GB2049668A

GB2049668A - Process for producing 1,1,1- trichloroethane

Info

Publication number: GB2049668A
Application number: GB8010529A
Authority: GB
Original assignee: Asahi Glass Co Ltd
Current assignee: AGC Inc
Priority date: 1979-05-22
Filing date: 1980-03-28
Publication date: 1980-12-31
Also published as: DE3011689A1; FR2457270B1; FR2457270A1; GB2049668B

Abstract

1,1,1-Trichloroethane is produced by reacting chlorine with 1,1-dichloroethane in a vapor phase coexisting with a liquid phase containing a catalyst having hydrogen-attracting activity, preferably by a photochlorination reaction. 1,1,1-Trichloroethane can be obtained with high selectivity and with a high rate of conversion.

Description

SPECIFICATION Process for producing I 1,1 -trichloroethane The present invention relates to a process for producing 1,1,1 -trichloroethane by reacting chlorine with 1,1-dichloroethane. More particularly, it relates to an improved process for producing 1,1,1trichloroethane by carrying out the reaction in a vapor phase coexisting with a liquid phase containing a specific catalyst.

It has been proposed to produce 1,1,1 -trichloroethane by an addition reaction of vinylidene chloride with hydrogen chloride or a chlorination of dichloroethane with chlorine. For the latter chlorination, thermal chlorination and a photochlorination processes are known and are classified as liquid phase and vapor phase processes. The chlorination of 1,1 -dichloroethane has the disadvantage of forming a substantial amount of by-product beside the desired 1,1,1 -trichloroethane. For example, in the process described in Japanese Patent Publication 19328/1966, the selectivity in favour of the required 1,1,1 -trichloroethane is about 65% and more than 30% of by-products are formed.

In the process for forming 1,1,1 -trichloroethane (hereinafter referred to as MC) by a reaction of 1 ,1 -dichloroethane (hereinafter referred to as DCE) with chlorine, the following disadvantages are found.

In the liquid phase reaction, the reaction temperature can be easily controlled, however, the selectivity in favour of the product is not high enough and the rate of conversion of DCE is not always high enough. In the vapour phase reaction, the selectivity in favour of the product can be made relatively high, but control of the reaction temperature is not easy and the difficulty of control becomes more serious when the ratio of the feeding of chlorine is increased to increase the rate of conversion of DCE.

When the reaction temperature is too high, the ratio of by-products such as carbon materials increases and prevents a smooth reaction whereby the selectivity in favour of the product is lowered. In order to overcome the disadvantages of the vapour phase photochlorination reaction, the starting material of DCE can be sprayed into a photoreactor so as to remove the heat of reaction (See Japanese Patent Publication No. 19328/1 966) or the starting material of DCE may be used in a molar excess based on chlorine and the light source cooled by jacket cooling so as to keep below the reaction temperature (See Japanese Unexamined Patent Publication No. 1 66/1962).

The inventors have studied various processes for producing MC by a reaction of DCE with chlorine.

The present invention provides a process for producing 1,1,1 -trichloroethane by a reaction of chlorine with 1,1-dichloroethane, wherein the chlorination is carried out in a vapor phase coexisting with a liquid phase containing a catalyst having hydrogen-attracting activity.

Using the process of the present invention it is possible to achieve a high rate of conversion and high selectivity in favour of 1,1,1 -trichloroethane. The heat of reaction can be removed so as to increase the ratio of chlorine to 1,1 -dichloroethane and to increase the rate of conversion of 1,1 -dichloroethane.

The rate of conversion of DCE can be easily increased and the selectivity towards MC can be increased by carrying out the chlorination in a vapor phase in the presence of a liquid phase containing the specific catalyst, such as iodine or an iodine compound. The combination of the liquid phase in the vapor phase reaction system is effective to remove the heat of reaction and thus control any increases of the temperature in the reaction system, whereby the ratio of chlorine to the starting material of DCE can be increased and the rate of conversion of DCE increased.

In the process of the present invention, it is important to carry out a vapor phase chlorination in the presence of a liquid phase containing the specific catalyst and particularly, it is preferable to select a vapor phase photochlorination reaction. The addition of a small amount of the specific catalyst such as iodine or an iodine compound is effective for chlorination in the liquid phase combined with the vapor phase and selectivity towards MC based on DC can be increased to greater than 80%. The presence of the liquid phase is effective to remove the heat of reaction whereby a smooth reaction can be performed even when a ratio of chlorine to DCE is increased to higher than 0.5.Thus, in accordance with the process of the present invention, the yield of the object product can be increased to a satisfactory level in an industrial process.

In the process of the present invention, the catalysts which are effective for increasing the selectivity towards MC are catalysts having hydrogen pull activity, i.e. catalysts which attract the hydrogen atom (at the tertiary position) of DCE. It is especially preferable to use a strongly nucleophilic reagent such as iodine or an iodine compound as the catalyst. The iodine compounds include (a) compounds which form free iodine by feeding chlorine; or (b) compounds which coordinate chlorine in the atmosphere of chlorine.The iodine compounds (a) include compounds having ionic iodine bonding such as the alkali metal iodides Lil, Nal, KI, Rbl and OsI and alkaline earth metal iodides such as Bel2, Mug12, Cal2, and Boa 12. The iodine compounds (b) include compounds having a covalent iodine bond, for example iodides of the Group illb elements such as Bl3, All3, Gal3 and Tit,:: iodides of the Group IVb elements such as Sil4, Gel2 and Sol2; iodides of the Group Vb elements such as Nl3, P214 and Ass3; iodides of the transition elements such as Til3, Vl2, Vl3, Curl3, My 12, Fel2, Col2, Nil2, Curl, and Znl2 and organic iodides such as iodomethane, iodoethane, iodopropane, iodobutane, iodomethylene, iodoform, iodoethyiidine, iodobenzene, diiodobenzene, iodotoluene and iodophenol.

In the process of the present invention, various other catalysts for attracting the hydrogen atom (at the tertiary position) can also be used and include various compounds having nitrogen, sulfur or oxygen atoms, for example amines such as pyridine and triethylamine; sulfur compounds such as carbon disulfide and thiophene and ethers such as dioxane.

In the process of the present invention, iodine, alkali metal iodides and organic iodides are especially effective as the catalysts. The catalyst can be added in small amounts such as molar ratio of 10-5 to 2 x 10-2, preferably 5 x 10-5 to 2 x 10-3 based on the DCE starting material.

The liquid phase present in the vapor chlorination zone can be the starting material DCE. Thus, in a preferred embodiment, it is preferable to recycle a part of a condensed solution obtained by cooling the reaction mixture obtained from the reactor. The reaction mixture includes the unreacted DCE, the desired product MO, and the by-products comprising HCI and chlorides and is obtained from the reactor as a mixture of vapor and liquid phases. When the reaction mixture is cooled, the unreacted DCE and the product MC are condensed into the solution whereas the by-products of HCI etc. are separated in the vapor phase. A part of the condensed solution can be recycled as the liquid phase into the reactor for the chlorination.The rest of the condensed solution is fed to a distillation and separation process to obtain the product MC.

The unreacted DCE separated from the product by the distillation can be recycled to the reactor for the chlorination as further starting material or added to the condensed solution for recycling. The temperature to which the reaction mixture obtained from the reactor is cooled is selected so as to condense and liquefy at least the unreacted DOE in the vapor phase and is usually less than 700C, preferably 10 to 500C. The cooling temperature can be varied by varying the pressure, it being possible to use a reduced pressure or an elevated pressure. The amount of the liquid phase in the vapor phase chlorination zone is preferably in a range of 0.5 to 50 vol., preferably 1 to 10 vol. per 100 vol. of the total of the vapor phase and the liquid phase.When the ratio is too small, there is little difference from the conventional vapor phase chlorination as regards control of the reaction temperature. On the other hand, when the ratio is too large, there is little difference from the conventional liquid phase chlorination the rate of conversion of DOE and selectivity towards the desired product. When the condensed solution from the reaction mixture is recycled, amount recycled can be varied within a range compatible with the coexistence of the liquid phase and the vapor phase. It can suitably be in a range of 0.2 to 200 mole, preferably 5 to 50 mole, per 1 mole of the total of chlorine and DCE newly fed into the chlorination zone.

The liquid phase coexisting in the vapor phase chlorination zone is preferably made of the abovementioned condensed solution for the recycling, but is is possible to use DCE fed as the starting material in liquid form as a part of the coexisting liquid phase.

The small amount of catalyst such as iodine or an iodine compound which is used can be mixed with the recycled condensed solution to feed it into the reactor or can be added to the newly fed DGE to feed it into the reactor. When the reaction mixture discharged from the reactor is cooled to condense it, the specific catalyst remains in the condensed solution. Therefore, the condensed solution can be recycled to reuse the catalyst.

The reaction of chlorine with DOE can be carried out under various reaction conditions as a vapor phase reaction in the presence of the liquid phase. The reaction temperature is controlled by the coexistence of the liquid phase and usually a relatively low temperature is maintained such as 50 to 1 5000, preferably 60 to 1 3000. The ratio of chlorine can be relatively higher than in the conventional process and the molar ratio of chlorine to DOE newly fed into the reactor for the chlorination is usually in a range of 0.3 to 0.9, preferably about 0.5 to 0.8. The reaction can be effectively performed at atmospheric pressure but this can be increased so as to increase the reaction velocity.When iodine or an iodine compound which forms free iodine in the presence of chlorine is used as the catalysat, it is possible to feed the catalyst at the desired concentration by using a concentrated iodine solution obtained by dissolving iodine or the iodine compound in DCE at high concentration in a different tank and if necessary, feeding chlorine to liberate iodine before feeding.

The reaction of the present invention is preferably performed by a vapor phase photochlorination.

It is not indispensable to irradiate the reactor, but the induction period can be shortened by the photoirradiation of the reactor.

When a part of the non-condensed gas containing the HCI by-product as a main component is discharged from the reactor and recycled, the gas-liquid contact efficiency in the reactor can be increased and the heat of reaction can be effectively removed. The reaction mixture is obtained as a mixture of the vapor phase and the liquid phase, and accordingly the recycling of the non-condensed gas containing HCI as a main component to the reactor as the vapor phase can be attained by recycling a part of said reaction mixture. The reaction mixture can be separated into the vapor and liquid phases by a gas-liquid separator and the separated vapor phase can be recycled. When the non-condensed gas is recycled to the reactor, it can be mixed with the DCE starting material and the two fed to the reactor.

DCE can be partially or completely vaporized or misted by feeding the non-condensed gas with it to the reactor. The amount of the non-condensed gas containing HOl as a main component can be varied in a broad range and the molar ratio of the non-condensed gas to the total of DCE and chlorine newly fed into the reactor is usually 0.5 1 to 50:1, preferably 3 1 to 30:1.

In a preferred embodiment of the present invention, the following steps are employed. DCE and chlorine are fed, together with the condensed solution being recycled, into the reactor to react them by vapor plase chlorination in the presence of the liquid phrase. in this case, the non-condensed gas can be fed together with said materials into the reactor. The reaction mixture containing MC, DCE, HCI and heavy materials such as 1,1 ,2-trichloroethane is obtained as a mixture of vapor and liquid phases from the reactor. The reaction mixture can be partially recycled or can be separated into vapor and liquid phases by a gas-liquid separator and the separated vapor phase discharged by itself or after separating organic materials in a condenser.Some or all of the separated vapor phase can be recycled to the reactor for use as the non-condensed gas. The liquid phase and the condensed solution are collected in a condensed solution tank. A part of the condensed solution is discharged and a desired amout is recycled to the reactor. The condensed solution discharged is fed into a light material distillation column so as to obtain DCE and HCI as the distillate. At least a part of the DCE is recycled as further starting material to the reactor. In this case, HCI can be recycled as the non-condensed gas to the reactor. The mixture of the condensed MC, iodine or the iodine compound as the catalyst and the heavy materials is fed into a heavy material distillation column so as to obtain a MC distillate which is substantially pure.

Chlorine is fed in gaseous form or as a mixture with DCE as the starting material, into the reactor for the chlorination. In the case of the photochlorination, the reactor is equipped with a light source for irradiation with chemically active rays to initiate the photochlorination. The active rays suitably have a wavelength of 2500 to 5000, A. The light source can for example be a mercury vapor discharge lamp or a fluorescent lamp.

The present invention will be further illustrated by the following examples and references which are provided for purposes of illustration only.

EXAMPLE 1 In a reactor made of a heat resistant borosilicate glass having an inner diameter of 20 mm and a length of 500 mm, Raschig's rings made of heat resistant borosilicate glass were packed and the UV rays were externally radiated by a 100 W mercury discharge lamp during the reaction. As the starting materials chlorine was fed at a rate of 0.30 mole/hour and 1,1 -dichloroethane (containing 400 ppm of iodobenzene) was fed at a rate of 0.42 mole/hour from a top of the reactor. At the same time, a solution discharged from the reactor was recycled at a rate of 0.45 liter/hour from the top of the reactor. A reaction temperature was measured by moving a thermocouple in a glass tube at the center of the reactor to find 600C of the maximum temperature.

The reaction mixture discharged from the outlet of the reactor was separated into a vapor phase and a liquid phase by a gas-liquid separator. The vapor phase was cooled to 200C by a condenser to condense organic materials and the remained gas was fed into an alkaline absorbing column. The organic materials condensed and the liquid phase separated by the gas-liquid separator were stored in a tank. A part of the mixture was discharged and most of the mixture was recycled to the reactor. The result of the reaction is shown in Table 1.

REFERENCE 1: In accordance with the process of Example 1 except that iodibenzene was not added to 1,1 dichloroethane as the starting material, a photochlorination was carried out. The result is shown in Table 1.

REFERENCE 2: In accordance with the process of Example 1 except that 1,1 -dichloroethane as the starting material (no iodobenzene) was vaporized and fed into the reactor without any recycling of the solution discharged from the reactor, a vapor phase photochlorination was carried out. The result is shown in Table 1.

REFERENCE 3: In a 500 ml. reactor made of a borosilicate glass, a liquid phase photochlorination was carried out by externally applying a radiation by a 100 W mercury lamp, by feeding 1,1 -dichloroethane at a rate of 1.16 mole/hour at a molar ratio of chlorine to 1,1-dichloroethane of 0.60 at a reaction temperature of 500C under the atmospheric pressure. The result is shown in Table 1.

EXAMPLE 2: In the reactor of Example 1, a photochlorination was carried out by feeding chlorine at a rate of 0.31 mole/hour and feeding 1,1 -dichloroethane (containing 400 ppm of iodobenzene) at a rate of 0.40 mole/hour and recycling the solution discharged from the reactor at a rate of 0.10 liter/hour. The maximum temperature in the reactor was 1 1 OOC. The result is shown in Table 1.

EXAMPLE 3: In the reactor of Example 1, a photochlorination was carried out be feeding chlorine at a rate of 0.80 mole/hour and feeding 1,1 -dichlorethane (containing 300 ppm of iodopropane) at a rate of 1.60 mole/hour from the top of the reactor and recycling the solution discharged from the reactor at a rate of 2.0 liter/hour from the top of the reactor. The maximum temperature in the reactor was 580 C. The result is shown in Table 1.

EXAMPLE 4: In the reactor of Example 1, a photochlorination was carried out by feeding chlorine at a rate of 0.50 mole/hour and feeding 1,1 -dichlorethane (600 ppm of iodine was added and treated with chlorine) at a rate of 0.85 mole/hour from top of the reactor and recycling the solution discharged from the reactor at a rate of 0.40 liter/hour from the top of the reactor. The maximum temperature in the reactor was 780C. The result is shown in Table 1.

Table 1

Exp. 1 Ref. 1 Ref. 2 Ref. 3 Exp. 2 Exp. 3 Exp. 4 Molar ratio of Cl2/DCE 0.71 0.70 0.60 0.60 0.78 0.50 0.59 Reaction temp. ( ec) 60 60 270 50 110 58 78 Conversion of Cl2 (%) 99.0 99.9 99.8 99.9 99.9 99.0 99.3 Conversion of DCE (%) 66.3 65.2 56.0 55.0 68.7 46.9 54.8 Selectivity to MC (%) 83.8 71.5 74.8 69.0 81.0 82.4 83.5 Note: DCE: 1,1-dichloroethane MC: 1,1, 1-trichloroethane EXAMPLE 5:: In a reactor made of a heat resistant borosilicate glass having an inner diameter of 80 mm and a length of 300 mm, Rachig's rings made of heat resistant borosilicate glass were packed and the UV rays were externally radiated by a 1 KW high pressure mercury discharge lamp during the reaction. As the starting materials, chlorine was fed at a rate of 3.8 mole/hour and 1,1-dichloroethane (DCE) (containing 400 ppm of iodobenzene) was fed at a rate of 6.7 mole/hour from a top of the reactor. A gas discharged from the reactor which was separated by condensing organic material through a condenser at 200C, was recycled to the reactor at a rate of 1,200 liter/hour and a solution discharged from the reactor was recycled at a rate fo 31 liter/hour from the top of the reactor.The solution discharged from the reactor and the condensed solution were stored in a tank. A part of the mixture was discharged and most of the mixture was recycled to the reactor.

A reaction temperature was measured by moving a thermocouple in a glass tube at the center of the reactor to find 600C of the maximum temperature. The reaction was carried out at the atmospheric pressure. The result is shown in Table 2.

EXAMPLES 6 to 8: in accordance with the process of Example 5 except varying the reaction conditions, each photochlorination was carried out. In Examples 6 and 7, the reaction was carried out at the atmospheric pressure whereas in Example 8, the reaction was carried out under 2 atm. The results are shown in Table 2.

EXAMPLE 9: In the reactor of Example 5, a photochlorination was carried out by feeding chlorine at a rate of 3.8 mole/hour and feeding 1 ,1-dichloroethane (containing 400 ppm of iodobenzene) at a rate of 6.7 mole/hour from the top of the reactor and a solution discharged from the reactor was recycled at a rate of 31 liter/hour without recycling a gas discharged from the reactor. According to the measurement of the temperature distribution in the reactor, the maximum temperature was 1200C. The result is shown in Table 2.

REFERENCE 4: In the reactor of Example 5, a photochlorination was carried out by feeding chlorine at a rate of 3.8 mole/hour and feeding 1,1 -dichloroethane at a rate of 6.7 mole/hour from the top of the reactor without any recycling of a gas or a solution. The result is shown in Table 2.

Table 2

Exp. 5 Exp. 6 Exp. 7 Exp. 8 Exp. 9 Rest 4 Molar ratio of Cl ,/DCE 0.57 0.80 0.30 0.60 0.57 0.57 Rate of recycling solution (liter/hr.) 31.0 31.0 15.0 38.0 31.0 0 Rate of recycling gas (N-liter/hr.) 1,200 2,500 800 1,500 0 0 Reaction temp. ('C) 60 52 58 90 120 250 Conversion of Cli (%) 99.8 99.0 99.6 99.9 99.8 99.8 Selectivity to methylchloroform 84.0 84.2 84.2 84.0 81.9 73.4 EXAMPLES 10 to 13: In accordance with the process of Example 5, except varying the reaction conditions as described in Table 3, each photochlorination was carried out under the atmospheric pressure.

In Examples 10 and 11, 1,1-dichloroethane containing pyridine was used as a starting material. In Examples 12 and 13, 1,1 -dichloroethane containing thiophene was used as a starting material. The result is shown in Table 3.

Table 3

Exp. 10 Exp. 11 Exp. 12 Exp. 13 Molar ratio of CiJDCE 0.45 0.58 0.30 0.60 Rate of recycling solution (liter/hr.) 25.0 25.0 20.0 15.0 Rate of recycling gas (liter/hr.) 1,000 1,500 2,000 1,500 Reaction temp. (C) 57 57 54 58 Amount of catalyst kind (ppm) pyridine pyridine thiophene thiophene 5,000 1,000 1,000 2,000 Conversion of C1i(%) 99.7 99.8 99.9 99.8 Selectivity to methylchloroform (%) 83.9 78.8 80.1 84.1

Claims

CLAIMS:

1. A process for producing 1,1,1 -trichlorethane by a reaction of chlorine with 1,1 -dichloroethane, wherein the chlorination is carried out in a vapour phase coexisting with a liquid phase containing a catalyst having hydrogen-attracting activity.

2. A process according to claim 1, wherein said catalyst is iodine or an iodine compound.

3. A process according to claim 1 or claim 2, wherein said reaction is a photochlorination reaction.

4. A process according to any preceding claim, wherein the reaction temperature is in a range of 50 to 150 C.

5. A process according to any preceding claim, wherein the ratio of said liquid phase to the total of said vapor and liquid phases is 0.5 to 50 vol. per 100 vol.

6. A process according to any preceding claim, wherein a part of the reaction mixture is discharged from a reactor in which the reaction takes place and cooled to condense a gaseous component thereof and a part of the resulting condensed solution is recycled to said reactor for use as said liquid phase.

7. A process according to claim 6, wherein said discharged reaction mixture is cooled to a temperature lower than 700C.

8. A process according to claim 6 or claim 7, wherein the molar ratio of said condensed solution to the total of chlorine and 1,1 l,l-dichloroethane which are newly fed into said reactor is in a range of 0.2:1 to 200:1.

9. A process according to any preceding claim, wherein chlorine and 1,1 l,l-dichloroethane are newly fed to the reaction at a molar ratio of chlorine to 1,1 1,1-dichloroethane of 0.3 1 to 9 1.

10. A process according to any preceding claim, wherein at least a part of a non-condensed gas, containing HCI as a main component which is discharged from said reaction is recycled to said reaction in a vapor phase.

11. A process according to claim 10, wherein the molar ratio of said non-condensed gas to the total of chlorine and 1,1 -dichloroethane which are newly fed into said reaction is in a range of 0.5 to 50.

12. A process according to claim 1 substantially as herein described with reference to the Examples.