Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1998-11-12
2000-08-08
Trinh, Ba K.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
549326, 549508, 568864, C07D30708, C07D30733, C07C 2706, C07C 29136
Patent
active
061004103
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the production of butane-1,4-diol, .gamma.-butyrolactone and tetrahydrofuran.
Butane-1,4-diol, together with variable amounts of .gamma.-butyrolactone and tetrahydrofuran, can be produced by hydrogenolysis of diesters of maleic acid, fumaric acid and mixtures thereof. A major use of butane-1,4-diol is as a feedstock for the plastics industry, particularly for the production of polybutylene terephthalate. It is also used as an intermediate for the production of .gamma.-butyrolactone and of the important solvent, tetrahydrofuran.
The maleate and fumarate diesters used as feedstock for the production of butane-1,4-diol by such a hydrogenolysis route are conveniently prepared from maleic anhydride, which is itself produced by vapour phase oxidation of a hydrocarbon feedstock, such as benzene, mixed C.sub.4 olefins, or n-butane, in the presence of a partial oxidation catalyst. In the partial oxidation of benzene there is typically used a supported vanadium pentoxide catalyst promoted with MoO.sub.3 and possibly other promoters. The reaction temperature is from about 400.degree. C. to about 455.degree. C. and the reaction pressure is from about 1 bar to about 3 bar, while about 4 times the theoretical amount of air is used in order to stay outside the explosive limits. The contact time is about 0.1 s. When the feedstock is a mixed C.sub.4 olefin feedstock, i.e. a mixed butenes feedstock, then the partial oxidation catalyst may be vanadium pentoxide supported on alumina. Typical reaction conditions include use of a temperature of from about 425.degree. C. to about 485.degree. C. and a pressure of from about 1.70 bar to about 2.05 bar. The volume ratio of air to butenes may be about 75:1 in order to stay below explosive limits. Alternatively it is possible, according to more modern practice, to design the plant so that satisfactory safe operation can be achieved, despite the fact that the feed mixture of air and butenes is within the flammable limits. In the case of n-butane as feedstock, the catalyst is typically vanadium pentoxide and the reaction conditions include use of a temperature of from about 350.degree. C. to about 450.degree. C. and a pressure of from about 1 bar to about 3 bar. The air:n-butane volume ratio may be about 20:1, even though this may be within the flammable limits. One design of reactor for such partial oxidation reactions comprises vertical tubes surrounded by a jacket through which a molten salt is circulated in order to control the reaction temperature.
In each case a hot vaporous reaction mixture is recovered from the exit end of the reactor which comprises maleic anhydride vapour, water vapour, carbon oxides, oxygen, nitrogen, and other inert gases, besides organic impurities such as formic acid, acetic acid, acrylic acid, and unconverted hydrocarbon feedstock.
One way of recovering maleic anhydride from such a reaction mixture is to cool it to about 150.degree. C. using a steam-producing stream and then to cool it further to about 60.degree. C. by cooling it against water in order to condense part of the maleic anhydride, typically about 30% to about 60% of the maleic anhydride present. The remainder of the stream is then scrubbed with water.
Scrubbing with water or with an aqueous solution or slurry is described, for example, in U.S. Pat. No. 2,638,481. Such scrubbing results in production of a solution of maleic acid which is then dehydrated, by distilling with xylene, for example, so as to remove the water and re-form the anhydride. A disadvantage of such a procedure, however, is that an unacceptable proportion of the product remains in the vapour phase. In addition, some of the maleic acid is inevitably isomerised to fumaric acid. The byproduct fumaric acid represents a loss of valuable maleic anhydride and is difficult to recover from the process system since it tends to form crystalline masses which give rise to process problems.
Because of this isomerisation problem a variety of other anhydrous scrubbing liquids have been proposed. For example, dibut
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Hiles Andrew George
Tuck Michael William Marshall
Wood Michael Anthony
BASF - Aktiengesellschaft
Trinh Ba K.
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