Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-08-09
2002-09-24
O'Sullivan, Peter (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C502S158000
Reexamination Certificate
active
06455742
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains generally to the field of catalytic hydrogenation, and more particularly relates to the catalytic hydrogenation of carboxylic acid groups to hydroxyl groups in hydroxycarboxylic acids.
BACKGROUND OF THE INVENTION
Dihydroxyalkanes such as ethylene glycol and 1,2-propanediol have uses in a wide variety of applications including as monomers in polyester resins; in antifreeze and deicing fluids; in the manufacture of food, drug and cosmetic products; and in liquid detergents. The demand for 1,2-propanediol has recently increased as it has become more common to substitute 1,2-propanediol for ethylene glycol in these applications.
1,2-propanediol, or propylene glycol, is currently produced by oxygenating propylene to produce the epoxide, propylene oxide. Propylene oxide is then typically reacted with water to form the desired 1,2-propanediol. Because this process begins with propylene, the price of the resulting 1,2-propanediol is linked to the change in the price of oil and other hydrocarbon non-renewable resources. There is a need for a method that produces dihydroxyalkanes from renewable resources such as plants.
It is well known that plants produce glucose from atmospheric carbon dioxide and sunlight in the process of photosynthesis. Because carbon dioxide is a greenhouse gas, any additional removal of the gas from the atmosphere helps to offset the increase in these gases by industrial emissions. It is well known that glucose may be obtained from a variety of natural sources such as corn starch, a natural product obtained from corn. Fermentation of glucose is well known to produce lactic acid, also known as &agr;-hydroxypropanoic acid or 2-hydroxypropanoic acid. In fact, the majority of lactic acid currently produced is obtained through the fermentation of glucose.
Several types of fermentation exist for converting glucose to lactic acid. For example, in homolactic fermentation, the primary fermentation product is lactic acid, and various bacteria such as
Lactobacillus delbruckii, L. bulgaricus, L. Leichmanii, L. carsei,
and
L. salivarus
can be used. Surinder, P. C.; Ullman's Encyclopedia of Ind. Chem., 5
th
Edition (1990) Vol. A15, 100. In heterolactic fermentation, on the other hand, large amounts of other fermentation products such as acetic acid, ethanol, formic acid, and carbon dioxide may be produced depending on the materials and reaction conditions used. Id.
As non-renewable resources are diminished, the prices of materials obtained from such resources will undoubtedly increase. On the other hand, as advances in fermentation and separation technologies occur, the price of products obtained from fermentation processes will decrease. Thus, the price of lactic acid derived from natural, renewable resources should decrease as these advances are made. Furthermore, as production of glucose and lactic acid increases, the price of lactic acid should drop due to increased competition and economies of scale.
Conversion of the carboxylic acid functionality on lactic acid to a hydroxyl group produces 1,2-propanediol. Thus, if an economically feasible method were found that could effect this transformation, a route would be available for producing 1,2-propanediol from a renewable resource. What is thus needed, is an economical method for reducing the carboxylic acid group on hydroxycarboxylic acids to a hydroxyl group.
It has long been known that the catalytic hydrogenation of carboxylic acids is difficult. Thus, reductions of carboxylic acids are usually accomplished through a two-step process wherein the carboxylic acid is first converted into a more readily reducible derivative such as an ester or anhydride. Although the reduction of carboxylic acids has been described, such processes normally employ high hydrogen pressures and are also normally performed in the liquid phase. A process for directly converting a hydroxycarboxylic acid to a dihydroxyalkane, particularly a process which does so at lower pressures, would greatly reduce expenses associated with such a transformation as it would eliminate the unnecessary expenses associated with transforming the carboxylic acid group to a more readily reducible group.
Various patents disclose the reduction of carboxylic acid derivatives. For example, U.S. Pat. No. 2,093,159 issued to Schmidt discloses the reduction of esters to aldehydes and alcohols using activated copper, nickel, silver, zinc, cadmium, lead, or mixtures of these metals. The activating agents disclosed include metal compounds which give acids with oxygen such as chromium, molybdenum, tungsten, uranium, manganese, vanadium, or titanium in addition to compounds of the alkali, alkaline earth and rare earth metals. The patent discloses that metal catalyst activity can be achieved by depositing the metal catalyst on finely divided substrates such as fibrous asbestos, graphite, silica gel or metal powders. The temperatures for the catalytic reduction of esters is disclosed as ranging between 200° C. and 400° C., and Ni is disclosed as having superior reduction properties over copper.
The catalytic conversion of carboxylic acid anhydrides to alcohols is disclosed in U.S. Pat. No. 2,275,152 issued to Lazier. The catalysts disclosed for use in the reduction include mixtures of difficultly reducible oxides of hydrogenation metals such as chromites or chromates and oxides of magnesium, zinc, and manganese with readily reducible oxides of hydrogenation metals such as those of silver, cadmium, copper, lead, mercury, tin bismuth, iron, cobalt, and nickel. Hydrogen pressure in the process is greater than 10 atm, and operable temperatures are those in excess of 200° C.
A process for hydrogenating esters to alcohols with a cobalt-zinc-copper catalyst at temperatures between 100° C. and 350° C. and pressures ranging from 34 to 681 atm is disclosed in U.S. Pat. No. 4,113,662 issued to Wall. The patent discloses that the cobalt-zinc-copper catalyst is a highly effective ester hydrogenation catalyst in terms of activity, selectivity and stability.
A process for effecting hydrogenolysis of esters is disclosed in GB 2,150,560 issued to Kippax et al. The disclosed process includes contacting a vaporous mixture of an ester, hydrogen, and minor amounts of carbon dioxide with a catalyst consisting essentially of a reduced mixture of copper oxide and zinc oxide at a temperature ranging from about 150° C. up to about 240° C. and at a pressure ranging from about 4.9 to 14.8 atm. The addition of carbon dioxide was found to have a profound effect upon the activity of the Cu/Zn hydrogenation catalysts.
The catalytic conversion of carboxylic acids to alcohols has generally been described as more difficult than the conversion of esters to alcohols. Thus, the pressure and temperature required to effect the reduction of carboxylic acids have generally been higher than those required for reduction of esters and other carboxylic acid derivatives.
Catalytic hydrogenation of carboxylic acids and esters is disclosed in U.S. Pat. No. 2,110,483 issued to Guyer. The addition of iron is disclosed as improving the catalytic activity of catalysts, especially copper chromite which is referred to as a particularly suitable catalyst. Metals disclosed as having useful catalytic properties include copper, chromium, nickel, uranium, cobalt, zinc, cadmium, molybdenum, tungsten, and vanadium. The process can be carried out at pressures ranging from 50 to 400 atm and at temperatures ranging from 150° C. to 400° C.
The reduction of carboxylic acids is also disclosed in U.S. Pat. No. 2,322,098 issued to Schmidt. Suitable catalysts for the catalytic reduction performed at temperatures greater than 120° C. and pressures greater than 30 atm, preferably from 100 atm to 300 atm, include copper, nickel, iron, cobalt, and silver. Activated catalysts are disclosed as obtained by depositing the catalytic substance on large surface carriers such as fibrous asbestos, graphite, silica gel, or inert metal powders.
The liquid-phase ruthenium-catalyzed reduction of carboxylic acids i
Cortright Randy D.
Dumesic James A.
Foley & Lardner
O'Sullivan Peter
Wisconsin Alumni Research Foundation
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