Reactor and method for carrying out polycondensation or depolymerization reactions

Abstract

The invention relates to a reactor, in particular for carrying out polycondensation or depolymerization reactions, comprising at least one inlet, at least one product outlet line, a liquid zone, an inner zone arranged above the liquid zone, and a gas zone comprising at least one gas outlet line, wherein the gas zone is arranged above the inner zone, and wherein the gas zone has a larger cross-sectional area than the inner zone, and wherein the gas zone comprises a demisting element connected to a scrubbing liquid inlet disposed in the gas zone and a scrubbing liquid outlet disposed in the gas zone, and wherein the inner region comprises one or more inner components selected from the group consisting of a structured packed bed, a random packed bed and a hybrid heat exchange element for increasing the surface to volume ratio within the inner region wherein the one or more inner components have a specific surface area of 10 to 1,000 m2 / m3.

Description

[0001] The present invention relates to reactors, particularly reactors for carrying out polycondensation or depolymerization reactions, and methods for carrying out polycondensation or depolymerization in the respective reactors.

[0002] Polycondensation reactions are widely used to synthesize valuable compounds such as esters, oligoesters, and polyesters. Depolymerization reactions, on the other hand, are used to degrade oligomers and / or polymers into smaller molecules, for example, to degrade lactic acid oligomers and / or polymers into lactide. Important esters include triglycerides, such as fats and oils; monoglycerides, which are commonly used as emulsifiers; fatty acid methyl esters, which are commonly used as synthetic fuels; polyethylene terephthalate (PET); polylactic acid (PLA); and polyethylene furanoates (PEG). Particularly important polyesters are polylactic acid esters, which are gaining increasing importance because they are available from renewable resources and are largely compostable and / or biodegradable. Furthermore, the technical properties of these polymers are very close to those derived from fossil-based resources, which explains why these polymers are considered highly promising alternatives to the latter.

[0003] Generally, two main alternative methods are known for the synthesis of polylactic acid homopolymers or copolymers. The first main method is the direct polycondensation of lactic acid, optionally with one or more comonomers (e.g., caprolactone and / or glycolide), to form homopolymers or copolymers, for example, by directly polycondensing lactic acid to polylactic acid homopolymers. The second main method known for the synthesis of polylactic acid homopolymers or copolymers is the ring-opening polymerization of lactide (a cyclic diester of lactic acid), optionally with one or more other cyclic esters (e.g., glycolide (a cyclic diester of glycolic acid), lactones, etc.). Lactide is typically produced by the condensation of two lactic acid molecules, or by first oligomerizing lactic acid and then subjecting the oligomer to a depolymerization reaction. For example, lactide is prepared by fermenting carbohydrates from biomass (e.g., starch, sugar, or corn) to produce lactic acid, then oligomerizing the lactic acid, and subsequently subjecting the oligomer to a depolymerization reaction.

[0004] During polycondensation, water is generated as a byproduct, dispersed in equilibrium within a viscous reaction mixture. This mixture also contains unreacted monomers, as well as the resulting oligomers and polymers. To improve the conversion rate of the polycondensation reaction, water must be removed from the viscous reaction mixture instantaneously and efficiently. However, due to the high viscosity of the reaction mixture, rapid and efficient removal of water remains a challenge and requires improvement. Similarly, the depolymerization of polymers or oligomers is an equilibrium reaction. To improve the conversion rate of depolymerization (e.g., the depolymerization of oligolactide or polylactide, respectively), the generated monomers (e.g., lactide) need to be removed from the reaction mixture once they are formed. However, the reactants, oligomers, and polymers (e.g., lactic acid oligomers and lactic acid polymers) have associated high viscosity, and removing monomers (e.g., lactide) from the viscous reaction mixture is challenging.

[0005] In view of this, the object of the present invention is to provide a reactor and method for carrying out polycondensation or depolymerization reactions in a specific high yield by effectively removing low molecular weight byproducts such as water generated during the reaction from a viscous (reaction) mixture.

[0006] According to the invention, this objective is achieved by providing a reactor (particularly for carrying out polycondensation or depolymerization reactions) comprising at least one inlet, at least one product outlet line, a liquid zone, an internal zone, and a gas zone including at least one gas outlet line, wherein the internal zone is arranged above the liquid zone, the gas zone is arranged above the internal zone, and the gas zone has a larger cross-sectional area than the internal zone, wherein the gas zone includes a de-entrainment element connected to a wash liquid inlet and a wash liquid outlet, the wash liquid inlet being disposed in the gas zone, the wash liquid outlet being disposed in the gas zone, and wherein the internal zone includes one or more internal components selected from structured packed beds, random packed beds, and mixed heat exchange elements for increasing the surface-to-volume ratio within the internal zone, wherein the one or more internal components have a specific surface area of ​​10 to 1,000 m². 2 / m 3 .

[0007] This solution is based on the finding that the removal of low molecular weight compounds (e.g., water) from highly viscous mixtures (e.g., highly viscous reaction mixtures) can be achieved rapidly and particularly efficiently in a reactor comprising an inner zone above a reaction zone (referred to herein as the liquid zone), and above that, a gas zone having a larger cross-sectional area than the inner zone. Due to the higher mass and heat transfer in the inner zone, efficient pre-separation of the liquid from the gas-liquid mixture containing the highly viscous mixture rising from the liquid zone into the inner zone is possible; while the gas zone above, with its larger cross-sectional area, allows for the efficient removal of residual droplets entrained in the gas rising from the inner zone into the gas zone. This is because the flow of the gas mixture rising from the inner zone into the gas zone is reduced in the gas zone due to its larger cross-sectional area, resulting in the coagulation of entrained droplets into larger droplets, which can then easily fall by gravity and are thus removed from the gas. Furthermore, the demister element included in the gas zone allows for particularly effective removal of liquid entrained in the gas phase rising from the liquid zone through the internal zone and passing through the gas zone. The one or more internal components contained within the internal zone (selected from structured packed beds, random packed beds, and mixed heat exchange elements for increasing the surface-to-volume ratio of the internal zone, having a specific surface area of ​​10 to 1,000 m²) 2 / m 3 This allows for efficient pre-separation of the liquid from the gas within the internal zone, thus increasing mass transfer within the internal zone. Consequently, the reactor and method according to the invention allow for polycondensation or depolymerization reactions in particularly high yields by efficiently removing low molecular weight byproducts (e.g., water) generated during the reaction from viscous (reaction) mixtures.

[0008] The term "zone" as used herein refers to a portion of the reactor. The prefixes "liquid zone," "internal zone," and "gas zone" have no limiting meaning and are used only herein to distinguish the three distinct zones.

[0009] According to the invention, the reactor comprises a liquid zone, an inner zone, and a gas zone. In one embodiment, the reactor is a container comprising the aforementioned zones, wherein individual zones are arranged vertically on top of each other. Alternatively, the reactor may comprise three distinct containers, wherein the first constitutes a liquid zone, the second constitutes an inner zone, and the third constitutes a gas zone, wherein the containers are arranged vertically on top of each other, and wherein the containers are directly or indirectly connected to each other (i.e., via an intermediate element, such as a pipe). However, in all these embodiments, the liquid zone, the inner zone, and the gas zone each comprise a peripheral wall surrounding the periphery of the respective zone, wherein the liquid zone also comprises a bottom wall, and the gas zone also comprises a top wall. Furthermore, the gas zone comprises a bottom wall that surrounds at least the lower portion of the gas zone, and since the gas zone has a larger cross-sectional area compared to the inner zone, the inner zone is not disposed below the lower portion of the gas zone. However, the bottom wall of the gas zone may even extend further to the portion below which the inner zone is disposed. In any case, the bottom wall comprises an opening to allow liquid and gas to flow from the inner zone to the gas zone and vice versa. Furthermore, the liquid zone may include a top wall, and preferably actually include a top wall, particularly when the liquid zone has a larger cross-sectional area than the inner zone. In this variation, the top wall at least surrounds the upper portion of the liquid zone, above which no inner zone is provided due to the larger cross-sectional area of ​​the liquid zone compared to the inner zone. However, the top wall of the liquid zone may even extend further to the portion above which the inner zone is provided. In any case, the top wall includes openings to allow liquid and gas to flow from the inner zone to the liquid zone and vice versa.

[0010] According to the present invention, the gas zone of the reactor has a larger cross-sectional area than the internal zone of the reactor. If the cross-sectional area of ​​the gas zone and / or the internal zone varies along the vertical height of the respective zone, the cross-sectional area refers to the average cross-sectional area of ​​the respective zone. To calculate the average cross-sectional area of ​​a zone, the respective zone is subdivided into adjacent cross-sectional segments, each segment having a height or extension of 1 mm in the vertical direction, wherein the average cross-sectional area of ​​the respective zone is the quotient of the sum of the cross-sectional areas of all cross-sectional segments divided by the number of all segments.

[0011] Preferably, the gas region has a (average) cross-sectional area that is 1 to 400% larger than the (average) cross-sectional area of ​​the interior region, and more preferably 200 to 300% larger.

[0012] As described above, the zones of the reactor can be indirectly connected to each other, for example, via pipes. In this embodiment, the pipes connecting the liquid zone to the inner zone and the pipes connecting the inner zone to the gas zone have a (average) cross-sectional area that is substantially the same as the (average) cross-sectional area of ​​the inner zone. In this regard, "substantially the same cross-sectional area" means that the (average) cross-sectional area of ​​the corresponding pipe is 80% to 120%, preferably 90% to 110%, more preferably 95% to 105%, and most preferably 100% of the (average) cross-sectional area of ​​the inner zone of the reactor.

[0013] According to a particular preferred embodiment of the invention, the gas region is directly connected to the internal region, and the internal region is directly connected to the liquid region, wherein the regions are arranged vertically above each other in the order described above.

[0014] The present invention does not impose any particular limitation on the cross-sectional shape of the liquid region, the interior region, and the gas region. For example, the liquid region, the interior region, and the gas region can each have a circular, oval, elliptical, rectangular, square, or polygonal cross-sectional shape independently of each other. Preferably, the liquid region, the interior region, and the gas region each have the same cross-sectional shape. More preferably, the liquid region, the interior region, and the gas region each have a circular cross-sectional shape, such that, in three dimensions, these regions are each hollow cylinders. Most preferably, in the latter alternative, the gas region has a larger diameter than the interior region.

[0015] In a further refinement of the invention, it is proposed that the liquid region has the same or larger (average) cross-sectional area as the inner region, or, if the liquid region and the inner region each have a circular cross-sectional area, the liquid region has a larger diameter than the inner region. Preferably, the liquid region has a (average) cross-sectional area that is 1 to 400% larger than the (average) cross-sectional area of ​​the inner region, and more preferably 200 to 300%.

[0016] Good results are particularly obtained when the liquid region, the inner region, and the gas region each have a circular cross-sectional shape, wherein the diameter of the gas region is larger than the diameter of the inner region, and the diameter of the liquid region is the same as or larger than the diameter of the inner region, preferably larger.

[0017] In order to achieve particularly effective removal of liquid entrained in the gas phase rising from the liquid zone through the internal zone and passing through the gas zone, the gas zone according to the invention includes a demister element, preferably a demister and / or a washing liquid distributor, which is connected to a washing liquid inlet and a washing liquid outlet disposed in the gas zone.

[0018] In this embodiment, any type of demister can be used, such as a vane packdemister, a mesh demister, or a cyclone demister. A vane packdemister comprises multiple adjacent complex-formed plates, typically made of metal or plastic, with fluid channels formed between adjacent plates, for example, those forming a Z-shaped pattern when viewed vertically. This allows droplets carrying liquid to contact the surface of the plates, coalesce, and then fall as larger droplets, thus being removed from the rising gas passing through the demister. A mesh demister comprises a knitted mesh through which a gas / liquid mixture flows, causing droplets to contact the surface of the filaments, coalesce, and then fall as larger droplets, thus being removed from the gas freely moving upward through the mesh. Furthermore, a cyclone demister typically comprises a hollow cylindrical tube through which the gas / liquid mixture flows tangentially. When droplets entrained in the gas / liquid mixture are thrown against the circumferential wall of the hollow cylindrical tube by centrifugal force and discharged from the bottom of the hollow cylindrical tube from there, the gas flows freely through the hollow cylindrical tube and leaves the hollow cylindrical tube at its opposite end.

[0019] In this embodiment, the gas zone includes a washing liquid distributor connected to a washing liquid inlet and a washing liquid outlet. Preferably, the washing liquid inlet and outlet are located at different positions within the gas zone, and more preferably at different positions on the peripheral wall and / or top wall of the gas zone. Good results are obtained when the washing liquid distributor is located in the upper part of the gas zone, for example, in the region between 60% and 95% of the gas zone height when viewed vertically from the bottom to the top; the washing liquid inlet is preferably located on the top wall of the gas zone and connected to the washing liquid distributor via a pipeline (e.g., a pipe); and the washing liquid outlet is preferably located on the peripheral wall of the gas zone below the washing liquid distributor, for example, in the region between 30% and 70% of the gas zone height when viewed vertically from the bottom to the top, and connected to the washing liquid distributor via a pipeline (e.g., a pipe). The washing liquid dissolves or disperses droplets entrained in the rising gas, thereby demisting the rising gas.

[0020] To achieve good pre-separation of liquid from gas in the internal region, i.e., to increase mass transfer, the internal region according to the invention includes one or more internal components for increasing the surface-to-volume ratio of the internal region, wherein the one or more internal components have a specific surface area of ​​10 to 1,000 m². 2 / m 3 Preferably, the one or more internal components have a specific surface area of ​​50 to 500 m². 2 / m 3 More preferably 75 to 300 m 2 / m3 The optimal value is 100 to 200 m. 2 / m 3 According to the present invention, the one or more internal components are selected from structured packed beds, random packed beds, and hybrid heat exchange elements.

[0021] According to a particularly preferred embodiment of the invention, the internal zone of the reactor comprises one or more so-called cross-channel corrugated structured sheet packing beds, which are assembled from multiple corrugated sheets arranged in parallel and in contact with each other. Preferably, the corrugated metal sheets are secured to each other by a number of rods passing through the corrugated sheets perpendicular to their longitudinal sections, wherein the rods are secured by first and last corrugated sheets by washers and nuts or by bending rods. Each corrugated sheet preferably comprises multiple alternating peaks and valleys, wherein adjacent corrugated sheets are oriented such that the corrugations of adjacent corrugated sheets intersect each other in a cross-shaped manner, the corrugations extending obliquely relative to the vertical or longitudinal direction, thereby forming a continuous series of intersecting oblique channels. These channels positively influence the flow of the gas and liquid phases within the packing and promote interphase mass transfer. That is, the gas and liquid phases contact each other in the channels of the structured packing elements, thereby promoting interphase mass and heat transfer. During operation, droplets entrained in the rising gas contact the surface of the structured packing, coalesce, and then fall as large droplets, thus being removed from the rising gas. For example, the internal zone of the reactor may include one to ten, more preferably one to five, still more preferably one to three, and most preferably one or two structured packing beds arranged vertically but spaced apart from each other.

[0022] According to an alternative preferred embodiment of the invention, the internal zone of the reactor comprises one or more random packed beds, each random packed bed comprising a plurality of packing elements randomly oriented within the packing. For example, the packing elements are complex-formed rings that provide a large and uniform opening area in each ring orientation, thereby allowing high surface exposure of liquids and gases while minimizing dry zones. During operation, droplets entrained in the rising gas contact the surface of the random packed packing, coalesce, and then fall as large droplets, thus being removed from the rising gas. For example, the internal zone of the reactor may comprise one to ten, more preferably one to five, still more preferably one to three, and most preferably one or two random packed beds arranged vertically but spaced apart from each other.

[0023] According to an alternative preferred embodiment of the invention, the internal zone of the reactor includes one or more mixing heat exchange elements. Particularly good results are obtained when the internal zone of the reactor includes one or more tube bundle heat exchangers comprising a plurality of hollow tubes through which the heat transfer medium can flow, wherein the hollow tubes are bent to also serve as deflectors for fluids flowing outside and through the hollow tubes, thereby achieving fluid mixing. During operation, droplets entrained in the rising gas contact the surface of the hollow tubes, coalesce, and then fall as larger droplets, thus being removed from the rising gas. Such tube bundle heat exchangers are commercially distributed, for example, by Sulzer Chemtech Ltd. under the trade name SMR.

[0024] Furthermore, each of the internal zones may have at least one inlet on its peripheral wall, which can be connected to the feed line of the starting composition. The outlet line can then be connected to the peripheral wall or bottom wall of the liquid zone.

[0025] In a further refinement of the invention, it is proposed that the reactor further include a recirculation line that allows the liquid to recirculate between the liquid zone and the inner zone of the reactor. This allows for effective and complete mixing of the composition flowing through the inner and liquid zones. Particularly good results are obtained when the recirculation line is connected to an outlet located in the liquid zone and an inlet located in the inner zone, and optionally also to an inlet located in the liquid zone, positioned above the outlet. More specifically, it is preferred that the recirculation line is connected to an outlet located in the bottom wall of the liquid zone, and to an inlet located in the peripheral wall of the inner zone, and optionally also to an inlet located in the peripheral wall of the liquid zone. For example, the recirculation line is connected to an inlet located in the peripheral wall of the inner zone, in a region between 70% and 100% of the height of the inner zone when viewed vertically from the bottom to the top. Similarly, the recirculation line can be connected to an inlet located in the peripheral wall of the liquid zone, in a region between 30% and 70% of the height of the liquid zone when viewed vertically from the bottom to the top.

[0026] Preferably, in this embodiment, the feed line for the starting composition is merged with the recirculation line, and the merged feed / recirculation line is then introduced into an inlet located in the inner zone (and more specifically in the peripheral wall of the inner zone). Furthermore, the product outlet line preferably branches off from the recirculation line.

[0027] In order to further improve mixing efficiency and / or precisely regulate the desired operating temperature, a further improvement to the concept of the invention proposes to incorporate mixing and / or heat exchange elements in the recirculation line.

[0028] According to another particularly preferred embodiment of the invention, the reactor further includes a mixing and / or heat exchange element directly connected to and arranged below the liquid zone. This allows for optimization of mixing efficiency and regulation of optimal operating temperature in a simple construction manner. Also in this embodiment, it is preferred that the reactor further includes a recirculation line, which is preferably connected to an outlet disposed in the mixing and / or heat exchange element directly connected to the liquid zone, wherein the recirculation line is also connected to an inlet disposed in the inner zone, and optionally also to an inlet disposed in the liquid zone. Also in this embodiment, it is preferred that the recirculation line is connected to an inlet located on the peripheral wall of the inner zone, in a region between 70% and 100% of the height of the inner zone when viewed vertically from the bottom to the top. Similarly, the recirculation line may be connected to an inlet located on the peripheral wall of the liquid zone, in a region between 30% and 70% of the height of the liquid zone when viewed vertically from the bottom to the top. Furthermore, in this embodiment, it is preferred that the feed line for the starting composition is merged with the recirculation line, and the merged feed / recirculation line is then introduced into an inlet located in the inner zone (and more specifically, on the peripheral wall of the inner zone). Furthermore, the product outlet line preferably branches off from the recirculation line. However, in this embodiment, the recirculation line preferably does not include any mixing and / or heat exchange elements. In this embodiment, it is also preferred that the feed line for the starting composition is merged with the recirculation line, and the merged feed / recirculation line is then introduced into an inlet located in the liquid zone, while the product outlet line branches off from the recirculation line.

[0029] In each of the two above-described embodiments—specifically, in the embodiment where the recirculation line is directly connected to an outlet disposed in the bottom wall of the liquid zone, and in the embodiment where the recirculation line is directly connected to and arranged below the liquid zone—the mixing and / or heat exchange element can be any element that allows mixing of the liquid flowing through it and / or allows heating and / or cooling of the liquid flowing through it. For example, the mixing and / or heat exchange element is a mixing element comprising at least one mixer selected from static mixers, dynamic mixers, and jet mixers. A static mixer refers to any mixer that does not include any moving parts, and particularly does not include any rotating parts, while a dynamic mixer includes one or more moving parts, and particularly rotating parts, while a jet mixer includes a pump and an element through which liquid is injected into the mixer with high kinetic energy to create a flow pattern that achieves mixing.

[0030] In a further refinement of the invention, it is preferable that the mixing element is also heatable and / or coolable. This allows for heat compensation or provision of additional heat load, and / or homogenization of the discharged composition.

[0031] Good results are particularly obtained when the mixing and / or heat exchange elements are static mixer devices. Static mixers typically produce a mixing effect by generating turbulence due to static (i.e., non-moving) elements such as plates, rods, crossbars, baffles, spiral deflectors, grids, etc. If these elements are hollow, the heat transfer medium can flow through them, giving the corresponding static mixer heat exchange capabilities. Suitable examples of static mixers are X-type static mixers, spiral / helical static mixers, quattro static mixers, baffle-type static mixers, turbulent strip-type static mixers, and any combination of two or more of the above mixer types. X-type static mixers include deflectors in the form of rods, crossbars, plates, etc., having an X-shaped form in plan and / or side and / or cross-sectional views. Such x-type static mixers are described, for example, in WO 2010 / 066457 A1, EP 1206962 A1, EP2158027B1 and EP0655275 B1, and are commercially available from Sulzer Chemtech Ltd, Winterthur, Switzerland under the trade names SMX, SMXL and SMX plus, and from Fluitec, Neftenbach, Switzerland under the trade name CSE-X. Spiral / helical type static mixers have a helical deflector and are described, for example, in US 3,743,250 A, while quattro type static mixers include a deflector forming a chamber-like mixing section and are described, for example, in EP 2548634 B1 and EP 0815 929 B1. Baffle-type static mixers typically include longitudinal deflection devices and are described, for example, in EP 1510247 B1 and US 4,093,188 A. Turbulent strip-type static mixers comprise multiple elongated strips within a tube, each strip consisting of a series of alternating deflection panels connected sequentially by, for example, substantially triangular bridging portions. The strips are held together by these alternating bridging portions and substantially anchored to the tube's axis, with other bridging portions located near the inner wall of the tube, as described, for example, in US 4,296,779 A. Other suitable static mixers are distributed by Sulzer Chemtech AG under the trade names CompaX, SMI, KVM, SMV, and GVM, and by Stamixco AG, Wollerau, Switzerland under the trade name GVM.In view of the foregoing, it is preferred that at least one of the at least two distributors has at least one static mixer selected from an X-type static mixer, a spiral / helical type static mixer, a quattro type static mixer, a baffle type static mixer, a turbulent strip type static mixer, and any combination of two or more of the above mixer types. Most preferably, the mixing and heat exchange element is a tube bundle heat exchanger, which is commercially distributed by Sulzer Chemtech Ltd. under the trade name SMR.

[0032] According to another aspect, the present invention relates to a method for carrying out a polycondensation or depolymerization reaction, comprising the steps of: feeding a starting composition into the reactor through an inlet, discharging a product composition from the reactor through a product outlet line, and discharging gas from the reactor through a gas outlet line.

[0033] The method of the present invention involves no particular limitation on the type of starting composition. Good results are particularly obtained when the starting composition comprises monomers, oligomers, and / or polymers based on lactic acid or similar dicarboxylic acids or furanyl dicarboxylic acid. Therefore, preferably, the starting composition comprises lactic acid, lactic acid oligomers (e.g., lactide), lactic acid polymers, mixtures of lactic acid and lactic acid oligomers, mixtures of lactic acid, lactic acid oligomers and lactic acid polymers, 3-hydroxypropionic acid, 3-hydroxypropionic acid oligomers, 3-hydroxypropionic acid polymers, mixtures of 3-hydroxypropionic acid and 3-hydroxypropionic acid oligomers, mixtures of 3-hydroxypropionic acid, 3-hydroxypropionic acid oligomers and 3-hydroxypropionic acid polymers, mixtures of alkylene glycols and furanyldicarboxylic acid, oligomers of alkylene glycols and furanyldicarboxylic acid, polymers of alkylene glycols and furanyldicarboxylic acid, mixtures of alkylene glycols, furanyldicarboxylic acid and oligomers of alkylene glycols and furanyldicarboxylic acid, or mixtures of alkylene glycols, furanyldicarboxylic acid, oligomers of alkylene glycols and furanyldicarboxylic acid and polymers of alkylene glycols and furanyldicarboxylic acid. In this respect, oligomers refer to molecules containing 2 to 10 repeating monomer units, while polymers refer to molecules containing more than 10 repeating monomer units. Preferably, the furanyldicarboxylic acid is 2,4-furanyldicarboxylic acid, and more preferably 2,5-furanyldicarboxylic acid, while the alkylene glycol is preferably ethylene glycol.

[0034] In a further improvement to the concept of the present invention, it is proposed that the residence time in the liquid zone be 1 to 20 hours, and more preferably 2 to 10 hours. The residence time of the liquid in the liquid zone can be adjusted, for example, by appropriately adjusting the liquid level in the liquid zone and by appropriately selecting the cross-sectional area or diameter of the liquid zone.

[0035] Good results are particularly obtained when the gas zone includes a demister as a demisting element and / or a washing liquid distributor (connected to a washing liquid inlet and a washing liquid outlet disposed in the gas zone), wherein the washing liquid is a starting composition, or, if the starting composition is a mixture of two or more components, one, two, or all of the components in the starting mixture. In the case of polycondensation of lactic acid (optionally also containing lactic acid oligomers and / or lactic acid polymers), the washing liquid is preferably lactic acid. In the case of polycondensation of 3-hydroxypropionic acid (optionally also containing 3-hydroxypropionic acid oligomers and / or lactic acid polymers), the washing liquid is preferably 3-hydroxypropionic acid. Furthermore, in the case of polycondensation of alkylene glycols with furanyldicarboxylic acid (optionally also containing alkylene glycol / furanyldicarboxylic acid oligomers and / or alkylene glycol / furanyldicarboxylic acid polymers), the washing liquid is preferably a mixture of alkylene glycols and furanyldicarboxylic acid, such as a mixture of ethylene glycol and 2,5-furanyldicarboxylic acid.

[0036] According to another embodiment of the invention, the gas zone includes a blade demister, a mesh demister, or a cyclone demister as a demister.

[0037] According to a particularly preferred embodiment of the invention, the reactor for carrying out the method further includes a recirculation line connected to an outlet disposed in the liquid zone or an outlet disposed in the mixing and / or heat exchange element, wherein the recirculation line is also connected to an inlet disposed in the internal zone, and optionally also connected to an inlet disposed in the liquid zone. Preferably, the weight ratio of the recirculated stream to the feed stream is from 1:1 to 200:1. Particularly good results are obtained when the weight ratio of the recirculated stream to the feed stream is from 20:1 to 150:1, more preferably from 30:1 to 100:1, still more preferably from 40:1 to 80:1, and most preferably from about 50:1 to 70:1.

[0038] Furthermore, it is preferred that during the method according to the invention, a catalyst is contained in the reactor, wherein the catalyst preferably comprises a rare earth metal (e.g., yttrium) or a transition metal (e.g., zirconium, titanium) or an alkaline earth metal (e.g., magnesium or calcium) or other metals (e.g., aluminum, tin, etc.), the catalyst being used for condensation reactions and / or for depolymerization reactions.

[0039] This patent application is subsequently described by way of example with reference to advantageous embodiments and accompanying drawings.

[0040] It is shown that: Figure 1 A schematic diagram of a reactor according to one embodiment of the present invention is shown.

[0041] Figure 1The reactor 10 shown, viewed from bottom to top, includes a mixing and heat exchange element 12, a liquid zone 14, an internal zone 16, and a gas zone 18. Furthermore, the reactor 10 (and more specifically, the internal zone 16) includes an inlet 20, and the reactor 10 also includes a product outlet line 22 and a gas outlet line 24 disposed at the top of the gas zone 18. The liquid zone 14, internal zone 16, and gas zone 18 are each hollow cylindrical containers with a circular cross-sectional area, wherein the diameters of the liquid zone 14 and gas zone 18 are the same, while the diameters of the liquid zone 14 and gas zone 18 are larger than the diameter of the internal zone 16. The internal zone 16 includes a structured packed bed 26, and the gas zone 18 includes a washing liquid distributor 28 connected to a washing liquid inlet 30 and a washing liquid outlet 32.

[0042] Furthermore, reactor 10 includes a recirculation line 34 connected to an outlet 36 located at the bottom of mixing and heat exchange element 12, wherein recirculation line 34 is also connected to an inlet 38 located in liquid zone 16. Additionally, reactor 10 includes a feed line 40 for the starting composition, which merges with recirculation line 34, and the merged feed / recirculation line 42 is then introduced into inlet 20 of inner zone 16. Furthermore, product outlet line 22 branches off from recirculation line 34.

[0043] During operation, the starting composition (e.g., a lactic acid composition) is fed through inlet 20 into the inner zone 16 of the reactor along with liquid recirculated via lines 40 and 42. In this inner zone, the mixture is contacted with rising gas in a structured packed bed 26. In the inner zone 16, entrained droplets in the rising gas are pre-separated from the rising gas as these droplets contact the surface of the structured packing 26, coalesce, and then fall as large droplets, thus being removed from the rising gas. As the gas carrying residual droplets rises further into the gas zone 18, the liquid containing the starting composition falls into the liquid zone 14, where the lactic acid reacts in a polycondensation reaction to produce water, lactic acid oligomers, and polylactic acid. The liquid product falls from the liquid zone 14 to the mixing and heat exchange element 12 and is discharged via outlet 36 to the recirculation line 34. A portion of the product composition is discharged via product outlet line 22, while the remainder is recirculated to liquid zone 14 via inlet 38. After mixing with the initial mixture fed via feed line 40, the mixture enters the inner zone 16 of reactor 10 via the combined feed / recirculation line 42 and inlet 20. The rising gas is further purified from the entrained liquid in gas zone 18, where partial liquid-gas separation is achieved by droplet settling due to gravity. Due to the relatively low gas flow in gas zone 18 (which is larger than inner zone 16), and partly due to the dissolution / dispersion of droplets in the washing liquid, the washing liquid flows through washing inlet line 30, through washing liquid distributor 28, into gas zone 18, and exits from gas zone 18 via washing liquid outlet line 32. The thus purified gas exits reactor 10 via gas outlet line 24.

[0044] Figure Labels 10 Reactors 12 Mixing and heat exchange elements 14. Liquid Zone of the Reactor 16. Internal zone of the reactor 18. Gas Zone of the Reactor 20 Reactor inlet 22 Product outlet pipeline 24 Gas outlet pipeline 26. Structured packed bed 28. Detergent dispenser 30 Washing liquid inlet 32. Detergent outlet 34 Recirculation Line 36. Outlet of mixing and heat exchange elements 38. Entrance to the liquid zone 40 Feed line 42 Combined feed / recirculation pipeline.

Claims

1. A reactor (10), particularly for performing a polycondensation or depolymerization reaction, said reactor comprising at least one inlet (20), at least one product outlet line (22), a liquid zone (14), an internal zone (16), and a gas zone (18) including at least one gas outlet line (24), wherein the internal zone (16) is disposed above the liquid zone (14), wherein the gas zone (18) is disposed above the internal zone (16), and wherein the gas zone (18) has a larger cross-sectional area than the internal zone (16), wherein the gas zone (18) includes a demister connected to a washing liquid inlet (30) disposed in the gas zone (18) and a washing liquid outlet (32) disposed in the gas zone (18), and wherein the internal zone (16) includes one or more internal components selected from structured packed beds (26), random packed beds, and mixing heat exchange elements for increasing the surface-to-volume ratio within the internal zone (16), wherein said one or more internal components have a specific surface area of ​​10 to 1,000 m². 2 / m 3 .

2. The reactor (10) according to claim 1, wherein the gas zone (18) is directly connected to the inner zone (16), and the inner zone (16) is directly connected to the liquid zone (14).

3. The reactor (10) according to claim 1 or 2, wherein the liquid zone (14), the internal zone (16) and the gas zone (18) each have a circular cross-sectional shape.

4. The reactor (10) according to any one of the preceding claims, wherein the one or more internal components have a specific surface area of ​​50 to 500 m² / m³, preferably 75 to 300 m² / m³, and most preferably 100 to 200 m² / m³.

5. The reactor (10) according to any one of the preceding claims, wherein the reactor (10) further comprises a recirculation line (34) connected to an outlet disposed in the liquid zone (14) and an inlet disposed in the inner zone (16), and optionally also connected to an inlet (38) disposed in the liquid zone (14) and arranged above the outlet, wherein preferably a mixing and / or heat exchange element (12) is disposed in the recirculation line (34).

6. The reactor (10) according to any one of claims 1 to 4, wherein the reactor (10) further comprises a mixing and / or heat exchange element directly connected to and arranged below the liquid zone (14), wherein the reactor (10) preferably further comprises a recirculation line (34) connected to an outlet (36) disposed in the mixing and / or heat exchange element (12) and an inlet disposed in the inner zone (16), and optionally also connected to an inlet (38) disposed in the liquid zone (14).

7. The reactor (10) according to claim 5 or 6, wherein the mixing and / or heat exchange element (12) is a mixing element (12) including at least one mixer selected from static mixers, dynamic mixers and jet mixers, wherein the mixing element (12) is preferably also heatable and / or coolable.

8. A method for carrying out a polycondensation reaction or a depolymerization reaction, comprising the following steps: The starting composition is fed into the reactor (10) of any one of the preceding claims through inlet (20), the product composition is discharged from the reactor through product outlet line (22), and the gas is discharged from the reactor through gas outlet line (24).

9. The method of claim 8, wherein the starting composition comprises lactic acid, lactic acid oligomers, lactic acid polymers, mixtures of lactic acid and lactic acid oligomers, mixtures of lactic acid, lactic acid oligomers and lactic acid polymers, 3-hydroxypropionic acid, 3-hydroxypropionic acid oligomers, 3-hydroxypropionic acid polymers, mixtures of 3-hydroxypropionic acid and 3-hydroxypropionic acid oligomers, mixtures of 3-hydroxypropionic acid, 3-hydroxypropionic acid oligomers and 3-hydroxypropionic acid polymers, mixtures of alkylene glycols and furanyldicarboxylic acid, oligomers of alkylene glycols and furanyldicarboxylic acid, polymers of alkylene glycols and furanyldicarboxylic acid, mixtures of alkylene glycols, furanyldicarboxylic acid and oligomers of alkylene glycols and furanyldicarboxylic acid, or mixtures of oligomers of alkylene glycols, furanyldicarboxylic acid, oligomers of alkylene glycols and furanyldicarboxylic acid and polymers of alkylene glycols and furanyldicarboxylic acid.

10. The method according to claim 8 or 9, wherein the residence time in the liquid zone (14) is 1 to 20 hours, and preferably 2 to 10 hours.

11. The method according to any one of claims 8 to 10, wherein the gas zone (18) comprises a demister and / or a washing liquid distributor (28) as a demisting element, the washing liquid distributor being connected to a washing liquid inlet (30) disposed in the gas zone (18) and a washing liquid outlet (32) disposed in the gas zone (18), wherein the washing liquid is the starting composition, or, if the starting composition is a mixture of two or more components, is one, two or all of the components in the starting mixture.

12. The method according to claim 11, wherein the washing liquid is lactic acid, 3-hydroxypropionic acid, or a mixture of ethylene glycol and 2,5-furandicarboxylic acid.

13. The method according to any one of claims 8 to 12, wherein the reactor (10) further comprises a recirculation line (34) connected to an outlet disposed in the liquid zone (14) or to an outlet (36) disposed in the mixing and / or heat exchange element (12), wherein the recirculation line (34) is also connected to an inlet disposed in the inner zone (16), and optionally also connected to an inlet (38) disposed in the liquid zone (14).

14. The method according to claim 13, wherein the weight ratio of the recycled stream to the feed stream is 1:1 to 200:1, preferably 20:1 to 150:1, more preferably 30:1 to 100:1, still more preferably 40:1 to 80:1, and most preferably 50:1 to 70:

1.

15. The method according to any one of claims 8 to 14, wherein a catalyst is contained in the reactor (10), wherein the catalyst preferably comprises a rare earth metal such as yttrium, or a transition metal such as zirconium, titanium, or an alkaline earth metal such as magnesium or calcium, or another metal such as aluminum, tin, etc., said catalyst being used for condensation reaction and / or depolymerization reaction.

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