Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2003-06-03
2004-11-23
Trinh, Ba K. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C549S523000, C423S584000
Reexamination Certificate
active
06822103
ABSTRACT:
FIELD OF THE INVENTION
The invention refers to on integrated process for selective oxidation of organic compounds, in liquid phase, which comprises a first step for direct synthesis of a non acidic hydrogen peroxide solution and a second step for oxidation an organic substrate with the reaction mixture of the first step.
STATE OF THE ART
Selective oxidation reactions are a major class of chemical transformations which account for the production of a wide variety of important chemical products, including alcohols, carbonyl compounds, epoxides, hydroxylates, acids, glycols and glycol ethers, lactones, oximes, and oxygenated sulfur and nitrogen compounds such as sulfoxides, sulfones, nitrones, azo compounds, and other N-oxides. Performing these chemical transformations efficiently, economically, and safely requires a suitable oxidizing agent which can be purchased or produced to react with the desired organic chemical feedstock, which is then converted to the oxidized organic chemical product.
Several significant problems face conventional oxidation processes. Some industrial processes use gas containing oxygen such as air or pure oxygen. But using oxygen combined with organic chemical feedstocks may accidentally achieve gas compositions in the explosive range, thereby posing a serious safety hazard. Such oxidation processes can also be prone to forming explosive gas mixtures. Oxidative processes using oxygen or air also tend to suffer from product selectivity problems related to over-oxidation of the organic chemical feedstock, normally producing undesired carbon oxides (CO, CO
2
)
An attractive alternative to using oxygen or air as the oxidation agent is the use of organic hydroperoxides as oxidizing agents. These hydroperoxide compounds, typically generated by oxidation of suitable intermediates with air or O
2,
are reacted with chemical feedstocks to form oxygenated products and organic by-products. The most common processes for producing propylene oxide (PO) use tert-butyl hydroperoxide and ethylbenzene hydroperoxide as hydroperoxides. These processes cause the formation of a higher quantity of co-products of commercial interest with respect to PO. For example, the process via tert-butyl hydroperoxide co-produces 2.5-3.5 kg of tert-butyl alcohol per kg of PO, whereas via ethylbenzene hydroperoxide co-produces 2.2-2.5 kg of styrene per kg of PO. The presence of these co-products can be of little advantage if the request for PO and the respective co-products is not suitably balanced. For example, when the demand for styrene, or methyl tert-butyl ether (MTBE) which could be obtained from tert-butyl alcohol, is high, the economics of this process are competitive; otherwise these processes are not economic.
Instead of using organic peroxides, hydrogen peroxide is a known desirable oxidizing agent. The byproduct of oxidation reactions using hydrogen peroxide is typically water, a safe compound that can be easily recovered and reused or disposed. The amount of water on a weight basis is much less than the amount of organic by-product when organic hydroperoxides are used, and thereby represents significant savings in process costs. However, past attempts to develop selective chemical oxidation processes based on hydrogen peroxide have encountered significant difficulties. Conventional hydrogen peroxide production utilizes the anthraquinone process, wherein the anthraquinone is first hydrogenated to anthrahydroquinone and then autoxidized to release hydrogen peroxide and the anthraquinone for recycle. Hydrogen peroxide is generated at low concentrations in the solution, and very large flows of anthraquinone and anthrahydroquinone must be handled in order to produce the desired hydrogen peroxide product. Accordingly, such conventionally produced hydrogen peroxide is generally too expensive for commercial use as an oxidizing agent for selective chemical oxidation processes.
A second method for the production of hydrogen peroxide comprises the use of secondary alcohols such as isopropanol and methylbenzylalcohol (U.S. Pat. No. 2,871,102, EP 378388, EP 1074548) or high-boiling secondary alcohols such as diaryl methanol (U.S. Pat. No. 4,303,632) with oxygen. These known processes, however, substantially suffer from disadvantages deriving from the necessity of operating at high reaction temperatures (generally ranging from 100 to 180° C.), the partial oxidation of the ketone which is formed as main co-product, the necessity of using a hydrogen peroxide stabilizer (orthophosphoric acid or sodium pyrophosphate). Furthermore, these processes are complicated by the necessity of separating and recovering the cetone and by products from the reaction mixture after using the hydrogen peroxide solution in a subsequent epoxidation process.
An important alternative is generating hydrogen peroxide directly by the catalytic reaction of hydrogen and oxygen, which avoids the difficulty of accompanying large flows of a working solution and can reduce the cost of hydrogen peroxide. These processes generally use a catalytic system consisting of a noble metal, particularly metals of the platinum group or their mixtures, in the form of salts or as supported metals, by reacting the two gases in a solvent consisting of an aqueous medium or an aqueous organic medium. The prior art includes a number of catalytic technologies which directly convert hydrogen and oxygen to hydrogen peroxide, but generally utilize a hydrogen/oxygen feed wherein the hydrogen concentration is greater than about 10 mol % (U.S. Pat. Nos. 4,681,751, 4,772,458, 4,832,938, 5,338,531), which is well above the flammability limit of 4.5 mol % for such mixtures and creates a serious process hazard. At hydrogen feed concentrations below 4.5 mol %, the prior art catalysts are not sufficiently active and selective to generate hydrogen peroxide product at a reasonable rate (WO 99/41190, WO 01/05498 WO 01/05501, U.S. Pat. No. 6,168,775 B1). The prior art technologies need the use in the reaction medium of high concentrations of promoters, for example acid promoters, halogenated products and/or other additives. This makes it necessary to add stabilizers, with onerous purification operations of the H
2
O
2
solution before its use in the oxidation reactions.
Various oxidation processes for organic chemical feedstocks utilizing hydrogen peroxide are known. For example, U.S. Pat. No. 4,701,428 discloses hydroxylation of aromatic compounds and epoxidation of olefins such as propylene with H2O2 using a titanium silicalite catalyst. Also, U.S. Pat. Nos. 4,824,976; 4,937,216; 5,166,372; 5,214,168; 5,912,367, WO 94/238234 and WO 99/48884 all disclose epoxidation of various olefins including propylene using titanium compounds catalysts.
EP 978316 describes a process for catalytic oxidation of an organic compound selected from olefins, aromatic hydrocarbons, ammonia and carbonyl compounds, including a first step for direct synthesis of hydrogen peroxide using a metal of group VIII supported on activated carbon functionalized with sulfonic acids, and a second step for oxidation of said organic compound substrate with the reaction mixture from the first step containing hydrogen peroxide to obtain the desired oxidized product. When the olefin is propylene, the best overall yield of propylene oxide, based on hydrogen feed, that can be achieved is 83%. However, higher yields of oxidized organic compounds are much desired.
U.S. 2001/0016187 describes a process for selective oxidation of organic chemical feedstocks utilizing directly produced hydrogen peroxide intermediate oxidant, including a first step for direct synthesis of hydrogen peroxide using a supported phase-controlled noble metal catalyst, namely a Pd/carbon black catalyst, in a solvent, in the presence of acid promoters and/or stabilizers, such as sulfuric acid, and a second step for oxidation of said organic compound substrate with the reaction mixture from the first step containing hydrogen peroxide to obtain the desired oxidized product. No data concerning oxidation of any organic chemical feedstock
Brieva Gema Blanco
Campos Martin Jose Miguel
De Frutos Escrig Pilar
Fierro Jose Luis Garcia
Garcia Jose Manuel Riesco
Ladas & Parry LLP
Repsol Quimica S.A.
Trinh Ba K.
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