Production of carbon tetrachloride by photochlorination of chloroform

Abstract

To provide industrial methods for efficient synthesis of carbon tetrachloride.SOLUTION: A method of producing carbon tetrachloride comprises the step of reacting chlorine with chloroform in the presence of electromagnetic radiation within a reaction mixture that includes the chlorine, the chloroform and carbon tetrachloride, where the concentration of chloroform is less than 5000 ppm by weight relative to the weight of the reaction mixture, where the reaction mixture includes at least the stoichiometric concentration of chlorine relative to chloroform, where the electromagnetic radiation creates chloride radicals, and where the reaction mixture is well mixed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 358,340, filed on July 5, 2016, the content of which is incorporated herein by reference.

[0002] Embodiments of the present invention relate to a method for producing carbon tetrachloride by photochlorination of chloroform.

Background Art

[0003] Carbon tetrachloride is a useful feedstock for the synthesis of many important commercial chemicals. In particular, carbon tetrachloride often serves as a basic feedstock in the production of chlorinated propane (used in the production of hydrofluoroolefins (HFOs)).

[0004] Originally, chloroform was reacted with chlorine to form carbon tetrachloride, but in most commercial processes, methane is chlorinated to produce carbon tetrachloride. Industrial processes have been proposed for chlorinating partially chlorinated methane (methyl chloride, methylene chloride, and chloroform) to carbon tetrachloride. For example, U.S. Patent No. 9,169,177 discloses a method for producing carbon tetrachloride from partially chlorinated methane. To increase the reaction selectivity to carbon tetrachloride, it is proposed in this patent to maintain a conversion rate of less than 90%. This produces a product stream containing chloroform and carbon tetrachloride with little production of methyl chloride or methylene chloride. These chlorinated methanes in the product stream that are not fully chlorinated (e.g., chloroform) are returned to the reactor for further chlorination.

[0005] Due to the increasing demand for carbon tetrachloride, an industrial method for the efficient synthesis of carbon tetrachloride is desired.

Summary of the Invention

[0006] One or more embodiments of the present invention provide a method for producing carbon tetrachloride. The method includes reacting chlorine with chloroform in a reaction mixture containing chlorine, chloroform, and carbon tetrachloride in the presence of electromagnetic radiation, wherein the concentration of chloroform is less than 5000 weight ppm of the weight of the reaction mixture, the reaction mixture contains at least a stoichiometric concentration of chlorine relative to chloroform, the electromagnetic radiation generates chloride radicals, and the reaction mixture is well mixed.

[0007] Other embodiments of the present invention provide a method for producing carbon tetrachloride. The method includes: (i) preparing a reaction mixture containing carbon tetrachloride, chlorine, and chloroform in a reactor; (ii) exposing the reaction mixture to electromagnetic energy to thereby convert at least a portion of the chloroform to carbon tetrachloride; (iii) removing a product stream containing carbon tetrachloride from the reactor; and (iv) returning at least a portion of the product stream to the reactor after the step of removing the product stream.

[0008] Still other embodiments of the present invention relate to improving a method of converting chloroform to carbon tetrachloride by a photochlorination reaction in which chlorine is exposed to ultraviolet light in the presence of chloroform. The improvement includes performing the photochlorination reaction in a well-mixed reactor containing a carbon tetrachloride medium containing less than 5000 ppm of chloroform and at least a stoichiometric concentration of chlorine, in a reaction zone exposed to electromagnetic radiation having a wavelength of about 200 to about 500 nm.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0010] Embodiments of the present invention are, at least in part, based on the discovery of a process for producing carbon tetrachloride by photochlorination of chloroform. According to embodiments of the present invention, the reaction occurs in a carbon tetrachloride medium containing relatively high concentrations of chlorine and relatively low concentrations of chloroform. By practicing the method of the present invention, it has been found, unexpectedly, that industrially useful levels of conversion can be achieved with substantial selectivity for carbon tetrachloride. As an advantage, it has been discovered that the formation of hexachloroethane obtained by dimerization of two trichloromethyl radicals can be maintained below commercially acceptable levels. As a result, the carbon tetrachloride product produced by embodiments of the present invention can be used directly as a crude product stream in subsequent synthetic processes such as the Kolbe reaction, and there is no need to incur the cost of removing unwanted poly-chlorinated organics. Overview of the method

[0011] The overview of one or more embodiments of the present invention can be described with reference to FIG. 1. FIG. 1 shows a chlorination process 11. In an introduction step 13, carbon tetrachloride 12 and chlorine gas 14 are supplied by a carbon tetrachloride feed stream 12' and a chlorine gas feed stream 14'. Here, carbon tetrachloride 12 and chlorine gas 14 are mixed to form a mixture 15 of carbon tetrachloride 12 and chlorine gas 14 (which may sometimes be referred to as the initial mixture 15). The initial mixture 15 of carbon tetrachloride and chlorine gas is then exposed to electromagnetic radiation 18' from an electromagnetic radiation source 18 in a free radical formation step 17. The free radical formation step 17 forms a mixture 19 of chlorine gas, carbon tetrachloride, and chlorine free radicals (which may sometimes be referred to as the free radical mixture 19).

[0012] The chloroform feed stream 20' introduces chloroform 20 into the free radical mixture 19 to form a reaction mixture 22. In the reaction step 21, chloroform 20 is converted to carbon tetrachloride, the desired product, and hydrochloric acid 24, a reaction by - product, is produced. Carbon tetrachloride, chlorine, and hydrochloric acid are contained in the product mixture 28. The product mixture 28 may be regarded as an intermediate stream 28' or a crude product stream 28' from the reaction step 21. Then, one or more additional treatment steps 25 (e.g., a stripping step 25) may be performed on the crude product stream 28'. The additional treatment step 25 may include gas removal, for example, removing at least a portion of chlorine and hydrochloric acid 24 via a gas stream 24' to concentrate carbon tetrachloride 26 via a purified stream 26'.

[0013] In one or more embodiments, at least a portion of the purified carbon tetrachloride 26 may be recycled to the reaction step 21 by a recycle stream 29'. Alternatively, at least a portion of the purified carbon tetrachloride 26 may be recovered as a product 30 by a purified product stream 30'. As described above, the purified stream 26' has the advantage that it does not require a distillation step to remove organic species, such as poly - chlorinated organic compounds, which are often by - products in the manufacture of organic species, such as chlorinated organic compounds, and may be used directly as a reaction stream in subsequent chemical syntheses. That being said, it may be desirable to further purify the product stream for certain uses. Accordingly, certain embodiments of the present invention may include a distillation step to further purify the purified stream 26'.

[0014] Another method scheme can be described with reference to FIG. 2. FIG. 2 shows a chlorination method 31. Introduction Preparation In step 33, carbon tetrachloride 12 from the feed stream 12' is combined with electromagnetic radiation 18' from the radiation source 18 to prepare an irradiation medium 32. Reactive Mixture Formation In step 35 、 Chloroform 20 from the feed stream 20' is combined with chlorine 14 from the feed stream 14' to form a reactant mixture 34. Carbon tetrachloride may be mixed with chloroform 20 and chlorine 14 within this Reactive Mixture Formation step.

[0015] the irradiated medium 32 (continuously exposed to electromagnetic radiation) and Reactive the mixture 34 Introduction are introduced into step 37 to form the reaction mixture 22 and the reaction step 21 is carried out. Here, chloroform 20 is converted to carbon tetrachloride (i.e., chloroform is chlorinated), and hydrochloric acid is produced as a reaction by-product. Carbon tetrachloride and hydrochloric acid are contained in the product mixture 28. The product mixture 28 may be regarded as an intermediate stream 28’ from the reaction step 21, i.e., a crude product stream 28’. Then, one or more additional treatment steps 25 such as a stripping step 25 may be carried out on the crude product stream 28’. Additional (Process) Stripping step 25 may include gas removal to concentrate carbon tetrachloride 26 via a purified stream 26’ and at least a part of chlorine and hydrochloric acid 24 via a gas stream 24’. Remove,

[0016] In one or more embodiments, at least a part of carbon tetrachloride 26 may be recycled via a recycle stream 29’ to (Initial) Introduction Preparation step 33 and / or Reactive Mixture Formation step 35. Alternatively, at least a part of purified done carbon tetrachloride 26 may be recovered as a product 30 via a purified product stream 30’. As described above for FIG. 1, additional purification such as distillation may be avoided. However, in certain embodiments, further purification including distillation may be desirable.

[0017] A system for chlorinating chloroform The system for carrying out the method of the present invention can be described with reference to FIG. 3. FIG. 3 shows a system 51 for carrying out a chlorination method. The system 51 includes a reaction tank 53, and the reaction tank 53 includes an inlet 57, an exhaust port 61, a lamp 63, a stirring element 65, and a product outlet 67.

[0018] According to an exemplary embodiment, chloroform 54 via the chloroform feed stream 54’ is mixed with carbon tetrachloride via, for example, the recycle stream 75’ to form a reactant premix. Next, chlorine 52 from the feed stream 52’ is mixed with the reactant premix containing chloroform and carbon tetrachloride (e.g., via an in-line sparger (porous dispersion tube)) to form a reactant mixture in stream 77’. As shown in FIG. 3, before introducing chlorine, chloroform and carbon tetrachloride may be mixed or stirred in a mixing device such as an in-line mixer 55. In other embodiments (not shown), the mixture containing chlorine, chloroform, and carbon tetrachloride included in stream 77’ may be similarly stirred before introducing it into the reactor 53.

[0019] Next, the feed stream 77’ is introduced into the reactor 53 via the inlet 57. As described above, a chlorination reaction occurs due to the electromagnetic radiation from the lamp 63, whereby chloroform is converted to carbon tetrachloride. The resulting carbon tetrachloride product is taken out of the reactor 53 via the outlet 67 as the product stream 66’ (which may also be referred to as the crude product stream 66’). The product stream 66’ may also contain one or more of chloroform, chlorine, hydrogen chloride, and other by-products at relatively low concentrations. Gaseous by-products (e.g., hydrogen chloride and chlorine) may be taken out of the reactor 53 via the exhaust port 61 to form stream 79’. This stream may be neutralized for disposal, or further separated to isolate chlorine and hydrochloric acid, which may be used in other synthetic chemical processes.

[0020] The crude product stream 66' may be transported to tank 69. Tank 69 may include a degassing tank, where light components (e.g., chlorine and hydrogen chloride) may be removed by gas stream 69' to concentrate the crude product stream 66'. The light components may be mixed with stream 79'. For example, by pump 71, the crude product stream 66' containing concentrated carbon tetrachloride may be returned to reactor 53 through recycle loop 71' via carbon tetrachloride feed stream 75'. Alternatively, the concentrated crude product stream may be discharged from the system for storage and further use via carbon tetrachloride product stream 73'. In one or more embodiments, the carbon tetrachloride product stream 73' may be exposed to additional electromagnetic radiation (lamp 63 as described herein) supplied, for example, from a polishing UV reactor, thereby photochlorinating residual chloroform in the product stream. In one or more embodiments, additional chlorine may be added to the product stream being processed in this downstream finishing reactor.

[0021] It is understood that according to certain embodiments of the present invention, the recycle loop 71' is optional as long as the crude product stream 66' can be transported directly to other processes (i.e., stream 66' can be transported directly to 73'). However, in such embodiments, another source of carbon tetrachloride must be used as the reaction medium.

[0022] Thus, it is understood that the method (and system) of the present invention can be operated as a continuous process, with reactants being continuously supplied to the reactor and products being continuously removed from the reactor. Also, the processing requirements for carbon tetrachloride may be met by the product stream from the system (e.g., the carbon tetrachloride product stream 66' may be recycled to reactor 53 via feed stream 75). In one or more embodiments, after the initial startup of the system that requires an external source of carbon tetrachloride (e.g., carbon tetrachloride 12), the method of the present invention can receive more than 90%, in other embodiments more than 95%, and in still other embodiments more than 99% of the carbon tetrachloride required for operation of the system from carbon tetrachloride recycled from the system (e.g., via loop 71').

[0023] Also, although it is obvious, various modifications may be made to system 51 without departing from the present invention. For example, it is not necessary to premix chlorine 52 and chloroform 54 before introducing them into the reaction vessel 53, and chlorine 52 and chloroform 54 may be directly injected into the reactor 53 through their respective supply streams. In certain embodiments, the chloroform supply stream 54' may be introduced below the liquid level in the reactor (e.g., through an immersion tube). In these or other embodiments, similarly, the chlorine supply stream 52' may also be introduced below the liquid level, for example, through a sparger. In one or more embodiments, the separated individual supply streams may first be mixed with carbon tetrachloride and then introduced directly into the reactor 53. Further, the reactor 53 may generally be configured such that the material flows from the bottom to the top of the reactor as shown in FIG. 3, or alternatively, the flow of the material may be reversed so that the input stream is received at the top of the reactor and the product is removed from the bottom of the reactor.

[0024] In one or more embodiments, the inlet 57 may include a dispersion device such as a sparger or an immersion tube, and the container 53 may include a plurality of inlets (not shown).

[0025] In one or more embodiments, the container 53 may include a single lamp as shown in FIG. 3, or alternatively, may include a plurality of lamps. In one or more embodiments, the lamp 63 may include an ultraviolet lamp, a laser, and a light-emitting diode. In certain embodiments, the lamp may include a mercury vapor discharge lamp (e.g., a Hanovia lamp). In one or more embodiments, these lamps (e.g., lamp 63) may be partially immersed in the reaction medium contained within the container 53, or alternatively, may be completely immersed in the reaction medium. In other embodiments (not shown), the lamp may be disposed outside the interior of the reactor but emit the desired electromagnetic radiation into the reactor medium.

[0026] In addition, the reaction vessel 53 may be provided with a temperature control system such as a heating / cooling jacket. In one or more embodiments, the stirring element 65 may include a single mechanical stirrer as shown in FIG. 3, or a plurality of stirring devices may be employed. As is known in the art, various mixing configurations may be used, including mixers attached to the top and bottom.

[0027] In one or more embodiments, the reactor 58 is configured to include a dark region. The dark region is a region within the reactor that is not exposed to an appropriate amount of electromagnetic radiation to cause the desired photochlorination reaction described herein. Providing this dark region provides the input stream 77' with time and space to be diluted and well mixed in a larger volume of carbon tetrachloride than is contained within the reactor 53, after which chlorine is radicalized in the presence of appropriate electromagnetic radiation and / or the chlorine radicals react with chloroform. Although it will be apparent to those skilled in the art, the dark region may be formed using several reaction mechanisms. For example, a physical barrier may be placed within the reactor to protect a region from the electromagnetic radiation emitted from the lamp 63. Alternatively, in combination with a physical barrier, the dark region may be formed by providing an appropriate distance between the lamp 63 and the desired location of the dark region. As will be apparent to those skilled in the art, it is desirable that the inlet 57 be located within or adjacent to the dark region.

[0028] It is understood that at startup, the reactor 53 is first filled with carbon tetrachloride to form the initial medium in which the reaction occurs. In one or more embodiments, the reactor does not contain, or substantially does not contain, chloroform at the start of the reaction so that chloroform does not become excessive relative to chlorine at any point during the reaction. Once the reaction is in progress, an appropriate balance of chlorine and chloroform, and thus carbon tetrachloride, within the reactor 53 can be maintained by adjusting the input of chlorine, chloroform, and, if necessary, carbon tetrachloride into the reactor 53 (which is described below in this specification).

[0029] This system has been described with reference to specific embodiments of the invention, but those skilled in the art can adapt the system to other methods described herein without undue experimentation or calculation.

[0030] Characteristics of the carbon tetrachloride feed stream In one or more embodiments, the carbon tetrachloride feed stream (e.g., 12’, 75’) is substantially carbon tetrachloride. This carbon tetrachloride feed stream refers to a feed stream that does not contain a detectable amount of components other than carbon tetrachloride. In one or more embodiments, the carbon tetrachloride feed stream (e.g., 12’, 75’) consists essentially of carbon tetrachloride and refers to a composition that does not contain other components that substantially affect the basic and novel characteristics of the embodiments of the invention. In one or more embodiments, the carbon tetrachloride feed stream (e.g., 12’, 75’) consists of carbon tetrachloride. In one or more embodiments, this carbon tetrachloride is industrial grade carbon tetrachloride. In one or more embodiments, the carbon tetrachloride feed streams 12’ and 75’ contain from about 99.9 to about 100 wt% carbon tetrachloride. In one or more embodiments, the carbon tetrachloride feed stream (e.g., 12’, 75’) contains less than 7000 ppm of chlorinated organic components other than carbon tetrachloride, in other embodiments less than 6000 ppm, in other embodiments less than 5500 ppm, in other embodiments less than 5000 ppm, in other embodiments less than 2500 ppm, in other embodiments less than 1000 ppm, in other embodiments less than 750 ppm, in other embodiments less than 500 ppm, in other embodiments less than 100 ppm.

[0031] Characteristics of the chlorine feed stream In one or more embodiments, the chlorine feed stream (e.g., 14’, 52’) is substantially chlorine. This chlorine feed stream refers to a feed stream that contains no appreciable amount of components other than chlorine gas. In one or more embodiments, the chlorine gas feed stream (e.g., 14’, 52’) consists essentially of chlorine gas and refers to a composition that contains no other components that would substantially affect the basic and novel characteristics of the embodiments of the present invention. In one or more embodiments, the chlorine gas feed stream (e.g., 14’, 52’) consists of chlorine gas. In one or more embodiments, the chlorine feed stream (e.g., 14’, 52’) contains from about 99.5 to about 100 vol% chlorine. In one or more embodiments, the chlorine feed stream (e.g., 14’, 52’) contains less than 5000 ppm of components other than chlorine, less than 1000 ppm in other embodiments, less than 750 ppm in other embodiments, and less than 500 ppm in other embodiments.

[0032] In one or more embodiments, the chlorine gas feed stream (e.g., 14’, 52’) is dispersed with nitrogen or another inert medium (such as argon, etc.) before being introduced into the system. Thus, in one or more embodiments, the chlorine gas feed stream (e.g., 14’, 52’) is substantially oxygen-free and refers to a feed stream that contains no appreciable amount of oxygen. In one or more embodiments, the chlorine feed stream (e.g., 14’, 52’) contains less than 2500 ppm of oxygen, less than 1000 ppm in other embodiments, less than 750 ppm in other embodiments, less than 500 ppm in other embodiments, and less than 250 ppm in other embodiments.

[0033] Characteristics of the chloroform feed In one or more embodiments, the chloroform feed streams 20' and 54' refer to feed streams that are substantially chloroform and contain no appreciable amount of components other than chloroform. In one or more embodiments, the chloroform feed streams 20' and 54' consist essentially of chloroform and refer to compositions that contain no other components that would substantially affect the basic and novel characteristics of the embodiments of the present invention. In one or more embodiments, the chloroform feed streams 20' and 54' consist of chloroform. In one or more embodiments, this chloroform is industrial grade chloroform. In other embodiments, carbon fluoride grade chloroform is used. In still other embodiments, the chloroform may include feeds from other synthetic processes such as the production of chloromethane. In one or more embodiments, the chloroform feed streams 20' and 54' contain from about 99.8 to about 100 wt% chloroform. In one or more embodiments, the chloroform feed streams 20' and 54' contain less than 5000 ppm of components other than chloroform, in other embodiments less than 2500 ppm, in other embodiments less than 2000 ppm, in other embodiments less than 1000 ppm, in other embodiments less than 750 ppm, and in other embodiments less than 500 ppm.

[0034] Characteristics of the Reaction Mixture In one or more embodiments, the reaction mixture (e.g., the contents of reaction mixture 22 or reactor 53) containing carbon tetrachloride, chlorine, hydrogen chloride, and chloroform, along with residual by-products (e.g., heavy chlorinated organics, etc.), is maintained at a temperature and pressure such that the carbon tetrachloride is kept in the liquid phase. As will be apparent to those skilled in the art, since it is desirable for the process of the present invention to be carried out in the liquid phase, the higher the operating pressure, the higher the operating temperature.

[0035] In one or more embodiments, during and optionally prior to the reaction or chlorination step (e.g., reaction step 21), the reaction mixture (e.g., reaction mixture 22 or the contents of reactor 53) is maintained at a temperature above 10°C. In other embodiments, it is maintained above 15°C, and in other embodiments above 20°C. In these or other embodiments, prior to or during the reaction step, this reaction mixture is maintained at a temperature below 70°C. In other embodiments below 60°C, and in other embodiments below 50°C. In one or more embodiments, prior to or during the reaction step, this reaction mixture is maintained at a temperature of about 10 to about 70°C. In other embodiments about 15 to about 60°C, and in other embodiments about 20 to about 50°C. In one or more embodiments, the reaction mixture (e.g., reaction mixture 22 or the contents of reactor 53) is maintained at a temperature and pressure sufficient to maintain a relatively high concentration of chlorine and chloroform in the carbon tetrachloride medium.

[0036] In one or more embodiments, prior to or during the reaction or chlorination step (e.g., step 21), the reaction mixture (e.g., reaction mixture 22 or the contents of reactor 53) is maintained at a pressure above 0.8 atm, in other embodiments above 0.9 atm, and in other embodiments above 0.95 atm. In these or other embodiments, prior to or during the reaction step, the reaction mixture is maintained at a pressure below 15 atm, in other embodiments below 10 atm, and in other embodiments below 5 atm. In one or more embodiments, prior to or during the reaction step, the reaction mixture is maintained at a pressure of about 0.8 to about 15 atm, in other embodiments about 0.9 to about 10 atm, or in other embodiments about 0.95 to about 5 atm.

[0037] In one or more embodiments, the reaction mixture (e.g., reaction mixture 22 or the contents of reactor 53) is maintained under agitation before or during the reaction or chlorination step (e.g., step 21). In one or more embodiments, the agitation is sufficient to cause turbulent flow throughout the reactor (e.g., reactor 53) in which the reaction occurs. In one or more embodiments, this agitation is sufficient to achieve a turbulent flow having a Reynolds number quantitative value greater than 4000. In other embodiments, it is sufficient to achieve a turbulent flow having a Reynolds number quantitative value greater than 10,000, and in other embodiments greater than 20,000. In these or other embodiments, the reaction mixture is agitated before or during the reaction or chlorination step (e.g., step 21) to generate a turbulent flow having a Reynolds number quantitative value of about 4000 to about 30,000, in other embodiments about 8,000 to about 28,000, or in other embodiments about 10,000 to about 26,000. In one or more embodiments, the photochlorination method of the present invention is carried out in a reactor (e.g., reactor 53). This reactor is a well-mixed reactor with sufficient agitation to approximate an ideal continuous stirred tank reactor (CSTR).

[0038] As proposed above, in the introduction of chloroform into the reaction mixture (e.g., reaction mixture 22 or the contents of reactor 53), its feed rate adjusts the chloroform concentration in the reactor, and the introduction is carried out in an amount and manner such that in the presence of UV light, the reaction of chloroform to carbon tetrachloride occurs substantially instantaneously. Unexpectedly, it has been discovered that diluting and diffusing chloroform, which is miscible with carbon tetrachloride, immediately before or during the reaction step (e.g., step 21) is an important parameter for obtaining the beneficial results of the present invention.

[0039] In one or more embodiments, the feed rate of chloroform to the reactor (e.g., reactor 53) may be quantified relative to carbon tetrachloride in the reactor. In one or more embodiments, the feed rate of chloroform is greater than 10 pounds (4.54 kg) per hour per 1000 pounds (454 kg) of carbon tetrachloride in the reactor, in other embodiments greater than 15 pounds (6.80 kg), in other embodiments greater than 25 pounds (11.3 kg), in other embodiments greater than 35 pounds (15.9 kg), in other embodiments greater than 45 pounds (20.4 kg), in other embodiments greater than 55 pounds (24.9 kg), in other embodiments greater than 65 pounds (29.5 kg), in other embodiments greater than 75 pounds (34.0 kg), in other embodiments greater than 85 pounds (38.6 kg), in other embodiments greater than 95 pounds (43.1 kg), in other embodiments greater than 110 pounds (49.9 kg), and in other embodiments greater than 120 pounds (54.4 kg). In these or other embodiments, the feed rate of chloroform is less than 1000 pounds (454 kg) per hour per 1000 pounds (454 kg) of carbon tetrachloride in the reactor, in other embodiments less than 800 pounds (363 kg), in other embodiments less than 650 pounds (295 kg), in other embodiments less than 500 pounds (227 kg), in other embodiments less than 250 pounds (113 kg), in other embodiments less than 200 pounds (90.7 kg), in other embodiments less than 150 pounds (68.0 kg), in other embodiments less than 125 pounds (56.7 kg), in other embodiments less than 100 pounds (45.4 kg), in other embodiments less than 80 pounds (36.3 kg), in other embodiments less than 60 pounds (27.2 kg), in other embodiments less than 40 pounds (18.1 kg), in other embodiments less than 30 pounds (13.6 kg), and in other embodiments less than 25 pounds (11.3 kg). In one or more embodiments, the feed rate of chloroform is about 10 to about 1000 pounds (about 4.54 to about 454 kg) per hour per 1000 pounds (454 kg) of carbon tetrachloride in the reactor, in other embodiments about 25 to about 650 pounds (about 11.3 to about 295 kg), and in other embodiments about 55 to about 200 pounds (about 24.9 to about 90.7 kg).

[0040] In one or more embodiments, the dilution of chloroform may also be quantified based on the amount of chloroform in the reaction mixture (e.g., the contents of reaction mixture 22 or reactor 53). For example, the chloroform concentration in the reaction mixture may be quantified based on the weight of chloroform relative to the weight of the reaction mixture. This reaction mixture contains carbon tetrachloride, chlorine, hydrogen chloride, and chloroform. As will be apparent to those skilled in the art, these amounts (i.e., the chloroform in the reaction mixture) may be determined by measuring the amount of chloroform in the reactor effluent (i.e., at the outlet). The amount of chloroform corresponds well to the amount of chloroform in the reaction zone within a well-stirred reactor. The reaction zone of such a reactor refers to the location within the reaction medium (i.e., the reactor) where chlorination of chloroform occurs (i.e., the reaction mixture is exposed to electromagnetic radiation of an appropriate wavelength). In one or more embodiments, the chloroform concentration in the reaction mixture is less than 5,000 weight ppm relative to the total weight of the reaction mixture, in other embodiments less than 4,000 weight ppm, in other embodiments less than 3,000 weight ppm, and in other embodiments less than 2,000 weight ppm. In one or more embodiments, the chloroform concentration in the reaction mixture is from about 1 to about 5,000 weight ppm relative to the total weight of the reaction mixture, in other embodiments from about 50 to about 3,000 weight ppm, and in other embodiments from about 100 to about 2,000 weight ppm.

[0041] As proposed above, the amount of chlorine present in the reaction mixture during a reaction step (e.g., reaction step 21), or otherwise described, appears to be one of the important parameters for practicing the present invention. In one or more embodiments, the introduction of chlorine into the reaction mixture (e.g., vessel 53) is carried out in an amount and manner such that it reacts with at least a stoichiometric amount or a stoichiometric excess of chlorine relative to chloroform. In one or more embodiments, the chlorine concentration in the reaction medium (i.e., carbon tetrachloride) is a saturated concentration relative to chlorine in carbon tetrachloride at the temperature and pressure at which the reaction is carried out. In one or more embodiments, the amount of chlorine in the reactor (e.g., reactor 53) is an amount sufficient to maintain a detectable level of chlorine in the headspace of the reactor. The chlorine concentration in the reactor is continuously maintained over time to the extent of supplying an excess of chlorine to the reactor relative to chloroform until it reaches a saturated concentration with respect to the temperature and pressure in the reactor. If there is chlorine in the reactor, carbon tetrachloride may be recycled by a recycle loop to adjust its amount.

[0042] In one or more embodiments, the amount of chlorine introduced into the reaction mixture may be quantified based on the molar ratio of chlorine to chloroform supplied to the reactor. In one or more embodiments, for example, the molar ratio of chlorine to chloroform supplied to reactor 53 is greater than 1.00:1.00, in other embodiments greater than 1.02:1.00, and in still other embodiments greater than 1.04:1.00. In one or more embodiments, the molar ratio of chlorine to chloroform is from about 1.00:1.00 to about 1.10:1.00, in other embodiments from about 1.01:1.00 to about 1.08:1.00, and in still other embodiments from about 1.02:1.00 to about 1.06:1.00.

[0043] In these or other embodiments, the amount of chlorine used in the process of the present invention may be quantified based on the chlorine concentration in the reaction mixture. As will be apparent to those skilled in the art, these amounts (i.e., chlorine in the reaction mixture) may be determined by measuring the amount of chlorine in the reactor effluent (i.e., at the outlet). Here, the amount of chlorine in the well-stirred reactor corresponds to the amount of chlorine in the reaction zone. This reaction zone refers to the location within the reaction medium (i.e., the reactor) where the chlorination of chloroform occurs. In one or more embodiments, the chlorine concentration in the effluent is greater than 0.01 wt% relative to the total weight of the reaction mixture, in other embodiments greater than 0.1 wt%, in other embodiments greater than 0.3 wt%, in other embodiments greater than 0.6 wt%, in other embodiments greater than 1.2 wt%, in other embodiments greater than 1.5 wt%, in other embodiments greater than 1.8 wt%, and in other embodiments greater than 2.0 wt%. In these or other embodiments, the chlorine concentration in the reactor effluent is the saturation concentration at a given temperature and pressure, in other embodiments less than 5 wt% relative to the total weight of the reaction mixture, in other embodiments less than 4.6 wt%, and in other embodiments less than 4.2 wt%. In one or more embodiments, the chlorine concentration in the reactor effluent is from about 0.01 wt% to the saturation concentration relative to the total weight of the reaction mixture, in other embodiments from about 0.1 to about 5 wt%, in other embodiments from about 0.3 to about 5 wt%, in other embodiments from about 1.8 to about 4.6 wt%, and in other embodiments from about 2.0 wt% to about 4.2 wt%.

[0044] Characteristics of electromagnetic radiation In one or more embodiments, the electromagnetic radiation used to practice the present invention (e.g., generated by lamp 63) includes wavelengths from about 200 to about 500 nm. In other embodiments, it includes wavelengths from about 200 to about 400 nm, in other embodiments from about 280 to about 380 nm, and in other embodiments from about 300 to about 350 nm. In these or other embodiments, the electromagnetic radiation is characterized by a wavelength distribution based on relative intensity, with about 50 to about 60% of the intensity having wavelengths from about 280 to about 435 nm. In these or other embodiments, about 40 to about 50% of the intensity has wavelengths from about 300 to about 380 nm. In these or other embodiments, about 20 to about 30% of the intensity has wavelengths from about 330 to about 370 nm. In one or more embodiments, the electromagnetic radiation includes ultraviolet light.

[0045] In one or more embodiments, the electromagnetic radiation is obtained from one or more light-generating lamps operating at 40 to about 20,000 W. In other embodiments, it is obtained from one or more light-generating lamps operating at about 75 to about 18,000 W, and in other embodiments at about 100 to about 10,000 W. In one or more embodiments, the electromagnetic radiation is obtained from one or more mercury lamps. In certain embodiments, the electromagnetic radiation is obtained from a Hanovia mercury vapor discharge lamp.

[0046] Characteristics of the product stream As described above, the crude carbon tetrachloride product streams (e.g., streams 28' and 66') contain the desired carbon tetrachloride product, chlorine, hydrogen chloride, and residual by-products (e.g., heavy chlorinated organics, etc.). In one or more embodiments, these product streams (e.g., 28' and 66') are substantially carbon tetrachloride, chloroform, hydrogen chloride, and optionally chlorine. These product streams refer to product streams that do not contain detectable amounts of components other than carbon tetrachloride, chloroform, hydrogen chloride, and optionally chlorine. In one or more embodiments, this product stream (e.g., 28' and 66') consists essentially of carbon tetrachloride, and optionally chloroform, hydrogen chloride, and chlorine. This product stream refers to a composition that does not contain other components that substantially affect the basic and novel properties of the embodiments of the present invention. In one or more embodiments, this product stream (e.g., 28' and 66') consists of carbon tetrachloride, and optionally chloroform, hydrogen chloride, and chlorine.

[0047] In one or more embodiments, this product stream (e.g., 28' and 66') contains less than 2500 ppm (parts per million by weight), in other embodiments less than 1000 ppm, in other embodiments less than 500 ppm, in other embodiments less than 250 ppm, in other embodiments less than 100 ppm of chlorinated hydrocarbons other than carbon tetrachloride (e.g., hexachloroethane).

[0048] In one or more embodiments, this product stream (e.g., 28' and 66') contains less than 2500 ppm (parts per million by weight), in other embodiments less than 1000 ppm, in other embodiments less than 750 ppm, in other embodiments less than 500 ppm of components other than carbon tetrachloride, hydrogen chloride, and chlorine.

[0049] In one or more embodiments, the product streams (e.g., 28’ and 66’) have the advantage of having a low concentration of chloroform. This indicates a high reaction yield. In one or more embodiments, the reaction yield with respect to chloroform is greater than 90.00%, in other embodiments greater than 92.00%, in other embodiments greater than 95.00%, in other embodiments greater than 97.00%, in other embodiments greater than 98.00%, in other embodiments greater than 99.00%, in other embodiments greater than 99.50%, in other embodiments greater than 99.99%. In certain embodiments, the yield with respect to chloroform is 100%. As a result, the product streams 28’ and 66’ contain less than 6000 ppm (parts per million by weight), in other embodiments less than 5500 ppm, in other embodiments less than 5000 ppm, in other embodiments less than 4500 ppm, in other embodiments less than 4000 ppm, in other embodiments less than 3000 ppm, in other embodiments less than 2000 ppm, in other embodiments less than 1000 ppm, in other embodiments less than 500 ppm, in other embodiments less than 250 ppm, in other embodiments less than 100 ppm, in other embodiments less than 50 ppm, in other embodiments less than 10 ppm of chloroform.

[0050] Reaction mechanism As proposed herein, it is believed that the manner and sequence of this process form chlorine-free radicals prior to any side reactions (e.g., dimerization of chloroform) and promote the reaction of these radicals with chloroform, thereby enhancing the selectivity of the reaction. Without being bound by any particular theory, it is believed that the following reactions occur during one or more steps of the present invention. Cl2 + hν → 2Cl * (1) Initiation CHCl3 + Cl * → CCl3 * + HCl (2) Propagation CCl3 * + Cl2 → CCl4 + Cl * (3) Propagation CCl3 * + CCl3 * → C2Cl6 (4) Termination CCl3 * + Cl * → CCl4 (5) Stop Cl * + Cl * → Cl2 (6) Stop Reactions 1 - 3 are the desired pathways to convert chloroform and chlorine gas into carbon tetrachloride and HCl by - products. Reaction 5 produces the desired product but terminates the free - radical reaction chain. Reaction 4 terminates the reaction chain and involves dimerization of two trichloromethyl radicals to form hexachloroethane. This reaction is substantially avoided in the present invention. Reaction 6 terminates the reaction chain but can generate free radicals again by supplying chlorine in the presence of an initiator such as UV light.

Industrial Applicability

[0051] In one or more embodiments, a crude product stream (e.g., stream 28’, 66’, or 73’) may be used in the synthesis of chlorinated organic compounds. As shown above, the method of one or more embodiments of the present invention does not require a separation step (e.g., a distillation step) and provides a product stream that can be directly used in these downstream synthesis processes, with the advantage of removing heavy chlorinated organic by - products such as hexachloroethane.

[0052] In one or more embodiments, carbon tetrachloride produced as a crude product stream according to embodiments of the present invention can be directly mixed with an olefin (e.g., ethylene or vinyl chloride) and reacted in the presence of a suitable catalyst to form chlorinated propane and / or chlorinated propene. In this regard, reference is made to U.S. Pat. Nos. 6,187,978 and 6,313,360, and U.S. Patent Publications 2012 / 0310020, 2009 / 0216055, and 2004 / 0225166, which are hereby incorporated by reference into this specification.

[0053] To illustrate the practice of the present invention, the following examples were prepared and tested. However, the following examples should not be considered as limiting the scope of the present invention. The present invention is defined by the claims.

Examples

[0054] Examples 1 - 5 All of the reactions of Examples 1 - 5 were carried out in a 1 - liter Pyrex stirred reactor (Ace reactor #7864 - 12) equipped with a jacket using a water - cooled quartz immersion lamp well (Ace #7874 - 38) equipped with a jacket. It was irradiated with a 450 - watt medium - pressure mercury vapor discharge lamp (Ace #7825 - 35). A magnetic stir bar was used to ensure thorough mixing inside the reactor. The mixing conditions inside the reactor were calculated so that the Reynolds number was about 24,400. Each experiment was carried out over about 6 hours. The examples were analyzed by gas chromatography using a 30 m×0.53 mm DB - 624 column and a thermal conductivity detector (TCD). The concentration of hexachloroethane (the only undesirable by - product detected) was measured, the percentage of chloroform consumed to form it was calculated, and the selectivity was calculated by subtracting from 100%. The relevant data for each example are summarized in Table 1 below.

[0055] Example 1 A 1158 - gram mixture containing 4.4 wt% chloroform and 95.6 wt% carbon tetrachloride was charged into the reactor. The reaction temperature was maintained at 35°C. The UV lamp was turned on. After 5 minutes, 100 wt% chloroform was fed at a rate of 0.29 g / min, and 100 wt% chlorine gas was diffused into the solution at a rate of 0.18 g / min for 6 hours. Chlorine was supplied at 70% of the stoichiometrically required amount for the reaction. Samples were taken every hour for 6 hours. When the selectivity of chloroform with respect to carbon tetrachloride was determined, it was 65.2%, and the remainder of the chloroform formed hexachloroethane. The data collected every hour showed no change in selectivity over time other than normal experimental variations.

[0056] Example 2 1196 grams of 100 wt% carbon tetrachloride was charged into the reactor. The reaction temperature was maintained at 35 °C. The UV lamp was turned on. After 4 minutes, 100% chloroform was fed at a rate of 0.30 g / min, and 100 wt% chlorine was diffused into the solution at a rate of 0.18 g / min for 6 hours and 10 minutes. Chlorine was supplied in a stoichiometrically required amount for the reaction. Samples were taken every hour. When the selectivity of chloroform with respect to carbon tetrachloride was determined, it was approximately 100%. The conversion rate of chloroform to hexachloroethane was less than 0.003% (not detectable at the detection limit of the analytical method). The data collected every hour showed no change in selectivity over time other than normal experimental variations.

[0057] Example 3 1190 grams of 100 wt% carbon tetrachloride was charged into the reactor. The reaction temperature was maintained at 25 °C. The UV lamp was turned on. After 4 minutes, 100 wt% chloroform was fed at a rate of 0.30 g / min, and 100 wt% chlorine was diffused into the solution at a rate of 0.18 g / min for 5 hours. Chlorine was supplied in a stoichiometrically required amount for the reaction. Samples were taken every hour. When the selectivity of chloroform with respect to carbon tetrachloride was determined, it was approximately 100%. The conversion rate of chloroform to hexachloroethane was less than 0.003% (not detectable at the detection limit of the analytical method). The data collected every hour showed no change in selectivity over time other than normal experimental variations.

[0058] Example 4 1207 grams of 100 wt% carbon tetrachloride was charged into the reactor. The reaction temperature was maintained at 35 °C. Chlorine was diffused at a rate of 0.18 g / min. The UV lamp was turned on after 30 minutes. After another 5 minutes, 100% chloroform was fed at a rate of 0.31 g / min. Chlorine was supplied in an excess amount of the stoichiometrically required amount for the reaction. Samples were taken every hour. When the selectivity of chloroform with respect to carbon tetrachloride was determined, it was approximately 100%. The conversion rate of chloroform to hexachloroethane was less than 0.003% (not detectable at the detection limit of the analytical method). The data collected every hour showed no change in selectivity over time other than normal experimental variations.

[0059] Example 5 A reactor was charged with a mixture (1225 grams) containing about 5000 weight ppm of chloroform and the balance carbon tetrachloride. The reaction temperature was maintained at 35 °C. The UV lamp was turned on. After 5 minutes, 100 wt% chloroform was fed at a rate of 0.30 g / min, and 100 wt% chlorine gas was diffused into the solution at a rate of 0.18 g / min for 5 hours. Chlorine was supplied at 94% of the stoichiometrically required amount for the reaction. Samples were taken every hour. The selectivity of chloroform with respect to carbon tetrachloride was determined to be 81.4%. The remainder of the chloroform produced hexachloroethane. The data collected every hour showed no change in selectivity over time other than normal experimental variations.

[0060] [Table 1]

[0061] The data in Table 1 indicate that Examples 1 and 5 are outside the scope of the practice of the present invention. This is because the conversion rate to carbon tetrachloride and the selectivity of the reaction were lower than acceptable levels. The product streams obtained from Examples 1 and 5 both required further distillation of the product stream to remove hexachloroethane. Examples 2, 3, and 4 show very advantageous results, suggesting that the excess chloroform present in Examples 1 and 5 has an adverse effect on this reaction.

[0062] Examples 6 - 9 In Examples 6 to 9, the reactor system used in Examples 1 to 5 was modified to provide a circulation loop. With this circulation loop, chloroform can be mixed with carbon tetrachloride outside the reactor, and chlorine can be dispersed into this mixture before introducing the blend of chloroform, carbon tetrachloride, and chlorine into the reactor. A magnetic stir bar was used to ensure good mixing in the reactor. The mixing conditions in the reactor were calculated so that the Reynolds number was about 20,000. Each experiment was carried out over a time interval of about 90 minutes. The product was sent from the top of the reactor to the product receiving section to maintain the liquid in the reactor at a constant volume throughout each experiment. A 100-watt medium-pressure mercury vapor discharge lamp (Ace#7825-30) equipped with a borosilicate glass filter (Ace#7835 44) was used to cause the radiation to attenuate at lower wavelengths. The relevant data from each example are summarized in Table 2 below.

[0063] Example 6 The reactor was charged with 957 grams of carbon tetrachloride. The reaction temperature was maintained at 35 °C. The UV lamp was turned on. After 5 minutes, 100 wt% chloroform was fed at a rate of 5.30 g / min, and 100 wt% chlorine gas was diffused into this solution at a rate of 3.42 g / min for 90 minutes. Chlorine was supplied in an amount 112% of the stoichiometric amount required for the reaction. Samples were taken every 30 minutes. The conversion rate of chloroform was 98.90%, and the selectivity of chloroform to carbon tetrachloride was 99.94%. The remainder was chloroform that reacted to form hexachloroethane.

[0064] Example 7 A reactor was charged with a mixture (953 grams) containing 1.02% chloroform in carbon tetrachloride. The reaction temperature was maintained at 35 °C. The UV lamp was turned on. After 5 minutes, 100 wt% chloroform was fed at a rate of 5.78 g / min, and 100 wt% chlorine gas was diffused into this solution at a rate of 3.42 g / min for 90 minutes. Chlorine was supplied at 100% of the stoichiometrically required amount for the reaction with the fed chloroform. Samples were taken every 30 minutes. The conversion of chloroform was 97.79%, and the selectivity of chloroform with respect to carbon tetrachloride was 99.84%. The remainder was chloroform that reacted to form hexachloroethane.

[0065] Example 8 A reactor was charged with a mixture (1044 grams) containing 8.93% chloroform in carbon tetrachloride. The reaction temperature was maintained at 35 °C. The UV lamp was turned on. After 5 minutes, 100 wt% chloroform was fed at a rate of 5.76 g / min, and 100 wt% chlorine gas was diffused into this solution at a rate of 3.42 g / min for 90 minutes. Chlorine was supplied at 100% of the stoichiometrically required amount for the reaction with the fed chloroform. Samples were taken every 30 minutes. The conversion of chloroform was 90.99%, and the selectivity of chloroform with respect to carbon tetrachloride was 99.67%. The remainder was chloroform that reacted to form hexachloroethane.

[0066] Example 9 In this example, the borosilicate glass filter was removed from the UV lamp. A reactor was charged with a mixture (963 grams) containing 1.24% chloroform in carbon tetrachloride. The reaction temperature was maintained at 35 °C. The UV lamp was turned on. After 5 minutes, 100 wt% chloroform was fed at a rate of 5.78 g / min, and 100 wt% chlorine gas was diffused into this solution at a rate of 3.42 g / min for 90 minutes. Chlorine was supplied at 100% of the stoichiometrically required amount for the reaction with the fed chloroform. Samples were taken every 30 minutes. The conversion of chloroform was 98.33%, and the selectivity of chloroform with respect to carbon tetrachloride was 99.60%. The remainder was chloroform that reacted to form hexachloroethane.

[0067]

Table 2

[0068] The data in Table 2 shows that Examples 7, 8, and 9 are outside the scope of the practice of the present invention. This is because the selectivity of the reaction to carbon tetrachloride is outside the acceptable range. For example, in Example 7, the achieved selectivity was only 99.84%, and for this reason, the resulting product stream contained more than 1500 ppm of hexachloroethane. This is an unacceptable concentration in most synthetic processes using carbon tetrachloride as a raw material. Therefore, further distillation of the product stream is required to remove hexachloroethane. Examples 7, 8, and 9 are considered to be disqualified due to the presence of excessive chloroform during the reaction.

[0069] It will be apparent to those skilled in the art that various modifications and changes can be made without departing from the scope and spirit of the present invention. The present invention is not limited to the exemplary embodiments described herein.

Claims

1. (i) providing a reactive mixture in a reactor comprising carbon tetrachloride, chlorine, and chloroform; Providing a carbon tetrachloride medium containing less than 5000 ppm chloroform and at least a stoichiometric concentration of chlorine; continuously supplying chlorine and chloroform to said carbon tetrachloride medium to form said reactive mixture; providing a reactive mixture; (ii) exposing the reactive mixture to electromagnetic energy, thereby converting at least a portion of the chloroform to carbon tetrachloride; (iii) continuously removing from the reactor a product stream comprising carbon tetrachloride, less than 2500 ppm of chlorinated hydrocarbons other than carbon tetrachloride, and less than 1000 ppm of hexachloroethane, wherein the amount of chloroform in the product stream is indicative of a reaction yield relative to chloroform of greater than 99.00%; and (iv) returning only a portion of the product stream to the reactor after the step of removing a product stream, thereby providing a remaining portion of the product stream that was not returned to the reactor, the remaining portion of the product stream being suitable for use in a subsequent chemical synthesis without the need to remove organic species from the remaining portion of the product stream; A method for producing carbon tetrachloride, comprising:

2. The method of claim 1, wherein the step of preparing a reactive mixture includes introducing chloroform into the reactor at a rate of less than 800 pounds per hour for every 1,000 pounds of carbon tetrachloride in the reactor.

3. The method of claim 1, wherein the step of preparing a reactive mixture comprises introducing chlorine into the reactor in a molar ratio relative to chloroform of greater than 1.02:1.

00.

4. 10. The method of claim 1, further comprising agitating the reactive mixture in the reactor to provide a well-mixed reactor that approximates an ideal continuous stirred tank reactor.

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