air. The reactor temperature was controlled at about 400℃. After the temperature stabilized, air was introduced. The total feed of air and nitrogen was controlled at 200L / h. The air volume was gradually increased until the maximum air volume was 50L / h. The temperature of the reactor bed was controlled not to exceed 500℃ throughout the regeneration process. When the temperature of the upper and lower bed of the reactor did not change and the tail gas analysis confirmed that there was no oxygen consumption, the regeneration was stopped and reactor No. 3 was cooled down for standby.

[0099]

[21] At this point, the state of the two-stage series reaction system is completely consistent with the state in [8]. The subsequent reaction system can be cycled and regenerated according to the steps determined from [8] to

[20] .

[0100] The product composition of the two-stage tandem reaction system is shown in Table 1.

[0101] Experimental Example 2

[0102] The difference from Experimental Example 1 is that methyl acetate is replaced with methyl propionate, the flow rate of the first raw material is controlled at 100 g / h, the flow rate of the second raw material is controlled at 176 g / h, the flow rate of fresh raw material entering reactor No. 1 is 193 g / h, the flow rate of fresh raw material entering reactor No. 2 is 83 g / h, the temperature of reactor No. 1 is 350℃, the temperature of reactor No. 2 is 340℃, and other processes and operating conditions remain unchanged. Then, the reaction system needs to be switched after about 240 hours of operation.

[0103] The product composition of the two-stage series reaction system is shown in Table 1.

[0104] Experimental Example 3

[0105] The difference from Experimental Example 1 is that methyl acetate is replaced with methyl propionate, 20% trioxymethylene methanol solution is replaced with 50% butyraldehyde methanol solution, the first raw material flow rate is controlled at 100 g / h, the second raw material flow rate is controlled at 183 g / h, the fresh raw material flow rate entering reactor No. 1 is 198 g / h, the fresh raw material flow rate entering reactor No. 2 is 85 g / h, the temperature of reactor No. 1 is 360℃, the temperature of reactor No. 2 is 350℃, and other processes and operating conditions remain unchanged. Then, the reaction system needs to be switched after about 260 hours of operation.

[0106] The product composition of the two-stage series reaction system is shown in Table 1.

[0107] Table 1

[0108]

[0109] Test Example 4

[0110] The method for synthesizing methyl methacrylate (MMA) using the tandem reaction system of Example 1 includes the following steps:

[0111] [1] Weigh 2.5 kg of trioxymethylene and dissolve it in 10 kg of methanol solvent. After stirring evenly, a 20% mass fraction of trioxymethylene methanol solution is formed. Add the above trioxymethylene methanol solution to the first raw material tank.

[0112] [2] Weigh 10 kg of high-purity methyl propionate (≥99.9 wt%) and add it to the second raw material tank;

[0113] [3] The solution in the first raw material tank is pumped into the preheating furnace, and the flow rate here is controlled at 120g / h;

[0114] [4] The solution in the second raw material tank is pumped into the preheating furnace, and the flow rate here is controlled at 210g / h;

[0115] [5] The temperature of the preheating furnace is controlled at 150℃~300℃. After the raw material solution is heated, it is mixed together and enters the reaction system. At this time, the total flow rate of fresh raw material is 330g / h.

[0116] [6] The flow rate distribution ratio of fresh raw materials entering reactors No. 1, 2 and 3 is 5:3:2, that is, the flow rate of fresh raw materials entering reactor No. 1 is controlled at 165g / h by regulating valve and flow meter. The temperature of reactor No. 1 is controlled at 350℃ and the pressure is controlled at 0.25MPa. Methyl propionate and formaldehyde undergo gas-phase condensation reaction in reactor No. 1 to generate MMA. All reaction products flow into reactor No. 2 to continue to participate in the reaction.

[0117] [7] The flow rate of fresh raw material entering reactor No. 2 is controlled at 100 g / h by regulating valve and flow meter. At the same time, it is mixed with all the reaction products of reactor No. 1 and used as feed for reactor No. 2. The temperature of reactor No. 2 is controlled at 340℃ and the pressure is controlled at 0.2 MPa. Methyl propionate and formaldehyde continue to undergo gas-phase condensation reaction in reactor No. 2 to generate MMA. All reaction products flow into reactor No. 3 to continue to participate in the reaction.

[0118] [8] The flow rate of fresh raw material entering reactor No. 3 is controlled at 65 g / h by regulating valve and flow meter. At the same time, it is mixed with all the reaction products of reactor No. 2 and used as feed for reactor No. 3. The temperature of reactor No. 3 is controlled at 330℃ and the pressure is controlled at 0.15 MPa. Methyl propionate and formaldehyde continue to undergo gas-phase condensation reaction in reactor No. 3 to generate MMA. All reaction products flow into the reaction product manifold and are sent to the next distillation section.

[0119] 【9】At this time, the status of each reactor in the reaction system is as follows: Reactor No. 1 is the first stage reactor in operation, Reactor No. 2 is the second stage reactor in operation, Reactor No. 3 is the third stage reactor in operation, the product of the first stage reactor enters the second stage reactor in series, the product of the second stage reactor enters the third stage reactor in series, and the product of the third stage reactor enters the reaction product header; Reactor No. 4 is in standby state.

[0120]

[10] After running for about 240 hours, when taking samples from the reaction product main pipe for analysis at regular intervals, it will be found that the MMA content has dropped to 80% to 85% of the initial value, and trace amounts of formaldehyde will begin to appear in the sample. At this time, it is necessary to switch the old and new reaction systems, cut off reactor No. 1, and put reactor No. 4 into operation.

[0121]

[11] Reactor No. 1, as the first-stage reactor, has the highest reaction temperature and processes the largest amount of fresh feedstock, resulting in the greatest decrease in its activity. Therefore, reactor No. 1 needs to be isolated and prepared for regeneration. At this time, reactor No. 2 will serve as the first-stage reactor of the new reaction system, and its process conditions will be adjusted according to the original first-stage reactor: the fresh feedstock flow rate will be increased from 100 g / h to 165 g / h, the reaction temperature will be increased from 340℃ to 350℃, and the reaction pressure will be increased from 0.2 MPa to 0.25 MPa. At this time, reactor No. 3... The reactor will serve as the second-stage reactor in the new reaction system, and will be adjusted according to the process conditions of the original second-stage reactor: the fresh feed flow rate will be increased from 65 g / h to 100 g / h, the reaction temperature will be increased from 330℃ to 340℃, and the reaction pressure will be increased from 0.15 MPa to 0.2 MPa; the newly added reactor No. 4 will serve as the third-stage reactor in the new reaction system, and will be controlled according to the process conditions of the original third-stage reactor: the fresh feed flow rate will be 65 g / h, the reaction temperature will be 330℃, and the reaction pressure will be 0.15 MPa;

[0122]

[12] At this time, the states of each reactor in the new reaction system after the switch are as follows: Reactor No. 2 is the first stage reactor in the new reaction system, Reactor No. 3 is the second stage reactor in the new reaction system, Reactor No. 4 is the third stage reactor in the new reaction system. The products of the first stage reactor are connected in series to the second stage reactor, the products of the second stage reactor are connected in series to the third stage reactor, and the products of the third stage reactor are connected to the reaction product header. Reactor No. 1 is in the preparation for regeneration.

[0123]

[13] In-situ regeneration of reactor No. 1 was carried out. The regeneration gas was a certain proportion of nitrogen and air. The reactor temperature was controlled at about 400℃. After the temperature stabilized, air was introduced. The total feed of air and nitrogen was controlled at 200L / h. The air volume was gradually increased until the maximum air volume was 50L / h. The temperature of the reactor bed was controlled not to exceed 500℃ throughout the regeneration process. When the temperature of the upper and lower bed of the reactor did not change and the tail gas analysis confirmed that there was no oxygen consumption, the regeneration was stopped and reactor No. 1 was cooled down for standby.

[0124]

[14] After running for about 240 hours again, when taking samples from the reaction product header for analysis, it will be found that the MMA content has dropped to 80% to 85% of the initial value, and trace amounts of formaldehyde will begin to appear in the sample. At this time, it is necessary to switch the old and new reaction systems again, cut off reactor number 2, and put reactor number 1 into use.

[0125]

[15] Reactor No. 2, as the first-stage reactor, has the highest reaction temperature and processes the largest amount of fresh feedstock, resulting in the greatest decrease in its activity. Therefore, reactor No. 2 needs to be isolated and prepared for regeneration. At this time, reactor No. 3 will serve as the first-stage reactor of the new reaction system, and its process conditions will be adjusted according to the original first-stage reactor: the fresh feedstock flow rate will be increased from 100 g / h to 165 g / h, the reaction temperature will be increased from 340℃ to 350℃, and the reaction pressure will be increased from 0.2 MPa to 0.25 MPa. At this time, reactor No. 4... The reactor will serve as the second-stage reactor in the new reaction system, and will be adjusted according to the process conditions of the original second-stage reactor: the fresh feed flow rate will be increased from 65 g / h to 100 g / h, the reaction temperature will be increased from 330℃ to 340℃, and the reaction pressure will be increased from 0.15 MPa to 0.2 MPa; the newly added reactor No. 1 will serve as the third-stage reactor in the new reaction system, and will be controlled according to the process conditions of the original third-stage reactor: the fresh feed flow rate will be 65 g / h, the reaction temperature will be 330℃, and the reaction pressure will be 0.15 MPa;

[0126]

[16] At this time, the status of each reactor in the new reaction system after switching is as follows: Reactor No. 3 is the first stage reactor in the new reaction system, Reactor No. 4 is the second stage reactor in the new reaction system, Reactor No. 1 is the third stage reactor in the new reaction system. The products of the first stage reactor are connected in series to the second stage reactor, the products of the second stage reactor are connected in series to the third stage reactor, and the products of the third stage reactor are connected to the reaction product header. Reactor No. 2 is in the preparation for regeneration.

[0127]

[17] In-situ regeneration of reactor No. 2 was carried out. The regeneration gas was a certain proportion of nitrogen and air. The reactor temperature was controlled at about 400℃. After the temperature stabilized, air was introduced. The total feed of air and nitrogen was controlled at 200L / h. The air volume was gradually increased until the maximum air volume was 50L / h. The temperature of the reactor bed was controlled not to exceed 500℃ throughout the regeneration process. When the temperature of the upper and lower bed of the reactor did not change and the tail gas analysis confirmed that there was no oxygen consumption, the regeneration was stopped and reactor No. 2 was cooled down for standby.

[0128]

[18] After running for about 240 hours again, when taking samples from the reaction product header for analysis, it will be found that the MMA content has dropped to 80% to 85% of the initial value, and trace amounts of formaldehyde will begin to appear in the sample. At this time, it is necessary to switch the old and new reaction systems again, cut off reactor number 3, and put reactor number 2 into operation.

[0129]

[19] Reactor No. 3, as the first-stage reactor, has the highest reaction temperature and processes the largest amount of fresh feedstock, resulting in the greatest decrease in its activity. Therefore, reactor No. 3 needs to be isolated and prepared for regeneration. At this time, reactor No. 4 will serve as the first-stage reactor of the new reaction system, and its process conditions will be adjusted according to the original first-stage reactor: the fresh feedstock flow rate will be increased from 100 g / h to 165 g / h, the reaction temperature will be increased from 340℃ to 350℃, and the reaction pressure will be increased from 0.2 MPa to 0.25 MPa. At this time, reactor No. 1... The reactor will serve as the second-stage reactor in the new reaction system, and will be adjusted according to the process conditions of the original second-stage reactor: the fresh feed flow rate will be increased from 65 g / h to 100 g / h, the reaction temperature will be increased from 330℃ to 340℃, and the reaction pressure will be increased from 0.15 MPa to 0.2 MPa; the newly added reactor No. 2 will serve as the third-stage reactor in the new reaction system, and will be controlled according to the process conditions of the original third-stage reactor: the fresh feed flow rate will be 65 g / h, the reaction temperature will be 330℃, and the reaction pressure will be 0.15 MPa;

[0130]

[20] At this time, the status of each reactor in the new reaction system after switching is as follows: Reactor No. 4 is the first stage reactor in the new reaction system, Reactor No. 1 is the second stage reactor in the new reaction system, Reactor No. 2 is the third stage reactor in the new reaction system. The products of the first stage reactor are connected in series to the second stage reactor, the products of the second stage reactor are connected in series to the third stage reactor, and the products of the third stage reactor are connected to the reaction product header; Reactor No. 3 is in the preparation for regeneration.

[0131]

[21] Reactor No. 3 was regenerated in situ. The regeneration gas was a certain proportion of nitrogen and air. The reactor temperature was controlled at about 400℃. After the temperature stabilized, air was introduced. The total feed of air and nitrogen was controlled at 200L / h. The air volume was gradually increased until the maximum air volume was 50L / h. The temperature of the reactor bed was controlled not to exceed 500℃ throughout the regeneration process. When the temperature of the upper and lower bed of the reactor did not change and the tail gas analysis confirmed that there was no oxygen consumption, the regeneration was stopped and reactor No. 3 was cooled down for standby.

[0132]

[22] After running for about 240 hours again, when taking samples from the reaction product main pipe for periodic analysis, it will be found that the MMA content has dropped to 80% to 85% of the initial value, and trace amounts of formaldehyde will begin to appear in the sample. At this time, it is necessary to switch the old and new reaction systems again, cut off reactor No. 4, and put reactor No. 3 into use.

[0133]

[23] Reactor No. 4, as the first-stage reactor, has the highest reaction temperature and processes the largest amount of fresh feedstock, resulting in the greatest decrease in its activity. Therefore, reactor No. 4 needs to be isolated and prepared for regeneration. At this time, reactor No. 1 will serve as the first-stage reactor in the new reaction system, and its process conditions will be adjusted according to the original first-stage reactor: the fresh feedstock flow rate will be increased from 100 g / h to 165 g / h, the reaction temperature from 340℃ to 350℃, and the reaction pressure from 0.2 MPa to 0.25 MPa. At this time, reactor No. 2... The reactor will serve as the second-stage reactor in the new reaction system, and will be adjusted according to the process conditions of the original second-stage reactor: the fresh feed flow rate will be increased from 65 g / h to 100 g / h, the reaction temperature will be increased from 330℃ to 340℃, and the reaction pressure will be increased from 0.15 MPa to 0.2 MPa; the newly added reactor, number 3, will serve as the third-stage reactor in the new reaction system, and will be controlled according to the process conditions of the original third-stage reactor: the fresh feed flow rate will be 65 g / h, the reaction temperature will be 330℃, and the reaction pressure will be 0.15 MPa.

[0134]

[24] At this time, the states of each reactor in the new reaction system after the switch are as follows: Reactor No. 1 is the first stage reactor in the new reaction system, Reactor No. 2 is the second stage reactor in the new reaction system, Reactor No. 3 is the third stage reactor in the new reaction system. The products of the first stage reactor are connected in series to the second stage reactor, the products of the second stage reactor are connected in series to the third stage reactor, and the products of the third stage reactor are connected to the reaction product header; Reactor No. 4 is in the regeneration preparation state.

[0135]

[25] In-situ regeneration of reactor No. 4 was carried out. The regeneration gas was a certain proportion of nitrogen and air. The reactor temperature was controlled at about 400℃. After the temperature stabilized, air was introduced. The total feed of air and nitrogen was controlled at 200L / h. The air volume was gradually increased until the maximum air volume was 50L / h. The temperature of the reactor bed was controlled not to exceed 500℃ throughout the regeneration process. When the temperature of the upper and lower bed of the reactor did not change and the tail gas analysis confirmed that there was no oxygen consumption, the regeneration was stopped and reactor No. 4 was cooled down for standby.

[0136]

[26] At this point, the state of the three-stage series reaction system is completely consistent with the state of [9]. The subsequent reaction system can be cycled and regenerated according to the steps determined from [9] to

[25] .

[0137] The product composition of the three-stage tandem reaction system is shown in Table 2.

[0138] Experimental Example 5

[0139] The difference from Experimental Example 4 is that methyl propionate is replaced with methyl acetate, the flow rate of the first feedstock is controlled at 120 g / h, the flow rate of the second feedstock is controlled at 296 g / h, the flow rate of fresh feedstock entering reactor No. 1 is 208 g / h, the flow rate of fresh feedstock entering reactor No. 2 is 125 g / h, the flow rate of fresh feedstock entering reactor No. 3 is 83 g / h, the temperature of reactor No. 1 is 370℃, the temperature of reactor No. 2 is 360℃, and the temperature of reactor No. 3 is 350℃. Other processes and operating conditions remain unchanged. The reaction system needs to be switched after about 240 hours of operation.

[0140] The product composition of the three-stage series reaction system is shown in Table 2.

[0141] Experimental Example 6

[0142] The difference from Experimental Example 4 is that the 20% trioxymethylene methanol solution is replaced with a 50% butyraldehyde methanol solution. The flow rate of the first raw material is controlled at 130 g / h, the flow rate of the second raw material is controlled at 240 g / h, the flow rate of fresh raw material entering reactor No. 1 is 185 g / h, the flow rate of fresh raw material entering reactor No. 2 is 110 g / h, the flow rate of fresh raw material entering reactor No. 3 is 74 g / h, the temperature of reactor No. 1 is 360℃, the temperature of reactor No. 2 is 350℃, and the temperature of reactor No. 3 is 340℃. Other processes and operating conditions remain unchanged. The reaction system needs to be switched after about 260 hours of operation.

[0143] The product composition of the three-stage series reaction system is shown in Table 2.

[0144] Table 2

[0145]

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A tandem reaction system for gas-phase condensation to generate alkyl acrylate compounds, characterized in that, The series reaction system comprises n series reactors, wherein n≥3; The series reaction system is provided with a raw material gas header for distributing raw material gas into each reactor for gas phase condensation reaction; Each reactor is independently provided with a polymerization inhibitor injection system on the raw material feeding pipeline for injecting polymerization inhibitor into the reactor; The series reaction system is provided with a reaction product header, and the reaction product outlet of each reactor is connected to the feeding inlet of the next reactor and to the reaction product header; The series reaction system comprises i series reactors for gas phase condensation reaction, wherein 2≤i<n, and at least one reactor is in a regeneration or standby state.

2. The series reaction system according to claim 1, wherein The series reaction system is further provided with a regeneration gas header for distributing regeneration gas into each reactor for in-situ catalyst regeneration.

3. The series reaction system according to claim 2, wherein The series reaction system is further provided with a regeneration tail gas header for collecting the regeneration tail gas of each reactor.

4. The series reaction system according to any one of claims 1 to 3, characterized by, The reactor comprises a vertical cylindrical adiabatic fixed bed type reactor.

5. The series reaction system according to claim 4, wherein The adiabatic fixed bed type reactor comprises, from top to bottom, a feeding distribution zone, a reaction isothermal zone and a discharging collection zone.

6. The series reaction system according to claim 5, wherein The feeding distribution zone is provided with an inlet distributor, a distribution tray, a support beam and a support grid, and the support grid and the distribution tray are filled with inert fillers.

7. The series reaction system according to claim 5, wherein The reaction isothermal zone is filled with gas phase condensation reaction catalyst.

8. The series reaction system according to claim 5, wherein The discharging collection zone is provided with an outlet distribution tray, a support beam, a support grid and an outlet collector, and the support grid and the outlet distribution tray are filled with inert fillers.

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