Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
1998-11-25
2001-09-11
Rotman, Alan L. (Department: 1612)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C549S516000, C549S524000, C549S525000
Reexamination Certificate
active
06288248
ABSTRACT:
The present invention relates to an epichlorohydrin-based product and to a process for manufacturing an epichlorohydrin-based product by reaction between allyl chloride and a peroxide compound in a liquid medium containing a diluent, and more particularly to an epichlorohydrin-based product which is depleted in chloro impurities and to an improved process for manufacturing this product which is depleted in chloro impurities.
It is well known to prepare epichlorohydrin by dehydrochiorination, using a basic compound, of an aqueous solution of dichloropropanols, which is obtained by reacting, in a suitable reaction zone, allyl chloride, water and chlorine, as described, for example, in patent application EP-A-1,561,441.
During this known process, unwanted by-products are generally formed, namely organochlorine products. Since these products are difficult to remove, some can be found in the epichlorohydrin. Furthermore, these by-products pose problems of disposal since they contribute towards the chemical oxygen demand and, where appropriate, to the presence of undesirable halo compounds.
The invention is directed towards overcoming the drawbacks of this known process for preparing epichlorohydrin by providing a purer product containing fewer impurities and especially fewer chloro impurities, as well as a simple process for preparing epichlorohydrin which generates fewer by-products and especially fewer chloro by-products and which exhibits high selectivity.
Consequently, the invention relates to an epichlorohydrin-based product containing at least 99.9% by weight of epichlorohydrin and a total amount of chloro impurities of less than or equal to 150 ppm by weight, in particular less than or equal to 100 ppm. This product advantageously contains an amount of methyl glycidyl ether of less than or equal to 250 ppm by weight, in particular less than or equal to 200 ppm. It preferably contains an amount of 2-methoxy-1-propanol of less than or equal to 100 ppm by weight, in particular less than or equal to 80 ppm.
The expression impurities and by-products is understood to denote products which are formed by reaction between epichlorohydrin and water or optionally the diluent and by reaction between allyl chloride and the diluent. For example, epichlorohydrin and the water or the methanol used as diluent can form, under the usual epoxidation conditions, appreciable amounts of 1-chloro-3-methoxy-2-propanol, 1-chloro-2-methoxy-3-propanol, 1,3-dichloro-2-propanol, 2,3-dichloropropanol and 1-chloro-2,3-dihydroxypropane. Moreover, the reaction between allyl chloride and the methanol used as diluent can give methyl allyl ether which, under the conditions of epoxidation with a peroxide compound such as hydrogen peroxide, can give methyl glycidyl ether. Products formed by reaction between water or the diluent and side products which may be present in the starting allyl chloride can also be found among the impurities and by-products. This is the case, for example, for 2-methoxy-1-propanol.
The invention also relates to a process for manufacturing an epichlorohydrin-based product containing at least 99.9% by weight of epichlorohydrin and a total amount of chloro impurities of less than or equal to 150 ppm by weight, in which
(a) allyl chloride is reacted with a peroxide compound in the presence of water, a catalyst and a diluent in at least one reactor, and
(b) the reaction mixture leaving step (a) is subjected to a treatment to separate out the epichlorohydrin.
The catalysts which can be used in step (a) of the process according to the invention are preferably titanium silicalite type catalysts. These are crystalline synthetic materials similar in structure to zeolites, comprising silicon oxide and titanium oxide and characterized by an infrared absorption band at about 950 -960 cm
−1
. Their general formula is typically:
xTiO
2
.(1−x)SiO
2
in which x is between 0.0001 and 0.5, preferably between 0.001 and 0.05.
The materials of this type, known as TS-1, have a microporous crystalline zeolite structure similar to that of zeolite ZSM-5. The properties and the main uses of these compounds are known (B. Notari, Structure-Activity and Selectivity Relationship in Heterogeneous Catalysis, R. K. Grasselli and A. W. Sleight Editors, Elsevier, 1991, pp. 243-56). Their synthesis has been studied in particular by A. Van der Poel and J. Van Hooff(Applied Catalysis A, 1992, Vol. 92, pp. 93-111). Other materials of this type have a structure similar to that of beta-zeolite or zeolite ZSM-11.
The catalyst are generally in amounts of greater than 2, usually greater than 5 and preferably greater than 10 g per kilo of reation mixture. These amounts generally do not exceed 200 and preferably not 100 g per kilo of reaction mixture.
The peroxide compound which can be used in step (a) of the process according to the invention can be chosen from hydrogen peroxide and any peroxide compound containing active oxygen and capable of carrying out an epoxidation. Examples which may be mentioned are the peroxide compounds obtained by oxidation of organic compounds such as ethylbenzene, isobutane and isopropanol. Hydrogen peroxide is preferred.
The peroxide compound can be used in the form of an aqueous solution or in the form of an organic solution. For economic reasons, it is generally used in the form of an aqueous solution.
When the peroxide compound is hydrogen peroxide, solutions containing at least 20% and preferably at least 30% by weight of hydrogen peroxide are particularly suitable. The solutions used can contain up to 85% by weight of hydrogen peroxide. Preferably, solutions containing less than 40% by weight of hydrogen peroxide are used. It is particularly preferred to use solutions containing about 35% by weight of hydrogen peroxide.
The process in step (a) may be performed with an allyl chloride/peroxide compound molar ratio which can vary within a wide range. The molar ratio is generally at least 0.5, in particular at least 1. The molar ratio is usually less than or equal to 10, in particular to 4.
The poor miscibility of the reagents, the allyl chloride and the aqueous solution of peroxide compound makes it necessary to use a common diluent in step (a). The diluent used in step (a) of the process according to the invention can be chosen from any organic solvent which is at least partially water-soluble. Solvents which are particularly suitable are alcohols. The preferred alcohols contain from 1 to 5 carbon atoms and comprise only one —OH group. Examples which may be mentioned are methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, s-butanol t-butanol and pentanol. Usually, the alcohol is methanol or t-butanol. Methanol is particularly preferred.
The diluent can be used in variable amounts. In general, the reaction mixture contains at least 30% by weight of diluent, usually at least 50% by weight. It commonly contains not more than 90% by weight of diluent. Preferably, it contains not more than 75% by weight of diluent.
The temperature and pressure at which step (a) is carried out can vary within very wide ranges. They are chosen so as not to exceed the decomposition temperature of the reaction mixture.
The temperature of step (a) is commonly less than 150° C. and usually between 0 and 120° C. Good results have been obtained at temperatures of between 20 and 80° C.
The pressure in step (a) can be less than, equal to or greater than atmospheric pressure. The pressure is generally less than 5 bar. Good results have been obtained using pressures of from 0.05 to 3 bar.
The duration of step (a) depends on the catalyst, the peroxide compound, the diluent and the amounts of each of the constituents used. It is chosen so as to obtain a very high to quantitative degree of conversion of the peroxide compound. It can range from 1 minute to 50 hours. Good results have been obtained with a reaction time of from 5 minutes to 2 hours.
Step (a) can be carried out in a single reactor or in a series of reactors in parallel or in series. Any type of apparatus which is suitable for liquid reaction mix
Catinat Jean-Pierre
Gilbeau Patrick
Strebelle Michel
Desai Rita
Rotman Alan L.
Schneller Marina V.
Solvay ( Societe Anonyme)
Venable
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