Method of making hydrogenated acids

Details Method of making hydrogenated acids Method of making hydrogenated acids

1999-06-10

2001-05-15

Carr, Deborah D. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Fatty compounds having an acid moiety which contains the...

C554S141000

Reexamination Certificate

active

06232480

ABSTRACT:

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
Mixtures of saturated and unsaturated carboxylic acids are conveniently converted to products substantially free of unsaturation by means of catalytic hydrogenation. Such a process is particularly useful in the commercial production of fatty acids, compounds which are used to make base stocks for soap production, as intermediate raw materials for producing a wide range of surfactants, as foam control agents and precipitants in a variety of cleaning products, as superfatting agents in personal cleansing bars, as softener components, and for a number of other more specialized purposes. Fatty acids are obtained from fats and oils by a process the first step of which is referred to as splitting. Splitting is the hydrolysis of a fat or oil to form three molecules of fatty acid and one molecule of glycerine. The glycerine is separated and refined in a separate operation. The crude split fatty acids are usually then distilled to remove color bodies and odoriferous materials. This sequence of splitting and distilling yields the most basic tallow and coconut fatty acids which are widely used for preparing bar soaps. This basic type of coconut fatty acids also finds use in the preparation of a variety of types of surfactants. While these simple split and distilled tallow and coconut fatty acids do have wide use, many in the soap and detergents industry prefer materials with improved colors, color stabilities and odors. These improvements are often effected by hydrogenation.
In the case of tallow the hydrogenation is a partial hydrogenation. It is generally controlled so as to reduce or totally eliminate the polyunsaturated acids, which are inevitably present in split tallows. Reducing or eliminating the polyunsaturates can significantly improve the color stability of the fatty acids and many soap producers find that this carries through to improving the storage properties of their soap bars. The hydrogenation process also improves the initial color and odor of the partially hydrogenated fatty acids and this also is generally found to carry through to bar soaps. The typical catalyst used for hydrogenation is some type of nickel catalyst and it is a nonselective catalyst. That means that besides reducing polyunsaturated acids to monounsaturated acids—basically oleic acids—it also reduces some amount of unsaturated acid to saturated acid—basically stearic acid. During the hydrogenation step, oxygenated compounds such as alcohols, acids and lactones may be formed which can have a deleterious effect on products and/or processes utilizing such acids. For example, the presence of alcoholic impurities could interfere with the production of acid chlorides. It is therefore desirable to produce a hydrogenated carboxylic acid that does not contain the oxygenated compounds.
BRIEF SUMMARY OF THE INVENTION
Hydrogenated carboxylic acids are made by a process which comprises contacting a mixture of saturated and unsaturated carboxylic acids with a catalyst effective amount of a hydrogenation catalyst and in the presence of an effective amount of an adsorbent to produce a hydrogenated product having less than about 200 ppm of oxygenated by-products and an iodine value of less than about 10. The process may also be carried out by first contacting a mixture of saturated and unsaturated carboxylic acids with a catalyst effective amount of a hydrogenation catalyst to form a hydrogenated product containing oxygenated by-products and then contacting the hydrogenated product with an effective amount of an adsorbent to produce a hydrogenated product having less than about 200 ppm of oxygenated by-products and an iodine value of less than about 10.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
Not Applicable.
DETAILED DESCRIPTION OF THE INVENTION
The process according to the invention can be applied to the production of any carboxylic acid made by the hydrogenation of a mixture of saturated and unsaturated carboxylic acids. The simplest example is the production of hydrogenated propionic acid having less than about 200 ppm of oxygenated compounds and an iodine value of less than about 10, by the hydrogenation of a mixture of acrylic and propionic acids (propenoic and propanoic acids). The process according to the invention is particularly useful for the commercial production of hydrogenated fatty acids, such as stearic acid, wherein the presence of oxygenated compounds could have a deleterious effect on products and/or processes utilizing such acids. Hydrogenated stearic acid can be made by fully hydrogenating mixtures of saturated and unsaturated tallow fatty acids. Hydrogenation converts these mixtures which contain C
18
unsaturated acids to stearic acid. During the hydrogenation step, oxygenated compounds such as alcohols, acids and lactones may be formed. The reduction step is typically carried out by contacting the acid mixture with hydrogen in the presence of a catalyst. The typical catalyst used for hydrogenation is some type of nickel catalyst and it is a nonselective catalyst. That means that besides reducing polyunsaturated acids to monounsaturated acids—basically oleic acids—it also reduces some amount of unsaturated acid to saturated acid—basically stearic acid. There is also some conversion of cis-unsaturated acids to transunsaturated acids.
The process according to the invention can be carried out in either of two ways. In one embodiment, a mixture of saturated and unsaturated carboxylic acids is contacted with a catalyst effective amount of a hydrogenation catalyst to produce a hydrogenated product which may contain oxygenated compounds. The hydrogenated product is then contacted with an effective amount of an adsorbent to decrease the amount of any oxygenated compounds to less than about 200 ppm. The process according to the invention results in the degree of the unsaturation of the starting mixture of carboxylic acids being substantially reduced or eliminated. The hydrogenation is carried out until the iodine value is less than about 10, preferably less than about 5 and most preferably less than about 1.
In another embodiment, a mixture of saturated and unsaturated carboxylic acids is contacted with a catalyst effective amount of a hydrogenation catalyst and in the presence of an effective amount of an adsorbent to produce a hydrogenated product having less than about 200 ppm of oxygenated by-products and an iodine value of less than about 10, preferably less than about 5 and most preferably less than about 1. The degree of unsaturation of the starting mixture of carboxylic acids is substantially reduced or eliminated by the process according to the invention. In this embodiment, the adsorbent can be present as part of the catalyst as, for example, the catalyst support or it can be added separately at the beginning of the hydrogenation.
The mixture of saturated and unsaturated carboxylic acids can be composed of any type of saturated and unsaturated carboxylic acids. The carboxylic acids are generally derived from the splitting or hydrolysis of vegetable oil, tallow or grease. Since the process according to the invention is particularly useful for the commercial production of hydrogenated fatty acids, it can be utilized with a fatty acid stream from the processing of any type of fat or oil. For example, the mixture of carboxylic acids can be a crude fatty acid stream resulting from the splitting or hydrolysis of tallow or vegetable oil. The process is particularly suited to carboxylic acids derived from tallow and/or grease such as choice white grease or yellow grease or vegetable oils. Vegetable oils that are particularly preferred are those that contain a high content of saturated or unsaturated C18 fatty acids, examples of which include, but are not limited to, sunflower oil, soybean oil, canola oil, safflower oil, and corn oil. The process can also be used with the carboxylic acids of tall oil and carboxylic acids derived from the splitting or hydrolysis of oils such as rape s

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