Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2001-08-06
2003-07-08
Trinh, Ba K. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C549S529000
Reexamination Certificate
active
06590112
ABSTRACT:
This application is a 371 of PCT/EP99/08703 dated Nov. 11, 1999.
The invention relates to a continuous process for the manufacture of an oxirane by reaction between an olefin and a peroxide compound in the presence of a zeolite-based catalyst. The invention relates more particularly to a process for manufacturing 1,2-epoxypropane (or propylene oxide) by reaction between propylene and hydrogen peroxide.
It is known practice to manufacture propylene oxide by epoxidation of propylene using hydrogen peroxide and in the presence of a catalyst of TS-1 type, as described, for example, in patent application EP 0,230,949. This known process has the drawback of leading, under certain conditions, to poor selectivities and a deactivation of the catalyst.
Patent application EP 0,712,852 describes the use of a metal salt for this reaction, but these reaction conditions require a periodic or very frequent regeneration of the catalyst.
The invention is directed towards overcoming this drawback by providing a continuous process for manufacturing an oxirane, which exhibits high selectivity while at the same time producing only minimal deactivation of the catalyst.
The invention consequently relates to a continuous process for manufacturing an oxirane by reaction, at a temperature above 35° C. and for a period of more than 48 hours, of an olefin with a peroxide compound in the presence of a zeolite-based catalyst and in the presence of a salt, in which the catalyst undergoes no regeneration treatment and in which the rate of deactivation of the catalyst, expressed as being a percentage of the conversion of the peroxide compound lost per gram of oxirane produced per gram of zeolite determined after establishing the reaction conditions, i.e. after the consumption of 2.5 mol of peroxide function per gram of zeolite, remains less than or equal to 0.15%.
One of the essential features of the invention lies in the addition of a salt. The reason for this is that it has been found that the presence of a salt in the epoxidation reaction medium limits the side reactions which give rise to the formation of unwanted by-products. The addition of a salt thus makes it possible to increase the selectivity.
Another particular feature of the invention lies in a minimal deactivation of the catalyst after establishing the reaction conditions, i.e. after the consumption of 2.5 mol of peroxide (—OOH) function per gram of zeolite. More particularly, the rate of deactivation of the catalyst is expressed as being a percentage of conversion of the peroxide compound lost per gram of oxirane produced per gram of zeolite determined after establishing the reaction conditions, i.e. after the consumption of 2.5 mol of peroxide function per gram of zeolite. The rate of deactivation of the catalyst is less than or equal to 0.15%. Advantageously, this rate of deactivation is less than or equal to 0.1%. The rate of deactivation is preferably less than or equal to 0.05%.
Yet another essential feature of the process of the invention lies in the temperature at which the olefin reacts with the peroxide compound in the presence of the catalyst and the metal salt. The reason for this is that the Applicant has found that a temperature above 35° C. makes it possible to overcome the gradual deactivation of the catalyst and that the presence of a metal salt makes it possible to carry out the reaction at a substantially higher temperature without, however, any appreciable reduction in the reaction selectivity being observed. It is advantageous to carry out the reaction at a temperature above or equal to 40° C. and preferably above or equal to 45° C. A temperature above or equal to 50° C. is most particularly preferred. However, the reaction temperature is generally below 100° C. and preferably below 80° C.
The salt used in the process according to the invention can be a metal salt or an ammonium salt. Generally, the metal is chosen from alkali metals and alkaline-earth metals. The alkali metals most usually used are lithium, sodium, potassium and caesium. The alkaline-earth metals which can be used in the context of the present invention are mainly magnesium, calcium, strontium and barium.
The metal salts used are mainly halides, oxides, hydroxides, carbonates, sulphates, phosphates and organic acid salts such as acetates. The halides are generally fluorides, chlorides, bromides and iodides. A preference is shown for chlorides.
The salt used in the process according to the present invention is preferably an alkali metal halide and advantageously sodium chloride.
The amount of metal salt used in the present process is expressed as the content of ammonium or metal ions from the salt relative to the amount of catalyst expressed in millimol (mmol) of metal or of ammonium per gram of zeolite. Generally, the salt is introduced such that its content in the reaction medium is greater than or equal to 10
−4
mmol/g of zeolite and less than or equal to 10 mmol/g of zeolite. Advantageously, the metal salt content is greater than or equal to 10
−3
mmol/g of zeolite and less than or equal to 1 mmol/g of zeolite. A preference is shown for a content of greater than or equal to 10
−2
mmol/g of zeolite and less than or equal to 0.5 mmol/g of zeolite.
The catalysts used in the process according to the invention contain a zeolite, i.e. a solid containing silica which has a microporous crystalline structure. The zeolite is advantageously free of aluminium. It preferably contains titanium.
The zeolite which can be used in the process according to the invention can have a crystal structure of ZSM-5, ZSM-11 or MCM-41 type or of beta-zeolite type. Zeolites of ZSM-5 type are suitable for use. Those with an infrared adsorption band at about 950-960 cm
−1
are preferred.
The zeolites which are particularly suitable are titanium silicalites. Those corresponding to the formula xTiO
2
(1−x)SiO
2
in which x is from 0.0001 to 0.5, preferably from 0.001 to 0.05, give high-quality performance. Materials of this type, known under the name TS-1 and having a crystal structure of ZSM-5 type, give particularly favourable results.
Advantageously, the catalyst is in the form of spherical particles obtained by dispersing a sol containing zeolite crystals with a compound capable of forming a gel in the zone of a reactor containing a reaction gas such that the sol becomes fragmented into grains of sol at the reaction zone inlet. The grains of sol flow in the reaction zone along a curvilinear trajectory and, in doing so, the grains of sol solidify to a gel and can be collected.
The catalyst particles generally have an average diameter of greater than or equal to 0.01 mm and less than or equal to 5 mm, a specific surface of greater than or equal to 1 m
2
/g and less than or equal to 900 m
2
/g (determined according to the nitrogen adsorption method), an apparent density of between 0.1 and 1.0 g/ml, a pore volume of between 0.25 and 2.5 ml/g and a pore diameter distribution with a maximum of between 15 and 2000 Å.
In one particular embodiment of the process according to the invention, the reaction is carried out continuously in a reactor in the liquid phase in the presence of a solvent, and a gaseous compound is introduced continuously into the reactor at a flow rate which is sufficient to entrain some of the oxirane produced, which is collected with the gaseous compound at the place at which this gaseous compound leaves the reactor. This specific embodiment can be advantageous since it has been observed that the oxirane reacts in the epoxidation reaction medium with the water which accompanies the peroxide compound and/or the solvent to form by-products, thereby reducing the selectivity of the epoxidation reaction. By introducing a gaseous compound into the reaction medium at a flow rate which is sufficient to entrain the oxirane produced and remove it from the reactor at the same time as the gaseous compound, the contact time between the oxirane produced and the epoxidation reaction medium is reduced. This thus avoids the formation of by-products
Catinat Jean-Pierre
Strebelle Michel
Solvay ( Societe Anonyme)
Trinh Ba K.
LandOfFree
Method for making an oxirane does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for making an oxirane, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for making an oxirane will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3026445