Process for producing highly pure chlorinated alkane

Abstract

Disclosed is a process for producing highly pure chlorinated alkane in which a chlorinated alkene is contacted with chlorine in a reaction zone to produce a reaction mixture containing the chlorinated alkane and the chlorinated alkene, and extracting a portion of the reaction mixture from the reaction zone, wherein the molar ratio of chlorinated alkane:chlorinated alkene in the reaction mixture extracted from the reaction zone does not exceed 95:5.

Claims

1. A method of synthesizing a fluorinated alkane, fluorinated alkene, chlorinated alkene, or chlorofluorinated alkene, comprising providing a feedstock of a highly pure chlorinated alkane composition comprising 1,1,1,2,3-pentachloropropane in amounts of at least about 99.8 wt % and oxygenated organic compounds in amounts of about 5 ppm to about 100 ppm.

2. The method according to claim 1, wherein the fluorinated alkene is 2,3,3,3-tetrafluoropropene.

3. The method according to claim 1, wherein the chlorofluorinated alkene is 2-chloro-3,3,3-trifluoropropene.

4. The method according to claim 1, wherein the chlorinated alkene is 1,1,2,3-tetrachloropropene.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1Primary conversion and principal conversion steps (1,1,3-trichloropropene conversion to 1,1,1,2,3-pentachloropropane)

(2) TABLE-US-00001 1 gaseous chlorine 2 column gas-liquid reactor 3 external circulation loop 4 external cooler 5 external circulation loop 6 1,1,3-trichloropropene feed stream 7 external circulation loop 8 1,1,1,2,3-pentachloropropane-rich stream 9 cooler 10 1,1,1,2,3-pentachloropropane-rich stream (feed to hydrolysis step, FIG. 2) 11 off-gas

(3) FIG. 2Hydrolysis step

(4) TABLE-US-00002 101 water stream 102 1,1,1,2,3-pentachloropropane-rich feed stream 103 washing tank 104 washing tank outlet 105 filter 106 filter cake 107 1,1,1,2,3-pentachloropropane-rich product stream 108 wastewater stream

(5) FIG. 3Distillation step

(6) TABLE-US-00003 201 1,1,1,2,3-pentachloropropane-rich feed stream (product stream 107, FIG. 2) 202 distillation boiler 203 distillation residue stream 204 filter 205 filter cake 206 heavies stream 207 vacuum distillation column 208 distillate stream 209 condenser 210 intermediate line 211 liquid divider 212 reflux stream 213.1 1,1,3-trichloropropene stream 213.2 1,1,1,3-tetrachloropropane stream 213.3 purified 1,1,1,2,3-pentachloropropane stream

EXAMPLES

(7) Abbreviations used:

(8) TCPe=1,1,3-trichloropropene

(9) PCPa=1,1,1,2,3-pentachloropropane

(10) HCE=hexachloroethane

(11) DCPC=dichloropropanoylchloride

(12) The present invention is now further illustrated in the following example.

Example 1Continuous Production of 1,1,1,2,3-pentachloropropane

(13) A schematic diagram of the equipment used to perform the primary conversion step and principal conversion step of the present invention is provided as FIG. 1. A liquid stream of 1,1,3-trichloropropene is fed via line 6 into an external circulation loop 3, 5, 7 connected to a column gas-liquid reactor 2. Gaseous chlorine is fed in the reactor 2 via line 1. The reactor 2 is includes a single primary reaction zone, namely circulation loop 3, 5, 7 and lower part of the reactor 2. The circulation loop 3, 5, 7 is provided with an external cooler 4 to control the temperature of the reaction mixture. Thorough mixing of 1,1,3-trichloropropene and chlorine is achieved within the primary reaction zone. The primary conversion step could equally be conducted in one or more other types of reactor, such as continuously stirred tank reactor/s.

(14) The operating temperature within the primary reaction zone is 0 C. to 20 C. Operating the reactor within this range was found to minimise the formation of pentachloropropane isomers, which are difficult to separate from the target product, 1,1,1,2,3-pentachloropropane. Thorough mixing of the reaction mixture and mild temperatures, but also controlling the proportion of 1,1,1,2,3-pentachloropropane present in the reaction mixture, was found to minimise serial reactions of 1,1,3-trichloropropene and the formation of 1,1,1,3,3-pentachloropropane (which is difficult to separate from 1,1,1,2,3-pentachloropropane). To increase the rate of reaction at the low temperatures, the reaction mixture is exposed to visible light.

(15) The reaction mixture is then passed up through the reactor 2 for the principal conversion step, which is performed as a reduced temperature conversion step. Cooling of the reaction mixture is achieved using cooling tubes, and the reaction mixture is passed through a series of upstream and downstream principal reaction zones (not shown), resulting in zonal chlorination of 1,1,3-trichloropropene. To drive the reaction towards completion, the reaction mixture in the downstream principal reaction zone is exposed to ultraviolet light. Advantageously, this fully utilizes the chlorine starting material such that the obtained reaction mixture which is extracted from the downstream-most principal reaction zone has very low levels of dissolved chlorine.

(16) Operating the principal reaction zones at such temperatures has been found to minimise the serial reactions of 1,1,3-trichloropropene, which result in the formation of unwanted and problematic impurities, such as hexachloropropane.

(17) A 1,1,1,2,3-pentachloropropane rich stream is extracted from reactor 2 via line 8. Off-gas is extracted from the reactor 2 via line 11. The 1,1,1,2,3-pentachloropropane rich stream is subjected to cooling using a product cooler 9 and passed via line 10 for a hydrolysis step. A schematic diagram illustrating the equipment used to conduct this step is presented as FIG. 2.

(18) In that equipment, the 1,1,1,2,3-pentachloropropane rich stream is fed into washing tank 103 via line 102. Water is fed into the washing tank via line 101 to form a biphasic mixture. The organic phase (containing the 1,1,1,2,3-pentachloropropane rich product) can easily be separated from the aqueous phase by the sequential removal of those phases via line 104. The extracted phases are filtered 105 with the filter cake being removed 106. The 1,1,1,2,3-pentachloropropane rich product is then fed via line 107 for further processing while wastewater is removed via line 108.

(19) The hydrolysis step is especially effective at removing oxygenated organic compounds, such as chlorinated propionyl chloride and their corresponding acids and alcohols, which may be formed during the processes of the present invention. While the formation of such compounds can be avoided by excluding the presence of oxygen from the upstream stages of the synthesis, doing so increases the cost of production. Thus, the hydrolysis step assists with the economic and straightforward removal of such otherwise problematic (owing to the difficulty of removing them, e.g. by distillation) impurities.

(20) To maximise the purity of the obtained 1,1,1,2,3-pentachloropropane, a vacuum distillation step was performed, using the apparatus shown in FIG. 3, namely a distillation boiler 202 and vacuum distillation column 207. Advantageously, the components of the distillation apparatus which come into contact with the process liquid and distillate are formed of non-metallic materials which prevents the formation of degradation products of the 1,1,1,2,3-pentachloropropane.

(21) The vacuum distillation column 207 is provided with a liquid side stream withdrawal which can be used to prevent contamination of the product stream with light molecular weight compounds which may be formed in the boiler.

(22) The 1,1,1,2,3-pentachloropropane rich product from the apparatus shown in FIG. 2 is fed into boiler 202 via line 201. A residue is extracted from the distillation boiler 202 via line 203, subjected to filtering using a filter 204. The filter cake is extracted from the system 205 and a heavies stream is extracted via line 206 and subjected to further processing.

(23) Distillate is taken from the distillation column 201 via line 208, fed via condenser 209, intermediate line 210 and liquid divider 211 to yield a streams of i) 1,1,3-trichloropropene via line 213.1 which is recycled to the primary reaction zone, ii) 1,1,1,3-tetrachloropropane via line 213.2 and purified 1,1,1,2,3-pentachloropropane via line 213.3. A reflux stream 212 from divider 211 is fed back into the vacuum distillation column 207.

(24) Using the apparatus and process conditions outlined above, 3062 kg of 1,1,3-Trichloropropene (113TCPe, purity 97.577%) was continuously processed with an average hourly loading 44.9 kg/h to produce 1,1,1,2,3-Pentachloropropane (11123PCPa). Basic parameters of the process are as follows:

(25) TABLE-US-00004 Basic parameters Reactor overall mean residence time (min) 375 Reactor temperature range ( C.) 1-30 Reactor pressure (kPa) 101 Overall reaction 113TCPe conversion (%) 91.3 Overall 11123PCPa reaction yield (mol PCPa/mol TCPe 97.9 converted, in %) Overall 11123PCPa yield including the all process steps 97.4 described in Example 1

(26) The full impurity profile of the purified product obtained in line 213.3. in FIG. 3 of the above-described embodiment is presented in the following table:

(27) TABLE-US-00005 Compound (% wt) Phosgene ND 1,1,3-Trichloroprop-1-ene 0.007 2,3-Dichloropropanoylchloride ND 1,2.3-Trichloropropane ND 2,3,3,3-Tetrachloroprop-1-ene 0.001 1,1,3,3-Tetrachloroprop-1-ene 0.003 1,1,1,3-Tetrachloropropane 0.002 1,1,2,3-Tetrachloroprop-1-ene 0.003 1,1,3,3,3-Pentachloroprop-1-ene 0.001 1,1,1,3,3-Pentachloropropane 0.004 hexachloroethane ND 2,3-Dichloropropanoicacid ND 1,1,1,2,3-Pentachloropropane 99.967 1,1,2,2,3-Pentachloropropane 0.001 1,1,1,3-Tetrachlororopropane-2-ol 0.001 1-Bromo-1,1,2,3-Tetrachloropropane ND 2-Bromo-1,1,1,3-Tetrachloropropane ND 1,1,1,3,3,3-Hexhachloropropane ND 1,1,1,2,3,3-Hexachloropropane 0.002 1,1,1,2,2,3-Hexachloropropane 0.001 1,2-Dibromo-1,1,3-Trichloropropane ND HCl as Cl ND H.sub.2O 0.005 ND means below 0.001% wt.

Example 2Ultra Pure Composition 1,1,1,2,3-Pentachloropropane (PCPA)

(28) The process of Example 1 was repeated four times and samples of 1,1,1,2,3-pentachloropropane were obtained following distillation using the apparatus illustrated in FIG. 3. Distillation was conducted at a pressure of around 15 mBar and at a maximum boiler temperature of 105 C. As can be seen in the following table, the process of the present invention enables highly pure PCPA, including very low levels of impurities, particularly 1,1,2,2,3-pentachloropropane which is very difficult to separate from 1,1,1,2,3-pentachloropropane using distillation. Note that the figures in this table are provided as percentages by weight of the composition.

(29) TABLE-US-00006 Trial Number Compound 2-1 2-2 2-3 2-4 Phosgene ND ND ND ND 1,1,3-Trichloroprop-1-ene 0.0014 0.0012 0.0006 0.0014 2,3-Dichloropropanoyl chloride ND ND ND ND 1,2.3-Trichloropropane ND ND ND ND 2,3,3,3-Tetrachloroprop-1-ene 0.0005 0.0002 <0.0001 0.0002 1,1,3,3-Tetrachloroprop-1-ene 0.0017 0.0021 0.0008 0.0015 1,1,1,3-Tetrachloropropane 0.0023 0.0013 0.0007 0.0013 1,1,2,3-Tetrachloroprop-1-ene 0.0018 0.0021 0.0008 0.0011 1,1,3,3,3-Pentachloroprop-1-ene ND ND ND ND 1,1,1,3,3-Pentachloropropane 0.002 0.0022 0.0009 0.0016 hexachloroethane ND ND ND <0.0001 2,3-Dichloropropanoic acid ND ND ND ND 1,1,1,2,3-Pentachloropropane 99.984 99.985 99.993 99.989 1,1,2,2,3-Pentachloropropane 0.0006 0.0009 0.0008 0.0009 1,1,1,3-Tetrachlororopropane-2-ol 0.001 0.0008 0.0006 0.0005 1-Bromo-1,1,2,3-Tetrachloropropane ND ND ND ND 2-Bromo-1,1,1,3-Tetrachloropropane ND ND ND ND 1,1,1,3,3,3-Hexachloropropane ND ND ND ND 1,1,1,2,3,3-Hexachloropropane 0.0006 0.0004 ND 0.0005 1,1,1,2,2,3-Hexachloropropane ND 0.0003 ND ND 1,2-Dibromo-1,1,3-Trichloropropane ND ND ND ND Moisture (mg/kg) 44 23 NP NP Iron (mg/kg) <0.05 0.05 NP NP HCl as Chlorides (mg/kg) 0.51 0.53 NP NP ND = below 1 ppm, NP = not performed

Example 3Effect of Water Treatment

(30) Crude 1,1,1,2,3-Pentachloropropane compositions were obtained using the apparatus depicted in FIG. 1 and described in Example 1 above, e.g. the compositions were obtained from line 10 in FIG. 1. One stream (Trial 3-1) was not subjected to a hydrolysis step, while the other was (Trial 3-2), using the apparatus shown in FIG. 2 and described in Example 1 above. The resulting crude compositions were then subjected to distillation. The purity of and oxygenated compound contents of the samples, pre- and post-distillation, are shown in the following table:

(31) TABLE-US-00007 Trial Number 3-1 3-2 Pre-distillation 1,1,1,2,3-Pentachloropropane 89.038 91.402 Sum of oxygenated as 0.006 0.001 propanoyl chlorides and their acids Post-distillation 1,1,1,2,3-Pentachloropropane 99.948 99.930 Sum of oxygenated as 0.006 <0.001 propanoyl chlorides and their acids

(32) As is apparent, the washing step can be successfully employed to minimise the content of oxygenated organic impurities in compositions rich in chlorinated alkanes of interest.

Example 4Influence of Molar Ratio of Chlorinated Alkene:Chlorinated Alkane on Impurity Formation

(33) A batch operated reactor consisting of a four neck glass flask equipped with a stirrer, thermometer, back cooler, feed and discharge neck and cooling bath was set up. The feedstock consisted of 1,1,3-Trichloropropene comprising perchloroethylene and oxygenated impurities in amounts observed in commercially sourced supplies.

(34) Minor amounts of HCl gas were formed and these together with traces of chlorine were cooled down by means of a back cooler/condenser and then absorbed in a caustic soda scrubber. Chlorine was introduced into the liquid reaction mixture via dip pipe in various amounts for a period of 90 minutes. The temperature of reaction was maintained at 26 to 31 C. Pressure was atmospheric. The chlorine was totally consumed during the reaction. The reaction mixture was sampled and analyzed by GC and the results of this analysis are shown in the following table:

(35) TABLE-US-00008 Trial No. 4-1 4-2 4-3 4-4 4-5 chlorine dosed 20% 40% 60% 80% 100% (mol % of stoichiometry) TCPe:PCPa 90:10 72:28 53:47 33:67 14:86 ratio in reaction mixture (mol %) HCE (w %) 0.015 0.025 0.040 0.064 0.099 DCPC (w %) 0.089 0.067 0.172 0.228 0.322 Other oxygenated 0.009 0.017 0.030 0.058 (w %)

(36) As can be seen, increasing the conversion of the chlorinated alkene starting material to the chlorinated alkane product of interest results in an increase in the formation of impurities in the reaction mixture. These disadvantageous results arise as conversion of the starting material to product approaches total conversion.

Example 5Influence of Molar Ratio of Chlorinated Alkene:Chlorinated Alkane on Isomeric Selectivity

(37) This example was carried out in as described in Example 4 above. 1,1,3-Trichloropropene (purity 94.6% containing 5% of 1,1,1,3-Tetrachloropropane as an impurity) was used as the feedstock.

(38) 4 trials at different reaction temperature were conducted. The samples of reaction mixture were taken at 80%, 90%, 95% and 100% of stoichiometric quantity of chlorine dosed (based on 113TCPe in the feedstock) and then analyzed by gas chromatography. The results of this analysis are shown in the following table:

(39) TABLE-US-00009 Chlorine dosed (mol % of 113TCPe in feedstock) Reaction 80% 90% 95% 100% Trial Nr. temp. 11133PCPA content in reaction mixture in % 5-1 6 C. 0.028 0.040 0.053 0.075 5-2 25 C. 0.040 0.055 0.071 0.099 5-3 45 C. 0.049 0.064 0.076 0.095 5-4 63 C. 0.056 0.071 0.086 0.112

(40) These results demonstrate that increasing the conversion of the chlorinated alkene starting material to the chlorinated alkane product of interest results in a decrease in the selectivity of the reaction towards the chlorinated alkane isomer of interest.

(41) These disadvantageous results arise as conversion of the starting material to product approaches total conversion.

Example 6Influence of Molar Ratio of Chlorinated Alkene:Chlorinated Alkane on Impurity Formation

(42) This chlorination step was carried out as described in Example 4 above. 1,1,3-Trichloropropene (purity 99.4%) was used as a feedstock.

(43) Chlorine was introduced into the liquid reaction mixture at 120% of the stoichiometric quantity towards feedstock 1,1,3-Trichioropropene for a period of 90 minutes and was totally consumed during the reaction. The reaction temperature was 80 C. and reactor pressure was atmospheric. The samples of reaction mixture were taken by 80%, 95%, 110% and 120% of stoichiometric quantity of the chlorine dosed was analyzed by gas chromatography. Reaction selectivity is expressed in the table below as a ratio between sum of major impurities (1,1,3,3-Tetrachloropropene, 1,1,1,2,3,3-Hexachloropropane, 1,1,1,2.2.3-Hexachloropropane) to the product 1,1,1,2,3-Pentachloropropane:

(44) TABLE-US-00010 Trial Number 6-1 6-2 6-3 6-4 chlorine dosed (mol % 80 95 110 120 of stoichiometry) TCPe:PCPa ratio in 22:78 11:89 0.6:99.4 0.2:99.8 reaction mixture (mol %) Sum of byproducts/ 3.51 3.59 4.28 6.34 11123PCPa (%)

(45) These results demonstrate that increasing the conversion of the chlorinated alkene starting material to the chlorinated alkane product of interest results in an increase in the formation of unwanted impurities. These disadvantageous results arise as conversion of the starting material to product approaches total conversion. As can be seen, the degree of conversion (and thus the formation of impurities) can advantageously and conveniently be achieved by controlling the amount of chlorine into the reaction zone, such that there is no molar excess of chlorine:chlorinated alkene starting material.

Example 7Removal of Oxygenated Impurities by Hydrolysis

(46) To demonstrate the effectiveness of the hydrolysis step of the present invention at removing oxygenated compounds from the chlorinated alkane product of interest, samples of crude reaction mixture reaction mixture were obtained using the apparatus depicted in FIG. 1 and described in Example 1 above, e.g. the composition was obtained from line 10 in FIG. 1. The content of a specific oxygenated compound known to be problematic in downstream reactions was analysed (Feed). The sample was then subjected to a hydrolysis step using the apparatus depicted in FIG. 2 and described above in Example 1, and the organic phase, e.g. the composition obtained from line 107 in FIG. 2 was analysed (After treatment). The results are shown in the following table:

(47) TABLE-US-00011 Content of specific Trial Number oxygenated compound (ppm) 7-1 Feed After treatment 2,3-Dichloropropanoyl chloride 937 23

(48) As can be seen from this example there is about 97.5% efficiency in the removal of this specific oxygenated impurity.