Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
1997-12-12
2002-03-19
Keys, Rosalynd (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S542000, C422S129000, C528S272000
Reexamination Certificate
active
06359173
ABSTRACT:
TECHNICAL FIELD
This invention relates to methods and devices for making reaction products, and especially dibasic acids, by oxidizing a hydrocarbon under controlled conditions.
BACKGROUND ART
There is a plethora of references (both patents and literature articles) dealing with the formation of acids, one of the most important being adipic acid, by oxidation of hydrocarbons. Adipic acid is used to produce Nylon 66 fibers and resins, polyesters, polyurethanes, and miscellaneous other compounds.
There are different processes of manufacturing adipic acid. The conventional process involves a first step of oxidizing cyclohexane with oxygen to a mixture of cyclohexanone and cyclohexanol (KA mixture), and then oxidation of the KA mixture with nitric acid to adipic acid. Other processes include, among others, the “Hydroperoxide Process”, the “Boric Acid Process”, and the “Direct Synthesis Process”, which involves direct oxidation of cyclohexane to adipic acid with oxygen in the presence of solvents, catalysts, and initiators or promoters.
The Direct Synthesis Process has been given attention for a long time. However, to this date it has found little commercial success. One of the reasons is that although it looks very simple at first glance, it is extremely complex in reality. Due to this complexity, one can find strikingly conflicting results, comments, and views in different references.
It is well known that after a reaction has taken place according to the Direct Synthesis, a mixture of two liquid phases is present at ambient temperature, along with a solid phase mainly consisting of adipic acid. The two liquid phases have been called the “Polar Phase” and the “Non-Polar Phase”. However, no attention has been paid so far to the importance of the two phases, except for separating the adipic acid from the “Polar Phase” and recycling these phases to the reactor partially or totally with or without further treatment.
It is also important to note that most studies on the Direct Oxidation have been conducted in a batch mode, literally or for all practical purposes.
There is a plethora of references dealing with oxidation of organic compounds to produce acids, such as, for example, adipic acid and/or intermediate products, such as for example cyclohexanone, cyclohexanol, cyclohexylhydroperoxide, etc.
The following references, among the plethora of others, may be considered as representative of oxidation processes relative to the preparation of diacids and intermediate products.
U.S. Pat. No. 5,463,119 (Kollar), U.S. Pat. No. 5,374,767 (Drinkard et al.), U.S. Pat. No. 5,321,157 (Kollar), U.S. Pat. No. 3,987,100 (Barnette et al.), U.S. Pat. No. 3,957,876 (Rapoport et al.), U.S. Pat. No. 3,932,513 (Russell), U.S. Pat. No. 3,530,185 (Pugi), U.S. Pat. No. 3,515,751 (Oberster et al.), U.S. Pat. No. 3,361,806 (Lidov et al.), U.S. Pat. No. 3,234,271 (Barker et al.), U.S. Pat. No. 3,231,608 (Kollar), U.S. Pat. No. 3,161,603 (Leyshon et al.), U.S. Pat. No. 2,565,087 (Porter et al.), U.S. Pat. No. 2,557,282 (Hamblet et al.), U.S. Pat. No. 2,439,513 (Hamblet et al.), U.S. Pat. No. 2,223,494 (Loder et al.), U.S. Pat. No. 2,223,493 (Loder et al.), German Patent DE 44 26 132 A1 (Kysela et al.), and PCT International Publication WO 96/03365 (Constantini et al.).
None of the above references, or any other references known to the inventors disclose, suggest or imply, singly or in combination, oxidation reactions to intermediate oxidation products under conditions subject to the intricate and critical controls and requirements of the instant invention as described and claimed.
Our U.S. Pat. Nos. 5,580,531, 5,558,842, 5,502,245, as well as our PCT International Publication WO 96/40610 describe methods and apparatuses relative to controlling reactions in atomized liquids.
SUMMARY OF THE INVENTION
As aforementioned, the present invention relates to methods and devices of oxidizing a hydrocarbon, such as cyclohexane for example, to an acid, such as adipic acid for example. More particularly this invention pertains to a method of controlling in a first reaction zone the oxidation of a hydrocarbon to form an acid in the presence of a catalyst, a solvent, an optional initiator, water, and oxidation products; the hydrocarbon, the catalyst, the solvent, and at least part of the oxidation products forming at least partially a liquid mixture, the method characterized by the steps of:
(a) contacting the liquid mixture with a gaseous oxidant in the first reaction zone at a first temperature, the first temperature being adequately high for the oxidation to proceed;
(b) driving the oxidation to a steady state at a first hydrocarbon level, a first solvent level, a first catalyst level, and a first water level;
(c) controlling at least one of the first hydrocarbon level, the first solvent level, the first catalyst level, and the first water level, in a manner to cause formation of and/or maintain a single liquid phase in the first reaction zone, regardless of the presence or absence of a solid phase, and if necessary; and
(d) making phase-related adjustments to the liquid mixture, the phase-related adjustments being at least partially based on phase formation relationships, when said liquid mixture is at a second temperature, and wherein the phase related adjustments are directed toward formation and/or maintenance of a single liquid phase.
The second temperature is preferably substantially the same as the first temperature. However, it may be different than the first temperature.
The phase related adjustments to the liquid mixture in the first reaction zone may be conducted by variable selected from a group consisting of temperature in the first reaction zone, pressure in the first reaction zone, gaseous oxidant flow rate into the first reaction zone, water flow rate into the first reaction zone, water removal rate from the first reaction zone, catalyst flow rate into the first reaction zone, hydrocarbon flow rate into the first reaction zone, hydrocarbon removal rate from the first reaction zone, solvent flow rate into the first reaction zone, solvent removal rate from the first reaction zone, recycled off-gas flow rate into the first reaction zone, and a combination thereof.
It is preferable that the method comprises a step of determining, one or more of:
a maximum hydrocarbon level, a maximum water level, and a maximum catalyst level, at or over which, the single liquid phase is transformed to two liquid phases; and
a minimum solvent level, at or under which, the single liquid phase is transformed to two liquid phases;
under a set of conditions, wherein levels not being determined remain constant.
The step of determining one or more of the levels, at or over which, the single liquid phase is transformed to two liquid phases, may further comprise steps of:
obtaining a sample of a liquid mixture from the first reaction zone; and
adding to the sample, hydrocarbon, or water, or catalyst, or a combination thereof, until a second liquid is formed.
The first hydrocarbon level, the first water level, and the first catalyst level are preferably controlled to be under the maximum hydrocarbon level, the maximum water level, and the maximum catalyst level, respectively, and the first solvent level is controlled to be maintained over the minimum solvent level.
The sample may be analyzed to obtain compositional data of the sample, and therefore of the contents of the reaction zone.
The compositional data of the sample may be compared with one or more of phase diagrams, thermodynamic data bases, flow sheets, computer flow sheet simulations, catalyst precipitation data, energy balances, and experimental data, and a step of making phase related adjustments and/or catalyst precipitation adjustments may be made in order to avoid formation of a second liquid phase, and/or catalyst precipitation, respectively, in the first reaction zone, if the comparison indicates that formation of a second liquid phase and/or catalyst precipitation are being approached.
The compositional data of the sample may also be compared with one or more of the max
Aldrich Sharon M.
Dassel Mark W.
DeCoster David C.
Rostami Ader M.
Vassiliou Eustathios
RPC Inc.
Seed Intellectual Property Law Group PLLC
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