Organic compounds -- part of the class 532-570 series – Organic compounds – Heavy metal containing
Reexamination Certificate
2000-08-10
2001-10-16
Nazario-Gonzalez, Porfirio (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heavy metal containing
Reexamination Certificate
active
06303808
ABSTRACT:
Many tin carboxylates have been synthesized in recent years and have been finding many uses, for example, as additives, reactants, and catalysts for a wide variety of products. For example, tin (II) carboxylates have been used widely as a synthesis catalyst for flexible polyurethane systems, like slab stock polyether-based flexible foams, such as mattresses, and molded flexible foams for the automobiles, furniture, and carpeting markets. In particular, tin (II) 2-ethylhexanoate (stannous 2-ethylhexanoate), tin (II) octoate (stannous octoate), and other tin (II) carboxylate salts are the standard catalysts for polyurethane systems. A survey of the catalysts normally used in industrial polyurethane chemistry and the mechanism on which their action is based can be found in A. Farkas and G. A. Mills, Advan. Catalysis, 13,393 (1962); J. H. Saunders and K. C. Frisch, Polyurethanes, Part I, Wiley-Interscience, New York, 1962, Chapter VI; and K. C. Frisch and L. P. Rumao, J. Macromol. Sci-Revs. Macromol Chem., C5 (1), 103-105 (1970). Such metal catalysts are highly active for urethane formation, increasing the rate of reaction of the isocyanate group with the hydroxyl group of the polyether or polyester. In addition, such tin (II) carboxylates have been used as catalysts for other reactions (see, for example, Cook, U.S. Pat. No. 3,716,523, entitled Low Concentration Stannous Carboxylate Catalysis of Polyesterification, issued Feb. 13, 1973). Tin (II) carboxylates have also been used to prepare a tin (IV) oxide catalyst for converting carbon monoxide and oxygen to carbon dioxide (Kolts, U.S. Pat. No. 5,071,818, entitled Process for Preparation of Tin Dioxide Containing Catalyst Composition, issued Dec. 10, 1991).
In addition, certain tin compounds are known to be used to treat cracking catalysts conventionally employed in the catalytic cracking of hydrocarbons for the production of gasoline, motor fuel, blending components, and light distillates. While the presence of certain metals on such catalysts can be beneficial, the presence of others is detrimental, and it is possible to passivate those deleterious metals by treating the contaminated catalyst with compounds containing antimony, tin, indium or bismuth (see, for example, U.S. Pat. Nos. 4,495,105 and 4,257,919). Tin compounds are particularly useful as passivating agents for vanadium, especially tin (II) dodecanoate and tin (II) octadecanoate.
Such tin (II) carboxylates (stannous carboxylates) are commercially produced using a chloride-based process. This can consist of reacting stannous chloride with sodium carboxylates to produce stannous carboxylates, by reacting stannic chloride with tin metal to form stannous chloride which then reacts with sodium carboxylates to form stannous carboxylates or by reacting Sn metal with aqueous HCl to produce stannous chloride which then reacts with sodium carboxylates to form stannous carboxylates. These commercial methods, which necessarily involve tin chlorides (or other halides) produce a product which contains chloride impurities, which may interfere with its ultimate use and requires the use of hydrochloric acid or chlorine gas.
A method for the preparation of tin (II) acetate is disclosed in the literature; for example, Gmelin, 8
th
Ed., 1975, No. 46, Part C 2, pp. 220-221 discloses the reaction of metallic tin and glacial acetic acid wherein the reaction is permitted to proceed for 80 to 90 hours under reflux conditions and in an inert gas atmosphere. Tin (II) acetate is the sole reaction product.
Miller, U.S. Pat. No. 4,495,105, entitled Preparation of Higher Tin Carboxylates on Improved Yields Using an Inert Gas, issued Jan. 22, 1985, relates to a process for preparing tin carboxylates of higher carboxylic acids by: (a) reacting either tin (II) oxide or tin (IV) oxide with an anhydride of a lower organic acid, (b) reacting the product from (a) with at least one higher carboxylic acid, and (c) recovering the tin carboxylate of the higher carboxylic acid.
Ruf, U.S. Pat. No. 5,068,373, Entitled
Method for the Preparation of Anhydrous Tin—(IV)—Carboxylates
, issued Nov. 26, 1991, relates to a method of reacting metallic tin or tin (II) acetate with an excess of acetic anhydride to produce tin (IV) acetate. The tin (IV) acetate is separated from the reaction mixture and used as separated or, if desired, is subsequently converted to tin (IV) carboxylate having four or more carbon atoms by reaction with the appropriate carboxylic acid.
It is a primary object of the present invention to provide a general method for the production of tin (II) carboxylates and tin (IV) carboxylates which is economical and simple to carry out. Generally, it is an object of the invention to improve on the art of producing tin carboxylates, without the need for tin halides, other organometallic compounds, or carboxylic anhydrides. It is an object of the present invention to provide a process for preparation of higher carboxylates of tin that uses readily available reactants and affords high yields of the desired tin carboxylate. It is another object of the invention to provide a method of preparation wherein the tin carboxylate produced is substantially free of deleterious impurities and has a high level of thermal stability. These and other objects, aspects and advantages of the present invention will become apparent to those skilled in the art from the following description of the invention.
SUMMARY OF THE INVENTION
The present invention achieves these objectives and also exhibits the properties and advantages described herein.
One aspect of the present invention comprises a process for making a product containing tin (II) carboxylates of the formula (RCOO)
2−n
Sn(OOCR′)
n
, where each R, which may be the same or different, is hydrogen or a C
1
-C
40
hydrocarbyl group, each R′, which may be the same or different is a C
1
-C
40
hydrocarbyl group, and n is 0, 1 or 2, the process comprising:
(a) forming a reaction mixture by combining elemental tin, a promoter, and one or more carboxylate-containing compounds of the formula R(CO)X, where R is hydrogen or a C
1
-C
4
hydrocarbyl group and X is a hydroxyl group, a halogen atom, or O(CO)R′—, where R′ is a C
1
-C
40
hydrocarbyl group;
(b) heating the reaction mixture to form a heated reaction mixture;
(c) oxidizing the heated reaction mixture using an oxygen-containing gas to form an oxidized reaction mixture containing tin (II) carboxylate and as well as tin (IV) carboxylates; and
(d) reducing the oxidized reaction mixture with elemental tin to convert at least a portion of the tin (IV) carboxylates to tin (II) carboxylates if stannous compounds are desirable.
In certain embodiments of the invention, the number of moles of elemental tin added to the reaction mixture formed in step (a) is equal to or greater than the stoichiometric number of moles capable of reacting with the carboxylate-containing compounds of the formula R(CO)X to generate stannic or stannous compounds.
In preferred embodiments of the invention, the promoter is selected from the group consisting of: hindered phenols, peroxides, hydroperoxides and hydrocarbons that oxidize to form peroxides and hydroperoxides. Particularly preferred promoters are 4-tert-butylcatechol and 2,5-di-tert-butylhydroquinone.
In a preferred embodiment of the invention, the promoter is added neat to the reaction mixture or in a carrier. In a preferred embodiment of the invention, the carrier is a glycol, alcohol, carboxylic acid or polyglycol. Particularly preferred carriers are 2-ethyl 1-hexanoic acid and dipropylene glycol. In a preferred embodiment of the invention, the oxygen-containing gas is air.
In a preferred embodiment of the invention, the elemental tin is in a form selected from the group consisting of: ingots, bars, sheets, foils,rods, wires, chips, shavings, shot, beads, granules, mossy tin, powder, and dust. In another preferred embodiment of the invention, the oxidation step (c) is performed at from about 100° C. to about 200° C. In yet another preferred embodiment of the inve
Bacalogu Radu
Brecker Lawrence R.
Fisch Michael
Kleinlauth Philip J.
Knezevic Vasilije
Crompton Corporation
Nazario-Gonzalez Porfirio
Scully Scott Murphy & Presser
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