WO2009122438A1

WO2009122438A1 - Improved process for heat stable chlorinated paraffin wax

Info

Publication number: WO2009122438A1
Application number: PCT/IN2009/000205
Authority: WO
Inventors: Rasika Satam; Yogesh Borole; Sisir Kumar Mandal; Amol Niphade
Original assignee: Aditya Birla Science & Technology Co. Limited
Priority date: 2008-03-31
Filing date: 2009-03-26
Publication date: 2009-10-08

Abstract

A method for synthesis of chlorinated paraffin, the method comprising reacting a C_8-24 paraffinic hydrocarbon with chlorine gas in the presence of 100 to 1500 ppm of an stabilizer at a temperature in the range of 25 C to 200 C and at a pressure in the range of 1 to 3 atmospheres.

Description

IMPROVED PROCESS FOR HEAT STABLE CHLORINATED PARAFFIN WAX

FIELD OF THE INVENTION

The invention relates to a method for synthesis of chlorinated paraffin. The invention also relates to the chlorinated paraffin and to the compositions thereof.

BACKGROUND OF THE INVENTION

Chlorinated paraffins are widely used in plasticizers and flame retardant formulations. They are also used in formulations having applications as additives in metal working fluids, in sealants, paints and coatings. Paraffins are usually chlorinated with chlorine gas in a jacketed reactor provided with a coolant liquid. To improve the productivity of the chloroparaffin products, high reactivity of the paraffin with chlorine gas and high thermal stability of the chloroparaffin product are desired. During conventional chlorination methods, however, the reactivity of paraffins with chlorine gas is limited. Further, the chloroparaffin products are usually thermally unstable and would undergo decomposition by the elimination of hydrogen chloride. Various methods are known wherein stabilizing compounds are used to improve the heat stability of the chloroparaffin product. US patent 2722557 discloses a method for paraffin chlorination in the presence of a glycolic stabilizer. However, when glycols are used, the overall chlorine content of the chloroparaffin product is reduced, which is not desirable. US patent 3284519 discloses a method wherein diazo carboxylate is used as a stabilizer for increasing the thermal stability of chloro paraffin product. Diazo carboxylate is, however, not environmentally benign and is therefore not recommended. There is a need for a synthetic method to obtain thermally stable chloroparaffin without the above mentioned disadvantages.

OBJECTS OF THE INVENTION

An object of the invention is to provide a method for synthesis of chlorinated paraffins wherein the reactivity of chlorine gas with paraffins and the thermal stability of the chloroparaffin product are improved.

Another object of the invention is to provide thermally stable chlorinated paraffin suitable for a wide range of applications.

A further object of the invention is to provide compositions comprising thermally stable chlorinated paraffins.

SUMMARY OF THE INVENTION

The invention is based on the finding that when an activity control agent selected from organo tin compounds and mercaptides, carboxylates, sulfides and maleates of a group II and a group 14 metal is used in paraffin chlorination reactions, the chlorination reactivity and thermal stability of the chloroparaffin product are significantly increased. The improvement in chlorination reactivity and in the thermal stability of the product is advantageous in increasing the productivity and reducing the cost of synthesis.

In accordance with the present invention, there is provided a method for synthesis of chlorinated paraffin, the method comprising reacting a C_8-24 paraffmic hydrocarbon with chlorine gas in the presence of 100 to 1500 ppm of an activity control agent at a temperature in the range of 25°C to 200⁰C and at a pressure in the range of 1 to 3 atmospheres. Typically, the hydrocarbon is preheated at a temperature in the range of 50⁰C to 80⁰C.

Typically, the activity control agent is selected from a group consisting of an organo tin compound and mercaptides, carboxylates, sulfides and maleates of a group II and a group 14 metal.

Typically, the group II metal is selected from calcium and barium and the group 14 metal is selected from tin and lead

Typically, the activity control agent is an alkyl mercaptide.

Typically, the reaction is carried out in the presence of 100 to 1500 ppm of activity control agent.

Typically, the reaction is carried out at a temperature in the range of 60⁰C to 150⁰C.

Typically, chlorinated paraffin is synthesized by the method of the present invention.

Typically, a composition comprising the chlorinated paraffin is disclosed.

DETAILED DESCRIPTION OF THE INVENTION

Accordingly, the invention provides a method for synthesis of chloroparaffin products wherein an activity control agent is used. The following terms, wherever used in the description herein and in the appended claims, have the meaning defined below.

The term normal paraffin refers to paraffin having the characteristics as given in table 1.

Table 1: Characteristics of normal paraffin

The term light normal paraffin refers to paraffin having characteristics as given in table 2:

Table 2: Characteristics of light normal paraffin

The term raw paraffin refers to a mixture of normal paraffin and light normal paraffin.

The term activity control agent refers to any additive, accelerator, promoter or catalyst that when used in the paraffin chlorination reaction at least improves the heat stability of the chloroparaffin product and increases the reaction rate. In one embodiment, the invention provides a method for synthesis of a chlorinated paraffin, the method comprising reacting a C_8-24 paraffinic hydrocarbon with chlorine gas in the presence of 100 to 1500 ppm of an activity control agent at a temperature in the range of 25°C to 200⁰C and at a pressure in the range of 1 to 3 atmospheres.

In another embodiment, the invention provides a method for synthesis of a chlorinated paraffin, the method comprising reacting a Cg_-24 paraffinic hydrocarbon with chlorine gas in the presence of 100 to 1500 ppm of an activity control agent at a temperature in the range of 25⁰C to 200⁰C and at a pressure in the range of 1 to 3 atmospheres wherein the activity control agent is selected from a group consisting of an organo tin compound and mercaptides, carboxylates, sulfides and maleates of a group II and a group 14 metal.

In another embodiment, the invention provides a method for synthesis of a chlorinated paraffin, the method comprising reacting a C_8-24 paraffinic hydrocarbon with chlorine gas in the presence of 100 to 1500 ppm of an activity control agent at a temperature in the range of 25°C to 200⁰C and at a pressure in the range of 1 to 3 atmospheres wherein the activity control agent is selected from a group consisting of an organo tin compound and mercaptides, carboxylates, sulfides and maleates of a group II and a group 14 metal and the hydrocarbon is preheated at a temperature in the range of 50⁰C to 80⁰C.

In another embodiment, the invention provides a method for synthesis of a chlorinated paraffin, the method comprising reacting a C_8-24 paraffinic hydrocarbon with chlorine gas in the presence of 100 to 1500 ppm of an activity control agent at a temperature in the range of 25°C to 200⁰C and at a pressure in the range of 1 to 3 atmospheres wherein the group II metal is selected from calcium and barium and the group 14 metal is selected from tin and lead.

In another embodiment, the invention provides a method for synthesis of a chlorinated paraffin, the method comprising reacting a C_8-24 paraffinic hydrocarbon with chlorine gas in the presence of 100 to 1500 ppm of an activity control agent at a temperature in the range of 25°C to 200⁰C and at a pressure in the range of 1 to 3 atmospheres wherein the activity control agent is an alkyl mercaptide.

In another embodiment, the invention provides a method for synthesis of a chlorinated paraffin, the method comprising reacting a C_8-24 paraffinic hydrocarbon with chlorine gas in the presence of 500 to 800 ppm of an activity control agent at a temperature in the range of 25°C to 200⁰C and at a pressure in the range of 1 to 3 atmospheres.

In another embodiment, the invention provides a method for synthesis of chlorinated paraffin, the method comprising reacting a C_8-24 paraffinic hydrocarbon with chlorine gas in the presence of 100 to 1500 ppm of an activity control agent at a temperature in the range of 60⁰C to 150⁰C and at a pressure in the range of 1 to 3 atmospheres.

In yet another embodiment, the invention provides chlorinated paraffin synthesized by reacting a C_8-24 paraffinic hydrocarbon with chlorine gas in the presence of 100 to 1500 ppm of an activity control agent at a temperature in the range of 25°C to 200⁰C and at a pressure in the range of 1 to 3 atmospheres. In a further embodiment, the invention provides a composition comprising chlorinated paraffin synthesized by reacting a C_8-24 paraffinic hydrocarbon with chlorine gas in the presence of 100 to 1500 ppm of an activity control agent at a temperature in the range of 25⁰C to 200⁰C and at a pressure in the range of 1 to 3 atmospheres.

The method of the invention provides chloroparaffin products having relatively high thermal stability. The method is usually carried out in a jacketed reactor provided with a coolant liquid for controlling the reactor temperature and a pre-heater for heating the paraffin. Additionally, the reactor can have an overhead gas-liquid separating arrangement and a gas distribution arrangement. A glass reactor, a lead or a steel reactor can be used for carrying out the method.

The paraffin feed used in the method of the invention can be a normal paraffin, a light normal paraffin or a mixture of the two paraffins. Advantageously, the paraffin is preheated to around 60⁰C before chlorination reaction. The chlorine gas used for the reaction can be obtained from a membrane chlorine plant.

The activity control agent used in the method of the invention include organo tin compounds and mercaptides, carboxylates, sulfides and maleates of a group II and a group 14 metal. Advantageously, an alkyl tin mercaptide is used as the activity control agent. The activity control agent is used in the reaction in an amount ranging from 100 to 1500 ppm. Advantageously, 500 to 800 ppm of activity control agent is used.

The method of the invention is carried out at a temperature in the range of 25°C to 200⁰C and at a pressure in the range of 1 to 3 atmospheres. Advantageously, the method is carried out at a temperature in the range of 6O⁰C to 120⁰C and at a pressure of around 1 atmosphere.-

The invention also provides a chlorinated paraffin, having improved thermal stability, and compositions thereof. The chloroparaffin compositions can be used for various applications including metal working fluids, sealants, leather processing, in paints and coatings, carbonless copy paper and as flame retardants/softeners in rubbers, textiles, PVC and other polymers. The composition can contain a single chloroparaffin or a mixture of different chloroparaffins. Further, in addition to the chloroparaffin, the compositions can contain solvents and additives that can impart special characteristics and functionalities.

Apart from increasing rate of chlorination of the paraffins and yielding chloroparaffin products having improved thermal stability, the method of the invention could lead to considerable reduction in the formation of carbonaceous and pitchy products. The method of the invention could also reduce the amount of unreacted chlorine gas in the reactor, resulting in operational and cost benefits. Typically, the method of the invention has a batch cycle time reduced by 3 to 4 hrs as compared to the conventional methods.

The invention is further illustrated by way of the following non limiting examples.

In the examples and the results that follow, specific gravity and density of the chloroparaffin product is determined by using a hydrometer. Weight loss studies were performed by measuring loss in weight of final product after heating at a temperature of 18O⁰C for half an hour. Heat test was conducted by keeping a beaker containing the product in an oven at a temperature of 18O⁰C.

EXAMPLES

Example 1: Synthesis of chlorinated paraffin in the absence of activity control agent

In a lead-lined reactor of 10 TON capacity, 2.4 TON normal paraffin preheated to 60⁰C was taken for chlorination. The reactor was equipped with the cooling jacket, chlorine inlet sparger, off-gas outlet valve and temperature sensors. Arrangements were made for direct supply of chlorine gas at 30⁰C from the membrane chlorine plant. The reaction temperature was controlled with a combination of chlorine flow and cooling water-inlet flow. Off-gases of the reaction were passed through the water scrubber for removal of HCl- gas. The scrubber outlet was given to the caustic solution tank for converting the un-reacted chlorine into sodium hypochlorite. Chlorination reaction was run for 1400 minutes and the temperature was allowed to rise from 60⁰C to 120⁰C, more precisely from 70⁰C to 110⁰C during the reaction. At the end of 1400 minutes the chlorine flow was stopped and air flow to remove the HCl and trapped Cl₂ was started. The air was passed for 2 hours, meanwhile the reactor temperature dropped to 50⁰C. At this temperature the product was unloaded in the aeration tank; final aeration was done for 2 hr. 2 kg of epoxy soya stabilizer per 250 kg of chloroparaffin product was added to the product. Specific gravity was checked for analyzing the rate of reaction. Product quality was checked by weight loss and heat heat stability. The synthetic experiments carried out and the results obtained without the addition of any activity control agent using different paraffin feeds are displayed against experiment No.s 1 and 4 in table 3. Example 2: Synthesis of chlorinated paraffin in the presence of activity control agent

In a lead-lined reactor of 10 TON capacity, 2.4 TON normal paraffin and 12 g of butyl tin mercaptide (activity control agent), preheated to 60⁰C was taken for chlorination. The reactor was equipped with a cooling jacket, chlorine inlet sparger, off-gas outlet valve and temperature sensors. Arrangements were made for direct supply of chlorine gas at 30⁰C from a membrane chlorine plant. The reaction temperature was controlled with a combination of chlorine flow and jacketed cooling water-inlet flow. Off-gases of the reaction were passed through the water scrubber for removal of hydrogen chloride gas. The scrubber outlet was given to the caustic solution tank for converting the unreacted chlorine into sodium hypochlorite. Second lot of 12 g butyl tin mercaptide was added after one hour of FRR (Free Radical Reaction). Chlorination reaction was run for 1400 minutes and the temperature was allowed to rise from 60⁰C to 120⁰C, more precisely from 70⁰C to 110⁰C during the reaction. At the end of 1400 minutes the chlorine flow was stopped and air flow to remove the HCl/ dissolved Cl₂ was started. The air was passed for 2 hours, meanwhile the reactor temperature dropped to 50 ⁰C. At this temperature, the product was unloaded in the aeration tank and final aeration was done for 2 hr. 2 kg of epoxy soya stabilizer per 250 kg of chloroparaffin product was added, followed by 7kg butyl tin mercaptide to the product for better heat stability. Specific gravity was measured for analyzing the rate of reaction. Product quality was determined by weight loss and heat heat stability. The results of the synthetic experiments carried out under various conditions in the presence of the activity control agent are given against Expt Nos 2, 3 and 5 in table 3.

The results of the various chlorination experiments using paraffins carried out under various conditions are compared in table 3. Table 3: Comparison of reactivity and heat stability of chloroparaffins synthesized under various conditions

From table 3 it is clear that on following the method of the invention (as exemplified by experiment Nos 2, 3 and 5), there is increased rate of chlorination (as evidenced by the relatively less time required [1200 minutes and 1370 minutes as against 1400 minutes] for reaching a specific gravity of 1.2 g/cm³) and increased heat stability of the chloroparaffin product (as evidenced by the relatively less percentage weight loss[0.17 and 0.45 as against 0.33 and 0.68 respectively] when subjected to a temperature of 180⁰C for half an hour and also by the observed heat stability of. the product at 180⁰C).

The reactivity increase of paraffin chlorination reaction on following the method of the invention is further evident from Fig 1 and Fig 3. Fig 1 displays the specific gravity profile of chloroparaffin product obtained by chlorination of normal paraffin and Fig 3 displays the specific gravity profile of chloroparaffin product obtained by chlorination of raw paraffin. From Fig 1 and Fig 3 it is clear that on following the method of the invention where an activity control agent is used, chloroparaffin of desired specific gravity is obtained at lower reaction times.

Fig 2 and Fig 4 display the appearance of chloroparaffin products obtained by the chlorination of normal paraffin and raw paraffin respectively. In each of the figures, the chloroparaffin product (The liquid in the beaker marked as B and the liquid in the beaker marked as E) obtained on following the method of the invention has better clarity. Better product clarity is indicative of less contamination of the product by carbonaceous and pitchy by products, on following the method of the invention. In other words, on following the method of the invention, product selectivity and purity during paraffin chlorination are improved. Therefore,_/ the method of the invention ensures maximum yield and minimizes the requirement of cumbersome purification procedures. TECHNICAL ADVANTAGES

In accordance with the present invention, the amount of unreacted chlorine is reduced by at least 40% which was determined by the amount of calcium carbonate required to neutralize the unreacted chlorine coming from the reactor. Thus, the method in accordance with the present invention shows increase in the reactivity of the chlorine and heat stability of the chloroparraffin, which results in improvement of chloroparaffin productivity. In accordance with the present invention, the improvement in thermal stability of the chloroparaffin is beneficial in applications that require operations at higher temperatures. Moreover, in accordance with the present invention, the heat stability of the chloroparaffins reduces or even eliminates the need for the addition of expensive external stabilizing agents, thereby resulting in improvement in chloroparaffin purity and reduction in cost.

The method in accordance with the present invention allows better control of the reaction kinetics that help in reducing run away reactions and 'flashing' of the paraffins. The activity control agents used in the method in accordance with present invention are less expensive and are added only in ppm quantities to obtain the thermally stable chloroparaffins.

While considerable emphasis has been placed herein on the specific steps of the preferred method, it will be appreciated that many steps can be made and that many changes can be made in the preferred steps without departing from the principles of the invention. These and other changes in the preferred steps of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

Claims

Claims:

1. A method for synthesis of chlorinated paraffin, the method comprising reacting a C_8-24 paraffinic hydrocarbon with chlorine gas in the presence of 100 to 1500 ppm of an activity control agent at a temperature in the range of 25⁰C to 200⁰C and at a pressure in the range of 1 to 3 atmospheres.

2. The method as claimed in claim 1, wherein the hydrocarbon is preheated at a temperature in the range of 50⁰C to 80⁰C.

3. The method as claimed in any one of the claims 1 or 2, wherein the activity control agent is selected from a group consisting of an organo tin compound and mercaptides, carboxylates, sulfides and maleates of a group II and a group 14 metal.

4. The method as claimed in claim 3, wherein the group II metal is selected from calcium and barium and the group 14 metal is selected from tin and lead.

5. The method as claimed in any one of the claims 1 to 4, wherein the activity control agent is an alkyl mercaptide.

6. The method as claimed in any one of the claims 1 to 5, wherein the reaction is carried out in the presence of 500 to 800 ppm of activity control agent.

7. The method as claimed in any one of the claims 1 to 6, wherein the reaction is carried out at a temperature in the range of 60⁰C to 150⁰C.

8. A chlorinated paraffin synthesized by the method as claimed in any one of the claims 1 to 7.

9. A composition comprising the chlorinated paraffin as claimed in claim 8.