HK1227841B - Method for recovering chlorinated hydrocarbons - Google Patents

Description

FIELD OF THE INVENTION

Embodiments of the present invention are directed toward a method for recovering chlorinated hydrocarbons, especially chloropropanes, from crude reactant streams containing the chlorinated hydrocarbons.

BACKGROUND OF THE INVENTION

U.S. Patent No. 8,115,038 discloses a method for producing 1,1,1,2,3-pentachloropropane from 1,1,1,3-tetrachloropropane by heating 1,1,1,3-tetrachloropropane in the presence of ferric chloride and chlorine. The product of this direct chlorination is a mixture that is referred to as crude 1,1,1,2,3-pentachloropropane liquid. This crude may include, in addition to the 1,1,1,2,3-pentachloropropane, ferric chloride, 1,1,1,3-tetrachloropropane, 1,1,3-trichloropropene, and 1,1,2,3-tetrachloropropene, as well as hexachloropropane.

U.S. Patent No. 8,115,038 discloses that the 1,1,1,2,3-pentachloropropane can be directly treated within a reactive distillation column to produce 1,1,2,3-tetrachloropropene. In the alternative, this patent discloses that the 1,1,1,2,3-pentachloropropane can be further purified. While conventional techniques for purification may be evident to the skilled person, commercially efficient techniques for separating the 1,1,1,2,3-pentachloropropane from the crude 1,1,1,2,3-pentachloropropane liquid would be desirable.

SUMMARY OF THE INVENTION

One or more embodiments of the present invention provide a process for simultaneously producing purified streams of 1,1,2,3-tetrachloropropene and 1,1,1,2,3-pentachloropropane, the process comprising: providing a crude product stream containing 1,1,1,2,3-pentachloropropane, where the crude product stream includes ferric chloride; subjecting the crude product stream to reactive distillation within a distillation column having a bottom and a height under conditions sufficient to form a gradient within the column, wherein the distillation column includes a gradient of 1,1,1,2,3-pentachloropropane within the bottom of the column and part way up the height of the column, where the gradient includes a maximum concentration of 1,1,1,2,3-pentachloropropane at the bottom of the gradient and a maximum concentration of 1,1,2,3-tetrachloropropene at the top of the gradient; and removing the 1,1,1,2,3-pentachloropropane from the distillation column at a location from a side-draw tray within the gradient proximate to the maximum concentration of 1,1,1,2,3-pentachloropropane within the gradient, wherein packing material is provided at or near the side-draw tray to inhibit iron chlorides from entering the 1,1,1,2,3-pentachloropropane stream removed from the column via the side-draw tray.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic representation of a process for isolating 1,1,1,2,3-pentachloropropane according to one or more embodiments of the invention where a side draw tray is used in a reactive distillation column.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In embodiments of the present invention, the techniques of the present invention provide a process whereby both purified 1,1,1,2,3-pentachloropropane and 1,1,2,3-tetrachloropropene can be produced at desired levels. PROCESS FOR PRODUCING 1,1,1,2,3-PENTACHLOROPROPANE CRUDE

In one or more embodiments, a crude product stream containing 1,1,1,2,3-pentachloropropane may be produced by using known methods. In one or more embodiments, the crude product stream containing 1,1,1,2,3-pentachloropropane may be produced within a single reactor vessel where 1,1,1,3-tetrachloropropane is converted to 1,1,1,2,3-pentachloropropane in the presence of chlorine and ferric chloride.

CHARACTERISTICS OF 1,1,1,2,3-PENTACHLOROPROPANE CRUDE

In one or more embodiments, the crude product stream containing 1,1,1,2,3-pentachloropropane, which may also be referred to as crude 1,1,1,2,3-pentachloropropane, includes at least 50 wt. %, in other embodiments at least 60 wt. %, and in other embodiments at least 70 wt. % 1,1,1,2,3-pentachloropropane. In particular embodiments, the crude product stream may include from about 50 to about 90 or in other embodiments from about 70 to about 80 wt. % 1,1,1,2,3-pentachloropropane.

According to the invention, the crude product stream also includes ferric chloride. In one or more embodiments, the crude product stream includes at least 10 ppm, in other embodiments at least 25 ppm, in other embodiments at least 50 ppm, in other embodiments at least 80 ppm, and in other embodiments at least 100 ppm by weight ferric chloride. In particular embodiments, the crude product stream includes from about 50 to about 500 ppm or in other embodiments from about 70 to about 200 ppm by weight ferric chloride.

In one or more embodiments, the crude product stream also includes carbon tetrachloride. In one or more embodiments, the crude product stream includes at most 50 wt. %, in other embodiments at most 30 wt. %, and in other embodiments at most 20 wt. % carbon tetrachloride. In particular embodiments, the crude product stream includes from about 5 to about 30 wt. % or in other embodiments from about 10 to about 20 wt. % carbon tetrachloride.

In one or more embodiments, the crude product stream also includes 1,1,1,3-tetrachloropropane. In one or more embodiments, the crude product stream includes at most 20 wt. %, in other embodiments at most 10 wt. %, and in other embodiments at most 5 wt. % 1,1,1,3-tetrachloropropane. In particular embodiments, the crude product stream includes from about 0 to about 5 wt. % or in other embodiments from about 0 to about 2.5 wt. % 1,1,1,3-tetrachloropropane.

EMBODIMENT OF THE PRESENT INVENTION - SIDE DRAW

In an embodiment of the present invention, 1,1,1,2,3-pentachloropropane is isolated from a crude product stream including the 1,1,1,2,3-pentachloropropane by using a side draw tray positioned near the bottom of a packed column wherein reactive distillation of the crude 1,1,1,2,3-pentachloropropane stream is reactively distilled. This process takes advantage of the fact that 1,1,1,2,3-pentachloropropane has a lower vapor pressure (i.e., higher boiling point) than the 1,1,2,3-tetrachloropropene, the latter of which is produced by dehydrochlorination within the reactive distillation column. Thus, the reactive distillation column includes a gradient of 1,1,1,2,3-petachloropropane within the bottom of the column and part way up the height of the column, with the greatest concentration of 1,1,1,2,3-pentachloroproane existing in the bottom of the column. The side-draw tray is positioned at a location near the top of this gradient. According to the invention, sufficient packing material is provided at or near the draw tray to inhibit iron chlorides from entering the 1,1,1,2,3-pentachloropropane stream exiting the column via the side draw. In one or more embodiments, the gradient is defined by column packing. As the skilled person understands, this column packing may include structured packing materials such as metal structured packing materials. In other embodiments, the gradient is defined by the column design.

An example of this embodiment is shown in Fig. 1. In one or more embodiments, crude 1,1,1,2,3-pentachloropropane stream 12 enters reactive distillation column 100 via a recycle loop 104. As with the previous embodiments, ferric chloride 71 can be added to stream 12. Column 100 is operated under conditions of temperature and pressure sufficient to dehydrochlorinate 1,1,1,2,3-pentachloropropane to 1,1,2,3-tetrachloropropene.

In one or more embodiments, reactive distillation column 100 is operated at a temperature of at least 60 °C, in other embodiments at least 100 °C, and in other embodiments at least 150 °C. In these or other embodiments, reactive distillation column 100 is operated at temperatures of at most 200 °C, in other embodiments at most 150 °C, and in other embodiments at most 100 °C.

As shown in Fig. 1, column 100 includes column packing 106, and a side draw tray 110 at or near the bottom 112 of column packing 106. It is believed that 1,1,1,2,3-pentachloropropane concentrates within column 100 and is captured by tray 110 before returning to the bottom chamber 114 of column 100. The condensed material 117 captured at tray 110 is believed to include concentrated 1,1,1,2,3-pentachloropropane and is removed from column 100 via side draw stream 116, which may also be referred to as lower draw 116. In one or more embodiments, stream 116 may advantageously be substantially free of ferric chloride or other catalytic materials that could promote dehydrochlorination of the 1,1,1,2,3-pentachloropropane, and therefore efficient fractionating of stream 116 may be performed. The term "substantially free of ferric chloride" refers to that amount of ferric chloride or less that will not have an appreciable impact on the ability to further fraction the 1,1,1,2,3-pentachloropropane from other constituents within stream 116. In particular embodiments, stream 116 includes less than 100 ppm, in other embodiments less than 10 ppm, in other embodiments less than 5 ppm, and in other embodiments less than 1 ppm by weight ferric chloride.

Exiting column 100 at the top 118 is volatiles stream 120, which includes 1,1,2,3-tetrachloropropene. Volatiles fraction 120 may be condensed and collected from column 100 as a condensate stream 125 (which is rich in 1,1,2,3-tetrachloropropene) or volatiles fraction 120 can be routed to a compression and recovery unit 124 where the volatiles fraction 120 can be at least partially condensed and combined with condensate stream 125. Volatiles exiting compression and recovery unit 124 may be routed to an incinerator 127.

The bottom fraction 126 from reactive distillation column 100 can be routed to heavy ends purge 128. In one or more embodiments, a portion of bottom fraction 126, especially the fraction believed to contain iron chlorides, can be recycled back to one or more processes where ferric chloride is employed. For example, iron chlorides 129 can be recycled back to a reactor in which crude 12 is produced.

Accordingly, the process of this embodiment produces two enriched streams; the first stream (e.g., stream 116) includes concentrated 1,1,1,2,3-pentachloropropane and the second stream (e.g., stream 125) includes concentrated 1,1,2,3-tetrachloropropene. As with other embodiments, these two streams can be further purified to produce purified streams of 1,1,1,2,3-pentachloropropane and 1,1,2,3-tetrachloropropene, respectively.

For example, in one or more embodiments, lower draw 116 and condensate 125 can be further fractioned to remove compounds that are lighter than 1,1,2,3-tetrachloropropene (and 1,1,1,2,3-pentachloropropane). For example, streams 116 and 125 may be separately and individually routed to a distillation column 132 for further fractioning. Advantageously, a single column, such as column 132, may be used wherein stream 125 (which is rich in 1,1,2,3-tetrachloropropene) is routed to an elevated location in column 132 and stream 116 (which is rich is 1,1,1,2,3-pentachloropropane) is routed to a lower location in column 132.

In one or more embodiments, distillation column 132 can be operated at or under pressures greater than 0.051 bar (0.050 atmospheres), in other embodiments greater than 0.071 bar (0.070 atmospheres), in other embodiments greater than 0.096 bar (0.095 atmospheres), and in other embodiments greater than 0.106 bar (0.105 atmospheres). In these or other embodiments, column 132 can be operated at or under pressures less than 0.253 bar (0.250 atmospheres), in other embodiments less than 0.172 bar (0.170 atmospheres), in other embodiments less than 0.132 bar (0.130 atmospheres), and in other embodiments less than 0.111 bar (0.110 atmospheres). In particular embodiments, distillation column 132 is operated at from about 0.051 bar (0.050 atmospheres) to about 0.253 bar (0.250 atmospheres) or in other embodiments from about 0.096 bar (0.095 atmospheres) to about 0.132 bar (0.130 atmospheres).

As shown in Fig. 1, volatiles fraction 133 from distillation column 132 may include those compounds more volatile than 1,1,1,2,3-pentachloropropane and 1,1,2,3-tetrachloropropene, and these compounds may be removed from the process as light ends purge 134.

The bottoms fraction 135 from distillation column 132, which includes both 1,1,1,2,3-pentachloropropane and 1,1,2,3-tetrachloropropene, may be further fractioned to isolate the 1,1,2,3-tetrachloropropene product, which is more volatile than the 1,1,1,2,3-pentachloropropane. For example, bottoms fraction 135 may be routed to a second distillation column 136.

In one or more embodiments, second distillation column 136 can be operated at pressures greater than 0.051 bar (0.050 atmospheres), in other embodiments greater than 0.071 bar (0.070 atmospheres), in other embodiments greater than 0.096 bar (0.095 atmospheres), and in other embodiments greater than 0.106 bar (0.105 atmospheres). In these or other embodiments, distillation column 136 can be operated at or under pressures less than 0.253 bar (0.250 atmospheres), in other embodiments less than 0.172 bar (0.170 atmospheres), in other embodiments less than 0.132 bar (0.130 atmospheres), and in other embodiments less than 0.111 bar (0.110 atmospheres). In particular embodiments, second distillation column 136 is operated at from about 0.051 bar (0.050 atmospheres) to about 0.253 bar (0.250 atmospheres) or in other embodiments from about 0.096 bar (0.095 atmospheres) to about 0.132 bar (0.130 atmospheres).

In one or more embodiments, second distillation column 136 is operated at conditions to isolate 1,1,2,3-tetrachloropropene in a volatiles fraction 139 where 1,1,2,3-tetrachloropropene product 140 can be isolated and collected. Bottoms fraction 138 from second distillation column 136, which contains 1,1,1,2,3-pentachloropropane product, may be further fractioned to isolate the 1,1,1,2,3-pentachloropropane from other compounds within bottoms fraction 138. For example, bottoms fraction 138 may be routed to a third distillation column 142.

In one or more embodiments, third distillation column 142 can be operated at pressures greater than 0.051 bar (0.050 atmospheres), in other embodiments greater than 0.071 bar (0.070 atmospheres), in other embodiments greater than 0.096 bar (0.095 atmospheres), and in other embodiments greater than 0.106 bar (0.105 atmospheres). In these or other embodiments, third distillation column 142 can be operated at or under pressures less than 0.253 bar (0.250 atmospheres), in other embodiments less than 0.172 bar (0.170 atmospheres), in other embodiments less than 0.132 bar (0.130 atmospheres), and in other embodiments less than 0.111 bar (0.110 atmospheres). In particular embodiments, third distillation column 142 can be operated at from about 0.051 bar (0.050 atmospheres) to about 0.253 bar (0.250 atmospheres) or in other embodiments from about 0.096 bar (0.095 atmospheres) to about 0.132 bar (0.130 atmospheres).

Compounds having a lower boiling point than 1,1,1,2,3-pentachloropropane may form a volatiles fraction 143 and be removed from third distillation column 142 as middle ends purge 144. An example of a compound having a lower boiling point than 1,1,1,2,3-pentachloropropane that is likely to be removed as middle ends purge 144 is pentachloropropene. The bottoms fraction 147 from third distillation column 142 is removed as heavy ends purge 146. The desired 1,1,1,2,3-pentachloropropane product 150 is removed from third distillation column 142 as stream 148.

EXAMPLES

In order to demonstrate the practice of the present disclosure, the following examples have been prepared and tested. The examples should not, however, be viewed as limiting the scope of the present disclosure. The claims will serve to define the invention.

The sample experiments set forth herein were conducted within a 20-tray, 25mm i.d. vacuum-jacketed Pyrex laboratory distillation column equipped with a 1-liter bottoms flask and means for operation at sub-atmospheric pressure. A swinging-bucket type reflux head allowed controlled withdrawal of overhead product. The bottoms flask of the distillation column was charged, as batch, with crude 1,1,1,2,3-pentachloropropane, which was prepared in accordance with the teachings of U.S. Pat. No. 8,115,038 . The Table I provides amount of crude used in each example together with the relative amounts of some relevant constituents thereof. The column pressure was adjusted to about 0.24-0.27 bar (0.24-0.27 atmospheres), and sufficient heat was applied to the bottoms flask to reflux liquid in the column (e.g. about 140 -150 °C). The distillation was conducted over several hours. The formation rate of 1,1,2,3-tetrachloropropene, as indicated by a measurement within a specified time interval, was evaluated and representative data is reported in the Table I. TABLE I

Inhibitor	N/A	TBP	TBP	Dodecane	Dodecane
Inhibitor Amount (ppmw)	N/A	1532	155	1078	2215
Molar Ratio Inhibitor: Ferric Chloride	N/A	10:1	1:1	10:1	20:1
Sample Weight (g)	1118.6	1162.2	1096.8	1011.1	943.6
1,1,1,2,3-pentachloropropane (%)	77.725	77.725	77.725	78.006	77.984
Ferric Chloride (ppm)	93	93	93	93	93
1,1,2,3-tetrachloropropene (%)	0.643	0.643	0.643	0.667	0.755
Overhead 1, 1,2,3-tetrahloropropene
1-4 hours reflux (%)	25.441	2.817	2.974	6.552	4.706
4-6 hours reflux (%)	12.725	1.003	0.901	3.005	1.578

TABLE I

*Not according to the present invention

As generally indicated by the Table I, in the absence of an inhibitor, 1,1,1,2,3-pentachloropropane was readily converted to 1,1,2,3-tetrachloropropene as a result of the distillation process; i.e. dehydrochlorination took place. When TBP was present, however, even at amounts as low as 1 mole of TBP per mole of ferric chloride, dehydrochlorination to 1,1,2,3-tetrachloropropene was advantageously inhibited. Similar advantageous results were achieved in the presence of dodecane, although analysis shows that greater amounts of dodecane may be desirable to achieve more appreciable inhibition of the dehydrochlorination reaction.

In a second experiment, which generally used the same laboratory equipment used in the first experiment, crude 1,1,1,2,3-pentachloropropane, prepared according to the teachings of U.S. Patent No. 8,115,038 , was subjected to low pressure distillation. Specifically, the targeted pressure was 0.03 bar (0.03 atmospheres), although limits of the experimental design initially precluded reaching that target. The particulars of the experiment are provided in Table II. In particular, the distillation was conducted over several hours, and the rate of 1,1,2,3-tetrachloropropene within the overhead product was determined as provided in Table II.

1,1,1,2,3-pentachloropropane (%)	1.024	0.046	8.308	0.426	0.102
Ferric Chloride (ppm)	131	-	-	-	-
1,1,2,3-tetrachloropropene (%)	78.810	4.234	87.318	99.480	99.877
Pressure	N/A	0.14	0.05	0.03	0.03

As generally shown in Table II, distillation at low temperatures inhibited conversion of the 1,1,1,2,3-pentachloropropane to 1,1,2,3-tetrachloropropene; i.e., dehydrochlorination was inhibited.

Claims (2)

1. A process for simultaneously producing purified streams of 1,1,2,3-tetrachloropropene and 1,1,1,2,3-pentachloropropane, the process comprising:

   a. providing a crude product stream containing 1,1,1,2,3-pentachloropropane, where the crude product stream includes ferric chloride;

   b. subjecting the crude product stream to reactive distillation within a distillation column having a bottom and a height under conditions sufficient to form a gradient within the column, wherein the distillation column includes a gradient of 1,1,1,2,3-pentachloropropane within the bottom of the column and part way up the height of the column, where the gradient includes a maximum concentration of 1,1,1,2,3-pentachloropropane at the bottom of the gradient and a maximum concentration of 1,1,2,3-tetrachloropropene at the top of the gradient; and

   c. removing the 1,1,1,2,3-pentachloropropane from the distillation column at a location from a side-draw tray within the gradient proximate to the maximum concentration of 1,1,1,2,3-pentachloropropane within the gradient, wherein packing material is provided at or near the side-draw tray to inhibit iron chlorides from entering the 1,1,1,2,3-pentachloropropane stream removed from the column via the side-draw tray.
2. The process of claim 1, where the packing material is metal structured packing material.