Compositions

Abstract

An azeotropic or near-azeotropic composition is disclosed consisting essentially of chloromethane (R-40) and hydrogen fluoride (HF). The composition may be used in the preparation of difluoromethane o

Description

The present invention relates to azeotropic or near-azeotropic compositions comprising hydrogen fluoride (HF) and chloromethane (R-40; CH3CI) along with uses of such compositions. Background The listing or discussion of a prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge. Dichloromethane (R-30; CH2CI2) may be produced by the hydrochlorination of methanol to chloromethane (R-40; CH3CI), followed by the reaction of the chloromethane with chlorine to produce R-32. Unreacted R-40 is present as an impurity, along with the trichloromethane (R-20; CHCI3) and tetrachloromethane (R-10; CCI4) by-products, in the R-32 product. Difluoromethane (R-32; CH2F2) is a hydrofluorocarbon which is used individually or in admixture with other hydrofluorocarbon or hydrofluoroolefin compounds as a refrigerant. R-32 is typically produced from the hydrofluorination of dichloromethane (R-30; CH2CI2), via the intermediate chlorofluoromethane (R-31; CH2CIF), in the liquid phase using a fluorination catalyst such as antimony pentachloride catalyst (SbCk). R-32 may also be produced from the hydrofluorination of R-30 in the vapour phase. Following the hydrofluorination of R-30, the crude reaction product comprises, in addition to R-32, excess unreacted HF, unreacted R-40 which was present as a feedstock impurity, and the unreacted intermediate R-31. For the sake of process efficiency, it is desirable that the R-31 is separated from the crude produce stream and recycled to the dehydrofluorination reactor so that it may be converted to R-32. It is not, however, desirable that the R-40 feedstock impurity is recycled to the dehydrofluorination reactor since it would have the potential to accumulate in the system. Furthermore, it is desirable that R-40 is separated from the R-32 product, due to its toxicity. Conventionally, distillation is used to separate HF, R-32, R-40 and R-31 in the crude product stream, based on their respective boiling points of 20°C, -52 °C, -24 °C and -9 °C. However, it would be desirable to be able to provide improved separation of the crude product stream. The present invention addresses the above and other deficiencies, and the above needs, by the provision of an azeotropic or near-azeotropic composition comprising R-40 and HF. Such compositions will be referred to hereinafter as “the compositions of the (present) invention”. The present inventors have surprisingly found the existence of a minimum boiling heteroazeotrope between R-40 and HF. Such an azeotropic and near-azeotropic compositions have a lower boiling point than R-40 and, therefore, are easier to separate from R-31 by, for example, distillation. Furthermore, the heteroazeotropic nature of the azeotrope between R-40 and HF is such that R-40 and HF can be subsequently separated from each other by liquid-liquid separation (e.g. in a decanter). Compositions and Processes of the Invention According to a first aspect of the invention, there is provided an azeotropic or near-azeotropic composition comprising chloromethane (R-40) and hydrogen fluoride (HF). The azeotropic or near-azeotropic composition of the invention preferably consists essentially of R-40 and HF. The composition of the invention more preferably consists of R-40 and HF. The azeotropic or near-azeotropic composition of the invention is preferably a heteroazeotropic or near-heteroazeotropic composition. By azeotrope or azeotropic composition, we mean a preferably binary composition which at vapour-liquid equilibrium has the same composition in both the liquid and vapour phase, and whose boiling point is lower than that of either of the pure components. By near-azeotrope or near-azeotropic composition (e.g. a near-azeotropic composition of R-40 and HF), we mean a composition that behaves similarly to an azeotrope composition (i.e. the composition has constant boiling characteristics or a tendency not to fractionate upon boiling), but may not have all of the properties of an azeotrope, for example binary liquid compositions whose vapour pressure is above that of the pure component with the lower boiling point when measured at equivalent temperature, but whose equilibrium vapour composition may differ from the liquid composition. In essence, at a given pressure, a boiling azeotrope or near-azeotrope composition has substantially the same constituent proportions in the vapour phase as in the boiling liquid phase. This means that no (or substantially no) fractionation of the components in the liquid composition takes place. By heteroazeotrope, we mean an azeotrope where the vapour phase coexists with two liquid phases. In other words, a heteroazeotropic composition exhibits two liquid phases. By the phrase “consisting essentially of’, we mean the azeotropic or near-azeotropic composition may contain further components than those stated, provided that such further components do not materially affect the azeotropic or near-azeotropic properties of the composition. The azeotropic or near-azeotropic composition of the invention may comprise, consist essentially of, or preferably consist of, from about 15 mol% to about 99 mol% chloromethane (R-40) and from about 85 mol% to about 1 mol% hydrogen fluoride (HF). Preferably, the azeotropic or near-azeotropic composition of the invention comprises, consists essentially of, or preferably consists of, from about 20 mol% to about 98 mol% R-40 and from about 80 mol% to about 2 mol% HF. The azeotropic or near-azeotropic composition of the invention is preferably azeotropic or near-azeotropic at temperatures of from about -20°C to about +70°C. The azeotropic or near-azeotropic composition of the invention is preferably azeotropic or near-azeotropic at pressures of from about 1.0 bara to about 20 bara. In a more preferred embodiment, the azeotropic or near-azeotropic composition of the invention comprises, consists essentially of, or preferably consists of: - from about 20 mol% to about 86 mol% R-40 and from about 80 mol% to about 14 mol% HF, preferably, from about 22 mol% to about 78 mol% R-40 and from about 78 mol% to about 22 mol% HF, more preferably, from about 24 mol% to about 69 mol% R-40 and from about 76 mol% to about 31 mol% HF, - even more preferably, from about 26 mol% to about 59 mol% R-40 and from about 74 mol% to about 41 mol% HF, yet more preferably, from about 28 mol% to about 37 mol% R-40 and from about 72 mol% to about 63 mol% HF; most preferably, about 30 mol% R-40 and about 70 mol% HF. In the more preferred embodiment, the azeotropic or near-azeotropic composition of the invention may be azeotropic or near-azeotropic at temperatures of from about -20°C to about +70°C, preferably from about -20°C to about +40°C, more preferably from temperatures of from about -20°C to about 0°C, even more preferably from temperature of from about -20°C to about -10°C. In the more preferred embodiment, the azeotropic or near-azeotropic composition of the invention may be azeotropic or near-azeotropic at pressures of from about 1.0 bara to about 20 bara, preferably from about 1.0 bara to about 10 bara, more preferably from about 1.1 bara to about 5.0 bara, even more preferably from about 1.1 bara to about 2.0 bara. In an alternative more preferred embodiment, the azeotropic or near-azeotropic composition of the invention comprises, consists essentially or, or preferably consists of: from about 25 mol% to about 98 mol% R-40 and from about 75 mol% to about 2 mol% HF, preferably, from about 30 mol% to about 86 mol% R-40 and from about 70 mol% to about 14 mol% HF, - more preferably, from about 37 mol% to about 84 mol% R-40 and from about 63 mol% to about 16 mol% HF, even more preferably, from about 59 mol% to about 82 mol% R-40 and from about 41 mol% to about 18 mol% HF, yet more preferably, from about 69 mol% to about 80 mol% R-40 and from about 31 mol% to about 20 mol% HF; - most preferably, about 78 mol% R-40 and about 22 mol% HF. In the more preferred embodiment, the azeotropic or near-azeotropic composition of the invention may be azeotropic or near-azeotropic at temperatures of from about -20°C to about +70°C, preferably from about -20°C to about +20°C, more preferably from temperatures of from about -10°C to about +10°C, even more preferably from temperature of from about 0°C. In the more preferred embodiment, the azeotropic or near-azeotropic composition of the invention may be azeotropic or near-azeotropic at pressures of from about 1.0 bara to about 20 bara, preferably from about 1.5 bara to about 10 bara, more preferably from about 1.8 bara to about 5.0 bara, even more preferably from about 2.0 bara to about 3.0 bara, such as from about 2.4 bara to about 2.7 bara. In an alternative more preferred embodiment, the azeotropic or near-azeotropic composition of the invention comprises, consists essentially of, or preferably consists of: from about 45 mol% to about 97 mol% R-40 and from about 55 mol% to about 3 mol% HF, preferably, from about 59 mol% to about 96 mol% R-40 and from about 41 mol% to about 4 mol% HF, - more preferably, from about 69 mol% to about 93 mol% R-40 and from about 31 mol% to about 7 mol% HF, even more preferably, from about 78 mol% to about 90 mol% R-40 and from about 22 mol% to about 10 mol% HF, most preferably, about 86 mol% R-40 and about 14 mol% HF. In the more preferred embodiment, the azeotropic or near-azeotropic composition of the invention may be azeotropic or near-azeotropic at temperatures of from about -20°C to about +70°C, preferably from about -10°C to about +70°C, more preferably from temperatures of from about 0°C to about +70°C, even more preferably from temperature of from about 10°C to about +70°C. In the more preferred embodiment, the azeotropic or near-azeotropic composition of the invention may be azeotropic or near-azeotropic at pressures of from about 1.0 bara to about 20 bara, preferably from about 2.0 bara to about 19 bara, more preferably from about 3.0 bara to about 18.7 bara. When used herein in relation to a specific value (such as an amount), the term “about” (or similar terms, such as “approximately”) will be understood as indicating that such values may vary by up to 10% (particularly, up to 5%, such as up to 1%) of the value defined. It is contemplated that, at each instance, such terms may be replaced with the notation “±10%”, or the like (or by indicating a variance of a specific amount calculated based on the relevant value). It is also contemplated that, at each instance, such terms may be deleted. In an even more preferred embodiment, the azeotropic or near-azeotropic composition of the invention comprises, consists essentially of, or preferably consists of from about 20 mol% to about 37 mol% R-40 and from about 80 mol% to about 63 mol% HF, wherein the composition is azeotropic or near-azeotropic at a temperature of about -20°C and a pressure of about 1.24 bara. Most preferably, the composition consists essentially of, or preferably consists of, about 30 mol% R-40 and about 70 mol% HF, wherein the composition is azeotropic at a temperature of about -20°C and a pressure of about 1.24 bara. In an alternative even more preferred embodiment, the azeotropic or near-azeotropic composition of the invention comprises, consists essentially of, or preferably consists of from about 20 mol% to about 37 mol% R-40 and from about 80 mol% to about 63 mol% HF, wherein the composition is azeotropic or near-azeotropic at a temperature of about -10°C and a pressure of about 1.81 bara. Most preferably, the composition consists essentially of, or preferably consists of, about 30 mol% R-40 and about 70 mol% HF, wherein the composition is azeotropic at a temperature of about -10°C and a pressure of about 1.81 bara. In an alternative even more preferred embodiment, the azeotropic or near-azeotropic composition of the invention comprises, consists essentially of, or preferably consists of from about 59 mol% to about 86 mol% R-40 and from about 41 mol% to about 14 mol% HF, wherein the composition is azeotropic or near-azeotropic at a temperature of about 0°C and a pressure of about 2.60 bara. Most preferably, the composition consists essentially of, or preferably consists of, about 78 mol% R-40 and about 22 mol% HF, wherein the composition is azeotropic at a temperature of about -0°C and a pressure of about 2.60 bara. In an alternative even more preferred embodiment, the azeotropic or near-azeotropic composition of the invention comprises, consists essentially of, or preferably consists of from about 78 mol% to about 99 mol% R-40 and from about 22 mol% to about 1 mol% HF, wherein the composition is azeotropic or near-azeotropic at a temperature of about 10°C and a pressure of about 3.66 bara. Most preferably, the composition consists essentially of, or preferably consists of, about 86 mol% R-40 and about 14 mol% HF, wherein the composition is azeotropic at a temperature of about 10°C and a pressure of about 3.66 bara. In an alternative even more preferred embodiment, the azeotropic or near-azeotropic composition of the invention comprises, consists essentially of, or preferably consists of from about 78 mol% to about 99 mol% R-40 and from about 22 mol% to about 1 mol% HF, wherein the composition is azeotropic or near-azeotropic at a temperature of about 20°C and a pressure of about 5.03 bara. Most preferably, the composition consists essentially of, or preferably consists of, about 86 mol% R-40 and about 14 mol% HF, wherein the composition is azeotropic at a temperature of about 20°C and a pressure of about 5.03 bara. In an alternative even more preferred embodiment, the azeotropic or near-azeotropic composition of the invention comprises, consists essentially of, or preferably consists of from about 78 mol% to about 99 mol% R-40 and from about 22 mol% to about 1 mol% HF, wherein the composition is azeotropic or near-azeotropic at a temperature of about 30°C and a pressure of about 6.77 bara. Most preferably, the composition consists essentially of, or preferably consists of, about 86 mol% R-40 and about 14 mol% HF, wherein the composition is azeotropic at a temperature of about 30°C and a pressure of about 6.77 bara. In an alternative even more preferred embodiment, the azeotropic or near-azeotropic composition of the invention comprises, consists essentially of, or preferably consists of from about 78 mol% to about 99 mol% R-40 and from about 22 mol% to about 1 mol% HF, wherein the composition is azeotropic or near-azeotropic at a temperature of about 40°C and a pressure of about 8.92 bara. Most preferably, the composition consists essentially of, or preferably consists of, about 86 mol% R-40 and about 14 mol% HF, wherein the composition is azeotropic at a temperature of about 40°C and a pressure of about 8.92 bara. In an alternative even more preferred embodiment, the azeotropic or near-azeotropic composition of the invention comprises, consists essentially of, or preferably consists of from about 78 mol% to about 99 mol% R-40 and from about 22 mol% to about 1 mol% HF, wherein the composition is azeotropic or near-azeotropic at a temperature of about 50°C and a pressure of about 11.55 bara. Most preferably, the composition consists essentially of, or preferably consists of, about 86 mol% R-40 and about 14 mol% HF, wherein the composition is azeotropic at a temperature of about 50°C and a pressure of about 11.55 bara. In an alternative even more preferred embodiment, the azeotropic or near-azeotropic composition of the invention comprises, consists essentially of, or preferably consists of from about 78 mol% to about 99 mol% R-40 and from about 22 mol% to about 1 mol% HF, wherein the composition is azeotropic or near-azeotropic at a temperature of about 60°C and a pressure of about 14.72 bara. Most preferably, the composition consists essentially of, or preferably consists of, about 86 mol% R-40 and about 14 mol% HF, wherein the composition is azeotropic at a temperature of about 60°C and a pressure of about 14.72 bara. In an alternative even more preferred embodiment, the azeotropic or near-azeotropic composition of the invention comprises, consists essentially of, or preferably consists of from about 78 mol% to about 99 mol% R-40 and from about 22 mol% to about 1 mol% HF, wherein the composition is azeotropic or near-azeotropic at a temperature of about 70°C and a pressure of about 18.51 bara. Most preferably, the composition consists essentially of, or preferably consists of, about 86 mol% R-40 and about 14 mol% HF, wherein the composition is azeotropic at a temperature of about 70°C and a pressure of about 18.51 bara. In a second aspect, the invention provides a process for separating R-40 and HF in the azeotropic or near-azeotropic composition as hereinbefore described (i.e. the first aspect of the invention including all embodiments and particular features thereof), wherein the separating is conducted by pressure swing distillation. In other words, the process comprises the step of separating R-40 and HF via the use of pressure swing apparatus. Such pressure swing apparatus set-ups may comprise at least two columns, which may be operated sequentially at different pressures. Similarly, the columns may be operated sequentially at two different temperatures. A first column A is preferably operated at a pressure of from about 1 to about 20 bara, such as from about 2 to about 20 bara, more preferably from about 5 to about 20 bara, for example about 10 bara. A second column B is preferably operated at a pressure of from about 0.5 to about 10 bara, such as from about 0.5 to about 5 bara, more preferably from about 0.5 to about 2 bara, for example about 1 bara. In the second aspect of the invention, an azeotropic or near-azeotropic feed composition (Fi) of the invention comprising R-40 and HF is preferably fed into column A. Such compositions may comprise, or preferably consist of, about 1 mol% to about 85 mol% R-40 and from about 15 mol% to about 99 mol% HF, advantageously from about 1 mol% to about 40 mol% R-40 and from about 60 mol% to about 99 mol% HF, such as about 1 mol% to about 20 mol% R-40 and from about 80 mol% to about 99 mol% HF, for example about 1.2 mol% to about 10 mol% R-40 and from about 90 mol% to about 98.8 mol% HF, preferably about 1.4 mol% to about 5 mol% R-40 and from about 95 mol% to about 98.6 mol% HF, even more preferably from about 1.5 mol% to about 3 mol% R-40 and from about 97 mol% to about 98.5 mol% HF, such as from about 1.5 mol% to about 2.5 mol% R-40 and from about 97.5 mol% to about 98.5 mol% HF. Advantageously, the Fi composition consists of less than 3 mol% R-40 and more than 97 mol% HF. On entering column A, HF is separated from the Fi composition. As such, HF may be recovered from column A yielding a HF rich composition (Di) comprising greater than about 90 mol% HF, such as greater than about 95 mol% HF, preferably greater than 99 mol% HF, and an azeotropic or near-azeotropic composition (Ci) comprising R-40 and HF in a molar ratio that is richer in R-40 than Fi. Preferably, composition Di is recovered from column A at the higher temperature region of the column. On recovering the composition Di from column, a preferably azeotropic or near-azeotropic composition Ci comprising R-40 and HF is fed into column B, wherein the Ci composition is separated into two further fluid compositions, wherein R-40 is separated from the azeotrope composition to yield a composition (D2) comprising greater than about 90 mol% R-40, such as greater than about 95 mol% R-40, preferably greater than 99 mol% R-40, and an azeotropic or near-azeotropic composition (C2) comprising R-40 and HF in a molar ratio that is richer in HF than Ci. Preferably, composition D2 is recovered from column B at the higher temperature region of the column. The recovery of compositions Di and Ci from column A may occur simultaneously or sequentially. Preferably, the recovery of compositions Di and Ci occurs simultaneously. On recovering the composition D2 from column B, a preferably azeotropic or near-azeotropic composition (C2) consisting of R-40 and HF may be recovered at the opposite end of the column. As R-40 has been recovered from composition Ci, the C2 composition is richer in HF than Ci. Preferably, such compositions comprise, or preferably consist of, about 75 mol% to about 99 mol% R-40 and from about 1 mol% to about 25 mol% HF, such as from about 75 mol% to about 90 mol% R-40 and from 10 mol% to about 25 mol% HF, for example from about 75 mol% to about 85 mol% R-40 and from about 15 mol% to about 25 mol% HF. Preferably, such compositions comprise, or preferably consist of, from about 75 mol% to about 80 mol% R-40 and from about 20 mol% to about 25 mol% HF. The recovery of compositions D2 and C2 from column B may occur simultaneously or sequentially. Preferably, the recovery of compositions D2 and C2 occurs simultaneously. In an embodiment, upon recovery of the composition C2from column B, this composition may be recycled back into column A. Preferably, this process is, therefore, continuous. Although it is preferred that the separation of composition Fi is via first entering column A then column B, it is envisaged that the process may be reversed and the azeotropic or near-azeotropic composition may be subjected to the separation process in column B first before being subjected to the separation process in column A. In a third aspect of the invention, there is provided a composition comprising the azeotropic or near-azeotropic composition as hereinbefore defined (i.e. the first aspect of the invention, including all embodiments and particular features thereof). Preferably, the composition of the third aspect of the invention comprises, in addition to the azeotropic or near-azeotropic composition, a further component selected from the list consisting of: dichloromethane (R-30), difluoromethane (R-32), chlorofluoromethane (R-31) and mixtures thereof. More preferably, the composition of the third aspect of the invention comprises chlorofluoromethane (R-31). Preferably, the composition of the third aspect of the invention comprises the azeotropic or near azeotropic composition in an amount of from about 1 mol% to about 90 mol%, such as from about 1 mol% to about 50 mol%, more preferably from about 1 mol% to about 10 mol%. In a fourth aspect of the invention, there is provided a process for removing R-40 from a mixture containing R-40 and at least one further component, which comprises adding or removing HF to the mixture in an amount sufficient to form an azeotropic or near-azeotropic composition as defined hereinbefore (i.e. in the first aspect of the invention, including all embodiments and particular features thereof), and thereafter separating the azeotropic or near-azeotropic composition from the at least one further component. Preferably, the further component of the fourth aspect of the invention is selected from the list consisting of: dichloromethane (R-30), difluoromethane (R-32), chlorofluoromethane (R-31) and mixtures thereof. More preferably, the further component comprises chlorofluoromethane (R-31). Preferably, the separating of the azeotropic or near-azeotropic composition from the at least one further component is conducted by distillation. In a fifth aspect of the invention, there is provided a process for preparing difluoromethane (R-32), comprising the steps of: (i) hydrofluorinating a first composition comprising dichloromethane (R-30) to produce a second composition comprising difluoromethane (R-32) and R-40; (ii) adding or removing HF to the second composition in an amount sufficient to form an azeotropic or near-azeotropic composition as hereinbefore defined (i.e. in the first aspect of the invention, including all embodiments and particular features thereof); and (iii) separating the azeotropic or near-azeotropic composition from the R-32; and (iv) optionally, separating the R-40 and HF in the azeotropic or near-azeotropic composition using the process as hereinbefore defined (i.e. in the second aspect of the invention, including all embodiments and particular features thereof). Preferably, the separating of the azeotropic or near-azeotropic composition from the R-32 is conducted by distillation. Embodiments of the present invention will now be described with reference to the following drawings: Figures 1 to 10 show the results obtained when measuring the vapour pressure of varying compositions of HF and R-40 at temperatures of-20°C, -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C and 70°C. Figure 11 shows a pressure swing apparatus set-up, which is suitable for the separation of azeotropic or near-azeotropic compositions of the invention. The present invention provides an azeotropic or near-azeotropic composition comprising R-40 and HF. Without wishing to be bound by theory, the existence of an azeotropic or near-azeotropic composition is generally dependent on temperature, pressure and the ratio of components in the composition. By varying the temperature, pressure and composition, an azeotrope or near-azeotropic composition of the invention may occur at any point between these values. The components of azeotropic or near-azeotropic compositions may be separated via the use of a pressure swing distillation apparatus. Such set-ups typically comprise one or more distillation columns operated at temperatures and pressures specific to the azeotropic or near-azeotropic composition of interest. By fine tuning the temperature and pressure of the pressure swing distillation column(s), an azeotrope composition may be distilled from the column, wherein, depending on the pressure and temperature of the column, the resulting distillate may comprise the components of the azeotropic composition in different molar ratios than that of the original feed composition. This, therefore, can result in the liquid phase that is left in the column being richer in one component of the azeotropic composition than the other. In some cases, the liquid phase may be almost 100 mol% of the component left in the liquid phase. An exemplary pressure swing apparatus set-up for the separation of azeotropic or near-azeotropic compositions of the invention is provided in Figure 11. This set-up comprises two columns (A and B), which are operated at different temperatures and pressures. Preferably, column B is operated at a lower pressure to the second column A. However, it is envisaged that column A may be operated at a lower pressure to column B. Similarly, column A is preferably operated at higher temperatures to column B. However, column B may just as easily be operated at higher temperatures to column A if the process requires. In a specific embodiment, and with reference to Figure 11, a feed composition (Fi) comprising about 1 mol% to about 80 mol% R-40 and about 20 mol% to about 99 mol% HF is fed into column A, which is operated at a pressure (Pa) of about 10 bara and temperatures of about 98 °C at the bottom (Tai) of the column and about 45 °C at the top (Ta2). Under these conditions, the Fi composition undergoes partial distillation, wherein a distillate composition (Ci) is distilled from the top of the column leaving a HF rich residue (Di). After this first separation process, the Ci composition comprises about 90 mol% R-40 and about 10 mol% HF. Whereas, the Di residue composition comprises about 99 mol% to about 100 mol% HF. The highly pure Di composition is removed from the column and collected, and the Ci composition is fed into column B, which is operated at a pressure (Pb) of about 1 bara and temperatures of about -24 °C at the bottom (Tbi) of the column and -25 °C at the top (Tbz). Under such conditions, the Ci composition undergoes distillation to provide a distillate composition (C2) comprising about 75 mol% R-40 and about 25 mol% HF, which results in a R-40 rich residue (D2) remaining in the column. This D2 residue typically comprises about 99 mol% to about 100 mol% R-40. After the separation process in column B, the highly pure D2 composition is removed from the column and collected, and the distillate composition C2 is recycled back into column A to repeat the process. Examples Example 1 A binary azeotrope between R-40 and HF was identified by a study of the vapour-liquid equilibrium of binary mixtures over a temperature range of -20°C to +70°C using a constant volume apparatus. The experimental data were measured in a static constant volume apparatus consisting of a vessel of precisely known internal volume located in a temperature-controlled metal block. A magnetic stirring device was located inside the vessel. Thermal fluid was passed through the block to allow precise control of temperature inside the vessel. The cell was evacuated then known amounts of compositions of R-40 and HF were charged to the cell. The temperature of the cell was then varied to temperatures between -20°C and +70°C. At each step the cell temperature and pressure were logged and recorded when stable conditions were reached. The phase behaviour of these compositions at exemplary temperatures is shown in Tables 1 and 2, and illustrated in Figures 1 to 10. Table 1: P-T-X of R-40 / HF for T = -20 to +20 °C Mole fraction R-40 Mole fraction HF Pressure (bara) T = -20°c T = -10°C T = 0°C T= 10°C T = 20°C 0.000 1.000 0.19 0.31 0.48 0.71 1.04 0.023 0.977 0.56 0.79 1.09 1.47 1.96 0.052 0.948 0.84 1.19 1.63 2.17 2.85 0.100 0.900 1.07 1.53 2.11 2.84 3.74 0.202 0.798 1.21 1.75 2.47 3.37 4.51 0.302 0.698 1.24 1.81 2.57 3.54 4.76 0.369 0.631 1.21 1.80 2.57 3.57 4.82 0.593 0.407 1.22 1.80 2.59 3.62 4.94 0.690 0.310 1.21 1.80 2.60 3.65 4.99 0.778 0.222 1.21 1.80 2.60 3.66 5.02 0.861 0.139 1.18 1.78 2.59 3.66 5.03 1.000 0.000 1.15 1.73 2.53 3.58 4.92 Table 2: P-T-X of R-40 / HF for T = 30 to 70 °C Mole fraction R-40 Mole fraction HF Pressure (bara) T = 30°c T = 40°C T = 50°C T = 60°C T = 70°C 0.000 1.000 1.47 2.03 2.77 3.70 4.89 0.023 0.977 2.58 3.35 4.30 5.47 6.90 0.052 0.948 3.67 4.67 5.87 7.31 9.04 0.100 0.900 4.82 6.12 7.67 9.50 11.67 0.202 0.798 5.89 7.58 9.59 11.97 14.78 0.302 0.698 6.27 8.13 10.37 13.05 16.23 0.369 0.631 6.38 8.30 10.63 13.45 16.83 0.593 0.407 6.61 8.68 11.21 14.27 17.94 0.690 0.310 6.69 8.81 11.39 14.51 18.23 0.778 0.222 6.74 8.87 11.49 14.66 18.44 0.861 0.139 6.77 8.92 11.55 14.72 18.51 1.000 0.000 6.60 8.68 11.20 14.22 17.81 A pressure maxima demonstrates the presence of a minimum boiling azeotrope. Figure 1 shows that a binary azeotrope / near-azeotropic composition exists between R-40 and HF at a temperature of -20°C and a pressure of 1.24 bara, wherein R-40 is present in an amount of about 20 mol% to about 37 mol% and HF is present in an amount of from about 80 mol% to about 63 mol%. Figure 2 shows that a binary azeotrope / near-azeotropic composition exists between R-40 and HF at a temperature of -10°C and a pressure of 1.81 bara, wherein R-40 is present in an amount of about 20 mol% to about 37 mol% and HF is present in an amount of from about 80 mol% to about 63 mol%. Figure 3 shows that a binary azeotrope / near-azeotropic composition exists between R-40 and HF at a temperature of 0°C and a pressure of 2.60 bara, wherein R-40 is present in an amount of about 59 mol% to about 86 mol% and HF is present in an amount of from about 14 mol% to about 41 mol%. Figure 4 shows that a binary azeotrope / near-azeotropic composition exists between R-40 and HF at a temperature of 10°C and a pressure of 3.66 bara, wherein R-40 is present in an amount of about 78 mol% to about 99 mol% and HF is present in an amount of from about 1 mol% to about 22 mol%. Figure 5 shows that a binary azeotrope / near-azeotropic composition exists between R-40 and HF at a temperature of 20°C and a pressure of 5.03 bara, wherein R-40 is present in an amount of about 78 mol% to about 99 mol% and HF is present in an amount of from about 1 mol% to about 22 mol%. Figure 6 shows that a binary azeotrope / near-azeotropic composition exists between R-40 and HF at a temperature of 30°C and a pressure of 6.77bara, wherein R-40 is present in an amount of about 78 mol% to about 99 mol% and HF is present in an amount of from about 1 mol% to about 22 mol%. Figure 7 shows that a binary azeotrope / near-azeotropic composition exists between R-40 and HF at a temperature of 40°C and a pressure of 8.92 bara, wherein R-40 is present in an amount of about 78 mol% to about 99 mol% and HF is present in an amount of from about 1 mol% to about 22 mol%. Figure 8 shows that a binary azeotrope / near-azeotropic composition exists between R-40 and HF at a temperature of 50°C and a pressure of 11.55 bara, wherein R-40 is present in an amount of about 78 mol% to about 99 mol% and HF is present in an amount of from about 1 mol% to about 22 mol%. Figure 9 shows that a binary azeotrope / near-azeotropic composition exists between R-40 and HF at a temperature of 60°C and a pressure of 14.72 bara, wherein R-40 is present in an amount of about 78 mol% to about 99 mol% and HF is present in an amount of from about 1 mol% to about 22 mol%. Figure 10 shows that a binary azeotrope / near-azeotropic composition exists between R-40 and HF at a temperature of 70°C and a pressure of 18.51 bara, wherein R-40 is present in an amount of about 78 mol% to about 99 mol% and HF is present in an amount of from about 1 mol% to about 22 mol%. Preferences and options for a given aspect, feature or parameter of the invention should, unless the context indicates otherwise, be regarded as having been disclosed in combination with any and all preferences and options for all other aspects, features and parameters of the invention.

Claims

1. An azeotropic or near-azeotropic composition consisting essentially of chloromethane(R-40) and hydrogen fluoride (HF).

2. The composition according to Claim 1 consisting essentially of from about 15 mol% to about 99 mol% chloromethane (R-40) and from about 85 mol% to about 1 mol% hydrogen fluoride (HF).

3. The composition according to Claim 2 consisting essentially of from about 20 mol% to about 98 mol% R-40 and from about 80 mol% to about 2 mol% HF.

4. The composition according any of the preceding claims, which is azeotropic or near-azeotropic at temperatures of from about -20°C to about +70°C.

5. The composition according to any one of the preceding claims, which is azeotropic or near-azeotropic at pressures of from about 1.0 bara to about 20 bara.

6. The composition according to Claim 3 consisting essentially of:from about 20 mol% to about 86 mol% R-40 and from about 80 mol% to about 14 mol% HF,preferably, from about 22 mol% to about 78 mol% R-40 and from about 78 mol% to about 22 mol% HF,- more preferably, from about 24 mol% to about 69 mol% R-40 and from about 76 mol% to about 31 mol% HF, even more preferably, from about 26 mol% to about 59 mol% R-40 and from about 74 mol% to about 41 mol% HF,yet more preferably, from about 28 mol% to about 37 mol% R-40 and from about 72 mol% to about 63 mol% HF;- most preferably, about 30 mol% R-40 and about 70 mol% HF.

7. The composition according to Claim 6, which is azeotropic or near-azeotropic attemperatures of from about -20°C to about +70°C, preferably from about -20°C to about +40°C, more preferably from temperatures of from about -20°C to about 0°C, even more preferably from temperature of from about -20°C to about -10°C.

8. The composition according to Claims 6 or 7, which is azeotropic or near-azeotropic at pressures of from about 1.0 bara to about 20 bara, preferably from about 1.0 bara to about 10 bara, more preferably from about 1.1 bara to about 5.0 bara, even more preferably from about 1.1 bara to about 2.0 bara.

9. The composition according to Claim 3 consisting essentially of:from about 25 mol% to about 98 mol% R-40 and from about 75 mol% to about 2 mol% HF,preferably, from about 30 mol% to about 86 mol% R-40 and from about 70 mol% to about 14 mol% HF,- more preferably, from about 37 mol% to about 84 mol% R-40 and from about 63 mol% to about 16 mol% HF, even more preferably, from about 59 mol% to about 82 mol% R-40 and from about 41 mol% to about 18 mol% HF, yet more preferably, from about 69 mol% to about 80 mol% R-40 and from about 31 mol% to about 20 mol% HF;- most preferably, about 78 mol% R-40 and about 22 mol% HF.

10. The composition according to Claim 9, which is azeotropic or near-azeotropic at temperatures of from about -20°C to about +70°C, preferably from about -20°C to about +20°C, more preferably from temperatures of from about -10°C to about +10°C, even more preferably from temperature of from about 0°C.

11. The composition according to Claims 9 or 10, which is azeotropic or near-azeotropic at pressures of from about 1.0 bara to about 20 bara, preferably from about 1.5 bara to about 10 bara, more preferably from about 1.8 bara to about 5.0 bara, even more preferably from about 2.0 bara to about 3.0 bara, such as from about 2.4 bara to about 2.7 bara.

12. The composition according to Claim 3 consisting essentially of:from about 45 mol% to about 97 mol% R-40 and from about 55 mol% to about 3 mol% HF,- preferably, from about 59 mol% to about 96 mol% R-40 and from about 41 mol% to about 4 mol% HF,more preferably, from about 69 mol% to about 93 mol% R-40 and from about 31 mol% to about 7 mol% HF,even more preferably, from about 78 mol% to about 90 mol% R-40 and from about 22 mol% to about 10 mol% HF,- most preferably, about 86 mol% R-40 and about 14 mol% HF.

13. The composition according to Claim 12, which is azeotropic or near-azeotropic at temperatures of from about -20°C to about +70°C, preferably from about -10°C to about +70°C, more preferably from temperatures of from about 0°C to about +70°C, even more preferably from temperature of from about 10°C to about +70°C.

14. The composition according to any one of the preceding claims, which is azeotropic or near-azeotropic at pressures of from about 1.0 bara to about 20 bara, preferably from about 2.0 bara to about 19 bara, more preferably from about 3.0 bara to about 18.7 bara.

15. The composition according to any of the preceding claims, wherein the composition exhibits two liquid phases.

16. The composition according to any of the preceding claims which consists of R-40 and HF in the stated amounts.

17. A process for separating R-40 and HF in the azeotropic or near-azeotropic composition as defined in any one of Claims 1 to 16, wherein the separating is conducted by pressure swing distillation.

18. The process according to Claim 17, wherein the pressure swing apparatus comprises a first column (A) and a second column (B) operated sequentially at different pressures.

19. The process according to Claim 18, wherein the column A is operated at a higher pressure to column B.

20. The process according to Claims 18 or 19, wherein column A is operated at a pressure of from about 1 to about 20 bara, such as from about 2 to about 20 bara, preferably from about 5 to about 20 bara, for example about 10 bara.

21. The process according to any one of Claims 18 to 20, wherein column B is operated at a pressure of from about 0.5 to about 10 bara, such as from about 0.5 to about 5 bara, preferably from about 0.5 to about 2 bara, for example about 1 bara.

22. The process according to any one of Claims 18 to 21, wherein the two columns are operated sequentially at different temperatures.

23. The process according to any one of Claims 18 to 22, wherein a composition (Fi) is fed into the process, wherein Fi comprises about 1 mol% to about 85 mol% R-40 and from about 15 mol% to about 99 mol% HF, advantageously from about 1 mol% to about 40 mol% R-40 and from about 60 mol% to about 99 mol% HF, such as about 1 mol% to about 20 mol% R-40 and from about 80 mol% to about 99 mol% HF, for example about 1.2 mol% to about 10 mol% R-40 and from about 90 mol% to about 98.8 mol% HF, preferably about 1.4 mol% to about 5 mol% R-40 and from about 95 mol% to about 98.6 mol% HF, even more preferably from about 1.5 mol% to about 3 mol% R-40 and from about 97 mol% to about 98.5 mol% HF, such as from about 1.5 mol% to about 2.5 mol% R-40 and from about 97.5 mol% to about 98.5 mol% HF.

24. The process according to any one of Claims 18 to 23, wherein the Fi composition is separated into two liquid compositions in column A, wherein HF is separated from the azeotrope composition to yield a composition (Di) comprising greater than about 90 mol% HF, such as greater than about 95 mol% HF, preferably greater than 99 mol% HF, and an azeotropic or near-azeotropic composition (Ci) comprising HF and R-40 in a molar ratio that is richer in R-40 than Fi.

25. The process according to any one of Claims 18 to 24, wherein Di is removed from the separating apparatus and Ci is fed into column B, wherein the Ci composition is separated into two further liquid compositions, wherein R-40 is separated from the azeotrope composition to yield a composition (D2) comprising greater than about 90 mol% R-40, such as greater than about 95 mol% R-40, preferably greater than 99 mol% R-40, and an azeotropic or near-azeotropic composition (C2) comprising HF and R-40 in a molar ratio that is richer in HF than Ci.

26. The process according to any one of Claims 18 to 25, wherein composition D2 is removed from the separating apparatus and composition C2 is recycled back into column A.

27. The process according to any one of Claims 18 to 26, wherein the process is continuous.

28. The process according to any one of Claims 18 to 27, wherein the azeotropic or near-azeotropic composition Fi is subjected to the separation process in column B first before being subjected to the separation process in column A.

29. A composition comprising the azeotropic or near-azeotropic composition as defined in any of Claims 1 to 16.

30. The composition according to Claim 29 comprising a further component selected from the list consisting of: dichloromethane (R-30), difluoromethane (R-32), chlorofluoromethane (R-31) and mixtures thereof; preferably wherein the composition comprises chlorofluoromethane (R-31).

31. A process for removing R-40 from a mixture containing R-40 and at least one further component, which comprises adding or removing HF to the mixture in an amount sufficient to form an azeotropic or near-azeotropic composition as defined in any of Claims 1 to 16, and thereafter separating the azeotropic or near-azeotropic composition from the at least one further component.

32. The process according to Claim 31 wherein the at least one further component is selected from the list consisting of: dichloromethane (R-30), difluoromethane (R-32), chlorofluoromethane (R-31) and mixtures thereof; preferably wherein the at least further component is chlorofluoromethane (R-31).

33. The process according to Claims 31 or 32, wherein the separating is conducted by distillation.

34. A process for preparing difluoromethane (R-32) comprising the steps of:(i) hydrofluorinating a first composition comprising dichloromethane (R-30) to produce a second composition comprising difluoromethane (R-32) and R-40;(ii) adding or removing HF to the second composition in an amount sufficient to form an azeotropic or near-azeotropic composition as defined in any of Claims 1 to 16; and(iii) separating the azeotropic or near-azeotropic composition from the R-32.

35. The process according to Claims 34, wherein the separating is conducted by distillation.

36. The process according to Claims 34 or 35, further comprising the step:5 (iv) separating the R-40 and HF in the azeotropic or near-azeotropic compositionusing the process as defined in any one of Claims 17 to 28.

37. Any novel composition, method or process as described herein, optionally with reference to the examples.

Images