Organic compounds -- part of the class 532-570 series – Organic compounds – Fatty compounds having an acid moiety which contains the...
Reexamination Certificate
2001-03-02
2002-09-24
Carr, Deborah (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Fatty compounds having an acid moiety which contains the...
C554S128000, C554S141000, C554S145000, C502S077000, C502S078000
Reexamination Certificate
active
06455716
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for the branching of saturated and/or unsaturated linear fatty acids and/or alkyl esters thereof utilizing a crystalline, porous solid acid catalyst, such as a zeolite, which also contains metal sites.
BACKGROUND OF THE INVENTION
Branched alkyl fatty acids and alkyl esters are useful in a number of consumer products, including surfactants, fabric conditioners, cosmetics, and lubricants. Branched fatty acids and alkyl esters which are saturated offer a number useful features, including lubricity/surfactancy due to their chainlength and random branching, oxidative stability due to little or no carbon—carbon double bonds present, and low crystallinity over a wide range of temperatures due to a significantly lower melt point compared to their linear counterparts.
A number of various processes for making branched fatty acids and esters have been previously disclosed. One approach involves the exclusive use of unsaturated fatty acids or alkyl ester feedstocks using a microporous catalyst. For example, U.S. Pat. No. 5,856,539, issued Jan. 5, 1999 to Hodgson et al., discloses a process for converting unsaturated fatty acids into branched fatty acids by using catalysts having a microporous. structure, such as zeolites. In addition, U.S. Pat. No. 5,677,473, issued Oct. 14, 1997 to Tomifuji et al., discloses a process for preparing branched chain fatty acids or alkyl esters by subjecting unsaturated fatty acids or esters having 10 to 25 carbon atoms to a skeletal isomerization reaction in the presence of water or a lower alcohol using a zeolite catalyst having a linear pore structure that is small enough to minimize dimerization and large enough to allow diffusion of the branched molecules. Both of these patents have numerous disadvantages, including high feedstock costs (i.e. oleic acid), relatively high yields of by-products such as oligomers, and high equipment capital costs due to the need for custom separation processes (i.e. molecular distillation to recover dimers and trimers).
A second approach involves the use of saturated fatty acids and non-microporous catalysts. For example, U.S. Pat. No. 3,090,807, issued May 21, 1963 to Illing, describes the branching of saturated aliphatic carboxylic acids by heating with carbon monoxide in the presence of (a) a metal carbonyl, (b) a halogen, such as chlorine, bromine, or iodine, (c) an activator, such as compounds of bismuth, antimony, titanium, boron, iron, or tin, and (d) water. In addition, WO 98/07680 published Feb. 26, 1998 by Roberts et al., describes the branching of saturated or unsaturated fatty acids or their derivitives using a binary ionic liquid catalyst, such as a metal chloride and/or an organic or inorganic halide salt. Both of these patents have numerous disadvantages, including high operating costs associated with using the types of catalysts described above, high equipment capital costs associated with corrosion prevention when using halogens or ionic liquids, and also the environmental issues associated with disposal of these materials.
A third approach is a totally synthetic based route to making branched fatty acids or alkyl esters. UlIman's Encyclopedia of Industrial Chemistry (Volume A5, 5
th
Ed., 1986, pp. 239-240) describes four different approaches to making synthetic fatty acids, including carbonylation of olefins, carboxylation of olefins, oxidation of alkanes, and alkali fusion of alcohols. The first two approaches result in significant quantities of branched molecules. Carbonylation of olefins is currently the principal method for the commercial production of C
4
-C
13
carboxylic acids. Because of the complex nature of the olefinic raw materials, the higher carboxylic acids obtained in this process (C
8
and higher) are usually mixtures of branched chain products. The disadvantages of these types of approaches to making branched acids and/or alkyl esters include the high capital cost and yield losses associated with a multi-step synthetic route (i.e. linear olefin synthesis, olefin branching, hyroformulation, and oxidation for the carbonylation process) vs. that of the natural route (i.e. hydrolysis of triglycerides, followed by branching of the fatty acid), as well as the undesirability of using non-renewable, petroleum based feedstocks as opposed to using renewable, natural based fatty acid or methyl ester feedstocks.
Crystalline, microporous solid acid catalysts, containing metal sites have also been disclosed. For example, U.S. Pat. No. 4,882,307, issued Nov. 21, 1989 to Tsao discloses a process for preparing noble metal-containing zeolites having high metal dispersion. The catalysts are used in processes such as hydrogenation, dehydrogenation, dehydrocyclization, isomerization, hydrocracking, dewaxing, and reforming of materials such as hydrocarbons. However, these types of catalysts have not heretofor been used to catalyze isomerization reactions to branch saturated and/or unsaturated fatty acids and/or alkyl esters thereof.
It is the object of the present invention to create an efficient process for branching saturated or unsaturated fatty acids and/or alkyl esters thereof to achieve significant quantities of branched molecules using a crystalline, microporous solid acid catalyst, such as a zeolite, with metal sites present.
It is a further object of the present invention to create a process that uses renewable, natural-based feedstocks such as linear fatty acids derived from vegetable or animal sources, which is also environmentally friendly from the standpoint of waste disposal of catalysts or other process aids.
SUMMARY OF THE INVENTION
The present invention encompasses a process for branching saturated and/or unsaturated fatty acids and/or alkyl esters thereof comprising the steps of:
(a) subjecting a feedstock comprising saturated and/or unsaturated fatty acids having from 3 to 25 carbon atoms, alkyl esters thereof, or mixtures thereof, to a skeletal isomerization reaction using a catalyst comprising a crystalline porous structure having incorporated therein a metal to form metal sites on said catalyst; and
(b) isolating branched fatty acids, alkyl esters thereof, or mixtures thereof, from a reaction mixture obtained by said skeletal isomerization reaction.
The catalyst utilized in the present process is preferably a zeolite catalyst containing metal sites of Group VIII metal. The process is carried out in the presence of hydrogen gas, or a mixture of gases including hydrogen gas, under pressure.
The present invention further encompasses the present process further comprising a recycle step in which higher yields of branched molecules can be obtained.
DETAILED DESCRIPTION OF THE INVENTION
It has now been found that it is possible to convert (by isomerization) a feed of fatty acids and/or alkyl esters comprising saturated and/or unsaturated fatty acids and/or alkyl esters thereof (e.g. oleic, stearic, palmitic, myristic) into a mixture which has a significant content of branched fatty acids and/or alkyl esters. In the present process, a fatty acid and/or alkyl ester feed comprising either saturated and/or unsaturated fatty acids and/or alkyl esters is contacted with a catalyst, wherein the catalyst comprises a material having a crystalline microporous structure containing metal sites, preferably a zeolite catalyst containing metal sites, particularly Group VIII metal sites. The reaction which is the subject of this invention can be seen as an isomerization reaction (involving both skeletal and positional isomerization). The branching reaction is herein included.
The process of the present invention is to prepare branched chain fatty acids and/or alkyl esters thereof from either saturated and/or unsaturated fatty acids and/or alkyl esters having a total carbon number of from about 3 to about 25, comprising at least a step wherein skeletal isomerization is carried out at a temperature of from about 240° C. to 380° C., preferably in the presence of a gas selected from the group consisting of hydrogen, nitrogen, carbon dioxide, argon,
Connor Daniel Stedman
Kenneally Corey James
Carr Deborah
Matthews Armina E.
Miller Steven W.
The Proctor & Gamble Company
William Zerby Kim
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