|Title of Invention||
AN IMPROVED PROCESS FOR THE MANUFACTURE OF EPOXIDES PARTICULARLY EPICHLOROHYDRIN
|Abstract||A process for preparing epichlorohydrin comprising the following steps : (a) reacting allyl chloride with an inorganic peroxide compound in the presence of at least one solvent at a temperature of about 30 to 60 degree C in a fixed bed column reactor containing a catalyst to obtain a resultant containing a mixture of epichlorohydrin, unreacted allyl chloride, solvent and water; (b) diluting the mixture with water, wherein the mass ratio of water to the mixture is about 0.2 to 0.7, to obtain a diluted mixture; (c) cooling the diluted mixture to about 5-15 degree C to obtain a cooled diluted mixture; (d) separating organic phase and aqueous phase from the cooled diluted mixture; (e) separating and recovering unreacted allyl chloride and epiochlorohydrin individually from the organic phase by fractional distillation; and (f) separating and recovering solvent and water individually from the aqueous phase by fractional distillation.|
|Full Text||FORM - 2
THE PATENTS ACT, 1970
(39 of 1970)
THE PATENTS RULES, 2003
(See section 10 and rule 13)
AN IMPROVED PROCESS FOR THE MANUFACTURE OF EPOXIDES, PARTICULARLY EPICHLOROHYDRIN
ADITYA BIRLA CHEMICALS (THAILAND) LTD.
a Thailand Company
of 888/167, 16th floor, Mahatun Plaza Building, Ploenchit Road,
Limpini, Bangkok 10330, Thailand
THE FOLLOWING SPECIFICATION DESCRIBES THE INVENTION.
Field of Invention :
The present invention relates to an improved process for the manufacture of epoxides.
Particularly, this invention relates to the manufacture of epichlorohydrin by catalytic epoxidation of allyl chloride using aqueous hydrogen peroxide in presence of alcoholic solvents such as methanol, glycerol, glycol and alike.
Background and Prior Art:
Conventional manufacturing processes for epichlorohydrin described in the prior art also use methanol as a solvent but suffer from several drawbacks such as difficulties in product separation.
Typically, the reaction mass in such processes contains multiple binary hetero azeotropes, which do not allow easy separation of the product epichlorohydrin and the reactant allyl chloride from the reaction crude. Other prior art processes such as those described in the US Patent No. 6,288,248 and 6,350,888 have attempted to overcome these product separation difficulties by using liquid-liquid extraction using chlorinated hydrocarbon solvents such as dichlorobenzene. However, the separation of product epichlorhydrin from unreacted allyl chloride and impurities such as methyl glycidyl ether still remains key problem. Apart from this, the effluent treatment for removal of chlorinated solvents and products poses serious economic and environmental problems. The authors of the present invention have therefore comprehensively investigated the possibility of improved
manufacturing process for epichlorohydrin that obviates the above mentioned problems.
In one aspect of this invention, there is provided a catalytic process for the manufacture of l,2-epoxy-3-chloropropane of high purity, by reacting allyl chloride with an inorganic peroxide compound, such as hydrogen peroxide, in a presence of a solvent, such as methanol.
Accordingly, allyl chloride (ALC) is reacted in a jacketed tubular reactor with aqueous hydrogen peroxide solution in the presence of methanol having a catalyst bed.
The reaction takes place at temperature between 30 and 55 degrees C. The aqueous solution of hydrogen peroxide is immiscible with allyl chloride. Use of methanol as a solvent makes the system homogenous and facilitates the reaction.
Typically, one mole of hydrogen peroxide is used for 8 to 9 moles of ALC. Under the reaction conditions, more than 96% and preferably more than 98% of the hydrogen peroxide is converted.
The effluent stream from the reactor containing epichlorohydrin, unreacted allyl chloride and methanol is contacted with process water at temperatures in the range of 6 to 8 degrees Celsius and then transferred into the extractor.
Alternatively, the effluent stream from the reactor together with the added process water may be stored in a holding tank before taking into the extractor. The process water may be used as such or may have added constituents like common salt, surfactants, surface tension enhancing agents, and polarity increasing agents, which essentially assist in decreasing the solubility of the organics in the water.
From the extractor the reactor effluent is led to an extractor settler where the organic and aqueous phase separation takes place at temperatures between 0 to 5 degrees Celsius.
The typical ratio of mass flow rates of the process water stream to reactor effluent stream to the extractor is in the range of 0.2 to 0.7.
The organic and the aqueous phase are separated by phase split decanting and lead to stripping columns separately.
The aqueous phase contains traces of ALC and methanol, which are removed at temperatures of around 64 to 67 degrees Celsius in a stripping column and returned to the feed to the tubular reactor.
The water substantially free from ALC and methanol is lead to a separator for removing epichlorohydrin and then for disposal.
The organic phase contains epichlorohydrin of purity close to 99%. The traces of allyl chloride contaminating the organic phase are separated in
another stripping column at a temperature in the range of 41 to 45 degrees Celsius.
The present invention differs from the prior art in that,
a) a simple but intricate train of distillation sequence is proposed,
b) does not need fresh addition of any chlorinated solvent, and
c) a well designed extractor permits liquid-liquid phase split in spite of certain process disturbances and allows clean separation of epichlorohydrin and water, not restricted to the solubility, etc.
The unreacted allyl chloride is re-fed into the reactor system along with the fresh streams of allyl chloride and methanol whereas highly purified epichlorohydrin is removed from the reaction system.
Brief Description of the Accompanying Drawings:
The invention will now be described with reference to the accompanying schematic drawing (Figure 1), which discloses a process flow diagram of a typical embodiment of a process in accordance with this invention.
Figure 2 displays a detailed presentation of apparatus used for the preparation of epichlorohydrin and Figure 3 is schematic representation of siphon separator (SS.)
As shown in Figure 1, the catalytic oxidation of allyl chloride takes place in a tubular reactor (TR) containing a packed catalyst, enclosed in a jacket (J).
The reactants i.e. allyl chloride (ALC), methanol (MeOH) and hydrogen peroxide (H202) are added into the reactor using inlet stream (In).
After the completion of reaction, the effluent from the reactor containing epichlorohydrin (ECH), unreacted allyl chloride, methanol and water is transferred to a holding tank (HT) using the outlet stream (Ou). The effluent stream (W1) from the holding tank is then mixed with process water (W2) and then fed to the extraction chamber (Ex-1). The mass flow rate of W1/W2 is maintained in the range of 0.2 to 0.7.
The extraction chamber (EX-1) typically consists of three separate units: the mixer (MX), cold extractor (ER) and Decant settler (DS) as shown in Figure 2.
The mixer MX is a preferred embodiment for proper mixing of two streams. The mixer MX comprises glass beads wherein streams from W1 and W2 are thoroughly mixed before flowing downstream to the cold extractor ER.
The cold extractor (ER) is a coiled tube reactor in which the reactor effluent and the process water is led through the coil and coolant is circulated around it to bring down the temperature of the mixture in the coil to 4 to 6 degrees Celsius.
The residence time of the mixture in the extractor ranges between 45 to 150 minutes. From the cold extractor the mixture of the reactor effluent and the process water is led to the decanter settler (DS) placed below the distillation column cold extractor (ER) in the extraction chamber Ex-1, where the
temperature of the mixture is further reduced to 0 to 5 degrees Celsius. Phase separation takes place by difference in densities of the two phases, in which the organic phase settles to the bottom and is extracted through the outlet of the decanter settler (DS) through outlet (Oo). The resident time of the split phase content and the levels of the two phases are carefully controlled. The aqueous phase is let off from the outlet (Aqo) of the decanter settler (DS). The aqueous phase typically consists of mainly water and methanol with some quantities of epichlorohydrin and unreacted allyl chloride. The organic phase typically consists of epichlorohydrin and unreacted allyl chloride. The organic phase is led to column (Dl) where the epichlorohydrin of high purity is collected and the separated allyl chloride is led to the reactor input stream (In).
The aqueous stream is led to column (D2) where essentially, vapours of methanol and allyl chloride are removed and sent back to the feed line of the tubular reactor (In). The water with some quantity of epichlorohydrin is collected for removal of epichlorohydrin in a separator (SS)and is further separated by different separation techniques such as membrane separation, separation using ion exchange resins or molecular sieves or be reverse osmosis.
Alternatively, a siphon separator, as shown in Figure 3, can also be used for the separation of organic layer. The water free of any traces of epichlorohydrin after this separation operation is sent back to the water tank WT.
If instead of methanol, Bis phenol A solvent is used for homogenization, it may be advantageous to retain the solvent, as it may be required in the further processes utilizing ECH.
While considerable emphasis has been placed herein on the steps and reactant chemical compounds of the preferred embodiments, it will be appreciated that many permutations and combinations of the process steps and the composition can be made and that many changes can be made in the preferred scheme without departing from the principles of the invention. These and other changes in the preferred process steps as well as other steps of the process 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.
Dated this 18th day of September, 2006.
|Indian Patent Application Number||1479/MUM/2006|
|PG Journal Number||40/2010|
|Date of Filing||18-Sep-2006|
|Name of Patentee||ADITYA BIRLA CHEMICALS (THAILAND) LTD.,|
|Applicant Address||888/167, 16TH FLOOR, MAHATUN PLAZA BUILDING, PLOENCHIT ROAD, LIMPINI, BANGKOK 10330,|
|PCT International Classification Number||B01J27/00|
|PCT International Application Number||N/A|
|PCT International Filing date|