FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2006
COMPLETE SPECIFICATION
(See Section 10; rule 13)
A PROCESS FOR SEPARATING 1, 4-DICHLORO BUTENE-2
PIDILITE INDUSTRIES LIMITED
an Indian Company
of Regent Chambers, Nariman Point,
Mumbai -400021, Maharashtra, India.
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

Field of invention
The invention relates to a process for separating 1, 4-dichloro butene-2.
Background
1, 4-dichloro butene-2 is a valuable intermediate in the manufacture of chloroprene. Chloroprene is used in large quantities for the synthesis of polychloroprene, a synthetic rubber. 1, 4-dichloro butene-2 is manufactured by the chlorination of butadiene. The chlorination also results in other dichlorobutenes such as 3, 4-dichloro butene-2and heavier fractions. The various dichlorobutenes and their heavier fractions are usually separated using distillation columns. Conventionally, the distillation columns in chloroprene manufacture use Mellapack 250 as the packing. However, the extent of recovery of 1, 4-dichloro butene-2 possible during conventional separations is limited and, therefore, requires improvement.
Detailed description
Accordingly, the invention provides a process for separating 1, 4-dichloro butene-2 from a mixture of chlorinated products.
In one embodiment, the invention provides a process for separating 1, 4-dichloro butene-2 from a mixture of chlorinated products, the process comprising contacting the mixture with a column packed with a structured packing capable of providing number of theoretical stages in excess of 10.

In another embodiment, the invention provides a process for separating 1, 4-dichloro butene-2 from a mixture of chlorinated products, the process comprising contacting the mixture with a column packed with a structured packing capable of providing number of theoretical stages in excess of 10 wherein the packing agent is stainless steel, particularly Mellapack450YSS316L.
In another embodiment, the invention provides a process for separating 1, 4-dichloro butene-2 from a mixture of chlorinated products, the process comprising contacting the mixture with a column packed with a structured packing capable of providing number of theoretical stages in excess of 10 wherein the column has a diameter of around 1000 mm and a height of around 5 meters.
In another embodiment, the invention provides a process for separating 1, 4-dichloro butene-2 from a mixture of chlorinated products, the process comprising contacting the mixture with a column packed with a structured packing capable of providing number of theoretical stages in excess of 10 wherein the surface area per volume of the packing is more than 450 m2/m3.
In another embodiment, the invention provides a process for separating 1, 4-dichloro butene-2 from a mixture of chlorinated products, the process comprising contacting the mixture with a column packed with a structured packing capable of providing number of theoretical stages in excess of 10 wherein entrainment of heavy fractions at the top of the column is in the range of 5 to 10%.

In another embodiment, the invention provides a process for separating 1, 4-dichioro butene-2 from a mixture of chlorinated products, the process comprising contacting the mixture with a column packed with a structured packing capable of providing number of theoretical stages in excess of 10 wherein more than 80% of 1,4-dichlorobutene-2 is retained at the top portion of the column.
In another embodiment, the invention provides a process for separating 1, 4-dichloro butene-2 from a mixture of chlorinated products, the process comprising contacting the mixture with a column packed with a structured packing capable of providing number of theoretical stages in excess of 10 wherein the column is operated at a head pressure of 20mm Hg.
In another embodiment, the invention provides a column for separating 1, 4-dichloro butene-2 from a mixture of chlorinated products, the column comprising a structured packing agent capable of providing number of theoretical stages in excess of 10.
In another embodiment, the invention provides a column for separating 1, 4-dichloro butene-2 from a mixture of chlorinated products, the column comprising a structured packing agent capable of providing number of theoretical stages in excess of 10 wherein the structured packing agent is stainless steel, particularly Mellapack 450 Y SS 316L.
In another embodiment, the invention provides a column for separating 1, 4-dichloro butene-2 from a mixture of chlorinated products, the column comprising a structured

packing agent capable of providing number of theoretical stages in excess of 10 wherein the column is having a having a diameter of around 1000 mm and a height of around 5 meters.
In another embodiment, the invention provides a column for separating 1, 4-dichloro butene-2 from a mixture of chlorinated products, the column comprising a structured packing agent capable of providing number of theoretical stages in excess of 10 wherein the surface area per volume of the packing is more than 450 m /m .
The invention provides a process for separating 1, 4-dichlorobutene-2 from a mixture of chlorinated products. Usually, a high boiler column is used for separation, in the process of the invention. Advantageously, the high boiler column is operating at a head pressure of 20 mm Hg. Such a high vacuum is beneficial to achieve high evaporation rates of 1, 4-dichlorobutene-2 from the bottom of the column and for avoiding thermal break down of the products, in fact, a set of two distillation columns are used for separation of dichlorobutenes from heavy fractions. In the first column, 3, 4-dichlorobutene-l and 1, 4-dichlorobutene-2 are separated from the top portions leaving 35 to 55%, 1, 4-dichlorobutene-2 with heavy fractions at the bottom. In the second distillation column, 1, 4-dichlorobutene-2 is received from the top portion leaving behind 15 to 25% , 1, 4-dichlorobutene-2 along with heavy fractions. The process of the invention utilizes a distillation column packed with a structured packing. Advantageously, the column diameter is around 1000 mm and the height of the column that is packed is around 5.3 meters.

A comparison of parameters of separation of 1, 4-dichlorobutene-2 from other chlorinated products using columns having different structured packing agents is displayed in table 1.

Identified parameters Parameter values for a standard packing agent which is
250YSS316L 450YSS316L
Feed rate to
distillation
column 1300kg/hr 874 kg/hr 1300 kg/hr 874 kg/hr
Distillate rate 900 kg/hr 600 kg/hr 900 kg/hr 600 kg/hr
Rate withdraw 400 kg/hr 274 kg/hr 400 kg/hr 274 kg/hr
Composition of top stream 1,4-
dichlorobutene :
79%
Heavy fraction :
10.7%
3,4-dichloro-
butene-1: Q.S. 1,4-
dichlorobutene :
79%
Heavy fraction :
10.7%
3,4-dichloro-
butene-l:Q.S. 1,4-
dichlorobutene :
84%
Heavy fraction :
7.5%
3,4-dichIoro-
butene-l:Q.S. 1,4-
dichlorobutene :
84%
Heavy fraction :
7.5 %
3,4-dichIoro-
butene-l:Q.S.
Percentage composition of 1,4-
dichlorobutene-2 of bottom stream (%) 19.7 19.7 9.8 9.8
From Table 1, it is clear that by using Mellapack 450Y as the column packing, the proportion of 1, 4-dichlorobutene-2 in the bottom stream is reduced from 19.7% to 9.8%. Therefore, upon using Mellapack 450Y as the packing agent, there is an improvement in separation of 1, 4-dichlorobutene-2 by around 50%.

Technical Advantages:
The improved recovery of 1, 4-dichlorobutene-2 by the process of the invention enable efficient separation of dichlorobutenes with minimizing the losses of 1,4-dichlorobutene-2 which is a valuable component.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the invention. These and other changes in the preferred embodiment 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.

We Claim:
1. A process for separating 1, 4-dichloro butene-2 from a mixture of chlorinated products,
the process comprising contacting the mixture with a column packed with a structured packing agent capable of providing number of theoretical stages in excess of 10.
2. The process as claimed in claim 1 wherein the dichlorobutene is 1, 4-dichloro butene-2
3. The process as claimed in claim 1 or 2 wherein the packing used is stainless steel as
herein described.
4. The process as claimed in anyone of the claims 1 to 3 wherein the column has a
diameter of around 1000 mm and a height of around 5 meters.
5. The process as claimed in anyone of the claims 1 to 4 wherein the surface area per
volume of the packing is more than 450 m2/m3.
6. The process as claimed in anyone of the claims 1 to 5 wherein entrainment of heavy
fractions at the top of the column is in the range of 5 to 10%.
7. The process as claimed in anyone of the claims 1 to 6 wherein more than 80% of 1, 4-
dichlorobutene-2 is retained at the top portion of the column,

8. The process as claimed in anyone of the claims 1 to 6 wherein the column is operated
at a head pressure of 20mm Hg.
9. A column for separating dichlorobutenes from a mixture of chlorinated products, the column comprising a structured packing capable of providing number of theoretical stages in excess of 10.
10. The column as claimed in claim 9 wherein the structured packing is stainless steel as herein described.