Cooling end sections of tube bundle reactors for partial oxidation of methylacrolein

Abstract

The present invention relates generally to the cooling of a product stream produced by the partial oxidation of C3-C6 aldehydes in the tubes of a tube bundle reactor. The present invention relates in particular to an apparatus for cooling the product stream in the end portions of the tubes using particulate solid material located in the end portions. The present invention additionally relates to a method of cooling the product stream using the particulate solid material at a rate sufficient to ensure that auto-oxidation is inhibited when the feed stream exits the additional longitudinal portion.

Description

Technical Field

[0001] This invention generally relates to the preparation of methacrylic acid from methacrolein via partial oxidation in a tubular reactor. In particular, the invention relates to apparatus and methods for cooling the methacrylic acid and residual methacrolein after the partial oxidation step has been performed to suppress auto-oxidation and post-combustion or similar processes (especially other undesirable side reactions). The invention further relates to the products obtained by the above-described apparatus and methods (especially methacrylic acid and the downstream product methyl methacrylate), the polymerization of methyl methacrylate, and the use of these products in the preparation of polymers (especially polymethyl methacrylate). Background Technology

[0002] Methyl methacrylate (MMA) is a widely used chemical product, with a global production of millions of tons annually. Various production methods are known for producing MMA, as summarized in Krill, Offermanns, and Rühling (2019), Chem. Unserer Zeit, 53. One example of these methods is the so-called C4 process, in which isobutylene or tert-butanol is partially oxidized in the presence of a suitable catalyst to obtain methacrolein, which is then partially oxidized again in the presence of another suitable catalyst to obtain methacrylic acid. In an additional step, methacrylic acid can be esterified with methanol to obtain MMA.

[0003] Partial oxidation methods using tube bundle reactors are known in the art. A frequently challenging aspect of operating a tube bundle reactor is regulating the temperature of the feed stream before the partial oxidation step and the temperature of the product stream after the partial oxidation step. Several inventions have been disclosed to address this challenging objective, including the following:

[0004] The invention disclosed in DE 30 42 468 A1 aims to cool acrolein obtained by partial oxidation in a tube bundle reactor. This is achieved by dividing the tubes of the tube bundle reactor into an additional longitudinal section and a further longitudinal section, the latter being downstream of the former. The additional longitudinal section is filled with a solid catalyst, while the further longitudinal section is filled with a granulated solid material intended to intensely cool the acrolein prepared in the additional longitudinal section. An important aspect of this disclosure is that the temperatures of the additional longitudinal section and the further longitudinal section are independently regulated by a secondary cooling process using a cooling medium (preferably a molten salt mixture or a high-heat-resistant oil).

[0005] The relevant teachings are provided by DE 100 47 693 A1, which addresses the problem of extending catalyst lifetime in a tube-bundle reactor. The aforementioned document teaches the placement of granular solid material within the tubes, specifically in the inlet and outlet spaces. These inlet and outlet spaces are located just outside and adjacent to the ends of the tubes. However, DE 100 47 693 A1 does not address the issue of reducing negative impacts and damage to the reactor itself.

[0006] Another approach to regulating the temperature is disclosed in DE 198 06 810 A1, in which the application focuses on regulating the temperature of the feed stream before it flows into the tube. This is achieved by isolating the end of the tube on the gas inlet side from the gas itself, since the aforementioned end is typically a very hot part of the reactor, resulting in a hot feed stream.

[0007] Even under the aforementioned conditions, regulating the temperature of the feed and product streams in the tube bundle reactor remains challenging. This is important not only for productivity but also for the safe operation of the tube bundle reactor. Summary of the Invention

[0008] Purpose

[0009] The object of the present invention is to overcome at least partially the disadvantages encountered in the prior art.

[0010] Another object of the present invention is to provide an apparatus for cooling a partially oxidized product stream.

[0011] Another object of the present invention is to provide an apparatus for partial oxidation product streams that requires less downtime for maintenance.

[0012] Another object of the present invention is to provide an apparatus for a partial oxidation product stream with improved safety.

[0013] Another object of the present invention is to provide an apparatus for a partially oxidized product stream, which has improved productivity.

[0014] Another object of the present invention is to provide an apparatus for a partially oxidized product stream that can be used safely at higher temperatures.

[0015] Another object of the present invention is to provide an apparatus for a partially oxidized product stream that is safer to use and has increased productivity, even when using used or partially deactivated catalysts.

[0016] Another object of the present invention is to provide a method for cooling the product stream when the partially oxidized product stream is no longer in contact with the solid catalyst.

[0017] Another object of the present invention is to provide a method for cooling a partially oxidized product stream to suppress auto-oxidation.

[0018] Another object of the present invention is to provide a method for cooling a partially oxidized product stream to a temperature below the auto-oxidation temperature of the partially oxidized product stream.

[0019] Preferred embodiments of the present invention

[0020] The contribution to at least partially achieving one of the above objectives is made by the independent implementation. The dependent implementation provides a preferred implementation that contributes to at least partially achieving one of the stated objectives.

[0021] [1] A reactor assembly arranged in a fluid communication manner, comprising a first reactor for the partial oxidation of C3-C6 aldehydes (preferably acrolein, more preferably methacrolein), the first reactor comprising the following structures as reactor components:

[0022] a) First entrance;

[0023] b) The entrance space (volume) downstream of the first entrance;

[0024] c) The first metal plate downstream of the entrance space;

[0025] d) Another metal plate downstream of the first metal plate;

[0026] e) The outlet space downstream of the other metal plate;

[0027] f) The first exit downstream of the exit space;

[0028] g) A plurality of pipes having a pipe length, wherein each of the pipes

[0029] (i) Located between the entrance space and the exit space.

[0030] (ii) Includes an entry point.

[0031] (iii) Includes the export end.

[0032] (iv) Includes the outer surface,

[0033] (v) includes the inner surface.

[0034] (vi) includes an inner space defined by the inner surface of the tube;

[0035] And of which at least 50%, preferably at least 80%, and more preferably at least 90% of the tubes respectively

[0036] [I] includes a first longitudinal portion, wherein the first longitudinal portion is positioned within the first metal plate.

[0037] [II] includes an additional longitudinal portion, wherein the additional longitudinal portion

[0038] (a) Arranged downstream of the first longitudinal portion, and

[0039] (b) Contains a first solid catalyst.

[0040] [III] includes an additional longitudinal portion, wherein the additional longitudinal portion

[0041] A) Arranged downstream of the additional longitudinal section.

[0042] B) Positioned within the other metal plate.

[0043] C) Contains an inert granular solid material, wherein the granular solid material

[0044] (I) Adapted and arranged for heat dissipation,

[0045] (II) Adaptively modified and arranged to be gas-permeable;

[0046] h) A liquid cooling aid, wherein a portion of the outer surface of the tube is arranged and adaptively adjusted to contact the liquid cooling aid, wherein the portion is at least 50%, preferably at least 70%, more preferably at least 80%, and even more preferably at least 90% of the length of the additional longitudinal portion;

[0047] And among them,

[0048] The average thickness of any layer containing the granular solid material present in the outlet space, the inlet space, or both is less than 10%, preferably less than 5%, and more preferably less than 3% of the average length of the additional longitudinal portion.

[0049] [2] The reactor assembly according to embodiment [1], wherein at least one or all of the following features are applicable:

[0050] a) The mass percentage of the granular solid material present in the first longitudinal portion is less than 5% by weight, preferably less than 3% by weight, and more preferably less than 1% by weight, based on the total mass of the granular solid material contained in the tube;

[0051] b) The mass percentage of the first solid catalyst contained in the first longitudinal section is less than 5% by weight, preferably less than 3% by weight, and more preferably less than 1% by weight, based on the total mass of the first solid catalyst contained in the tube.

[0052] For implementation scheme [2], all possible combinations of features a and b are preferred aspects of the implementation scheme. These combinations are, for example, a; b; a, b.

[0053] [3] In any of the preceding embodiments of the reactor assembly, at least 30%, preferably at least 50%, more preferably at least 80%, and even more preferably at least 90% of the length of the additional longitudinal portion is embedded in the additional metal plate.

[0054] [4] In any of the preceding embodiments, at least 30%, preferably at least 50%, more preferably at least 80%, and even more preferably at least 90% of the length of the first longitudinal portion is embedded in the first metal plate.

[0055] [5] In the reactor assembly according to any of the foregoing embodiments, the additional longitudinal portion has a length that is at least twice, preferably at least ten times, and more preferably at least 30 times the length of the other longitudinal portion. In many cases, the length of the additional longitudinal portion does not exceed 100 times the length of the other longitudinal portion.

[0056] [6] In the reactor assembly according to any of the foregoing embodiments, the additional longitudinal portion has a length that is at least twice, preferably at least ten times, and more preferably at least 30 times the length of the first longitudinal portion. In many cases, the length of the additional longitudinal portion does not exceed 110 times the length of the first longitudinal portion.

[0057] [7] A reactor assembly according to any of the foregoing embodiments, wherein the additional longitudinal portion is in thermal contact with the additional metal plate.

[0058] [8] A reactor assembly according to any of the foregoing embodiments, wherein the additional metal plate is in thermal contact with the liquid cooling aid.

[0059] [9] A reactor assembly according to any of the foregoing embodiments, wherein at least one or all of the following features are applicable:

[0060] a) The mass percentage of the first solid catalyst contained in the additional longitudinal portion is greater than 50% by weight, preferably greater than 70% by weight and more preferably greater than 85% by weight, based on the total mass of the first solid catalyst contained in the tube;

[0061] b) The ratio of the mass of the first solid catalyst, which is contained in the additional longitudinal portion, to the mass of the granulated solid material is 1:x, where x is at least 10, preferably at least 100, and more preferably at least 500. Here, x represents the mass of the granulated solid material.

[0062] For the implementation scheme [9], all possible combinations of features a and b are preferred aspects of the implementation scheme. These combinations are, for example, a; b; a, b.

[0063]

[10] The reactor assembly according to any of the foregoing embodiments, wherein the granular solid material comprises one or more components selected from the group consisting of metals and metal oxides, preferably a mixture of at least two components selected from the group above.

[0064]

[11] The reactor assembly according to any of the foregoing embodiments, wherein the granular solid material is selected from aluminum, copper, steel, silicon dioxide, alumina, zirconium oxide, sandstone, granite or a combination of two or more of them, such as ceramics.

[0065]

[12] The reactor assembly according to any of the foregoing embodiments, wherein the granular solid material has at least one or all of the following physical properties:

[0066] a) Thermal conductivity in the range of 0.01 W / m / ℃ to 500 W / m / ℃, preferably in the range of 0.05 W / m / ℃ to 450 W / m / ℃, and more preferably in the range of 0.1 W / m / ℃ to 400 W / m / ℃;

[0067] b) at 20m 2 / m 3 up to 2000m 2 / m 3 Within a range, more preferably within 100m 2 / m 3 up to 1500m 2 / m 3 Within the range, and further preferably within 800m 2 / m 3 Up to 1200m 2 / m 3 Geometric specific surface area within the range;

[0068] c) Free volume in the range of 24% to 99%, preferably in the range of 30% to 99%, and even more preferably in the range of 35% to 99%; or

[0069] d) Particle size distribution in the range of 0.01 mm to 100 mm, preferably in the range of 0.05 mm to 50 mm, and more preferably in the range of 0.1 mm to 30 mm.

[0070] For implementation scheme

[12] , all possible combinations of features a to d are preferred aspects of the implementation scheme. These combinations are, for example, a; b; c; d; a,b; a,c; a,d; b,c; b,d; c,d; a,b,c; a,b,d; a,c,d; b,c,d; a,b,c,d.

[0071]

[13] In a reactor assembly according to any of the foregoing embodiments, at least one or all of the following properties are applicable to at least 50%, preferably at least 80%, and more preferably at least 95% of the tubes:

[0072] a) The length of the tube is in the range of 1000mm to 15000mm, preferably in the range of 2000mm to 9000mm, and more preferably in the range of 3000mm to 6000mm;

[0073] b) The diameter of the inner surface is in the range of 10 mm to 100 mm, preferably in the range of 12 mm to 50 mm, or more preferably in the range of 18 mm to 46 mm; or

[0074] c) The tubes are arranged parallel to each other.

[0075] For the implementation scheme

[13] , all possible combinations of features a to c are preferred aspects of the implementation scheme. These combinations are, for example, a; b; c; a, b; a, c; b, c; a, b, c.

[0076]

[14] The reactor assembly according to any of the foregoing embodiments, wherein the liquid cooling aid has a temperature in the range of 150°C to 420°C, preferably in the range of 200°C to 370°C, and more preferably in the range of 230°C to 360°C.

[0077]

[15] In the reactor assembly according to any of the foregoing embodiments, the first metal plate, the other metal plate, or both independently have a thickness in the range of 10 mm to 300 mm, preferably in the range of 15 mm to 180 mm, and more preferably in the range of 20 mm to 160 mm. In one aspect of this embodiment, the first longitudinal portion preferably has a length in the range of 0.5 to 4 times the thickness of the first metal plate, preferably in the range of 0.6 to 3.2 times, and more preferably in the range of 0.7 to 2.9 times. In another aspect of this embodiment, the other longitudinal portion preferably has a length in the range of 0.5 to 4 times the thickness of the other metal plate, preferably in the range of 0.6 to 3.2 times, and more preferably in the range of 0.7 to 2.9 times.

[0078]

[16] According to any of the preceding embodiments, the liquid cooling aid flows into the first reactor through at least one inlet opening and flows out of the first reactor through at least one outlet opening.

[0079]

[17] In a reactor assembly according to any of the foregoing embodiments, the first longitudinal portion, the additional longitudinal portion and the further longitudinal portion account for at least 50%, preferably at least 65%, more preferably at least 80% and even more preferably at least 90% of the tube length.

[0080]

[18] The reactor assembly according to any of the foregoing embodiments, wherein the first solid catalyst is selected from mixed metal oxides or a combination of at least two of them.

[0081]

[19] A reactor assembly according to any of the foregoing embodiments, wherein the reactor assembly further comprises a second reactor.

[0082] a. wherein the second reactor is located upstream of the first reactor;

[0083] b. wherein the second reactor comprises

[0084] i. Second entrance

[0085] ii. A second outlet in fluid communication with the first inlet of the first reactor.

[0086] iii. The second catalytic reaction zone located between the second inlet and the second outlet,

[0087] a.) wherein the second reaction zone contains a second solid catalyst.

[0088] b.) The second solid catalyst is arranged and adaptively adjusted to partially oxidize a gaseous composition having an aldehyde precursor content of at least 2 vol%, preferably at least 2.5 vol%, and more preferably at least 3 vol%, wherein the selectivity is at least 70%, preferably at least 75%, and more preferably at least 80%, based on the unsaturated hydrocarbon content.

[0089]

[20] The reactor assembly according to the aforementioned embodiment

[19] , wherein the aldehyde precursor is selected from isobutylene, methyl tert-butyl ether and tert-butanol, or a combination of at least two of them.

[0090]

[21] A reactor assembly according to any one of the aforementioned embodiments

[19] to

[20] , wherein the second solid catalyst is selected from mixed metal oxides or a combination of at least two of them.

[0091]

[22] A reactor assembly according to any of the foregoing embodiments, wherein the reactor assembly further comprises a third reactor.

[0092] a. wherein the third reactor is located downstream of the first reactor;

[0093] b. wherein the third reactor comprises

[0094] i. A third inlet in fluid communication with the first outlet of the first reactor.

[0095] ii. Third exit,

[0096] iii. A third catalytic zone located between the third inlet and the third outlet.

[0097] a.) wherein the third catalytic region comprises a third catalyst,

[0098] b.) The third catalyst is arranged and adaptively adjusted to esterify a composition, preferably a liquid composition, having at least 30% by volume, preferably at least 45% by volume, and more preferably at least 55% by volume of a C3-C6 carboxylic acid component into an alkyl ester, preferably an alkyl acrylate, more preferably an alkyl methacrylate, and further preferably methyl methacrylate.

[0099]

[23] According to the reactor assembly of the aforementioned embodiment

[22] , the third catalyst is selected from ion exchangers or Lewis acids, more preferably acidic ion exchange resins or acids, which are capable of catalyzing esterification, or a combination of at least two of them.

[0100]

[24] According to the aforementioned reactor assembly, the reactor assembly includes a gas cooler connected to the first outlet.

[0101]

[25] A method for preparing a product, wherein the product is preferably a polymer or an unsaturated alkyl carboxylic acid compound, more preferably an unsaturated alkyl carboxylic acid or an unsaturated alkyl ester, further preferably an alkyl acrylate, even more preferably an alkyl methacrylate, and particularly preferably methyl methacrylate, wherein the method comprises the following steps:

[0102] a) Provide a gaseous feed stream, wherein the feed stream contains C3-C6 aldehydes;

[0103] b) Partial oxidation of the C3-C6 aldehydes in the feed stream in the presence of a solid catalyst to obtain a first product stream comprising partially oxidized products, wherein the partial oxidation is carried out along an additional longitudinal portion, and

[0104] c) Cooling the first product stream along another longitudinal portion, preferably to below 350°C, more preferably below 340°C, even more preferably below 330°C, and even more preferably below 320°C, wherein

[0105] (i) The additional longitudinal portion comprises granular solid material.

[0106] (ii) The temperature of the product stream in the additional longitudinal section at a rate R p decline;

[0107] and,

[0108] in

[0109] R p Greater than the rate of temperature decrease R e The rate R e It is the rate in the case where the additional longitudinal portion does not contain the granulated solid material.

[0110]

[26] According to the method of implementation scheme

[25] , where R p It is R e It is at least 2 times, preferably at least 5 times, more preferably at least 10 times, and even more preferably at least 21 times.

[0111]

[27] According to the method of any one of embodiments

[25] to

[26] , wherein the rate R p The temperature range is from 0.1℃ / cm to 5℃ / cm, preferably from 0.2℃ / cm to 2.5℃ / cm, and more preferably from 0.6℃ / cm to 1.6℃ / cm.

[0112]

[28] According to any one of the embodiments

[25] to

[27] , the temperature of the first product stream leaving the other longitudinal portion is lower than the auto-oxidation temperature of the first product stream.

[0113]

[29] According to the method of any one of embodiments

[25] to

[28] , the temperature of the first product stream leaving the other longitudinal portion is in the range of >230°C to 360°C, preferably in the range of 270°C to 335°C, and more preferably in the range of 295°C to 320°C.

[0114]

[30] According to the method of any one of the embodiments

[25] to

[29] , the temperature of the first product stream entering the additional longitudinal portion is in the range of 250°C to 400°C, preferably in the range of 260°C to 390°C, and more preferably in the range of 280°C to 380°C.

[0115]

[31] According to the method of any one of the embodiments

[25] to

[30] , the temperature of the feed stream entering the first longitudinal section is in the range of 180°C to 300°C, preferably in the range of 200°C to 280°C, and more preferably in the range of 220°C to 260°C.

[0116]

[32] According to any one of the embodiments

[25] to

[31] , the pressure reduction between the inlet space and the outlet space is in the range of 100 mbar to 350 mbar, preferably in the range of 130 mbar to 300 mbar, and more preferably in the range of 150 mbar to 280 mbar.

[0117]

[33] According to the method of any one of embodiments

[25] to

[32] , the average velocity of the first product stream in the additional longitudinal portion is in the range of 0.5 m / s to 12 m / s, preferably in the range of 0.8 m / s to 11.5 m / s, and more preferably in the range of 1.0 m / s to 11 m / s.

[0118]

[34] According to any one of the embodiments

[25] to

[32] , the product stream leaving the first outlet is fed into a gas cooler, and the temperature of the product stream leaving the gas cooler is in the range of 160°C to 280°C, preferably in the range of 190°C to 270°C, and more preferably in the range of 200°C to 260°C.

[0119]

[35] According to the method of any one of embodiments

[25] to

[33] , the C3-C6 aldehyde is present in the first product stream in an amount ranging from 0.1% to 10%, preferably from 0.3% to 7%, more preferably from 0.5% to 5%, and even more preferably from 0.7% to 4%, based on the amount of C3-C6 aldehyde in the feed stream.

[0120]

[36] The method according to any one of the embodiments

[25] to

[35] , wherein the C3-C6 aldehyde is acrolein, preferably methacrolein.

[0121]

[37] The method according to any one of the embodiments

[25] to

[36] , wherein the product is methacrylic acid or methyl methacrylate.

[0122]

[38] The method according to any one of embodiments

[25] to

[37] , wherein the feed stream comprises

[0123] a) at least 2% by volume, preferably at least 2.5% by volume, and more preferably at least 3% by volume of unsaturated C3-C6 aldehydes, preferably methacrolein;

[0124] b) The volume percentage of water is at least twice, preferably at least three times, and more preferably at least four times, the volume percentage of C3-C6 aldehydes;

[0125] c) The volume percentage of oxygen is 2 to 3.5 times that of C3-C6 aldehydes, preferably 2.2 to 3.3 times, more preferably 2.4 to 3.2 times;

[0126] d) Less than 3% by volume, preferably less than 1.5% by volume, more preferably less than 1% by volume of unsaturated C3-C6 carboxylic acids, preferably methacrylic acid;

[0127] The sum of the volume percentages of the components of the feed stream is equal to 100% by volume.

[0128]

[39] According to the method of any one of embodiments

[25] to

[38] , wherein the first product stream further comprises the following components:

[0129] a) Water of no more than 10% by volume, preferably no more than 18% by volume, and more preferably no more than 20% by volume;

[0130] b) No more than 5% by volume, preferably no more than 7% by volume, and more preferably no more than 10% by volume of oxygen;

[0131] c) at least 0.5% by volume, preferably at least 1.0% by volume, more preferably at least 1.5% by volume, and even more preferably at least 1.8% by volume of unsaturated C3-C6 carboxylic acids, preferably methacrylic acid;

[0132] d) Acetic acid of not more than 2% by volume, preferably not more than 1.5% by volume, more preferably not more than 1.2% by volume, and even more preferably not more than 0.6% by volume;

[0133] e) no more than 0.9% by volume, preferably no more than 1% by volume, and more preferably no more than 1.1% by volume of (meth)acrylonitrile;

[0134] Wherein the sum of the volume percentages of the components of the first product stream is equal to 100 volumes.

[0135]

[40] According to the method of any one of the embodiments

[25] to

[39] , wherein the additional longitudinal portion and the other longitudinal portion are located in the tube.

[0136]

[41] According to the method of any one of the embodiments

[25] to

[40] , wherein the additional longitudinal portion is adjacent to the extra longitudinal portion.

[0137]

[42] According to any one of the embodiments

[25] to

[41] , the first product stream is subjected to an esterification reaction to obtain a product in the form of an unsaturated alkyl ester, preferably methyl methacrylate.

[0138]

[43] The method according to embodiment

[42] wherein the unsaturated alkyl ester is subjected to at least one purification step.

[0139]

[44] The method according to any one of embodiments

[42] and

[43] , wherein the unsaturated alkyl ester is subjected to a polymerization reaction to obtain a product in the form of a polymer, preferably polymethyl methacrylate.

[0140]

[45] The unsaturated alkyl esters that can be obtained by the methods according to embodiments

[42] to

[44] can be used for the preparation of polymers.

[0141]

[46] The polymer can be obtained by means of the method according to embodiment

[45] .

[0142]

[47] The polymer according to embodiment

[46] is used for articles selected from molded articles, molding materials, films, sheets, granules, composite materials, foams, fibers, lubricants, adhesives, thickeners, suspending agents, flocculants, resins, plastics, coatings, contact lenses, building materials, absorbent materials, pharmaceuticals, materials for controlled release of active substances, powders, or combinations of at least two of the above. Invention Details

[0144] The selection of preferred embodiments of the invention is discussed in more detail in this section.

[0145] First reactor

[0146] As is known to those skilled in the art, tube bundle reactors are particularly suitable for the partial oxidation of a gaseous feed stream over a catalyst to obtain a product stream. Such reactors are commercially available, for example, from Deggendorfer Werft, Germany, or from IHI Corporation, Japan. Due to their widespread use and commercial availability, operating tube bundle reactors is generally well within the knowledge of those skilled in the art.

[0147] In the context of this invention, the term "feed stream" refers to a gaseous mixture of compounds and single chemical elements prior to the commencement of partial oxidation, preferably prior to contact with the catalyst.

[0148] In the context of this invention, the term "product stream" or similar expression should be understood to mean that the feed stream has been contacted with the catalyst and that partial oxidation of at least one of the components contained in the feed stream has begun.

[0149] A first aspect of the invention is a reactor assembly comprising a first reactor for partially oxidizing a feed stream into a product stream. The first reactor is a commercially available tube-bundle reactor that has been modified to cool the product stream to inhibit further oxidation (so-called "auto-oxidation").

[0150] Autooxidation is an incomplete and uncontrolled oxidation process that produces carbon residues that tend to clog the reactor. As a result, the reactor's yield decreases. Autooxidation is strongly dependent on pressure and temperature, and even more so on the concentration of the major component in the product stream (e.g., (meth)acrolein) that is readily autooxidized. Additionally, O2 concentration and reactant residence time also affect autooxidation. Autooxidation of (meth)acrolein has been observed at concentrations above 3 vol% at temperatures of 240 °C or higher. At 1 vol% concentrations, autooxidation of (meth)acrolein has been observed at temperatures of 315 °C or higher.

[0151] In another aspect of the invention, the first reactor includes a first inlet that allows a feed stream to flow into the first reactor and a first outlet that allows a product stream to flow out of the first reactor.

[0152] According to another aspect of the invention, a plurality of tubes are located between the first inlet and the first outlet, wherein each tube includes an inlet end allowing the feed flow to enter the tube and an outlet end allowing the product flow to exit the tube. In another aspect of the invention, each tube has an outer surface and an inner surface defining an inner space within the tube.

[0153] According to another aspect of the invention, at least a portion of the outer surface of the tube is immersed in and in thermal contact with the liquid cooling agent. The expression "thermally in contact" should be understood to mean that heat can flow between any number of components that are in thermal contact with each other. Preferably, any number of components that are in thermal contact with each other also touch each other.

[0154] In one aspect of the invention, at least 50% of the tube further comprises an additional longitudinal portion and a further longitudinal portion, wherein the latter is downstream of the former. Preferably, the interior space of the additional longitudinal portion is at least partially filled with a first solid catalyst suitable for oxidizing the feed stream into the product stream. Particularly preferably, the interior space of the further longitudinal portion is at least partially filled with an inert granular solid material arranged and adaptively modified for heat dissipation. Also preferably, the interior space of the additional longitudinal portion is at least partially filled with a mixture of the first solid catalyst and the granular solid material.

[0155] The term "inert" should be understood to mean that the presence of the granular solid material does not cause any measurable change in the composition of the feed stream or the product stream.

[0156] The term "heat dissipation" should mean that the product stream is in thermal contact with the granulated solid material, and that this causes the product stream to be cooled more quickly compared to a situation where the product stream is not in contact with the granulated solid material. For example, the temperature of the product stream at the center of the additional longitudinal portion is higher than the temperature of the product stream flowing along the sidewall of the additional longitudinal portion. The granulated solid material dissipates heat by transferring heat from the center of the additional longitudinal portion to the sidewall of the additional longitudinal portion.

[0157] In another aspect of the invention, preferably at least 50% of the tube comprises a first longitudinal portion. Further preferably, the first longitudinal portion is upstream of the additional longitudinal portion. Although the first longitudinal portion may be at least partially filled with the first solid catalyst, it is more preferable that the first longitudinal portion does not contain any first solid catalyst. Although the first longitudinal portion may be at least partially filled with the granulated solid material, it is more preferable that the first longitudinal portion does not contain any granulated solid material. Particularly preferably, the first longitudinal portion does not contain any first solid catalyst or any granulated solid material.

[0158] In the context of this invention, the longitudinal portion includes two endpoints. These two endpoints are characterized as locations where the change in the ratio of the mass of the first solid catalyst to the mass of the particulate solid material exceeds 30%. It should be noted that two adjacent longitudinal portions will share one endpoint. For example, consider a tube having a first longitudinal portion, the additional longitudinal portion, and the further longitudinal portion. Furthermore, the first longitudinal portion and the additional longitudinal portion are adjacent to each other, while the additional longitudinal portion and the further longitudinal portion are adjacent to each other. Then, consider the following two exemplary configurations:

[0159] i. The first longitudinal portion is empty, the additional longitudinal portion is filled only with the first solid catalyst, and the other longitudinal portion is filled only with the granulated solid material;

[0160] ii. The first longitudinal portion is filled only with the granulated solid material, the additional longitudinal portion is filled with a mixture of the first solid catalyst and the granulated solid material, and the other longitudinal portion is filled only with the granulated solid material.

[0161] In both settings, it is clear that the ratio of the mass of the first solid catalyst to the mass of the particulate solid material varies by more than 20% between two adjacent longitudinal portions.

[0162] In one aspect of the invention, the first reactor comprises a first metal plate. Preferably, the first metal plate is made of stainless steel or carbon steel. In another aspect of the invention, the first reactor comprises a further metal plate. Preferably, the further metal plate is made of stainless steel or carbon steel.

[0163] According to one aspect of the invention, an additional metal plate is arranged and adaptively adjusted to allow the additional longitudinal portion to be positioned within the additional metal plate. In this aspect, it is preferable that the additional longitudinal portion extends through the additional metal plate: for example, the length of the additional longitudinal portion is greater than the thickness of the additional metal plate; for example, the additional longitudinal portion extends through the additional metal plate into the outlet space. However, it is more preferable that the outlet end of the tube is flush with the surface of the additional metal plate (further preferably not touching the surface of the additional metal plate containing the liquid cooling aid). The preferred embodiments disclosed in this paragraph, with appropriate modifications, are also preferred for aspects of the invention in which the first metal plate is arranged and adaptively adjusted to allow the first longitudinal portion to be positioned within the first metal plate. It is also preferable that the metal plate is made of stainless steel or carbon steel.

[0164] In another aspect of the invention, the first reactor further includes two spaces associated with the first inlet and the first outlet: the inlet end of the tube and the first inlet define an inlet space, while the outlet end of the tube and the first outlet define an outlet space. According to one aspect of the invention, the first inlet, the inlet space, the tube, the outlet space, and the first outlet are in fluid communication with each other.

[0165] The term "fluid" should be understood to mean any element, compound, or physical substance in a gaseous or liquid thermodynamic phase. A "fluid" can be at least one of liquid, gas, vapor, supercritical fluid, or any other fluid. For example, water vapor, a gaseous feed stream, and salt dissolved in water are considered instances of "fluid."

[0166] The expression "fluid communication" should be understood to mean that fluid can flow from a first component of the first apparatus to any other component or additional device of the first apparatus that is "fluidly communication" with the first component of the first apparatus. For example, a first partial oxidation reactor and a third esterification reactor are "fluidly communication" as long as fluid can flow from the first reactor to the third reactor, or vice versa. For example, the first partial oxidation reactor contains a space between the tubes, wherein this space is filled with a liquid cooling aid. This space is not "fluidly communication" with, for example, the first outlet of the first reactor, because fluid cannot flow from this space to the first outlet.

[0167] It should be noted that the "fluidly connected" components do not imply that the components must be adjacent to each other. For example, between the first oxidation reactor and the third esterification reactor, which are in "fluid communication," there may be means for cooling and purifying the product stream before it flows into the third reactor.

[0168] Tube

[0169] In the context of this invention, the term "tube" refers to any number of streamlines of a device capable of guiding fluid. Preferably, the "tube" has openings at both ends. It is also preferred that the "tube" has a closed internal space through which fluid can flow, and the internal space may be filled with a material such as a solid catalyst.

[0170] The components of a "pipe" are not required to be adjacent to each other; only that they are required to be in fluid communication. For example, a "pipe" can refer to two pipes and an additional metal plate placed between the pipes, wherein the additional metal plate has a hollow structure extending through it. Fluid can thus flow through one pipe, via the hollow structure in the additional metal plate, into the second pipe.

[0171] Regarding several aspects of the invention related to the tube, the following should be noted: Although there is no particular limitation on the shape of the tube, a straight tube is preferred. It is also preferred that the tube has a circular cross-section. It is further preferred that the additional longitudinal portion and the additional longitudinal portion are adjacent to each other. It is even more preferred that the first longitudinal portion is adjacent to the additional longitudinal portion.

[0172] Preferably, the length of the first longitudinal portion differs from the average length of all first longitudinal portions by no more than 20%, preferably no more than 15%, and more preferably no more than 10%. Preferably, the length of the additional longitudinal portion differs from the average length of all additional longitudinal portions by no more than 18%, preferably no more than 12%, and more preferably no more than 6%. Preferably, the length of the further longitudinal portion differs from the average length of all further longitudinal portions by no more than 20%, preferably no more than 15%, and more preferably no more than 10%.

[0173] In one aspect of the invention, the length of the additional longitudinal portion is preferably in the range of 0.5 to 0.98 times the length of the tube, more preferably in the range of 0.6 to 0.97 times, and even more preferably in the range of 0.8 to 0.95 times. Preferably, the length of the additional longitudinal portion is less than the length of the additional longitudinal portion. More preferably, the length of the additional longitudinal portion is in the range of 40 mm to 300 mm, more preferably in the range of 60 mm to 280 mm, and even more preferably in the range of 90 mm to 250 mm. Preferably, the length of the first longitudinal portion is less than the length of the additional longitudinal portion. More preferably, the length of the first longitudinal portion is in the range of 40 mm to 200 mm, more preferably in the range of 60 mm to 180 mm, and even more preferably in the range of 90 mm to 150 mm.

[0174] Export space

[0175] It is possible that at least one layer comprising granular solid material may be present in the inlet space, in the outlet space, or in both. This layer may take the form of, for example, a sheet of uniform thickness covering the outlet end of the tube and the outer surface of the additional metal plate. The sheet may be subdivided into segments, each filled with granular solid material, for example, in a woven shape. For example, in the form of a pile of granular solid material covering only the outlet end. Here, the outer surface of the additional metal plate is defined as not touching the surface of the additional metal plate containing the liquid cooling aid.

[0176] Preferably, the average thickness of the layer in the outlet space is less than 200 mm, more preferably less than 100 mm, and even more preferably less than 50 mm. It is even more preferably that the outlet space does not contain any particulate solid material. Preferably, the average thickness of the layer in the inlet space is less than 200 mm, more preferably less than 100 mm, and even more preferably less than 50 mm. It is even more preferably that the inlet space does not contain any particulate solid material. Particularly preferably, both the inlet space and the outlet space do not contain any particulate solid material.

[0177] First catalyst

[0178] According to one aspect of the invention, the additional longitudinal portion is filled with a first solid catalyst capable of partially oxidizing the feed stream. Many solid catalysts suitable for this purpose are known to those skilled in the art. Among them, solid catalysts suitable for partially oxidizing C3-C6 aldehydes to carboxylic acids are preferred. More preferably are solid catalysts comprising metal oxides, and even more preferably are catalysts comprising mixed metal oxides.

[0179] Examples of suitable catalysts include those described in detail in the following documents: WO 2008 / 145418 A1, WO2004 / 073857 A1, WO 2019 / 141203 A1, and US 5,583,084, with WO 2019 / 141203 A1 being preferred. It is also preferable not to limit the selection of a suitable catalyst to a single catalyst, and mixtures containing any number of suitable catalysts can be used.

[0180] Granulated solid materials

[0181] According to one aspect of the invention, the additional longitudinal portion is filled with granular solid material arranged and adaptively adjusted for heat dissipation. There are no particular limitations on the selection of the granular solid material, and many suitable examples are well known to those skilled in the art. These examples include oxides, sulfides, nitrides, carbides, carbonates, and silicates of alkali metals, alkaline earth metals, and transition metals, as well as metals, metalloids, and nonmetals of Groups III, IV, and V of the periodic table, and mixtures thereof.

[0182] Examples of preferred choices include magnesium oxide, calcium oxide, α-alumina, γ-alumina, silicon dioxide, titanium dioxide, zinc oxide, silicon nitride, aluminum silicate, ceramic materials, common refractory materials, and glass. Other preferred choices include silicon carbide, bentonite, block talc, mullite, kyanite, pumice, diatomaceous earth, and kaolin, or combinations of two or more of these. Particularly preferred are α-alumina or γ-alumina, or both.

[0183] Further preferably, the granulated solid material is selected from materials (chemical elements and their compounds) having a thermal conductivity falling within either of two ranges. For the first range, the thermal conductivity is preferably in the range of 0.01 W / m / ℃ to 8.5 W / m / ℃, more preferably in the range of 0.05 W / m / ℃ to 5 W / m / ℃, and even more preferably in the range of 0.1 W / m / ℃ to 2 W / m / ℃. For the second range, the thermal conductivity is preferably in the range of 10 W / m / ℃ to 150 W / m / ℃, more preferably in the range of 11 W / m / ℃ to 70 W / m / ℃, and even more preferably in the range of 12 W / m / ℃ to 25 W / m / ℃.

[0184] Materials falling within the first thermal conductivity range are preferably less chemically reactive than those in the second range. Examples of granular solid materials falling within the first range are inorganic materials such as sand, sandstone, and granite. Granular solid materials falling within the second range are typically metals, with examples including steel, aluminum, and copper. If the granular solid material is steel, stainless steel is preferred.

[0185] Preferably, the selection of granular solid materials is not limited to a single material, but can be a mixture containing any amount of the aforementioned elements and compounds. More preferably, one or more granular solid materials from the first thermal conductivity range are combined with one or more granular solid materials from the second thermal conductivity range.

[0186] In one aspect of the invention, there is no limitation on the geometry of the individual particles constituting the granular solid material. For example, the granular solid material may have one or more of substantially any of the following shapes: spheres, rings, rods, flakes, brushes, grids, hollow cylinders, and foams, or combinations of two or more of the above shapes. For example, the granular solid material may also be in the form of one or more of woven fabrics, nets, or knitted fabrics. However, it is preferred that the particle size distribution of the granular solid material is determined by at least one dimension of the tube (more preferably the diameter of the inner surface of the tube).

[0187] Preferably, the granulated solid material should be arranged and adapted to be gas-permeable. The phrase "arranged and adapted to be gas-permeable" should be understood to mean that the granulated solid material can be porous, or more preferably, that the granulated solid material contains spaces through which the product stream can flow. These spaces are preferably located between or within the individual particles constituting the granulated solid material. Their presence may be due to the geometry of the individual particles. For example, if the individual particles are spheres of similar size, small spaces will exist between the spheres, even if the spheres touch each other. For example, if the individual particles are hollow cylinders of similar size, the product stream can flow through the internal space of the cylinder.

[0188] The granulated solid material is commercially available from, for example, Vereinigte. -Fabriken GmbH & Co.KG, Germany, and Raschig GmbH, Germany.

[0189] Liquid cooling aid

[0190] According to one aspect of the invention, at least a portion of the outer surface of the tube is immersed in and in thermal contact with the liquid cooling agent. In this aspect, preferably at least 50%, more preferably at least 80%, and even more preferably at least 95% of the outer surface of the tube is in thermal contact with the liquid cooling agent. The expression "immersed in" should be understood to mean that the liquid cooling agent can flow through the space between the tubes.

[0191] The liquid cooling aid, acting as a heat transfer aid, provides a mechanism for regulating the temperature of the product stream in the tube, and preferably provides a mechanism for regulating the temperature of the catalyst, product stream, or both in the additional longitudinal section. The term "cooling aid" should therefore not be interpreted as meaning that the liquid cooling aid is specifically used for cooling the tube. If necessary, the liquid cooling aid can also be used to heat the tube. The choice of liquid cooling aid is not particularly limited, and many options are well known to those skilled in the art. Suitable liquid cooling aids in salt bath form are commercially available, for example, from HEFDurferrit GmbH, Germany. Suitable liquid cooling aids in oil form are commercially available, for example, from Marlotherm, from Sasol GmbH, Germany.

[0192] In another aspect of the invention, it is preferable that the additional metal plate is in thermal contact with the liquid cooling agent, thereby allowing the temperature of the additional metal plate to be regulated by the liquid cooling agent. The temperature of the additional metal plate may optionally be regulated independently of the temperature of the liquid cooling agent. However, such independent temperature regulation of the additional metal plate generally adds unnecessary complexity to the first reactor without providing any benefit to productivity or safety, and often requires additional maintenance.

[0193] In one aspect of the invention, the first reactor preferably further includes at least one inlet opening allowing the liquid cooling aid to flow into the first reactor, and at least one outlet opening allowing the liquid cooling aid to flow out of the reactor. This allows the liquid cooling aid to flow through the first reactor.

[0194] In this regard, it is preferable that the position of the at least one inflow opening is closer to the other metal plate relative to the first metal plate, and the position of the at least one outflow opening is closer to the first metal plate relative to the other metal plate. However, in this regard, it is particularly preferred that the position of the at least one inflow opening is closer to the first metal plate relative to the other metal plate, and the position of the at least one outflow opening is closer to the other metal plate relative to the first metal plate.

[0195] In another aspect of the invention, it is preferred that the temperature of the liquid cooling aid is adjusted outside the reactor. This can be accomplished using any heating / cooling device known to those skilled in the art and available commercially from, for example, Deggendorfer Werft, Germany.

[0196] Second reactor

[0197] According to one aspect of the invention, the reactor assembly optionally includes a second reactor located upstream of and in fluid communication with the first reactor. The second reactor is used to partially oxidize an aldehyde precursor to a C3-C6 aldehyde, wherein the C3-C6 aldehyde is a component contained in the feed stream flowing into the first reactor.

[0198] The preferred C3-C6 aldehyde to be prepared is preferably C3-C6 alkyl acrolein, and more preferably methacrolein. Further details of the method for preparing the C3-C6 aldehyde are described, for example, in WO 2008 / 145418 A1 and EP 1 995 232 B1.

[0199] Preferably, the second reactor is also a tube bundle reactor. Therefore, any embodiment or aspect of the first reactor, preferably or otherwise, or any of the tube bundle reactors disclosed in, for example, DE 30 42 468 A1, DE 100 47 693 A1 and DE 19806 810 A1, is also applicable to the second reactor.

[0200] Third reactor

[0201] According to one aspect of the invention, the reactor assembly optionally includes a third reactor downstream of and in fluid communication with the first reactor. The third reactor is adaptively adapted and arranged to esterify the product stream prepared in the first reactor over a third catalyst to obtain an ester.

[0202] Preferably, the product stream comprises a C3-C6 carboxylic acid, which is esterified to obtain an alkyl ester, preferably an alkyl acrylate, more preferably an alkyl methacrylate, and even more preferably methyl methacrylate.

[0203] The third reactor is not particularly limited, and any reactor suitable for esterification can be used. However, a reactor suitable for liquid-phase esterification is preferred. More preferably, a reactor suitable for esterifying C3-C6 carboxylic acids to form methyl methacrylate is preferred. Further details of the esterification methods related to this invention can be found, for example, in WO 2008 / 145418 A1 and EP 1995 232 B1.

[0204] Preparation of products

[0205] If the product is an unsaturated alkyl carboxylic acid, it is preferred to prepare the product using any embodiment of the first reactor disclosed in the preceding sections. If the product is an unsaturated alkyl ester, it is preferred to prepare the product in an esterification step. Even more preferably, this esterification step is carried out using any embodiment of the third reactor disclosed in the preceding sections.

[0206] If the product is a polymer, it is preferably prepared by subjecting an unsaturated alkyl ester to a polymerization reaction to obtain the product in polymer form, preferably polymethyl methacrylate. The polymerization is not particularly limited and can be carried out by any method known to those skilled in the art, such as those described in US 5,292,797, US 4,562,234, US 5,773,505, US 5,612,417, US 4,952,455, US 4,948,668, and US 4,239,671. A preferred polymerization method is free radical polymerization, initiated by an initiator that decomposes into free radicals under polymerization conditions, wherein the polymerization is preferably solution or emulsion polymerization, and more preferably aqueous solution polymerization.

[0207] Further details regarding the methods and apparatus required to obtain products in the form of unsaturated alkyl esters or polymers, or to prepare said polymers using said unsaturated alkyl esters, are discussed, for example, in EP 1 995 232 B1.

[0208] The present invention preferably relates to apparatus and methods for cooling product streams prepared by partial oxidation of C3-C6 aldehydes. Methods for preparing feed streams containing said C3-C6 aldehydes, including a partial oxidation step comprising partial oxidation to said C3-C6 aldehydes, the esterification step, and further details of any additional steps that may be necessary to prepare said polymers are disclosed, for example in WO 2008 / 145418 A1 and EP 1 995 232 B1.

[0209] Temperature regulation

[0210] The partial oxidation of the gaseous feed stream to obtain the first product stream should be carried out in a controlled manner, and according to one aspect of the invention, it typically occurs in an additional longitudinal section containing a solid catalyst suitable for partial oxidation. Preferably, auto-oxidation that may occur outside said additional longitudinal section should be suppressed.

[0211] One aspect of the invention is cooling the product stream when the first product stream is not in contact with the solid catalyst. Preferably, the cooling occurs in a separate longitudinal section. More preferably, the cooling is such that R... p >R e It is performed at a sufficiently fast rate as required.

[0212] Temperature drop rate R p The rate of temperature decrease, R, is defined as the rate when the additional longitudinal portion contains granular solid material. e It is defined as the rate when the additional longitudinal portion does not contain granular solid material.

[0213] The rate of temperature decrease, R, is defined as

[0214]

[0215] Where T is temperature, Δx = x2 – x1, and x1 and x2 are two points in space. The x-axis is arranged parallel to the line describing the trajectory of the center of the additional longitudinal section, where x2 is downstream of x1. Therefore, x2 > x1 and Δx > 0. Since the additional longitudinal section may be located, for example, in a straight pipe or in a pipe of “S” shape, the variable Δx refers to the distance the fluid mass needs to travel through the additional longitudinal section, assuming the flow is laminar. It should be noted that R is defined such that R > 0 when the temperature decreases from x1 to x2. Preferably, x1 and x2 are the start and end points of the additional longitudinal section, respectively.

[0216] The preferred temperature for the partial oxidation depends on the components contained in the feed stream. Preferably, the average pressure in the tube is in the range of 1 bar to 5 bar.

[0217] The process of controlling the temperature of the first product stream is preferably accomplished by using a liquid cooling aid. More preferably, the additional longitudinal portion is filled with granular solid material. Even more preferably, the additional longitudinal portion is embedded in an additional metal plate. Further preferably, the additional metal plate is in thermal contact with the liquid cooling aid. Even further preferably, the additional longitudinal portion, the additional longitudinal portion, the liquid cooling aid, the granular solid material, and the additional metal plate are located in the first reactor, as described in the preceding sections.

[0218] As an extension of the preferred cooling method, it is further preferred to either select a granulated solid material with a specific thermal conductivity, increase the length of the additional longitudinal portion, increase the amount of granulated solid material in the additional longitudinal portion, control the pressure in the additional longitudinal portion, change the size of the granulated solid material, or combine any number of these possible solutions.

[0219] If granular solid materials are used to achieve R p >R e The preferred method is to use granulated solid materials disclosed for the first reactor. Further preferably, the additional longitudinal portion and the additional longitudinal portion are part of a tube in any disclosed embodiment of the first reactor.

[0220] The present invention will now be described by way of non-limiting embodiments, exemplary implementations, and accompanying drawings. It should be noted that the drawings are not drawn to scale. Detailed Implementation

[0221] Optional gas cooler

[0222] The control and treatment of the gas exiting the first outlet is particularly problematic for the safe operation of the method. This reaction gas contains components that tend to decompose or undergo further oxidation, especially methacrylic acid and methacrolein. During decomposition, one molecule of a selected critical component produces two or more molecules of fission and oxidation products, accompanied by an undesirable increase in pressure. Decomposition products such as methacrolein, methacrylic acid, CO, CO2, acetic acid, acetone, or acetaldehyde may form. In summary, these side effects reduce the overall yield and efficiency of the method. Furthermore, a critical state may occur due to this pressure increase. In various publications, these effects are referred to as post-combustion, blue flame, and autooxidation (see Ingold, 1961, “Inhibition of Autooxidation of Organic Substances”, EP 30 07 69 or US 3,876,693). Various methods and apparatuses for mitigating these side effects have been described in the prior art, but these proposed solutions are unsuitable or insufficient for the specific problem of oxidizing methacrolein to methacrylic acid according to the present invention.

[0223] Therefore, it is particularly preferred that the reactor assembly includes a gas cooler connected to the first outlet. Here, the gas stream is cooled from a first outlet temperature that may be in the range of 230°C to 360°C to a lower temperature in the range of 160°C to 280°C, preferably in the range of 190°C to 270°C, and more preferably in the range of 200°C to 260°C. This preferred embodiment of the invention prevents any afterburning or blue flame effects.

[0224] The gas cooler may be located inside or outside the reactor. A characteristic feature of the cooler is that it operates with cooling medium II, which does not correspond to cooling medium I of the catalyst bed. A shell-and-tube cooler, operated with boiler pressurized water, is preferred. Here, heat or energy is transferred from the reactant gas to the cooling medium, potentially generating water vapor.

[0225] The residence time of the gas in the reactor outlet chamber and around the cooler is controlled such that the residence time is in the range of 0.1 seconds to 10 seconds, preferably in the range of 1 second to 7 seconds. Attached Figure Description

[0226] Figure 1 : A schematic diagram of the cross-section of the first reactor.

[0227] Figure 2 The steps included in the method for preparing the product.

[0228] Figures 3.1-3.5 Exemplary temperature profiles in the first reactor. Different profiles correspond to different experimental settings.

[0229] Figure 1 A schematic diagram (not drawn to scale) of the components comprising a first reactor 100 according to the invention is shown. This diagram illustrates a preferred embodiment of the invention and should therefore not be considered limiting.

[0230] The solid arrows indicate the flow direction through the first reactor 100. The feed stream flows into the first reactor 100 through the first inlet 101 and into pipe 102 through the inlet end 103. As the feed stream flows through pipe 102, it is partially oxidized into a product stream, which exits pipe 102 through the outlet end 104. The product stream then flows out of the first reactor 100 through the first outlet 105.

[0231] The tube 102 has a first longitudinal portion 106. Downstream of the first longitudinal portion is an additional longitudinal portion 107 filled with a first solid catalyst (not shown). Downstream of the additional longitudinal portion 107 is another longitudinal portion 108 filled with granular solid material 109. Furthermore, the first longitudinal portion 106 does not contain any first solid catalyst or any granular solid material 109.

[0232] Figure 1 The first longitudinal portion 106 and the additional longitudinal portion 107 are shown to be adjacent to each other. The latter's longitudinal portion is further shown to be adjacent to another longitudinal portion 108. While it is preferred that the aforementioned longitudinal portions be adjacent to each other, this is not mandatory.

[0233] A first longitudinal portion 106 is embedded in a first metal plate 110. An inlet space 114 is defined by a first inlet 101 and the outer surface 111 of the first metal plate 110. A further longitudinal portion 108 is embedded in another metal plate 112. An outlet space 115 is defined by a first outlet 105 and the outer surface 113 of the other metal plate 112. Figure 1 It can be seen that the first inlet 101, the inlet space 114, the pipe 102, the outlet space 115 and the first outlet 105 are fluidly connected to each other.

[0234] although Figure 1 The first longitudinal portion 106 is shown to be fully embedded in the first metal plate 110, but the first longitudinal portion 106 may also extend beyond the first metal plate 110, either into the inlet space 114 or into the opposite direction, or both. Similarly, the additional longitudinal portion 108 may also extend beyond the additional metal plate 112, either into the outlet space 115 or into the opposite direction, or both.

[0235] Liquid cooling aid 116 flows through the space between tubes 102 and comes into thermal contact with the outer surface (not shown) of tubes 102. The liquid cooling aid enters and exits the first reactor 100 through openings 117 and 118. Dashed arrows indicate that either opening 117 or 118 can be used as an inflow and outflow opening, thus providing a possible means of controlling the flow direction of the liquid cooling aid 116.

[0236] although Figure 1 Only two openings, 117 and 118, for the liquid cooling agent 116 are shown, but the first reactor 100 may contain any number of openings. Furthermore, these openings may be arranged anywhere between the first metal plate 110 and the other metal plate 112. For example, openings 117 and 118 should be arranged and adapted to not be in fluid communication with the inlet space 114 and the outlet space 115. For example, if the first reactor 100 has a generally spherical shape, openings 117 and 118 may be located anywhere on the periphery of the first reactor 100.

[0237] in addition, Figure 1 The location of opening 117 is closer to the other metal plate 112 than the first metal plate 110, while opening 118 is closer to the first metal plate 110 than the other metal plate 112. If opening 117 is used as an outflow opening and opening 118 is used as an inflow opening, the flow direction of the liquid cooling aid 116 will be substantially to the left and upward. More preferably, opening 118 is used as an inflow opening and opening 117 as an outflow opening. Figure 1 In this case, the flow direction of the liquid cooling agent 116 will be basically to the left and upward.

[0238] although Figure 1 The diagram shows the feed / product stream flowing upward through the first reactor 100, but all possible flow paths through the first reactor fall within the scope of this invention. This includes, for example, embodiments in which the first reactor 100 is arranged such that the feed / product stream will flow downward.

[0239] Figure 2 The steps included in method 200 for preparing a product are shown, wherein the preferred form of the product is: a) preferably a polymer or b) preferably an unsaturated alkyl carboxylic acid compound, more preferably an unsaturated alkyl carboxylic acid or unsaturated alkyl ester, further preferably an alkyl acrylate, even more preferably an alkyl methacrylate, and particularly preferably methyl methacrylate.

[0240] In the first step 230, a gaseous feed stream is provided, comprising a C3-C6 aldehyde, preferably methacrolein. In the subsequent step 240, the gaseous feed stream is partially oxidized over a solid catalyst to obtain a first product stream, wherein the solid catalyst is located in an additional longitudinal section. Preferably, the first product stream comprises a carboxylic acid, more preferably methacrylic acid. Step 250 includes cooling the first product stream in an additional longitudinal section, wherein the temperature increases at a rate R. p The descent. The additional longitudinal portion comprises granular solid material.

[0241] Figure 2 The method is shown to may also include an optional pre-step 220. In this pre-step 220, a product stream containing an aldehyde precursor is prepared from a feed stream containing a C3-C6 aldehyde, preferably methacrolein. The product stream prepared in the pre-step 220 then forms part of the feed stream 230.

[0242] In a preferred embodiment, the C3-C6 aldehyde is prepared by partial oxidation in a preliminary step 220. Additionally, the resulting product stream may undergo any number of further processing steps, such as cooling and purification.

[0243] One or more subsequent processing steps 260 may also be included in the method, and may include, in particular, the following processes in any order and in any combination: quenching of the first product stream 261, purification of the first product stream 262, esterification of the first product stream 263, and polymerization of the ester prepared in 263 264.

[0244] Figures 3.1-3.5 Exemplary temperature profiles for the feed stream and the first product stream in the first reactor are shown. The gaseous mixture flowing into the first reactor via the first inlet before the partial oxidation begins is defined as the feed stream. After the partial oxidation begins, the gaseous mixture is defined as the first product stream.

[0245] Below the temperature profile is a tube having a first longitudinal portion 306, an additional longitudinal portion 307, and a further longitudinal portion 308. The first longitudinal portion 306 is embedded in a first metal plate 310, while the further longitudinal portion 308 is embedded in a further metal plate 312. The additional longitudinal portion 307 is filled with a solid catalyst (not shown). Upstream of the inlet end 303 of the tube is an inlet space 314. Downstream of the outlet end 304 of the tube is an outlet space 315. Arrows indicate the direction of flow through the reactor.

[0246] exist Figures 3.1-3.5 The temperature profiles are shown for the following components of the first reactor:

[0247] 314: Entrance Space

[0248] 306: First longitudinal section

[0249] 307: Additional Vertical Section

[0250] 308: Other vertical sections

[0251] 315: Export Space

[0252] It should be noted that when stating "the temperature reaches a constant value," this should be understood as meaning approximately constant. Figures 3.1-3.5 The curves in the curves have the same qualitative shape. In the inlet space 314, the temperature of the feed stream remains constant. In the first longitudinal section 306, the temperature of the feed stream increases slightly. In the additional longitudinal section 307, partial oxidation causes the temperature of the first product stream to initially increase sharply to a maximum value, and then gradually decrease to a lower value.

[0253] After exiting the additional longitudinal section 307, the first product stream flows through another longitudinal section 308 and into the outlet space 315. The characteristics of the temperature profiles in the other longitudinal section 308 and the outlet space 315 are determined by the presence (or absence) of the granulated solid material 309. This characteristic will be discussed in more detail below. It should be noted that in Figures 3.1-3.5 In the middle, T auto Indicates the auto-oxidation temperature of the first product stream.

[0254] exist Figure 3.1 In this reactor, the first reactor does not contain any particulate solid material. Two temperature profiles are shown. The first profile, 391, is for a first reactor where the solid catalyst is fresh (prepared 1 month ago), and the second profile, 392, is for a first reactor where the solid catalyst has been used (prepared 2 years ago). Both profiles show a slight decrease in temperature at 308. However, at 315, the temperature remains constant. Figure 3.1 It is also stated that when the catalyst is fresh, the temperature of the product stream leaving 308 is below T. auto As shown in curve 391. However, when the catalyst is used, as shown in curve 392, the temperature of the product stream leaving 308 is higher than T. auto .

[0255] exist Figures 3.2-3.5 In this reactor, the first reactor contains granular solid material 309. The presence of granular solid material 309 results in temperature curves 393 and 394. Curve 393 represents the case where a fresh solid catalyst is used, and curve 394 represents the case where a solid catalyst prepared two years ago is used. Figures 3.2-3.4The description clearly specifies the components in the first reactor containing granular solid material 309. If not specified, the components do not contain the granular solid material.

[0256] Figure 3.2 The first longitudinal portion 306 is shown to be filled with granular solid material 309. This results in curve 393, where the temperature of the product stream exiting 308 is below T. auto .

[0257] Figure 3.3 The diagram shows that the additional longitudinal section 308 is filled with granular solid material 309. This results in curve 394, where the temperature in 308 drops rapidly and then reaches a constant value. The temperature also remains constant in 315. It should be noted that the temperature of the product stream leaving 308 is below T. auto Conversely, the dashed line indicates that the product stream leaving 392a is at a temperature higher than T. auto , where 392a corresponds to the case under the following conditions, which are for the above Figure 3.1 The condition described by the solid line 392 in the figure.

[0258] Figure 3.4 The other longitudinal portion 308 is shown to be filled with granular solid material 309. Figure 3.4 Further explanation is that the exit space 315 contains multiple layers of granular solid material 309. This results in curve 394. More specifically, the temperature in 308 drops rapidly and then reaches a constant value. However, compared to... Figure 3.3 Conversely, in 315, the temperature drops rapidly again before reaching a constant value. The product stream leaving 308 also exits at a temperature below T. auto .

[0259] exist Figure 3.5 The settings in the middle are similar to Figure 3.4 The setup in the middle, except that the exit space 315 contains only a single layer of granular solid material 309. Figure 3.4 Curve 394 and in Figure 3.5 The main difference between curves 394 and 315 is that the temperature drop is more gradual in curve 315 than in the latter case. Figure 3.5 In the middle, the temperature of the product stream leaving 308 is also lower than T. auto .

[0260] Test methods

[0261] Unless otherwise stated, all test methods not involving the measurement of fluid properties are performed at a temperature of 25°C and a pressure of 1 atmosphere.

[0262] length

[0263] The length of the tube or the longitudinal portion of the tube (the first longitudinal portion, the additional longitudinal portion, or the other longitudinal portion) is measured along an imaginary line describing the center of the tube or the center of the longitudinal portion of the tube.

[0264] Layer thickness

[0265] The thickness of the layer of granular solid material in the inlet or outlet space can be measured using a ruler. The thickness is measured by placing one end of the ruler at the outlet end of the tube, with the ruler kept parallel to the tube. To obtain an average thickness, the thickness is measured at 5% of the outlet end of the tube.

[0266] quality

[0267] The mass of the first solid catalyst or the granulated solid material can be measured using any commercially available scale.

[0268] Particle size

[0269] The particle size constituting the granular solid material was measured according to standard BS1796-1:1989. For sieve analysis, at least six sieves were used.

[0270] Geometric specific surface area

[0271] Geometric surface area defines the outer surface of an object.

[0272] Free volume

[0273] The granulated solid material is filled into a container of known volume. Water is then added to the container until it is full. The volume of water added to the container is divided by the volume of the container and then multiplied by 100. This gives the free volume of the granulated solid material as a percentage. Many suitable containers are known to those skilled in the art, and any container deemed suitable can be used. Many methods for measuring the volume of water added to the container are known to those skilled in the art, and any method deemed suitable can be used.

[0274] temperature

[0275] The temperature of the product stream is measured along the tube using a thermocouple placed at the center of the tube. The thermocouple extends along the length of the tube. The thermocouple can also measure the temperature at 20 points within the tube. The temperature of the liquid cooling agent is also measured using a thermocouple. The thermocouple is placed at the opening through which the liquid cooling agent flows into the first reactor. Suitable thermocouples are known to those skilled in the art and are commercially available.

[0276] pressure

[0277] The pressure is measured in the inlet space and the outlet space. Therefore, the pressure drop is defined as the decrease in pressure between the inlet space and the outlet space. The pressure is measured using a pressure gauge. Such measuring instruments are well known to those skilled in the art and are commercially available.

[0278] Speed ​​(GHSV)

[0279] Mass flow rate is measured using a mass flow meter. Such measuring instruments are well known to those skilled in the art and are commercially available. GHSV can be calculated from this measurement. This calculation is well known to those skilled in the art.

[0280] thermal conductivity

[0281] The appropriate thermal conductivity for granular solid materials can be found in textbooks such as the Handbook of Chemistry and Physics, 56th edition (1975).

[0282] Chemical composition

[0283] The chemical composition was determined by gas chromatography. The measurements were performed in both the inlet and outlet spaces. The methods and apparatus for performing these measurements are well known to those skilled in the art.

[0284] Example

[0285] Numerous experiments were conducted in which the distribution of granular solid material in the first reactor varied. Apart from the differences mentioned above, all experiments had the same initial settings, as described in the following sections.

[0286] Initial settings

[0287] The feed stream is fed into a tubular reactor commercially available from Deggendorfer Werft, Germany. The feed stream is partially oxidized along an additional longitudinal section containing a first solid catalyst to obtain a product stream containing methacrylic acid. The selection of the first solid catalyst is described in WO 2019 / 141203 A1.

[0288] The feed stream flowing into the first reactor has a temperature of 235°C and a flux of 1000 Nm. 3 / m 3 The gas space-time velocity is h. The average pressure in the tube is in the range of 1.25 to 2.5 bar. Furthermore, the composition of the feed stream is given in Table 1.

[0289] Table 1: Composition of the feed flow

[0290]

[0291] Each tube in the tubular reactor has a first longitudinal portion, an additional longitudinal portion, and a further longitudinal portion. The first longitudinal portion has an average length of 120 mm, the additional longitudinal portion has an average length of 3900 mm, and the further longitudinal portion has an average length of 150 mm. Furthermore, the first longitudinal portion is adjacent to the additional longitudinal portion, and the additional longitudinal portion is adjacent to the further longitudinal portion.

[0292] For each of the tubes, the following characteristics also apply: the entire length of the additional longitudinal section is filled with the first solid catalyst. The mass percentage of the first solid catalyst contained in the additional longitudinal section is 99% by weight based on the total mass of the first solid catalyst contained in the tube. Furthermore, the mass of the first solid catalyst in a single tube varies by no more than 2% relative to the average mass calculated for all tubes. It should be noted that the average mass is calculated considering the mass of the first solid catalyst in all tubes across all experiments.

[0293] The first reactor also includes a first metal plate and another metal plate. Both the first metal plate and the other metal plate have a thickness of 100 mm. Furthermore, both the first metal plate and the other metal plate are in thermal contact with a liquid cooling aid. The liquid cooling aid is a commercially available salt bath from HEF Durferrit GmbH, Germany.

[0294] The reactor has two openings that allow the liquid cooling agent to flow into and out of the reactor. The inflow opening is located closer to the first metal plate than the other metal plate, while the outflow opening is located closer to the other metal plate than the first metal plate. The temperature of the liquid cooling agent flowing into the reactor is adjusted to have an average value of 290°C.

[0295] The granulated solid material used is alumina, and the size distribution of the granulated solid material is in the range of 3 mm to 7 mm. The granulated solid material is commercially available from Vereinigte. -Fabriken GmbH&Co.KG, Germany.

[0296] Distribution of granular solid materials

[0297] The distribution of granular solids in the first reactor varies for different experiments. For all experiments, the inlet space is free of granular solids. Additionally, the mass percentage of granular solids in the extra longitudinal section of a tube is less than 1% by weight, based on the total mass of granular solids in the tube.

[0298] For different experiments, the distribution of the granular solid material in the first reactor is as follows:

[0299] 1. No particulate solid material is present in the first longitudinal section, the other longitudinal section, or the outlet space;

[0300] 2. There is granular solid material in the first longitudinal section, but not in the other longitudinal section or the outlet space;

[0301] 3. There is granular solid material in the other longitudinal section, but not in the first longitudinal section or the outlet space;

[0302] 4. Particulate solid material is present in the other longitudinal section and the outlet space, but not in the first longitudinal section. The thickness of the layer of particulate solid material in the outlet space is 250 mm.

[0303] 5. Particulate solid material is present in the other longitudinal section and the outlet space, but not in the first longitudinal section. The thickness of the layer of particulate solid material in the outlet space is 50 mm.

[0304] The following characteristics also apply to all experiments: when the first longitudinal portion or the other longitudinal portion contains granular solid material, the entire length of the applicable longitudinal portion is filled with the granular solid material. Furthermore, the variation in the mass of the granular solid material in a single tube relative to the average mass calculated for all tubes is no greater than 2%. It should be noted that the average mass is calculated considering the mass of the granular solid material in all tubes across all experiments.

[0305] When the granular solid material is placed in the outlet space, as in Experiments 4 and 5, the granular solid material is randomly poured onto the other metal plate and then leveled so that the thickness of the layer of granular solid material in the outlet space is approximately constant. Furthermore, the granular solid material in the outlet space is in the form of spheres with a diameter of 5 mm.

[0306] Experimental results

[0307] Table 2 summarizes the results of the experiments. Table 2 also indicates whether the granular solid material was present in a given portion of the first reactor. It should be noted that both Experiment 4 and Experiment 5 contained granular solid material in the outlet space. However, the amount in Experiment 4 was greater than that in Experiment 5.

[0308] It should be noted that the results are for a first solid catalyst that has been operated for two years. Exceptions are experiments 1a and 2, which show results for a fresh catalyst. Additionally, Table 2 indicates the numbering of the figures illustrating the feed / product flow temperature profiles in the first reactor.

[0309] Table 2: Distribution of granular solid material in the first reactor and comparison of experimental results.

[0310]

[0311] Regarding the results shown in Table 2, the following should be noted:

[0312] ·T out <T auto Indicates the temperature T in the outlet space. out Is it below the auto-oxidation temperature T? auto .

[0313] ·T out The temperature of the product stream in the outlet space.

[0314] • R: The rate at which the temperature of the product stream decreases in the additional longitudinal section.

[0315] • Downtime: The downtime required to run the first reactor. The results are graded, with 1 indicating the minimum downtime and 5 indicating the maximum downtime.

[0316] • Safety: Indicates how safely the first reactor can operate. The results are graded, with 1 being the safest and 5 the least safe.

[0317] • Yield difference: The yield of Experiment 1a, in which no particulate solid material exists in the reactor, is used as a baseline. A positive value indicates an increase in yield compared to Experiment 1a, and a negative value indicates a decrease in yield compared to Experiment 1a.

[0318] • ΔP: Pressure reduction between the inlet space and the outlet space. A smaller value is preferred.

[0319] List of reference numerals

[0320] 100 First Reactor

[0321] 101 First Entrance

[0322] 102 tubes

[0323] 103 tube inlet end

[0324] 104 tube outlet end

[0325] 105 First Exit

[0326] 106 First longitudinal section

[0327] 107 Additional vertical sections

[0328] 108. Other vertical sections

[0329] 109 Granular Solid Materials

[0330] 110 First Metal Plate

[0331] 111 Outer surface of the first metal plate

[0332] 112 Other metal plates

[0333] 113 Additionally, the outer surface of the metal plate

[0334] 114 Entrance Space

[0335] 115 Exit Space

[0336] 116 Liquid Cooling Agent

[0337] 117 Opening of liquid coolant

[0338] 118 Opening of liquid coolant

[0339] 200 Method for preparing the product

[0340] 220 Optional preparation of C3-C6 aldehydes

[0341] 230 provides gaseous feed flow

[0342] Partial oxidation of the 240 feed stream

[0343] 250 Cooling of the first product stream

[0344] 260 Optional methods and steps

[0345] 261 Sudden Cooling of the First Product Flow

[0346] 262 Purification of the first process flow

[0347] 263 Esterification of Process Flow

[0348] 264 Polymerization of the ester prepared in 262

[0349] 303 Entry Point

[0350] 304 Export End

[0351] 306 First longitudinal section

[0352] 307 Additional Vertical Section

[0353] 308 Other vertical sections

[0354] 309 Granular Solid Materials

[0355] 310 First Metal Plate

[0356] 312 Other metal plates

[0357] 314 Entrance Space

[0358] 315 Export Space

[0359] 391 Temperature profiles of non-particulate solid materials: fresh catalyst

[0360] 392 Temperature profile of non-particulate solid material: used catalyst

[0361] 393 Temperature profiles of granular solid materials: fresh catalyst

[0362] 394 Temperature profiles of granular solid materials: used catalysts

Claims

1. A reactor assembly arranged in fluid communication, comprising a first reactor for the partial oxidation of C3-C6 aldehydes, the first reactor comprising the following structures as reactor components: a) First entrance; b) The entrance space downstream of the first entrance; c) The first metal plate downstream of the entrance space; d) Another metal plate downstream of the first metal plate; e) The outlet space downstream of the other metal plate; f) The first exit downstream of the exit space; g) A plurality of pipes having a pipe length, wherein each of the pipes (i) Located between the entrance space and the exit space, (ii) Includes an entry point, (iii) Includes the export end, (iv) Includes the outer surface, (v) Includes the inner surface, (vi) includes an inner space defined by the inner surface of the tube; and at least 50% of the tubes therein [I] includes a first longitudinal portion, wherein the first longitudinal portion is positioned within the first metal plate. [II] includes an additional longitudinal portion, wherein the additional longitudinal portion (a) Arranged downstream of the first longitudinal portion, and (b) Contains a first solid catalyst, [III] includes an additional longitudinal portion, wherein the additional longitudinal portion A) Arranged downstream of the additional longitudinal section. B) Positioned within the other metal plate. C) Contains an inert granular solid material, wherein the granular solid material (I) Adaptively adjusted and arranged for heat dissipation, (II) Adaptively adjusted and arranged to be gas-permeable; h) a liquid cooling aid, wherein a portion of the outer surface of the tube is arranged and adaptively configured to contact the liquid cooling aid, wherein the portion is at least 50% of the length of the additional longitudinal portion; And among them, The average thickness of any layer containing the granulated solid material present in the outlet space, the inlet space, or both is less than 10% of the average length of the additional longitudinal portion; At least 30% of the length of the additional longitudinal portion is embedded in the additional metal plate, the additional longitudinal portion being in thermal contact with the additional metal plate, and the additional metal plate being in thermal contact with the liquid cooling aid.

2. The reactor assembly according to claim 1, wherein at least one or all of the following features are applicable: a) The mass percentage of granular solid material present in the first longitudinal section is less than 5% by weight based on the total mass of granular solid material contained in the tube. b) The mass percentage of the first solid catalyst contained in the first longitudinal section is less than 5% by weight based on the total mass of the first solid catalyst contained in the tube.

3. The reactor assembly according to claim 1 or 2, wherein at least one or all of the following features are applicable: a) The mass percentage of the first solid catalyst contained in the additional longitudinal section is greater than 50% by weight based on the total mass of the first solid catalyst contained in the tube. b) The mass ratio of the first solid catalyst, which is contained in the other longitudinal portion, to the mass of the granulated solid material is 1: x ,in x For at least 10 and x This represents the mass of the granulated solid material.

4. The reactor assembly according to claim 1 or 2, wherein the granular solid material comprises one or more components selected from metals and metal oxides.

5. The reactor assembly according to claim 1 or 2, wherein the granulated solid material has at least one or all of the following physical properties: a) Thermal conductivity in the range of 0.01 W / (m·℃) to 500 W / (m·℃); b) at 20 m 2 / m 3 up to 2000 m 2 / m 3 Geometric specific surface area within the range; c) Free volume in the range of 24% to 99%; or d) Particle size distribution in the range of 0.01 mm to 100 mm.

6. The reactor assembly according to claim 1 or 2, wherein the first metal plate, the other metal plate, or both have a thickness in the range of 10 mm to 300 mm independently of each other.

7. The reactor assembly according to claim 1 or 2, wherein the reactor assembly includes a gas cooler connected to the first outlet.

8. A method for preparing a product in a reactor assembly according to any one of claims 1-7, wherein the method comprises the following steps: a) Provide a gaseous feed stream, wherein the feed stream contains C3-C6 aldehydes; b) Partial oxidation of the C3-C6 aldehydes in the feed stream in the presence of a solid catalyst to obtain a first product stream containing the partially oxidized products, wherein the partial oxidation is carried out along an additional longitudinal portion, and c) Cool the first product stream along another longitudinal section, wherein (i) The additional longitudinal portion comprises granular solid material. (ii) The temperature of the product stream in the additional longitudinal section at a rate R p decline; and in R p greater than the rate of temperature decrease R e The rate thereof R e It is the rate in the case where the additional longitudinal portion does not contain the granulated solid material.

9. The method of claim 8, wherein R p yes R e At least twice as much.

10. The method of claim 8 or 9, wherein the rate R p Within the range of 0.1℃ / cm to 5℃ / cm.

11. The method of claim 8 or 9, wherein the temperature of the first product stream exiting the additional longitudinal portion is lower than the auto-oxidation temperature of the first product stream.

12. The method of claim 8 or 9, wherein the temperature of the first product stream exiting the additional longitudinal portion is in the range of >230°C to 360°C.

13. The method of claim 12, wherein the product stream exiting the first outlet is fed into a gas cooler, and wherein the temperature of the product stream exiting the gas cooler is in the range of 160°C to 280°C.

14. The method of claim 8 or 9, wherein the product is methacrylic acid or methyl methacrylate.

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