HK40001610B - Process for the production of chlorinated hydrocarbons - Google Patents

Description

FIELD OF THE INVENTION

The present invention provides processes for the production of 1,1,1,2,3-pentachloropropane.

BACKGROUND OF THE INVENTION

Hydrofluoroolefins (HFOs) have been proposed as "fourth generation" refrigerants. These compounds have also been proposed for use as blowing agents, biocides, and monomer feedstock. Most industrially useful synthetic techniques require chlorinated hydrocarbon feedstocks to produce the HFOs. In particular, 2,3,3,3-tetrafluoropropene (HFO-1234yf) can be produced by employing 1,1,2,3-tetrachloropropene (HCC-1230xa) feedstock.

U.S. 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 publication teaches that 1,1,1,2,3-pentachloropropane can be produced 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 the 1,1,1,3-tetrachloropropane to form 1,1,3-trichloropropene, and then the 1,1,3-trichloropropene reacts 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 either continuously or periodically and is generally maintained at 30 to 1000 ppm. The product is fed, either continuously or periodically, to a reactive distillation system where the 1,1,1,2,3-pentachloropropane is dehydrochlorinated to 1,1,2,3-tetrachloropropene in the presence of a Lewis acid catalyst such as the ferric chloride. The distillation system employed includes a reaction zone, a separation zone, and a condensing zone. The liquid in the reaction zone is heated and agitated. Heat can be provided through a jacket on the vessel, by internal heat exchangers, or by external heat exchangers, and the agitation can be provided via pump circulation or stirring.

Because 1,1,2,3-tetrachloropropene is an important feedstock for the synthesis of certain HFOs, there is a desire to improve the efficiency of the processes for the production of 1,1,2,3-tetrachloropropene.

US 2009/216055 A1 discloses a process for the production of 1,1,1,2,3-pentachloropropane by reaction of 1,1,1,3-tetrachloropropane, chlorine and a Lewis acid, e.g. ferric chloride. The Lewis acid is supplied in various forms to the reaction mixture, for example a solid anhydrous, dissolved in carbon tetrachloride or without solvent.

SUMMARY OF THE INVENTION

The present invention provides a process for producing 1,1,1,2,3-pentachloropropane according to claim 1 and a process for producing 1,1,1,2,3-pentachlorpropane according to claim 9. Further embodiments are disclosed in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic view of a system for the preparation of 1,1,1,2,3-pentachloropropane wherein the process includes a slurry loop for delivering Lewis acid to the reactor.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Embodiments of the invention are based, at least in part, on the discovery of a process for the synthesis of 1,1,1,2,3-pentachloropropane by chlorinating 1,1,1,3-tetrachloropropane, wherein one or more Lewis acid catalysts, such as ferric chloride, is delivered to a reaction vessel from a slurry system wherein the catalyst is slurried within a chlorinated hydrocarbon (e.g. carbon tetrachloride). It is believed that by separately preparing a catalyst slurry, efficiencies can be achieved and problems associated with the Lewis acid catalysts, such as handling problems and its propensity to absorb water, can be avoided. This process also will advantageously allow for more finite controls on the introduction of the catalyst to the reactor.

1,1,1,2,3-PENTACHLOROPROPANE SYNTHESIS

According to embodiments of the present invention, 1,1,1,2,3-pentachloropropane is prepared by introducing 1,1,1,3-tetrachloropropane, chlorine, Lewis acid catalyst, and optionally carbon tetrachloride. In this respect, U.S. Publication Number 2009/0216055A1 is mentioned. As the skilled person appreciates, the 1,1,1,3-tetrachloropropane is a liquid at reaction conditions, and therefore the chlorine and the Lewis acid catalyst are added to the 1,1,1,3-tetrachloropropane liquid, which may be included within a mixture with carbon tetrachloride. In one or more embodiments, the chlorine is added as a gas and can be added to the 1,1,1,3-tetrachloropropane liquid through, for example, a tube submerged into the liquid or via one or more gaseous dispersing elements within the liquid. As the skilled person appreciates, several Lewis acid catalysts have been employed as chlorination catalysts, and practice of embodiments of the invention are not limited to specific Lewis acid catalysts. 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, although the skilled person can readily extend the teachings herein to other chlorination catalysts.

According to embodiments of the present invention, the Lewis acid, such as ferric chloride, which is partially soluble in the reaction medium at reaction conditions, is introduced to the 1,1,1,3-tetrachloropropane liquid as a slurry dispersed (and partially dissolved) within a chlorinated hydrocarbon liquid, such as carbon tetrachloride. In one or more embodiments, the catalyst is maintained within a liquid dispersion through continuous agitation that may be provided by, for example, a continuous circulation loop that is in communication with the vessel that contains the 1,1,1,3-tetrachloropropane liquid.

The process of one or more embodiments of the present invention can be described with reference to Fig. 1. As shown, system 11 includes Lewis acid mix tank 21, which is in fluid communication with reactor 51 (which may be referred to as chlorination reactor 51) through a circulation loop 41. Slurry tank 21 receives chlorinated hydrocarbon (e.g. carbon tetrachloride) 31 through inlet 22 and Lewis acid catalyst 33 through inlet 23. Slurry tank 21 may also optionally receive other materials 34, such as additional solvents, catalysts, catalyst ligands, or recycle streams captured downstream in the process, through inlet 26. In one or more embodiments, carbon tetrachloride 31 may be fed continuously, or in other embodiments it may be periodically injected, into slurry tank 21 through inlet 22. Likewise, Lewis acid catalyst 33 may be periodically added to slurry tank 21, or in other embodiments, Lewis acid catalyst 33 may be continuously charged to slurry tank 21 by employing continuous feeding apparatus. For example, Lewis acid catalyst 33 can be charged to slurry tank 21 by employing a dustless bucket tipper.

A slurry 35 of carbon tetrachloride 31 and Lewis acid catalyst 33 is formed by agitating the mixture within slurry tank 21 via one or more mixing elements 24, which may include agitation devices or baffles. Mixing elements 24 may be operated in a manner to substantially disperse the Lewis acid catalyst within the chlorinated hydrocarbon liquid (e.g. carbon tetrachloride); in particular embodiments, agitation is sufficient to achieve a substantially homogeneous concentration of the Lewis acid within the chlorinated hydrocarbon.

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

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

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

In one or more embodiments, loop 41 is maintained at a pressure that is greater than the pressure within reactor 51; in particular embodiments, the pressure within loop 41 is sufficient to create flow into reactor 51 (when valve 47 is open) while taking into account potential gravitational assistance. As the skilled person will appreciate, sufficient pressure can be maintained within loop 41 while valve 47 provides flow into reactor 51 by back-pressure valve 49. Valve 49 may include a control valve or solenoid valve that can be controlled by a signal flow sensor or similar device. In one or more embodiments, temperature controls (e.g. element 45) provide cooling to maintain the temperature of slurry 35 below the boiling point of the chlorinated hydrocarbon (e.g. below 77 °C for carbon tetrachloride). In particular embodiments, the loop temperature is maintained at from about 0 to about 80 °C, in other embodiments from about 5 to about 60 °C, and in other embodiments from about 10 to about 40 °C.

In one or more embodiments, the concentration of Lewis acid (e.g. ferric chloride) 33 within slurry 35 may be represented as a percent solids (both dispersed and soluble) within the weight of liquid. In one or more embodiments, the percent solids ferric chloride within slurry 35 may be from about 1 to about 15 wt %, in other embodiments from about 2 to about 10 wt %, and in other embodiments from about 3 to about 7 wt %. Additionally, as shown in Fig. 1, slurry 35, which includes Lewis acid from circulation loop 41, can be combined with 1,1,1,2,3-pentachloropropane crude stream 71 through valve 48 to provide sufficient Lewis acid to catalyze the dehydrochlorination reaction.

Claims (9)

1. A process for producing 1,1,1,2,3-pentachloropropane by introducing 1,1,1,3-tetrachloropropane, chlorine, and Lewis acid catalyst, optionally in the presence of carbon tetrachloride, the process comprising introducing, from a slurry system, the Lewis acid catalyst as a slurry within a chlorinated hydrocarbon.
2. The process of claim 1, where the slurry is continuously agitated prior to introducing the slurry to the 1,1,1,3-tetrachloropropane and the chlorine.
3. The process of claim 2, where the continuous agitation takes place within a continuously-stirred slurry tank of the slurry system.
4. The process of claim 2, where the continuous agitation is caused by continuous circulation of the slurry through a slurry loop.
5. The process of any of the preceding claims, where the chlorinated hydrocarbon is carbon tetrachloride, and where the Lewis acid catalyst is ferric chloride.
6. The process of claim 4, where the 1,1,1,3-tetrachloropropane, chlorine, and Lewis acid catalyst are introduced within a reactor, and where the slurry loop is maintained at a pressure in excess of the pressure within the reactor.
7. The process of claim 5, where the slurry includes from 1 to 15 wt % of the Lewis acid catalyst dispersed or dissolved within the carbon tetrachloride, and where the temperature of the slurry within the slurry loop is maintained at a temperature below the boiling point of carbon tetrachloride.
8. The process of any of the preceding claims, where the concentration of the Lewis acid catalyst within the slurry is substantially homogenous.
9. A process for producing 1,1,1,2,3-pentachloropropane, the process comprising:

   (i) providing a slurry of a Lewis acid catalyst within a chlorinated hydrocarbon;

   (ii) continuously circulating the slurry through a slurry loop in fluid communication with a reactor; and

   (iii) introducing into the reactor 1,1,1,3-tetrachloropropane, chlorine, and the slurry.