Process for drying hydrogen (chloro)fluoroolefins

Abstract

The present invention provides methods for drying hydro(chloro)fluoroolefins. In particular, the present invention provides a method for purifying a fluid comprising a first drying stage comprising contacting a first fluid stream comprising one or more hydro(chloro)fluoroolefins and water with a source of sulfuric acid to produce a first treated fluid stream comprising the hydro(chloro)fluoroolefins and a first spent sulfuric acid stream, wherein the first treated fluid stream comprises a lower concentration of water compared to the first fluid stream.

Description

[0001] This application is a divisional application of the application filed on July 14, 2016, with application number 201680039228.9 and entitled "Method for Drying Hydrofluoroolefins". Technical Field

[0002] This invention relates to methods suitable for the preparation of hydrochlorofluoroolefins, for example, concerning the washing and / or purification of intermediate and product streams. Specifically, the invention provides methods for washing and / or purifying product streams containing fluoropropylenes, such as 1,3,3,3-tetrafluoropropylene (HFO-1234ze) and 2,3,3,3-tetrafluoropropylene (HFO-1234yf). Background Technology

[0003] (Hydrohalides) are commonly used as refrigerants or propellant materials and as foaming agents. In the last 20 years, many of the (hydrohalides) used in these applications have changed because some of these materials (such as dichlorofluoromethane, R12) have been found to deplete the Earth's ozone layer, while others (such as 1,1,1,2-tetrafluoroethane, R134a) have unacceptably high levels of activity as greenhouse gases.

[0004] Hydrofluoroolefins (HFCs) have emerged as a class of compounds that can address these issues by offering good performance as refrigerants, propellant materials, and foaming agents, while also possessing the potential for low ozone depletion and low global warming.

[0005] Several methods for preparing hydrofluoroolefins have been proposed. These methods require the removal of unused reagents and reaction byproducts before the resulting product is in a marketable state. It has been found that previous purification techniques used in the preparation of hydrofluorocarbons degrade hydrofluoroolefin products, increasing the number and quantity of byproducts and reducing the overall product yield. Summary of the Invention

[0006] Therefore, there is a need for efficient methods for cleaning and / or purifying hydrofluoroolefin product streams that minimize associated product degradation, which reduces product yield and may generate waste material streams containing hazardous substances and / or are difficult or costly to handle. This invention provides such methods.

[0007] There is also a need for efficient methods to remove unwanted water from hydrofluoroolefin product streams, as methods such as washing and / or purifying the product stream may introduce water into the stream. This invention provides such methods.

[0008] In a first aspect, the present invention provides a method comprising a first drying stage comprising contacting a first fluid material stream comprising one or more hydrofluoroolefins and water with a source of sulfuric acid to produce a first treated fluid material stream comprising hydrofluoroolefins and a first used sulfuric acid material stream, wherein the first treated fluid material stream comprises a lower concentration of water compared to the first fluid material stream.

[0009] Preferably, the first treated fluid stream contains less than 1% by weight of water, for example, less than about 500 ppm of water. More preferably, the first treated fluid stream contains less than about 250 ppm of water, less than 100 ppm of water, or less than 10 ppm of water.

[0010] Preferably, the first fluid stream contains less than about 20% HF by weight, such as less than 10% HF by weight, less than 5% HF by weight, or less than 1% HF by weight. In some embodiments, the first fluid stream contains no more than trace amounts of HF.

[0011] Preferably, the first fluid stream contains less than about 20% by weight HCl, such as less than 10% by weight HCl, less than 5% by weight HCl, or less than 1% by weight HCl. In some embodiments, the first fluid stream contains no more than trace amounts of HCl.

[0012] Preferably, the first drying stage is carried out in a first sulfur-containing purification container. Preferably, the residence time of the first fluid material flow in the first purification container is between about 1 second and about 60 seconds. Preferably, the residence time of the first sulfuric acid source in the first sulfur-containing purification container is between about 5 seconds and 10,000 seconds.

[0013] Preferably, at least 50% by weight of the first fluid material stream comprises hydrofluoroolefins. More preferably, at least 60%, 70%, or 80% by weight of the first fluid material stream comprises hydrofluoroolefins. In some preferred embodiments, at least 50% by weight of the first fluid material stream comprises one hydrofluoroolefin. More preferably, at least 60%, 70%, or 80% by weight of the first fluid material stream comprises one hydrofluoroolefin.

[0014] In some preferred embodiments, at least 50% by weight of the first fluid material stream comprises hydrofluoroolefins selected from the group consisting of hydrofluoropropylene, hydrochlorofluoropropylene, hydrofluoroethylene, hydrofluorobutene, and hydrochlorofluorobutene. More preferably, at least 60%, 70%, or 80% by weight of the first fluid material stream comprises hydrofluoroolefins selected from the group consisting of hydrofluoropropylene, hydrochlorofluoropropylene, hydrofluoroethylene, hydrofluorobutene, and hydrochlorofluorobutene. Preferred hydrofluoroolefins include HFO-1234yf, HFO-1234ze, 1-chloro-3,3,3-trifluoropropylene (HCFO-1233zd), 2-chloro-3,3,3-trifluoropropylene (HCFO-1233xf), 1,1,1-4,4,4-hexafluoro-but-2-ene (HFO-1336mzz), and 1,1-difluoroethylene (HFO-1132a).

[0015] In a preferred embodiment, the first sulfuric acid source comprises aqueous sulfuric acid at a concentration between about 60% by weight and about 98% by weight. More preferably, the first sulfuric acid source comprises aqueous sulfuric acid at a concentration between about 75% by weight and about 95% by weight, for example, between about 78% by weight and about 94% by weight. In some embodiments, the first sulfuric acid source comprises aqueous sulfuric acid at a concentration between about 78% by weight and about 90% by weight. The inventors have found that even a small reduction in sulfuric acid concentration can provide a significant reduction in hydrochlorofluoroolefin degradation compared to concentrated sulfuric acid, thereby providing a greater final product yield and reducing the concentration of potentially harmful organic matter in the used sulfuric acid stream.

[0016] Preferably, the first fluid stream is in the gas phase when in contact with a sulfuric acid source. More preferably, the first fluid stream is contacted with the sulfuric acid source at a temperature between about 10°C and about 70°C, for example, between about 20°C and about 60°C. Most preferably, the first fluid stream is contacted with the sulfuric acid source at a temperature between about 20°C and 40°C, for example, between about 25°C and 35°C (e.g., about 30°C). Preferably, the first fluid stream is contacted with the sulfuric acid source at a sufficiently high temperature to minimize or prevent the condensation of hydrofluoroolefins.

[0017] Preferably, the first used sulfur-containing material stream contains less than about 20,000 ppm fluorine, for example less than about 15,000 ppm fluorine, such as less than about 10,000 ppm fluorine, less than about 8,000 ppm fluorine, less than about 5,000 ppm fluorine, less than about 4,000 ppm fluorine, less than about 3,000 ppm fluorine, or less than about 2,000 ppm fluorine. In some embodiments, the first used sulfur-containing material stream contains less than about 1,000 ppm fluorine, for example less than about 500 ppm fluorine. In the most preferred embodiment, the first used sulfur-containing material stream contains less than about 100 ppm fluorine, for example less than about 80 ppm fluorine, less than about 50 ppm fluorine, less than about 40 ppm fluorine, or less than about 25 ppm fluorine.

[0018] In a preferred embodiment, the first used sulfur-containing material stream contains less than about 10,000 ppm of total organic carbon. For example, in some embodiments, the first used sulfur-containing material stream contains less than about 8,000 ppm of total organic carbon, less than about 5,000 ppm of total organic carbon, less than about 4,000 ppm of total organic carbon, less than about 3,000 ppm of total organic carbon, or less than about 2,000 ppm of total organic carbon. In some embodiments, the first used sulfur-containing material stream contains less than about 1,000 ppm of total organic carbon. In the most preferred embodiment, the first used sulfur-containing material stream contains less than about 500 ppm of total organic carbon, such as less than about 250 ppm of total organic carbon, less than about 100 ppm of total organic carbon, less than about 50 ppm of total organic carbon, or less than about 25 ppm of total organic carbon.

[0019] In some embodiments, the method includes a second drying step, comprising contacting a first treated fluid stream with a second sulfuric acid source to produce a second treated fluid stream comprising hydrofluoroolefins and a second used sulfuric acid stream, wherein the second treated fluid stream contains a lower concentration of water compared to the first treated fluid stream. In such embodiments, it is preferred (but not mandatory) that the first sulfuric acid source contains aqueous sulfuric acid at a concentration between about 78% by weight and about 90% by weight.

[0020] The inventors have discovered that by providing a second drying step, it is possible to carry out the first drying step under milder conditions, thereby removing a large amount of water from the first fluid material stream while minimizing the reaction with hydrofluoroolefins.

[0021] Preferably, the second drying stage is carried out in a second sulfur-containing purification container. Preferably, the residence time of the first treated fluid material stream in the second purification container is between about 1 second and about 60 seconds. Preferably, the residence time of the second sulfuric acid source in the second sulfur-containing purification container is between about 5 seconds and 10,000 seconds. When a second drying step is included, it is preferred that the residence time of the first sulfuric acid source in the first sulfur-containing purification container is between about 5 seconds and 500 seconds.

[0022] Preferably, the second treated fluid stream contains less than about 500 ppm of water. More preferably, the second treated fluid stream contains less than about 250 ppm of water, less than 100 ppm of water, or less than 10 ppm of water.

[0023] In a preferred embodiment, the second sulfuric acid source comprises aqueous sulfuric acid at a concentration between about 60% by weight and about 98% by weight. More preferably, the second sulfuric acid source comprises aqueous sulfuric acid at a concentration between about 75% by weight and about 95% by weight, for example, between about 78% by weight and about 94% by weight. In some embodiments, the second sulfuric acid source comprises aqueous sulfuric acid at a concentration between about 90% by weight and about 94% by weight.

[0024] Preferably, the first treated fluid stream is in the gas phase when in contact with the second sulfuric acid source. Preferably, the first fluid stream is contacted with the sulfuric acid source at a temperature between about 10°C and about 70°C, for example, between about 20°C and about 60°C. Most preferably, the first treated fluid stream is contacted with the second sulfuric acid source at a temperature between about 20°C and 40°C, for example, between about 25°C and 35°C (e.g., about 30°C). Preferably, the first fluid stream is contacted with the sulfuric acid source at a sufficiently high temperature to minimize or prevent the condensation of hydrofluoroolefins.

[0025] Preferably, the second used sulfur-containing material stream contains less than about 20,000 ppm fluorine, for example less than about 15,000 ppm fluorine, such as less than about 10,000 ppm fluorine, less than about 8,000 ppm fluorine, less than about 5,000 ppm fluorine, less than about 4,000 ppm fluorine, less than about 3,000 ppm fluorine, or less than about 2,000 ppm fluorine. In some embodiments, the second used sulfur-containing material stream contains less than about 1,000 ppm fluorine, for example less than about 500 ppm fluorine. In the most preferred embodiment, the second used sulfur-containing material stream contains less than about 100 ppm fluorine, for example less than about 80 ppm fluorine, less than about 50 ppm fluorine, less than about 40 ppm fluorine, or less than about 25 ppm fluorine.

[0026] In a preferred embodiment, the second used sulfur-containing material stream contains less than about 10,000 ppm of total organic carbon. For example, in some embodiments, the second used sulfur-containing material stream contains less than about 8,000 ppm of total organic carbon, less than about 5,000 ppm of total organic carbon, less than about 4,000 ppm of total organic carbon, less than about 3,000 ppm of total organic carbon, or less than about 2,000 ppm of total organic carbon. In some embodiments, the second used sulfur-containing material stream contains less than about 1,000 ppm of total organic carbon. In the most preferred embodiment, the second used sulfur-containing material stream contains less than about 500 ppm of total organic carbon, such as less than about 250 ppm of total organic carbon, less than about 100 ppm of total organic carbon, less than about 50 ppm of total organic carbon, or less than about 25 ppm of total organic carbon.

[0027] Preferably, the first and / or (if a second treated fluid material stream is generated) contains hydrofluoroolefins in a substantially pure state or as part of a mixture of hydrofluoroolefins and / or other halogenated organic compounds.

[0028] In a preferred embodiment, the first and / or (if a) second treated fluid stream is contacted with the adsorbent material. The adsorbent material removes or reduces the concentration of one or more components selected from the following: residual acids (e.g., residual HF and / or residual HCl), residual water, and / or residual impurities, such as residual organic impurities.

[0029] In some embodiments, the adsorbent material comprises soda lime. In other embodiments, the adsorbent material comprises one or more molecular sieves, for example, having a... arrive For example, about To date One or more zeolites with pore sizes within the specified range.

[0030] In some embodiments, the second treated fluid stream (optionally in contact with an adsorbent material) undergoes distillation to separate some or all of the remaining components, for example, to provide a substantially pure product stream.

[0031] In some preferred embodiments, the method includes the aforementioned acid removal step. The acid removal step preferably includes treating the crude product stream to remove at least a portion of any HF and / or HCl from the crude product stream to provide a first fluid stream. Preferably, the crude product stream is a product stream of a dehydrohalogenation reaction (e.g., a dehydrofluorination and / or dechlorination reaction). More preferably, the dehydrohalogenation reaction provides one or more hydro(chloro)fluoroolefins. Therefore, the crude product stream may contain HF and / or HCl at a molar concentration of about 0.5 to 1.5 times (e.g., 0.8 to 1.2 times) the molar concentration of the hydro(chloro)fluoroolefins in the crude product stream. The crude product stream may also contain one or more (hydro)haloalkanes, which may represent byproducts of the dehydrohalogenation reaction and / or one or more unreacted starting materials.

[0032] In a preferred embodiment, the acid removal step includes contacting the crude product stream with water to produce a used aqueous acid (e.g., HF and / or HCl) stream and a treated product stream, the treated product stream having a lower acid concentration (e.g., lower HF and / or HCl concentration) compared to the crude product stream.

[0033] In alternative embodiments, the acid removal step comprises contacting the crude product stream with an aqueous acid source (e.g., a source of aqueous HF and / or HCl) to produce a used aqueous acid (e.g., HF and / or HCl) stream and a treated product stream, the treated product stream having a lower acid concentration (e.g., a lower HF and / or HCl concentration) compared to the crude product stream. Preferably, the aqueous acid source comprises aqueous HF at a concentration of at least about 40% by weight or at least about 50% by weight. Most preferably, the aqueous acid source comprises aqueous HF at a concentration between about 40% by weight and about 60% by weight. In alternative embodiments, the aqueous acid source comprises aqueous sulfuric acid, for example, at a concentration of less than about 98% by weight, such as less than about 95% by weight or less than about 90% by weight.

[0034] In some embodiments, HF and / or HCl are recovered from the used aqueous acid stream, for example, by flash separation and / or distillation.

[0035] In some embodiments, the treated product stream is provided directly to the first drying stage, for example, in the form of a first fluid stream. In other embodiments, the treated product stream undergoes one or more other processing steps before being provided to the first drying stage.

[0036] Preferably, the treated product stream undergoes a second acid removal step. The second acid removal step preferably involves contacting the treated product stream with an aqueous alkali solution to produce a second treated product stream and a used aqueous alkali solution stream, the second treated product stream having a lower acid concentration compared to the treated product stream. In a preferred embodiment, the aqueous alkali solution source comprises an aqueous caustic alkali, such as aqueous NaOH or KOH. Preferably, the aqueous NaOH or KOH is provided at a concentration of less than about 20% by weight, for example, less than about 15% by weight, less than about 10% by weight, or less than about 5% by weight.

[0037] In some embodiments, the second processed product stream is provided directly to the first drying stage, for example, in the form of a first fluid stream. In other embodiments, the second processed product stream undergoes one or more other processing steps before being provided to the first drying stage.

[0038] In another aspect of the invention, an integrated method for preparing one or more hydrofluoroolefins is provided, comprising:

[0039] (i) Dehydrohalogenating one or more hydrofluoroalkanes to form a crude product stream;

[0040] (ii) subjecting the crude product stream to a first acid removal step, comprising contacting the crude product stream with water or an aqueous acid source to produce a treated product stream and a used aqueous acid stream;

[0041] (iii) Optionally subjecting the treated product stream to a second acid removal step, comprising contacting the treated product stream with a source of alkaline solution to generate a second treated product stream and a used alkaline solution stream;

[0042] (iv) subjecting the treated product stream or (if a second treated product stream is generated) to a first drying stage in the form of a first fluid stream, comprising contacting the first fluid stream with a source of sulfuric acid to generate a first treated fluid stream comprising hydrofluoroolefin and a first used sulfuric acid stream.

[0043] In another aspect, the present invention provides a method for removing acid from a crude product stream of a dehydrohalogenation reaction, the crude product stream containing one or more hydrofluoroolefins, the method comprising:

[0044] (i) subjecting the crude product stream to a first acid removal step, comprising contacting the crude product stream with water or an aqueous acid source to produce a treated product stream and a used aqueous acid stream;

[0045] (ii) Optionally subjecting the treated product stream to a second acid removal step, comprising contacting the treated product stream with a source of alkaline solution to produce a second treated product stream and a used alkaline solution stream.

[0046] In some embodiments, the method includes subjecting a treated product stream or (if a second treated product stream is generated) to a first drying stage in the form of a first fluid stream, including contacting the first fluid stream with a source of sulfuric acid to generate a first treated fluid stream comprising hydrofluoroolefin and a first used sulfuric acid stream.

[0047] In another aspect, the present invention provides a used washing liquid comprising aqueous sulfuric acid at a concentration of less than about 98 wt% (e.g., less than about 95 wt%, 90 wt%, 85 wt%, 80 wt%, 75 wt%, 70 wt%, 65 wt%, 60 wt%, 55 wt%, or 50 wt%) and at least one compound selected from: fluoroacrylic acid, polyfluoroacrylic acid, formic acid, and fluoroformaldehyde, and / or one or more unsaturated fluorinated oligomers. Preferably, the used washing liquid contains sulfuric acid at a concentration between 50 wt% and 98 wt%, for example, between 75 wt% and 95 wt%, for example, 75 wt%, and the sulfuric acid concentration in the purification step that produces the used liquid.

[0048] Preferably, the used liquid contains less than about 20,000 ppm fluorine, less than about 15,000 ppm fluorine, less than about 10,000 ppm fluorine, less than about 8,000 ppm fluorine, less than about 5,000 ppm fluorine, less than about 4,000 ppm fluorine, less than about 3,000 ppm fluorine, less than about 2,000 ppm fluorine, less than about 1,000 ppm fluorine, less than about 500 ppm fluorine, less than about 100 ppm fluorine, less than about 80 ppm fluorine, less than about 50 ppm fluorine, less than about 40 ppm fluorine, or less than about 25 ppm fluorine.

[0049] Preferably, the used liquid contains less than about 10,000 ppm total organic carbon, less than about 8,000 ppm total organic carbon, less than about 5,000 ppm total organic carbon, less than about 4,000 ppm total organic carbon, less than about 3,000 ppm total organic carbon, or less than about 2,000 ppm total organic carbon, less than about 1,000 ppm total organic carbon, less than about 500 ppm total organic carbon, less than about 250 ppm total organic carbon, less than about 100 ppm total organic carbon, less than about 50 ppm total organic carbon, or less than about 25 ppm total organic carbon.

[0050] In another aspect of the invention, the use of the used washing liquid as described above is provided for preparing a regenerated washing liquid for use in the purification methods described herein, comprising sulfuric acid having a concentration between about 60% by weight and about 98% by weight (e.g., 75% by weight and about 95% by weight, for example, between about 78% by weight and about 94% by weight or between about 78% by weight and about 90% by weight).

[0051] In another aspect, the present invention provides the use of the regenerated washing liquid as described herein in a purification method as described herein.

[0052] In other embodiments, the used liquid may be treated to neutralize it and remove at least some of any fluorine and / or organic compounds for safe disposal.

[0053] As will be understood by those skilled in the art, any preferred and alternative embodiments presented above are applicable to any of the aspects described in this invention. Attached Figure Description

[0054] Embodiments of the present invention will now be described with reference to the following examples and figures:

[0055] Figure 1 A schematic diagram of a purification chain for carrying out the method according to the present invention is shown;

[0056] Figures 2 to 7 The surface response curves show the fluorine and total organic carbon produced by contacting HFO-1234ze with sulfuric acid. Detailed Implementation

[0057] Embodiments of the present invention are shown in Figure 1 The diagram shows a purified chain 10 used to process the crude product from the dehydrohalogenation reaction. The crude product contains HFO-1234ze, but the purified chain can also be used to prepare other hydrochlorofluoroolefins, such as HFO-1234yf, HCFO-1233zd, HFO-1233xf, HFO-1132a, and HFO-1336mzz. In addition to HFO-1234ze, the crude product stream also contains HF and / or HCl (e.g., generated from dehydrohalogenation), unreacted starting materials (e.g., 1,1,1,3,3-pentafluoropropane (HFC-245fa) and / or 1-chloro-1,3,3,3-tetrafluoropropane (HCFC-244fa)), and other organic substances, such as those generated as byproducts of the dehydrohalogenation reaction.

[0058] In simple terms, the crude product stream is fed into the first purification column 20 via feed line 22, while water is supplied to the purification column 20 via purification line 24. Purification line 24 provides a large quantity of water sufficient to produce an effluent with an HF concentration of approximately 5% by weight. In purification column 20, most of the HF and / or HCl in the crude product stream dissolves or is otherwise absorbed in the water to produce a first used product stream containing aqueous HF and / or HCl, which flows from purification column 20 through the first effluent line 26. The first treated product stream (with significantly reduced HF and / or HCl content) exits the first purification column 20 and is delivered to the second purification column 30 via the second feed line 28.

[0059] In the second purification column 30, the first treated product stream comes into contact with a supply source of aqueous caustic alkali material (e.g., aqueous KOH), which is supplied to the purification column 30 via the second purification line 34. Preferably, the concentration of the aqueous KOH can be about 20% by weight. The aqueous caustic alkali material reacts with trace amounts of HF and / or HCl remaining in the treated product stream to produce a used caustic alkali stream, which flows from the purification column 30 through the second effluent line 36. The second treated product stream flows from the second purification column 30 through the third feed line 38 to the third purification column 40.

[0060] The third purge column 40 is adapted to remove water introduced into the second treated product stream during the treatment in the first and second purge columns 20, 30. In the third purge column, the second treated product stream is contacted with a source of aqueous sulfuric acid at a concentration of about 78% to about 90% by weight, which is supplied to the purge column 40 via the third purge line 44. The aqueous sulfuric acid is used to remove a portion of the water from the second treated product stream while the concentration of sulfuric acid is low enough to reduce the risk of significant degradation of the desired final product of HFO-1234ze. The used aqueous sulfuric acid is removed from the third purge column 40 via the third effluent line 46, while the third treated product stream passes from the third purge column 40 through the third feed line 48 to the fourth purge column 50.

[0061] A fourth purification column 50 is used to further remove water from the third treated product stream. In the fourth purification column 50, the third treated product stream is contacted with a source of aqueous sulfuric acid at a concentration of about 90% to about 98% by weight, most preferably about 90% by weight, supplied to the purification column 50 via a third purification line 54. The aqueous sulfuric acid is used to highly remove residual water from the third treated product stream. The relatively high concentration of sulfuric acid ensures a higher water removal rate than in the third purification column 30; however, the lower initial water concentration in the third treated product stream compared to the second product stream allows for shorter contact times and / or acid volumes, thereby reducing the risk of significant degradation of the desired final product of HFO-1234ze. Used aqueous sulfuric acid is removed from the fourth purification column 50 via a fourth effluent line 56, while the fourth treated product stream passes from the fourth purification column 50 through a fourth feed line 48 to the polishing bed 60.

[0062] Polishing bed 60 contains an adsorbent material (such as Sofnolime (RTM) quicklime) or a molecular sieve (such as one with a specific structure). arrive (Zeolite with pore size within the range). The polishing bed removes any residual water, acid, and impurities from the fourth-treated product stream. The resulting product stream may undergo further distillation.

[0063] All effluent streams 26, 36, 46, and 56 can be discarded or conveyed for recycling to ensure the further use of any commercially valuable components (such as HF and / or HCl and / or any organic components they may contain). However, in some embodiments, the effluent stream 56 of the fourth purge column 50 can be recycled by supplying it to the third purge line 30 for use in the third purge column 40.

[0064] In some embodiments, the first purge column 20 may be replaced by one or more columns, wherein the purge fluid contains aqueous HF, for example, at a concentration of about 50% by weight. In such embodiments, it is anticipated that the concentration of Hf in the effluent will exceed the concentration of the purge fluid and that efficient recovery of Hf will be achieved, for example, by absorbing Hf into the wash liquid to increase the Hf concentration to about 70% by weight, followed by distilling about 70% by weight of Hf into a substantially anhydrous HF feed stream (which can be recycled for other processes) and a feed stream containing about 50% by weight of HF, which can be returned to the column to replace column 20.

[0065] Reference Example

[0066] Batch experiments were conducted using 30 ml of sulfuric acid of different concentrations in a 100 ml Hastelloy autoclave. After evacuating the headspace, the reactor was filled with HFO-1234zeE to a pressure of 1.0 barg (approximately 1.2 g of HFO-1234zeE). The autoclave was immersed in a water bath at different temperatures and stirred at 500 rpm for different time periods, as shown in Table 1.

[0067] Fluorine Measurement

[0068] The fluoride content of the used liquid from each autoclave was tested using an ion-selective electrode. The solution was adjusted to pH 5.5 with a buffer solution prior to measurement. The original sulfuric acid solution contained no fluoride. The results are shown in Table 1.

[0069] Total organic carbon measurement

[0070] The total organic carbon (TOC) content of the used liquid from each autoclave was tested before and 30 minutes after bubbling with compressed air. The original sulfuric acid solution contained no organic carbon. The results are shown in Table 1.

[0071] Table 1

[0072]

[0073]

[0074] The results are plotted as a series of response surface curves, such as Figures 2 to 5 As shown in the image.

[0075] Figure 2 The results show the relationship between fluoride content and temperature and contact time after reaction with HFO-1234zeE at a constant sulfuric acid concentration of 98 wt%. Increasing time and temperature individually appears to increase the fluoride content in the used solution, but their combination has the greatest effect, as shown by the upward slope of the surface at the far end of the curve for the highest temperature and longest contact time.

[0076] Figure 3 The table shows the TOC content measured with HFO-1234zeE at a concentration of 98 wt% at different temperatures and contact times with H2SO4. Furthermore, increasing temperature and time individually increases the TOC content, but their combination has the greatest effect. The relatively high total TOC content indicates a relatively vigorous reaction between organic matter and H2SO4.

[0077] Bubbling each solution sample with air was designed to remove any intermediate to low boiling point substances resulting from decomposition, highlighting the preferred treatment options for the solution before disposal. However, results showed no statistically significant difference between samples before and after bubbling within the 95% confidence limits.

[0078] Figure 4 The response surface curves show how the residual fluoride content in the solution varies between 78 wt% and 98 wt% with contact time and sulfuric acid concentration at a constant temperature of 30 °C. At low sulfuric acid concentrations and short contact times, only extremely low levels of fluoride are present, increasing very slowly with increasing contact time and sulfuric acid concentration. As the sulfuric acid concentration reaches 98 wt%, the fluoride content increases sharply and suddenly, especially at longer contact times.

[0079] TOC results were obtained at a constant temperature of 30°C for sulfuric acid concentrations varying from 78 wt% to 98 wt% (see [reference]). Figure 5 The results showed a similar trend to those for fluorine, where very little TOC was present at low sulfuric acid concentrations and short contact times, but the TOC content appeared to rise rapidly as the concentration reached 98% by weight, regardless of the contact time.

[0080] Other experiments were conducted to investigate the effect of sulfuric acid concentrations exceeding 90% by weight on the stability of HFO-1234zeE, and the results are shown in Table 2. TOC was not studied in these experiments.

[0081] Table 2

[0082] Example Temperature (°C) Time (minutes) <![CDATA[[H2SO4] (wt%)]]> F (ppm) 30 30 90 90 33.2 31 30 30 98 98.8 32 30 60 99.7 160.6 33 30 60 94 63.6 34 30 60 88.3 8 35 30 30 90 38.3 36 30 17.6 94 25.4 37 30 102.4 94 64 38 30 60 94 57.4 39 30 60 94 56.4 40 30 60 94 57.6 41 30 60 94 43 42 30 90 98 316 43 30 30 94 37.4 44 30 60 96 66.4 45 30 60 93.2 15.2 46 30 17.6 96 25.2 47 30 30 98 56.6 48 30 102.4 96 144.4 49 30 90 94 76.4 50 30 90 98 141.2 51 30 60 96 69.4 52 30 60 96 72 53 30 60 98.8 165.6 54 30 60 96 68.4 55 30 60 96 77

[0083] Figure 6 The surface response curves are shown at a constant temperature of 30°C for fluorine concentrations between 90 wt% and 98 wt% sulfuric acid. It can be observed that fluorine concentrations gradually increase with increasing contact time and sulfuric acid concentration. At lower concentrations, an acceptablely low level of fluorine appears to exist. Figure 7 A similar curve shows sulfuric acid concentrations concentrated between 94% and 98% by weight.

[0084] The concentration of water in HFO-1234zeE is a function of the concentration of sulfuric acid it comes into contact with and the effectiveness of the purifier. Data shows that the partial pressure of water in sulfuric acid solutions of different concentrations can be used to determine the equilibrium concentration. This data suggests that the concentration of sulfuric acid supplied to the final (or sole) sulfuric acid purifier should exceed 80 wt% in order to keep the concentration of water in HFO-1234zeE below 100 ppm. Results of the present invention show that, with 94 wt% sulfuric acid, the fluoride content ranges from 37 to 76 ppm under different contact times. As the sulfuric acid concentration increases from 94 wt%, the fluoride concentration in the used sulfuric acid begins to rise rapidly. Therefore, it appears that the optimal sulfuric acid concentration for drying hydrofluoroolefins (such as HFO-1234ze) will be between about 90 wt% and about 94 wt%. As can also be seen from the results presented above, sulfuric acid concentrations below 90 wt% (e.g., between 78 wt% and 90 wt%) provide manageable levels of fluoride and TOC (and thus provide manageable product degradation), and therefore, concentrations in this range are considered optimal for the first of the two sulfuric acid drying stages. As can also be seen from the results presented above, sulfuric acid concentrations below 90 wt% (e.g., between 78 wt% and 90 wt%) provide manageable levels of fluorine and TOC (and thus provide manageable product degradation), and therefore, concentrations in the range described above are found to be optimal for the first of the two sulfuric acid drying stages.

[0085] Reference Example 56

[0086] Another experiment was conducted using 30 mL of 94% by weight H₂SO₄ heated to 30°C and stirred at 500 rpm. After evacuating the headspace, the autoclave was filled to 2.0 barg with HFO-1234yf (1.2 g) and reacted for 60 min. The fluorine concentration of the used H₂SO₄ liquid was then analyzed. The used sulfuric acid solution did not contain detectable fluorine.

[0087] Example 57

[0088] Hydrofluoroolefins were dried using sulfuric acid of both high and low concentrations.

[0089] 300 g of HFO-1234ze(E) or HFO-1234yf was added to a 500 mL Whitey autoclave and doped with approximately 300 ppm of water. The moisture content of the composition was analyzed before and after the addition of water. 30 g of moistened hypofluoric acid was added to a Whitey autoclave containing 50 mL of sulfuric acid (at a concentration of 98 wt% (aqueous solution) or 80 wt% (aqueous solution)) and shaken for 10 minutes. The dried hypofluoric acid was then separated from the Whitey autoclave at 10 °C and the moisture content was analyzed. The results of drying with 98 wt% H2SO4 (aqueous solution) are presented in Table 3, and the results of drying with 80 wt% H2SO4 (aqueous solution) are presented in Table 4.

[0090] Table 3

[0091]

[0092] Table 4

[0093]

[0094] This direct comparison clearly shows that sulfuric acid maintains sufficiently high drying performance even at lower hydrofluoroolefin concentrations. This high performance at lower concentrations results in less degradation of the desired hypofluorescent acid and thus a greater yield of the final product. Lower sulfuric acid concentrations also reduce the concentration of potentially harmful organic matter in the used sulfuric acid stream.

[0095] Example 58

[0096] Aqueous samples were dried (E)-1234 ze at 60 °C in a purified medium containing 98 wt% sulfuric acid [contacted with it] [by stirring]. The mixture was then neutralized and extracted with a solvent. The solvent extract was dried, filtered, and concentrated. A sample of the concentrated extract was obtained and analyzed by 1-D NMR (… 1 H, 13 C and 19 F), 2-D NMR ( 1 H- 1 H COSY and 1 H- 13 C HSQC), gas chromatography and ISE were used to analyze and identify decomposition products and pathways.

[0097] Several decomposition products were found in the used purification solution, including fluoroacrylic acid, polyfluoroacrylic acid, formic acid and fluoroformaldehyde, as well as several unsaturated fluorinated oligomers.

[0098] Unless the context otherwise indicates, preferences and choices of a given aspect, feature, or parameter of the invention should be considered as disclosed in combination with any and all preferences and choices of all other aspects, features, and parameters of the invention.

[0099] When a molecule (e.g., HFO-1234ze) is available in E and Z isomers, the general disclosure of the molecule also refers to the E and Z isomers.

Claims

1. A method for purifying a fluid, comprising a first drying stage, comprising contacting a first fluid material stream comprising one or more hydrofluoroolefins and water with a source of sulfuric acid at a concentration between 75% by weight and 95% by weight to produce a first treated fluid material stream comprising the hydrofluoroolefins and a first used sulfuric acid material stream, wherein the first treated fluid material stream comprises a lower concentration of water compared to the first fluid material stream, and wherein the hydrofluoroolefin comprises one or more of HFO-1234yf and HFO-1234ze.

2. A method comprising an integrated process for preparing one or more hydrofluoroolefins selected from HFO-1234yf and HFO-1234ze, the method comprising: Dehydrohalogenation of one or more hydrofluoroalkanes to form a crude product stream; (i) subjecting the crude product stream to a first acid removal step, comprising contacting the crude product stream with water or an aqueous acid source to produce a treated product stream and a used aqueous acid stream; (ii) Optionally subjecting the treated product stream to a second acid removal step, comprising contacting the treated product stream with a source of alkaline solution to generate a second treated product stream and a used alkaline solution stream; (iii) subjecting the treated product stream or, if generated, the second treated product stream to a first drying stage in the form of a first fluid stream, comprising contacting the first fluid stream with a sulfuric acid source at a concentration between 75% and 95% by weight to generate a first treated fluid stream comprising the hydrofluoroolefin and the first used sulfuric acid stream.

3. The method according to claim 1 or claim 2, wherein the first treated fluid stream contains less than 1% by weight of water.

4. The method according to claim 1 or claim 2, wherein the first treated fluid stream contains less than 500 ppm of water.

5. The method according to claim 1 or claim 2, wherein the first fluid material stream contains less than 20% by weight HF.

6. The method of claim 1 or claim 2, wherein the first fluid material stream contains less than 10% by weight HF.

7. The method according to claim 1 or claim 2, wherein the first fluid material stream contains less than 5% HF by weight.

8. The method according to claim 1 or claim 2, wherein the first fluid material stream contains less than 1% HF by weight.

9. The method according to claim 1 or claim 2, wherein the first fluid material stream contains less than 20% by weight HCl.

10. The method of claim 1 or claim 2, wherein the first fluid material stream contains less than 10% by weight HCl.

11. The method of claim 1 or claim 2, wherein the first fluid material stream contains less than 5% by weight HCl.

12. The method of claim 1 or claim 2, wherein the first fluid material stream contains less than 1% by weight HCl.

13. The method according to claim 1 or claim 2, wherein at least 50% by weight of the first fluid material stream is the hydrofluoroolefin.

14. The method of claim 13, wherein at least 60% by weight of the first fluid material stream is the hydrofluoroolefin.

15. The method of claim 13, wherein at least 70% by weight of the first fluid material stream is the hydrofluoroolefin.

16. The method of claim 13, wherein at least 80% by weight of the first fluid material stream is the hydrofluoroolefin.

17. The method according to claim 1 or claim 2, wherein the sulfuric acid source comprises aqueous sulfuric acid at a concentration between 78% by weight and 94% by weight.

18. The method according to claim 1 or claim 2, wherein the sulfuric acid source comprises aqueous sulfuric acid at a concentration between 78% and 90% by weight.

19. The method according to claim 1 or claim 2, wherein the first fluid material stream is contacted with the sulfuric acid source at a temperature between 10°C and 70°C.

20. The method according to claim 1 or claim 2, wherein the first fluid material stream is contacted with the sulfuric acid source at a temperature between 20°C and 60°C.

21. The method according to claim 1 or claim 2, wherein the first fluid material stream is contacted with the sulfuric acid source at a temperature between 20°C and 40°C.

22. The method according to claim 1 or claim 2, wherein the first fluid material stream is contacted with the sulfuric acid source at a temperature between 25°C and 35°C.

23. The method according to claim 1 or claim 2, wherein the first fluid material stream is contacted with the sulfuric acid source at 30°C.

24. The method of claim 1 or claim 2, wherein the first used sulfuric acid stream contains less than 20,000 ppm fluorine.

25. The method according to claim 1 or claim 2, wherein the first used sulfuric acid stream contains less than 15,000 ppm fluorine.

26. The method of claim 1 or claim 2, wherein the first used sulfuric acid stream contains less than 10,000 ppm fluorine.

27. The method of claim 1 or claim 2, wherein the first used sulfuric acid stream contains less than 8000 ppm fluorine.

28. The method according to claim 1 or claim 2, wherein the first used sulfuric acid stream contains less than 5000 ppm fluorine.

29. The method according to claim 1 or claim 2, wherein the first used sulfuric acid stream contains less than 4000 ppm fluorine.

30. The method according to claim 1 or claim 2, wherein the first used sulfuric acid stream contains less than 3000 ppm fluorine.

31. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 2000 ppm fluorine.

32. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 1000 ppm fluorine.

33. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 500 ppm fluorine.

34. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 100 ppm fluorine.

35. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 80 ppm fluorine.

36. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 50 ppm fluorine.

37. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 40 ppm fluorine.

38. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 25 ppm fluorine.

39. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 10000 ppm total organic carbon.

40. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 8000 ppm total organic carbon.

41. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 5000 ppm total organic carbon.

42. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 4000 ppm total organic carbon.

43. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 3000 ppm total organic carbon.

44. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 2000 ppm total organic carbon.

45. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 1000 ppm total organic carbon.

46. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 500 ppm total organic carbon.

47. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 250 ppm total organic carbon.

48. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 100 ppm total organic carbon.

49. The process of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 50 ppm total organic carbon.

50. The method of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises less than 25 ppm total organic carbon.

51. The method of claim 1 or claim 2, wherein the first used sulfuric acid stream comprises one or more compounds selected from the group consisting of fluoropropenoic acid, polyfluoropropenoic acid, formic acid, and fluoromethylal, and / or one or more unsaturated fluorine-containing oligomers.

52. The method of claim 1 or claim 2, wherein the method comprises a second drying step comprising contacting the first treated fluid stream with a second source of sulfuric acid to produce a second treated fluid stream comprising the hydrogen (chloro)fluoroolefin and a second used sulfuric acid stream, wherein the second treated fluid stream comprises a lower concentration of water than the fluid stream.

53. The method of claim 52, wherein the source of sulfuric acid comprises aqueous sulfuric acid at a concentration between 78 wt% and 90 wt%.

54. The method of claim 52, wherein the second treated fluid stream comprises less than 500 ppm water.

55. The method of claim 52, wherein the second treated fluid stream comprises less than 250 ppm water.

56. The method of claim 52, wherein the second treated fluid stream comprises less than 100 ppm water.

57. The method of claim 52, wherein the second treated fluid stream comprises less than 10 ppm water.

58. The method of claim 52, wherein the second source of sulfuric acid comprises aqueous sulfuric acid at a concentration between 60 wt% and 98 wt%.

59. The method of claim 52, wherein the second source of sulfuric acid comprises aqueous sulfuric acid at a concentration between 75 wt% and 95 wt%.

60. The method of claim 52, wherein the second source of sulfuric acid comprises aqueous sulfuric acid at a concentration between 78 wt% and 94 wt%.

61. The method of claim 52, wherein the second source of sulfuric acid comprises aqueous sulfuric acid at a concentration between 90 wt% and 94 wt%.

62. The method of claim 52, wherein the first treated fluid stream is contacted with the second source of sulfuric acid at a temperature between 10 °C and 70 °C.

63. The method of claim 52, wherein the first treated fluid stream is contacted with the second source of sulfuric acid at a temperature between 20 °C and 60 °C.

64. The method of claim 52, wherein the first treated fluid stream is contacted with the second source of sulfuric acid at a temperature between 20 °C and 40 °C.

65. The method of claim 52, wherein the first treated fluid stream is contacted with the second source of sulfuric acid at a temperature between 25 °C and 35 °C.

66. The method of claim 52, wherein the first treated fluid stream is contacted with the second source of sulfuric acid at 30 °C.

67. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 20,000 ppm fluorine.

68. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 15,000 ppm fluorine.

69. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 10,000 ppm fluorine.

70. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 8,000 ppm fluorine.

71. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 5,000 ppm fluorine.

72. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 4,000 ppm fluorine.

73. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 3,000 ppm fluorine.

74. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 2,000 ppm fluorine.

75. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 1,000 ppm fluorine.

76. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 500 ppm fluorine.

77. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 100 ppm fluorine.

78. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 80 ppm fluorine.

79. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 50 ppm fluorine.

80. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 40 ppm fluorine.

81. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 25 ppm fluorine.

82. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 10,000 ppm total organic carbon.

83. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 8,000 ppm total organic carbon.

84. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 5,000 ppm total organic carbon.

85. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 4,000 ppm total organic carbon.

86. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 3,000 ppm total organic carbon.

87. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 2,000 ppm total organic carbon.

88. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 1000 ppm total organic carbon.

89. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 500 ppm total organic carbon.

90. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 250 ppm total organic carbon.

91. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 100 ppm total organic carbon.

92. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 50 ppm total organic carbon.

93. The method of claim 52, wherein the second used sulfuric acid stream comprises less than 25 ppm total organic carbon.

94. The method of claim 52, wherein the second used sulfuric acid stream comprises one or more compounds selected from the group consisting of fluoropropenoic acid, polyfluoropropenoic acid, formic acid, and fluoromethylal, and / or one or more unsaturated fluorine-containing oligomers.

95. The method of claim 1 or claim 2, wherein the first treated fluid stream and / or, if produced, the second treated fluid stream comprises the hydrogen (chloro)fluoroolefin at a purity of at least 99 weight %.

96. The method of claim 1 or claim 2, wherein the first treated fluid stream and / or, if produced, the second treated fluid stream comprises the hydrogen (chloro)fluoroolefin at a purity of at least 99.5 weight %.

97. The method of claim 1 or claim 2, wherein the first treated fluid stream and / or, if produced, the second treated fluid stream comprises the hydrogen (chloro)fluoroolefin at a purity of at least 99.9 weight %.

98. The method of claim 1 or claim 2, wherein the first treated fluid stream and / or, if produced, the second treated fluid stream is contacted with an adsorbent material.

99. The method of claim 98, wherein the adsorbent material comprises soda lime and / or one or more molecular sieves.

100. The method of claim 98, wherein the adsorbent material comprises soda lime and / or one or more zeolites having a pore size in the range of 2 to 10 Å.

101. The method of claim 98, wherein the adsorbent material comprises soda lime and / or one or more zeolites having a pore size in the range of 3 to 6 Å.

102. The method of claim 1 or claim 2, wherein the first treated fluid stream and / or, if produced, the second treated fluid stream, optionally having been contacted with an adsorbent material, is subjected to distillation to separate some or all of the remaining components.

103. The method of claim 1, further comprising a prior acid removal step to provide the first fluid stream.

104. The method of claim 1, further comprising a prior acid removal step comprising treating a crude product stream to remove at least a portion of any HF and / or HC1 in the crude product stream to provide the first fluid stream.

105. The method of claim 104, wherein the crude product stream is a product stream of a dehydrohalogenation reaction.

106. The method of claim 104, wherein the crude product stream is a product stream of a dehydrofluorination and / or dehydrochlorination reaction.

107. The method of claim 103, wherein the acid removal step comprises contacting a crude product stream with water to produce a spent aqueous acid stream and a treated product stream, the treated product stream having a lower acid concentration than the crude product stream.

108. The method of claim 107, wherein the aqueous acid comprises HF and / or HC1, the treated product stream having a lower HF and / or HC1 concentration than the crude product stream.

109. The method of claim 2, wherein the acid removal step comprises contacting the crude product stream with an aqueous acid source to produce a spent aqueous acid stream and a treated product stream, the treated product stream having a lower acid concentration than the crude product stream.

110. The method of claim 109, wherein the aqueous acid source comprises a source of aqueous HF and / or HC1, the aqueous acid comprises HF and / or HC1, the treated product stream having a lower HF and / or HC1 concentration than the crude product stream.

111. The method of claim 103, wherein the acid removal step comprises contacting a crude product stream with an aqueous acid source to produce a spent aqueous acid stream and a treated product stream, the treated product stream having a lower acid concentration than the crude product stream.

112. The method of claim 111, wherein the aqueous acid source comprises a source of aqueous HF and / or HC1, the aqueous acid comprises HF and / or HC1, the treated product stream having a lower HF and / or HC1 concentration than the crude product stream.

113. The method of claim 109 or 111, wherein the aqueous acid source comprises aqueous HF at a concentration between 30 wt% and 60 wt%.

114. The method of claim 109 or 111, wherein the aqueous acid source comprises aqueous HF at a concentration between 40 wt% and 60 wt%.

115. The method of claim 2, wherein the treated product stream is provided directly to the first drying stage.

116. The method of claim 2, wherein the treated product stream is provided directly to the first drying stage in the form of the first fluid stream.

117. The method of claim 2, wherein the treated product stream is subjected to one or more further treatment steps prior to being provided to the first drying stage.

118. The method of claim 113, wherein the treated product stream is subjected to a second acid removal step.

119. The method of claim 113, wherein the treated product stream is subjected to a second acid removal step comprising contacting the treated product stream with an aqueous base solution to produce a second treated product stream and a spent aqueous base solution stream, the second treated product stream having a lower acid concentration than the treated product stream.

120. The method of claim 117, wherein the treated product stream is subjected to a second acid removal step.

121. The method of claim 117, wherein the treated product stream is subjected to a second acid removal step comprising contacting the treated product stream with an aqueous base solution to produce a second treated product stream and a spent aqueous base solution stream, the second treated product stream having a lower acid concentration than the treated product stream.

122. The method of claim 119 or 121, wherein the aqueous base solution source comprises an aqueous caustic solution.

123. The method of claim 119 or 121, wherein the aqueous base solution source comprises aqueous NaOH or KOH.

124. The method of claim 119 or 121, wherein the aqueous base solution source comprises an aqueous caustic solution at a concentration of less than 20 wt.%.

125. The method of claim 119 or 121, wherein the aqueous base solution source comprises an aqueous caustic solution at a concentration of less than 10 wt.%.

126. The method of claim 119 or 121, wherein the aqueous base solution source comprises an aqueous caustic solution at a concentration of less than 5 wt.%.

127. The method of claim 119 or 121, wherein the second treated product stream is provided directly to the first drying stage.

128. The method of claim 119 or 121, wherein the second treated product stream is provided directly to the first drying stage in the form of the first fluid stream.

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