Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1997-01-07
1998-05-26
Geist, Gary
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C07C 3700
Patent
active
057568618
DESCRIPTION:
BRIEF SUMMARY
Disclosed herein is a method for the production of phenol and its derivatives by partial oxidation of benzene or a benzene derivative by nitrous oxide.
The production of phenol by partial oxidation of benzene using nitrous oxide over a variety of catalysts ranging from vanadium pentoxide on silica to zeolites, e.g. ZSM-5 and ZSM-11 zeolite catalysts, at elevated temperatures, e.g. 300.degree. to 450.degree. C., has been disclosed. In this reaction benzene is partially oxidized by an excess amount of nitrous oxide producing phenol and by-product nitrogen. See, for instance, Suzuki et al., 1988 Chemistry Letters of the Chemistry Society of Japan at pages 953-956. In U.S. Pat. No. 5,001,280 Gubelmann et al. discloses the advantage of oxidizing benzene with nitrous oxide at 400.degree. C. using a zeolite catalyst having a silica to alumina ratio greater than 90.
In U.S. Pat. No. 5,110,995 Kharitonov et al. disclose that changes in the molar ratio of benzene to nitrous oxide does not substantially affect the yields of phenol but declare a preference for a reaction mixture of stoichiometric composition. Although benzene derivatives can also be oxidized by nitrous oxide to provide the corresponding phenol derivative, phenol is the most important commodity chemical in the class with uses in the manufacture of phenolic resins and the synthesis of chemicals such as caprolactam and adipic acid.
The partial oxidation of benzene or a benzene derivative by nitrous oxide to phenol or a phenol derivative is highly exothermic. The liberation of significant quantities of heat, i.e. about 62 kilocalories per mole of phenol produced, leads to overheating of the catalyst resulting in lowering of reaction selectivity due to intensification of side reactions. Overheating can also diminish catalyst life.
Various approaches for avoiding overheating only make the process more complex. For instance, the reaction can be conducted in a tubular reactor with heat extracted by a circulating heat transfer fluid in an intertubular space. Alternatively, the reaction can be carried out in a fluid bed reactor equipped with internal heat exchangers. As the reaction becomes more exothermic, e.g. due to higher conversion, more complex equipment is required to remove the generated heat of reaction. For instance, in some cases the heat capacity of the reaction mixture is increased by introducing a high heat capacity component to reduce the level of adiabatic temperature increase.
Despite its simplicity, the use of high heat capacity components is rare because of requirements for such an additive component are very stringent. For example, in addition to having a high heat capacity, the component must also be inert under reaction conditions, must not poison the catalyst and must be easily separable from the reaction products. In the case of the oxidation of methanol to formaldehyde, Boreskov in Russian Pateny 804628 has suggested adding saturated hydrocarbons such as ethane and propane to the reaction mixture to absorb heat.
To avoid overheating in laboratory practice, the catalyst is usually placed in a tubular reactor of small diameter or diluted with quartz chips. The reaction is also often reported as being conducted using a small concentration of the starting materials. For instance, Burch et al. in Applied Catalysis A: General, 86 (1992)139-146, indicate that the optimal reaction mixture contains about 4 mole percent of benzene and a large excess of nitrous oxide. And, Gubelmann et al. discloses in U.S. Pat. No. 5,055,623 a reaction process using excess nitrous oxide where the reaction mixture has a molar ratio of nitrous oxide to benzene ranging from as 1 to 10. Among the drawbacks of these prior art reaction systems are overheating of the catalyst, low reactor capacity, low conversion of nitrous oxide and the generation of undesirable amounts of oxidized by-products such as hydroquinone resulting in a less than optimal selectivity towards the desired phenol product.
SUMMARY OF THE INVENTION
The present invention provides a simplified proc
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Kharitonov Alexandr Sergeevich
Panov Gennady Ivanovich
Sheveleva Galina Antolievan
Geist Gary
Monsanto Company
Pottlitz, Jr. Karl J.
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