Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
1997-12-01
2002-11-26
Aulakh, Charanjit S (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C502S326000
Reexamination Certificate
active
06486367
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an improved process for the hydrogenation of maleic acid, maleic anhydride or other hydrogenatable precursor to 1,4-butanediol and tetrahydrofuran. The improvement comprises the addition of iron to the maleic acid, maleic anhydride or other hydrogenatable precursor feedstock. The addition of iron in the feedstock improves catalyst performance to reaction products with higher yields of 1,4-butanediol and minimal formation of by-products.
2. Description of the Prior Art
It is well known that tetrahydrofuran, gamma-butyrolactone and 1,4-butanediol are obtained by the catalytic hydrogenation of maleic anhydride and related compounds. Tetrahydrofuran is a useful solvent for natural and synthetic resins and is a valuable intermediate in the manufacture of a number of chemicals and plastics. Gamma-butyrolactone is an intermediate for the synthesis of butyric acid compounds, polyvinylpyrrolidone and methionine. Gamma-butyrolactone is a useful solvent for acrylate and styrene polymers and also a useful ingredient of paint removers and textile assistants. 1,4-butanediol (a.k.a. 1,4-butylene glycol) is useful as a solvent, a humectant, an intermediate for plasticizers and pharmaceuticals, a cross-linking agent for polyurethane elastomers, a precursor in the manufacture of tetrahydrofuran, and is used to make terephthalate plastics.
Numerous catalysts and processes for the hydrogenation of maleic acid, maleic anhydride or other hydrogenatable precursor to tetrahydrofuran, gamma-butyrolactone and 1,4-butanediol have been disclosed. Of specific interest in the instant invention are processes which are catalyzed by a supported noble metal catalyst. It has been taught in the art that such catalysts may also contain iron.
For example, U.S. Pat. No. 4,985,572 teaches a process for the catalytic hydrogenation of a carboxylic acid or an anhydride thereof to the corresponding alcohol and/or carboxylic acid ester using a catalyst comprising rhenium, palladium and at least one other metal capable of alloying with the palladium, all on a carbon support. The preferred metal capable of alloying with the palladium is silver but gold, copper, nickel, rhodium, tin, cobalt, aluminum, manganese, gallium, iron, chromium, and platinum also are taught. The preparation of this catalyst is characterized by the simultaneous deposition of palladium and silver on the carbon support followed by a high temperature (600° C.) heat treatment. Rhenium is then deposited on the palladium/alloying metal impregnated carbon support. The resulting catalyst is then reduced.
Additionally, WO 92/02298 discloses a hydrogenation catalyst comprising palladium and rhenium and one or more metals selected from the group consisting of rhodium, cobalt, platinum, ruthenium, iron, thulium, cerium, yttrium, neodymium, aluminum, praseodymium, holmium, hafnium, manganese, vanadium, chromium, gold, terbium, lutetium, nickel, scandium and niobium, on a support.
Generally, in the hydrogenation of maleic acid, maleic anhydride or other hydrogenatable precursor, the above discussed catalysts have the propensity to produce more tetrahydrofuran and gamma-butyrolactone than 1,4-butanediol. An object of this invention is a process which will maximize 1,4-butanediol production and minimize gamma-butyrolactone production.
SUMMARY OF THE INVENTION
The instant invention is a process for the production of 1,4-butanediol comprising catalytically hydrogenating a feedstock comprising a hydrogenatable precursor and iron in contact with a hydrogen-containing gas.
DETAILED DESCRIPTION OF THE INVENTION
Maleic acid or other hydrogenatable precursor are hydrogenated in the presence of a noble metal catalyst to 1,4-butanediol. The production and yields of 1,4-butanediol are enhanced by the addition of iron or an iron containing compound to the feed.
Reactants
In the process of the instant invention, at least one hydrogenatable precursor is reacted with a hydrogen containing gas in the presence of the catalyst. As used herein a “hydrogenatable precursor” is any carboxylic acid or anhydride thereof, carboxylic acid ester, lactone or mixture thereof which when hydrogenated produces 1,4-butanediol. Representative hydrogenatable precursors include maleic acid, maleic anhydride, fumaric acid, succinic anhydride, succinic acid, succinate esters such as the C
1
to C
8
dialkyl succinates (e.g. dimethyl succinate), maleate esters such as the C
1
to C
8
dialkyl maleates (e.g. dimethyl maleate), gamma-butyrolactone or mixtures thereof The preferred hydrogenatable precursors are maleic acid, maleic anhydride, succinic acid, succinic anhydride, fumaric acid, esters of C
4
acids, gamma butyrolactone or mixtures thereof.
The most preferred hydrogenatable precursor is maleic acid which is typically obtained by reacting n-butane or benzene in an oxygen-containing gas in the presence of a catalyst to oxidize in the vapor phase the n-butane or benzene to maleic anhydride, and then collecting the maleic anhydride by a water quench to produce maleic acid in an aqueous solution. The oxidation of n-butane or benzene is typically operated at a temperature of about 300° C. to 600° C. and a pressure of about 0.5 to 20 atmospheres (50 to 2000 kPa).
Typically, the hydrogen (H
2
) containing gas is commercially pure hydrogen with no diluent gases. However, the hydrogen containing gas in addition to hydrogen (H
2
) may also contain nitrogen (N
2
), any gaseous hydrocarbon (e.g. methane), as well as gaseous oxides of carbon, (e.g. carbon monoxide, carbon dioxide).
Catalyst
The catalyst employed in the instant invention comprises a noble metal of Group VIII of the Periodic Table selected from the group consisting of at least one of palladium, ruthenium, rhodium, osmium, iridium and platinum. These include (i) catalysts also containing at least one of rhenium, manganese or tellurium as described in UK Patent Publication No. 01551741, (ii) catalysts also containing at least one of silver and gold as described in U.S. Pat. No. 4,096,156 and (iii) catalysts also containing at least one metal capable of alloying with the noble Group VIII metal and at least one of rhenium, tungsten or molybdenum as described in U.S. Pat. No. 5,149,680. Examples of other suitable catalyst include palladium and rhenium on a carbon support as described in UK Patent Publication No. 01543232 and U.S. Pat. No. 4,659,686. These catalyst composition may also be further modified through the incorporation of a metal or metals selected from Groups IA, IIA or VIII.
The preferred catalyst employed in the instant invention comprises palladium, silver and rhenium supported on carbon. The carbons for use in this invention have a BET surface area of at least 200 m
2
/g, and preferably be in the range of 500-1500 m
2
/g. Catalysts of this type are described in U.S. Pat. No. 5,149,680.
The preferred catalyst composition comprises about 0.1 to about 20 weight percent palladium, preferably about 2 to about 8 weight percent palladium; about 0.1 to about 20 weight percent silver, preferably about 1 to about 8 weight percent silver; about 0.1 to about 20 weight percent rhenium, and preferably about 1 to about 10 weight percent rhenium. The ratio of palladium to silver is between 10 to 1 and 1 to 10. As suggested earlier, this catalyst composition may also be further modified through the incorporation of a metal or metals selected from Groups IA or IIA.
The preferred catalysts for use in this invention may be conveniently prepared by impregnation of the carbon support, either in single or multiple impregnation steps, with a solution or solutions containing at least one palladium, silver, or rhenium compound. As used herein, impregnation of the carbon support means to cause the carbon support to be filled, imbued, permeated, saturated or coated. The impregnating solution may optionally contain complexing agents to help solubilize one or more of the metal compounds. The catalyst is dried after each impregnation step to remove any carrier solvent. Drying temperatu
Attig Thomas George
Budge John Raymond
Dubbert Robert Allen
Aulakh Charanjit S
The Standard Oil Company
Yusko David P.
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