Method for producing synthetic oligonucleotides and remover for removing impurities from organic wash solvents used in oligonucleotide synthesis

Abstract

The present invention provides a method for utilizing a blended composition of acetonitrile and toluene as an organic wash solvent in the production of synthetic oligonucleotides that yields higher synthetic oligonucleotide yields than pure acetonitrile wash solvents. The method also provides a method for removing one or more impurities from an acetonitrile and toluene containing wash solvent received as a waste stream from an oligonucleotide synthesis process. The method includes adding at least one of an iodine-reactive compound, a sulfur-reactive compound, and / or an acid-reactive compound to the waste stream, and fractionating the waste stream. The fractionation produces a top fraction and a bottom fraction, where the top fraction includes the acetonitrile and the toluene, and the bottom fraction includes the one or more impurities.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Patent Application No. 18 / 225,010, filed on July 21, 2023, and claims the benefit of U.S. Provisional Application No. 63 / 392,441, filed on July 26, 2022, both of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present technical field generally relates to methods and systems for purifying waste streams including acetonitrile and toluene, and more specifically, one or more reactive compounds are added to the waste stream, which enables recovery and subsequent recycling of a substantially purified mixture of acetonitrile and toluene. In some cases, when used as a wash solvent in an oligonucleotide synthesis process, the recycled and purified mixture of acetonitrile and toluene produces a higher purity oligonucleotide than pure acetonitrile. Background Art

[0004] Many chemical processes utilize acetonitrile as a solvent or washing liquid, resulting in the generation of low-grade acetonitrile waste streams. When these processes are performed at a manufacturing scale, the volume of the low-grade acetonitrile waste streams generated can be quite large. For example, oligonucleotide (DNA and RNA) synthesis is usually carried out via a four-step cycle (deblocking, activation / coupling, end-capping and oxidation), which is repeated for each nucleotide added until the desired sequence is obtained. Between each step, the oligonucleotide bound to the carrier is usually washed with high-purity (i.e. 100%) acetonitrile to reduce residual reagents from the previous step. This results in the generation of a large amount of acetonitrile waste streams, wherein when manufacturing about 1 metric ton of active pharmaceutical ingredients (API) based on oligonucleotides, about 2,000 metric tons of acetonitrile are used.

[0005] Synthetic oligonucleotide sequences show the prospect of being used for treatment, diagnosis and drug target validation application in the biopharmaceutical industry, and the quantity of oligonucleotide-based drugs in preclinical or clinical trials is constantly increasing. However, API manufacturers based on oligonucleotides face the expense and difficulty of managing the purchase of a large amount of pure acetonitrile and the disposal of a large amount of waste streams based on acetonitrile produced. Therefore, in industry, there is an urgent need to reclaim and purify acetonitrile waste streams to produce a method and system for washing solvents based on acetonitrile suitable for reuse. In addition, according to the subsequent detailed description and the appended claims, other desired features and characteristics will become apparent. Summary of the invention

[0006] The present disclosure provides the process and method for removing one or more impurities from the waste stream produced by the oligonucleotide process, and these one or more impurities comprise iodine-containing compounds, sulfur-containing compounds and / or alkaline nitrogen-containing compounds.In this case, the waste stream contains acetonitrile and toluene that are rich in acetonitrile and one or more impurities than composition ratio.One or more reductants / scavengers (comprising iodine-reactive compounds, sulfur-reactive compounds and / or acidic reactive compounds) are added in the waste stream, and during fractionation, the top fraction comprises acetonitrile and toluene that are in azeotropic composition, and the bottom fraction contains one or more impurities.The top fraction can be further processed to remove any residual impurity, and the acetonitrile and toluene mixture of purifying can be recycled in the oligonucleotide process as washing solvent.

[0007] In one embodiment, the present disclosure provides a method for processing a waste stream, the method comprising: receiving a waste stream comprising acetonitrile, toluene, and one or more iodine-containing compounds; adding an iodine-reactive compound to the waste stream; and fractionating the waste stream to produce a top fraction and a bottom fraction. In this case, the top fraction comprises acetonitrile and toluene of the waste stream, and the bottom fraction comprises the one or more iodine-containing compounds of the waste stream.

[0008] In another embodiment, the present disclosure provides a method for processing a waste stream, the method comprising: receiving a waste stream comprising acetonitrile, toluene, and one or more sulfur-containing compounds; adding a sulfur-reactive compound to the waste stream; and fractionating the waste stream to produce a top fraction and a bottom fraction. In this case, the top fraction includes acetonitrile and toluene of the waste stream, and the bottom fraction includes one or more sulfur-containing compounds of the waste stream.

[0009] In yet another embodiment, the present disclosure provides a method for processing a waste stream, the method comprising: receiving a waste stream comprising acetonitrile, toluene, and basic nitrogen-containing compounds; adding an acidic reactive compound to the waste stream; and fractionating the waste stream to produce an overhead fraction and a bottom fraction. In this case, the overhead fraction comprises acetonitrile and toluene of the waste stream, and the bottom fraction comprises basic nitrogen-containing compounds of the waste stream.

[0010] In another embodiment, the present disclosure provides a method for producing a synthetic oligonucleotide, the method comprising: washing a reaction vessel containing one or more components of an oligonucleotide synthesis process with a co-mixed washing solution of at least acetonitrile and toluene, wherein acetonitrile is at least 70% of the co-mixed washing solution; and recovering the synthetic oligonucleotide. In this case, the synthetic oligonucleotide is recovered at a minimum oligonucleotide purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic diagram of a system and method for purifying a waste stream according to an exemplary embodiment. DETAILED DESCRIPTION

[0012] The following detailed description is merely exemplary in nature and is not intended to limit the various embodiments or the application and uses thereof. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.

[0013] Provided herein is a method, system and technique for purifying oligonucleotide waste streams.Technique, method and system of the present invention provide pre-treatment and recirculate the technical simplification and economically advantageous mode of the waste stream received from oligonucleotide synthesis.As previously mentioned, oligonucleotide synthesis techniques (for example, solid phase synthesis) utilize a large amount of solvents based on acetonitrile as washing solvents, and during this type of process, the solvent based on acetonitrile is contaminated by many impurities.

[0014] Oligonucleotide synthesis process usually needs pure acetonitrile washing solvent, and therefore, containing acetonitrile waste stream can not be reused.Therefore, need to contain acetonitrile waste stream purification to for recycling back to acceptable level in synthesis process.It has been found that this type of synthesis process contaminates acetonitrile with various compounds, this various compounds comprises toluene (for example, as contaminated via removing blocking agent), iodine (for example, as contaminated via oxidizing agent), such as the sulfur-containing compound of mercaptan (for example, as contaminated by sulfurizing agent and activating agent) and such as the alkaline nitrogen-containing compound of alkylamine (for example, as contaminated by oxidizing agent, end-capping agent and activating agent).In this case, be difficult to remove such compounds to acceptable degree with acetonitrile purified to recycling and / or reclaim required purity.

[0015] Importantly, it has been found that the substantially pure mixture of acetonitrile and toluene can be utilized as suitable washing solvent in the oligonucleotide synthesis process, rather than using pure acetonitrile.Therefore, it has been confirmed that the waste stream needs to be purified into the substantially pure mixture of acetonitrile and toluene (that is, removing other impurities, such as iodine, mercaptan and alkylamine), so that in the synthesis process, the originally unavailable contaminated acetonitrile waste stream is reused as washing solvent.In addition, it has also been surprisingly found that at some compositions, compared to the pure acetonitrile washing solvent, in the oligonucleotide synthesis process, the mixture of acetonitrile and toluene used for purification produces more highly purified oligonucleotide as washing solvent.Therefore, the recycling of the waste stream of purification not only causes the significant minimization (for example, because washing solvent is recycled back in the oligonucleotide synthesis process rather than being discarded) of the washing solvent based on acetonitrile of waste, and uses the waste stream of purification to also cause more highly purified oligonucleotide.

[0016] As described in relation to U.S. Pat. No. 10,336,690 (the disclosure of which is expressly incorporated herein), this can be achieved via fractionation combined with contact with one or more absorbents / adsorbents. In this case, the waste stream can be fed to a fractionation / distillation column, wherein during the fractionation / distillation, the top fraction (distillate) of the column includes acetonitrile and lower boiling point compounds and / or volatile compounds (e.g., toluene, some water, and most of the iodine, mercaptans, and alkylamines), while the bottom fraction includes the higher boiling point components of the waste stream. As also described in relation to U.S. Pat. No. 10,336,690, the condensed top stream can be sent to a series of absorbers, wherein when contacted with different absorbents, a purified stream containing acetonitrile can be obtained. However, in this case, due to the relatively high concentration of contaminants in the top fraction of the column, the removal of impurities consumes a large amount of absorbent. Therefore, it has been determined that it may be advantageous to remove one or more of these contaminants before contacting the absorber. This can reduce the cost of the purification process because both the size of the column and / or the amount of absorbent / adsorbent used can be reduced.

[0017] As used herein, the term "purification" and variants thereof refer to reducing the amount of one or more impurities in a composition. As a general concept, purification can be achieved via many techniques known in the art, depending on the properties of the composition to be purified and the impurities to be reduced. Purification does not necessarily produce a pure product that is completely free of all impurities or any specific impurities. In addition, some methods and systems described herein utilize multiple purification steps, including fractionation of acetonitrile-containing waste streams. In some embodiments, fractionation is an initial purification step.

[0018] refer to Figure 1 In one exemplary embodiment, fractionation of waste stream 102 is performed using a system 100 having a fractionation zone 103 including a distillation or fractionation column 106. In a specific embodiment, fractionation / distillation column 106 contains internals (such as packing, trays, screens, bubble caps or similar mechanical configurations) that provide multiple stages, step-wise contacting of vapor-liquid streams flowing through the column. The number of stages and the type of internals will vary depending on the specific composition of the acetonitrile-containing waste stream, inlet location, reflux ratio, desired column efficiency, etc. Therefore, the internal profile of fractionation / distillation column 106 can vary from one application to another.

[0019] Waste stream 102 may be derived from a variety of sources and contain some impurities with boiling points higher than acetonitrile and some impurities with boiling points lower than acetonitrile. In this regard, some waste stream purification processes rely on taking a "heart cut" of the distillate, wherein two fractionation columns are used to first separate acetonitrile and lower boiling impurities (in a first column top fraction) from higher boiling impurities (in a first column bottom fraction), and a second fractionation column is used to separate acetonitrile and other similar boiling point materials (in a second column bottom fraction) from lower boiling impurities (in a second column top fraction).

[0020] However, as described herein, such complex fractionation through two columns is not required. Instead, in some embodiments, fractionation zone 103 comprises a single column 106, wherein a single top fraction 108 is collected until a single fractionation point (e.g., just above the boiling point of acetonitrile or acetonitrile-toluene mixture, such as about 81° C. to 82° C. at standard pressure (1 ATM)).

[0021] As used herein, the term "overhead" fraction means the fraction removed from the upper portion of the fractionation column. The top fraction includes components of the initial mixture that have lower boiling points than components found in the "bottoms" (i.e., the fractions retained in and / or removed from the lower portion of the fractionation column). The top fraction 108 includes acetonitrile and low-temperature boiling impurities. In some embodiments, the top fraction 108 may also include some higher boiling impurities, such as toluene and iodine due to azeotropic behavior with acetonitrile.

[0022] The methods and systems described herein achieve further purification of the top fraction 108 by condensing the top fraction 108 and contacting the condensed top fraction 108 with one or more adsorbents (e.g., adsorbents 112, 118, and 124 contained within columns 110, 116, and 122, respectively). The nature of the specific adsorbent used in the subsequent purification steps is determined by the type and level of impurities remaining in the top fraction 108, and is therefore affected by the source of the waste stream 102.

[0023] As mentioned above, many scientific and manufacturing processes utilize acetonitrile and toluene streams as solvents or as scrubbing solutions and thus generate acetonitrile waste streams. Various processes require acetonitrile and toluene streams of varying purity and / or may require a certain degree of purity relative to one or more specific impurities.

[0024] One such process that produces particularly large amounts of acetonitrile waste is the manufacture of synthetic oligonucleotides (DNA and RNA). Oligonucleotide synthesis is usually carried out via a four-step cycle (deblocking, activation / coupling, end-capping and oxidation), wherein pure acetonitrile is washed between each cycle. Since each step in the cycle uses different reagents, the acetonitrile waste stream generated from the washing after each step may be contaminated by impurities of different types and levels.

[0025] For example, each oligonucleotide synthesis cycle usually starts from the nucleotide of the sealing that is covalently connected to the carrier.The nucleotide of sealing is deblocked in the first step, usually via reacting in the presence of toluene or methylene dichloride with an acidic solution such as 3% trichloroacetic acid (TCA) or 3% dichloroacetic acid (DCA).Once the blocking reaction is completed, reagent is discharged, and the oligonucleotide (attached to the carrier) of blocking is washed with a washing solvent based on acetonitrile.The impurity found in the gained acetonitrile waste stream may include unreacted reagent, residual solvent and / or the by product of blocking reaction.For example, the impurity in the blocking acetonitrile waste stream may include toluene, acetic acid, trichloromethane and / or propionitrile.The impurity in the blocking acetonitrile waste stream accounts for 0.1 % by weight to 30 % by weight of waste stream 102 usually.In an exemplary embodiment, waste stream 102 is included in the acetonitrile waste produced during the acetonitrile washing step after the blocking step of oligonucleotide synthesis.

[0026] The second step in the oligonucleotide synthesis cycle relates to the oligonucleotide of activation and coupling to go sealing.Activation is carried out via contacting with any suitable activator known in the art.After activation, the material of the binding carrier is treated with iodine and water in the presence of a weak base (for example, pyridine, lutidine or collidine), and the weak base is oxidized to four coordinated phosphotriesters by the phosphite triester.The oligonucleotide of going sealing is coupled (i.e. reacted) with phosphoramidite to form a phosphite oligomer.Phosphoramidite is selected from all available phosphoramidites differently, and wherein reaction is carried out as known in the art.

[0027] In one embodiment, the waste stream 102 is a waste stream of acetonitrile, wherein ...

[0028] Usually, during the coupling step, only a part of the nucleotide to be sealed is reacted with phosphoramidite, and any unreacted nucleotide must be blocked.End-blocking is carried out by contacting unreacted nucleotide with a certain amount of diacetic anhydride and a certain amount of N-methylimidazole.After coupling, reagent is discharged / propelled through tower by a washing solvent based on acetonitrile, and the oligonucleotide grown on the washing solid support.Equally, the impurity found in the gained acetonitrile waste stream may include the by product of unreacted reagent, residual solvent or end-blocking reaction.For example, the impurity in the blocked acetonitrile waste stream may include N-methylimidazole, acetic acid, diacetic anhydride, lutidine, pyridine, tetrahydrofuran, propionitrile and / or toluene.The impurity in the blocked acetonitrile waste stream accounts for 0.1 % by weight to 30 % by weight of waste stream 102 usually equally.In an exemplary embodiment, waste stream 102 is included in the acetonitrile waste produced during the acetonitrile washing step after the end-blocking step of oligonucleotide synthesis.

[0029] Finally, the phosphite oligomer formed in the activation / coupling step is oxidized or sulfurized.Oxidation (for example, via reaction with iodine) is realized in the presence of water and pyridine.Vulcanization is realized with the reaction of phenylacetyl disulfide or similar chemical entities.After oxidation or sulfurization, reagent is discharged / propelled through tower with washing acetonitrile solution.The solid support containing the oligonucleotide of growth is washed again with acetonitrile washing stream.The impurity found in the gained acetonitrile waste stream may include the by product of unreacted reagent, residual solvent or oxidation reaction.For example, the impurity in the oxidation acetonitrile waste stream may include organic and inorganic iodine, toluene, tetrahydrofuran (THF), pyridine, propionitrile and water.In an exemplary embodiment, waste stream 102 is included in the acetonitrile waste produced during the acetonitrile washing step after the synthetic oxidation step of oligonucleotide.

[0030] It will be appreciated that the types and amounts of impurities found in the wash stream from each of the above steps may vary. The methods and systems described herein may be used to purify a waste stream 102 from a wash step following any particular step, or may be used to purify a waste stream 102 that has been collected and pooled (e.g., in a collection tank 104) from a wash step involving deblocking, coupling, capping, and / or oxidation as previously described.

[0031] The types and amounts of impurities in the overhead fraction 108 may vary depending on the source of the waste stream 102, and the appropriate adsorbent may be selected based on these compositions and the final grade (ie, overall purity) of the desired acetonitrile / toluene end product.

[0032] For example, the top fraction obtained by distillation of the collected waste generated by oligonucleotide synthesis may contain substances such as water and toluene, as well as various other impurities of the waste stream in concentrations up to 30% by weight. These impurities can be organic and / or inorganic iodine-containing compounds, sulfur-containing compounds such as mercaptans (e.g., ethylthiotetrazole (ETT), phenylacetyl disulfide (PADS)), basic nitrogen-containing compounds (e.g., pyridine, lutidine, picoline, 1-methylimidazole), various alcohols (e.g., methanol), esters (e.g., acetic acid, dichloroacetic acid), nitriles (e.g., propionitrile) and / or halogenated hydrocarbons (e.g., chloroform / dichloromethane).

[0033] Figure 1 An exemplary embodiment of a system 100 is illustrated for purifying a waste stream 102 received from an oligonucleotide synthesis process to a purity acceptable for recycling. In this case, purification occurs via the system 100, which includes a fractionation zone 103, which includes a collection tank 104 and a fractionation / distillation column 106, and an adsorbent zone 130, which includes a first absorber 110, a second absorber 116, and a third absorber 122.

[0034] like Figure 1 As illustrated, the fractionation section 103 includes a collection tank 104 and a fractionation / distillation column 106. In this case, the waste stream 102 is passed into the fractionation section 103 and collected in the collection tank 104. The collection tank 104 can be used to combine the waste streams 102 into pools so that various forms of the waste stream 102 (e.g., as described above with respect to different compositions of deblocking, coupling, capping, and / or oxidation steps) are maintained in a common volume within the collection tank 104.

[0035] Once waste stream 102 enters collection tank 104, it may come into contact with one or more reactive compounds (ie, reducing compounds, scavengers, etc.), and some of the impurities within waste stream 102 react with waste stream 102 and are subsequently precipitated from the waste stream.

[0036] For example, the first reactive compound 151 can be added to the collection tank 104 and react with some components of the waste stream 102. In this case, the first reactive compound 151 can be an iodine-reactive compound that reacts with (e.g., reduces) one or more iodine-containing compounds within the waste stream 102. For example, the iodine-reactive compound can be sodium thiosulfate, and the sodium thiosulfate anion reacts with the iodine of the iodine-containing compound, thereby reducing the iodine and subsequently precipitating the iodine from the waste stream 102, as illustrated by the following representative reaction.

[0037] I2+2Na2S2O3→2NaI+Na2S4O6

[0038] In a second example, a second reactive compound 152 can be added to the collection tank 104 and react with some components of the waste stream 102. In this case, the second reactive compound 152 can be a sulfur-reactive compound that reacts with (e.g., reduces) one or more sulfur-containing compounds (e.g., ETT, PADS) such as mercaptans within the waste stream 102. For example, the sulfur-reactive compound can be silver nitrate that reacts with the sulfur-containing compounds, thereby reducing the sulfur-containing compounds and subsequently precipitating the sulfur-containing compounds from the waste stream 102, as illustrated in the following representative reaction.

[0039] 2RS-SR+2H2O+AgNO3→3RS-Ag+RSO2H+2HNO3

[0040] In a third example, a third reactive compound 153 can be added to the collection tank 104 and react with some components of the waste stream 102. In this case, the third reactive compound 153 can be an acidic reactive compound that reacts with (e.g., reduces) one or more basic nitrogen-containing compounds such as alkylamines (e.g., pyridine, lutidine, picoline, 1-methylimidazole) within the waste stream 102. In this case, the acidic reactive compound can be a carboxylic acid (e.g., formic acid) that reacts with (e.g., reduces) the basic nitrogen-containing compound and subsequently precipitates the basic nitrogen-containing compound from the waste stream 102, as illustrated in the following representative reaction.

[0041] R1,R2-N-H+HCOOH→R1-R2-N-COH+H2O

[0042] In some cases, two or more of reactive compounds 151, 152, and / or 153 may be added simultaneously or subsequently to waste stream 102 within collection tank 104, and each of reactive compounds 151, 152, and / or 153 may react in combination with compounds within waste stream 102.

[0043] For example, the iodine-reactive compound 151 can be added at the same time as, before, or after the sulfur-reactive compound 152, and both the iodine-reactive compound 151 and the sulfur-reactive compound 152 react with the iodine-containing compound and the sulfur-containing compound, respectively, within the waste stream 102. In this case, the sulfur-reactive compound 152 can further react with the reduced iodine-containing compound to further precipitate iodine from the waste stream 102. For example, where the iodine-reactive compound 151 is sodium thiosulfate and the sulfur-reactive compound 152 is silver nitrate, the silver nitrate can further reduce the iodide produced via the reaction of the sodium thiosulfate and the volatile iodine, and enhance the recovery (e.g., precipitation) of iodine from the waste stream 102. However, the addition of silver nitrate is not required to reduce and precipitate iodide, and it is possible to fully reduce and precipitate iodine without the use of silver nitrate.

[0044] In another example, the iodine-reactive compound 151 can be added at the same time, before, or after the acid-reactive compound 153, and both the iodine-reactive compound 151 and the acid-reactive compound 153 react with the iodine-containing compound and the basic nitrogen-containing compound, respectively, within the waste stream 102. In this case, the chemical interaction between the iodine-reactive compound 151 and the acid-reactive compound 153, as well as the intermediates formed when reducing the iodine-containing compound and the basic nitrogen-containing compound, can work together to reduce the sulfur-containing compounds of the waste stream 102. For example, in the case where the iodine-reactive compound 151 is sodium thiosulfate and the acid-reactive compound 153 is formic acid, the interaction of the sodium thiosulfate and formic acid with each of the iodine-containing compound and the basic nitrogen-containing compound can produce a matrix effect, and the intermediates formed by these reactions react with (e.g., reduce) the sulfur-containing compound (e.g., thiol) in the waste stream 102. In this regard, the use of iodine-reactive compound 151 and acid-reactive compound 153 (eg, reducing the sulfur-containing compound without using sulfur-reactive compound 152) can achieve the desired reduction of all three impurities (eg, iodine-containing compound, sulfur-containing compound, and basic nitrogen-containing compound).

[0045] In yet another example, all three reactive compounds 151, 152, and / or 153 may be added to the waste stream 102 within the collection tank 104, and each of the reactive compounds 151, 152, and / or 153 may react simultaneously and / or in combination to reduce each of the iodine-containing compound, the sulfur-containing compound, and the basic nitrogen-containing compound within the waste stream 102. In this case, each of the iodine-containing compound, the sulfur-containing compound, and the basic nitrogen-containing compound may be precipitated from the waste stream 102 by reaction with the reactive compounds 151, 152, and / or 153 and the intermediates produced by these reactions.

[0046] although Figure 1It is illustrated that each of the reactive compounds 151, 152, and / or 153 is added to the collection tank 104 separately (i.e., through different feed tubes), but two or more reactive compounds may be added in combination. For example, the reactive compounds 151 and 152 may be added to the collection tank 104 through the same feed tube rather than through separate feed tubes, such as Figure 1 exemplified. The foregoing also applies to any combination of reactive compounds 151, 152, and 153, wherein each of the components may be added individually or in any combination, including all three reactive compounds 151, 152, and 153 added to the collection tank 104 through the same feed pipe. Alternatively, in some embodiments, any one of the reactive compounds 151, 152, and / or 153 may be added to the feed stream 105 instead of to the collection tank 104. In this case, the collection tank 104 may be removed from the system 100, and each of the reactive compounds 151, 152, and / or 153 may be metered into the waste stream 102 (e.g., the collection tank 104 is removed from the fractionation zone 103, wherein the waste stream 102 is inline with each of the reactive compounds 151, 152, and / or 153, and at the point where the reactive compounds are added to the waste stream 102, the waste stream 102 is converted into the feed stream 105.)

[0047] The waste stream 102 and each of the reactive compounds 151, 152 and / or 153 are collected in a collection tank 104 and fed as a feed stream 105 to a fractionation / distillation column 106. The fractionation / distillation column 106 is used to separate / fractionate the components of the feed stream 105 into a top fraction 108 and a bottom fraction 107.

[0048] The overhead fraction 108 contains at least a majority of the acetonitrile originally present in the waste stream 102. For example, the overhead fraction 108 can contain more than 75%, such as more than 85%, such as more than 95% of the acetonitrile originally contained in the waste stream 102. That is, the overhead fraction 108 can contain from about 75% to about 100%, such as from about 85% to about 100%, such as from about 95% to about 100% of the acetonitrile originally contained in the waste stream 102.

[0049] In addition to acetonitrile, the top fraction 108 may also contain water, toluene, and other lower boiling impurities. For example, in the case where about 1 wt % (e.g., 10,000 ppm) of water is present in the wastewater stream 102, the top fraction 108 may contain up to 10,000 ppm, however more preferably 100 ppm, still more preferably 50 ppm, and more preferably 30 ppm of water. In this case, the water may form an azeotrope with one or more components of the top fraction 108, such as an azeotrope formed with acetonitrile. In this case, and as will be further described herein, the water may be removed from the top fraction 108 by a variety of methods, including contact with a desiccant.

[0050] An "azeotrope" (or "azeotrope") composition is a unique combination of two or more components. Azeotropes can be homogeneous (having one liquid phase) or heterogeneous (having two liquid phases). Azeotrope compositions can be characterized in various ways. For example, at a given pressure, an azeotrope composition boils at a constant characteristic temperature that is either higher than the higher boiling component (maximum boiling azeotrope) or lower than the lower boiling component (minimum boiling azeotrope). However, in the case of a heterogeneous azeotrope, the boiling point of the azeotrope will always be lower than the boiling point of the lower boiling component. In the case of a heterogeneous azeotrope, at the characteristic temperature, the composition of each of the two liquid phases and the gas phase will remain constant when boiling. Azeotrope compositions do not fractionate when boiling or evaporating. Therefore, the components of an azeotrope composition cannot be separated during a phase change.

[0051] Azeotrope compositions are also characterized in that, at the characteristic azeotrope temperature, the bubble point pressure of the liquid phase is the same as the dew point pressure of the vapor phase.

[0052] The behavior of azeotropic compositions is in contrast to the behavior of zeotropic compositions, in which the liquid composition changes to a considerable extent during boiling or evaporation.

[0053] For purposes of this disclosure, an azeotrope composition is characterized in that it boils at a constant characteristic temperature that is below the boiling points of two or more components (the minimum boiling azeotrope) and thus has the same composition in both the vapor and liquid phases.

[0054] However, it will be appreciated by those of ordinary skill in the art that the composition and boiling point of an azeotrope composition will vary to some extent at different pressures. Thus, depending on the temperature and / or pressure, an azeotrope composition may have a varying composition. Thus, it will be appreciated by those of ordinary skill in the art that a range of compositions rather than fixed compositions may be used to define an azeotrope composition. Additionally, an azeotrope may be defined based on the exact weight percentage of each component of a composition characterized by a fixed boiling point at a specified pressure.

[0055] Azeotropes or azeotrope-like compositions can be identified in a number of different ways.

[0056] For the purposes of this disclosure, azeotropes or azeotrope-like compositions are identified experimentally using an ebulliometer (Walas, Phase Equilibria in Chemical Engineering, Butterworth-Heinemann, 1985, 533-544). An ebulliometer is designed to measure the boiling point of a liquid extremely accurately by measuring the temperature of vapor-liquid equilibrium.

[0057] The boiling points of each component are measured at a constant pressure. The skilled person will know that for binary azeotropes or azeotrope-like compositions, the boiling point of one of the components of the composition is initially measured. The second component of the composition is then added in varying amounts, and the boiling point of each of the resulting compositions is measured at the constant pressure using an ebulliometer. In the case of a ternary azeotrope, the initial composition will contain a binary blend, and the third component is added in varying amounts. The boiling point of each of the resulting ternary compositions is measured at the constant pressure using an ebulliometer.

[0058] The measured boiling points are plotted against the composition of the composition tested, e.g., for a binary azeotrope, the amount of the second component added to the composition (expressed in weight % or mole %). The presence of an azeotrope composition can be identified by observing a maximum or minimum boiling temperature that is higher or lower than the boiling point of any individual component.

[0059] The skilled artisan will appreciate that azeotropes or azeotrope-like compositions are identified by comparing the change in boiling point of the composition relative to the boiling point of the first component when a second component is added to the first component. Thus, in order to measure the change in boiling point, it is not necessary to calibrate the system to the reported boiling point of a specific component.

[0060] In the case where the top fraction 108 contains toluene, the amount of toluene present in the top fraction 108 can be based on the azeotropic interaction between acetonitrile and toluene or the composition of toluene present in the feed stream 105. For example, in the case of the azeotropic interaction between acetonitrile and toluene, the relative weight percentages of acetonitrile and toluene of the top fraction 108 can depend on the operating temperature and pressure of the fractionation / distillation column 106. For example, in the case where the fractionation / distillation column 106 is operated at a temperature between 80° C. and 86° C. and a pressure of 1 ATM, the azeotropic composition comprises about 76 weight percent acetonitrile and 24 weight percent toluene. In a second example, the relative weight percentage of toluene in the feed stream 105 can be less than the relative weight percentage of toluene in the acetonitrile and toluene azeotrope (e.g., the relative weight percentage of toluene in the feed stream 105 is less than 24 weight percent). In this case, the top fraction 108 can contain substantially the same relative weight percentages of acetonitrile and toluene as the feed stream 105. For example, in the case where the feed stream 105 contains about 80 relative weight percent acetonitrile and 20 relative weight percent toluene, the top fraction 108 also contains 80 relative weight percent acetonitrile and 20 relative weight percent toluene (e.g., the relative weight percent of toluene does not increase to the azeotropic composition of 24 relative weight percent toluene). Therefore, the relative weight percent of toluene in the top fraction 108 can be based on the azeotropic interaction between acetonitrile and toluene at the operating temperature and pressure of the fractionation / distillation column 106, or less than the azeotropic composition when the feed stream 105 contains a lower relative weight percent of toluene than the azeotropic composition. In other words, the relative weight percents of acetonitrile and toluene can be based on at least the azeotropic composition of acetonitrile and toluene, or can be a higher relative weight percent than the azeotropic composition when the feed stream 105 contains less toluene than the azeotropic composition.

[0061] However, the fractionation / distillation column 106 may also be operated at various temperatures and pressures to achieve the desired acetonitrile recovery, and the relative composition of acetonitrile and toluene may be varied. In addition, although illustrated as a single distillation column 106, and in the case of a pressure swing distillation, more than one column 106 (e.g., two columns 106 in series operated at different temperatures and pressures) may be used. Thus, in this regard, although described as involving an azeotropic composition of 76 wt % acetonitrile and 24 wt % toluene, other azeotropic compositions of acetonitrile and toluene are possible.

[0062] In addition to acetonitrile and toluene, the overhead fraction 108 may contain one or more impurities such as iodine, sulfur-containing compounds such as mercaptans (e.g., ethylthiotetrazolyl (ETT), BMT, phenylacetyl disulfide (PADS)), basic nitrogen-containing compounds (e.g., pyridine, lutidine, picoline, N-methylimidazole), and esters (e.g., acetic acid, dichloroacetic acid), each of which may be carried into the overhead fraction 108 due to the boiling point of the compound (e.g., a boiling point lower than the operating temperature of the distillation / fractionation column 106) and / or due to chemical interactions of the compounds within the waste stream 102 (i.e., as in the case of iodine and water). However, as previously described, one or more reactive compounds 151, 152, and / or 153 may be added to the waste stream 102 such that the overhead fraction 108 includes substantially less of these impurities when the feed stream 105 containing such reactive compounds is fractionated.

[0063] For example, where reactive compound 151 is added to waste stream 102 in collection tank 104 and first reactive compound 151 is an iodine-reactive compound (e.g., sodium thiosulfate), the iodine-containing compound of waste stream 102 substantially reduces the amount of iodine present in top fraction 108 via reaction (e.g., reduction) with sodium thiosulfate. In this case, iodine is precipitated from feed stream 105 within distillation column 106, and top fraction 108 contains a relatively small amount of iodine, rather than iodine remaining in a volatile state (e.g., when distilled, as would otherwise be present in top fraction 108). For example, where 5 ppm of iodine is present in feed stream 105, first reactive compound 151 can reduce the amount of iodine in top fraction 108 to less than 2 ppm, and in some cases, less than 1 ppm, and more preferably less than 5 ppm, and in some cases, to trace amounts (e.g., substantially free of iodine). In these examples, the amount of iodine present in the overhead fraction 108 is much lower than if the first reactive compound 151 was not added to the waste stream 102 prior to fractionation / distillation.

[0064] In a second example, the second reactive compound 152 is a sulfur-reactive compound (e.g., silver nitrate) of the waste stream 102 added to the collection tank 104. In this example, the sulfur-containing compounds (e.g., mercaptans) of the waste stream 102 are reacted (e.g., reduced) via sodium thiosulfate to substantially reduce the amount of mercaptans present in the top fraction 108. In this case, mercaptans are precipitated from the feed stream 105 within the distillation column 106, and the top fraction 108 contains relatively small amounts of sulfur-containing components, rather than mercaptans remaining in a volatile state (e.g., when distilled, as would otherwise be present in the top fraction 108). For example, in the case where 200 ppm of mercaptan compounds are present in the waste stream 102, the second reactive compound 152 can reduce the amount of mercaptan compounds in the top fraction to less than 10 ppm, and in some cases, less than 5 ppm, and more preferably, less than 1 ppm, and in some cases, less than 5 ppm, and in further cases, to trace amounts (e.g., substantially free of mercaptans). In these examples, the amount of mercaptans present in the overhead fraction 108 is much lower than if the second reactive compound 152 is not added to the waste stream 102 prior to fractionation / distillation.

[0065] In a third example, the third reactive compound 153 is an acidic reactive compound (e.g., formic acid) of the waste stream 102 added to the collection tank 104. In this example, the basic nitrogen-containing compounds (e.g., alkylamines) of the waste stream 102 substantially reduce the amount of alkylamines present in the top fraction 108 via reaction (e.g., reduction) with the formic acid. In this case, the alkylamines are precipitated from the feed stream 105 within the distillation column 106, and the top fraction 108 contains a relatively small amount of the basic nitrogen-containing compounds, rather than the alkylamines remaining in a volatile state (e.g., when distilled, which would otherwise be present in the top fraction 108). For example, in the case where up to 5 wt % (e.g., 50,000 ppm) of alkylamine compounds are present in the waste stream 102, the third reactive compound 152 can reduce the amount of basic nitrogen-containing compounds in the top fraction to less than 500 ppm, and in some cases, less than 200 ppm, and more preferably less than 100 ppm. In other examples, the concentration of alkylamine compounds in waste stream 102 can be significantly lower, such as about 100 ppm. In this case, third reactive compound 152 can reduce the amount of alkylamine compounds in the top fraction to less than 10 ppm, and in some cases, less than 5 ppm, and more preferably less than 1 ppm, and in some cases, less than 5 ppm, and in further cases, to trace amounts (e.g., substantially free of alkylamines). In these examples, the amount of alkylamine compounds present in top fraction 108 is much lower than if third reactive compound 153 is not added to waste stream 102 prior to fractionation / distillation.

[0066] In each of the above cases, the bottom fraction 107 includes lower boiling point compounds (e.g., water), and any of the precipitated compounds (such as iodine, sulfur-containing compounds, and / or basic nitrogen-containing compounds). In this case, the bottom fraction 107 is recovered and can be further processed to remove some of the compounds contained in the bottom fraction 107. For example, in the case where silver nitrate is used as a reducing agent for sulfur-containing compounds and / or iodine, the silver can be recovered via further processing of the bottom fraction 107.

[0067] In an exemplary embodiment, the condensed top fraction 108 exits the fractionation zone 103 and is passed to the adsorption zone 130. In the adsorption zone 130, the condensed top fraction 108 enters a first adsorbent column 110 configured to contain a first adsorbent 112. The first top fraction 108 is purified by contacting with the first adsorbent 112 to produce a purified acetonitrile and toluene stream 114.

[0068] As previously described, the amount of iodine-containing species present in the top fraction 108 is significantly reduced by the first reactive compound 151, however, some iodine-containing components may still be present in the top fraction 108. In this case, the top fraction 108 can be contacted with a selected adsorbent 112 to reduce the amount of these organic and / or inorganic iodine-containing species, thereby producing a purified acetonitrile and toluene stream 114. Suitable adsorbents include silver (Ag) exchanged zeolites. In some embodiments, the Ag exchanged zeolite is an Ag exchanged faujasite, and specifically an faujasite having a silicon: aluminum (Si: Al) molar ratio of at least about 1.2, such as an Si: Al molar ratio of at least about 2.0. In some embodiments utilizing Ag exchange faujasite, Ag is present at a minimum of about 3 wt%, such as at least about 15 wt%. In some specific embodiments, Ag is partially ion exchanged and partially precipitated on the zeolite, wherein the fraction of Ag ion exchange depends on the Si: Al molar ratio and the wt% Ag. Typically, however, at least about 10 wt% of the Ag is ion-exchanged on the zeolite. This is not to say that the iodine reducing adsorbent is limited to faujasite. Rather, any other suitable zeolite may be used.

[0069] In embodiments utilizing one or more Ag-exchanged faujasite zeolites to reduce organic and / or inorganic iodine-containing species and sulfur-containing species present in the condensed top fraction, the adsorbent may be used by contacting the condensed top fraction 108 with the adsorbent at a weight ratio of at least about 1:100,000 adsorbent: condensed top fraction 108. In some embodiments, the weight ratio of adsorbent: condensed top fraction 108 is at least about 1:10,000, 1:1000, or 1:100. The contacting may be performed via a batch process or via a continuous process with suitable equipment, temperature, pressure, and flow rate.

[0070] In some embodiments, the methods provided herein are used to purify a waste stream 102 comprising organic and / or inorganic iodine-containing compounds, and the resulting purified acetonitrile and toluene stream 114 comprises about 25 ppm or less iodine, such as about 10 ppm or less iodine, such as about 5 ppm or less iodine, such as about 1 ppm or less iodine, such as about 0.5 ppm or less iodine, and in some cases, substantially free of iodine. In some cases, in some embodiments, the resulting purified acetonitrile and toluene stream 114 comprises about 0.1 ppm to about 25 ppm iodine, such as about 0.1 ppm to about 10 ppm iodine, such as about 0.1 ppm to about 5 ppm iodine, such as about 0.1 ppm to about 1 ppm iodine, such as about 0.1 ppm to about 0.5 ppm iodine.

[0071] In some embodiments, the methods provided herein are used to purify a waste stream 102 containing organic and / or inorganic sulfur-containing compounds as impurities. As previously described, the amount of sulfur-containing compounds present in the top fraction 108 is significantly reduced by the second reactive compound 152, however, some sulfur-containing components may still be present in the top fraction 108. In this case, the top fraction 108 can be contacted with the selected adsorbent 112 to reduce the amount of these sulfur-containing compounds, thereby producing a purified acetonitrile and toluene stream 114. In some embodiments, the resulting purified acetonitrile and toluene stream 114 contains about 10 ppm of sulfur or less, such as about 6 ppm of sulfur or less, such as about 5 ppm of sulfur or less, such as about 4 ppm of sulfur or less. In some embodiments, the resulting purified acetonitrile and toluene stream 114 contains about 0.5 ppm to about 10 ppm of sulfur, such as about 0.5 ppm to about 6 ppm of sulfur, such as about 0.5 ppm to about 5 ppm of sulfur, such as about 0.5 ppm to about 4 ppm of sulfur.

[0072] In some embodiments, the methods provided herein are used to purify a waste stream 102 containing basic nitrogen-containing compounds (such as pyridine, pyridine, lutidine, picoline, N-methylimidazole). As previously described, the amount of basic nitrogen-containing compounds present in the top fraction 108 is significantly reduced by the third reactive compound 152, however, some basic nitrogen-containing components may still be present in the top fraction 108. In this case, the purified acetonitrile and toluene stream 114 is passed to a second adsorbent tower 116, which is configured to contain an alkaline N-reducing adsorbent 118. Similarly, the alkaline N-reducing adsorbent can be the only adsorbent used; alternatively, the alkaline N-reducing adsorbent can be one of the multiple adsorbents used. In the case of using multiple adsorbents, they can also be used sequentially. In such embodiments, the alkaline N-reducing adsorbent can be used at any position in the sequence.

[0073] exist Figure 1 In a particular exemplary embodiment, purified acetonitrile and toluene stream 114 is contacted with basic N-reducing adsorbent 118 to produce purified acetonitrile and toluene stream 120 comprising a reduced amount of basic N-containing compound impurities relative to waste stream 102. Purified acetonitrile and toluene stream 120 can be collected for use or further purified as desired.

[0074] In some embodiments, the basic N adsorbent may comprise an acidic cation exchange resin. In such embodiments, the relative proportion of adsorbent used per volume of the acetonitrile and toluene stream to be purified (e.g., condensed top fraction 108 or purified acetonitrile and toluene stream 114) may vary depending on the specific adsorbent, the amount of basic N-containing impurities contained in the acetonitrile and toluene stream, and the desired level of basic N-containing impurities in the resulting purified acetonitrile and toluene stream. In some embodiments, an acidic cation exchange resin (such as Amberlyst TM -15) for reducing basic N-containing impurities in an acetonitrile and toluene stream at a ratio of at least about 1 g of adsorbent to 10 L of the acetonitrile and toluene stream, such as at least about 1 g of adsorbent to 0.1 L of the acetonitrile and toluene stream.

[0075] Thus, in some embodiments, the methods provided herein are used to purify a waste stream 102 comprising one or more basic N-containing compounds as impurities. In some embodiments, a purified acetonitrile and toluene stream is produced by removing such impurities from an acetonitrile and toluene stream, such that the resulting purified acetonitrile and toluene stream contains about 100 ppm or less of basic N-containing compounds, such as about 50 ppm or less of basic N-containing compounds, such as about 25 ppm or less of basic N-containing compounds, such as about 10 ppm or less of basic N-containing compounds. In some embodiments, a purified acetonitrile and toluene stream 120 is produced by removing these impurities from an acetonitrile and toluene stream, such that the resulting purified acetonitrile and toluene stream contains about 1 ppm to about 100 ppm of basic N-containing compounds, such as about 1 ppm to about 50 ppm of basic N-containing compounds, such as about 1 ppm to about 25 ppm of basic N-containing compounds, such as about 1 ppm to about 10 ppm of basic N-containing compounds.

[0076] In some embodiments, the acid exchange resin can also reduce the amount of cations present in the purified acetonitrile and toluene stream 114. For example, impurities such as cations Fe, Mg, Cr, Ni, Ag and I2 can be reduced by contacting with a cation exchange resin. In some embodiments, by contacting with an alkaline N reduction adsorbent comprising an acidic cation exchange resin as described above, cation reduction occurs simultaneously with alkaline N reduction. In some embodiments, the purified acetonitrile and toluene stream 120 includes less than about 5ppm of cation Fe, such as about 0.1ppm to about 5ppm, as an impurity. In some embodiments, the purified acetonitrile and toluene stream 120 includes less than about 5ppm of cation Mg, such as about 0.1ppm to about 5ppm, as an impurity. In some embodiments, the purified acetonitrile and toluene stream 120 includes less than about 5ppm of cation Cr, such as about 0.1ppm to about 5ppm as an impurity. In some embodiments, the purified acetonitrile and toluene stream 120 includes less than about 5ppm of cation Ni, such as about 0.1ppm to about 5ppm as an impurity. In some embodiments, the purified acetonitrile and toluene stream 120 contains less than about 5 ppm of cationic Ag, such as from about 0.1 ppm to about 5 ppm, as an impurity. In some embodiments, the purified acetonitrile and toluene stream 120 contains less than about 5 ppm of iodine / iodide, such as from about 0.1 ppm to about 5 ppm, as an impurity.

[0077] It may be desirable to reduce the amount of water present in the condensed purified acetonitrile and toluene stream 120. In some embodiments, including Figure 1In the examples shown, the purified acetonitrile and toluene stream 120 is passed to a third adsorbent column 122. In these examples, the third adsorbent column 122 is configured to contain a water reducing adsorbent (i.e., a desiccant) 124. The purified acetonitrile and toluene stream 120 is contacted with the water reducing adsorbent 124 to produce a purified acetonitrile and toluene mixture 126 that exits the adsorption zone 130.

[0078] In some embodiments, Linde A-type (LTA) molecular sieves exchanged with potassium (K) in combination with an inorganic binder can be used as dewatering adsorbent 124. It has been surprisingly found that if the porous desiccant has been treated to partially close their pore structure, the porous desiccant exhibits improved performance (i.e., higher water adsorption capacity) for reducing water in acetonitrile waste streams. Therefore, in some embodiments, one or more porous desiccants (including one or more K-exchanged LTA-type molecular sieves combined with an inorganic binder) can be treated by any suitable process known in the art to partially close the pores of the desiccant before use. However, care must be taken not to close the pores too much and thus limit the water adsorption capacity. The degree of pore closure can be measured by determining the smallest molecule (also referred to as a plug gauge molecule) that will not adsorb more than 1% by weight of the molecule when exposed to an atmospheric partial pressure. In some embodiments, the desiccant is an LTA-type adsorbent that has been treated with a stream to partially close the pore structure of the desiccant to the point where the desiccant has a limited ability to adsorb ethylene, difluoromethane, or both.

[0079] In embodiments where one or more LTA-type adsorbents are utilized to reduce water in the purified acetonitrile and toluene stream 120 from the waste stream 102, the adsorbent can be used in a weight ratio of at least 5 mg to 10 mg of desiccant per gram of acetonitrile to be purified. In some embodiments, one or more LTA-type adsorbents having a minimum water adsorption capacity of 10 wt % are used. In embodiments where one or more LTA-type adsorbents are utilized to reduce water in the purified acetonitrile and toluene stream 120, the adsorbent can be used in a weight ratio of at least 5 mg to 10 mg of desiccant per gram of acetonitrile to be purified. In some embodiments, one or more LTA-type adsorbents having a minimum water adsorption capacity of 10 wt % are used. Contacting can be performed via a batch process or a continuous process with suitable equipment, temperature, pressure, and flow rate.

[0080] In some embodiments, reducing the amount of water present in the condensed purified acetonitrile and toluene stream 120 is performed via a liquid phase process. In these embodiments, when the purified acetonitrile and toluene stream 120 contacts the water reducing adsorbent 124, the purified acetonitrile and toluene stream is in a liquid phase.

[0081] Alternatively or in addition, reducing the amount of water present in the purified acetonitrile can be carried out by a gas phase process, such as gas phase pressure swing adsorption (PSA). In an exemplary embodiment, the purified acetonitrile and toluene streams leaving the fractionation tower can be processed to reduce or eliminate the condensation of the top fraction of the tower. On the contrary, the purified acetonitrile and toluene streams leaving the fractionation tower are further heated, for example, by being superheated by about 25°C above the fractionation temperature, and the heated steam is fed into a tower containing a water-reducing adsorbent. In some embodiments, the water-reducing adsorbent is a Linde A type (LTA)-type 20 molecular sieve exchanged with potassium (K) combined with an inorganic binder, which, as described above, may or may not have partially enclosed pores. After contacting with the water-reducing adsorbent, the steam is directed to a heat exchanger, in which the steam is condensed into liquid-phase purified acetonitrile and toluene. The liquid-phase purified acetonitrile and toluene mixture can be further purified as needed, including contacting with other adsorbent materials described herein. Those skilled in the art will appreciate that multiple columns containing water reducing adsorbents may be used in parallel in the processes described herein, such that after the adsorbent in the first column is saturated, the acetonitrile and toluene mixture vapor to be dried may be directed to the second column while the adsorbent in the first column is regenerated. In some embodiments, the regeneration conditions include stripping water from the adsorbent by reducing the pressure and condensing the released material as a liquid waste stream.

[0082] In some embodiments, at least a portion of the liquid waste stream can be redirected back to the fractionation column for further processing. In some embodiments, the average water delta loading (i.e., the change in the average water content of the adsorbent from the beginning to the end of the adsorption step) is about 1 kg water / 100 kg adsorbent to about 3 kg water / 100 kg adsorbent. In these embodiments, the adsorption conditions (such as pressure, feed rate, and flow rate) can be such that the 45 adsorption step can be performed for about 5 minutes to about 10 minutes.

[0083] Therefore, in some embodiments, the methods provided herein are used to purify a waste stream 102 comprising water as an impurity. In some related embodiments, the waste stream 102 is fractionated and the top fraction is contacted with a desiccant having a partially closed pore structure. In some embodiments, the purified acetonitrile and toluene mixture 126 that has been purified by contact with a desiccant contains about 2000 ppm of water or less, such as about 1000 ppm of water or less, such as about 500 ppm of water or less, such as about 150 ppm of water or less, 100 ppm of water or less, such as about 50 ppm of water or less, such as about 25 ppm of water or less.

[0084] Although the various embodiments described above describe a waste stream that is passed from a fractionation tower and then sequentially passed through an iodine-reducing adsorbent, through an adsorbent that reduces alkaline N-containing compounds, and through a water-reducing adsorbent, it should be understood that the scope of this document is not limited to this. On the contrary, it should be understood that, in addition to the fractionation tower, only one or two of the adsorbents may be used, and / or the adsorbents may be used in a different order, but are not limited to this. For example, after fractionation and condensation, the condensed top fraction 108 may be contacted with an alkaline N-containing compound reducing adsorbent and the resulting acetonitrile and toluene stream may be contacted with a water-reducing adsorbent, or the condensed top fraction 108 may be contacted with a water-reducing adsorbent and the resulting stream may be contacted with an iodine-reducing adsorbent.

[0085] In some embodiments, the methods provided herein are used to purify the waste stream 102 from oligonucleotide synthesis to produce a purified acetonitrile and toluene mixture 126 suitable for reuse in various industrial or manufacturing processes. In some embodiments, the purified acetonitrile and toluene mixture 126 is suitable for reuse as an inter-step washing solution in oligonucleotide synthesis with an inter-step acetonitrile washing solution. In some embodiments, the purity of the purified acetonitrile and toluene mixture 126 is greater than about 85%, such as greater than or equal to about 95%, as determined by gas chromatography.

[0086] As previously described, it has been found that in the context of an oligonucleotide synthesis process, the use of a blended solution of toluene and acetonitrile as a wash solvent has been found to be not only acceptable (e.g., producing oligonucleotides of similar purity as compared to a pure acetonitrile wash solvent), but in some cases, has surprisingly been found to increase the purity of the oligonucleotides produced as compared to a pure acetonitrile wash solvent.

[0087] For example, in a first set of cases, various wash solvents containing different acetonitrile and toluene purities were tested, and the resulting oligonucleotide purity was obtained based on a first type of carrier resin and a first type of oligonucleotide test sequence (e.g., test-20; 20-mer, etc.), and it was surprisingly found that a blended solution of toluene and acetonitrile as a wash solvent increased the purity of the first oligonucleotide purity compared to a pure acetonitrile wash solvent.

[0088] For example, when pure acetonitrile is used as a washing solvent in the oligonucleotide synthesis process using a first type of carrier resin and a first oligonucleotide test sequence (Test-20), the purity of the resulting synthesized oligonucleotide determined by liquid chromatography can be in the range of 70% to 73%, such as in the range of 70.2% to 72.2%.

[0089] However, in the case where the substantially pure mixture of 95 % by weight acetonitrile and 5 % by weight toluene is used as a washing solvent in the oligonucleotide synthesis process with the first type of carrier resin and test-20 oligonucleotide sequences, it has been surprisingly found that the oligonucleotide synthesized by the gained is slightly purer than the synthesized oligonucleotide produced by using pure acetonitrile as a washing solvent. For example, the oligonucleotide purity obtained from the oligonucleotide synthesis process using the toluene blend of 95 % by weight acetonitrile / 5 % by weight can have a purity within the range of 70% to 74% purity, and more specifically, a purity within the range of 70.7% to 73.8% purity. Therefore, compared to pure acetonitrile, in the oligonucleotide synthesis process, using the blend of 95 % by weight acetonitrile / 5 % by weight toluene is favourable as a washing solvent.

[0090] In another example, the substantially pure mixture of the acetonitrile of 85 % by weight and the toluene of 15 % by weight is used as the washing solvent in the oligonucleotide synthesis process, using the same first carrier resin and test-20 oligonucleotide sequences.In this case, surprisingly found that the oligonucleotide of gained synthesis is slightly purer than the synthetic oligonucleotide that uses pure acetonitrile to produce as the washing solvent.For example, the oligonucleotide purity obtained from the oligonucleotide synthesis process using the toluene blend of acetonitrile of 85 % by weight / 15 % by weight can have the purity within 72% to 76% purity range, and more specifically, the purity within 72.5% to 76.4% purity range.Therefore, compared to pure acetonitrile, in the oligonucleotide synthesis process, using the blend of the toluene of acetonitrile of 85 % by weight / 15 % by weight is favourable as the washing solvent.

[0091] In another example again, in the case of the substantially pure mixture of the azeotropic composition of the acetonitrile of 76 % by weight and the toluene of 24 % by weight as a washing solvent in the oligonucleotide synthesis process with the first solid carrier resin and test-20 oligonucleotide sequences, it has been surprisingly found that the oligonucleotide of the synthesis of gained is slightly purer than the synthetic oligonucleotide produced using pure acetonitrile as a washing solvent.For example, the oligonucleotide purity obtained from the oligonucleotide synthesis process using the toluene blend of the acetonitrile of 76 % by weight / 24 % by weight can have a purity within the range of 71% to 73% purity, and more specifically, a purity within the range of 71.3% to 72.2% purity.Therefore, compared to pure acetonitrile, in the oligonucleotide synthesis process, using the blend of the toluene of the acetonitrile of 76 % by weight / 24 % by weight is favourable as a washing solvent.

[0092] In a second set of cases, various wash solvents containing different acetonitrile and toluene purities were tested, and the resulting oligonucleotide purity was obtained based on a second type of carrier resin and a second type of oligonucleotide test sequence (e.g., test-18;18-mer), and it was surprisingly found that a blended solution of toluene and acetonitrile as a wash solvent also increased the purity of the second oligonucleotide purity compared to a pure acetonitrile wash solvent.

[0093] For example, when a second carrier resin and a second oligonucleotide test sequence (Test-18) are used, and when pure acetonitrile is used as a washing solvent in the oligonucleotide synthesis process, the purity of the resulting synthesized oligonucleotide (determined by liquid chromatography) can be in the range of 91% to 93%, such as in the range of 91.2% to 93.1%.

[0094] However, using the same second carrier resin (second resin) and test oligonucleotide test sequence (test 18), wherein the substantially pure mixture of the acetonitrile of 90 % by weight and the toluene of 10 % by weight is used as the washing solvent in the oligonucleotide synthesis process, surprisingly found that the oligonucleotide of gained synthesis is slightly purer than the synthetic oligonucleotide using pure acetonitrile to produce as the washing solvent.For example, the oligonucleotide purity obtained from this oligonucleotide synthesis process using the toluene blend of 90 % by weight of acetonitrile / 10 % by weight can have the purity within 92% to 100% purity range, and more specifically, the purity within 92.6% to 99.8% purity range.Therefore, compared to pure acetonitrile, in the oligonucleotide synthesis process, using the blend of the toluene of 90 % by weight of acetonitrile / 10 % by weight is favourable as the washing solvent.

[0095] In the second example, using this same second carrier resin and the second test sequence (test 18), the substantially pure mixture of the acetonitrile of 85 % by weight and the toluene of 15 % by weight is used as the washing solvent in the oligonucleotide synthesis process.In this case, surprisingly found that the oligonucleotide of gained synthesis is slightly purer than the synthetic oligonucleotide that uses pure acetonitrile to produce as washing solvent.For example, the oligonucleotide purity obtained from the oligonucleotide synthesis process using the toluene blend of acetonitrile / 15 % by weight of 85 % by weight can have the purity in 92% to 96% purity range, and more specifically, the purity in 92.6% to 95.7% purity range.Therefore, compared to pure acetonitrile, in oligonucleotide synthesis process, using the blend of the toluene of acetonitrile / 15 % by weight of 85 % by weight is favourable as washing solvent.

[0096] In another example, using this same second carrier resin and the second oligonucleotide test sequence (test 18), the substantially pure mixture of the acetonitrile of 80 % by weight and the toluene of 20 % by weight is used as the washing solvent in the oligonucleotide synthesis process.In this case, surprisingly found that the oligonucleotide of gained synthesis is slightly purer than the synthetic oligonucleotide using pure acetonitrile to produce as the washing solvent.For example, the oligonucleotide purity obtained from the oligonucleotide synthesis process using the toluene blend of acetonitrile / 20 % by weight of 80 % by weight can have the purity within 93% to 97% purity range, and more specifically, the purity within 93.9% to 96.9% purity range.Therefore, compared to pure acetonitrile, in oligonucleotide synthesis process, using the blend of the toluene of acetonitrile / 20 % by weight of 80 % by weight is favourable as washing solvent.

[0097] In another example again, in the case of being used as washing solvent in the oligonucleotide synthesis process of the acetonitrile of 76 % by weight and the toluene of 24 % by weight, it has been surprisingly found that the oligonucleotide of gained synthesis has the higher purity of the synthetic oligonucleotide than using pure acetonitrile as washing solvent to produce.For example, the purity of the oligonucleotide obtained from the oligonucleotide synthesis process with the second resin and T18 sequence of the toluene blend of acetonitrile / 24 % by weight using 76 % by weight can be in the scope of 95% to 97%, and more specifically, purity is in the scope of 95.3% to 96.8%.Therefore, compared to pure acetonitrile, in oligonucleotide synthesis process, using the blend of the toluene of acetonitrile / 24 % by weight of 76 % by weight is favourable as washing solvent.

[0098] Therefore, and as demonstrated in the foregoing examples, it has been found that a blended wash solvent composition of 5 wt % to 24 wt % toluene and corresponding 95 wt % to 76 wt % acetonitrile results in at least the same level of purity of the resulting oligonucleotides produced by the oligonucleotide synthesis process, if not such oligonucleotides of higher purity than the pure acetonitrile wash solvent. In other words, the foregoing examples show that the use of a blended wash solvent comprising as little as 5 wt % toluene and as much as 24 wt % toluene and as little as 76 wt % acetonitrile and as much as 95 wt % acetonitrile (or any range defined by any two of the foregoing values) in an oligonucleotide synthesis process results in an oligonucleotide purity at least as pure as, if not purer than, the pure acetonitrile wash solvent.

[0099] As previously mentioned, the acetonitrile and toluene mixture 126 of the purification produced can be purified into substantially pure (for example, 80% or higher, and more preferably, 95% or higher purity) mixture of acetonitrile and toluene, and the substantially pure mixture of this acetonitrile and toluene can be the azeotropic composition of acetonitrile and toluene or be in the acetonitrile and toluene ratio that comprises the more acetonitrile than azeotrope.For example, the acetonitrile and toluene mixture 126 of the purification produced can be purified into the substantially pure azeotropic composition of the acetonitrile of about 76 weight % and the toluene of 24 weight %.In this case, although it has been found that in oligonucleotide synthesis technique, this blend composition can be reused as washing solvent and can produce the oligonucleotide purity that is at least similar to pure acetonitrile (for example, reuse azeotropic composition is at least acceptable, if not preferred compared with pure acetonitrile), but can advantageously increase the relative weight percentage of acetonitrile in mixture so that the more favourable composition with washing solvent is target, as mentioned above. For example, the weight percent of acetonitrile from the azeotropic composition can be increased from 76 weight percent to 80 weight percent, and more preferably 85 weight percent, and possibly 90 weight percent, and in some cases to 95 weight percent, in order to meet the more favorable acetonitrile and toluene blend as previously described.

[0100] The total weight percentage of increasing acetonitrile can be achieved by adding acetonitrile to the purified acetonitrile and toluene mixture 126 produced by using the recycled purified acetonitrile and toluene mixture 126 as a washing solvent in the oligonucleotide synthesis process at a certain moment in the process. For example, before using the purified acetonitrile and toluene mixture 126 as a washing solvent mixture in the oligonucleotide synthesis process, the supplemented acetonitrile 154 can be added to the purified acetonitrile and toluene mixture 126 (for example, inline, or by any other suitable mixing device). In this case, the amount of the supplementary acetonitrile 154 added to the purified acetonitrile and toluene mixture 126 can be based on the amount of the supplementary acetonitrile 154 required for the target composition of the blend of acetonitrile and toluene. For example, the amount of the supplementary acetonitrile 154 added to the purified acetonitrile and toluene mixture 126 can be the amount of acetonitrile increased to 80% by weight from the weight percentage (for example, 76% by weight) in the azeotropic composition, and more preferably 85% by weight, and may be 90% by weight, and in some cases increased to 95% by weight of the acetonitrile required. Alternatively, in the case where the relative weight percentage of acetonitrile and toluene is greater than the azeotropic composition, the amount of supplementary acetonitrile 154 added to the purified acetonitrile and toluene mixture 126 can be the amount required for the acetonitrile to increase the relative weight percentage of acetonitrile to 80 weight %, more preferably 85 weight %, and possibly 90 weight %, and in some cases to 95 weight % of acetonitrile. In addition, although supplementary acetonitrile 154 is exemplified as being added to the purified acetonitrile and toluene mixture 126, supplementary acetonitrile 154 can be added to any one or combination of the collection tank 104, the feed stream 105, the tower top fraction 108, the purified acetonitrile and toluene stream 114 and / or the purified acetonitrile and toluene stream 120, so that the composition of the acetonitrile and toluene mixture 126 includes any of the above weight percentages of acetonitrile. In any of these cases, compared to using pure acetonitrile as a wash solvent, the total purity of the oligonucleotide synthesis process is increased by using the resulting purified acetonitrile and toluene mixture 126 recycled to the oligonucleotide synthesis process as a wash solvent.

[0101] Although the aforementioned discussion relates to the recycling of the waste stream of purification, possible acetonitrile supplementation and recovery from oligonucleotide synthesis process to be used as washing solvent, it should be understood that this type of discussion does not mean that the present invention is limited only to the situation of waste stream recycling.As previously mentioned, it has been found that using acetonitrile and toluene mixture as washing solvent is advantageous compared to independent pure acetonitrile.Therefore, any treatment step relevant with the purification of waste stream 102 and supplementation may not be necessary, but the oligonucleotide synthesis process utilizing the fresh (for example, non-circulation) stream of any acetonitrile and toluene composition as above may be equally advantageous (if not more advantageous) for being used as the washing solvent in oligonucleotide synthesis process, and therefore also is contained in the present disclosure.

[0102] Materials and methods

[0103] Embodiment 1 to embodiment 8:

[0104] With respect to Examples 1 to 8 described below, an azeotropic or close boiling mixture of acetonitrile and toluene wastes containing iodine, mercaptans, alkylamines and other impurities is treated by adding a reducing agent such as sodium thiosulfate, silver nitrate and / or formic acid and / or formic acid to the feed stream. In the case of sodium thiosulfate, the reducing agent converts all dissolved organic and inorganic iodine compounds to non-volatile iodides and can be removed via a side draw without the need for any additional equipment.

[0105] Unless otherwise stated, all concentrations are by mass, ie percentages are weight percentages and ppm are weight ppm. In all examples, the feed mass in the distillation column is 1 kg of a binary mixture consisting of 76% acetonitrile and 24% toluene.

[0106] The fractionation was carried out in a 400 mm packed glass tower equipped with a liquid distributor and a cooling outlet at the top. The tower itself consisted of an evacuated (10 mbar to 6 mbar) silver-coated insulating jacket, an observation bar and an outer bellows (one bellows packing per 500 mm length). The packing consisted of corrosion-resistant Raschel rings made of borosilicate glass. The 40 cm packed tower was operated at a reflux ratio of RR = 0.33 and a gradually decreasing pressure. The experiment was carried out so that 80% of the initial feed was obtained as a tower top product. The distillate was divided into three fractions of 200 ml each.

[0107] As used herein, "man-made waste" refers to the composition shown in Table 1 below.

[0108] Table 1

[0109]

[0110]

[0111] Man-made waste may also include trace metals in an amount less than 0.2 ppm. Trace metals may include one or more of aluminum, barium, bismuth, cadmium, calcium, chromium, cobalt, copper, iron, lead, lithium, magnesium, manganese, molybdenum, nickel, potassium, silver, sodium, strontium, tin, and zinc.

[0112] Example 9: Test-20 Oligonucleotides (DNA and RNA)

[0113] Oligonucleotide (DNA and RNA) synthesis is usually carried out via a four-step cycle (deblocking, activation / coupling, end-capping and oxidation / sulfurization), which is repeated for each nucleotide added until the desired sequence is obtained. Between each step, the oligonucleotide bound to the carrier is washed with an acetonitrile-based washing solvent to reduce residual reagents from the previous step. The washing solvent is usually pure acetonitrile.

[0114] It is hypothesized that a blend of acetonitrile and toluene can be used as a wash solvent rather than pure acetonitrile alone. To test such a hypothesis, various compositions of substantially pure mixtures of acetonitrile and toluene were used as wash solvents in multiple oligonucleotide synthesis reactions, which produced various degrees of purity of the resulting oligonucleotides.

[0115] In this case, the following oligonucleotide synthesis test conditions were observed for Test 20 (eg, "20-mer"). Oligonucleotide:

[0116]

[0117]

[0118] Oligonucleotide yields were determined by HPLC using UV detection at 260 nm. In addition, the identity of the major peak was confirmed by LCMS.

[0119] Example 10: Test-18 Oligonucleotides (DNA and RNA)

[0120] Similar to Example 9, oligonucleotide (DNA and RNA) synthesis is usually carried out via four-step circulation (deblocking, activation / coupling, end-capping and oxidation / sulfurization), and each nucleotide added is repeated until the desired sequence is obtained. Between each step, the oligonucleotide attached to the carrier is washed with a washing solvent based on acetonitrile to reduce the residual reagent from the previous step. The washing solvent is normally pure acetonitrile.

[0121] As with Example 9, it was hypothesized that a blend of acetonitrile and toluene could be used as a wash solvent rather than pure acetonitrile alone. To test such a hypothesis, various compositions of substantially pure mixtures of acetonitrile and toluene were used as wash solvents in multiple oligonucleotide synthesis reactions, which produced various degrees of purity of the resulting oligonucleotides.

[0122] In this case, the following oligonucleotide synthesis test conditions were observed for Test 18 (eg, "18-mer"). Oligonucleotide:

[0123]

[0124] Oligonucleotide yields were determined by HPLC using UV detection at 260 nm. In addition, the identity of the major peak was confirmed by LCMS.

[0125] Example

[0126] Example 1: Fractionation of Man-Made Waste Streams

[0127] In this embodiment, 1000ml is also contained acetonitrile, toluene, tetrahydrofuran (THF) and the man-made waste of organic reagent from oligonucleotide synthesis as described in table 01 is introduced in the round-bottomed flask of fractionating tower.Fractional distillation is carried out under the situation of any pre-treatment additive or entrainer.Tower top temperature and tower bottom temperature are set at 76 ℃ and 85 ℃ respectively.Distillate is condensed and collected into two fractions in water cooler at tower top again.The first fraction (fraction 1) has minimum volume.It contains 1% to 2% water and the component shown in the following table 2.Main fraction (fraction 2) is also collected and analyzed.

[0128] The distillate of the artificial compounded rinse solution can be purified by simple fractional distillation; however, various components of the chemicals used for oligonucleotide synthesis may be left over. Thus, in addition to water, significant proportions of the used alkylamines, acetic acid, dichloroacetic acid, alkylthiols and iodine were found in both distillates. The results of the analysis of the artificial waste distillate and their specification values ​​("Specifications") are shown in Table 2.

[0129] Table 2

[0130] Run 1 Specification Man-made waste Fraction 1 Fraction 2 Acetonitrile (100%) Minimum 94% 82.0％ 75.4％ 95.9％ Toluene Maximum 5% 5.0％ 9.2％ 3.3％ THF Maximum 5% 5.0％ 15.3％ 0.03％ Pyridine <100ppm 20.000ppm 80ppm 6500ppm 2,6-Dimethylpyridine <100ppm 10.000ppm 60ppm 30ppm Pyridine <100ppm 10.000ppm 100ppm 800ppm N-Methylimidazole <100ppm 10.000ppm <50ppm <50ppm water <1ppm 10.000 8260ppm 930ppm Phenylacetyl disulfide <5ppm 200 <0.5ppm <0.5ppm Dichloroacetic acid <1ppm 100 <0.5ppm <0.5ppm 5-Ethylthio-1H-tetrazolyl <1ppm 100 <0.5ppm <0.5ppm iodine <1ppm 5 <0.5ppm <0.5ppm

[0131] Example 2: Fractional distillation of acetonitrile and toluene with addition of iodine

[0132] In this example, 200 mg of solid iodine was added to an azeotrope (designated as "azeotrope" in the table below) of 361 g of acetonitrile and 114 g of toluene. The mixture was stirred until the solid iodine was completely dissolved and then transferred to a round-bottomed flask of a fractionating column. The top and bottom temperatures were set at 76° C. and 80° C., respectively. The distillate was condensed in a cooler and collected in equal fractions at the top of the column. It was noted that the condensate (fractions 1-3) still had color and the smell of iodine was felt.

[0133] These fractions were analyzed and the results are shown in Table 3 below along with the specification values ​​("Specifications").

[0134] Table 3

[0135] Run 2 Specification Azeotrope Fraction 1 Fraction 2 Fraction 3 Acetonitrile (100%) Minimum 94% 76.0％ 75.40％ 95.90％ 97.3％ Toluene 5% maximum 24.0％ 9.20％ 3.30％ 3.30％ iodine <1ppm 205ppm 2ppm 4ppm 8ppm

[0136] Example 3: Precipitation of iodine from acetonitrile and toluene using sodium thiosulfate

[0137] In this embodiment, 200 mg of solid iodine and equimolar amount (259 mg) of solid sodium thiosulfate are added to the azeotrope of 361 g of acetonitrile and 114 g of toluene. The solution is stirred at 500 rpm with a magnetic stirrer until the solid is completely dissolved. Then, distillation is performed, and the tower top temperature and the tower bottom temperature are set to 81 ° C and 85 ° C respectively. The distillate is condensed at the tower top in a cooler and collected into two equal fractions.

[0138] In this advantageous version, the condensed distillate is colorless. The iodine content is less than 0.1 ppm. The analytical results of the fractions are shown in Table 4 below together with the specification values ​​("Specifications").

[0139] Table 4

[0140] Run 3 Specification Azeotrope Fraction 1 Fraction 2 Acetonitrile (100%) Minimum 94% 76.0％ 75.40％ 95.90％ Toluene 5% maximum 24.0％ 9.20％ 3.30％ iodine <1ppm 205ppm <0.1ppm <0.1ppm

[0141] Example 4: Precipitation of iodine from a man-made waste stream using sodium thiosulfate

[0142] In this example, 500 ml of artificial waste is doped with 125 mg of iodine and 160 mg of sodium thiosulfate. A mixture further containing 65% of acetonitrile and 25% of toluene is introduced into a round-bottomed flask of a fractionation column. The top temperature and the bottom temperature are set at 76° C. and 80° C., respectively. The distillate is condensed again at the top of the column in a cooler and collected into two fractions. Two main fractions are analyzed.

[0143] In contrast to Example 3, 1.2 ppm of iodide was found when analyzing fraction 2. This indicates that the higher concentration of iodine in the oligonucleotide waste requires excess reducing agent to prevent iodine carryover. The results of the analysis are shown in Table 5 below along with the specification values ​​("Specifications").

[0144] Table 5

[0145]

[0146]

[0147] Example 5: Precipitation of Thiols from Acetonitrile and Toluene Using Silver Nitrate

[0148] In this example, 100 mg of phenylacetyl disulfide (PAD) and 50 mg of 5-ethylthio-1H-tetrazole (ETT) were added to an azeotrope of 380 g of acetonitrile and 120 g of toluene (designated as "azeotrope" in the table below). Finally, 51 mg of silver nitrate was added to the mixture. Then, distillation was performed, with the top and bottom temperatures set to 76° C. and 81° C., respectively. The distillate was condensed at the top of the column in a cooler and collected in two equal fractions.

[0149] In this advantageous version, the condensed distillate is colorless and has no strong odor of sulfur compounds. The alkyl mercaptan content is reduced to below the detection limit of HPLC. The analytical results are shown in Table 6 below together with the specification values ​​("Specifications").

[0150] Table 6

[0151] Run 5 Analytical methods Specification Azeotrope Fraction 1 Fraction 2 Fraction 3 Acetonitrile GC 76.0％ 87.2 77.6 74.3 Toluene GC 24.0％ 21.7 22.4 25.6 Phenylacetyl disulfide HPLC <5ppm 0.020％ <0.5 <0.5 <0.5 5-Ethylthio-1H-tetrazolyl HPLC <1ppm 0.010％ <0.5 <0.5 <0.5

[0152] Example 6: Precipitation of alkylamines from acetonitrile and toluene using formic acid

[0153] In this example, the effectiveness of formic acid as a reducing agent and Lewis acid to precipitate alkylamines by forming Lewis adducts was studied. 10 g of pyridine was added to an azeotrope of 361 g of acetonitrile and 114 g of toluene, as well as 5 g each of picoline, 2,6-lutidine, and N-methylimidazole (designated as "azeotrope" in the table below). Finally, 13.24 g of formic acid was added to the mixture. Then, distillation was performed, with the top and bottom temperatures set to 81°C and 85°C, respectively. The distillate was condensed at the top of the tower in a cooler and collected into three equal fractions.

[0154] In this favorable form, the condensed distillate is colorless. The carryover of the alkylamines has been significantly reduced, indicating that the formic acid forms non-volatile salts with the alkylamine bases, thereby preventing them from evaporating during the distillation. The analytical results are shown in Table 7 below together with the specification values ​​("Specifications").

[0155] Table 7

[0156] Run 6 Analytical methods Specification Azeotrope Fraction 1 Fraction 2 Fraction 3 reduce% Acetonitrile (100%) GC Minimum 94% 76.0％ 78.4％ 78.1％ 76.5％ Toluene GC 5% maximum 24.0％ 21.3％ 21.8％ 23.3％ Pyridine GC <100ppm 2.0％ 300ppm 500pm 1400ppm 93.00％ 2,6-Dimethylpyridine GC <100ppm 1.0％ <100ppm <100 <101ppm 100.00％ Pyridine GC <100ppm 1.0％ <100ppm <100 190ppm 98.10％ N-Methylimidazole GC <100ppm 1.0％ <100ppm <100 <101ppm >99％

[0157] Example 7: Precipitation of iodine from a man-made waste stream using excess sodium thiosulfate

[0158] In this embodiment, 1000ml of artificial waste further containing 5ppm iodine and equimolar amount of sodium thiosulfate is introduced into the round-bottom flask of the fractionation tower. 12mg sodium thiosulfate is added to reduce the organic iodine compound in the waste solution. The tower top temperature and the tower bottom temperature are set at 76°C and 81°C, respectively. The distillate is condensed at the tower top in the cooler again and collected into two fractions. The first fraction has the smallest volume. It contains 1% to 2% of water and the components shown in Table 8. The main fraction is also collected and analyzed for iodine content. Within the detection limit of the method, iodine is not detected in the distillate. The analysis results are shown in Table 8 below together with the specification value ("Specification").

[0159] Table 8

[0160]

[0161]

[0162] Example 8: Precipitation of iodine and alkylamines from man-made waste streams

[0163] In this example, 500 ml of an artificial waste stream, 10 mg of sodium thiosulfate and excess formic acid were mixed. The mixture, which further contained 65% of acetonitrile and 25% of toluene, was introduced into a round-bottomed flask of a fractionation column. The top and bottom temperatures were set at 76° C. and 81° C., respectively. The distillate was condensed again at the top of the column in a cooler and collected into two fractions.

[0164] The concentrations of all tested alkylamines were below the specification limit and the amount of iodine in the distillate was below 0.5 ppm (detection limit of the HPLC method).The analytical results are shown in Table 9 below together with the specification values ​​("Specifications").

[0165] Table 9

[0166] Run 8 Specification Man-made waste Fraction 1 Fraction 2 Acetonitrile Minimum 94% 82.0％ 62.9％ 83％ Toluene 5% maximum 5.0％ 9％ 11.6％ THF 5% maximum 5.0％ 28.1％ 5.4％ Pyridine <100ppm 20.000ppm <50ppm <50ppm 2,6-Dimethylpyridine <100ppm 10.000ppm <50ppm <50ppm Pyridine <100ppm 10.000ppm <50ppm <50ppm N-Methylimidazole <100ppm 10.000ppm 100ppm <50ppm Phenylacetyl disulfide <5ppm 200ppm <0.5ppm <0.5ppm Dichloroacetic acid <1ppm 100ppm <0.5ppm <0.5ppm 5-Ethylthio-1H-tetrazolyl <1ppm 100ppm <0.5ppm <0.5ppm iodine <1ppm 5ppm <0.5ppm <0.5ppm

[0167] Example 9: Test-20 oligonucleotide purity obtained by using various wash solvent compositions:

[0168] In this embodiment, under the experimental conditions provided previously, the same 5'ATA CCG ATT AAG CGA AGT TT 3'20-mer oligonucleotide test-20 sequence is synthesized in four tests using four different compositions of acetonitrile-based washing solvents. The first test uses a pure (e.g., 100 wt %) acetonitrile washing solvent, the second test uses a washing solvent comprising 95 wt % acetonitrile and 5 wt % toluene, the third test uses a washing solvent comprising 85 wt % acetonitrile and 15 wt % toluene, and the fourth test uses a washing solvent comprising 76 wt % acetonitrile and 24 wt % toluene (e.g., representing an azeotropic composition of acetonitrile and toluene). The purity of the resulting 20-mer oligonucleotide is reported based on HPLC yield, and the results are shown in Table 10 below:

[0169] Table 10

[0170] Washing solvent weight% acetonitrile Washing solvent weight% toluene Average HPLC yield Standard deviation of HPLC yield 100 0 70.97 0.88 95 5 72.15 1.26 85 15 74.75 1.65 76 24 71.75 0.36

[0171] It has been surprisingly found that when using purity lower than pure acetonitrile washing solvent, the productive rate of the test-20 oligonucleotide product formed during the solid phase chemical synthesis of oligonucleotide increases slightly. Specifically, it is observed that the blended composition using containing 85% acetonitrile and 15% toluene (w / w) washing solvent causes the highest oligonucleotide productive rate. However, in each case in the above-mentioned situation, the blended composition of acetonitrile and toluene washing solvent shows at least similar (if not higher) test-20 oligonucleotide productive rate compared with pure acetonitrile washing solvent. Therefore, this experiment confirms that using blended washing solvent rather than pure acetonitrile in oligonucleotide synthesis process is not only possible (for example, oligonucleotide synthesis does not necessarily need pure acetonitrile washing solvent), but may be advantageous.

[0172] Example 10: Test-18 oligonucleotide purity obtained by using various wash solvent compositions:

[0173] In another embodiment, under the experimental conditions provided previously, the sequence of test-18 5'TTT TTT TTT TTT TTT TTT 3'18-mer oligonucleotide is synthesized in five tests using five different compositions of acetonitrile-based washing solvents. The first test uses a pure (e.g., 100 wt %) acetonitrile washing solvent, the second test uses a washing solvent comprising 90 wt % acetonitrile and 10 wt % toluene, the third test uses a washing solvent comprising 85 wt % acetonitrile and 15 wt % toluene, the fourth test uses a washing solvent comprising 80 wt % acetonitrile and 20 wt % toluene, and the fifth test uses a washing solvent comprising 76 wt % acetonitrile and 24 wt % toluene (e.g., representing an azeotropic composition of acetonitrile and toluene). The purity of the resulting 18-mer oligonucleotide is reported based on HPLC yield, and the results are shown in Table 11 below:

[0174] Table 11

[0175]

[0176]

[0177] Surprisingly found that when using purity lower than pure acetonitrile washing solvent, the productive rate of the test-18 oligonucleotide product formed during the solid phase chemical synthesis of oligonucleotide increases slightly.Specifically, observe and use the blended composition containing 80% acetonitrile and 20% toluene (w / w) washing solvent to cause the highest oligonucleotide productive rate.But, in each case in the above situation, the blended composition of acetonitrile and toluene washing solvent shows at least similar (if not higher) test-18 oligonucleotide productive rate compared with pure acetonitrile washing solvent.Therefore, this experiment confirms that using blended washing solvent rather than pure acetonitrile in oligonucleotide synthesis process is not only possible (for example, oligonucleotide synthesis does not necessarily need pure acetonitrile washing solvent), and may be favourable.

[0178] aspect:

[0179] Aspect 1 is a method for processing a waste stream, the method comprising: receiving the waste stream comprising acetonitrile, toluene and one or more iodine-containing compounds; adding an iodine-reactive compound to the waste stream; and fractionating the waste stream to produce a top fraction and a bottom fraction, the top fraction comprising the acetonitrile and the toluene of the waste stream, and the bottom fraction comprising the one or more iodine-containing compounds of the waste stream.

[0180] Aspect 2 is a method according to aspect 1, wherein the iodine-reactive compound comprises sodium thiosulfate.

[0181] Aspect 3 is a method according to any one of aspects 1 or 2, wherein the iodine-reactive compound comprises sodium thiosulfate and silver nitrate.

[0182] Aspect 4 is a method according to any one of aspects 1 to 3, wherein the top fraction further comprises iodine at a concentration of less than 25 ppm.

[0183] Aspect 5 is a method according to any one of aspects 1 to 4, wherein the top fraction further comprises iodine at a concentration of less than 1 ppm.

[0184] Aspect 6 is a method according to any one of Aspects 1 to 5, wherein during the fractionation of the waste stream, the iodine-reactive compound reacts with iodine in the one or more iodine-containing compounds, and the iodine in the one or more iodine-containing compounds is precipitated from the waste stream into the bottom fraction.

[0185] Aspect 7 is a method according to any one of aspects 1 to 6, further comprising purifying the top fraction into a purified top fraction consisting essentially of acetonitrile and toluene.

[0186] Aspect 8 is a method according to any one of Aspects 1 to 7, wherein the waste stream also contains one or more sulfur-containing compounds, the method also includes adding a sulfur-reactive compound to the waste stream, and the bottom fraction also includes the one or more sulfur-containing compounds.

[0187] Aspect 9 is a method according to any one of aspects 1 to 8, wherein the sulfur-reactive compound comprises silver nitrate.

[0188] Aspect 10 is a method according to any one of aspects 1 to 9, wherein the waste stream also contains one or more basic nitrogen-containing compounds, the method also includes adding an acidic reactive compound to the waste stream, and the bottom fraction also includes the one or more basic nitrogen-containing compounds.

[0189] Aspect 11 is a method according to any one of aspects 1 to 10, wherein the acidic reactive compound comprises formic acid.

[0190] Aspect 12 is a method for processing a waste stream, the method comprising: receiving the waste stream comprising acetonitrile, toluene and one or more sulfur-containing compounds; adding a sulfur-reactive compound to the waste stream; and fractionating the waste stream to produce a top fraction and a bottom fraction, the top fraction comprising the acetonitrile and the toluene of the waste stream, and the bottom fraction comprising the one or more sulfur-containing compounds of the waste stream.

[0191] Aspect 13 is a method according to any one of aspects 1 to 11 or aspect 12, wherein the top fraction further includes sulfur at a concentration of less than 25 ppm.

[0192] Aspect 14 is a method according to any one of aspects 1 to 11 or aspects 12 to 13, wherein the top fraction further includes sulfur at a concentration of less than 1 ppm.

[0193] Aspect 15 is a method according to any one of aspects 1 to 11 or aspects 12 to 14, wherein the sulfur-reactive compound comprises silver nitrate.

[0194] Aspect 16 is a method according to any one of aspects 1 to 11 or aspects 12 to 15, wherein during fractionation of the waste stream, the sulfur-reactive compound reacts with sulfur in the one or more sulfur-containing compounds and causes the sulfur to precipitate from the waste stream into the bottom fraction.

[0195] Aspect 17 is a method for processing a waste stream, the method comprising: receiving the waste stream comprising acetonitrile, toluene, and basic nitrogen-containing compounds; adding an acidic reactive compound to the waste stream; and fractionating the waste stream to produce a top fraction and a bottom fraction, the top fraction comprising the acetonitrile and the toluene of the waste stream, and the bottom fraction comprising the basic nitrogen-containing compounds of the waste stream.

[0196] Aspect 18 is a method according to any one of aspects 1 to 11, aspects 12 to 16, or aspect 17, wherein the top fraction further comprises one or more nitrogen-containing compounds at a concentration of less than 100 ppm.

[0197] Aspect 19 is a method according to any one of aspects 1 to 11, aspects 12 to 16, or aspects 17 and 18, wherein the acidic reactive compound comprises formic acid.

[0198] Aspect 20 is a method according to any one of Aspects 1 to 11, Aspects 12 to 16 or Aspects 17 to 19, wherein during fractionation of the waste stream, the acidic reactive compound reacts with the basic nitrogen-containing compound and causes the basic nitrogen-containing compound to precipitate from the waste stream into the bottom fraction.

[0199] Aspect 21 is a method for producing synthetic oligonucleotides, the method comprising: washing a reaction vessel containing one or more components of an oligonucleotide synthesis process with a blended washing solution comprising at least acetonitrile and toluene, the acetonitrile accounting for at least 70% of the blended washing solution; and recovering the synthetic oligonucleotides, the synthetic oligonucleotides comprising a minimum oligonucleotide purity.

[0200] Aspect 22 is a method according to aspect 21, wherein the blended wash solution comprises a substantially pure mixture of acetonitrile and toluene.

[0201] Aspect 23 is a method according to any one of aspects 21 and 22, wherein the blended wash solution is received as a purified waste stream recycled from the oligonucleotide synthesis process.

[0202] Aspect 24 is a method according to any one of aspects 21 to 23, wherein the substantially pure mixture of acetonitrile and toluene comprises at least 80% acetonitrile.

[0203] Aspect 25 is a method according to any one of aspects 21 to 24, wherein the substantially pure mixture of acetonitrile and toluene comprises at least 90% acetonitrile.

[0204] Aspect 26 is a method according to any one of aspects 21 to 24, wherein the substantially pure mixture of acetonitrile and toluene comprises an azeotropic mixture of acetonitrile and toluene.

[0205] Aspect 27 is a method according to any one of aspects 21 to 26, wherein the substantially pure mixture of acetonitrile and toluene comprises at least 76% acetonitrile.

[0206] Aspect 28 is a method according to any one of aspects 21 to 27, wherein the substantially pure mixture of acetonitrile and toluene comprises at least 5% toluene.

[0207] Aspect 29 is a method according to any one of aspects 21 to 28, wherein the substantially pure mixture of acetonitrile and toluene comprises at least 15% toluene.

[0208] Aspect 30 is a method according to any one of aspects 21 to 29, wherein the minimum oligonucleotide purity is not less than 70% purity.

[0209] Aspect 31 is a method according to any one of aspects 21 to 30, wherein the minimum oligonucleotide purity is greater than 72% purity.

[0210] Aspect 32 is a method according to any one of aspects 21 to 31, wherein the minimum oligonucleotide purity is greater than 75% purity.

[0211] Aspect 33 is a method according to any one of aspects 21 to 32, wherein the minimum oligonucleotide purity is not less than 90% purity.

[0212] Aspect 34 is a method according to any one of aspects 21 to 33, wherein the minimum oligonucleotide purity is greater than 92% purity.

[0213] Aspect 35 is a method according to any one of aspects 21 to 34, wherein the minimum oligonucleotide purity is greater than 95% purity.

[0214] Aspect 36 is a method according to any one of aspects 21 to 35, wherein the minimum oligonucleotide purity is greater than the oligonucleotide purity produced by washing the reaction vessel containing the one or more components of the oligonucleotide synthesis process with a wash solution consisting of acetonitrile.

[0215] Aspect 37 is a method according to any one of aspects 21 to 36, which is combined with any of the features according to any one of aspects 1 to 11, aspects 12 to 16, or aspects 17 to 20.

[0216] Aspect 38 is a method according to any one of aspects 1 to 11, comprising any of the features according to any one of aspects 21 to 36, aspects 12 to 16, or aspects 17 to 20.

[0217] Aspect 39 is a method according to any one of aspects 12 to 16, comprising any of the features according to any one of aspects 21 to 36, aspects 1 to 11, or aspects 17 to 20.

[0218] Aspect 40 is a method according to any one of aspects 17 to 20, comprising any of the features according to any one of aspects 21 to 36, aspects 1 to 11, or aspects 12 to 16.

Claims

1. A method for processing a waste stream, the method comprising: receiving the waste stream comprising acetonitrile, toluene, and one or more iodine-containing compounds; adding an iodine-reactive compound to the waste stream; The waste stream is fractionated to produce an overhead fraction and a bottoms fraction, the overhead fraction comprising the acetonitrile and the toluene of the waste stream, and the bottoms fraction comprising the one or more iodine-containing compounds of the waste stream.

2. The method of claim 1, wherein the iodine-reactive compound comprises sodium thiosulfate.

3. The method of claim 1, wherein the iodine-reactive compound comprises sodium thiosulfate and silver nitrate.

4. The method of claim 1, wherein the top fraction further comprises iodine at a concentration of less than 25 ppm.

5. The method of claim 1, wherein during fractionation of the waste stream, the iodine-reactive compound reacts with iodine in the one or more iodine-containing compounds and causes the iodine in the one or more iodine-containing compounds to precipitate from the waste stream into the bottoms fraction.

6. The process of claim 1 further comprising purifying the overhead fraction into a purified overhead fraction consisting essentially of acetonitrile and toluene.

7. A method for processing a waste stream, the method comprising: receiving the waste stream comprising acetonitrile, toluene, and one or more sulfur-containing compounds; adding a sulfur-reactive compound to the waste stream; as well as The waste stream is fractionated to produce an overhead fraction and a bottoms fraction, the overhead fraction comprising the acetonitrile and the toluene of the waste stream, and the bottoms fraction comprising the one or more sulfur-containing compounds of the waste stream.

8. The method of claim 7, wherein the top fraction further comprises sulfur at a concentration of less than 25 ppm.

9. The method of claim 7, wherein the sulfur-reactive compound comprises silver nitrate.

10. A method for processing a waste stream, the method comprising: receiving the waste stream comprising acetonitrile, toluene, and basic nitrogen-containing compounds; adding an acidic reactive compound to the waste stream; The waste stream is fractionated to produce an overhead fraction and a bottoms fraction, the overhead fraction comprising the acetonitrile and the toluene of the waste stream, and the bottoms fraction comprising the basic nitrogen-containing compounds of the waste stream.

11. The method of claim 10, wherein the top fraction further comprises one or more nitrogen-containing compounds at a concentration of less than 100 ppm.

12. The method of claim 10, wherein the acidic reactive compound comprises formic acid.

13. A method for producing a synthetic oligonucleotide, the method comprising: washing a reaction vessel containing one or more components of an oligonucleotide synthesis process with a blended wash solution comprising at least acetonitrile and toluene, wherein the acetonitrile comprises at least 70% of the blended wash solution; as well as The synthetic oligonucleotide is recovered, wherein the synthetic oligonucleotide comprises a minimum oligonucleotide purity.

14. The method of claim 13, wherein the blended wash solution comprises a substantially pure mixture of acetonitrile and toluene.

15. The method of claim 13, wherein the blended wash solution is received as a purified waste stream recycled from the oligonucleotide synthesis process.

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