A process for producing chlorinated hydrocarbons

Abstract

In a process for the production of 1,1,1,2,3-pentachloropropane, optionally in the presence of carbon tetrachloride, by introducing 1,1,1,3-tetrachloropropane, chlorine and a Lewis acid catalyst, the improvement comprising: introducing the Lewis acid as a slurry in a chlorinated hydrocarbon.

Description

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 62 / 366,680, filed July 26, 2016, which is incorporated herein by reference. Invention Field

[0002] Embodiments of the present invention provide methods for producing chlorinated hydrocarbons, particularly methods for producing 1,1,1,2,3-pentachloropropane and 1,1,2,3-tetrachloropropene. Background Technology

[0003] Hydrofluoroolefins (HFOs) have been proposed as "fourth-generation" refrigerants. These compounds have also been proposed for use as foaming agents, biocides, and monomer feedstocks. Most industrially available synthetic techniques require chlorinated hydrocarbon feedstocks to produce HFOs. In particular, 2,3,3,3-tetrafluoropropylene (HFO-1234yf) can be produced using 1,1,2,3-tetrachloropropylene (HCC-1230xa) as a feedstock.

[0004] U.S. Patent Publication No. 2009 / 0216055A1 teaches a method for producing 1,1,2,3-tetrachloropropene by dehydrochlorinating 1,1,1,2,3-pentachloropropane (HCC-240db). This patent disclosure teaches the production of 1,1,1,2,3-pentachloropropane in a single reaction vessel by heating a reaction mixture of 1,1,1,3-tetrachloropropane (HCC-240fa), chlorine, and a Lewis acid catalyst. The Lewis acid catalyst dehydrochlorinates 1,1,1,3-tetrachloropropane to form 1,1,3-trichloropropene, which is then reacted with chlorine in the presence of the catalyst to produce 1,1,1,2,3-pentachloropropane. The catalyst (e.g., ferric chloride) is added to the reactor continuously or periodically and is typically maintained at 30-1000 ppm. The product is continuously or periodically added to a reactive distillation system, in which 1,1,1,2,3-pentachloropropane is dehydrochlorinated to 1,1,2,3-tetrachloropropene in the presence of a Lewis acid catalyst (such as ferric chloride). The distillation system comprises a reaction zone, a separation zone, and a condensation zone. The liquid in the reaction zone is heated and stirred. Heat can be provided through a jacket on the vessel, through an internal heat exchanger, or through an external heat exchanger, and stirring can be provided through circulation or agitation by a pump.

[0005] Since 1,1,2,3-tetrachloropropene is an important raw material for the synthesis of certain HFOs, it is necessary to improve the efficiency of the 1,1,2,3-tetrachloropropene production method. Invention Overview

[0006] One or more embodiments of the present invention provide a method for producing 1,1,1,2,3-pentachloropropane, optionally in the presence of carbon tetrachloride, by introducing 1,1,1,3-tetrachloropropane, chlorine, and a Lewis acid catalyst, the improvement comprising: introducing the Lewis acid as a slurry in the chlorinated hydrocarbon.

[0007] Other embodiments of the present invention provide a method for converting 1,1,1,2,3-pentachloropropane to 1,1,2,3-tetrachloropropene by reactive distillation in the presence of a Lewis acid catalyst, the improvement comprising: heating a crude product stream containing 1,1,1,2,3-pentachloropropane and a Lewis acid catalyst in a reboiler, said reboiler being operated under conditions that suppress reactions or deposit formation in the distillation column and the reboiler.

[0008] Other embodiments of the present invention provide a method for producing 1,1,1,2,3-pentachloropropane, the method comprising: (i) providing a slurry of a Lewis acid catalyst in a chlorinated hydrocarbon; (ii) continuously circulating the slurry through a slurry loop in fluid communication with a reactor; and (iii) introducing 1,1,1,3-tetrachloropropane, chlorine and the slurry into the reactor.

[0009] Other embodiments of the present invention provide a method for converting 1,1,1,2,3-pentachloropropane into 1,1,2,3-tetrachloropropane, the method comprising: (i) providing a mixture of 1,1,1,2,3-pentachloropropane and a Lewis acid catalyst; (ii) heating the mixture in a forced circulation reboiler; and (iii) introducing the heated mixture from the forced circulation reboiler into a column, thereby evaporating 1,1,2,3-tetrachloropropene formed by heating 1,1,1,2,3-pentachloropropane in the presence of the Lewis acid catalyst. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of a system for the preparation of 1,1,1,2,3-pentachloropropane, wherein the method includes a slurry loop for delivering Lewis acid to a reactor.

[0011] Figure 2 This is a schematic diagram of a system for dehydrochlorinating 1,1,1,2,3-pentachloropropane in the presence of a Lewis acid. Detailed description of exemplary implementation methods

[0012] Embodiments of the present invention provide at least in part a method for synthesizing 1,1,1,2,3-pentachloropropane by chlorination of 1,1,1,3-tetrachloropropane, wherein one or more Lewis acid catalysts (e.g., ferric chloride) are delivered from a slurry system to a reaction vessel, wherein the catalyst is slurried in a chlorinated hydrocarbon (e.g., carbon tetrachloride). It is believed that high efficiency can be achieved by preparing the catalyst slurry separately, and problems associated with Lewis acid catalysts, such as operational issues and their tendency to absorb water, can be avoided. This method also advantageously allows for more limited control over the introduction of the catalyst into the reactor.

[0013] According to other embodiments, 1,1,1,2,3-pentachloropropane crude is dehydrochlorinated to 1,1,2,3-tetrachloropropene via reactive distillation, a technique in which the crude is heated within a forced-circulation reboiler. Flow rates and heat flux within the reboiler are maintained to prevent scaling within the distillation system. Indeed, it has been found that localized hot spots within the distillation system can cause catalyst residues to bake onto the system's surfaces. Therefore, while the prior art teaches that 1,1,1,2,3-pentachloropropane crude can be directly processed by reactive distillation to form 1,1,2,3-tetrachloropropene, specific distillation systems that can improve process efficiency are now considered. Furthermore, since reactive distillation is carried out in the presence of a Lewis acid catalyst (e.g., ferric chloride) at a threshold level, higher efficiency is anticipated when using the same or similar slurry system for delivering the Lewis acid catalyst to the chlorination reactor.

[0014] Synthesis of 1,1,1,2,3-pentachloropropane

[0015] According to embodiments of the present invention, 1,1,1,2,3-pentachloropropane is prepared by introducing 1,1,1,3-tetrachloropropane, chlorine, a Lewis acid, and optionally carbon tetrachloride. In this regard, U.S. Publication No. 2009 / 0216055A1 is incorporated herein by reference. As will be understood by those skilled in the art, 1,1,1,3-tetrachloropropane is a liquid under reaction conditions, and therefore chlorine and a Lewis acid catalyst are added to the 1,1,1,3-tetrachloropropane liquid, which may contain a mixture of carbon tetrachloride. In one or more embodiments, chlorine is added as a gas and can be added to the 1,1,1,3-tetrachloropropane liquid, for example, through a tube immersed in the liquid or through one or more gas dispersion elements in the liquid. As will be understood by those skilled in the art, a variety of Lewis acid catalysts have been used as chlorination catalysts, and the practice of embodiments of the present invention is not limited to a particular Lewis acid catalyst. Ferric chloride is a common chlorination catalyst and / or dehydrochlorination catalyst, and therefore specific embodiments of the invention are described with reference to ferric chloride, but those skilled in the art can readily extend the teachings herein to other chlorination catalysts.

[0016] According to embodiments of the invention, a Lewis acid (such as ferric chloride) that is partially soluble in the reaction medium under reaction conditions is introduced into a liquid 1,1,1,3-tetrachloropropane as a slurry dispersed (and partially dissolved) in a liquid chlorinated hydrocarbon (e.g., carbon tetrachloride). In one or more embodiments, the catalyst is maintained in the liquid dispersion by continuous stirring, which can be provided, for example, by a continuous circulation loop connected to a container containing the liquid 1,1,1,3-tetrachloropropane.

[0017] The methods of one or more embodiments of the present invention can be referred to Figure 1 The system 11 includes a Lewis acid mixing tank 21, which is in fluid communication with a reactor 51 (which may be referred to as a chlorination reactor 51) via a circulation loop 41. The slurry tank 21 receives chlorinated hydrocarbons (e.g., carbon tetrachloride) 31 through inlet 22 and Lewis acid catalyst 33 through inlet 23. The slurry tank 21 may also optionally receive other materials 34 through inlet 26, such as other solvents, catalysts, catalyst ligands, or recycle streams obtained downstream of the process. In one or more embodiments, carbon tetrachloride 31 may be continuously fed into the slurry tank 21 through inlet 22, or in other embodiments, it may be periodically injected into the slurry tank 21 through inlet 22. Similarly, the Lewis acid catalyst 33 may be periodically added to the slurry tank 21, or in other embodiments, the Lewis acid catalyst 33 may be continuously added to the slurry tank 21 using a continuous feed device. For example, the Lewis acid 33 may be added to the slurry tank 21 using a dustless bucket tipper.

[0018] A slurry 35 of Lewis acid 33 and carbon tetrachloride 31 is formed by stirring the mixture in a slurry tank 21 using one or more mixing elements 24, which may include agitators or baffles. The mixing elements 24 can be operated in such a way that the Lewis acid catalyst is sufficiently dispersed in the chlorinated hydrocarbon liquid (e.g., carbon tetrachloride); in a particular embodiment, stirring is sufficient to obtain a substantially uniform Lewis acid concentration in the chlorinated hydrocarbon.

[0019] Slurry 35 is continuously circulated through circulation loop 41 by one or more pumps 43 located upstream of reactor 51, which also advantageously maintain pressure within loop 41. Sufficient pressure can also be maintained within loop 41 with the assistance of a back pressure valve 49 located downstream of loop 41 (i.e., downstream of valve 47 within loop 41) that delivers slurry 35 to reactor 51. Slurry 35 moving through loop 41 can be heated or cooled by heating or cooling elements 45. Other materials 34 (e.g., those described above) may also optionally be injected into loop 41. In one or more embodiments, mixing of the various components in slurry 35 can be enhanced by one or more in-line mixers (not shown). Circulation loop 41 may also include valve 47, which allows slurry 35 to be fed into reactor 51 when valve 47 is in the open position. When valve 47 is in the closed position, slurry 35 is circulated back to mixing tank 21 through loop 41. Valve 47 may include a control valve or solenoid valve controllable by a flow signal sensor or similar device.

[0020] Reactor 51 receives slurry 35 from loop 41 through inlet 53. Reactor 51 also receives chlorine 61 through inlet 55 and 1,1,1,3-tetrachloropropane 65 through inlet 57. Additionally, reactor 51 may optionally receive other material inputs 34, such as those described above. Reactor effluent 63 exits reactor 51 at outlet 59 as a coarse 1,1,1,2,3-pentachloropropane feed stream 71.

[0021] In one or more embodiments, the flow rate of slurry 35 into reactor 51 (which is at least partially regulated by valve 47) can be proportional to the feed rate of 1,1,1,3-tetrachloropropane 65 and chlorine 61 into reactor 51.

[0022] In one or more embodiments, the pressure maintained in loop 41 is greater than the pressure in reactor 51; in a particular embodiment, the pressure in loop 41 is sufficient to generate flow into reactor 51 (when valve 47 is open), taking into account potential gravity assistance. As those skilled in the art will understand, sufficient pressure can be maintained within loop 41 while valve 47 provides flow into reactor 51 via back pressure valve 49. Valve 49 may include a control valve or solenoid valve controllable by a flow signal sensor or similar device. In one or more embodiments, a temperature controller (e.g., element 45) provides cooling to maintain the temperature of slurry 35 below the boiling point of chlorinated hydrocarbons (e.g., below 77°C for carbon tetrachloride). In a particular embodiment, the loop temperature is maintained from about 0°C to about 80°C; in other embodiments, the loop temperature is maintained from about 5°C to about 60°C; and in still other embodiments, the loop temperature is maintained from about 10°C to about 40°C.

[0023] In one or more embodiments, the concentration of Lewis acid (e.g., ferric chloride) 33 in slurry 35 can be expressed as a percentage of solids (dispersed and soluble solids) within the liquid weight. In one or more embodiments, the percentage of solid ferric chloride in slurry 35 can be from about 1% by weight to about 15% by weight, in other embodiments, the percentage is from about 2% by weight to about 10% by weight, and in other embodiments, the percentage is from about 3% by weight to about 7% by weight.

[0024] Synthesis of 1,1,2,3-tetrachloropropene

[0025] According to embodiments of the present invention, a crude 1,1,1,2,3-pentachloropropane feed stream can be directly processed by reactive distillation to form 1,1,2,3-tetrachloropropene. This method is generally known in the art, and therefore, U.S. Publication No. 2009 / 0216055A1 is incorporated herein by reference. As described above, according to embodiments of the present invention, reactive distillation is performed by heating the crude product stream within a forced circulation reboiler.

[0026] The reactive distillation method of one or more embodiments can be referred to Figure 2 Describe, Figure 2 A reactive distillation system 101 including a distillation column 103 and a reboiler 123 is shown. As is generally known in the art, column 103 includes a bottom zone 103A, in which a liquid form of column bottom 106 (which typically comprises about 3-5% solids) is collected and forms a liquid surface 106A. Column 103 also includes a packed zone 103B [with packing material 104 (e.g., grid material) and / or tray 104 located therein], and an exit tray 108. At the upper end of column 103, column 103 includes a top space 103C through which vapor exits column 103.

[0027] In one or more embodiments, the reboiler 123 (also referred to as forced circulation boiler 123) may comprise a single-pass or multi-pass reboiler. In a particular embodiment, as described below, the heating fluid or medium travels along the shell side through the reboiler 123. The practice of the invention is not limited to the type of heating fluid used and may include, for example, steam.

[0028] Distillation column 103 and reboiler 123 are in fluid communication via reboiler loop 111. 1,1,1,2,3-pentachloropropane crude feed 71 enters column 103 at or near liquid level 106A, more specifically, into bottom 103A, where it becomes contained in bottoms 106. Other Lewis acid catalysts may be introduced into crude feed 71 via, for example, slurry 35 (as described above). Bottoms 106 enter loop 111 through outlet 105. The flow rate of bottoms 106 through loop 111 is regulated, for example, by pump 115. In one or more embodiments, the flow rate of bottoms 106 through loop 111 is maintained at a rate sufficient to reduce the tube wall temperature in reboiler 123, thereby inhibiting deposit reactions and / or formation in reboiler 123. Bottoms 106 enter reboiler 123 at inlet 125 and circulate along the tube side within reboiler 123. In one or more embodiments, the velocity of the bottom material 106 passing through the reboiler 123 is at least 1 m / s; in other embodiments, the velocity is at least 3 m / s; and in still other embodiments, the velocity is at least 5 m / s. In these or other embodiments, the velocity of the bottom material 106 passing through the reboiler 123 is from about 1 m / s to about 20 m / s; in other embodiments, the velocity is from about 2 m / s to about 12 m / s; and in still other embodiments, the velocity is from about 3 m / s to about 9 m / s.

[0029] As described above, the bottom material 106 travels along the tube side through the reboiler 123, where it is heated by heat transferred from a heating fluid 127 (e.g., steam) introduced through inlet 126 to the shell side of the bottom material 106. In one or more embodiments, the heat flux across the tubes in the reboiler 123 is less than 44 kW / m², in other embodiments less than 33 kW / m², and in still other embodiments less than 22 kW / m². In these or other embodiments, the heat flux across the tubes in the reboiler 123 is from about 5 kW / m² to about 44 kW / m², in other embodiments about 7 kW / m² to about 33 kW / m², and in still other embodiments about 10 kW / m² to about 22 kW / m².

[0030] Heating of bottom product 106 [containing 1,1,1,2,3-pentachloropropene and a Lewis acid catalyst (e.g., ferric chloride)] causes 1,1,1,2-pentachloropropane to be dehydrochlorinated to produce 1,1,2,3-tetrachloropropene.

[0031] Bottom material 106 exits the reboiler as a heated liquid at outlet 129 and is injected into column 103 at inlet 107, located below the packing zone 103B; in certain embodiments, bottom material 106 enters at or near liquid level 106A. Bottom material 106 exiting reboiler 123 through outlet 129 is heated to such an extent that at least some of the target components (e.g., 1,1,2,3-tetrachloropropene) flash (i.e., boil) due to the pressure differential experienced upon entering column 103, and at least a portion of it will travel through packing space 103B toward top space 103C and eventually exit vapor outlet 109. Furthermore, in one or more embodiments, reboiler 123 may be located at a lower height relative to the bottom of distillation column 103, thereby providing sufficient hydrostatic pressure to prevent premature boiling of the bottom material within reboiler 123. Therefore, the combination of fluid velocity in loop 111, heat reflux in reboiler 123, and pressure maintained in loop 111 is used to suppress deposit formation and / or reactions on the tube wall or in distillation column 103.

[0032] In one or more embodiments, vapor (from heating the bottom material 106) can be partially condensed at the fill space 103B, and at least a portion of the vapor can be removed from column 103 via the extraction tray 108. This condensate (rich in 1,1,2,3-tetrachloropropylene) can be recycled back into the process for a variety of advantageous uses. For example, the extraction stream 117B (which may be referred to as seal face flush 117B) can be directed to one or more pumps, such as pump 117A, to provide a constant seal flush, which advantageously maintains constant pressure on the rotating seal face and preserves the seal during prolonged normal operation. Furthermore, the extraction stream 117C (which may also be referred to as instrument flush 117C) can be routed to one or more instruments (e.g., horizontal instruments within the bottom area 103A), providing a constant flush on the instruments to prevent solids accumulation. In these or other embodiments, condensate from the extraction tray 108 can also be collected in tank 117, which advantageously allows for the accumulation of volume so that it can be used subsequently, for example, during reactor start-up.

[0033] As understood by those skilled in the art, the desired 1,1,2,3-tetrachloropropene will exit distillation column 103 as vapor stream 132 through vapor outlet 109. Vapor stream 132 can then proceed through condenser 136, causing the desired chlorinated hydrocarbon 138 (i.e., 1,1,1,2,3-pentachloropropane) to condense, which may also be referred to as condensate stream 138, while allowing the lighter material (and uncondensed material) to exit as light fraction stream 140. A portion of condensate stream 138 can be returned to column 103 via stream 139 through a distributor (not shown) and enters top space 103C for reflux to the packing section. The remaining condensate 138 is collected as the desired product. Depending on the desired level of purification, further distillation and purification of condensate 138 can be performed in downstream processing.

[0034] In addition, such as Figure 1 and Figure 2 As shown, slurry 35 containing Lewis acid from circulation loop 41 can be combined with 1,1,1,2,3-pentachloropropane feed stream 71 via valve 48 to provide sufficient Lewis acid to catalyze the dehydrochlorination reaction. Figure 2 Specifically, slurry 35 can be combined with 1,1,1,2,3-pentachloropropane crude stream 71 before it enters column 103. In other embodiments not shown, slurry 35 can be introduced directly into column 103 or loop 111.

[0035] Various modifications and variations will become apparent to those skilled in the art without departing from the scope and spirit of the invention. The invention should not be limited entirely to the illustrative embodiments set forth herein.

Claims

1. A method for producing 1,1,1,2,3-pentachloropropane, optionally in the presence of carbon tetrachloride, by introducing 1,1,1,3-tetrachloropropane, chlorine, and a Lewis acid catalyst, the method comprising: A Lewis acid catalyst, slurried in a chlorinated hydrocarbon from a slurry system, is introduced to chlorinate 1,1,1,3-tetrachloropropane to 1,1,1,2,3-pentachloropropane in the presence of the Lewis acid catalyst. The slurry is continuously stirred before introducing the 1,1,1,3-tetrachloropropane and chlorine, and this continuous stirring is caused by continuous circulation of the slurry through a slurry loop. The concentration of the Lewis acid catalyst in the slurry is substantially uniform. The chlorinated hydrocarbon is carbon tetrachloride, and the Lewis acid catalyst is ferric chloride. The slurry contains 3 to 7% by weight of the Lewis acid catalyst dispersed or dissolved in carbon tetrachloride. The 1,1,1,3-tetrachloropropane, chlorine, and Lewis acid catalyst are introduced into the reactor, and the slurry loop is maintained at a pressure exceeding the pressure inside the reactor.

2. The method as described in claim 1, wherein, The temperature of the slurry in the slurry circuit is maintained below the boiling point of carbon tetrachloride.

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