Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2002-12-19
2004-11-09
Trinh, Ba K. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C549S523000
Reexamination Certificate
active
06815552
ABSTRACT:
The invention relates to a process for manufacturing an oxirane by reaction between an olefin and hydrogen peroxide in the presence of a catalyst and a diluent. 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 epoxidizing propylene using hydrogen peroxide in the presence of a catalyst of TS-1 type, as disclosed, for example, in patent application EP-A-0 230 949.
The hydrogen peroxide used is generally greatly freed from organic impurities. Thus, crude solutions of hydrogen peroxide (H
2
O
2
) arising from the extraction of a mixture derived from the oxidation of at least one alkylanthrahydroquinone, generally undergo one or more washing, extraction and/or distillation steps before being sold and/or used in synthetic processes. This is especially the case for the H
2
O
2
solutions used for the manufacture of oxiranes.
Patent application EP-A-0 549 013 relates to an integrated process for oxidizing organic substrates and for producing H
2
O
2
via an alkylanthraquinone (AO) process, which uses the water/alcohol mixture used during the oxidation of the organic substrate as the solvent for extracting the H
2
O
2
from the quinone shuttle. The Applicant has found that this process has several drawbacks:
the lack of flexibility of the overall process due to the interdependence of each step of the synthesis (AO and oxidation);
the limitation of the alcohol content of the water/alcohol mixtures imposed by the extraction conditions, which penalizes the degree of conversion of the H
2
O
2
during the epoxidation reaction;
the difficulties of phase separation during extraction with a water/alcohol mixture;
the passage of large amounts of methanol into the quinone shuttle, which, given the low flash point of methanol, results in an appreciable risk of explosion in the vapour phase during the step from oxidation to the synthesis of the H
2
O
2
;
a large amount of quinones extracted in the water/alcohol mixture, which penalizes the economic viability of an industrial plant; and
the pollution of the quinone shuttle by by-products of the oxidation reaction.
Moreover, the propylene used in the known epoxidation reactions is generally of relatively high purity, especially to avoid spurious oxidation reactions of the impurities, and mainly for reasons of yield and safety. Specifically, propane is the main impurity in propylene and it is reported in patent BE-A-1 001 884 that, in the presence of TS-1, hydrogen peroxide can oxidize an alkane.
In addition, in the case of propane, the oxidation product resulting therefrom is isopropanol. In the light of patent BE-A-1 001 884, a person skilled in the art would have deduced that, in a continuous process for producing propylene oxide with recycling of the organic reaction diluent (generally methanol), and/or in a continuous or batchwise process using a propane-rich source of propylene, isopropanol would accumulate in the diluent and end up being converted into acetone, which is generally difficult to separate from this diluent. In the presence of hydrogen peroxide, this acetone can form peroxides that are explosive and also insoluble in organic medium, which further increases the explosion hazard following their precipitation. This type of reasoning is applicable to any alkane oxidized in the presence of a peroxide compound and TS-1 and thus, to any source of olefin (recycled or otherwise) which is rich in alkane(s) and which would be intended for use in an epoxidation reaction.
Thus, patents U.S. Pat. Nos. 5,599,955 and 5,599,956 disclose the use of a substantially pure propylene, i.e. a propylene with a purity of at least 90% and preferably of at least 98%, the main impurity of which is propane.
Now, the various processes for synthesizing propylene (and olefins in general) generally lead to a propane content (or more generally a content of alkane(s)) which is appreciable, or even greater than that of the propylene, thus involving suitable separation and/or purification processes. Patents U.S. Pat. Nos. 5,599,955 and 5,599,956 mentioned above illustrate this problem.
In addition, various industrial processes using an olefin recycle the unconverted fraction thereof, which is conventionally enriched in alkane(s). These processes are thus also liable to require a separation of the constituents prior to this recycling. Examples of such processes are the polymerization of olefins and their epoxidation.
A subject of the present invention is a process for manufacturing an oxirane which avoids at least one of the abovementioned drawbacks, while at the same time having an increased degree of conversion and better selectivity than that obtained using a purified extract.
The invention consequently relates to a process for manufacturing an oxirane by reaction between an olefin and hydrogen peroxide in the, presence of a catalyst and an organic diluent, according to which the hydrogen peroxide is an aqueous hydrogen peroxide solution obtained by extraction, with substantially pure water, of the mixture derived from the oxidation of at least one alkylanthrahydroquinone, without subsequent washing and/or purification treatment.
Specifically, the Applicant has found, surprisingly, that the fact of using for the epoxidation reaction an H
2
O
2
solution extracted with water rather than with a water/alcohol mixture allows the degree of conversion of this H
2
O
2
to be increased. In addition, the fact of using an unpurified extract allows again in selectivity compared with the use of a purified extract.
The processes for producing hydrogen peroxide using alkylanthraquinone(s), or AO processes, are well known and are widely documented in the literature (see, for example, “Ullmann's Encyclopedia of Industrial Chemistry, Fifth Edition, 1989, Volume 3, p. 447-57”). They consist in subjecting a working solution of at least one alkylanthraquinone and/or of at least one tetrahydroalkylanthraquinone to a hydrogenation step, in a diluent, to produce one or more alkylanthrahydroquinones and/or alkyltetrahydroanthrahydroquinones. The working solution leaving the hydrogenation step is then subjected to an oxidation with oxygen, air or oxygen-enriched air to give hydrogen peroxide and to reform the alkylanthraquinones and/or alkyltetrahydroanthraquinones. The hydrogen peroxide formed is then separated from the working solution by means of an extraction step. According to the present invention, this extraction is carried out using substantially pure water. The working solution leaving the extraction step is then recycled into the hydrogenation step in order to recommence the hydrogen peroxide production cycle.
The term “alkylanthraquinones” is intended to denote, for example, 9,10-anthraquinones substituted with at least one alkyl side chain of linear or branched aliphatic type comprising at least one carbon atom. These alkyl chains usually comprise less than 9 carbon atoms and preferably less than 6 carbon atoms. Examples of such alkylanthraquinones are 2-ethylanthraquinone, 2-isopropylanthraquinone, 2-sec- and 2-tert-butylanthraquinone, 1,3-, 2,3-, 1,4- and 2,7-dimethylanthraquinone, and 2-iso- and 2-tert-amylanthraquinone, and mixtures of these quinones.
The expression “substantially pure water” is intended to denote a water containing less than 3% by weight of organic diluents, in particular of alcohol(s), preferably less than 0.1% or even less than 0.001% of these diluents. However, the extraction water may advantageously contain inorganic substances in a proportion of 0.001% by weight minimum, preferably 0.005% or even 0.01% minimum. However, the content of inorganic substances will not exceed 1% by weight, preferably 0.5%, or even 0.1%. These inorganic substances are advantageously substances which have a pH-regulating effect, such as acids and in particular strong acids such as nitric acid or phosphoric acid, or salts of such acids. These inorganic substances can also advantageously be substances which
Catinat Jean-Pierre
Strebelle Michel
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Solvay ( Societe Anonyme)
Trinh Ba K.
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