Method for the continuous manufacture of taurine

Abstract

A method for the continuous manufacture of taurine, comprising at least one of (a) – (c): (a) reacting an ethylene oxide and an alkali metal bisulfite to obtain a first intermediate product stream comprising an alkali metal isethionate; (b) reacting the alkali metal isethionate from the first intermediate product stream with ammonia to obtain a second intermediate product stream comprising an alkali metal taurate; and (c) converting the alkali metal taurate from the second intermediate product stream to obtain taurine and at least one by-product, wherein the by- product is suitable for reacting sulfur dioxide to alkali metal bisulfite, and separating the at least one by-product from the taurine to obtain at least one by-product stream comprising the at least one by-product and a product stream comprising the taurine; and an apparatus for the continuous manufacture of taurine.

Description

[0001] Method for the continuous manufacture of taurine

[0002] Cross-Reference to Related Application

[0003] The present application is related and claims right of priority to EP24208427.5 and EP24208417.6, which were filed on 23 October 2024 in the European Patent Office and are incorporated by reference in its entirety herein.

[0004] Field of the invention

[0005] The present application relates generally to a method for the continuous manufacture of taurine, as well as an apparatus for said method.

[0006] Background

[0007] Taurine is a naturally occurring amino sulfonic acid found in various tissues throughout the body and in many animals. It plays several critical roles, including supporting cardiovascular function, brain health, and the development of the central nervous system and muscles in infants. Taurine also acts as an antioxidant and is involved in bile salt formation, osmoregulation, and maintaining eye health. While it is naturally synthesized in the body from other amino acids, it can also be obtained from dietary sources like meat and fish. Taurine is commonly used in energy drinks, supplements, and pharmaceuticals due to its potential benefits in enhancing physical performance, supporting heart health, and promoting mental focus. In the animal nutrition industry, taurine is essential for cats, who cannot synthesize it naturally. Taurine is most commonly produced starting from ethylene oxide, which various steps have been described in detail before. Most commercial productions of taurine so far have been in batch. While advances towards a commercially viable continuous production of taurine have been made, it remains a need to improve aspects as to provide a reliable continuous production of taurine with high yield, that allows for particularly good process control, reduces waste, reduces energy consumption, and allows for the recycling of by-products. Summary

[0008] In example aspects, a method for the continuous manufacture of taurine , comprising at least one of the steps of (a) - (c):

[0009] (a) reacting an ethylene oxide and an alkali metal bisulfite to obtain a first intermediate product stream comprising an alkali metal isethionate;

[0010] (b) reacting the alkali metal isethionate from the first intermediate product stream with ammonia to obtain a second intermediate product stream comprising an alkali metal taurate; and

[0011] (c) converting the alkali metal taurate from the second intermediate product stream to obtain taurine and at least one by-product, wherein the by-product is suitable for reacting sulfur dioxide to alkali metal bisulfite, and separating the at least one by-product from the taurine to obtain at least one by-product stream comprising the at least one by-product and a product stream comprising the taurine;

[0012] and

[0013] (d) optionally reacting the at least one by-product from the at least one by-product stream with sulfur dioxide to obtain a recycle educt stream comprising alkali metal bisulfite; and (e) optionally crystallizing the taurine from the product stream and separating the crystallized taurine from a resulting mother liquor.

[0014] As used herein, the term “comprising” is to be construed as encompassing both “including” and “consisting of’, both meanings being specifically intended, and hence individually disclosed, example embodiments according to the present invention

[0015] As used herein, the articles “a” and “an” preceding an element or component are intended to be nonrestrictive regarding the number of instances (i.e. occurrences) of the element or component. Therefore, “a” or “an” is to be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously meant to be singular. As used herein, the term “about” modifying the quantity of a substance, ingredient, component, or parameter employed refers to variation in the numerical quantity that can occur, for example, through typical measuring and handling procedures, e.g., liquid handling procedures used for making concentrates or solutions. Furthermore, variation can occur from inadvertent error in measuring procedures, differences in the manufacture, source, or purity of the ingredients employed to carry out the methods, and the like. In one embodiment, the term “about” means within 10% of the reported numerical value. In a more specific embodiment, the term “about” means within 5% of the reported numerical value.

[0016] As used herein, the term “stream” refers to a fluid that may be transportable via pipes. For example the term “stream” may refer to a gas, liquid or supercritical fluid.

[0017] It has surprisingly been found that the method according to example aspects of the invention may possess any number of benefits including, inter alia, improvements in the yield, process control, waste reduction, energy consumption, recyclability of by-products, and product crystallization. Particularly, the method according to example aspects of the invention allows to produce taurine in food quality in a fully continuous process, having less than 1 molar equivalents of waste alkali metal bisulfite per molar equivalent of produced taurine. It is to be understood that advantages relating to specific example embodiments of individual method step may also be achieved individually for methods that include these example embodiments but provide alternative previous or subsequent steps.

[0018] According to one preferred example embodiment, the method comprises at least the step (a). According another preferred example embodiment, the method comprises at least the step (b). According another preferred example embodiment, the method comprises at least the step (c). According another preferred example embodiment, the method comprises at least the step (a) and (b). According another preferred example embodiment, the method comprises at least the step (b) and (c). According another preferred example embodiment, the method comprises at least the step (a) and (c). According another preferred example embodiment, the method comprises at least the step (a), (b), and (c).

[0019]

[0020] Reaction oxide and alkali

[0021] According to example aspects of the invention, the method may comprise the step of (a) reacting an ethylene oxide and an alkali metal bisulfite to obtain a first intermediate product stream comprising an alkali metal isethionate.

[0022] It has surprisingly been found that with the further specific example embodiments described below, that the alkali metal isethionate can be obtained with particularly good yield and selectivity, reducing by-products and allowing for good process control. It has been particularly found that by providing the reaction continuously, for example in a continuous flow reactor, reaction conditions such as elevated temperature and pressure may be used that allow for shorter reaction times and higher selectivity.

[0023] Ethylene oxide is a commonly known chemical with the chemical formula C2H4O, also known as oxirane, epoxyethane, or oxacyclopropane. Ethylene oxide is a cyclic ether, thereby being an epoxide. Ethylene oxide is a colorless gas under ambient conditions.

[0024] Alkali metal bisulfite are commonly known salts comprising an alkali metal cation and a bisulfite anion with the general formula XHSO3, with X being an alkali metal. Alkali metals may for example be Li, Na, K, Rb, or Cs. Preferably, the alkali metal may be Li, Na, or K. More preferably, the alkali metal may be Na or K, particularly Na. In one example embodiment, the alkali metal bisulfite is sodium bisulfite (NaHSCL). It has been found that sodium bisulfite is particularly preferred as it is readily available in good purity and the resulting sodium isethionate is particularly preferred for performing further steps (b) and / or (c).

[0025] Alkali metal isethionate is a salt comprising an alkali metal cation and an isethionate anion with the general formula XOSO2CH2CH2OH, with X being an alkali metal as defined before. The isethionate anion is based on isethionic acid, also known as 2 -Hydroxy ethane- 1 -sulfonic acid. Alkali metals may be as defined for the alkali metal bisulfite. It is to be understood that selecting a particular alkali metal bisulfite, for example sodium bisulfite, yields the corresponding alkali metal isethionate, for example sodium isethionate when performing reaction step (a).

[0026] Particularly, the first intermediate product stream may be obtained as continuous stream. This means that the reaction of the ethylene oxide and the alkali metal bisulfite is preformed continuously so that the first product stream comprising the alkali metal isethionate can be continuously obtained. In one example embodiment, the ethylene oxide is provided together with water in a first educt stream. In an alternative example embodiment, the ethylene oxide is provided without water in the first educt stream. The water and the ethylene oxide may be provided as dispersion, solution, or combination thereof. In one example embodiment, the ethylene oxide is comprised in the first educt stream in a concentration of > 1 wt.-% to < 100 wt.-% based on the total amount of ethylene oxide and water, preferably > 30 wt.-% to < 100 wt.-%, more preferably > 60 wt.-% to < 100 wt.-%.

[0027] In one example embodiment, the alkali metal bisulfite is provided as aqueous solution in a second educt stream. In one example embodiment the alkali metal bisulfite is comprised in the second educt stream in an concentration of > 1 wt.-% to < 60 wt.-% based on the total weight of the second educt stream, preferably > 5 wt.-% to < 50 wt.-%, more preferably > 10 wt.-% to < 40 wt.-%.

[0028] In one example embodiment, the alkali metal bisulfite is sodium bisulfite and is comprised in the second educt stream in a concentration of > 1 wt.-% to < 60 wt.-% based on the total weight of the second educt stream, preferably > 5 wt.-% to < 50 wt.-%, more preferably > 10 wt.-% to < 40 wt.-%.

[0029] In one example embodiment the ethylene oxide is provided for reaction with the alkali metal bisulfite in a molar ratio of ethylene oxide and alkali metal bisulfite in the range of > 1:2 to < 1:0.4, preferably > 1:1.8 to < 1:0.5, preferably > 1:1.6 to < 1:0.6, preferably > 1:1.5 to < 1:0.7, preferably > 1:1.4 to < 1:0.8, preferably > 1:1.3 to < 1:0.85, preferably > 1:1.2 to < 1:0.9. In one example embodiment, the ethylene oxide and the alkali metal bisulfite are reacted continuously in a continuous flow reactor, such as for example a plug flow reactor, to continuously obtain the first intermediate product stream comprising an alkali metal isethionate. Preferably, the ethylene oxide is provided continuously as the first educt stream and the alkali metal bisulfite is provided continuously as the second educt stream. In one example embodiment the first and second educt stream are mixed together in the continuous flow reactor. In one example embodiment, the ethylene oxide and the alkali metal bisulfite are reacted at a temperature in the range of > 5 °C to < 200 °C, preferably > 10 °C to < 190 °C, preferably > 15 °C to < 180 °C, preferably > 20 °C to < 170 °C, preferably > 30 °C to < 160 °C, preferably > 40 °C to < 150 °C, preferably > 50 °C to < 140 °C, preferably > 60 °C to < 130 °C, for example 80 °C.

[0030] In one example embodiment, the ethylene oxide and the alkali metal bisulfite are reacted at a pressure in the range of > 0 bar to < 100 bar, preferably > 1 bar to < 90 bar, preferably > 1.5 bar to < 80 bar, preferably > 2 bar to < 70 bar, preferably > 2.5 bar to < 60 bar, preferably > 3 bar to < 50 bar, preferably > 3.5 bar to < 40 bar, preferably > 4 bar to < 25 bar, preferably > 4.5 bar to < 15 bar, preferably > 4.8 bar to < 10 bar, preferably > 5 bar to < 8 bar, for example 5.5 bar. In one example embodiment, the ethylene oxide and the alkali metal bisulfite are reacted for a duration in the range of > 10 s to < 7200 s, preferably > 15 s to < 5000 s, preferably > 20 s to < 4000 s, preferably > 25 s to < 3000 s, preferably > 30 s to < 2800 s, preferably > 35 s to < 2600 s, preferably > 40 s to < 2400 s, preferably > 45 s to < 2200 s, preferably > 50 s to < 2000 s, preferably > 60 s to < 1800 s, preferably > 70 s to < 1600 s, preferably > 80 s to < 1400 s, preferably > 90 s to < 1200 s, preferably > 100 s to < 1000 s, preferably > 110 s to < 800 s, preferably > 120 s to < 600 s, preferably > 130 s to < 400 s, preferably > 140 s to < 200 s, for example 150 s.

[0031] It has particularly been found that with the disclosed temperature, pressure and reaction time, the selectivity of the reaction can be particularly advantageous.

[0032] In one example embodiment, the ethylene oxide and the alkali metal bisulfite are reacted under conditions to obtain a yield of alkali metal isethionate in the range of > 1% to < 100% based on the theoretical yield of alkali metal isethionate based on the amount of ethylene oxide provided, preferably > 50% to < 100%, preferably > 80% to < 100%, preferably > 90% to < 100%, preferably > 95% to < 100%, preferably > 96% to < 100%, preferably > 97% to < 100%, preferably > 98% to < 100%, preferably > 99% to < 100%, for example 98%. As waste-product, ethylene glycol may be obtained and comprised in the first intermediate product stream comprising alkali metal isethionate.

[0033] In one example embodiment, the ethylene oxide and the alkali metal bisulfite are reacted under the presence of a catalyst. Preferably the catalyst is an alkali metal hydroxide for example NaOH. In one example embodiment the catalyst is provided as aqueous NaOH solution as first catalyst stream. The first catalyst stream may be mixed continuously with the first and / or second educt stream. In one example embodiment, the catalyst may be provided to the reaction of the ethylene oxide and the alkali metal bisulfite in a molar ratio to ethylene oxide of > 0.01:1 to < 0.20:1, preferably > 0.02:1 to < 0.15:1, preferably > 0.03:1 to < 0.10:1, preferably > 0.04:1 to < 0.09:1, preferably > 0.05:1 to < 0.08:1, preferably > 0.06:1 to < 0.07:1.

[0034] In an alternative example embodiment, the ethylene oxide and the alkali metal bisulfite are reacted without a catalyst.

[0035] The reaction according to step (a) is an exothermic reaction. In one example embodiment, temperature is in step (a) is controlled with a heat exchanger. For example, method step (a) may be used with a heat exchanger to heat up a heat exchange fluid, such as water or steam. The heated heat exchange fluid may be used in other method steps of the present method with corresponding heat exchangers.

[0036] In one example embodiment, the ethylene oxide is provided continuously as the first educt stream and the alkali metal bisulfite is sodium bisulfite and is provided continuously as the second educt stream,

[0037] wherein the ethylene oxide is provided for reaction with the sodium bisulfite in a molar ratio of ethylene oxide to sodium bisulfite in the range of > 1 :2 to < 1 :0.4, preferably > 1 : 1.8 to < 1 :0.5, preferably > 1:1.6 to < 1:0.6, preferably > 1:1.5 to < 1:0.7, preferably > 1:1.4 to < 1:0.8, preferably > 1:1.3 to < 1:0.85, preferably > 1:1.2 to < 1:0.9,

[0038] wherein the first and second educt stream are mixed together in the continuous flow reactor and reacted at a temperature in the range of > 5 °C to < 200 °C, preferably > 10 °C to < 190 °C, preferably > 15 °C to < 180 °C, preferably > 20 °C to < 170 °C, preferably > 30 °C to < 160 °C, preferably > 40 °C to < 150 °C, preferably > 50 °C to < 140 °C, preferably > 60 °C to < 130 °C, for example 80 °C,

[0039] and a pressure in the range of > 0 bar to < 100 bar, preferably > 1 bar to < 90 bar, preferably > 1.5 bar to < 80 bar, preferably > 2 bar to < 70 bar, preferably > 2.5 bar to < 60 bar, preferably > 3 bar to < 50 bar, preferably > 3.5 bar to < 40 bar, preferably > 4 bar to < 25 bar, preferably > 4.5 bar to < 15 bar, preferably > 4.8 bar to < 10 bar, preferably > 5 bar to < 8 bar, for example 5.5 bar,

[0040] and for a duration in the range of in the range of > 10 s to < 7200 s, preferably > 15 s to < 5000 s, preferably > 20 s to < 4000 s, preferably > 25 s to < 3000 s, preferably > 30 s to < 2800 s, preferably > 35 s to < 2600 s, preferably > 40 s to < 2400 s, preferably > 45 s to < 2200 s, preferably > 50 s to < 2000 s, preferably > 60 s to < 1800 s, preferably > 70 s to < 1600 s, preferably > 80 s to < 1400 s, preferably > 90 s to < 1200 s, preferably > 100 s to < 1000 s, preferably > 110 s to < 800 s, preferably > 120 s to < 600 s, preferably > 130 s to < 400 s, preferably > 140 s to < 200 s, for example 150 s.

[0041] In one example embodiment, the ethylene oxide is provided continuously as the first educt stream and the alkali metal bisulfite is sodium bisulfite and is provided continuously as the second educt stream,

[0042] wherein the ethylene oxide is provided for reaction with the sodium bisulfite in a molar ratio of ethylene oxide to sodium bisulfite in the range of > 1:1.4 to < 1:0.8, preferably > 1:1.3 to < 1:0.85, preferably > 1:1.2 to < 1:0.9,

[0043] wherein the first and second educt stream are mixed together in the continuous flow reactor and reacted at a temperature in the range of > 20 °C to < 170 °C, preferably > 30 °C to < 160 °C, preferably > 40 °C to < 150 °C, preferably > 50 °C to < 140 °C, preferably > 60 °C to < 130 °C, for example 80 °C,

[0044] and a pressure in the range of > 3 bar to < 50 bar, preferably > 3.5 bar to < 40 bar, preferably > 4 bar to < 25 bar, preferably > 4.5 bar to < 15 bar, preferably > 4.8 bar to < 10 bar, preferably > 5 bar to < 8 bar, for example 5.5 bar,

[0045] and for a duration in the range of in the range of > 90 s to < 1200 s, preferably > 100 s to < 1000 s, preferably > 110 s to < 800 s, preferably > 120 s to < 600 s, preferably > 130 s to < 400 s, preferably > 140 s to < 200 s, for example 150 s.

[0046] In one example embodiment, the ethylene oxide is provided continuously as the first educt stream and the alkali metal bisulfite is sodium bisulfite and is provided continuously as the second educt stream,

[0047] wherein the ethylene oxide is provided for reaction with the sodium bisulfite in a molar ratio of ethylene oxide to sodium bisulfite in the range of preferably > 1:1.3 to < 1:0.85, preferably > 1:1.2 to < 1:0.9,

[0048] wherein the first and second educt stream are mixed together in the continuous flow reactor and reacted at a temperature in the range of > 60 °C to < 130 °C, for example 80 °C, and a pressure in the range of > 5 bar to < 8 bar, for example 5.5 bar,

[0049] and for a duration in the range of in the range of > 140 s to < 200 s, for example 150 s.

[0050] According to one particularly preferred example embodiment, the ethylene oxide is provided continuously as the first educt stream and the alkali metal bisulfite is sodium bisulfite and is provided continuously as the second educt stream, wherein the sodium bisulfite is comprised in the second educt stream in a concentration of about 30 wt.-%, wherein the ethylene oxide is provided for reaction with the sodium bisulfite in a molar ratio of ethylene oxide to sodium bisulfite of about 1:0.91, wherein aqueous NaOH solution is mixed continuously with the first and / or second educt stream in a molar ratio to ethylene oxide of about 0.065, wherein the first and second educt stream are mixed together in the continuous flow reactor and reacted at a temperature of about 80 °C, and a pressure of about 5.5 bar, and for a duration of about 150 s.

[0051] (b) Reaction of alkali metal isethionate with ammonia

[0052] According to example aspects of the invention, the method may comprise the step of

[0053] (b) reacting the alkali metal isethionate from the first intermediate product stream with ammonia to obtain a second intermediate product stream comprising an alkali metal taurate. It has surprisingly found that with the further specific example embodiments described below, the alkali metal taurate can be obtained with particularly good yield and selectivity, reducing by-products and allowing for good process control. It has been particularly found that by providing the reaction continuously, for example in a continuous flow reactor, reaction conditions such as elevated temperature and pressure may be used that allow for shorter reaction times and higher selectivity. Particularly, with the various example embodiments the formation of by-product such as alkali metal ditaurate or alkali metal tritaurate may be reduced, or the formation of alkali metal tritaurate as by-product may even be avoided entirely.

[0054] Alkali metal taurate is a commonly known salt comprising an alkali metal cation and taurate anion with the general formula XO3SCH2CH2NH2, with X being an alkali metal as defined before. The taurate anion is based on taurine, also known as 2-aminoethanesulfonic acid. Alkali metals may be as defined for the alkali metal bisulfite. It is to be understood that selecting a particular alkali metal bisulfite, for example sodium bisulfite, yields the corresponding alkali metal isethionate, which in turn yield the corresponding alkali metal taurate, for example sodium taurate when performing reaction step (b) based on sodium isethionate.

[0055] Alkali metal di taurate (also alkali metal ditaurinate) is known as salt comprising two alkali metal cations and a ditaurate di anion. The ditaurate anion is a dimer of taurate with the general formula NH (CthCFhChSO'k. Alkali metal tritaurate (also alkali metal tritaurinate) is known as salt comprising three alkali metal cations and a tritaurate tri anion. The tritaurate anion is a trimer of taurate with the general formula N(CH2CH2O2SO )3.

[0056] Particularly, the first intermediate product stream may be provided as continuous stream from method step (a).

[0057] In one example embodiment, the alkali metal isethionate is provided together with water in the first intermediate product stream. In one example embodiment the alkali metal isethionate is comprised in the first intermediate product stream in an concentration of > 1 wt.% to < 60wt.% based on the amount of the first intermediate product stream, preferably > 5 wt% to < 50 wt%, more preferably > 10 wt% to < 40 wt%. In one example embodiment, the alkali metal isethionate is sodium isethionate and is comprised in the first intermediate product stream in a concentration > 1 wt.% to < 60wt.% based on the amount of the first intermediate product stream, preferably > 5 wt% to < 50 wt%, more preferably > 10 wt% to < 40 wt%, for example 10 wt.-%. In one example embodiment the first intermediate product stream comprises byproduct from method step (a), in particular ethylene glycol, in an concentration of > 0 wt% to < 20 wt% based on the amount of the first intermediate product stream, preferably > 0.1 wt% to < 10 wt%, more preferably > 0.2 wt% to < 5 wt%.

[0058] In one example embodiment, the first intermediate product stream may be used directly as it is obtained from method step (a). In an alternative example embodiment, the first intermediate product stream may further be diluted, for example with water.

[0059] In one example embodiment, the ammonia may be provided as third educt stream as pure ammonia for example as ammonia gas or ammonia liquid. In an alternative example embodiment, ammonia may be provided as third educt stream as aqueous ammonia solution. In one example embodiment, the alkali metal isethionate is provided for reaction with the ammonia in a molar ratio of alkali metal isethionate to ammonia in the range of < 1:0.1 to > 1:100, preferably < 1:0.5 to > 1:90, preferably < 1:1 to > 1:80, preferably < 1:1.5 to > 1:70, preferably < 1 :2 to > 1 :60, preferably < 1 :2.5 to > 1:50, preferably < 1 :3 to > 1 :45, preferably < 1:3.5 to > 1:40, preferably < 1:4 to > 1:35, preferably < 1:4.5 to > 1:30, preferably < 1:5 to > 1:25, preferably < 1:5.5 to > 1:20, preferably < 1:6 to > 1:18, preferably < 1:6.5 to > 1:17, preferably < 1:7 to > 1:16. In one example embodiment, the ammonia is provided for reaction with the alkali metal isethionate in excess when considering a stochiometric reaction of 1 mol alkali metal isethionate with 1 mol ammonia.

[0060] In one example embodiment, the alkali metal isethionate and the ammonia are reacted continuously in a continuous flow reactor, such as for example a plug flow reactor, to continuously obtain the second intermediate product stream comprising an alkali metal taurate. Preferably, the alkali metal isethionate is provided continuously as the first intermediate product stream and the ammonia is provided continuously as the third educt stream. In one example embodiment the first intermediate product stream and the third educt stream are mixed together in the continuous flow reactor.

[0061] In one example embodiment, the alkali metal isethionate and the ammonia are reacted at a temperature in the range of > 160 °C to < 400 °C, preferably > 170 °C to < 390 °C, preferably > 180 °C to < 380 °C, preferably > 190 °C to < 370 °C, preferably > 200 °C to < 360 °C, preferably > 210 °C to < 350 °C, preferably > 220 °C to < 340 °C, preferably > 230 °C to < 330 °C, preferably > 240 °C to < 320 °C, preferably > 250 °C to < 310 °C, for example 270 °C or 260 °C.

[0062] In one example embodiment, the alkali metal isethionate and the ammonia are reacted at a pressure in the range of > 1 bar to < 250 bar, preferably > 10 bar to < 230 bar, preferably > 20 bar to < 210 bar, preferably > 30 bar to < 200 bar, preferably > 40 bar to < 190 bar, preferably > 50 bar to < 180 bar, preferably > 60 bar to < 170 bar, preferably > 70 bar to < 160 bar, preferably > 75 bar to < 150 bar, preferably > 80 bar to < 140 bar, preferably > 85 bar to < 130 bar, preferably > 90 bar to < 120 bar, for example 100 bar or 110 bar.

[0063] In one example embodiment, the alkali metal isethionate and the ammonia are reacted for a duration in the range of > 30 s to < 14400 s, preferably > 60 s to < 12000 s, preferably > 120 s to < 8000 s, preferably > 180 s to < 6400 s, preferably > 240 s to < 5800 s, preferably > 300 s to < 5000 s, preferably > 360 s to < 4600 s, preferably > 420 s to < 4300 s, preferably > 480 s to < 4000 s, preferably > 540 s to < 3700 s, preferably > 600 s to < 3400 s, preferably > 660 s to < 3100 s, preferably > 720 s to < 3000 s, preferably > 780 s to < 2900 s, preferably > 840 s to < 2800 s, preferably > 900 s to < 2700 s, for example 2400 s.

[0064] In one example embodiment, the alkali metal isethionate and the ammonia are reacted until a yield of the alkali metal taurate in the range of > 10% to < 100% based on the theoretical yield of alkali metal taurate based on the amount of alkali metal isethionate provided is reached, preferably > 35% to < 95%, preferably > 50% to < 92%, preferably > 65% to < 90%, preferably > 67% to < 87%, preferably > 70% to < 85%.

[0065] In one example embodiment, the alkali metal isethionate and the ammonia are reacted under conditions that the second intermediate product stream comprises a residual amount of metal isethionate as by-product based on the amount of metal isethionate in the first intermediate product stream of > 0% to < 90% based on the theoretical yield of alkali metal taurate based on the amount of alkali metal isethionate provided, preferably > 2% to < 70%, preferably > 3% to < 40%, preferably > 4% to < 30%, preferably > 5% to < 20%, preferably > 6% to < 15%. It has particularly been found that with the disclosed temperature, pressure and reaction time, and low yield the selectivity of the reaction can be particularly advantageous. Particularly, it has been found that the formation of tritaurate may be prevented entirely.

[0066] In one example embodiment, the alkali metal isethionate and the ammonia are reacted under the presence of a catalyst. Preferably the catalyst is selected from metal hydroxide catalysts or alkali metal hydroxide catalysts, such as LiOH, KOH, NaOH, Mg(0H)2, Al(0H)3, titanium (IV) catalysts such as Ti(SO3)2, or from sodium catalysts such as NaOH, NaHSOs, and Na2SO4. More preferably the catalyst is selected from NaOH, NaHSOs, and Na2SO4ln one example embodiment the catalyst is provided as aqueous solution as second catalyst stream. The second catalyst stream may be mixed continuously with the first intermediate product stream. In one example embodiment, the catalyst may be provided to the reaction of the metal isethionate and the ammonia in a molar ratio to metal isethionate of > 0.01 : 1 to < 1 : 1, preferably > 0.02: 1 to < 0.9:1, preferably > 0.025:1 to < 0.80:1, preferably > 0.03:1 to < 0.70:1, preferably > 0.035:1 to < 0.60:1, preferably > 0.04:1 to < 0.50:1.

[0067] In an alternative example embodiment, the metal isethionate and the ammonia are reacted without a catalyst. In one example embodiment, excess ammonia can be removed from the second intermediate product stream comprising an alkali metal taurate and continuously be recycled as ammonia in third educt stream. It is to be understood that the third educt stream may partially comprise the recycled ammonia from the second intermediate product stream and additional ammonia so the total amount of ammonia provided in step (b) is sufficient for the reaction. In one example embodiment the ammonia is removed from the second intermediate product stream by flashing the second intermediate product stream and separating the resulting gaseous ammonia from the remaining liquid comprising the alkali metal taurate.

[0068] In one example embodiment, the alkali metal isethionate is sodium isethionate and is provided continuously as the first intermediate product stream and ammonia is provided as the third educt stream,

[0069] wherein the sodium isethionate is provided for reaction with the ammonia in a molar ratio of sodium isethionate to ammonia in the range of < 1 :0.1 to > 1 : 100, preferably < 1 :0.5 to > 1 :90, preferably < 1 : 1 to > 1 :80, preferably < 1 : 1.5 to > 1 :70, preferably < 1 :2 to > 1 :60, preferably < 1:2.5 to > 1:50, preferably < 1:3 to > 1:45, preferably < 1:3.5 to > 1:40, preferably < 1:4 to > 1:35, preferably < 1:4.5 to > 1:30, preferably < 1:5 to > 1:25, preferably < 1:5.5 to > 1:20, preferably < 1 :6 to > 1:18, preferably < 1 :6.5 to > 1 : 17, preferably < 1:7 to > 1:16, wherein the first intermediate product stream and the third educt stream are mixed together in the continuous flow reactor and reacted at a temperature in the range of > 160 °C to < 400 °C, preferably > 170 °C to < 390 °C, preferably > 180 °C to < 380 °C, preferably > 190 °C to < 370 °C, preferably > 200 °C to < 360 °C, preferably > 210 °C to < 350 °C, preferably > 220 °C to < 340 °C, preferably > 230 °C to < 330 °C, preferably > 240 °C to < 320 °C, preferably > 250 °C to < 310 °C, for example 270 °C or 260 °C,

[0070] and a pressure in the range of > 1 bar to < 250 bar, preferably > 10 bar to < 230 bar, preferably > 20 bar to < 210 bar, preferably > 30 bar to < 200 bar, preferably > 40 bar to < 190 bar, preferably > 50 bar to < 180 bar, preferably > 60 bar to < 170 bar, preferably > 70 bar to < 160 bar, preferably > 75 bar to < 150 bar, preferably > 80 bar to < 140 bar, preferably > 85 bar to < 130 bar, preferably > 90 bar to < 120 bar, for example 100 bar or 110 bar,

[0071] and for a duration in the range of > 30 s to < 14400 s, preferably > 60 s to < 12000 s, preferably > 120 s to < 8000 s, preferably > 180 s to < 6400 s, preferably > 240 s to < 5800 s, preferably > 300 s to < 5000 s, preferably > 360 s to < 4600 s, preferably > 420 s to < 4300 s, preferably > 480 s to < 4000 s, preferably > 540 s to < 3700 s, preferably > 600 s to < 3400 s, preferably > 660 s to < 3100 s, preferably > 720 s to < 3000 s, preferably > 780 s to < 2900 s, preferably > 840 s to < 2800 s, preferably > 900 s to < 2700 s, for example 2400 s.

[0072] In one example embodiment, the alkali metal isethionate is sodium isethionate and is provided continuously as the first intermediate product stream and ammonia is provided as the third educt stream,

[0073] wherein the sodium isethionate is provided for reaction with the ammonia in a molar ratio of sodium isethionate to ammonia in the range of < 1:3.5 to > 1:40, preferably < 1:4 to > 1:35, preferably < 1 :4.5 to > 1 :30, preferably < 1 :5 to > 1 :25, preferably < 1 :5.5 to > 1 :20, preferably < 1:6 to > 1:18, preferably < 1:6.5 to > 1:17, preferably < 1:7 to > 1:16,

[0074] wherein the first intermediate product stream and the third educt stream are mixed together in the continuous flow reactor and reacted at a temperature in the range of > 200 °C to < 360 °C, preferably > 210 °C to < 350 °C, preferably > 220 °C to < 340 °C, preferably > 230 °C to < 330 °C, preferably > 240 °C to < 320 °C, preferably > 250 °C to < 310 °C, for example 270 °C or 260 °C,

[0075] and a pressure in the range of > 60 bar to < 170 bar, preferably > 70 bar to < 160 bar, preferably > 75 bar to < 150 bar, preferably > 80 bar to < 140 bar, preferably > 85 bar to < 130 bar, preferably > 90 bar to < 120 bar, for example 100 bar or 110 bar,

[0076] and for a duration in the range > 480 s to < 4000 s, preferably > 540 s to < 3700 s, preferably > 600 s to < 3400 s, preferably > 660 s to < 3100 s, preferably > 720 s to < 3000 s, preferably > 780 s to < 2900 s, preferably > 840 s to < 2800 s, preferably > 900 s to < 2700 s, for example 2400 s.

[0077] In one example embodiment, the alkali metal isethionate is sodium isethionate and is provided continuously as the first intermediate product stream and ammonia is provided as the third educt stream,

[0078] wherein the sodium isethionate is provided for reaction with the ammonia in a molar ratio of sodium isethionate to ammonia in the range of < 1:6 to > 1:18, preferably < 1:6.5 to > 1:17, preferably < 1 :7 to > 1:16, wherein the first intermediate product stream and the third educt stream are mixed together in the continuous flow reactor and reacted at a temperature in the range of > 240 °C to < 320 °C, preferably > 250 °C to < 310 °C, for example 270 °C or 260 °C,

[0079] and a pressure in the range of > 90 bar to < 120 bar, for example 100 bar or 110 bar, and for a duration in the range > 840 s to < 2800 s, preferably > 900 s to < 2700 s, for example 2400 s.

[0080] According to one particularly preferred example embodiment the alkali metal isethionate is sodium isethionate and is provided continuously as the first intermediate product stream and ammonia is provided as the third educt stream, wherein the sodium isethionate is provided for reaction with the ammonia in a molar ratio of sodium isethionate to ammonia of about 1:16, wherein the first intermediate product stream and the third educt stream are mixed together in the continuous flow reactor and reacted at a temperature of about 260 °C, and a pressure of about 120 bar, and for a duration of about 2400 s.

[0081] (c) Conversion of alkali metal taurate to taurine and by-product

[0082] According to example aspects of the invention, the method may comprise the step of

[0083] (c) converting the alkali metal taurate from the second intermediate product stream to obtain taurine and at least one by-product, wherein the by-product is suitable for reacting sulfur dioxide to alkali metal bisulfite, and separating the at least one by-product from the taurine to obtain at least one by-product stream comprising the at least one by-product and a product stream comprising the taurine.

[0084] It has surprisingly been found that with the further specific example embodiments described below, the taurate can be obtained with good yield and selectivity, reducing waste-products and allowing for good separation of the obtained by-products, as well as reusing the by-products in the method.

[0085] It is to be understood that selecting a particular alkali metal taurate, for example sodium taurate, yields a by-product suitable for reacting sulfur dioxide to the corresponding alkali metal bisulfite, such as sodium bisulfite.

[0086] In one example embodiment, the alkali metal taurate is converted to the taurine and the at least one by-product in one or more reaction steps. Preferably, the alkali metal taurate is converted to the taurine in one or two reaction steps. In one alternative example embodiment, the alkali metal taurate is converted to taurine in two reaction steps, wherein preferably in the first reaction step a first by-product is formed which is separated in a first by-product stream and in the second reaction step a second by-product is formed which is separated in a second byproduct stream.

[0087] In an alternative example embodiment, the alkali metal taurate from the second intermediate product stream is converted to the taurine in one reaction step, wherein in the one reaction step one by-product is formed which is separated in one by-product stream.

[0088] It will be appreciated that byproducts in the form of alkali metal salts, such as alkali metal isethionate, alkali metal ditaurate, and alkali metal tritaurate, may undergo the same conversion to the corresponding acid as the alkali metal taurate to taurine. Correspondingly, according to one example embodiment the product stream may comprise isethionic acid, ditaurine, and / or tritaurine. On the other hand, according to one example embodiment, waste-products may be removed in step (c). For example, ethylene glycol may be removed as waste-product stream.

[0089] (cl) Conversion of alkali metal taurate to taurine and by-product via ion exchange According to one alternative example embodiment, method step (c) may be preformed according to method step (cl), comprising the steps of

[0090] (cl a) converting the alkali metal taurate from the second intermediate product stream with ammonium anions in an ion exchange column to ammonium taurate comprised in a third intermediate product stream and alkali metal cations comprised in a first by-product stream, (clb) removing ammonia in a second by-product stream from the third intermediate product stream to form the product stream comprising taurine.

[0091] It is to be understood that the ammonia from the second by-product stream and the alkali metal cations from the first by-product stream together are suitable for reacting sulfur dioxide to alkali metal bisulfite, as will be provided in detail below when describing further method step (d). It has surprisingly been found that by converting the alkali metal taurate in an ion exchange column to ammonium taurate in a first step and afterwards removing ammonia to form taurine may allow for a particularly stable process, higher yield and selectivity. It has been found that these advantages may be particularly present when comparing the method according to the present example embodiment to a direct acidification of alkali metal taurate to taurine in an ion exchange column. While the example embodiment requires a two step process, it has been found that these may be conducted in a comparably stable manner, allowing for a continuous process.

[0092] Preferably, the alkali metal taurate is provided continuously as the second intermediate product stream.

[0093] (cla) ion exchange

[0094] In one example embodiment in step (cla), the alkali metal taurate from the second intermediate product stream is led into the ion exchange column, wherein the ion exchange column is filled with an acidic cation exchange resin loaded with the ammonium anions. In said example embodiment, the alkali metal taurate is passed through the ion exchange column and the alkali metal cations are exchanged with the ammonium anions, thereby yielding ammonium taurate in the third intermediate product stream leaving the ion exchange column and alkali metal cations bound to the acidic cation exchange resin of the ion exchange column as first by-product stream. It will be appreciated that, even though the alkali metal cations are at this point bound to the ion exchange resin, they are considered as by-product stream as the resin or the anions can be removed from the column.

[0095] In one example embodiment, step (cla) is performed continuously alternating between at least two ion exchange columns, wherein during the time the step is performed with one of the ion exchange columns, the other ion exchange columns are regenerated. Accordingly, the process can continuously be switched between the columns. In one example embodiment, at least two sets of multiple ion exchange columns are used altematingly.

[0096] In one example embodiment, the ion exchange column is considered to be exhausted once the yield of ammonium taurate based on the alkali metal taurate at the exit of the column is < 60%, preferably < 70%, preferably < 80%, more preferably < 90%.

[0097] According to one example embodiment, regeneration of the ion exchange column may be achieved by passing an ammonium salt solution through the ion exchange column. For example, ammonium chloride, ammonium sulfate, and / or ammonium bisulfite may be used for regeneration, yielding the regenerated column and corresponding alkali metal salt solution from the alkali metal bound to the ion exchange resin. Preferably, ammonium bisulfite may be used for regeneration of the columns. In case ammonium bisulfite is used, alkali metal bisulfite is obtained. The alkali metal cations obtained as first by-product stream, bound to the ion exchange resin, are thereby suitable for reacting ammonium bisulfite to alkali metal bisulfite. This step will be provided in more detail with respect to method step (d).

[0098] In one example embodiment, the second intermediate product stream led into the ion exchange column in step (cla) comprises alkali metal taurate in an amount of > 1 wt.-% to < 65 wt.-% based on the volume of the water, preferably > 5 wt.-% to < 30 wt.-%, more preferably > 10 wt.-% to < 25 wt.-%.

[0099] In one example embodiment, the alkali metal taurate is sodium taurate and the second intermediate product stream led into the ion exchange column in step (cla) comprises sodium taurate in an amount of > 2 wt.-% to < 25 wt.-% based on weight of the second intermediate product stream, preferably > 5 wt.-% to < 20 wt.-%, more preferably > 10 wt.-% to < 15 wt.-%.

[0100] In one example embodiment, the alkali metal taurate is sodium taurate and the second intermediate product stream led into the ion exchange column in step (cla) comprises unreacted sodium isethionate in an amount of > 0 wt.-% to < 5 wt.-% based on weight of the second intermediate product stream, preferably > 1 wt.-% to < 2 wt.-%, and / or the second intermediate product stream led into the ion exchange column in step (cla) comprises disodium ditaurate in an amount of > 0 wt.-% to < 5 wt.-% based on weight of the second intermediate product stream, preferably > 3 wt.-% to < 4 wt.-%. In one example embodiment, the alkali metal taurate is sodium taurate and the second intermediate product stream led into the ion exchange column in step (cla) further comprises ethylene glycol obtained as waste-product during reaction step (a).

[0101] In one example embodiment, step (cla) is performed under conditions to obtain a yield of the ammonium taurate in the range of > 65% to < 100% based on the theoretical yield of ammonium taurate based on the amount of alkali metal taurate provided, preferably > 70% to < 99%, preferably > 75% to < 97%, preferably > 80% to < 96%, preferably > 85% to < 95%, preferably > 87% to < 93%, preferably > 89% to < 91%, for example 90%. It may be understood that according to one example embodiment, the second intermediate product stream obtained in step (b) may directly be used in method step (c). Alternatively, the second intermediate product stream may further be diluted, for example with water.

[0102] In one example embodiment, the ion exchange column has a length in the range of > 0.5 m to < 5 m, preferably > 0.75 m to < 4 m, more preferably > 1 m to < 3 m.

[0103] In one example embodiment, the second intermediate product stream is led into the ion exchange column with a flow rate given in Volume of the resin per hour (BV / h) of > 10 BV / h to < 100 BV / h, > preferably 20 BV / h to < 80 BV / h, more preferably > 30 BV / h to < 60 BV / h, for example 40 BV / h.

[0104] It will be appreciated that byproducts in the form of alkali metal salts, such as alkali metal isethionate, alkali metal ditaurate, and alkali metal tritaurate, may undergo the same conversion to the ammonium salt as the alkali metal taurate to ammonium taurate. Correspondingly, according to one example embodiment the third intermediate product stream may comprise ammonium isethionate, di-ammonium ditaurate, and / or tri-ammonium tritaurate. On the other hand, neutral waste-products may not react further in this method step and still be present in the second intermediate product stream. For example, ethylene glycol may still be comprised in the second intermediate product stream when performing the step according to (cla).

[0105] (clb) ammonia removal

[0106] Ammonia may be removed in step (clb) in a second by-product stream from the third intermediate product stream to form the product stream comprising taurine.

[0107] Particularly, the third intermediate product stream is heated in step (clb) in order to decompose ammonium taurate to taurine and ammonia, removing ammonia as second by-product stream to from the product stream comprising taurine.

[0108] In one example embodiment, the third intermediate product stream is heated to a temperature in the range of > 20 °C to < 150 °C, preferably > 80 °C to < 140 °C, preferably > 85 °C to < 130 °C, > 90 °C to < 120 °C, > 95 °C to < 110 °C, for example 100 °C. Ammonia may then be expelled from the solution and may be removed as second by-product stream under reduced, normal, or increased pressure. The temperature may be achieved via a heat exchanger, wherein the heat exchange fluid has been heated by the reaction in method step (a).

[0109] The ammonia obtained as second by-product stream, is suitable for reacting with sulfur dioxide to ammonium bisulfite. This step will be provided in more detail with respect to method step (d). It will be appreciated that the ammonia obtained as second by-product stream, is suitable for reacting with sulfur dioxide to ammonium bisulfite, which together with the alkali metal cations obtained as first by-product stream, may be reacted to the alkali metal bisulfite. Thus, the by-products of the present example embodiment are suitable for reacting with sulfur dioxide to alkali metal bisulfite. This step will be provided in more detail with respect to method step (d).

[0110] It will be appreciated that byproducts in the form of ammonium salts, such as ammonium isethionate, di-ammonium ditaurate, and tri-ammonium tritaurate, may undergo the same conversion to the corresponding acid as the ammonium taurate to taurine. Correspondingly, according to one example embodiment the product stream may comprise isethionic acid, ditaurine, and / or tritaurine. On the other hand, neutral waste-products may not react further in this method step and still be present in the product stream. For example, ethylene glycol may still be comprised in the product stream when performing the step according to (clb).

[0111] (c2) Conversion of alkali metal taurate to taurine and by-product via bipolar membrane electrodialysis

[0112] According to one alternative example embodiment, method step (c) may be preformed according to the method step (c2), comprising the step of

[0113] (c2) converting the alkali metal taurate from the second intermediate product stream with a bipolar membrane electrodialysis to taurine forming the product stream and alkali metal hydroxide in a by-product stream.

[0114] It is to be understood that the alkali metal hydroxide from the by-product stream is suitable for reacting sulfur dioxide to alkali metal bisulfite, as will be provided in detail below when describing further method step (d).

[0115] Bipolar membrane electrodialysis (BMED) is an electrochemical method that make use of bipolar membranes, usually in combination with other ion exchange membranes in various setups. Bipolar membranes are generally membranes that allow for the exchange of ions of different polarity, mainly the exchange of H+in one direction and OH' in the other direction while not allowing the exchange of other anions or cations. In sum, a bipolar membrane may therefore be understood as membrane between two aqueous chambers that generates H+in one chamber and OH' in the other, while being impermeable otherwise.

[0116] Preferably, the alkali metal taurate is provided continuously as the second intermediate product stream for the bipolar membrane electrodialysis.

[0117] According to a first preferred alternative example embodiment, the bipolar membrane electrodialysis is configured so that alkali metal cations from the second intermediate product stream fed into the bipolar membrane electrodialysis are removed through a cation exchange membrane and the taurinate anions from the second intermediate product stream fed into the bipolar membrane electrodialysis are removed through an anion exchange membrane. According to the example embodiment, the bipolar membrane electrodialysis is further configured so that the alkali metal cations passed through the cation exchange membrane are contacted with hydroxide anions obtained from a bipolar membrane, and removed as alkali metal hydroxide in the by-product stream. According to the example embodiment, the bipolar membrane electrodialysis is further configured so that the taurate anions passed through the anion exchange membrane are contacted with hydrogen cations obtained from a bipolar membrane, and removed as taurine in the product stream.

[0118] According to a second preferred alternative example embodiment, the second intermediate product stream is adjusted to a pH in the range of 5-6 and / or the isoelectric point of taurine. It is to be understood that at this pH, the alkali metal taurate is present as zwitterionic taurine in solution. According to the second example embodiment, the bipolar membrane electrodialysis is configured so that alkali metal cations from the second intermediate product stream fed into the bipolar membrane electrodialysis are removed through a cation exchange membrane and anions of by-products, such as ditaurate, tritaurate, or isethionate, from the second intermediate product stream fed into the bipolar membrane electrodialysis are removed through an anion exchange membrane. According to the example embodiment, the bipolar membrane electrodialysis is further configured so that the alkali metal cations passed through the cation exchange membrane are contacted with hydroxide anions obtained from a bipolar membrane, and removed as alkali metal hydroxide in the by-product stream. According to the example embodiment, the bipolar membrane electrodialysis is further configured so that the anions of by-products, such as ditaurate, tritaurate, or isethionate, passed through the anion exchange membrane are contacted with hydrogen cations obtained from a bipolar membrane, and removed as acids, such as ditaurine, tritaurine, or isethionic acid in an acidic by-product stream. Further according to the example embodiment, the bipolar membrane electrodialysis is configured so that the taurine does not pass the anion or cation exchange membrane, and removed as taurine in the product stream.

[0119] Advantageously this may allow recycling of the organic by-products and overall increase yield and purity of the product stream.

[0120] According to one example embodiment, the acidic by-product stream may be used to adjust the pH of the second intermediate product stream to a pH value in the range of 5 to 6 and / or the isoelectric point of taurine according to the second alternative preferred example embodiment. Using the acidic by-product stream for pH adjustment has the advantage that no additional acid needs to be introduced into the reaction.

[0121] According to one example embodiment, the acidic by-product stream can be reintroduced into the reaction step (b). Particularly, the acidic by-product stream may be reintroduced into the reaction step (b) after pH adjustment with a base. According to one example embodiment, the pH adjustment may be performed using the alkali metal hydroxide obtained as by-product stream in the bipolar membrane electrodialysis. This may advantageously influence the chemical equilibrium of the reaction in step (b) and reduce waste product.

[0122] According to one example embodiment, the bipolar membrane electrodialysis comprises at least one chamber A contacted by a bipolar membrane (BP) and an anion exchange membrane (AEM), at least one chamber B contacted by an anion exchange membrane (AEM) and a cation exchange membrane (CEM), and at least one chamber C, contacted by a cation exchange membrane (CEM) and a bipolar membrane (BP).

[0123] As used herein, the term “chamber” is to be understood as enclosure allowing for the required chemical reaction, wherein it will be appreciated that “chamber” includes inlets and outlets for the corresponding streams entering and leaving the reaction. The bipolar membrane electrodialysis may comprise at least one anode chamber AC comprising an anode and contacting a membrane, preferably selected from a bipolar membrane and a cation exchange membrane. Furthermore, the bipolar membrane electrodialysis may comprise at least one cathode chamber CC comprising a cathode and contacting a membrane, preferably selected from a bipolar membrane and a cation exchange membrane. The anode and cathode may be connected with a voltage source.

[0124] According to one example embodiment the at least one chamber A, one chamber B, and one chamber C are arranged between the anode chamber AC and the cathode chamber CC.

[0125] According to one example embodiment, the bipolar membrane electrodialysis comprises at least one set S of three chambers, comprising one chamber A, one chamber B, and one chamber C, wherein the chamber A and B are contacted by the same anion exchange membrane, and wherein chamber B and C are contacted by the same cation exchange membrane.

[0126] According to example aspects of the present invention, in case two chambers are contacted by the same membrane, it is to be understood that the two chamber share said membrane. That is, the membrane is located directly between the two chambers, constituting the end of one chamber and the beginning of the other.

[0127] In other words, according to one example embodiment, the bipolar membrane electrodialysis comprises a set S comprising three chambers A, B, and C, that are connected via their corresponding joint membranes. It results that in the set S according to the example embodiment, anions can pass through the anion exchange membrane between chamber A and B and cations can pass through the anion exchange membrane between chamber B and C. In other words, the set has a order of membranes and chambers as follows: (BP) A (AEM) B (CEM) C (BP).

[0128] Using the aforementioned set in the bipolar membrane electrodialysis according to the first preferred alternative example embodiment as compared to other setups, for example comprising only two different chambers, surprisingly allows to also separate uncharged waste-products from the product stream. This may be particularly advantageous for the further reaction steps and recycling of mother liquor. For example, it has surprisingly been found that with this setup, ethylene glycol can be removed as waste product stream. Using the aforementioned set in the bipolar membrane electrodialysis according to the second preferred alternative example embodiment as compared to other setups, for example comprising only two different chambers, surprisingly allows to also separate acidic by-product from the product stream. This may be particularly advantageous for the overall yield as the by-products may be reintroduced in the process. For example, it has surprisingly been found that with this setup, isethionic acid, ditaurine and tritaurine can be removed as acidic by-product stream. According to one example embodiment, the set S is arranged between the anode chamber AC and the cathode chamber, wherein chamber A of set S is closer to the anode chamber AC than the cathode chamber CC and / or chamber C of set S is closer to the cathode chamber CC than the anode chamber AC.

[0129] According to one example embodiment, the bipolar membrane electrodialysis comprises at least one chamber A contacted by a bipolar membrane (BP) and an anion exchange membrane (AEM), at least one chamber B contacted by an anion exchange membrane (AEM) and a cation exchange membrane (CEM), and at least one chamber C, contacted by a cation exchange membrane (CEM) and a bipolar membrane (BP),

[0130] wherein the bipolar membrane electrodialysis comprise at least one anode chamber AC comprising an anode and contacting a membrane, preferably selected from a bipolar membrane and a cation exchange membrane, and at least one cathode chamber CC comprising a cathode and contacting a membrane, preferably selected from a bipolar membrane and a cation exchange membrane,

[0131] wherein the bipolar membrane electrodialysis comprises at least one set S of three chambers, comprising one chamber A, one chamber B, and one chamber C, wherein the chamber A and B are contacted by the same anion exchange membrane, and wherein chamber B and C are contacted by the same cation exchange membrane,

[0132] wherein the set S is arranged between the anode chamber AC and the cathode chamber CC, wherein chamber A of set S is closer to the anode chamber AC than the cathode chamber CC and / or chamber C of set S is closer to the cathode chamber CC than the anode chamber AC. According to one example embodiment the membrane contacted by the anode chamber is a bipolar membrane and the membrane contacted by the cathode chamber is a bipolar membrane, wherein the bipolar membrane contacted by the anode chamber is the same as the bipolar membrane contacted by chamber A of set S, and wherein the bipolar membrane contacted by the cathode chamber is the same as the bipolar membrane contacted by chamber C of set S. A resulting order of membranes and chambers may for example be as follows: AC (BP) A (AEM) B (CEM) C (BP) CC.

[0133] According to an alternative example embodiment the membrane contacted by the anode chamber is a cation exchange membrane, wherein a further chamber C is arranged between the anode chamber and chamber A of the set S, wherein the cation exchange membrane contacted by the anode chamber is the same as the cation exchange membrane contacted by the further chamber C and the bipolar membrane contacted by further chamber C is the same as the bipolar membrane contacted by chamber A of the set S.

[0134] Additionally, according to said alternative example embodiment the membrane contacted by the cathode chamber is a cation exchange membrane, wherein a further chamber A is arranged between the chamber C of the set S and the cathode chamber, and wherein a further chamber B is arranged between the further chamber A and the cathode chamber, wherein the cation exchange membrane contacted by the cathode chamber is the same as the cation exchange membrane contacted by the further chamber B, the an anion exchange membrane contacted by the further chamber B is the same as the anion exchange membrane contacted by the further chamber A, and the bipolar membrane contacted by the further chamber A is the same as the bipolar membrane contacted by chamber C of the set S.

[0135] It has surprisingly been found that with the above setup, the bipolar membrane electrodialysis has a better performance as compared to a different setup with the same number of chambers. It has been found that with the above setup, the number of bipolar membranes with respect to the total amount of chambers can be reduced. Particularly, the bipolar membranes are comparably expensive when and may have a higher resistance as compared to cation and anion exchange membranes. Accordingly, reducing the number of bipolar membranes while maintaining the overall number of chambers allows for better performance of the electrodialysis.

[0136] A resulting order of membranes and chambers may for example be as follows: AC (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) CC. According to one example embodiment, the bipolar membrane electrodialysis comprises a plurality of sets S, connected to each other via corresponding joint bipolar membranes. Particularly, the chamber C of a first set S is contacted by the same bipolar membrane as chamber A of a following set S. Accordingly, a stack of sets S may be formed wherein each chamber C is followed by a chamber A of the next set S, sharing the corresponding bipolar membrane. As a result, the stack may have a repeating sequence of chambers ABC, such as for example ABCABCABC and so on. It will be understood that the first set S and the last set S in the stack are only contacted with one further set S, wherein sets S in the middle of the stack are contacted with two sets S each. In other words, the bipolar membrane electrodialysis may have an order of membranes and chambers as follows: (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) C (BP) and so on. According to one example embodiment the plurality of sets S consists of a number n of sets S, wherein n is in the range of > 2 to < 500, preferably > 3 to < 450, more preferably > 4 to < 400, more preferably > 5 to < 350, more preferably > 10 to < 300, more preferably > 50 to < 250, more preferably > 100 to < 200. According to one example embodiment, the plurality of sets S is arranged between the anode chamber AC and the cathode chamber, wherein chamber A of each set S is closer to the anode chamber AC than the cathode chamber CC and / or chamber C of each set S is closer to the cathode chamber CC than the anode chamber AC.

[0137] According to one example embodiment the membrane contacted by the anode chamber is a bipolar membrane and the membrane contacted by the cathode chamber is a bipolar membrane, wherein the bipolar membrane contacted by the anode chamber is the same as the bipolar membrane contacted by chamber A of the set S closest to the anode chamber, and wherein the bipolar membrane contacted by the cathode chamber is the same as the bipolar membrane contacted by chamber C of the set S closest to the anode chamber.

[0138] A resulting order of membranes and chambers may for example be as follows: AC [S]nCC or more specific AC [(BP) A (AEM) B (CEM) C (BP)]nCC, for example for n = 3 AC (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) C (BP) CC.

[0139] According to an alternative example embodiment the membrane contacted by the anode chamber is a cation exchange membrane, wherein a further chamber C is arranged between the anode chamber and chamber A of the set S closest to the anode chamber, wherein the cation exchange membrane contacted by the anode chamber is the same as the cation exchange membrane contacted by the further chamber C and the bipolar membrane contacted by further chamber C is the same as the bipolar membrane contacted by chamber A of the set S closest to the anode chamber.

[0140] Additionally, according to said alternative example embodiment the membrane contacted by the cathode chamber is a cation exchange membrane, wherein a further chamber A is arranged between the chamber C of the set S closest to the cathode chamber and the cathode chamber, and wherein a further chamber B is arranged between the further chamber A and the cathode chamber, wherein the cation exchange membrane contacted by the cathode chamber is the same as the cation exchange membrane contacted by the further chamber B, the an anion exchange membrane contacted by the further chamber B is the same as the anion exchange membrane contacted by the further chamber A, and the bipolar membrane contacted by the further chamber A is the same as the bipolar membrane contacted by chamber C of the set S closest to the cathode chamber.

[0141] It has surprisingly been found that with the above setup, the bipolar membrane electrodialysis has a better performance as compared to a different setup with the same number of chambers. It has been found that with the above setup, the number of bipolar membranes with respect to the total amount of chambers can be reduced. Particularly, the bipolar membranes are comparably expensive when and may have a higher resistance as compared to cation and anion exchange membranes. Accordingly, reducing the number of bipolar membranes while maintaining the overall number of chambers allows for better performance of the electrodialysis.

[0142] A resulting order of membranes and chambers may for example be as follows: AC (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) CC. A resulting order of membranes and chambers may for example be as follows: : AC (CEM) C [S]nA (AEM) B (CEM) CC or more specific AC (CEM) C [(BP) A (AEM) B (CEM) C (BP)]nA (AEM) B (CEM) CC, for example for n = 3 AC (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) CC. According to one example embodiment, the second intermediate product stream is fed into each chamber B of the bipolar membrane electrodialysis and water is fed into each chamber A and each chamber C. According to one example embodiment, a voltage is applied between the anode and the cathode.

[0143] When conducting step (c2) according to the first preferred alternative example embodiment, particularly by applying a voltage to the anode and cathode of the bipolar membrane electrodialysis, alkali metal taurate in each chamber B is split into alkali metal cations and taurate anions, wherein the alkali metal cations pass the anion exchange membrane contacting chamber B in the direction of the anode into a neighboring chamber A and the taurate anions pass the cation exchange membrane contacting chamber B in the direction of the cathode into a neighboring chamber C. Accordingly, the alkali metal taurate is removed from the second intermediate product stream fed into each chamber B, resulting in a waste-product stream comprising uncharged waste-products. Furthermore, hydrogen cations (protons) are released from each bipolar membrane into each chamber A contacting the bipolar membrane in direction of the cathode. The released hydrogen cations may react with the taurate anions passed through the anion exchange membrane into chamber A forming taurine. Accordingly, taurine is obtained in each chamber A, resulting in the product stream. Furthermore, hydroxide anions are released from each bipolar membrane into each chamber C contacting the bipolar membrane in direction of the anode. The released hydroxide anions may react with the alkali metal cations passed through the cation exchange membrane into chamber C forming alkali metal hydroxide. Accordingly, alkali metal hydroxide is obtained in each chamber C, resulting in the by-product stream.

[0144] It will be appreciated that byproduct comprised in the product stream in the form of alkali metal salts, such as alkali metal isethionate, alkali metal ditaurate, and alkali metal tritaurate, may undergo the same conversion to the corresponding acid as the alkali metal taurate to taurine. Correspondingly, according to one example embodiment the product stream may comprise isethionic acid, ditaurine, and / or tritaurine. On the other hand, neutral waste-products may not react further in this method step and will retain in the neutral waste product stream. For example, ethylene glycol may still be retained in the neutral waste product stream when performing the step according to (c2). When conducting step (c2) according to the second preferred alternative example embodiment, particularly by applying a voltage to the anode and cathode of the bipolar membrane electrodialysis, alkali metal cations from the second intermediate product stream fed into chamber B pass the anion exchange membrane contacting chamber B in the direction of the anode into a neighboring chamber A and the anions of by-products, such as ditaurate, tritaurate, or isethionate, pass the cation exchange membrane contacting chamber B in the direction of the cathode into a neighboring chamber C. Accordingly, the taurine remains in the stream together with uncharged waste-products and is removed from chamber B as product stream. Furthermore, hydrogen cations (protons) are released from each bipolar membrane into each chamber A contacting the bipolar membrane in direction of the cathode. The released hydrogen cations may react with the anions of by-products, such as ditaurate, tritaurate, or isethionate, passed through the anion exchange membrane into chamber A forming organic acids, such as ditaurine, tritaurine, or isethionic acid, which are removed from chamber A as acidic by-product stream. Furthermore, hydroxide anions are released from each bipolar membrane into each chamber C contacting the bipolar membrane in direction of the anode. The released hydroxide anions may react with the alkali metal cations passed through the cation exchange membrane into chamber C forming alkali metal hydroxide. Accordingly, alkali metal hydroxide is obtained in each chamber C, resulting in the by-product stream.

[0145] It will be appreciated that byproduct comprised in the product stream in the form of alkali metal salts, such as alkali metal isethionate, alkali metal ditaurate, and alkali metal tritaurate, as compared to the alkali metal taurine are not at their isoelectric point in the pH range adjusted according to the second preferred alternative example embodiment. Thus, they undergo the same conversion to the corresponding acid passing through the anion exchange membrane, while taurine maintains in chamber B. Correspondingly, according to one example embodiment the product stream may comprise isethionic acid, ditaurine, and / or tritaurine.

[0146] According to one example embodiment, particularly according to the first preferred alternative example embodiment, the product stream is adjusted to a pH in the range of 5-6 and / or the isoelectric point of taurine, and subjected to an electrodialysis (ED) step, resulting in cleaned product stream and a third by-product stream. It is to be understood that at this pH, the alkali metal taurate is present as zwitterionic taurine in solution. Electrodialysis in this context is to be understood as electrochemical method making use of ion exchange membranes without bipolar membranes.

[0147] According to one example embodiment, the electrodialysis is configured so that the taurine from the product stream adjusted to a pH in the range of 5-6 and / or the isoelectric point of taurine is fed into the electrodialysis so that anions of by-products, such as ditaurate, tritaurate, or isethionate, are removed from the product stream through an anion exchange membrane. Advantageously this may allow recycling of the organic by-products additionally to the removal of neutral waste-products by the BMED, overall increasing yield and purity of the product stream.

[0148] According to one example embodiment, the electrodialysis comprises at least one chamber D contacted by an anion exchange membrane (AEM) and a cation exchange membrane (CEM) and at least one chamber E contacted by a cation exchange membrane (CEM) and an anion exchange membrane (AEM).

[0149] The electrodialysis may comprise at least one anode chamber AC comprising an anode and contacting an anion exchange membrane, preferably a cation exchange membrane. Furthermore, the electrodialysis may comprise at least one cathode chamber CC comprising a cathode and contacting an anion exchange membrane, preferably a cation exchange membrane. The anode and cathode may be connected with a voltage source.

[0150] According to one example embodiment the at least one chamber D and one chamber E are arranged between the anode chamber AC and the cathode chamber CC.

[0151] According to one example embodiment, the bipolar membrane electrodialysis comprises at least one set S* of two chambers, comprising a chamber D and a chamber E, wherein the chamber D and E same anion exchange membrane. According to example aspects of the present invention, in case two chambers are contacted by the same membrane, it is to be understood that the two chambers share said membrane. That is, the membrane is located directly between the two chambers, constituting the end of one chamber and the beginning of the other.

[0152] In other words, according to one example embodiment, the electrodialysis comprises a set S* comprising two chambers D and E that are connected via their corresponding joint membranes. It results that in the set S according to the example embodiment, anions can pass through the anion exchange membrane between chamber D and E. In other words, the set has a order of membranes and chambers as follows: (CEM) D (AEM) E (CEM).

[0153] According to one example embodiment, the set S* is arranged between the anode chamber AC and the cathode chamber, wherein chamber D of set S* is closer to the anode chamber AC than the cathode chamber CC and chamber E of set S* is closer to the cathode chamber CC than the anode chamber AC.

[0154] A resulting order of membranes and chambers may for example be as follows: AC (CEM) D (AEM) E (CEM) CC.

[0155] According to one example embodiment, the electrodialysis comprises a plurality of sets S*, connected to each other via corresponding joint cationic exchange membranes. Particularly, the chamber E of a first set S* is contacted by the same cation exchange membrane as chamber D of a following set S. Accordingly, a stack of sets S may be formed wherein each chamber E is followed by a chamber D of the next set S, sharing the corresponding cation exchange membrane. As a result, the stack may have a repeating sequence of chambers DE, such as for example DEDEDE and so on. It will be understood that the first set S and the last set S in the stack are only contacted with one further set S, wherein sets S in the middle of the stack are contacted with two sets S each. In other words, the electrodialysis may have an order of membranes and chambers as follows: (CEM) D (AEM) E (CEM) D (AEM) E (CEM) D (AEM) E (CEM) and so on. According to one example embodiment the plurality of sets S* consists of a number n of sets S*, wherein n is in the range of > 2 to < 500, preferably > 3 to < 450, more preferably > 4 to < 400, more preferably > 5 to < 350, more preferably > 10 to < 300, more preferably > 50 to < 250, more preferably > 100 to < 200.

[0156] According to one example embodiment, the plurality of sets S* is arranged between the anode chamber AC and the cathode chamber, wherein chamber D of each set S* is closer to the anode chamber AC than the cathode chamber CC and chamber E of each set S* is closer to the cathode chamber CC than the anode chamber AC.

[0157] A resulting order of membranes and chambers may for example be as follows: AC [S*]nCC or more specific AC [(CEM) D (AEM) E (CEM)]nCC, for example for n = 3 AC (CEM) D (AEM) E (CEM) D (AEM) E (CEM) D (AEM) E (CEM) CC. According to one example embodiment, the product stream is fed into each chamber E of the electrodialysis and water is fed into each chamber D. According to one example embodiment, a voltage is applied between the anode and the cathode.

[0158] When conducting the electrodialysis according to one example embodiment, particularly by applying a voltage to the anode and cathode of the electrodialysis, taurine in each chamber E passes through the electrodialysis in the product stream, wherein alkali metal cations in the product stream are removed through a cation exchange membrane to a neighboring chamber D or the anode chamber, and anions of by-products, such as ditaurate, tritaurate, or isethionate, in the product stream are removed through an anion exchange membrane to a neighboring chamber D or the cathode chamber.

[0159] Accordingly, the taurine remains in the product stream fed into each chamber E, resulting in a cleaned product stream. Furthermore, alkali metal cations and anions of by-products, such as ditaurate, tritaurate, or isethionate, are combined in each chamber D, resulting in a third byproduct stream.

[0160] According to one example embodiment, the third by-product stream and / or the second intermediate product stream may be used to adjust the pH of the product stream to a pH value in the range of 5 to 6 and / or the isoelectric point of taurine according to the before conducting the further electrodialysis of the product stream. Using the third by-product stream for pH adjustment has the advantage that no additional acid needs to be introduced into the reaction. According to one example embodiment, the third by-product stream can be reintroduced into the reaction step (b). This may advantageously influence the chemical equilibrium of the reaction in step (b) and reduce waste product.

[0161] According to one example embodiment of the bipolar membrane electrodialysis or the electrodialysis, an electrode rinsing solution is fed into the anode chamber and an electrode rinsing solution is fed into the cathode chamber. Preferably, the electrode rinsing solution fed into the anode chamber is the same as the electrode rinsing solution fed into the cathode chamber. More preferably, the electrode rinsing solution is circulated between the anode chamber and the cathode chamber. Thereby, changes in the composition of the electrode rinsing solution, such as the aggregation of ions or intermediately formed H2 or O2, that occur when passing the anode or cathode, are reverted when passing the corresponding cathode or anode, respectively.

[0162] According to one example embodiment, the electrode rinsing solution is based on water, in particular de-ionized water. According to one example embodiment, the electrode rinsing solution may further comprise a salt. Particularly, including a salt in the rinsing solution may reduce the total resistance of the bipolar electrodialysis by enhancing electron transfer between the electrodes with the respective rinsing solution. Furthermore, having a salt in the rinsing solution may further improve the ion transfer into the anode and cathode chamber. The salt may for example be selected from alkali metal salts, such as alkali metal sulfate, bisulfite, chloride, or nitride. Preferably, the alkali metal salt comprises the same alkali metal as used in the process according to example aspects of the present invention. For example, alkali metals may be Li, Na, K, Rb, or Cs. Preferably, the alkali metal may be Li, Na, or K. More preferably, the alkali metal may be Na or Ka, particularly Na. Preferably the salt is selected from Na2SC>4, NaHSCU, and NaCl, most preferably Na2SC>4.

[0163] According to one preferred example embodiment, the membrane contacted by the anode chamber is a bipolar membrane and the membrane contacted by the anode chamber is a bipolar membrane. When conducting step (c2), particularly by applying a voltage to the anode and cathode of the bipolar membrane electrodialysis, hydroxide anions are released from the bipolar membrane contacting the anode chamber into the anode chamber, and hydrogen cations are released from the bipolar membrane contacting the cathode chamber into the cathode chamber. The hydroxide anions in the anode chamber may transfer electrons to the anode, thereby reacting to water and O2. The hydrogen cations in the cathode chamber may take up electrons from the cathode, thereby reacting to H2. Circulating the rinsing solution between the anode chamber and the cathode chamber may reverse this reaction.

[0164] According to one preferred example embodiment of the bipolar membrane electrodialysis, the membrane contacted by the anode chamber is a cation exchange membrane and the membrane contacted by the anode chamber is cation exchange membrane, the bipolar membrane electrodialysis comprises the further chamber C between the anode chamber and the set S closes to the anode, and the further chamber A and B between set closest to the cathode and the cathode, wherein the electrode rinsing solution comprises an alkali metal salt. When conducting step (c2), particularly by applying a voltage to the anode and cathode of the bipolar membrane electrodialysis, alkali metal cations from the alkali metal salt in the electrode rinsing solution pass the cation exchange membrane from the anode chamber into the adjacent further chamber C, and alkali metal cations formed in the further chamber B pass the cation exchange membrane into the adjacent cathode chamber. This may lead to a depletion in alkali metal cations in the anode chamber and an increase in alkali metal concentration in the cathode chamber. It has been found that with this setup, the formation of O2 at the anode and H2 at the cathode can be reduced. Circulating the rinsing solution between the anode chamber and the cathode chamber may reverse this reaction and particularly balance the alkali metal concentration in the overall rinsing solution.

[0165] According to one example embodiment, the bipolar membrane electrodialysis or electrodialysis is operated at a voltage in the range of > 20 V to < 800 V, preferably > 50 V to < 700 V, more preferably > 100 V to < 600 V, more preferably > 200 V to < 400 V.

[0166] According to one example embodiment, the bipolar membrane electrodialysis or electrodialysis is operated under a current density in the range of > 1 A / m2to < 1500 A / m2, preferably > 100 A / m2to < 1000 A / m2, more preferably > 150 A / m2to < 500 A / m2, more preferably > 200 A / m2to < 350 A / m2.

[0167] According to one example embodiment, the anode and the cathode are a metal electrode, preferably a stainless steel or Ti / Pt electrode. Generally electrodes suitable to decompose water cam be used as cathode and anode.

[0168] (d) Reaction of b -product and sulfur dioxide

[0169] According to example aspects of the invention, the method comprises the step of

[0170] (d) optionally reacting the at least one by-product from the at least one by-product stream with sulfur dioxide to obtain a recycle educt stream comprising alkali metal bisulfite.

[0171] It has surprisingly been found that the obtained by-products may be re-cycled in the process. Particularly, it has been found that the by-products may also be re-cycled continuously. It is to be understood that selecting a particular alkali metal taurate, for example sodium taurate, yields a by-product suitable for reacting sulfur dioxide to the corresponding alkali metal bisulfite, such as sodium bisulfite.

[0172] In one example embodiment the at least one by-product is a first by-product obtained from a first reaction step of step (c) provided in a first by-product stream, and a second by-product obtained in a second reaction step of step (c) provided in a second by-product stream.

[0173] In one alternative example embodiment, the at least one by-product is one by-product obtained in a single reaction step of (c) as one by-product stream.

[0174] The recycle educt stream comprising alkali metal bisulfite may comprise alkali metal bisulfite in an amount of > 5 wt.-% to < 55 wt.-% based on the volume of the water, preferably > 15 wt.-% to < 45 wt.-%, more preferably > 25 wt.-% to < 35 wt.-%, for example 30 wt.-%.

[0175] In one example embodiment, the alkali metal bisulfite obtained in the recycle educt stream is provided as second educt stream in method step (a). In one example embodiment the alkali metal bisulfite obtained in the recycle educt stream is provided together with further alkali metal bisulfite as second educt stream in method step (a). Particularly, the second educt stream in method step (a) may comprise alkali metal bisulfite obtained from the recycle educt steam in an amount of > 10 wt.-% to < 50 wt.-% based on the total wight of alkali metal bisulfite in the second educt stream, preferably > 20 wt.-% to < 45 wt.-%, more preferably > 30 wt.-% to < 40 wt.-%.

[0176] (dl) Two-step reaction o f by-product with sulfur dioxide

[0177] According to one alternative example embodiment, method step (d) may be performed according to method step (dl), comprising the steps of

[0178] (dla) reacting the second by-product from the second by-product stream with sulfur dioxide to ammonium bisulfite in an intermediate recycle educt stream.

[0179] (d2a) reaction the ammonium bisulfite in the intermediate recycle educt stream with the first by-product from the first by-product stream in an ion exchange column to alkali metal bisulfite in the recycle educt stream.

[0180] Particularly, the second by-product may be the ammonia obtained in step (clb) when removing ammonia from the ammonium taurate, and the first by-product may be the alkali metal cations bound to the acidic cation exchange resin of the ion exchange column obtained as first byproduct stream in step (cl a).

[0181] (dla) reaction with sulfur dioxide

[0182] Sulfur dioxide may be reacted in step (dla) with the second by-product from the second byproduct stream to ammonium bisulfite in an intermediate recycle educt stream.

[0183] Particularly, the second by-product from the second by-product stream may be the ammonia obtained in step (clb) when removing ammonia from the ammonium taurate. In one example embodiment, the sulfur dioxide is provided together with water in a first precursor stream. In one example embodiment, the sulfur dioxide and the ammonia are reacted continuously in a continuous flow reactor, such as for example a plug flow reactor, to continuously obtain the intermediate recycle educt stream comprising the ammonium bisulfite. Preferably, the sulfur dioxide is provided continuously as the first precursor stream and the ammonia is provided continuously as the second by-product stream In one example embodiment the first precursor stream and second by-product stream are mixed together in the continuous flow reactor.

[0184] In one example embodiment, the ammonia may be provided as second by-product stream as ammonia gas. In an alternative example embodiment, ammonia may be provided as second byproduct stream as aqueous ammonia solution.

[0185] In one example embodiment, the sulfur dioxide may be provided in aqueous solution.

[0186] In one example embodiment, the sulfur dioxide is provided for reaction with the ammonia in a molar ratio of sulfur dioxide to ammonia in the range of > 1 : 1 to < 1 : 100, preferably > 1 :2 to < 1 :90, preferably > 1 :3 to < 1 :80, preferably > 1 :4 to < 1 :70, preferably > 1 :5 to < 1 :60, preferably > l:6to< 1:50, preferably > l:7to< 1:45, preferably > l:8to< 1:40, preferably > l:9to< 1:35, preferably > 1 : 10 to < 1 :30, preferably > 1 : 11 to < 1 :25, preferably > 1 : 12 to < 1 :20, preferably > 1:13 to < 1:18, preferably > 1:14 to < 1:17, preferably > 1:15 to < 1:16. In one example embodiment, the ammonia is provided for reaction with the sulfur dioxide in excess when considering a stochiometric reaction of 1 mol sulfur dioxide with 1 mol ammonia.

[0187] In one example embodiment, additional ammonia is provided as second precursor stream for reaction in step (dla). In one example embodiment, excess ammonia can be removed from the intermediate recycle educt stream comprising the ammonium bisulfite and continuously be recycled as ammonia in a second precursor stream. It is to be understood that the second precursor stream may partially comprise the recycled ammonia from intermediate recycle educt stream and additional ammonia so the total amount of ammonia provided in step (dla) is sufficient for the reaction. In one example embodiment the ammonia is removed from the intermediate recycle educt stream by flashing the second intermediate product stream and separating the resulting gaseous ammonia from the remaining liquid comprising the ammonium bisulfite.

[0188] (dlb) ion exchange

[0189] The ammonium bisulfite from the intermediate recycle educt stream may be reacted with the alkali metal cations in the ion exchange column from the first by-product stream to alkali metal bisulfite in the recycle educt stream.

[0190] Particularly, the first by-product may be the alkali metal cations bound to the acidic cation exchange resin of the ion exchange column obtained as first by-product stream in step (cla). In one example embodiment, the ion exchange column is an exhausted column from step (cla). In one example embodiment, when step (cla) is performed continuously alternating between at least two ion exchange columns, wherein the step is performed continuously with one ion exchange column until the first column is exhausted and the step is then performed continuously with at least a second ion exchange column until the second column is exhausted, step (dlb) is also performed continuously alternating between the exhausted columns, regenerating the ammonium anions bound to the ion exchange resin. In one example embodiment, at least two sets of multiple ion exchange columns are used altematingly.

[0191] In one example embodiment, the ion exchange column is considered regenerated once the yield of alkali metal sulfite based on the ammonium bisulfite at the exit of the column is < 90%, preferably < 80%, preferably < 70%, more preferably < 60%.

[0192] In one example embodiment, the intermediate recycle educt stream and the first by-product stream flow through the ion exchange column in step (dlb) in the same direction as the second intermediate product stream in step (cla). In an alternative example embodiment, the intermediate recycle educt stream and the first by-product stream flow through the ion exchange column in step (dlb) in the opposite direction as the second intermediate product stream in step (cl a).

[0193] (d2) One-step reaction of by-product with sulfur dioxide

[0194] According to one alternative example embodiment, method step (d) may be performed according to method step (d2), comprising the step of

[0195] (d2) reacting the by-product from the by-product stream with sulfur dioxide to alkali metal bisulfite in the recycle educt stream.

[0196] Particularly, the at least one by-product is one by-product obtained in a single reaction step of (c2) as one by-product stream.

[0197] According to one example embodiment, sulfur dioxide may be reacted in step (d2) with the alkali metal hydroxide obtained as the by-product in the by-product stream in (c2) to alkali metal bisulfite in an intermediate recycle educt stream.

[0198] In one example embodiment, the sulfur dioxide and the alkali metal hydroxide are reacted continuously in a continuous flow reactor, such as such as for example a plug flow reactor, to continuously obtain the recycle educt stream comprising the alkali metal bisulfite. Preferably, the sulfur dioxide is provided continuously as the first precursor stream and the alkali metal hydroxide is provided continuously as the by-product stream In one example embodiment the first precursor stream and by-product stream are mixed together in the continuous flow reactor. In one example embodiment, the alkali metal hydroxide may be provided as aqueous solution. In one example embodiment, the sulfur dioxide may be provided in aqueous solution or as gas. In one example embodiment, additional alkali metal hydroxide is provided as second precursor stream for reaction in step (d2).

[0199] In one example embodiment, the sulfur dioxide is provided for reaction with the alkali metal hydroxide in a molar ratio of sulfur dioxide to alkali metal hydroxide in the range of > 1:1 to < 1:100, preferably > 1:2 to < 1:0.5, preferably > 1:1.5 to < 1:0.75, preferably > 1:1.1 to < 1:0.9.

[0200] (e) Crystallization of taurine

[0201] According to example aspects of the invention, the method comprises the step of (e) optionally crystallizing the taurine from the product stream and separating the crystallized taurine from a resulting mother liquor.

[0202] In step (c) the product stream comprising taurine is obtained. Taurine may be crystallized by reducing the temperature of the product stream.

[0203] In one example embodiment, taurine is crystallized at a temperature in the range of > 0 °C to < 25 °C, preferably > 5 °C to < 20 °C, preferably > 10 °C to < 15 °C.

[0204] In one example embodiment, taurine is concentrated in the product stream by partially removing solvent, before cooling the product stream and crystallizing the taurine. By increasing the taurine concentration in the product stream, the crystallization may be faster of may be performed with better yield.

[0205] The solvent may partially be removed via the gas at elevated temperature and / or at reduced pressure. In one example embodiment, concentration of the taurine in the product stream is achieved by heating the product stream to a temperature in the range of > 70 °C to < 100 °C, preferably > 80 °C to < 95 °C, preferably > 85 °C to < 90 °C, and a pressure in the range of > 0.1 bar to < 1 bar, preferably > 0.5 bar to < 0.9 bar, > 0.7 bar to < 0.8 bar.

[0206] The temperature may be achieved via a heat exchanger, wherein the heat exchange fluid has been heated by the reaction in method step (a).

[0207] The crystallized taurine may be separated from the resulting mother liquor, preferably via solid liquid separation, such as filtration.

[0208] According to one example embodiment, the taurine may further be processed as is commonly known in the art. For example, the taurine may be recrystallized from water to increase purity of the product.

[0209] (f) Further steps

[0210] According to one example embodiment, the method may further comprise various recycling steps, wherein by-products and / or waste-products may be used in further reaction steps. Preferably, by-products may be isolated from waste-products, and by-products may be reintroduced into the method and reacted further. According to one example embodiment, the mother liquor obtained in step (e) after removing the taurine is introduced in step (a) or (b) as recycle by-product stream. Preferably, the mother liquor comprises by-products selected from ditaurine and tritaurine. In one example embodiment, the mother liquor further comprises waste-products, for example ethylene glycol. In one example embodiment, waste-products are removed from the mother liquor before reintroducing the mother liquor as recycle by-product stream into the method.

[0211] In one example embodiment, the mother liquor comprises at least one of isethionic acid and ditaurine, and further comprises optionally tritaurine, and is introduced in step (a) as recycle by-product stream. In one example embodiment the mother liquor is free from ethylene glycol and is introduced in step (a) as recycle by-product stream. Introducing the mother liquor as recycle by-product stream in step (a) allows for the reaction of isethionic acid with alkali metal bisulfite to alkali metal isethionate and ditaurine to alkali metal ditaurate. Tritaurine may react to alkali metal tritaurate. These may further react in step (b) with ammonia to alkali metal taurate. Particularly, introducing the by-products in step (a) and (b) allows for a shift of the reaction equilibrium towards the desired intermediate products.

[0212] Apparatus

[0213] In example aspects, an apparatus for conducting the method according to example aspects of the present invention, comprising at least one of the following (a) - (c):

[0214] (a) a continuous reactor comprising an input for the ethylene oxide and an input for the alkali metal bisulfite, and an output for the first intermediate product stream comprising the alkali metal isethionate;

[0215] (b) a continuous reactor comprising an input for the alkali metal isethionate from the first intermediate product stream and an input for ammonia, and an output for the second intermediate product stream comprising an alkali metal taurate; and

[0216] (c) a continuous reactor comprising an input for the alkali metal taurate from the second intermediate product stream, and an output for at least one by-product stream comprising the at least one by-product and an output for the product stream comprising the taurine;

[0217] and (d) optionally a continuous reactor comprising an input for the at least one by-product from the at least one by-product stream and an input for sulfur dioxide, and an output for the recycle educt stream comprising alkali metal bisulfite; and

[0218] (e) optionally a continuous reactor for crystallizing the taurine comprising an input for the product stream, a separator, an output for the crystallized taurine and an output for the resulting mother liquor.

[0219] According to one example embodiment, a method for the continuous manufacture of taurine, comprising at least one of the steps of (a) - (c):

[0220] (a) reacting an ethylene oxide and an alkali metal bisulfite to obtain a first intermediate product stream (10) comprising an alkali metal isethionate;

[0221] (b) reacting the alkali metal isethionate from the first intermediate product stream (10) with ammonia to obtain a second intermediate product stream (20) comprising an alkali metal taurate; and

[0222] (c) converting the alkali metal taurate from the second intermediate product stream (20) to obtain taurine and at least one by-product, wherein the by-product is suitable for reacting sulfur dioxide to alkali metal bisulfite, and separating the at least one by-product from the taurine to obtain at least one by-product stream (30) comprising the at least one by-product and a product stream (40) comprising the taurine;

[0223] and

[0224] (d) optionally reacting the at least one by-product from the at least one by-product stream (30) with sulfur dioxide to obtain a recycle educt stream (50) comprising alkali metal bisulfite; and

[0225] (e) optionally crystallizing the taurine from the product stream (40) and separating the crystallized taurine from a resulting mother liquor (60);

[0226] wherein the method comprises at least step (c), and

[0227] wherein method step (c) is preformed according to method step (cl), comprising the steps of (cl a) converting the alkali metal taurate from the second intermediate product stream (20) with ammonium anions in an ion exchange column to ammonium taurate comprised in a third intermediate product stream and alkali metal cations comprised in a first by-product stream (30),

[0228] (clb) removing ammonia in a second by-product stream (30) from the third intermediate product stream to form the product stream (40) comprising taurine.

[0229] According to one example embodiment, the ethylene oxide and the alkali metal bisulfite are reacted at a temperature in the range of > 5 °C to < 200 °C, preferably > 10 °C to < 190 °C, preferably > 15 °C to < 180 °C, preferably > 20 °C to < 170 °C, preferably > 30 °C to < 160 °C, preferably > 40 °C to < 150 °C, preferably > 50 °C to < 140 °C, preferably > 30 °C to < 130 °C, for example 80 °C.

[0230] According to one example embodiment, the ethylene oxide and the alkali metal bisulfite are reacted at a pressure in the range of > 0 bar to < 100 bar, preferably > 1 bar to < 90 bar, preferably > 1.5 bar to < 80 bar, preferably > 2 bar to < 70 bar, preferably > 2.5 bar to < 60 bar, preferably > 3 bar to < 50 bar, preferably > 3.5 bar to < 40 bar, preferably > 4 bar to < 25 bar, preferably > 4.5 bar to < 15 bar, preferably > 4.8 bar to < 10 bar, preferably > 5 bar to < 8 bar, for example 5.5 bar.

[0231] According to one example embodiment, the alkali metal isethionate is provided for reaction with the ammonia in a molar ratio of alkali metal isethionate to ammonia in the range of < 1 :0.1 to > 1:100, preferably < 1:0.5 to > 1:90, preferably < 1:1 to > 1:80, preferably < 1:1.5 to > 1:70, preferably < 1 :2 to > 1 :60, preferably < 1 :2.5 to > 1:50, preferably < 1 :3 to > 1 :45, preferably < 1:3.5 to > 1:40, preferably < 1:4 to > 1:35, preferably < 1:4.5 to > 1:30, preferably < 1:5 to > 1:25, preferably < 1:5.5 to > 1:20, preferably < 1:6 to > 1:18, preferably < 1:6.5 to > 1:17, preferably < 1 :7 to > 1:16.

[0232] According to one example embodiment, the alkali metal isethionate and the ammonia are reacted until a yield of the alkali metal taurate in the range of > 10% to < 100% based on the theoretical yield of alkali metal taurate based on the amount of alkali metal isethionate provided is reached, preferably > 35% to < 95%, preferably > 50% to < 92%, preferably > 65% to < 90%, preferably > 67% to < 87%, preferably > 70% to < 85%.

[0233] According to one example embodiment, step (cla) is performed continuously alternating between at least two ion exchange columns, wherein during the time the step is performed with one of the ion exchange columns, the other ion exchange columns are regenerated.

[0234] According to one example embodiment, the second intermediate product stream led into the ion exchange column in step (cla) comprises alkali metal taurate in an amount of > 1 wt.-% to < 65 wt.-% based on the volume of the water, preferably > 5 wt.-% to < 30 wt.-%, more preferably > 10 wt.-% to < 25 wt.-%.

[0235] According to one example embodiment, the alkali metal taurate is sodium taurate and the second intermediate product stream led into the ion exchange column in step (cla) comprises sodium taurate in an amount of > 2 wt.-% to < 25 wt.-% based on weight of the second intermediate product stream, preferably > 5 wt.-% to < 20 wt.-%, more preferably > 10 wt.-% to < 15 wt.-%.

[0236] According to one example embodiment, wherein the third intermediate product stream is heated to a temperature in the range of > 20 °C to < 150 °C, preferably > 80 °C to < 140 °C, preferably > 85 °C to < 130 °C, > 90 °C to < 120 °C, > 95 °C to < 110 °C, for example 100 °C

[0237] According to one example embodiment, method step (d) may be performed according to method step (dl), comprising the steps of

[0238] (dla) reacting the second by-product from the second by-product stream (30) with sulfur dioxide to ammonium bisulfite in an intermediate recycle educt stream.

[0239] (d2a) reaction the ammonium bisulfite in the intermediate recycle educt stream with the first by-product from the first by-product stream (30) in an ion exchange column to alkali metal bisulfite in the recycle educt stream (50). According to one example embodiment, the recycle educt stream (50) comprising alkali metal bisulfite may comprise alkali metal bisulfite in an amount of > 5 wt.-% to < 55 wt.-% based on the volume of the water, preferably > 15 wt.-% to < 45 wt.-%, more preferably > 25 wt.-% to < 35 wt.-%,

[0240] According to one example embodiment, in step (e) taurine is concentrated in the product stream (40) by heating the product stream (40) to a temperature in the range of > 70 °C to < 100 °C, preferably > 80 °C to < 95 °C, preferably > 85 °C to < 90 °C, and a pressure in the range of > 0.1 bar to < 1 bar, preferably > 0.5 bar to < 0.9 bar, > 0.7 bar to < 0.8 bar.

[0241] According to one example embodiment, the product stream (40) is heated via a heat exchanger, wherein the heat exchange fluid has been heated by the reaction in method step (a).

[0242] According to one example embodiment, the mother liquor (60) obtained in step (e) after removing the taurine is introduced in step (a) or (b) as recycle by-product stream (60).

[0243] According to one example example embodiment, an apparatus for conducting apparatus for conducting the method according to example aspects of the present invention comprising at least one of the following (a) - (c):

[0244] (a) continuous reactor comprising an input for the ethylene oxide and an input for the alkali metal bisulfite, and an output for the first intermediate product stream (10) comprising the alkali metal isethionate;

[0245] (b) a continuous reactor comprising an input for the alkali metal isethionate from the first intermediate product stream (10) and an input for ammonia, and an output for the second intermediate product stream (20) comprising an alkali metal taurate; and

[0246] (c) a continuous reactor comprising an input for the alkali metal taurate from the second intermediate product stream (20), and an output for at least one by-product stream (30) comprising the at least one by-product and an output for the product stream (40) comprising the taurine; and

[0247] (d) optionally a continuous reactor comprising an input for the at least one by-product from the at least one by-product stream (30) and an input for sulfur dioxide, and an output for the recycle educt stream (50) comprising alkali metal bisulfite; and

[0248] (e) optionally a continuous reactor for crystallizing the taurine comprising an input for the product stream (40), a separator, an output for the crystallized taurine and an output for the resulting mother liquor (60);

[0249] wherein the apparatus comprises at least the continuous reactor (c), and

[0250] wherein the continuous reactor (c) is an ion exchange column for converting the alkali metal taurate from the second intermediate product stream (20) with ammonium anions to ammonium taurate comprised in the second intermediate product stream and alkali metal cations comprised in the first by-product stream (30), and a continuous reactor for removing ammonia in the second by-product stream (30) from the second intermediate product stream to form the product stream (40) comprising taurine.

[0251] Examples

[0252] Example la: Reaction of ethylene oxide and alkali metal bisulfite

[0253] 1 equivalent ethylene oxide was reacted with 1.1 equivalents of sodium bisulfite (NaHSO3) in aqueous solution under presence 0.065 equivalent of NaOH in a flow reactor at a temperature of 80°C and of 6 bar with a retention time in the flow reactor of 5 minutes. Sodium isethionate was obtained with a yield > 96% and < 3% of ethylene glycol waste-product

[0254] Example lb: Reaction of ethylene oxide and alkali metal bisulfite

[0255] 1 equivalent ethylene oxide was reacted with 0.91 equivalents of sodium bisulfite (NaHSO3) in aqueous solution under presence 0.065 equivalent of NaOH in a flow reactor at a temperature of 80°C and of 6 bar with a retention time in the flow reactor of 2.5 minutes. Sodium isethionate was obtained with a yield > 96% and < 3% of ethylene glycol waste-product

[0256] Example 2a: Reaction of alkali metal isethionate with ammonia The sodium isethionate solution from Example 1 a was reacted in a continuous flow reactor with 15 equivalents of NH3 per 1 equivalent sodium isethionate present in the solution. The reaction was performed at a temperature of 310 °C and a pressure of 130 bar with a retention time in the flow reactor of 15 minutes. Sodium taurinate was obtained with a yield of >70% based on the sodium isethionate, with < 21% sodium isethionate and < 5% sodium ditaurinate.

[0257] Example 2b: Reaction of alkali metal isethionate with ammonia

[0258] The sodium isethionate solution from Example lb was reacted in a continuous flow reactor with 15 equivalents of NH3 per 1 equivalent sodium isethionate present in the solution. The reaction was performed at a temperature of 260 °C and a pressure of 120 bar with a retention time in the flow reactor of 40 minutes. Sodium taurinate was obtained with a yield of >70% based on the sodium isethionate, with < 20% sodium isethionate and < 10% sodium ditaurinate.

[0259] Example 3: Conversion of alkali metal taurate to taurine and by-product via ion exchange A glass column with 2.5 cm diameter and a porous frit at the bottom was filled with 125 mL of a weakly acidic cation exchange resin. To adjust the flowrate though the column, the setup was equipped with a peristaltic pump. A pH measurement at the exit of the column allowed the monitoring of the treated solutions.

[0260] The resin was activated into its ammonium form by pumping 180 g of a 9.2 w% NH4Cl-solution through the system at a flowrate of 12 mL / min. This corresponds to 5.76 times the resin volume per hour.

[0261] After that, the column was rinsed with 200 g of deionized water at a higher flowrate to avoid cross-contamination of the used solutions.

[0262] 149 g of the reaction product from Example 2, containing 13.1 wt.% of sodium taurate, 1.5 w% of unreacted sodium isethionate and 3.5 wt.% of disodium ditaurinate were passed through the column at 12 mL / min. The analysis of the collected liquid after the column for sodium ions resulted in a concentration of 0.42 wt.%. Compared to the 3.3 wt.% that have been measured before, this corresponds to an ion exchange efficiency of 87%.

[0263] Example 4: Conversion of alkali metal taurate to taurine and by-product via bipolar membrane electrodialysis 387 g of the a product solution obtained analogous to Example 2, containing about 10.5 w% sodium taurate, 4.5 w% unreacted sodium isethionate and 2.66 w% of disodium ditaurinate were put in a feed buffer (for chambers B). Acidic (for chambers A) and base (for chambers C) buffers were filled with 700 g and 250 g of deionized water, respectively. Small centrifugal pumps were used to provide the liquid flow through the compartments / chambers of the bipolar membrane electrodialysis. A setup for the bipolar membrane electrodialysis according to the following was used:

[0264] AC (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) CC.

[0265] The maximum voltage between the electrodes was set to 35 V, the maximum current to 2.0 A. After switching on the current, which was kept constant at 2.0 A after a steady state was reached, the experiment ran until there was not enough material left in the salt compartment to sustain the volume flow. In average this resulted in a current density of 302 A / m2. At this point 2.06 w% taurate, 0.53 w% sodium ions and 1.23 w% isethionate were detected in 129 g of the remaining starting solution. The acidic compartment contained 2.8 w% of taurine measured by HPLC and the base compartment contained 5.1 w% of bases with 1.1. w% of taurate impurities. Together with the masses in the corresponding compartments this corresponded to a yield of 65%. The taurine left in the base or salt solution however could be recycled into the process to further increase the yield.

[0266] Example 5: Conversion of alkali metal taurate to taurine and by-product via bipolar membrane electrodialysis and pH-adiustment

[0267] 1297 g of the a product solution obtained analogous to Example 2, containing about 7.1 w% sodium taurate, about 1 w% unreacted sodium isethionate and about 1 w% of disodium ditaurinate were put in a feed buffer (for chambers B). Acidic (for chambers A) and base (for chambers C) buffers were filled with 1196 g and 962 g of deionized water, respectively. Small centrifugal pumps were used to provide the liquid flow through the compartments / chambers of the bipolar membrane electrodialysis. A setup for the bipolar membrane electrodialysis according to the following was used:

[0268] AC (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) CC. The maximum voltage between the electrodes was set to 18 V, the maximum current to 2.0 A. After switching on the current, the voltage was kept at a constant 18 V. During the experiment the conductivity in the feed chamber constantly decreased, whereas the conductivities in the acid and base chamber increased based on ion concentrations. The current also rose until it reached a maximum of 1.6 A. With the depletion of ions in the feed chamber the resistance increased causing the current to decrease again eventually. Once no further decrease could be seen the experiment was stopped.

[0269] At this point only traces of taurine could be detected in the remaining 667 g of the starting solution. The acidic compartment contained 5.4 w% of taurine and 0.8 w% of isethionic acid measured by HPLC. Ditaurine could be detected at the same order of magnitude as the isethionate. The base compartment contained 3.2 w% of bases with 0.7. w% of taurinate, 0.2 w% of isethionate and traces of ditaurinate impurities. Together with the masses in the corresponding compartments this corresponded to a yield of 95%. The taurine left in the base solution however could be recycled into the process to further increase the yield.

[0270] Example 6: Conversion of alkali metal taurate to taurine and by-product via bipolar membrane electrodialysis and following electrodialysis

[0271] 669 g of the a product solution obtained analogous to Example 2, containing about 8 w% sodium taurate, about 1.1 w% unreacted sodium isethionate and about 1.1 w% of disodium ditaurinate were put in a feed buffer (for chambers B). Acidic (for chambers A) and base (for chambers C) buffers were filled with 613 g and 500 g of deionized water, respectively. Small centrifugal pumps were used to provide the liquid flow through the compartments / chambers of the bipolar membrane electrodialysis. A setup for the bipolar membrane electrodialysis according to the following was used:

[0272] AC (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) C (BP) A (AEM) B (CEM) CC.

[0273] The maximum voltage between the electrodes was set to 18 V, the maximum current to 2.0 A. After switching on the current, the voltage was kept at a constant 18 V. During the experiment the conductivity in the feed chamber constantly decreased, whereas the conductivities in the acid and base chamber increased based on ion concentrations. The current also rose until it reached a maximum of 1.7 A. With the depletion of ions in the feed chamber the resistance increased causing the current to decrease again eventually. Once no further decrease could be seen the experiment was stopped.

[0274] At this point only traces of taurine could be detected in the remaining 295 g of the starting solution. The acidic compartment contained 6 w% of taurine and 1.1 w% of isethionic acid measured by HPLC. Ditaurine could be detected at the same order of magnitude as the isethionic acid. The base compartment contained 3.2 w% of bases with 0.7. w% of taurinate, 0.2 w% of isethionate and traces of ditaurinate impurities. Together with the masses in the corresponding compartments this corresponded to a yield of 90%. The taurine left in the base solution however could be recycled into the process to further increase the yield.

[0275] The pH of the acidic solution obtained in the acid compartment of the bipolar membrane setup was adjusted from 1 to 5.5 with material from the ammonolysis reaction obtained analogous to Example 2. After that 937 g of pH adjusted material were inserted into the diluate buffer feeding chambers E of the electrodialysis, using a setup according to the following:

[0276] AC (CEM) D (AEM) E (CEM) D (AEM) E (CEM) D (AEM) E (CEM) D (AEM) E (CEM) D (AEM) E (CEM) CC.

[0277] The staring material contained about 5.5 w% of taurine, about 1.1 w% of sodium isethionate and about 1.1 w% of disodium ditaurinate. The concentrate buffer feeding chambers D was filled with 358 g of deionized water. After switching on the current and keeping a constant voltage of 18 V the conductivity in the chambers E decrease and the conductivity in the concentrate chambers D increased. The experiment was stopped when the current declined and a conductivity of 1.9 mS / cm was measured. At that point the concentrate obtained from chamber D comprised of 0.9 w% of taurine, 1.8 w% of sodium isethionate and a similar amount of sodium ditaurine. This stream could be recycled as third by-product stream to the ammonolysis reaction to increase the overall yield. Compared to the recycle of the crystallization mother liquor less taurine will be inserted in the reaction step and hence reducing the necessary recycle streams.

[0278] The diluate solution obtained from chambers D containing about 5.9 w% of taurine and about 0.1 w% of isethionate and about 0.1 w% of disodium ditaurinate can be concentrated as described with respect to the product stream. Example 7: Crystallization of taurine

[0279] In total, 274 g of the material obtained in Example 3 were transferred to a flask and heated to 100 °C at atmospheric pressure. After the distillation of 154 g of water and ammonia the solution was cooled, and the formed crystals of taurine were isolated by filtration resulting in 12.3 g of taurine. The same has been done with material obtained from Example 4, 5, and 6, showing similar results.

[0280] Example 8: Reaction of alkali metal isethionate with ammonia

[0281] The ammonolysis of sodium isethionate with ammonia delivers a solution comprising unreacted sodium isethionate, sodium taurate, disodium ditaurate, and trisodium tritaurate. To isolate pure taurine, the corresponding sodium salt must be converted to its free acid. This can be achieved using bipolar membrane electrodialysis in a two-chamber or three-chamber configuration. The module for the two-chamber configuration is equipped with two electrodes and a stack of alternating membranes and spacers, starting with the spacers on the electrodes, which are rinsed by an electrolyte solution to facilitate the reactions on the electrodes. To separate the electrode chamber from the other chambers, cation exchange membranes are used. Between the electrodes, several cell pairs are arranged. Each comprises a bipolar membrane, a spacer for the acidic circuit, a cation exchange membrane, and a spacer for the base circuit. The last one concludes with the bipolar membrane of the adjacent cell pair. This results in two separate circuits, between which mass transfer is only possible through the membranes. Under the influence of an electric field, the alkali ions in the solution begin migrating through the cation exchange membrane towards the cathode, thereby moving from the acidic chamber to the base chamber. The electric field also causes the electrolysis of water inside the bipolar membranes. This leads to the formation of OH- ions on the side facing the anode and H+ ions on the side facing the cathode. The transported alkali ions will recombine with the hydroxide ions to form alkali hydroxide, which can be reused in the production of alkali isethionate. Meanwhile, the H+ ions will start protonating the taurates. In this way, the pH of the acidic stream can be adjusted to the isoelectric point of taurine, thus converting alkali taurate into taurine.

[0282] The same is possible with a three-chamber setup. In this case, a third chamber is added between the acid and the base chamber, separated by a cation exchange membrane towards the base chamber and an anion exchange membrane towards the acidic chamber. Applying an electric field will lead to the migration of taurate ions into the acid compartment and alkali ions into the base compartment. There, they recombine with the corresponding ion from the water electrolysis taking place inside the bipolar membrane. In this case, the ions of the side components, mainly isethionate and ditaurate, will also migrate into the acidic compartment to be protonated. This results in a sharp decrease in pH. To increase the pH to the isoelectric point of taurine, a part of the product stream from the ammonolysis reaction can be added to the stream exiting the acidic chamber.

[0283] After converting alkali taurate to taurine by adjusting the pH, the product solution still contains unwanted byproducts, such as alkali isethionate and alkali ditaurate. They can be removed from the solution using a conventional electrodialysis setup, exploiting the fact that taurine is present as a zwitterion at its isoelectric point, thus bearing no net charge. The other components, however, remain present as charged ions, causing them to migrate in an electric field. Using a conventional electrodialysis stack that comprises alternating diluate and concentrate chambers separated by cation and anion exchange membranes, the taurine solution can be easily purified. The application of an electrical field will not affect the uncharged taurine, whereas the charged ions are caused to migrate into the concentrate chamber. The formed concentrate mainly comprises alkali isethionate and alkali ditaurate, and only small amounts of taurine can be recycled into the ammonolysis reaction to improve the overall yield of taurine. This is a significant advantage compared to recycling the mother liquor after taurine crystallization. In this case, the taurine content is given by the residual solubility in the mother liquor, which is about 7 w% at 25 °C. Using electrodialysis, the amount of taurine that is recycled unnecessarily can be reduced. Additionally, the risk of impurities in the precipitated taurine can be significantly reduced when crystallization occurs from a purified solution.

[0284] Example 8a: Conversion of alkali metal taurate to taurine and by-product via bipolar membrane electrodialysis

[0285] After removing ammonia from the product stream of the ammonolysis reaction, a two-chamber electrodialysis stack was used to convert sodium taurate to taurine. To initiate the experiment, the buffer for the base circuit was prepared by filling it with 252 g of deionized water. The electrolyte solution rinsing the electrode chambers comprised a sodium sulfate solution with a concentration of 20 g / L. The buffer for the acidic circuit was filled with 504 g of material from the previous reaction step, which was stripped of ammonia and comprised of 9.2 w% taurate, 1.2 w% sodium isethionate, 2.7 w% sodium ditaurate, and 0.3 w% ethylene glycol. After starting the pumps and rinsing the circuits for several minutes, the power supply was set to a maximum current of 1.9 A, corresponding to a current density of 300 A / m2 and a voltage of 20 V. The developing electrical field caused sodium ions to migrate from the acidic compartment through the cation exchange membrane towards the cathode, forming NaOH. The corresponding H+ ion is transported into the acidic compartment to form taurine. This causes the pH and conductivity in the acidic compartment to constantly decrease, as free taurine is mainly present as a zwitterion. When a pH of 6 is reached, the experiment is stopped. Under these conditions, it can be expected that the majority of the sodium taurate is converted to taurine in its zwitterionic form. The sodium isethionate and the sodium ditaurate, however, are expected to remain present as charged ions due to their lower pKa values of the sulfonic acid groups. At the end of the experiment, the acidic buffer contained 354 g of a solution comprising 10.2 w% taurine, 1.2 w% sodium isethionate, 2.7 w% sodium ditaurate, and 0.3 w% ethylene glycol. The base buffer was filled with 389 g of a solution comprising 1.7 w% taurate, 0.4 w% sodium isethionate, 0.9 w% disodium ditaurate, 3.9 w% NaOH, and 0.1 w% ethylene glycol.

[0286] Example 8b: Conversion of alkali metal taurate to taurine and by-product via bipolar membrane electrodialysis

[0287] The experiment was conducted according to Example 8a, but instead of using deionized water to fill the base compartment, 125 g of the resulting base solution from Example 8a were diluted with 125 g of water and used as the starting solution. At the end of the experiment, 332 g of acidified solution comprising 11.1 w% Taurine, 1.1 w% sodium isethionate, 2.6 w% of disodium ditaurate, and 0.3 w% ethylene glycol were found. The base compartment included 394 g of a solution comprising 2.8 w% taurate, 0.6 w% sodium isethionate, 1.5 w% disodium ditaurate, and 5.2 w% NaOH.

[0288] Example 8c: Purification of Taurine via Electrodialysis

[0289] The acidified solutions from Example 8a and Example 8b, with a pH of 6, were combined to be further purified using conventional electrodialysis. To do so, a membrane stack with 5 cell pairs of alternating anion and cation exchange membranes with spacers in between was used. In this way, one diluate and one concentrate circuit are formed. To start the experiment, the buffer of the diluate circuit was filled with 680 g of taurine solution. The concentrate circuit was filled with 299 g of deionized water. After starting the pumps and rinsing the circuits for several minutes, the power supply was set to a maximum current of 1.2 A, corresponding to a current density of 187.5 A / m2and a voltage of 8 V. The developing electrical field causes the present charged ions to migrate towards the corresponding electrode. That way, the present sodium isethionate and disodium ditaurate will be transported from the diluate chamber to the concentrate chamber. Taurine, however, is present as a zwitterion at these conditions and for that reason it is not influenced by the electrical field and will stay in the diluate stream. Consequently, the conductivity of the diluate decreased constantly during the experiment until a conductivity of 1 mS / cm was reached. Then the experiment was stopped. The concentrate circuit comprised 395 g of a solution comprising 0.8 w% taurine, 1.7 w% sodium isethionate, and 3.8 w% sodium ditaurate. In the diluate, a solution of 559 g comprised of 11.0 w% taurine and 0.1 % of sodium ditaurate, and 0.3 w% ethylene glycol resulted. These experiments demonstrate that all charged byproducts can be removed efficiently.

[0290] To obtain pure taurine, the purified solution can be concentrated and crystallized.

[0291] Example 8d: Conversion of alkali metal taurate to taurine and by-product via bipolar membrane electrodialysis

[0292] The experiment was conducted according to Example 8a, but a solution of 614 g comprising 9.0 w% taurate, 1.0 w% sodium isethionate, 3.7 w% sodium ditaurate, and 0.2 w% ethylene glycol was filled in the acidic buffer. The base buffer was filled with 239 g of deionized water. After stopping the experiment, 412 g of an acidified solution with a pH of 6 comprising 9.2 w% taurate, 0.8 w% sodium isethionate, 3.1 w% sodium ditaurate, and 0.2 w% ethylene glycol were obtained. The base compartment contained 414 g of a solution comprising 2.0 w% taurate, 0.4 w% sodium isethionate, 1.4 w% disodium ditaurate, and 4.0 w% NaOH.

[0293] Example 8e: Purification of Taurine via Electrodialysis

[0294] The experiment was conducted according to Example 8c, but 411 g of the acidified solution from Example 8d were used to start the experiment. The concentrate buffer was filled with 210 g of deionized water. Additionally, the terminating condition in this experiment was a conductivity of 0.4 mS / cm instead of 1 mS / cm in the diluate stream.

[0295] The resulting 350 g of diluate comprised 9.7 w% of Taurine and 0.2 w% ethylene glycol. All other impurities could be depleted below the detection limit of the used NMR analytics.

[0296] Example 8a Example 8b Example 8d Example 8c Example 8e After EDBM After EDBM After EDBM After ED After ED Taurine 10.2 11.1 9.2 11 9.7 Sodium 1.2 1.1 0.8 0 0 isethionate

[0297] Sodium ditaurate 2.7 2.6 3.1 0.1 0 Ethylene Glycol 0.3 0.3 0.2 0.3 0.2

[0298]

[0299] Comparing the results with and without the use of an additional electrodialysis to purify the product solution, it becomes evident that the further use of conventional electrodialysis delivers a highly purified taurine solution with only small amounts of ethylene glycol as the main impurity. After concentrating and crystallizing the pure taurine, the resulting mother liquor, which contains mainly taurine, can be easily recycled into the crystallization process with fresh material from the electrodialysis. Since no other side products are present, the mother liquor does not have to be recycled into the ammonolysis reaction. Additionally, the risk of impurities in the final product is very low. These are advantages compared to the concentration and crystallization that occur directly after pH adjustment by electrodialysis with bipolar membranes. In that case, the mother liquor contains large amounts of sodium dodecyl sulfate and sodium isethionate, in addition to the taurine. To ensure a high overall yield, the mother liquor has to be recycled into the ammonolysis reaction. Due to the residual solubility of taurine in the mother liquor, large amounts of taurine will also be recycled. This can be avoided by using conventional electrodialysis before the crystallization to separate the side products from the taurine. In this case, the concentrate from the second electrodialysis step which comprises mainly of sodium isethionate and sodium ditaurate and only small quantities of taurine can be recycled into the ammonolysis reaction. Hence, the recycling streams can be reduced. The particular combinations of elements and features in the above detailed embodiments are exemplary only; the interchanging and substitution of these teachings with other teachings in this and the patents / applications referred to herein are also expressly contemplated. Furthermore, the content of the prior art documents referred to herein is incorporated by reference. This refers, particularly, for prior art documents that disclose standard or routine methods. In that case, the incorporation by reference has mainly the purpose to provide sufficient enabling disclosure, and avoid lengthy repetitions. As those skilled in the art will recognize, variations, modifications, and other implementations of what is described herein can occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the foregoing description is by way of example only and is not intended as limiting. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. The invention's scope is defined in the following claims and the equivalents thereto. Furthermore, reference signs used in the description and claims do not limit the scope of the invention as claimed.

[0300] Figures

[0301] The aforementioned components, as well as the claimed components and the components to be used in accordance with example aspects of the invention in the described example embodiments, are not subject to any special exceptions with respect to their size, shape, material selection and technical concept such that the selection criteria known in the pertinent field can be applied without limitations.

[0302] Additional details, example characteristics and advantages of the object of the invention are disclosed in following description of the respective figures which in an exemplary fashion show preferred embodiments according to example aspects of the invention. Any embodiment does not necessarily represent the full scope of the invention, however, and reference is made therefore to the claims and herein for interpreting the scope of the invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention as claimed.

[0303] FIG. l is a schematic representation of the method according to one example embodiment. FIG. 2 is a schematic representation of a bipolar membrane electrodialysis used in step (c) according to one example embodiment.

[0304] Hereinafter, the figures are illustrated in more detail with reference to examples. However, the present disclosure is not limited to the following figures.

[0305] FIG. 1 is schematic representation of the method for the continuous manufacture of taurine according to one example embodiment. Ethylene oxide (EO) is provided together with water in a first educt stream (1) into a continuous reactor for step (a). Sodium bisulfite (NaHSC ) is fed into the continuous reactor of step (a) as aqueous solution in a second educt stream (2). The ethylene oxide (EO) and sodium bisulfite are reacted in step (a) to obtain a first intermediate product stream (10) comprising an sodium isethionate.

[0306] The sodium isethionate from the first intermediate product stream (10) is fed into a continuous reactor of step (b). Furthermore, ammonia is fed into the continuous reactor of step (b) in excess and recycled after the reaction. The sodium isethionate and ammonia are reacted in step (b) yielding a second intermediate product stream (20) comprising an sodium taurate.

[0307] The sodium taurate from the second intermediate product stream (20) is fed into a continuous reactor of step (c). Taurine and at least one by-product are obtained, wherein the by-product is suitable for reacting sulfur dioxide to sodium bisulfite. The at least one by-product is separated from the taurine to obtain at least one by-product stream (30) comprising the at least one byproduct and a product stream (40) comprising the taurine.

[0308] The at least one by-product from the at least one by-product stream (30) is reacted with sulfur dioxide in step (d) to obtain a recycle educt stream (50) comprising sodium bisulfite. The recycle educt stream (50) may be fed into the reactor of (a), for example together with the second educt stream (2).

[0309] The taurine is crystallized from the product stream (40) in step (e) and separated from a resulting mother liquor (60). The mother liquor (60) for example may be reintroduced into step (a). FIG. 2 is a schematic representation of a bipolar membrane electrodialysis (100) used in step (c) according to one example embodiment. Particularly, Fig. 2 show step (c2) wherein the sodium taurate from the second intermediate product stream (20) is converted with the bipolar membrane electrodialysis (100) to taurine forming the product stream (40) and alkali metal hydroxide in a by-product stream (30).

[0310] The bipolar membrane electrodialysis (100) comprises chambers A (110) contacted by a bipolar membrane (BP) and an anion exchange membrane (AEM), chambers B (120) contacted by an anion exchange membrane (AEM) and a cation exchange membrane (CEM), and chambers C (130), contacted by a cation exchange membrane (CEM) and a bipolar membrane (BP). Furthermore, the bipolar membrane electrodialysis (100) comprises an anode chamber AC (140) comprising an anode (141) and contacting a cation exchange membrane (CEM), and a cathode chamber CC (150) comprising a cathode (151) and contacting a cation exchange membrane (CEM). The bipolar membrane electrodialysis (100) has three sets S (160), each comprising one chamber A (110), one chamber B (120), and one chamber C (130), wherein the chamber A (110) and B (120) are contacted by the same anion exchange membrane (AEM), and wherein chamber B (120) and C (130) are contacted by the same cation exchange membrane. The sets S (160) share bipolar membranes (BP).

[0311] The bipolar membrane electrodialysis (100) further comprises a further chamber C(131), between the anode chamber (140) and chamber A (110) of the set S (160) closest to the anode chamber (140), wherein the cation exchange membrane (CEM) contacted by the anode chamber (140) is the same as the cation exchange membrane (CEM) contacted by the further chamber C (131) and the bipolar membrane (BP) contacted by further chamber C (131) is the same as the bipolar membrane BP contacted by chamber A (110) of the set S (160 closest to the anode chamber (140).

[0312] The bipolar membrane electrodialysis (100) comprises a further chamber A (111), arranged between the chamber C (130) of the set S (160) closest to the cathode chamber (150) and the cathode chamber (150), wherein a further chamber B (121) is arranged between the further chamber A (111) and the cathode chamber (150=, wherein the cation exchange membrane (CEM) contacted by the cathode chamber (160) is the same as the cation exchange membrane (CEM) contacted by the further chamber B (121), the an anion exchange membrane (AEM) contacted by the further chamber B (121) is the same as the anion exchange membrane (AEM) contacted by the further chamber A (111), and the bipolar membrane contacted (BP) by the further chamber A (111) is the same as the bipolar membrane (BP) contacted by chamber C (130) of the set S (160) closest to the cathode chamber (150).

[0313] As electrode rinsing solution, an aqueous solution of Na2SC>4 is fed into the anode chamber (140) and the cathode chamber (150).

[0314] The second intermediate product stream (20) is fed into each chamber B (120, 121) of the bipolar membrane electrodialysis (100) and water (H2O) is fed into each chamber A (110, 111) and each chamber C (130, 131).

[0315] When applying a voltage, sodium taurate in each chamber B (120, 121) is split into sodium cations and taurate anions, wherein the sodium cations pass the anion exchange membrane (AEM) contacting chamber B (120, 121) in the direction of the anode (141) into a neighboring chamber A (110, 111) and the taurate anions pass the cation exchange membrane (CEM) contacting chamber B (120, 121) in the direction of the cathode (151) into a neighboring chamber C (130). Accordingly, the sodium taurate is removed from the second intermediate product stream. Furthermore, hydrogen cations (protons) are released from each bipolar membrane (BP) into each chamber A (110, 111) contacting the bipolar membrane (BP) in direction of the cathode (151). The released hydrogen cations may react with the taurate anions passed through the anion exchange membrane (AEM) into chamber A (110, 111) forming taurine. Accordingly, taurine is obtained in each chamber A (110, 111), resulting in the product stream (40). Furthermore, hydroxide anions are released from each bipolar membrane (BP) into each chamber C (130, 131) contacting the bipolar membrane (BP) in direction of the anode (141). The released hydroxide anions may react with the sodium cations passed through the cation exchange membrane (CEM) into chamber C (130, 131), forming sodium hydroxide. Accordingly, sodium hydroxide is obtained in each chamber C (130, 131), resulting in the byproduct stream (30).

[0316] Reference Signs and Abbreviations

[0317] EO ethylene oxide

[0318] HTau taurine BP bipolar membrane

[0319] AEC anion exchange membrane

[0320] CEC cation exchange membrane

[0321] 1 first educt stream

[0322] 2 second educt stream

[0323] 10 first intermediate product stream

[0324] 20 second intermediate product stream

[0325] 30 by-product stream

[0326] 40 product stream

[0327] 50 recycle educt stream

[0328] 60 mother liquor / recycle by-product stream 100 bipolar membrane electrodialysis

[0329] 110 chamber A

[0330] 111 further chamber A

[0331] 120 chamber B

[0332] 121 further chamb er B

[0333] 130 chamber C

[0334] 131 further chamber C

[0335] 140 anode chamber AC

[0336] 141 anode

[0337] 150 cathode chamber CC

[0338] 151 cathode

[0339] 160 set S

Claims

Claims1. A method for the continuous manufacture of taurine, comprising at least one of the steps of (a) - (c):(a) reacting an ethylene oxide and an alkali metal bisulfite to obtain a first intermediate product stream (10) comprising an alkali metal isethionate;(b) reacting the alkali metal isethionate from the first intermediate product stream (10) with ammonia to obtain a second intermediate product stream (20) comprising an alkali metal taurate; and(c) converting the alkali metal taurate from the second intermediate product stream (20) to obtain taurine and at least one by-product, wherein the by-product is suitable for reacting sulfur dioxide to alkali metal bisulfite, and separating the at least one byproduct from the taurine to obtain at least one by-product stream (30) comprising the at least one by-product and a product stream (40) comprising the taurine;and(d) optionally reacting the at least one by-product from the at least one by-product stream (30) with sulfur dioxide to obtain a recycle educt stream (50) comprising alkali metal bisulfite; and(e) optionally crystallizing the taurine from the product stream (40) and separating the crystallized taurine from a resulting mother liquor (60);wherein the method comprises at least step (c), andwherein method step (c) is performed according to the method step (c2), comprising the step of(c2) converting the alkali metal taurate from the second intermediate product stream (20) with a bipolar membrane electrodialysis (100) to taurine forming the product stream (40) and alkali metal hydroxide in a by-product stream (30),wherein the bipolar membrane electrodialysis (100) comprises at least one chamber A (110) contacted by a bipolar membrane (BP) and an anion exchange membrane (AEM),at least one chamber B (120) contacted by an anion exchange membrane (AEM) and a cation exchange membrane (CEM), and at least one chamber C (130), contacted by a cation exchange membrane (CEM) and a bipolar membrane (BP),wherein the bipolar membrane electrodialysis (100) comprise at least one anode chamber AC (140) comprising an anode (141) and contacting a membrane, preferably selected from a bipolar membrane and a cation exchange membrane, and at least one cathode chamber CC (150) comprising a cathode (151) and contacting a membrane, preferably selected from a bipolar membrane and a cation exchange membrane, wherein the bipolar membrane electrodialysis (100) comprises at least one set S (160) of three chambers, comprising one chamber A (110), one chamber B (120), and one chamber C (130), wherein the chamber A and B (110, 120) are contacted by the same anion exchange membrane, and wherein chamber B and C (120, 130) are contacted by the same cation exchange membrane,wherein the set S (160) is arranged between the anode chamber AC (140) and the cathode chamber CC (150), wherein chamber A (110) of set S (160) is closer to the anode chamber AC (140) than the cathode chamber CC (150) and / or chamber C (130) of set S (160) is closer to the cathode chamber CC (150) than the anode chamber AC (140).

2. The method according to claim 1, wherein the ethylene oxide and the alkali metal bisulfite are reacted at a temperature in the range of > 5 °C to < 200 °C, preferably > 10 °C to < 190 °C, preferably > 15 °C to < 180 °C, preferably > 20 °C to < 170 °C, preferably > 30 °C to < 160 °C, preferably > 40 °C to < 150 °C, preferably > 50 °C to < 140 °C, preferably > 30 °C to < 130 °C, for example 80 °C.

3. The method according to claim 1 or 2, wherein the ethylene oxide and the alkali metal bisulfite are reacted at a pressure in the range of > 0 bar to < 100 bar, preferably > 1 bar to < 90 bar, preferably > 1.5 bar to < 80 bar, preferably > 2 bar to < 70 bar, preferably > 2.5 bar to < 60 bar, preferably > 3 bar to < 50 bar, preferably > 3.5 bar to < 40 bar,preferably > 4 bar to < 25 bar, preferably > 4.5 bar to < 15 bar, preferably > 4.8 bar to < 10 bar, preferably > 5 bar to < 8 bar, for example 5.5 bar.

4. The method according to any one of claims 1 to 3, wherein the alkali metal isethionate is provided for reaction with the ammonia in a molar ratio of alkali metal isethionate to ammonia in the range of < 1:0.1 to > 1:100, preferably < 1:0.5 to > 1:90, preferably < 1:1 to > 1:80, preferably < 1:1.5 to > 1:70, preferably < 1:2 to > 1:60, preferably < 1:2.5 to > 1:50, preferably < 1:3 to > 1:45, preferably < 1:3.5 to > 1:40, preferably < 1:4 to > 1:35, preferably < 1:4.5 to > 1:30, preferably < 1:5 to > 1:25, preferably < 1:5.5 to > 1 :20, preferably < 1 :6 to > 1:18, preferably < 1 :6.5 to > 1 : 17, preferably < 1:7 to > 1:16.

5. The method according to any one of claims 1 to 4, wherein the alkali metal isethionate and the ammonia are reacted until a yield of the alkali metal taurate in the range of > 10% to < 100% based on the theoretical yield of alkali metal taurate based on the amount of alkali metal isethionate provided is reached, preferably > 35% to < 95%, preferably > 50% to < 92%, preferably > 65% to < 90%, preferably > 67% to < 87%, preferably > 70% to < 85%.

6. The method according to claim 1, wherein the membrane contacted by the anode chamber AC (140) is a cation exchange membrane (CEM), wherein a further chamber C (131) is arranged between the anode chamber AC (140) and chamber A (110) of the set S (160), wherein the cation exchange membrane (CEM) contacted by the anode chamber (140) is the same as the cation exchange membrane (CEM) contacted by the further chamber C (131) and the bipolar membrane (BP) contacted by further chamber C (131) is the same as the bipolar membrane (BP) contacted by chamber A (110) of the set S (160); andwherein the membrane contacted by the cathode chamber CC (150) is a cation exchange membrane (CEM), wherein a further chamber A (111) is arranged between the chamber C (130) of the set S (160) and the cathode chamber CC (150), and wherein a further chamber B (121) is arranged between the further chamber A (111) and the cathodechamber CC (150), wherein the cation exchange membrane (CEM) contacted by the cathode chamber CC (150) is the same as the cation exchange membrane (CEM) contacted by the further chamber B (121), the an anion exchange membrane (AEM) contacted by the further chamber B (121) is the same as the anion exchange membrane (AEM) contacted by the further chamber A (111), and the bipolar membrane (BP) contacted by the further chamber A (111) is the same as the bipolar membrane (BP) contacted by chamber C (130) of the set S (160).

7. The method according to any one of claims 1 to 6, wherein the second intermediate product stream (20) is fed into each chamber B (120, 121) of the bipolar membrane electrodialysis (100) and water is fed into each chamber A (110, 111) and each chamber C (130, 131).

8. The method according to any one of claims 1 to 7, wherein the product stream (40) is adjusted to a pH in the range of 5-6 and / or the isoelectric point of taurine, and subjected to an electrodialysis (ED) step, resulting in a cleaned product stream (40) and a third by-product stream.

9. The method according to any one of claims 1 to 8, wherein the method step (d) may be performed according to method step (d2), comprising the step of(d2) reacting the by-product from the by-product stream (30) with sulfur dioxide to alkali metal bisulfite in the recycle educt stream (50).

10. The method according to any one of claims 1 to 9, wherein the recycle educt stream (50) comprising alkali metal bisulfite may comprise alkali metal bisulfite in an amount of > 5 wt.-% to < 55 wt.-% based on the volume of the water, preferably > 15 wt.-% to < 45 wt.-%, more preferably > 25 wt.-% to < 35 wt.-%,11. The method according to any one of claims 1 to 10, wherein in step (e) taurine is concentrated in the product stream (40) by heating the product stream (40) to a temperature in the range of > 70 °C to < 100 °C, preferably > 80 °C to < 95 °C, preferably > 85 °C to < 90 °C, and a pressure in the range of > 0.1 bar to < 1 bar, preferably > 0.5 bar to < 0.9 bar, > 0.7 bar to < 0.8 bar.

12. The method according to claim 11, wherein the product stream (40) is heated via a heat exchanger, wherein the heat exchange fluid has been heated by the reaction in method step (a).

13. The method according to any one of claims 1 to 12, wherein the mother liquor (60) obtained in step (e) after removing the taurine is introduced in step (a) or (b) as recycle by-product stream (60).

14. Apparatus for conducting the method according to any one of claims 1 to 13, comprising at least one of the following (a) - (c):(a) continuous reactor comprising an input for the ethylene oxide and an input for the alkali metal bisulfite, and an output for the first intermediate product stream (10) comprising the alkali metal isethionate;(b) a continuous reactor comprising an input for the alkali metal isethionate from the first intermediate product stream (10) and an input for ammonia, and an output for the second intermediate product stream (20) comprising an alkali metal taurate; and (c) a continuous reactor comprising an input for the alkali metal taurate from the second intermediate product stream (20), and an output for at least one by-product stream (30) comprising the at least one by-product and an output for the product stream (40) comprising the taurine;and(d) optionally a continuous reactor comprising an input for the at least one byproduct from the at least one by-product stream (30) and an input for sulfur dioxide, and an output for the recycle educt stream (50) comprising alkali metal bisulfite; and (e) optionally a continuous reactor for crystallizing the taurine comprising an input for the product stream (40), a separator, an output for the crystallized taurine and an output for the resulting mother liquor (60);wherein the apparatus comprises at least the continuous reactor (c), andwherein the continuous reactor (c) is a bipolar membrane electrodialysis (100) for converting the alkali metal taurate from the second intermediate product stream (20) to taurine forming the product stream (40) and alkali metal hydroxide in a by-product stream (30).

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