Method for removing sulfur dioxide (SO2) from trifluoroacetyl chloride (TFAC)

Abstract

This invention discloses a method for removing impurities such as sulfur dioxide (SO2) from trifluoroacetyl chloride (TFAC) by distillation, adsorption, or a combination thereof, and / or by forming an azeotropic or azeotropic composition comprising effective amounts of sulfur dioxide (SO2) and trifluoroacetyl chloride (TFAC). The thus purified trifluoroacetyl chloride (TFAC) can then be used to prepare trifluoroiodomethane (CF3I). Azeotropic and azeotropic compositions of sulfur dioxide (SO2) and trifluoroacetyl chloride (TFAC) are also disclosed.

Description

[0001] This application is a divisional application of the invention application with application number "202180062446.5" entitled "Method for removing sulfur dioxide (SO2) from trifluoroacetyl chloride (TFAC)".

[0002] Cross-reference to related applications This application claims priority to U.S. Patent Application No. 17 / 466,704, filed September 3, 2021, which claims the benefit of U.S. Provisional Application No. 63 / 222,801, filed July 16, 2021, and U.S. Provisional Application No. 63 / 077,352, filed September 11, 2020, all of which are incorporated herein by reference in their entirety. Technical Field

[0003] This disclosure relates to the removal of sulfur dioxide (SO2) as an impurity from trifluoroacetyl chloride (TFAC). This disclosure further relates to azeotropic and azeotropic compositions of sulfur dioxide (SO2) and trifluoroacetyl chloride (TFAC). Background Technology

[0004] Trifluoroiodomethane (CF3I), also known as perfluoromethyl iodide, trifluoromethyl iodide, or iodotrifluoromethane, is a commercially useful compound that can be industrially produced from trifluoroacetyl chloride (CF3COCl, TFAC). Trifluoroiodomethane is an environmentally acceptable compound with low global warming and ozone depletion potentials. It can serve as a substitute for more environmentally harmful substances.

[0005] Methods for preparing trifluoroiodomethane are known. In one method, trifluoroiodomethane is produced from trifluoroacetyl chloride in two steps.

[0006] The method includes a first step of preparing trifluoroacetyl iodine, as shown in the following reaction formula 1.

[0007] CF3COCl + HI → CF3COI + HCl (1) The method includes a second step of preparing trifluoroiodomethane via the reaction shown in Formula 2.

[0008] CF3COI→CF3I+CO (2) In another method, a one-step process is used to prepare trifluoroiodomethane from trifluoroacetyl chloride, as shown in the following reaction formula 3.

[0009] CF3COCl + HI → CF3I + CO + HCl (3) Advantageously, the aforementioned method provides higher CF3I selectivity than other methods.

[0010] However, it has been found that the presence of sulfur dioxide (SO2), an impurity sometimes found in trifluoroacetyl chloride (TFAC), may have a negative impact on the catalysts used in these methods. Summary of the Invention

[0011] This disclosure relates to the removal of impurities from trifluoroacetyl chloride (TFAC), and more specifically, to the removal of sulfur dioxide (SO2) from trifluoroacetyl chloride (TFAC) by distillation, adsorption, or a combination thereof, and / or by forming an azeotropic or azeotropic composition comprising effective amounts of sulfur dioxide (SO2) and trifluoroacetyl chloride (TFAC), the azeotropic or azeotropic composition being described as a lowest boiling point (or highest pressure) azeotrope. Distillation and adsorption can be used alone or in combination to reduce the amount of sulfur dioxide (SO2) in trifluoroacetyl chloride (TFAC) to a desired level. The trifluoroacetyl chloride (TFAC) thus purified can then be used to prepare trifluoroacetyl iodide (CF3COI) and / or trifluoroiodomethane (CF3I).

[0012] This disclosure also relates to a composition comprising an azeotrope or azeotropic-like composition, which is substantially composed of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2).

[0013] The boiling point of this azeotrope or azeotropic-like composition is about 10.0°C ± 3°C at a pressure of about 45 psia ± 0.3 psia.

[0014] The azeotropic or azeotropic composition may comprise, substantially consist of, or consist of: about 25% to about 99% by weight of trifluoroacetyl chloride (TFAC) and about 1% to about 75% by weight of sulfur dioxide (SO2), about 48% to about 90% by weight of trifluoroacetyl chloride (TFAC) and about 10% to about 52% by weight of sulfur dioxide (SO2), or about 68% to about 78% by weight of trifluoroacetyl chloride (TFAC) and about 22% to about 32% by weight of sulfur dioxide (SO2).

[0015] A method for forming an azeotropic or azeotropic composition includes the step of combining trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) to form an azeotropic or azeotropic composition substantially composed of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2), the azeotropic or azeotropic composition having a boiling point of about 10.0 °C ± 3 °C at a pressure of about 45 psia ± 0.3 psia.

[0016] This disclosure also relates to a method for removing sulfur dioxide (SO2) from trifluoroacetyl chloride (TFAC), the method comprising at least one of distillation, adsorption, or a combination thereof. Distillation and adsorption can be performed alone or in combination to achieve a desired level of sulfur dioxide (SO2) in the trifluoroacetyl chloride (TFAC). For example, distillation can be performed alone, or adsorption can be performed alone. Adsorption can be performed after distillation. Alternatively, distillation can be performed after adsorption. In another alternative, multiple distillation and adsorption steps can be combined.

[0017] This disclosure further relates to a method for removing sulfur dioxide (SO2) from trifluoroacetyl chloride (TFAC) upstream of, downstream of, or in combination thereof, the reaction of trifluoroacetyl chloride (TFAC) with hydrogen iodide (HI). Sulfur dioxide (SO2) can be removed from trifluoroacetyl chloride (TFAC) by distillation, adsorption, or a combination thereof. For example, distillation can be performed alone, or adsorption can be performed alone. Adsorption can be performed after distillation. Alternatively, distillation can be performed after adsorption. In another alternative, multiple distillation and adsorption steps can be combined.

[0018] This application discloses the following technical solutions: Option 1. A composition comprising an azeotrope or azeotropic-like composition, said azeotrope or azeotropic-like composition being substantially composed of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2).

[0019] Option 2. The composition according to Option 1, wherein the azeotropic or azeotropic composition has a boiling point of about 10.0°C ± 3°C at a pressure of about 45 psia ± 0.3 psia.

[0020] Option 3. A method for removing sulfur dioxide (SO2) from trifluoroacetyl chloride (TFAC), said method comprising at least one of distillation, adsorption, or a combination thereof.

[0021] Option 4. According to the method described in Option 3, the method further includes the following steps: The feed stream is fed to the distillation column, the feed stream containing trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2). Collect the distillate from the distillation column, the distillate comprising trifluoroacetyl chloride and sulfur dioxide (SO2); and The bottom product from the distillation column is collected, and the bottom product consists essentially of trifluoroacetyl chloride (TFAC).

[0022] Option 5. According to the method described in Option 3, the method further includes the following steps: The feed stream is fed to the distillation column, the feed stream containing trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2). An azeotrope or azeotropic-like composition is formed, which is essentially composed of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); Collect the distillate from the distillation column, the distillate comprising the azeotrope or azeotropic composition; and The bottom product from the distillation column is collected, and the bottom product consists essentially of trifluoroacetyl chloride (TFAC).

[0023] Option 6. The method according to Option 3, further comprising the following steps: The feed stream is fed to the distillation column, the feed stream containing trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2). An azeotrope or azeotropic-like composition is formed, which is essentially composed of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); Collect the distillate from the distillation column, the distillate comprising the azeotrope or azeotropic composition; Collect the bottom product from the distillation column; Contact the bottom product from the distillation column with the solid adsorbent; and Collect the product stream, which consists essentially of trifluoroacetyl chloride (TFAC).

[0024] Option 7. The method according to Option 3, further comprising the following steps: The feed stream is fed to the distillation column, the feed stream containing trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2). An azeotrope or azeotropic-like composition is formed, which is essentially composed of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); Collect the bottom product from the distillation column; Collect the distillate from the column, the distillate comprising the azeotrope or azeotropic composition; Contact the distillate with a solid adsorbent; and Collect the product stream, which consists essentially of trifluoroacetyl chloride (TFAC).

[0025] Option 8. The method according to Option 3, further comprising the following steps: The feed stream is fed to the distillation column, the feed stream containing trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2). An azeotrope or azeotropic-like composition is formed, which is essentially composed of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); Collect the bottom product from the distillation column; The bottom product from the distillation column is brought into contact with the first solid adsorbent; Collect the product stream, which consists essentially of trifluoroacetyl chloride (TFAC); Collect the distillate from the column, the distillate comprising the azeotrope or azeotropic composition; The distillate from the distillation column is contacted with a second solid adsorbent; and Collect the product stream, which consists essentially of trifluoroacetyl chloride (TFAC).

[0026] Option 9. The method according to Option 3, further comprising the following steps: The feed stream is brought into contact with a first solid adsorbent, the feed stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2). Collect the product stream, which contains trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2). The product stream containing trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) is fed to a distillation column; An azeotrope or azeotropic-like composition is formed, which is essentially composed of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); Collect the bottom product from the distillation column; The product from the bottom of the distillation column is brought into contact with a second solid adsorbent; Collect the product stream, which consists essentially of trifluoroacetyl chloride (TFAC); Collect the distillate from the column, the distillate comprising the azeotrope or azeotropic composition; The distillate from the distillation column is contacted with a third solid adsorbent; and The product stream is collected from the third solid adsorbent, and the product stream consists essentially of trifluoroacetyl chloride (TFAC).

[0027] Option 10. The method according to Option 9, wherein the bottom product contains about 100 ppm or less of sulfur dioxide (SO2).

[0028] Option 11. The method according to Option 3, further comprising the following steps: A feed stream containing a mixture of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) is contacted with a solid adsorbent or a mixture of two or more solid adsorbents; and Collect the product stream, which consists essentially of trifluoroacetyl chloride (TFAC).

[0029] Scheme 12. A method for removing sulfur dioxide (SO2) from a mixture containing trifluoroacetyl iodine (TFAI), said method comprising at least one of distillation, adsorption, or a combination thereof.

[0030] Option 13. The method according to Option 12, wherein the method comprises: A feed stream containing trifluoroacetyl iodine (TFAI), hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) is fed to the first distillation column to provide the first column top product and the first column bottom product. The overhead product is fed to a second distillation column to provide a second overhead product and a second bottom product; and The bottom product of the second column is fed to an adsorption column to provide a product stream containing trifluoroacetyl chloride (TFAC) and hydrogen iodide (HI).

[0031] Option 14. The method according to Option 12, wherein the feed stream comprising trifluoroacetyl iodine (TFAI), hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2) and hydrogen iodide (HI) is obtained by feeding trifluoroacetyl chloride (TFAC) containing 250 ppm or less of sulfur dioxide (SO2).

[0032] Option 15. The method according to Option 12, wherein the method comprises: The feed stream containing trifluoroacetyl iodine (TFAI), hydrogen chloride (HCl), hydrogen iodide (HI), trifluoroacetyl chloride (TFAC), and sulfur dioxide (SO2) is fed to the first distillation column to provide the first column top product and the first column bottom product; The first bottom product is fed to a second distillation column to provide a second top product and a second bottom product. The second bottom product is fed to a third distillation column to provide a third top product containing trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) and a third bottom product containing trifluoroacetyl iodide (TFAI). Attached Figure Description

[0033] Figure 1 An exemplary method for purifying trifluoroacetyl chloride (TFAC) by distillation is shown.

[0034] Figure 2An exemplary method for purifying trifluoroacetyl chloride (TFAC) by adsorbing impurities is shown.

[0035] Figure 3 An exemplary method for purifying trifluoroacetyl chloride (TFAC) by a combination of distillation and adsorption is shown.

[0036] Figure 4 Another exemplary method for purifying trifluoroacetyl chloride (TFAC) by a combination of distillation and adsorption is shown.

[0037] Figure 5 Another exemplary method for purifying trifluoroacetyl chloride (TFAC) by a combination of distillation and adsorption is shown.

[0038] Figure 6 Another exemplary method for purifying trifluoroacetyl chloride (TFAC) by a combination of distillation and adsorption is shown.

[0039] Figure 7 The pressure (psia) of trifluoroacetyl chloride (TFAC) concentration is shown in the PTx study of TFAC and SO2 at 10°C corresponding to Example 1.

[0040] Figure 8 The SO2 concentration in TFAC over time is shown, corresponding to Example 3.

[0041] Figure 9 The results of thermogravimetric analysis performed on used MSC-3K 172 carbon molecular sieves, corresponding to Example 5, are shown.

[0042] Figure 10 The results of mass spectrometry analysis performed on a used MSC-3K 172 carbon molecular sieve, corresponding to Example 5, are shown.

[0043] Figure 11 A schematic diagram of a system for removing sulfur dioxide (SO2) corresponding to Examples 11 to 17 is shown.

[0044] Figure 12 A schematic diagram of a system for removing sulfur dioxide (SO2) corresponding to Example 18 is shown. Detailed Implementation

[0045] This disclosure relates to the removal of impurities from trifluoroacetyl chloride (TFAC), and more specifically, to the removal of sulfur dioxide (SO2) from trifluoroacetyl chloride (TFAC) by distillation, adsorption or a combination thereof, and / or by forming an azeotropic or azeotropic composition comprising effective amounts of sulfur dioxide (SO2) and trifluoroacetyl chloride (TFAC).

[0046] It has been found that sulfur dioxide (SO2) can interfere with the catalytic processes for the preparation of trifluoroiodomethane (CF3I) in the two-step and one-step methods described above, wherein trifluoroacetyl chloride (TFAC) purified by the methods disclosed herein can provide an effective starting material for the production of trifluoroiodomethane (CF3I).

[0047] 1. Remove sulfur dioxide (SO2) before the formation of trifluoroacetyl iodide (TFAI). One method for purifying trifluoroacetyl chloride (TFAC) involves forming an azeotrope or azeotropic-like composition with sulfur dioxide (SO2). This azeotrope or azeotropic-like composition can be removed from a large quantity of trifluoroacetyl chloride (TFAC) via distillation. Another method for removing sulfur dioxide (SO2) from trifluoroacetyl chloride (TFAC) involves contacting a mixture of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) with a solid adsorbent or a mixture of two or more solid adsorbents to remove sulfur dioxide (SO2) from the mixture. Yet another method for purifying trifluoroacetyl chloride (TFAC) includes a combination of these methods. Contacting the mixture of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) with a solid adsorbent can be performed before or after distillation. Multiple adsorption steps can be used with or without distillation.

[0048] It has been discovered that trifluoroacetyl chloride (TFAC) forms homogeneous, lowest-boiling-point azeotropic and azeotropic compositions or mixtures with sulfur dioxide (SO2), and this disclosure provides homogeneous azeotropic or azeotropic compositions comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2). The azeotropic or azeotropic composition may consist substantially of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2), or the azeotropic or azeotropic composition may consist of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2).

[0049] An azeotropic composition is a unique combination of two or more components. Azeotropic compositions can be characterized in various ways. For example, at a given pressure, an azeotropic composition boils at a constant characteristic temperature, either above the higher-boiling-point component (maximum boiling-point azeotrope) or below the lower-boiling-point component (minimum boiling-point azeotrope). At this characteristic temperature, the same composition will exist in both gas and liquid phases. Azeotropic compositions do not fractionate upon boiling or evaporation. Therefore, the components of an azeotropic composition cannot separate during phase transition.

[0050] Alternatively, an azeotropic composition can be characterized as a composition that boils at a characteristic vapor pressure at a given temperature. The vapor pressure may be lower than that of the component with the lower vapor pressure (minimum pressure azeotrope), or the vapor pressure may be higher than that of the component with the higher vapor pressure (maximum pressure azeotrope). The minimum pressure azeotrope may be called the highest boiling point azeotrope, or vice versa, and the maximum pressure azeotrope may be called the lowest boiling point azeotrope, or vice versa.

[0051] The behavior of azeotropic compositions contrasts with that of non-azeotropic compositions, in which the liquid composition changes considerably during boiling or evaporation.

[0052] However, those skilled in the art will understand that the composition and boiling point of an azeotropic composition will vary to some extent under different pressures. Therefore, an azeotropic composition may have a varying composition depending on temperature and / or pressure. Thus, those skilled in the art will understand that a range of compositions can be used instead of a fixed composition to define an azeotropic composition. Furthermore, an azeotrope can be defined based on the exact weight percentage of each component of the composition, characterized by a fixed boiling point at a specified pressure.

[0053] An "azeotropic-like" composition is a composition of two or more components that behave substantially the same as an azeotropic composition. Therefore, for the purposes of this disclosure, an azeotropic-like composition is a combination of two or more different components that, when in liquid form at a given pressure, will boil at a substantially constant temperature and will provide a vapor composition substantially the same as that of the liquid undergoing boiling.

[0054] Azeotropic or azeotropic-like compositions can be identified using a variety of different methods.

[0055] Static gas-liquid equilibrium methods are a class of experimental techniques that can be used to identify the presence of azeotropic and azeotropic-like compositions. One such technique, known as the PTx method, collects measurements of the total saturation pressure ("P") exerted by a mixture of a known composition ("x") at a fixed temperature ("T") and unit volume. (Walas, Phase Equilibria in Chemical Engineering, Butterworth-Heinemann, 1985, p. 537). Using data collected from PTx experiments and the pure component properties of the mixture's components, the thermodynamic properties of the mixture can be accurately characterized by fitting the interaction parameters of the components to a well-defined thermodynamic equation; one such equation is the Helmholtz Energy Equation of State (HEOS) described by EW Lemmon et al. (Generalized Model for the Thermodynamic Properties of Mixtures, International Journal of Thermophysics, Vol. 20, 1999, pp. 825-835).

[0056] The presence of azeotropic compounds and their corresponding compositions can be observed by plotting saturated pressure measurements from PTx data against saturated pressures described as a function of composition using HEOS. For a given temperature (isotherm), the presence of an azeotropic composition is determined by observing that the maximum or minimum total pressure is greater than or less than the pure saturated pressure of any individual component.

[0057] Technicians will know that azeotropic or azeotropic compositions can be identified by comparing the change in the boiling point of the composition relative to the boiling point of the first component when the second component is added. Therefore, to measure the change in boiling point, it is not necessary to calibrate the system to the reported boiling point of a specific component.

[0058] This disclosure provides an azeotropic or azeotropic-like composition comprising an effective amount of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) that forms the azeotropic or azeotropic-like composition. As used herein, the term "effective amount" is the amount of each component that, when combined with other components, results in the formation of an azeotropic or azeotropic-like mixture.

[0059] The azeotropic or azeotropic composition of the present invention may consist essentially of a combination of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2), or a combination of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2).

[0060] As used herein, with respect to the components of an azeotropic or azeotropic-like composition or mixture, the term "consistently of..." means that the composition contains an indicated component in an azeotropic or azeotropic-like ratio and may contain additional components provided that the additional components do not form a new azeotropic or azeotropic-like system. For example, an azeotropic mixture consisting essentially of two compounds is one of those that form a binary azeotrope, which may optionally contain one or more additional components provided that the additional components do not render the mixture non-azeotropic and do not form an azeotrope with any one or both compounds (e.g., do not form a ternary or higher-order azeotrope).

[0061] An azeotropic or azeotropic composition having a boiling point of about 10.0 °C ± 3 °C at a pressure of about 45 psia ± 0.3 psia may comprise, substantially consist of or be composed of: about 25 wt% to about 99 wt% of trifluoroacetyl chloride (TFAC) and about 1 wt% to about 75 wt% of sulfur dioxide (SO2); about 48 wt% to about 90 wt% of trifluoroacetyl chloride (TFAC) and about 10 wt% to about 52 wt% of sulfur dioxide (SO2); or about 68 wt% to about 78 wt% of trifluoroacetyl chloride (TFAC) and about 22 wt% to about 32 wt% of sulfur dioxide (SO2).

[0062] Alternatively, an azeotropic or azeotropic composition having a boiling point of about 10.0 °C ± 3 °C at a pressure of about 45 psia ± 0.3 psia may comprise, substantially consist of or be composed of: about 24.5 wt% to about 94.9 wt% of trifluoroacetyl chloride (TFAC) and about 5.1 wt% to about 75.5 wt% of sulfur dioxide (SO2), or about 47.9 wt% to about 89.7 wt% of trifluoroacetyl chloride (TFAC) and about 10.3 wt% to about 52.1 wt% of sulfur dioxide (SO2).

[0063] This disclosure also provides a composition comprising an azeotropic or azeotropic composition. For example, a composition is provided comprising as low as 1 ppm of an azeotropic or azeotropic composition, 10 ppm of an azeotropic or azeotropic composition, 25 ppm of an azeotropic or azeotropic composition, or up to 50 ppm of an azeotropic or azeotropic composition, 100 ppm of an azeotropic or azeotropic composition, 1000 ppm of an azeotropic or azeotropic composition, 1% by weight of an azeotropic or azeotropic composition, 5% by weight or more of an azeotropic or azeotropic composition.

[0064] After separating the azeotropic or azeotropic composition from another composition, the azeotropic composition may contain at least 10% by weight of the azeotropic or azeotropic composition, or at least about 20% by weight of the azeotropic or azeotropic composition, or at least about 50% by weight of the azeotropic or azeotropic composition, or at least about 70% by weight of the azeotropic or azeotropic composition, or at least about 90% by weight of the azeotropic or azeotropic composition.

[0065] The azeotropic or azeotropic compositions disclosed herein, comprising, substantially consisting of, or consisting of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2), can be used to separate impurities, including sulfur dioxide (SO2), from trifluoroacetyl chloride (TFAC).

[0066] Specifically, an azeotropic or azeotropic composition comprising, substantially composed of, or composed of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) can be formed from a composition comprising one or both of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2), optionally together with one or more other compounds (such as other impurities) besides trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2). After the formation of the azeotropic or azeotropic composition, the azeotropic or azeotropic composition can be separated from the other compounds by suitable methods such as distillation or fractionation.

[0067] This disclosure provides a method for separating sulfur dioxide (SO2) as an impurity from a crude composition of trifluoroacetyl chloride (TFAC), the crude composition containing sulfur dioxide (SO2) as an impurity and any additional impurities (if present). Sulfur dioxide (SO2) may be present in the crude composition of trifluoroacetyl chloride (TFAC) in amounts of about 5 ppm or greater, about 50 ppm or greater, about 100 ppm or greater, about 500 ppm or greater, about 1000 ppm or greater, about 2000 ppm or greater, about 3000 ppm or greater, or about 5000 ppm or greater.

[0068] A method includes the following steps: providing crude trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2) as an impurity, and any other impurities (if present); feeding the crude trifluoroacetyl chloride (TFAC) to a distillation column; collecting a distillate from the distillation column containing sulfur dioxide (SO2), or an azeotrope or azeotropic mixture of sulfur dioxide (SO2) and trifluoroacetyl chloride (TFAC); and collecting a bottom product from the distillation column, the bottom product consisting essentially of trifluoroacetyl chloride (TFAC).

[0069] Another method includes the following steps: providing a crude composition comprising trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2) as an impurity, and any other impurities (if present); subjecting the crude composition to conditions that effectively form an azeotrope or azeotropic-like composition consisting essentially of or in effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); and separating the azeotrope or azeotropic-like composition from the crude composition by a separation technique such as, for example, distillation or fractionation. The azeotrope or azeotropic-like composition may then be subjected to further separation or purification steps to obtain purified trifluoroacetyl chloride (TFAC).

[0070] Another method for separating trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) from a feed stream containing trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) is shown in Figure 1 This method may include forming an azeotrope or azeotropic-like composition, or it may not include forming an azeotrope or azeotropic-like composition. The method includes an initial step of feeding a feed stream containing trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) into distillation column 10. Bottom product 16 may be passed through reboiler 18, and a portion of the bottom product is recycled back to column 10, while another portion is collected as bottom product stream 20. Bottom product stream 20 consists essentially of trifluoroacetyl chloride (TFAC). Overhead stream 12 is passed through condenser 14, and a portion of the overhead stream is refluxed back into column 10, while the remainder is collected as overhead product stream. Overhead product stream contains an azeotrope or azeotropic-like composition, which consists essentially of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2). The product stream may further contain an excess of trifluoroacetyl chloride (TFAC). The tower can operate under a variety of temperature and pressure conditions to achieve the desired separation.

[0071] The bottom product stream 20 may contain sulfur dioxide (SO2) in amounts of about 100 ppm or less, about 50 ppm or less, about 10 ppm or less, or about 1 ppm or less.

[0072] In another example, this disclosure provides a method for separating sulfur dioxide (SO2) as an impurity from a crude composition of trifluoroacetyl chloride (TFAC), the crude composition comprising sulfur dioxide (SO2) as an impurity and at least one additional impurity, the method comprising the steps of: providing a composition of crude trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2) as an impurity and at least one additional impurity; and contacting the crude composition with a solid adsorbent.

[0073] Suitable adsorbents may include molecular sieves, such as 3Å molecular sieves available from Acros Organics (and also from Honeywell UOP); 4Å and XH-9 molecular sieves available from Honeywell UOP; 10Å molecular sieves available from Grace Davison; and carbon molecular sieves, such as JEChem MSC-3K 172 carbon molecular sieve available from Osaka Gas Chemicals; activated alumina, such as SAS40 1 / 8" alumina available from BASF; zeolite ammonium powder, such as CBV5524G CY available from Zeolyst International; and activated carbon, such as NORIT ROX 0.8 activated carbon available from Cabot.

[0074] In this method, it can be achieved through, for example... Figure 2 The adsorption process shown removes sulfur dioxide (SO2) from trifluoroacetyl chloride (TFAC). SO2-containing trifluoroacetyl chloride (TFAC) is loaded into a vessel (such as a cylinder or tank) 22. A suction pipe 24 is provided at the liquid outlet port 26 of the trifluoroacetyl chloride (TFAC) vessel 22. The SO2-containing trifluoroacetyl chloride (TFAC) stream flows through the suction pipe 24, is conveyed through line 32, and delivered to the inlet 34 of the trifluoroacetyl chloride (TFAC) recirculation pump 36. The outlet line 38 of the trifluoroacetyl chloride (TFAC) recirculation pump 36 is connected to a valve 40, which conveys the SO2-containing trifluoroacetyl chloride (TFAC) stream 42 to an adsorption tower 44. The outlet 46 of the adsorption tower 44 is connected to the vapor port 56 of the vessel 22. A nitrogen purging port 70 and a pressure gauge 72 are connected to the recirculation pump outlet line 38. A portion of the stream 32 can be diverted through valve 58 to line 60, ultimately passing through the sampling port 66. Vacuum / nitrogen port 74 is also connected to line 60 via valve 62 and line 64.

[0075] After a pressure check of the system, trifluoroacetyl chloride (TFAC) containing SO2 is pumped from vessel 22 via recirculation pump 36 through suction pipe 24 and liquid port 26, passed through adsorption tower 44, and returned to trifluoroacetyl chloride (TFAC) vessel 22 via vapor port 56. Periodically, samples can be taken from sampling port 66 to analyze SO2 concentration by thermal conductivity detector-gas chromatography (TCD-GC). After a certain period, when the SO2 concentration reaches a certain level or the adsorbent is saturated with SO2, recirculation pump 36 is stopped and the trifluoroacetyl chloride (TFAC) cylinder valve is closed to contain the trifluoroacetyl chloride (TFAC) in vessel 22. Residual trifluoroacetyl chloride (TFAC) in the system is discharged into another container (not shown), or through valve 48 into a KOH scrubber (not shown) connected to discharge port 50, and the system is purged with nitrogen through port 74. The adsorption tower 44 is disconnected from the system, and the used adsorbent is discharged from the tower for regeneration. Preferably, a second adsorption tower (not shown) connected in parallel with the adsorption tower 44 can be used to achieve continuous adsorption operation.

[0076] On a larger scale, the SO2-containing TFAC feed stream can be contacted with an adsorbent. This contact can be mediated by a pump to move the feed stream through the packed bed via a pressure differential. Once contacted with the adsorbent, the feed stream can be recirculated from the bed back to the holding vessel until the desired purity is achieved.

[0077] The recycling process (or adsorption process) can be operated at temperatures of about -30°C or greater, about -20°C or greater, about -10°C or greater, about 0°C or greater, about 10°C or greater, about 20°C or less, about 30°C or less, about 40°C or less, about 50°C or less, about 60°C or less, about 70°C or less, about 80°C or less, or about 90°C or less, preferably from 0°C to 60°C, and even more preferably from 20°C to 40°C.

[0078] The recirculation process (or adsorption process) can be operated at pressures of about 0 psig or greater, about 50 psig or greater, about 100 psig or greater, about 150 psig or greater, about 200 psig or greater, about 250 psig or greater, about 300 psig or less, about 350 psig or less, about 400 psig or less, about 450 psig or less, or about 500 psig or less, preferably 10 psig to 200 psig, and even more preferably 40 psig to 100 psig.

[0079] The space velocity (WHV) of SO2-containing trifluoroacetyl chloride (TFAC) flowing through the adsorption column is not critical and can vary over a wide range. Higher WHV conditions may require longer recirculation times. The optimal recirculation time can be determined experimentally until the desired SO2 level in the trifluoroacetyl chloride (TFAC) is achieved.

[0080] When saturation is reached, the solid adsorbent will no longer function. The used solid adsorbent can optionally be regenerated for reuse. Regeneration can be accomplished by heating the used solid adsorbent to an elevated temperature under vacuum or in the presence of a purge gas (such as nitrogen) to desorb the adsorbed substances, which may include sulfur dioxide (SO2). The desorption temperature range can be from 100°C to 600°C, preferably from 150°C to 500°C, and more preferably from 300°C to 400°C.

[0081] The purified trifluoroacetyl chloride (TFAC) obtained by adsorption from this method may contain sulfur dioxide (SO2) in amounts of about 0.1% by weight or less, about 0.05% by weight or less, about 0.03% by weight or less, about 0.02% by weight or less, about 0.001% by weight or less, or about 0% by weight.

[0082] The percentage of sulfur dioxide (SO2) removed by adsorption from trifluoroacetyl chloride (TFAC) can be about 5% or more, about 10% or more, about 20% or more, about 50% or more, about 60% or more, about 70% or more, about 80% or more, about 90% or more, or about 100%.

[0083] As another alternative, Figure 1 and Figure 2 The methods shown can be combined. For example, as Figure 3 As shown, a feed stream containing trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) can be fed to distillation column 76. The bottom product 82 can be passed through reboiler 84, with a portion recycled back to distillation column 76 and another portion collected as bottom product stream 86. The bottom product stream 86 can be fed to adsorption column 88 to produce a product stream consisting essentially of purified trifluoroacetyl chloride (TFAC). The overhead stream 78 can pass through condenser 80, with a portion refluxed back to distillation column 76 and another portion purged as a light stream containing an azeotrope or azeotropic-like composition consisting essentially of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2), and optionally containing an excess of trifluoroacetyl chloride (TFAC). Adsorption column 88 can be operated using either a once-through method or a recirculation method.

[0084] Figure 4 It shows Figure 1 and Figure 2 Different alternatives to the combined method. A feed stream containing trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) can be fed to distillation column 90. The bottom product 102 can be passed through reboiler 104, with a portion recycled back to distillation column 90 and another portion collected as a bottom product stream containing purified trifluoroacetyl chloride (TFAC). The top product stream 92 is passed through condenser 94, with a portion refluxed back to distillation column 90 and another portion collected as a top product stream 96 containing an azeotrope or azeotropic-like composition consisting essentially of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2), and optionally containing an excess of trifluoroacetyl chloride (TFAC). This top product stream can be fed to adsorption column 98 to produce product stream 100 consisting essentially of purified trifluoroacetyl chloride (TFAC). Adsorption column 98 can be operated using a straight-through method or a recirculation method.

[0085] Figure 5 Another alternative for the combined method is shown. A feed stream containing trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) can be fed to distillation column 106. The bottom product 118 can be passed through reboiler 120, with a portion recycled back to distillation column 106 and another portion fed to adsorption column 122 to produce a product stream consisting essentially of purified trifluoroacetyl chloride (TFAC). The top product stream 108 is passed through condenser 110, with a portion refluxed back to distillation column 106 and another portion collected as product stream 112, which is an azeotrope or azeotropic-like composition consisting essentially of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2), and optionally containing an excess of trifluoroacetyl chloride (TFAC). This top product stream can be fed to adsorption column 114 to produce product stream 116 consisting essentially of purified trifluoroacetyl chloride (TFAC). Adsorption towers 122 and 114 can be operated using either a straight-through method or a recirculation method.

[0086] Figure 6Another alternative for the combined method is shown. A feed stream containing trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) can be fed to adsorption column 124 to produce a purified feed stream 126. This purified feed stream 126 can be fed to distillation column 128. The bottom product 140 can be passed through reboiler 142, with a portion recycled back to distillation column 128 and another portion fed to adsorption column 144 to produce a product stream consisting essentially of purified trifluoroacetyl chloride (TFAC). The overhead stream 130 is passed through condenser 132, with a portion refluxed back to distillation column 128 and another portion collected as product stream 134. This product stream is an azeotrope or azeotropic-like composition consisting essentially of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2), and optionally containing an excess of trifluoroacetyl chloride (TFAC). This overhead product stream can be fed to adsorption column 136 to produce product stream 138 consisting essentially of purified trifluoroacetyl chloride (TFAC). Adsorption columns 144 and 136 can be operated using either a straight-through method or a recirculation method. Figure 6 The location of the first adsorption tower shown can be replicated by any of the other methods described above.

[0087] 2. Synthesis of Trifluoroacetyl iodide (TFAI) As shown in reaction formula 1, trifluoroacetyl chloride (TFAC) can react with hydrogen iodide (HI) to synthesize trifluoroacetyl iodide (TFAI).

[0088] CF3COCl + HI → CF3COI + HCl This method can be a gas-phase method, which includes providing a reaction stream containing hydrogen iodide and at least one trifluoroacetyl halide selected from trifluoroacetyl chloride (TFAC), trifluoroacetyl fluoride (TFAF), trifluoroacetyl bromide (TFAB), and combinations thereof, to produce an intermediate product stream containing trifluoroacetyl iodide (TFAI).

[0089] This method can be carried out in a reactor, such as a heated tube reactor, which comprises tubes made of metals such as stainless steel, nickel, and / or nickel alloys such as nickel-chromium alloys, nickel-molybdenum alloys, nickel-chromium-molybdenum alloys, or nickel-copper alloys. The tubes within the reactor can be heated, or the feed material can be preheated before entering the reactor. The reactor can be any type of packed bed reactor.

[0090] Hydrogen iodide and trifluoroacetyl iodide in the reactant stream react in the presence of a first catalyst contained within a first reactor. The catalyst may comprise activated carbon, mesophase carbon, stainless steel, nickel, nickel-chromium alloys, nickel-chromium-molybdenum alloys, nickel-copper alloys, copper, alumina, platinum, palladium, or carbides (such as metallic carbides (such as iron carbide, molybdenum carbide, and nickel carbide) and non-metallic carbides (such as silicon carbide)) or combinations thereof. The catalyst may be in the form of mesh, granules, or spheres contained within the reactor.

[0091] The reaction temperature can be as low as about 0°C or higher, about 25°C or higher, about 35°C or higher, about 40°C or higher, about 50°C or higher, or about 60°C or lower, about 90°C or lower, about 120°C or lower, about 150°C or lower, or about 200°C or lower, or about 250°C or lower, or any value covered by these endpoints.

[0092] In this example of the method, fresh hydrogen iodide (HI) and trifluoroacetyl chloride (TFAC) are combined with a recycled mixture containing HI and TFAC recovered from the distillation column assembly. The TFAC / HI molar ratio of this combination is provided with an excess of TFAC to obtain a high conversion of the more expensive HI, but equimolar amounts or excess HI can be used.

[0093] The TFAC / HI ratio can be about 1:10 or less, about 1:5 or less, about 1:2 or less, about 1:1 or greater, about 2:1 or greater, about 3:1 or greater, about 4:1 or greater, about 5:1 or greater, about 6:1 or greater, about 7:1 or greater, about 8:1 or greater, about 9:1 or greater, about 10:1 or greater, or any value encompassed by these endpoints. Preferably, the TFAC / HI ratio is from 1:2 to 2:1. More preferably, the TFAC / HI ratio is from 1:1 to 2:1.

[0094] The pressure can be approximately 0 psig or higher, approximately 1 psig or higher, approximately 5 psig or higher, approximately 25 psig or higher, approximately 50 psig or higher, approximately 100 psig or higher, approximately 150 psig or higher, approximately 200 psig or lower, approximately 250 psig or lower, approximately 300 psig or lower, approximately 350 psig or lower, approximately 400 psig or lower, approximately 450 psig or lower, approximately 500 psig or lower, or any value within these endpoints.

[0095] The steam mixture can be fed into a reactor system containing a catalyst. Suitable catalysts may include activated carbon (such as NORIT ROX 0.8) and silicon carbide (such as SiC1-E3-M). Preferably, the catalyst is commercially available.

[0096] 3. Removal of sulfur dioxide (SO2) after the formation of trifluoroacetyl iodide (TFAI) Sulfur dioxide (SO2) in the trifluoroacetyl chloride (TFAC) feed stream can promote undesirable side reactions during the reaction to form trifluoroacetyl iodide. Furthermore, in continuous processes, small amounts of sulfur dioxide (SO2) entering the reactor can accumulate downstream. Without being bound by theory, it is believed that the reaction between sulfur dioxide (SO2) and hydrogen iodide (HI) can lead to the formation of byproducts such as iodine (I2) and sulfur-containing byproducts such as dihydrogen sulfide (H2S) and sulfur. Both iodine (I2) and sulfur can form solids, causing equipment difficulties such as process line blockage. In addition, sulfur-containing substances can poison the catalysts used in the synthesis process, leading to reduced catalytic activity. It has been found that even small amounts of sulfur dioxide (SO2) in the reactor can promote iodine (I2) formation, resulting in process line blockage.

[0097] Sulfur dioxide (SO2) can be removed downstream of the reactor, either in combination with or alone, by contacting the product stream with one or more solid adsorbents, such as a carbon bed. Suitable solid adsorbents may include those described above in Section 1, such as molecular sieves, such as 3Å molecular sieves available from Acros Organics (also available from Honeywell UOP); 4Å and XH-9 molecular sieves available from Honeywell UOP; 10Å molecular sieves available from Grace Davison; and carbon molecular sieves, such as JEChem MSC-3K 172 carbon molecular sieve available from Osaka Gas Chemicals; activated alumina, such as SAS40 1 / 8" alumina available from BASF; zeolite ammonium powder, such as CBV5524G CY available from Zeolyst International; and activated carbon, such as, for example, NORIT ROX 0.8 activated carbon available from Cabot.

[0098] like Figure 11As shown, a feed stream containing trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) can be fed to reactor 150. A crude product stream 152 can be fed to a first adsorption column 154. A product stream 156 containing trifluoroacetyl iodide (TFAI), hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) can be fed to a first distillation column 158. A bottom product 160 containing purified trifluoroacetyl iodide (TFAI) can be removed. An overhead product 162 containing hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and a reduced amount of sulfur dioxide (SO2) can be fed to a second adsorption column 164 to provide a product stream 166 containing hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and a reduced amount of sulfur dioxide (SO2). Product stream 166 enters the second distillation column 168. The overhead product 170, containing hydrogen chloride (HCl), can be discharged, and the bottom product 172, containing trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and a reduced amount of sulfur dioxide (SO2), can be conveyed to a third adsorption column 174 to provide a recycle stream 176 containing trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and a reduced amount of sulfur dioxide (SO2). The trifluoroacetyl chloride (TFAC) 176 can then be recycled back to reactor 150. Alternatively or additionally, a portion of the bottom product stream 172 can be redirected to a purge stream 178.

[0099] The initial concentration of sulfur dioxide (SO2) in trifluoroacetyl chloride (TFAC) may be about 5000 ppm or less, about 2500 ppm or less, about 1000 ppm or less, about 900 ppm or less, about 800 ppm or more, about 700 ppm or more, about 600 ppm or more, about 500 ppm or more, or any value covered by these endpoints, as determined relative to trifluoroacetyl chloride (TFAC).

[0100] The concentration of sulfur dioxide (SO2) in the trifluoroacetyl chloride (TFAC) feed stream can be about 250 ppm or less, about 225 ppm or less, about 200 ppm or less, about 150 ppm or less, about 100 ppm or less, about 50 ppm or less, about 20 ppm or less, about 10 ppm or less, about 5 ppm or less, or about 1 ppm or less.

[0101] The above method may include all adsorption towers, may include two adsorption towers, or may include only one adsorption tower. The adsorption towers may be placed in... Figure 11In any or all of the locations shown, to reduce the sulfur dioxide (SO2) content in the system, thereby reducing the sulfur dioxide (SO2) content in the reactor feed. Similarly, as Figures 1 to 6 As shown, Figure 11 The adsorption tower shown can be used in conjunction with the removal of sulfur dioxide (SO2) from TFAC.

[0102] Reference Figure 11 Adsorption towers 154, 164, and 174 can be used. Alternatively, adsorption towers 154 and 164, adsorption towers 154 and 174, or adsorption towers 164 and 174 can be used alone. As a further alternative, adsorption tower 154, adsorption tower 164, or adsorption tower 174 can also be used alone.

[0103] The adsorption tower is placed in the second distillation tower. Figure 11 The bottom of (174) is particularly advantageous. At this point in the method, crude trifluoroacetyl iodide (TFAI) and hydrogen chloride (HCl) have already been removed. Furthermore, sulfur dioxide (SO2) may be more concentrated relative to trifluoroacetyl chloride (TFAC) at this point because some trifluoroacetyl chloride (TFAC) will have already reacted to form trifluoroacetyl iodide (TFAI). Finally, at this point in the method, it may not be necessary to reduce the sulfur dioxide (SO2) concentration in the trifluoroacetyl chloride (TFAC) feed stream to zero, as sulfur dioxide (SO2) can be removed from the recirculated feed stream.

[0104] Once the adsorption tower or bed is saturated with sulfur dioxide (SO2), it can be regenerated as described in section 1 above.

[0105] As mentioned above, in addition to the adsorption tower or bed, optional purging can also be used to reduce the amount of sulfur dioxide (SO2) present. Besides trifluoroacetyl chloride (TFAC), the product stream leaving the tower and adsorption tower or bed may also contain small amounts of sulfur dioxide (SO2). If necessary, the product stream can be periodically purged to remove sulfur dioxide (SO2) from the system, with only a small amount of trifluoroacetyl chloride (TFAC) lost.

[0106] As an alternative, a fresh supply of trifluoroacetyl chloride (TFAC) with sulfur dioxide (SO2) impurities can be pre-distilled and treated with the adsorbent described above before being combined with the TFAC recycle stream. In this method, the sulfur dioxide (SO2) level can be low before being combined with the recycle stream. Specifically, the sulfur dioxide level can be about 40 ppm or less, about 30 ppm or less, about 20 ppm or less, about 15 ppm or less, about 10 ppm or less, about 5 ppm or less, or about 1 ppm or less.

[0107] 4. Perform TFAI substitution synthesis, followed by SO2 removal by distillation. This invention provides a method for synthesizing trifluoroacetyl chloride (TFAI) from trifluoroacetyl chloride (TFAC) and hydrogen iodide (HI) while minimizing the aforementioned undesirable impurities and byproducts. In this method, a feed stream containing trifluoroacetyl chloride (TFAC) with reduced levels of impurities is contacted with a feed stream containing hydrogen iodide (HI) with reduced levels of impurities. Therefore, both the individual feed streams and the combined feed streams are substantially free of impurities such as sulfur dioxide (SO2), iodine (I2), and ionic metals.

[0108] The feed stream may contain non-recycled (fresh) trifluoroacetyl chloride (TFAC) and hydrogen iodide (HI). Alternatively, the feed stream may contain recycled trifluoroacetyl chloride (TFAC) and hydrogen iodide (HI). As yet another alternative, the feed stream may contain a combination of recycled and non-recycled trifluoroacetyl chloride (TFAC) and hydrogen iodide (HI).

[0109] For example, the amount of sulfur dioxide (SO2) present in a trifluoroacetyl chloride (TFAC) feed stream can be reduced using simple distillation, azeotropic distillation, and / or contact with a solid adsorbent. Feed streams containing fresh trifluoroacetyl chloride (TFAC) can be purified, feed streams containing recycled trifluoroacetyl chloride (TFAC) can be purified, or both can be purified.

[0110] The amount of sulfur dioxide (SO2) present in the trifluoroacetyl chloride (TFAC) feed stream may be less than about 400 ppm or less, about 300 ppm or less, about 200 ppm or less, about 100 ppm or less, about 50 ppm or less, about 20 ppm or less, or about 10 ppm or less by weight, as determined by GC-TCD (gas chromatography-thermal conductivity detector).

[0111] It can purify feed streams containing fresh hydrogen iodide (HI), feed streams containing recycled hydrogen iodide (HI), or both. For example, the amount of iodine (I2) present in a hydrogen iodide (HI) feed stream can be reduced by simple distillation and / or contact with a solid adsorbent.

[0112] The method disclosed herein provides a method for producing trifluoroacetyl iodine (TFAI), wherein the amount of iodine (I2) present in the hydrogen iodide (HI) feed stream is less than about 1000 ppm, less than about 500 ppm, less than about 250 ppm, less than about 100 ppm, less than about 50 ppm, less than about 20 ppm, or less than about 10 ppm by weight.

[0113] To limit certain impurities, the molar ratio of trifluoroacetyl chloride (TFAC) to hydrogen iodide (HI) can be about 1:1 or less, about 0.9:1 or less, about 0.8:1 or less, about 0.7:1 or less, or about 0.6:1 or less, or about 0.1:1 or less, or about 0.05:1 or less, or about 0.02:1 or less.

[0114] To avoid being limited by theory, a ratio of 1:2 or less of trifluoroacetyl chloride (TFAC) to hydrogen iodide (HI) allows the trifluoroacetyl chloride to react substantially completely, leaving a product stream containing sulfur dioxide (SO2) and a small amount of trifluoroacetyl chloride (TFAC), thereby reducing the need to remove residual trifluoroacetyl chloride (TFAC).

[0115] Sulfur dioxide (SO2) can then be removed downstream of the reactor, such as... Figure 12 As shown. A feed stream containing trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2) impurities, and hydrogen iodide (HI) in a ratio of 1:2 or less can be fed to reactor 180 to provide a crude product stream 182 containing trifluoroacetyl iodide (TFAI), hydrogen chloride (HCl), hydrogen iodide (HI), a small amount of unreacted trifluoroacetyl chloride (TFAC), and sulfur dioxide (SO2). The crude product stream can be fed to a first distillation column 184. The overhead product 186 containing hydrogen chloride (HCl) can be removed. The bottom product 188 containing trifluoroacetyl iodide (TFAI), hydrogen iodide (HI), a small amount of unreacted trifluoroacetyl chloride (TFAC), and sulfur dioxide (SO2) can be fed to a second distillation column 190. The overhead product 192 containing HI can be recycled back to reactor 180. The bottom product 194, containing trifluoroacetyl iodide (TFAI), a small amount of unreacted trifluoroacetyl chloride (TFAC), and sulfur dioxide (SO2), can be fed to the third distillation column 196. The bottom product 198, containing trifluoroacetyl iodide (TFAI), can be collected as needed. The top product 200, containing trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2), can be removed from the process as a purge stream 204, or a portion of the top product 200 can be recycled to the feed stream 182 via stream 202, while the remainder is purged via stream 204.

[0116] The following non-limiting embodiments are used to illustrate this disclosure. Example

[0117] Example 1 - PTx Study: 10℃ Isotherm An azeotropic and azeotropic compositions of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) were measured using a set of volume-calibrated PTx units. A mixture of TFAC and SO2 was prepared gravimetrically into evacuated PTx units; two units were reserved for measuring each pure component. Once prepared, each of up to eight units with different compositions was inserted into a constant-temperature chamber. In this chamber, each unit was attached to an instrumentation manifold equipped with a calibrated pressure sensor and a resistance temperature detector (RTD); this provided a means of measuring and recording the total saturation pressure of the contents of each unit at its local temperature.

[0118] To establish equilibrium at the target temperature, the chamber setpoint is adjusted to an average temperature (T0) of 10°C. avg Once equilibrium was realized after the temperature and pressure in each cell had stabilized for several hours, the local temperature and saturation pressure of each cell were recorded. From these pressure-temperature-composition data, the binary interaction parameters of TFAC and SO2 in the Helmholtz energy equation of state (HEOS) were determined. Figure 7 The maximum pressure indicated by the figure shows that a minimum boiling azeotropic composition of about 75.0% by weight of TFAC and about 25.0% by weight of SO2 was formed, and the data are presented in Table 1 below.

[0119] Table 1 PTx study of TFAC and SO2 at an average temperature of 10℃ .

[0120] Example 2 - SO2 adsorption efficiency of various solid adsorbents Approximately 50 mL of pre-weighed selected solid adsorbent was added to the adsorption tower. Approximately 300 g of trifluoroacetyl chloride (TFAC) containing 0.1069 wt% SO2 was loaded into a 500 mL stainless steel cylinder. After pressure testing the system, the SO2-containing TFAC was circulated through the adsorption tower at room temperature (20°C to 30°C) using a recirculation pump. After 24 hours, the recirculation pump was stopped, and a TFAC sample was taken out for analysis to determine the SO2 concentration. The SO2 removal efficiency was then calculated.

[0121] The tested solid adsorbents are listed in Table 2 below.

[0122] Table 2 .

[0123] Table 3 below shows the removal efficiency of different adsorbents. All tested solid adsorbents showed some degree of SO2 removal capacity, with SO2 being completely adsorbed by Osaka Gas Chemicals MSC-3K 172 carbon molecular sieve.

[0124] Table 3 .

[0125] Example 3 - SO2 saturation of the adsorbent Approximately 50 mL of Osaka Gas Chemicals MSC-3K 172 carbon molecular sieve (29.72 g) was loaded into the adsorption column. 5120 g of TFAC containing 0.0995 wt% SO2 was loaded into a 3-gallon stainless steel cylinder. After pressure testing the system, the SO2-containing TFAC was circulated through the adsorption column using a recirculation pump at room temperature (20°C to 30°C). TFAC samples were periodically removed for SO2 concentration analysis by TCD-GC. The results are shown in... Figure 8 After 24 hours, the SO2 concentration in TFAC stabilized at 414 ppm, indicating that the adsorbent was saturated with SO2. The SO2 adsorption capacity of this adsorbent was determined to be approximately 10% by weight (or 0.10 g of SO2 adsorbed per gram of adsorbent).

[0126] Example 4 - Reduction of SO2 levels in TFAC This example demonstrates that SO2 levels in a trifluoroacetyl chloride (TFAC) feedstock can be reduced to various reduction levels via multiple cycles of recirculation. Fresh solid adsorbent was used initially and after each successive recirculation cycle, which was conducted at room temperature (20°C to 30°C). As shown in Table 4, the SO2 level decreased from its initial level of 1130 ppm to 258 ppm after cycle 1; to 156 ppm after cycle 2; to 80 ppm after cycle 3; and to zero (below the instrument's detection limit) after cycle 4. The percentage of SO2 removed relative to the initial amount of SO2 for each cycle is presented in Table 4.

[0127] Table 4 * Relative to the original SO2 level in TFAC.

[0128] Example 5 - Regeneration of Used Adsorbent Thermogravimetric analysis / mass spectrometry (TGA-MS) was performed on used JEChem MSC-3K 172 carbon molecular sieves (currently available from Osaka Gas Chemicals) under a nitrogen atmosphere to identify the adsorbed substances and desorption conditions. The TGA results are shown in... Figure 9 In, and the MS results are shown in Figure 10 middle.

[0129] Two significant (one major and one minor) weight loss events were observed. Both events were primarily attributed to SO2 desorption (m / z = 64). The major weight loss exhibited a maximum m / z intensity at 920 s, corresponding to 196 °C on the TGA data. The minor weight loss exhibited a maximum m / z intensity at 1711 s, corresponding to 335 °C on the TGA data. No m / z value corresponding to SO2 was detected after 500 °C. These results indicate that partial regeneration of the used adsorbent can be achieved within the temperature range of 196 °C to 335 °C.

[0130] Used JEChem MSC-3K 172 carbon molecular sieve was regenerated at 200°C for 24 hours under nitrogen purging. The regenerated JEChem MSC-3K 172 carbon molecular sieve was then used as an adsorbent. Recycling was performed for 24 hours at room temperature (20°C to 30°C). As shown in Table 5, after 24 hours of recycling, the SO2 level in the TFAC decreased from 431 ppm to 316 ppm, and its SO2 adsorption capacity was determined to be 0.06 g SO2 / g adsorbent (approximately 60% of the capacity of the fresh adsorbent presented in Example 3). These results indicate that the used JEChem MSC-3K 172 carbon molecular sieve was partially regenerated.

[0131] Table 5 .

[0132] Example 6 - Isolation and purification of trifluoroacetyl chloride (TFAC) A composition comprising crude trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and at least one additional impurity is provided. In a first step, the relative amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) are adjusted by adding trifluoroacetyl chloride (TFAC), adding sulfur dioxide (SO2), or both trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2). The composition is then exposed to effective conditions to form an azeotrope or azeotropic-like mixture. The azeotrope or azeotropic-like mixture can then be separated from at least one impurity by distillation, phase separation, or fractionation. Once the azeotrope or azeotropic-like mixture has been separated from the impurity, in a second step, the components of the azeotrope or azeotropic-like mixture—trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2)—are separated from each other. The separation of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) can then be accomplished by distillation, exposure to a solid adsorbent, or a combination thereof.

[0133] Example 7 - Distillation of Trifluoroacetyl chloride (TFAC) A composition comprising crude trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) is provided. This composition is fed into a distillation column. The distillate is collected, which may contain sulfur dioxide (SO2), trifluoroacetyl chloride (TFAC), or a mixture thereof. A bottom product containing trifluoroacetyl chloride (TFAC) may be collected. The amount of sulfur dioxide (SO2) present in the bottom product may be 100 ppm or less, 50 ppm or less, 10 ppm or less, or 1 ppm or less.

[0134] Example 8 - Azeotropic distillation of trifluoroacetyl chloride (TFAC) The composition containing trifluoroacetyl chloride (TFAC) and 2500 ppm sulfur dioxide (SO2) is purified to provide a purified TFAC feed containing 5 ppm SO2.

[0135] A crude TFAC feed of 1000 lb / hr, containing 997.5 lb / hr of TFAC and 2.5 lb / hr of SO2, is fed into a distillation column operating at 52.7 psia at the top. This column has 40 trays and is equipped with a condenser cooled by cold water supplied at 5°C, allowing the column top temperature to operate at approximately 10°C. The reboiler is heated with steam (e.g., 10 psig saturated steam at 115°C). The bottom stream of purified TFAC containing 5 ppm SO2 is recovered at a reflux rate of 1540 lb / hr and a boiling rate of 1820 lb / hr. The top and distillate streams are concentrated into a near-azeotropic composition of TFAC and SO2 (approximately 76 wt% TFAC, total distillate flow rate 10.25 lb / hr). The distillation yield of TFAC exceeds 99.2%.

[0136] Table 6 composition .

[0137] Table 7 tower conditions .

[0138] Other conditions, including different numbers of trays, different feed trays, different pressures, different reflux ratios, and different boiling ratios, can also be used to purify TFAC / SO2 mixtures.

[0139] Example 9 - An alternative method for distilling trifluoroacetyl chloride (TFAC) A composition comprising crude trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) is provided. In a first step, the composition is fed into a distillation column and exposed to effective conditions to form an azeotrope or azeotropic mixture. A bottom product containing trifluoroacetyl chloride (TFAC) may be collected. The amount of sulfur dioxide (SO2) present in the bottom product may be 100 ppm or less, 50 ppm or less, 10 ppm or less, or 1 ppm or less.

[0140] The azeotrope or azeotropic mixture is collected as a distillate. The components of the azeotrope or azeotropic mixture in the distillate—trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2)—are separated from each other in a second step. The separation of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) can then be accomplished by distillation, exposure to a solid adsorbent, or a combination thereof.

[0141] Example 10 - A purging method for removing sulfur dioxide (SO2) after the formation of trifluoroacetyl iodine (TFAI) (Comparative Example) This comparative example illustrates how to control SO2 accumulation in a process by removing a portion of SO2 from the recycle stream without using an adsorption tower in the recirculation. A feed stream containing 999 lb / hr of TFAC and 1 lb / hr of SO2 (1000 ppm SO2 relative to TFAC) is pre-conditioned to remove SO2 by the aforementioned method (either “upstream” distillation and adsorption, or both), resulting in a composition containing 50 ppm SO2 relative to TFAC (i.e., a TFAC / SO2 mass ratio of approximately 20000 / 1). This stream is combined with HI (which may contain impurities) and a recycle stream containing TFAC and HI (which may contain other impurities, including SO2). The combined stream is fed into a reactor. Sulfur dioxide (SO2) is not consumed in the reactor and can therefore become concentrated during the process. The reactor effluent is fed into a first distillation column to recover the bottom stream containing TFAC. The overhead stream from the first distillation column is fed into a second distillation column. The feed containing HCl is recovered in the overhead of the second distillation column. The bottoms of the second distillation column, containing TFAC, HI, and SO2, are recycled back to the reactor. To control SO2 buildup, a portion of the recycle feed is purged (i.e., removed from the recycle feed). To maintain the desired SO2 level of 250 ppm in the recycle feed, approximately 15% of the recycle feed must be purged, representing a loss in the yield of reactants TFAC and HI. This purging results in a loss of approximately 6% of the freshly entered TFAC (63 × 0.9435). Additional losses of TFAC may occur during SO2 removal via distillation.

[0142] Table 8 Purge Flow Composition .

[0143] Example 11: Removal of sulfur dioxide (SO2) using an adsorption tower after the formation of trifluoroacetyl iodine (TFAI) A feed stream containing trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) is fed into the reactor. The crude product stream is fed into... Figure 11 A first adsorption column, shown as 154, provides a product stream containing trifluoroacetyl iodide (TFAI), hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), and hydrogen iodide (HI). This product stream is then fed to a first distillation column. The bottom product of the first distillation column contains purified trifluoroacetyl iodide (TFAI). The top product contains hydrogen chloride, trifluoroacetyl chloride (TFAC), and hydrogen iodide (HI). This stream is passed through a compressor and then to a second distillation column. The top product of the second distillation column, containing hydrogen chloride (HCl), is discharged, and the bottom product containing trifluoroacetyl chloride (TFAC) and hydrogen iodide (HI) is recycled back into the feed stream.

[0144] Example 12: Removal of sulfur dioxide (SO2) using an adsorption tower after the formation of trifluoroacetyl iodide (TFAI). A feed stream containing trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) is fed to the reactor. A crude product stream containing trifluoroacetyl iodide (TFAI), sulfur dioxide (SO2), hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), and hydrogen iodide (HI) is fed to a first distillation column, from which a bottom product containing purified trifluoroacetyl iodide (TFAI) is removed. An overhead product containing hydrogen chloride (HCl), sulfur dioxide (SO2), trifluoroacetyl chloride (TFAC), and hydrogen iodide (HI) is fed to an adsorption column. Figure 11 (164) to provide a product stream with reduced sulfur dioxide (SO2). The product stream is then passed through a compressor and then fed to a second distillation column. The top product of the second distillation column, containing hydrogen chloride (HCl), is discharged, and the bottom product, containing trifluoroacetyl chloride (TFAC) and hydrogen iodide (HI), is recycled back into the feed stream.

[0145] Example 13: Removal of sulfur dioxide (SO2) using an adsorption tower after the formation of trifluoroacetyl iodide (TFAI). A feed stream containing 999 lb / hr of TFAC and 1 lb / hr of SO2 (1000 ppm SO2 relative to TFAC) is preconditioned by the aforementioned method (one or both of “upstream” distillation and adsorption) to remove SO2, thereby achieving a composition containing 50 ppm SO2 relative to TFAC (i.e., a TFAC / SO2 mass ratio of approximately 20000 / 1). This feed stream is combined with HI (which may contain impurities) and a recycle feed stream containing TFAC and HI (which may contain other impurities, including SO2). The combined feed stream is fed into a reactor. Sulfur dioxide (SO2) is not consumed in the reactor and can therefore become concentrated during the process. The reactor effluent is fed to a first distillation column to recover the bottoms stream containing TFAC. The overheads of the first distillation column, containing hydrogen chloride (HCl), sulfur dioxide (SO2), trifluoroacetyl chloride (TFAC), and hydrogen iodide (HI), are fed to a second distillation column. The overheads of the second distillation column are recovered from the HCl-containing stream. The bottoms of the second distillation column, containing trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and sulfur dioxide (SO2), are conveyed to the adsorption column. Figure 11 174), to provide a product stream containing trifluoroacetyl chloride (TFAC) and hydrogen iodide (HI) and reduced concentrations of sulfur dioxide (SO2). Trifluoroacetyl chloride (TFAC) and hydrogen iodide (HI) can then be recycled.

[0146] The adsorption tower is packed with adsorbent, such as Osaka Gas Chemicals JEChem MSC-3K 172 carbon molecular sieve. To maintain the desired SO2 level of 250 ppm in the recycle stream, purging from the recycle stream is unnecessary because the adsorbent selectively adsorbs SO2 from the recycle stream. Therefore, the yield loss associated with purging is eliminated. The composition of the recycle stream is shown in Table 9 below, based on a feed rate of 999 lb / hr TFAC, a TFAC conversion of 98% per pass, and a TFAC / HI molar ratio of 1.4 at the reactor inlet. Additional losses of TFAC during SO2 removal via distillation are not shown.

[0147] Table 9 Circulating material flow composition .

[0148] Example 14: Removal of sulfur dioxide (SO2) using two adsorption towers after the formation of trifluoroacetyl iodine (TFAI) A feed stream containing trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) is fed to the reactor. A crude product stream containing trifluoroacetyl iodide (TFAI), sulfur dioxide (SO2), hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), and hydrogen iodide (HI) is fed to the first adsorption tower. Figure 11 (154 in the text). The product stream containing trifluoroacetyl iodine (TFAI), hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and a reduced amount of sulfur dioxide (SO2) is then fed to the first distillation column. The bottom product containing purified trifluoroacetyl iodine (TFAI) is removed. The top product containing hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) is fed to the second adsorption column (…). Figure 11 The product stream (164) is supplied to contain hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and a reduced amount of sulfur dioxide (SO2), and is passed through a compressor and then conveyed to a second distillation column. The overhead product containing hydrogen chloride (HCl) can be discharged, and the bottom product containing trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and a reduced concentration of sulfur dioxide (SO2) can be recycled.

[0149] Example 15: Removal of sulfur dioxide (SO2) using two adsorption towers after the formation of trifluoroacetyl iodine (TFAI) A feed stream containing trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) is fed to the reactor. A crude product stream containing trifluoroacetyl iodide (TFAI), sulfur dioxide (SO2), hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), and hydrogen iodide (HI) is fed to the first adsorption tower. Figure 11 (154 in the text). The product stream containing trifluoroacetyl iodine (TFAI), hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and a reduced amount of sulfur dioxide (SO2) is then fed to the first distillation column. The bottom product containing purified trifluoroacetyl iodine (TFAI) is removed. The top product containing hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) is passed through a compressor and then fed to the second distillation column. The top product containing hydrogen chloride (HCl) can be discharged, and the bottom product containing trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and sulfur dioxide (SO2) can be fed to the second adsorption column (…). Figure 11 (174) to provide a product stream containing trifluoroacetyl chloride (TFAC) and hydrogen iodide (HI) and reduced concentration of sulfur dioxide (SO2). Trifluoroacetyl chloride (TFAC) and hydrogen iodide (HI) can then be recycled.

[0150] Example 16: Removal of sulfur dioxide (SO2) using two adsorption towers after the formation of trifluoroacetyl iodine (TFAI) A feed stream containing trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) is fed to the reactor. A crude product stream containing trifluoroacetyl iodide (TFAI), sulfur dioxide (SO2), hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), and hydrogen iodide (HI) is fed to the first distillation column. The bottom product containing purified trifluoroacetyl iodide (TFAI) is removed. The top product containing hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) is fed to the first adsorption column. Figure 11 164), to provide a product stream containing hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and a reduced amount of sulfur dioxide (SO2), and pass it through a compressor, then to a second distillation column. The overhead product containing hydrogen chloride (HCl) can be discharged, and the bottom product containing trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and sulfur dioxide (SO2) can be conveyed to a second adsorption column ( Figure 11 174), to provide a product stream containing trifluoroacetyl chloride (TFAC) and hydrogen iodide (HI) and reduced concentrations of sulfur dioxide (SO2). The trifluoroacetyl chloride (TFAC) and hydrogen iodide (HI) are then recycled.

[0151] Example 17: Removal of sulfur dioxide (SO2) using three adsorption towers after the formation of trifluoroacetyl iodine (TFAI) A feed stream containing trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) is fed to the reactor. A crude product stream containing trifluoroacetyl iodide (TFAI), sulfur dioxide (SO2), hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), and hydrogen iodide (HI) is fed to the first adsorption tower. Figure 11 154), to provide a product stream containing trifluoroacetyl iodide (TFAI), hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and a reduced amount of sulfur dioxide (SO2). The product stream is fed to a first distillation column. The bottom product containing purified trifluoroacetyl iodide (TFAI) is removed. The top product containing hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) is fed to a first adsorption column ( Figure 11164), to provide a product stream containing hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and a reduced amount of sulfur dioxide (SO2), and pass it through a compressor, then to a second distillation column. The overhead product containing hydrogen chloride (HCl) can be discharged, and the bottom product containing trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and sulfur dioxide (SO2) can be conveyed to a second adsorption column ( Figure 11 174), to provide a product stream containing trifluoroacetyl chloride (TFAC) and hydrogen iodide (HI) and reduced concentrations of sulfur dioxide (SO2). The trifluoroacetyl chloride (TFAC) and hydrogen iodide (HI) are then recycled.

[0152] Example 18: Alternative Synthesis of Trifluoroacetyl Iodine (TFAI) and Removal of Sulfur Dioxide (SO2) A feed stream containing 500 lb / hr of trifluoroacetyl chloride (TFAC) and 0.125 lb / hr of sulfur dioxide (SO2) (250 ppm relative to TFAC) is contacted with a feed stream containing fresh and recycled hydrogen iodide (HI). The fresh HI may contain iodine (I2) at 1000 ppm or less relative to the HI. The combined feed stream of fresh and recycled hydrogen iodide (HI) contains 1932 lb / hr of HI and 0.15 lb / hr of iodine (I2), resulting in a trifluoroacetyl chloride (TFAC) to hydrogen iodide (HI) molar ratio of 0.25:1. The feed stream is fed to the reactor to provide a crude product stream containing trifluoroacetyl iodide (TFAI), hydrogen chloride (HCl), hydrogen iodide (HI), trifluoroacetyl chloride (TFAC), and sulfur dioxide (SO2). The crude product stream is fed to the first distillation column. The overhead product containing hydrogen chloride (HCl) is removed. The bottom product, containing trifluoroacetyl iodine (TFAI), hydrogen iodide (HI), trifluoroacetyl chloride (TFAC), and sulfur dioxide (SO2), is then fed to a second distillation column. The overhead product, containing hydrogen iodide, is recycled back to the reactor. The bottom product, containing trifluoroacetyl iodine (TFAI), trifluoroacetyl chloride (TFAC), and sulfur dioxide (SO2), is then fed to a third distillation column. The bottom product, containing purified trifluoroacetyl iodine (TFAI), is collected, while the overhead product, containing trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2), is purged. Optionally, a portion of this stream can be recycled. Figure 12 A schematic diagram of the process is shown. Tables 10 and 11 below show the material balance.

[0153] Table 10 .

[0154] Table 11 .

[0155] Example 19: Removal of SO2 from TFAC by intermittent distillation 52.73 lb of TFAC containing 740 ppm SO2 was charged into a distillation unit equipped with a 10-gallon reboiler, a 2" ID × 120" L column (filled with Goodloe 2" diameter × 6" thickness structured metal packing), and a shell-and-shell condenser tube (surface area 10.45 ft²) for batch distillation to remove SO2 from the TFAC. The reboiler was heated to approximately 40°C with a 30 psig steam / tap water mixture. During this operation, every 2-4 hours, a column pressure of 2-4 psig was vented from the top of the column to a light matter collection cylinder to remove non-condensable gases at start-up and purge concentrated SO2 from the system. The top reflux and reboiler samples were periodically removed for SO2 analysis using a pre-calibrated TCD-GC. Based on this result, the SO2 contained in the TFAC was concentrated in the top reflux. The top purging continued, and the SO2 concentration in the reboiler continued to decrease until it reached the GC detection limit (<5 ppm). After eight reboiler samples showed SO2 levels below the detection limit (<5 ppm), the reboiler material was completely discharged into the heavy matter collection cylinder, yielding 49.67 lb of purified TFAC containing <5 ppm SO2 (below the detection limit), representing a yield of 96.84%. During operation, the light matter collection cylinder increased by 1.53 lb, giving a total mass balance of 99.82%.

[0156] A second batch distillation was performed in the same distillation unit as described above. 54.70 lb of TFAC containing 958 ppm SO2 was charged into the reboiler. During this operation, every 2-4 hours, the column pressure was evacuated from the top of the column to the light matter collection cylinder at 2 psig-4 psig to remove non-condensable gases and purge concentrated SO2 from the system at startup. The top reflux and reboiler samples were periodically removed for SO2 analysis using a pre-calibrated TCD-GC. Based on this result, the SO2 contained in the TFAC was concentrated in the top stream. Column purging continued, and the reboiler SO2 concentration continued to decrease until it reached the GC detection limit (<5 ppm). After three reboiler samples showed SO2 levels below the detection limit (<5 ppm), the reboiler material was completely evacuated into the heavy matter collection cylinder, yielding 53.93 lb of purified TFAC containing <5 ppm SO2 (below the detection limit), representing a yield of 98.59%. During operation, the lightweight collection cylinder increased by 0.49 lb, which gave a total mass balance of 99.49%.

[0157] aspect Aspect 1 is a composition comprising an azeotrope or azeotropic-like composition, which is substantially composed of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2).

[0158] Aspect 2 is the composition according to aspect 1, wherein the azeotropic or azeotropic composition has a boiling point of about 10.0°C ± 3°C at a pressure of about 45 psia ± 0.3 psia.

[0159] Aspect 3 is the composition according to aspect 1 or aspect 2, wherein the azeotropic or azeotropic composition is substantially composed of about 25% to about 99% by weight of trifluoroacetyl chloride (TFAC) and about 1% to about 75% by weight of sulfur dioxide (SO2).

[0160] Aspect 4 is a composition according to any one of aspects 1 to 3, wherein the azeotropic or azeotropic composition is substantially composed of about 48% to about 90% by weight of trifluoroacetyl chloride (TFAC) and about 10% to about 52% by weight of sulfur dioxide (SO2).

[0161] Aspect 5 is a method for forming an azeotrope or azeotropic-like composition, the method comprising the step of combining trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) to form an azeotrope or azeotropic-like composition substantially composed of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2), the azeotrope or azeotropic-like composition having a boiling point of about 10.0 °C ± 3 °C at a pressure of about 45 psia ± 0.3 psia.

[0162] Aspect 6 is the method according to aspect 5, wherein the combining step comprises combining about 25% by weight to about 99% by weight of trifluoroacetyl chloride (TFAC) and about 1% by weight to about 75% by weight of sulfur dioxide (SO2).

[0163] Aspect 7 is a method for removing sulfur dioxide (SO2) from trifluoroacetyl chloride (TFAC), the method comprising at least one of distillation, adsorption, or a combination thereof.

[0164] Aspect 8 is the method according to aspect 7, the method further comprising the steps of: feeding a feed stream into a distillation column, the feed stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); collecting a distillate from the distillation column comprising trifluoroacetyl chloride and sulfur dioxide (SO2); and collecting a bottom product from the distillation column, the bottom product consisting substantially of trifluoroacetyl chloride (TFAC).

[0165] Aspect 9 is the method according to aspect 7, the method further comprising the steps of: feeding a feed stream into a distillation column, the feed stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); forming an azeotrope or azeotropic-like composition substantially composed of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); collecting a distillate from the distillation column comprising the azeotrope or azeotropic-like composition; and collecting a bottom product from the distillation column substantially composed of trifluoroacetyl chloride (TFAC).

[0166] Aspect 10 is the method according to aspect 7, the method further comprising the steps of: feeding a feed stream into a distillation column, the feed stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); forming an azeotrope or azeotropic-like composition substantially composed of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); collecting a distillate from the distillation column comprising the azeotrope or azeotropic-like composition; collecting a bottom product from the distillation column; contacting the bottom product from the distillation column with a solid adsorbent; and collecting a product stream substantially composed of trifluoroacetyl chloride (TFAC) from the solid adsorbent.

[0167] Aspect 11 is the method according to aspect 7, the method further comprising the steps of: feeding a feed stream into a distillation column, the feed stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); forming an azeotrope or azeotropic-like composition comprising substantially effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); collecting the bottom product from the distillation column; collecting the distillate from the column comprising the azeotrope or azeotropic-like composition; contacting the distillate with a solid adsorbent; and collecting a product stream comprising substantially trifluoroacetyl chloride (TFAC) from the solid adsorbent.

[0168] Aspect 12 is the method according to aspect 7, the method further comprising the steps of: feeding a feed stream into a distillation column, the feed stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); forming an azeotrope or azeotropic-like composition substantially composed of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); collecting the bottom product from the distillation column; contacting the bottom product from the distillation column with a first solid adsorbent; collecting a product stream from the first solid adsorbent, the product stream substantially composed of trifluoroacetyl chloride (TFAC); collecting a distillate from the column, the distillate comprising the azeotrope or azeotropic-like composition; contacting the distillate from the distillation column with a second solid adsorbent; and collecting a product stream from the second solid adsorbent, the product stream substantially composed of trifluoroacetyl chloride (TFAC).

[0169] Aspect 13 is the method according to aspect 7, the method further comprising the steps of: contacting a feed stream with a first solid adsorbent, the feed stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); collecting a product stream from the solid adsorbent, the product stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); conveying the product stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) to a distillation column; forming an azeotrope or azeotropic-like composition, the azeotrope or azeotropic-like composition being substantially composed of an effective amount of trifluoroacetyl chloride. The process involves: composing a distillation column with acyl chloride (TFAC) and sulfur dioxide (SO2); collecting the bottom product from the distillation column; contacting the bottom product from the distillation column with a second solid adsorbent; collecting a product stream from the second solid adsorbent, the product stream consisting essentially of trifluoroacetyl chloride (TFAC); collecting a distillate from the column containing the azeotrope or azeotropic-like composition; contacting the distillate from the distillation column with a third solid adsorbent; and collecting a product stream from the third solid adsorbent, the product stream consisting essentially of trifluoroacetyl chloride (TFAC).

[0170] Aspect 14 is the method according to any one of Aspects 8 to 13, wherein the bottom product contains about 100 ppm or less of sulfur dioxide (SO2).

[0171] Aspect 15 is the method according to aspect 7, the method further comprising the steps of: contacting a feed stream containing a mixture of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) with a solid adsorbent or a mixture of two or more solid adsorbents; and collecting a product stream, the product stream consisting substantially of trifluoroacetyl chloride (TFAC).

[0172] Aspect 16 is the method according to any one of aspects 10 to 15, wherein the solid adsorbent is selected from: molecular sieves, zeolite powder, silica gel, activated alumina and activated carbon.

[0173] Aspect 17 is the method according to any one of aspects 10 to 16, wherein the solid adsorbent is a molecular sieve.

[0174] Aspect 18 is a method for separating trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) from a composition comprising trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and at least one impurity, the method comprising the steps of: forming an azeotrope or azeotropic-like composition consisting substantially of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2), the azeotrope or azeotropic-like composition having a boiling point between about -30°C ± 3°C and about 90.0°C ± 3°C at a pressure between about 5 psia ± 0.3 psia and about 450 psia ± 0.3 psia; and separating the azeotrope or azeotropic-like composition from the composition and the at least one impurity.

[0175] Aspect 19 is a method for synthesizing trifluoroacetyl iodine (TFAI), the method comprising: contacting a feed stream containing trifluoroacetyl chloride (TFAC) with a feed stream containing hydrogen iodide (HI) to provide a product stream containing trifluoroacetyl iodine (TFAI).

[0176] Aspect 20 is the method according to aspect 19, wherein the molar ratio of trifluoroacetyl chloride (TFAC) to hydrogen iodide (HI) is 1:2 or less.

[0177] Aspect 21 is the method according to aspect 19 or aspect 20, the method further comprising removing sulfur dioxide (SO2) from the product stream.

[0178] Aspect 22 is a composition comprising an azeotrope or azeotropic composition consisting essentially of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2).

[0179] Aspect 23 is the composition according to aspect 22, wherein the azeotropic or azeotropic composition has a boiling point of about 10.0°C ± 3°C at a pressure of about 45 psia ± 0.3 psia.

[0180] Aspect 24 is a method for removing sulfur dioxide (SO2) from trifluoroacetyl chloride (TFAC), the method comprising at least one of distillation, adsorption, or a combination thereof.

[0181] Aspect 25 is a method according to any one of Aspect 24 or Aspects 8 to 21, the method further comprising the steps of: feeding a feed stream into a distillation column, the feed stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); collecting a distillate from the distillation column comprising trifluoroacetyl chloride and sulfur dioxide (SO2); and collecting a bottom product from the distillation column, the bottom product consisting substantially of trifluoroacetyl chloride (TFAC).

[0182] Aspect 26 is a method according to any one of Aspects 24, 25, or 8 to 21, the method further comprising the steps of: feeding a feed stream into a distillation column, the feed stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); forming an azeotrope or azeotropic-like composition substantially composed of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); collecting a distillate from the distillation column comprising the azeotrope or azeotropic-like composition; and collecting a bottom product from the distillation column substantially composed of trifluoroacetyl chloride (TFAC).

[0183] Aspect 27 is a method according to any one of Aspects 24 to 25 or 8 to 21, the method further comprising the steps of: feeding a feed stream into a distillation column, the feed stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); forming an azeotrope or azeotropic-like composition substantially composed of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); collecting a distillate from the distillation column comprising the azeotrope or azeotropic-like composition; collecting a bottom product from the distillation column; contacting the bottom product from the distillation column with a solid adsorbent; and collecting a product stream substantially composed of trifluoroacetyl chloride (TFAC).

[0184] Aspect 28 is a method according to any one of Aspects 24 to 27 or 8 to 21, the method further comprising the steps of: feeding a feed stream into a distillation column, the feed stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); forming an azeotrope or azeotropic-like composition substantially composed of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); collecting the bottom product from the distillation column; collecting the distillate from the column, the distillate comprising the azeotrope or azeotropic-like composition; contacting the distillate with a solid adsorbent; and collecting a product stream substantially composed of trifluoroacetyl chloride (TFAC).

[0185] Aspect 29 is a method according to any one of Aspects 24 to 28 or 8 to 21, the method further comprising the steps of: feeding a feed stream into a distillation column, the feed stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); forming an azeotrope or azeotropic-like composition substantially composed of effective amounts of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); collecting the bottom product from the distillation column; contacting the bottom product from the distillation column with a first solid adsorbent; collecting a product stream substantially composed of trifluoroacetyl chloride (TFAC); collecting a distillate from the column comprising the azeotrope or azeotropic-like composition; contacting the distillate from the distillation column with a second solid adsorbent; and collecting a product stream substantially composed of trifluoroacetyl chloride (TFAC).

[0186] Aspect 30 is a method according to any one of Aspects 24 to 29 or 8 to 21, the method further comprising the steps of: contacting a feed stream with a first solid adsorbent, the feed stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); collecting a product stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2); conveying the product stream comprising trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) to a distillation column; forming an azeotrope or azeotropic-like composition substantially composed of... The process comprises: collecting the bottom product from the distillation column; contacting the bottom product from the distillation column with a second solid adsorbent; collecting the product stream, which is substantially composed of trifluoroacetyl chloride (TFAC); collecting the distillate from the column, which contains the azeotrope or azeotropic-like composition; contacting the distillate from the distillation column with a third solid adsorbent; and collecting the product stream from the third solid adsorbent, which is substantially composed of trifluoroacetyl chloride (TFAC).

[0187] Aspect 31 is the method according to any one of aspects 24, 25, 27 to 30 or 8 to 21, wherein the bottom product contains about 100 ppm or less of sulfur dioxide (SO2).

[0188] Aspect 32 is the method according to any one of Aspects 24 or 8 to 21, the method further comprising the steps of: contacting a feed stream containing a mixture of trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) with a solid adsorbent or a mixture of two or more solid adsorbents; and collecting a product stream, the product stream consisting substantially of trifluoroacetyl chloride (TFAC).

[0189] Aspect 33 is the method according to any one of aspects 24, 32 or 8 to 21, the method according to claim 11, wherein the solid adsorbent comprises one or more of molecular sieves, carbon molecular sieves, zeolite powder, silica gel, activated alumina, activated carbon, and combinations thereof.

[0190] Aspect 34 is the method according to aspect 33, wherein the solid adsorbent is a carbon molecular sieve.

[0191] Aspect 35 is a method for removing sulfur dioxide (SO2) from a mixture containing trifluoroacetyl iodine (TFAI), the method comprising at least one of distillation, adsorption, or a combination thereof.

[0192] Aspect 36 is a method according to any one of Aspects 35 or 8 to 21, the method comprising: conveying a stream containing trifluoroacetyl iodine (TFAI), hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2) and hydrogen iodide (HI) to a first distillation column to provide a first overhead product and a first bottom product; conveying the overhead product to a second distillation column to provide a second overhead product and a second bottom product; and conveying the second bottom product to an adsorption column to provide a product stream containing trifluoroacetyl chloride (TFAC).

[0193] Aspect 37 is the method according to any one of aspects 35, 36 or 8 to 21, wherein the adsorption tower comprises one or more of molecular sieves, carbon molecular sieves, zeolite powder, silica gel, activated alumina, activated carbon, and combinations thereof.

[0194] Aspect 38 is the method according to aspect 37, wherein the adsorption tower comprises a carbon molecular sieve.

[0195] Aspect 39 is the method according to any one of Aspects 24 to 38, wherein the feed stream containing trifluoroacetyl iodine (TFAI), hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) comprises sulfur dioxide (SO2) in an amount of 250 ppm or less. Aspect 40 is the method according to aspect 39, the method comprising: feeding a stream containing trifluoroacetyl iodine (TFAI), hydrogen chloride (HCl), hydrogen iodide (HI), trifluoroacetyl chloride (TFAC), and sulfur dioxide (SO2) to a first distillation column to provide a first overhead product and a first bottom product; feeding the first bottom product to a second distillation column to provide a second overhead product and a second bottom product; and feeding the second bottom product to a third distillation column to provide a third overhead product containing trifluoroacetyl chloride (TFAC) and sulfur dioxide (SO2) and a third bottom product containing trifluoroacetyl iodine (TFAI).

Claims

1. A method for removing sulfur dioxide (SO2) as an impurity in a process for producing trifluoroacetyl iodine (TFAI), the method comprising: A reactant stream containing trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and sulfur dioxide (SO2) is reacted to produce a stream containing trifluoroacetyl iodide (TFAI) and hydrogen chloride (HCl), unreacted trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and sulfur dioxide (SO2). Distillation of the feed stream; The first column overhead stream containing hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) is recovered. Recover the first bottom product containing TFAI; and The feed stream is fed to an adsorption tower before and / or after the distillation step to reduce the amount of sulfur dioxide (SO2) in the feed stream.

2. The method of claim 1, wherein the delivery step occurs after the reaction step and before the distillation step.

3. The method according to claim 1 or 2, wherein the adsorption tower comprises one or more of molecular sieves, carbon molecular sieves, zeolite powder, silica gel, activated alumina, activated carbon, and combinations thereof.

4. The method according to claim 3, wherein the adsorption tower comprises a carbon molecular sieve.

5. The method of claim 1, wherein the delivery step occurs after the distillation step.

6. The method according to any one of claims 1-5, the method further comprising the following steps: The first overhead stream containing hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) is distilled to provide a second overhead stream containing hydrogen chloride (HCl) and a second bottom product containing trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI).

7. The method according to claim 6, the method further comprising feeding trifluoroacetyl chloride (TFAC) to the reaction step via a recirculated feed stream.

8. The method according to claim 7, wherein the concentration of sulfur dioxide (SO2) in the recirculated stream is less than 50 ppm.

9. The method according to claim 7, wherein the concentration of sulfur dioxide (SO2) in the recirculated feed stream is less than 10 ppm.

10. The method of claim 6, further comprising conveying a second bottom product to an adsorption tower to reduce the amount of sulfur dioxide (SO2) in the second bottom product.

11. The method according to any one of claims 1-10, the method further comprising reacting TFAI to form trifluoroiodomethane (CF3I).

12. A method for removing sulfur dioxide (SO2) as an impurity in a process for producing trifluoroacetyl iodine (TFAI), the method comprising: A reactant stream containing trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and sulfur dioxide (SO2) is reacted to produce a product stream containing trifluoroacetyl iodide (TFAI) and hydrogen chloride (HCl), unreacted trifluoroacetyl chloride (TFAC), hydrogen iodide (HI), and sulfur dioxide (SO2); and The product stream is fed to an adsorption tower to reduce the amount of sulfur dioxide (SO2) in the product stream.

13. The method according to claim 12, wherein the adsorption tower comprises one or more of molecular sieves, carbon molecular sieves, zeolite powder, silica gel, activated alumina, activated carbon, and combinations thereof.

14. The method according to claim 12, further comprising the following steps: Distillation product stream; The first column overhead stream containing hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) is recovered. Recover the first bottom product containing TFAI; and The first overhead stream containing hydrogen chloride (HCl), trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI) is distilled to provide a second overhead stream containing hydrogen chloride (HCl) and a second bottom product containing trifluoroacetyl chloride (TFAC), sulfur dioxide (SO2), and hydrogen iodide (HI).

15. The method of claim 14, wherein the delivery step precedes the distillation step.

16. The method of claim 14, wherein the delivery step follows the distillation step.

17. The method of claim 12, further comprising feeding trifluoroacetyl chloride (TFAC) to the reaction step via a recirculated feed stream.

18. The method of claim 17, wherein the concentration of sulfur dioxide (SO2) in the recirculated stream is less than 50 ppm.

19. The method of claim 17, wherein the concentration of sulfur dioxide (SO2) in the recirculated stream is less than 10 ppm.

20. The method according to any one of claims 12-19, the method further comprising reacting TFAI to form trifluoroiodomethane (CF3I).

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