Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-11-16
2001-09-11
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S350000, C568S351000, C568S387000, C568S393000, C568S396000, C568S401000
Reexamination Certificate
active
06288281
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for the carbonylation of a saturated hydrocarbon to give an oxygenated saturated hydrocarbon. The process involves using an acidic ionic liquid catalyst such as a mixture of aluminum chloride and quaternary nitrogen-containing salts to catalyze the carbon monoxide addition to the saturated hydrocarbon at reaction conditions to form oxygenates.
BACKGROUND OF THE INVENTION
Liquid superacids, e.g., HF/BF
3
, are use to catalyze reactions such as the alkylation of paraffins and the carbonylation of aliphatic hydrocarbons, see, WO 98/50336. However, the use of liquid super acids such as HF/BF
3
are not environmentally friendly and thus their replacement has received considerable attention. In the search for such replacement a family of compounds, known as ionic liquids, is receiving attention because they can act as both catalysts and solvents and have no measurable vapor pressure.
Ionic liquids are sometimes referred to as molten salts, but they are not molten salts in the sense of molten sodium chloride. Ionic liquids have melting points below room temperature and have liquid ranges of as much as 300° C. compared to the 100° C. liquid range for water. One example is 1-ethyl-3-methylimidazolium chloride-aluminum chloride, which is abbreviated as (emim)Cl—AlCl
3
. This ionic liquid is liquid from about −100° C. to about 200° C. depending on the amount of (emim)Cl and AlCl
3
. When the molar percentage of AlCl
3
is 65%, the melting point is −96° C.
The cation in the ionic liquid is an organic cation such as (emim)
+
while the anions are inorganic anions such as the anions of AlCl
3
(AlCl
4
−
, Cl
−
, Al
2
Cl
7
−
). The organic cations account for the low melting points, while the chemical properties are determined mostly by the anions. Finally, depending on the relative amounts of the inorganic anions, the ionic liquid can be basic, neutral or acidic. A review of ionic liquids can be found in Chemical and Engineering News, Mar. 30, 1998, pp. 32-37 and K. R. Seddon, “Ionic Liquids for Clean Technology: An Update,” Molten Salt Forum Vols. 5-6 (1998) pp. 53-62, Trans Tech Publications, Switzerland.
WO 95/21806 discloses the alkylation of aromatics by an olefin using an ionic liquid as the catalyst. Specifically, the alkylation of benzene with ethylene using a (emim)Cl—AlCl
3
ionic liquid catalyst with 67 wt. % AlCl
3
and 33 wt. % (emim)Cl. U.S. Pat. No. 4,554,383 discloses a process to prepare p-tolualdehyde by reacting toluene and CO in the presence of a “melt” catalyst composed of a N-alkyl-pyridinium halide and aluminum chloride. WO 00/15594 discloses reacting an alkyl aromatic compound with CO in the presence of an acidic ionic liquid to form an alkyl aromatic aldehyde.
Although the carbonylation of aromatics (or olefins) is fairly facile, the carbonylation of saturated hydrocarbons is extremely difficult. The fundamental problem in the direct carbonylation of saturated hydrocarbons is the high stability of the C—C and C—H bonds. In view of the high stability of these bonds, attempts to directly convert saturated hydrocarbons to hetero organic molecules have met with few successes. For example U.S. Pat. No. 2,874,186 discloses a process for reacting carbon monoxide with normal paraffins, isoparaffins and naphthenes to produce ketones, acids and esters. The process involves placing the isoparaffin in a reactor with hydrogen fluoride and boron trifluoride (HF/BF
3
) and carbon monoxide under high pressures. The products, which were obtained from this process, were ketones and carboxylic acids. U.S. Pat. No. 2,346,701 discloses preparing organic oxygen-containing compounds such as ketones and acids by reacting propane with carbon monoxide using an anhydrous aluminum halide catalyst, e.g., aluminum chloride. U.S. Pat. No. 3,356,720 discloses preparing oxygenated organic compounds by reacting saturated hydrocarbons with carbon monoxide using a Freidel-Crafts catalyst and a tertiary alkyl, phenyl alkyl or phenyl carbonyl halide. Both ketones and carboxylic acids are produced. It is also disclosed in WO 98/50336 that branched aliphatic hydrocarbons can be converted to branched aliphatic ketones by reacting the hydrocarbons with carbon monoxide at high pressures and super acidic conditions. The super acidic conditions are produced by the combination of a protic acid such as HF and a Lewis acid such as BF
3
. The reaction is carried out at temperatures of about 0° C. to about 35° C. and pressures of about 10 to 200 atmospheres.
All of the above references disclose the use of superacids, for carbonylation, which are corrosive, volatile and environmentally harmful. In the pursuit of an environmentally green process for the carbonylation of saturated hydrocarbons, applicants have developed a process using ionic liquids. The process involves reacting the hydrocarbon with carbon monoxide in the presence of an acidic ionic liquid to produce an oxygenated saturated hydrocarbon. The ionic liquid serves both as the catalyst and the solvent. One example of an ionic liquid is AlCl
3
(n-butylpyridinium chloride) with a ratio of AlCl
3
:(n-butylpyridinium chloride) of 64:36 by weight.
SUMMARY OF THE INVENTION
As stated, this invention relates to a process for preparing an oxygenated saturated hydrocarbon comprising contacting a saturated hydrocarbon with carbon monoxide and an acidic ionic liquid catalyst at reaction conditions to provide an oxygenated saturated hydrocarbon.
Another embodiment of the invention involves hydrogenating the oxygenated saturated hydrocarbon to give a reduced oxygenated saturated hydrocarbon.
In a specific embodiment isobutane is reacted with CO in the presence of AlCl
3
(n-butylpyridinium) ionic liquid to give methyl isopropyl ketone.
These and other objects and embodiments will become clearer after a detailed description of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Generally, the present invention relates to the direct carbonylation of saturated hydrocarbons to form the corresponding oxygenated saturated hydrocarbons. By oxygenate is meant an oxygen containing saturated hydrocarbon, with saturated referring to the hydrocarbon portion of the molecule. Non-limiting examples of these oxygenates are ketones, aldehydes and acids. Without wishing to be bound by any particular theory, the reaction pathway by which direct carbonylation to ketones takes place involves the formation of a carbocation species, i.e., a carbenium or carbonium ion which is then reacted, i.e., intercepted, by carbon monoxide molecules forming a relatively stable oxycarbocation. The oxycarbocation undergoes further molecular rearrangement involving an intramolecular hydrogen transfer, i.e., hydride shift, to produce an aldehyde, and an intramolecular methyl shift to convert the aldehyde to the more stable ketone.
Accordingly, those saturated hydrocarbon compounds, which can be used in the present invention, are any of those that can form a carbocation at reaction conditions. The hydrocarbons, which meet these criteria, are any of those which contain at least one of a primary, secondary or tertiary carbon as described in standard organic chemistry texts. Preferred hydrocarbons are those which contain one or more tertiary carbon. For the purpose of this invention, the hydrocarbons which meet these criteria are the saturated hydrocarbons which include alkanes and cyclic alkanes. Although the number of carbon atoms which the saturated hydrocarbons can have is not a critical aspect of this invention, for practical purposes those having 1 to 30 carbon atoms are usually used and thus are preferred.
Included in the general category of alkanes are cyclic alkanes, straight chain alkanes, single and multiple branched alkanes. Cyclic alkanes include cyclic alkanes having one or more alkyl groups attached to the ring. Especially preferred alkanes are the branched alkanes (branched such that they contain one or more tertiary carbon) having from 4 to about 30 carbon atoms. Specific examples of branched alkanes
Bricker Jeffery C.
Holmgren Jennifer S.
Monson Lyle E.
Nemeth Laszlo T.
Molinaro Frank S.
Padmanabhan Sreeni
Tolomei John G.
UOP LLC
Witherspoon Sikarl A.
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