Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-05-26
2001-11-13
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S853000, C549S374000
Reexamination Certificate
active
06316679
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a novel process for treating a composition comprising a trimethylolalkane bis-monolinear formal such as that obtained as a heavy ends residue from the purification of a crude trimethylolalkane product, to obtain useful compounds.
2. Description of the Related Art
Trimethylolpropane (TMP) and trimethylolethane (TME) are well-known chemical commodities used as intermediates in the production of a wide variety of products, e.g., varnishes, alkyd and polyester resins, synthetic drying oils, urethane foams and coatings, silicone lube oils, lactone plasticizers, textile finishes, surfactants, epoxidation products, etc. TMP and TME are made by reacting one mole of n-butyraldehyde or propionaldehyde respectively with an amount in excess of 3 moles of formaldehyde in an aqueous medium and in the presence of an alkaline condensation agent. However, these conditions result in the formation of not only TMP or TME, but also various higher boiling impurities. Thus it is necessary to subject the crude TMP or TME product obtained from the reaction to a purification process including distillation and solvent extraction steps, not only to separate relatively pure UMP or TME from excess formaldehyde, water, and basic condensation agent, but also from the higher boiling impurities.
A critical step in the purification process for obtaining relatively pure TMP or TME from the crude product of the reaction is a vacuum distillation or “flashing” of the bulk of the TMP or TME produced in the reaction, which is thus removed as a vapor from the higher boiling impurities remaining behind as a liquid heavy ends residue. While the residue may still contain some TMP or TME, the percentage of such desirable compound is fairly low and is difficult to recover economically. Furthermore, several of the high boiling impurities produced by the reaction in fairly large amounts have only limited commercial value. Thus, any expedient for treating the heavy ends residue, or any compound present in such residue in large amount, so as to convert at least a portion of such compound to TMP or TME and/or other more valuable compounds, would be very desirable.
U.S. Pat. No. 3,076,854 issued Feb. 5, 1963 to Klein, discloses the purification of crude TMP product by a process comprising extracting the reaction liquor with a water immiscible solvent for TMP, e.g., n-butanol or amyl alcohol, subjecting the extract to further extraction with water to obtain a re-extract containing TMP contaminated with metal formate and polyhydric by-products; separating the aqueous re-extract from the stripped solvent, heating the contaminated TMP with methanol or other lower alkanol and a mineral acid to convert the metal formate to a salt of the added acid, and further treating the aqueous TMP re-extract with an acidic cation-exchange resin to remove metal ions from the solution. British Patent No 1,290,036 discloses a process for removing trimethylpropane monomethyl formal from a crude TMP product by treating the product with a sulfonic acid cation exchange resin. The trimethylolpropane monomethyl formal decomposes to form trimethylolpropane monocyclic formal and methanol.
German Democratic Republic Patent No. 142184 discloses a process for the recovery of TMP from higher boiling residues comprising adding water and methanol to the residues such that they contain at least 15 wt. % of water or 10-40 wt. % of methanol, pretreating the residues with a cation exchange resin to remove traces of condensation agent contained in the residues, treating the residues under distillation conditions with a highly acidic, highly crosslinked cation-exchange resin with a polystyrene base, and recovering the TMP formed by conventional separation means.
BRIEF SUMMARY OF THE INVENTION
As part of the invention disclosed herein, it has been discovered that a major proportion of the heavy ends residue obtained after removing the bulk of the TMP or TME, excess formaldehyde, water, and basic condensation agent, is a trimethylolalkane bis-monolinear formal having the formula,
where R is ethyl in the case of trimethylolpropane bis-monolinear formal (TMP-BMLF) CA Index Name 1,3-Propanediol, 2,2′-[methylenebis(oxymethylene)]bis[2-ethyl-], CAS No. [93983-16-5] or methyl in the case of trimethylolethane bis-monolinear formal (TME-BMLF) CA Index Name 1,3-Propanediol, 2,2′-[methylenebis(oxymethylene)]bis[2-methyl-], CAS No. [636073-72-5]. Thus, in accordance with the broadest aspect of the invention, a composition comprising a substantial percentage, e.g., at least about 40 wt. %, of TMP-BMLF or TME-BMLF, no more than about 5 wt. % of water, and no more than about 0.5 wt. % of methanol, all percentages based on the total weight of the composition, is contacted with a strong acid catalyst at an elevated temperature and a sufficient period of time to convert a significant amount of said TMP-BMLF or TME-BMLF to TMP or TME and the corresponding trimethylolalkane monocyclic formal having the following formula,
where R is ethyl in the case of trimethylolpropane monocyclic formal (TMP-MCF) CA Index Name 1,3-Dioxane-5-methanol, 5-ethyl, CAS No. [5187-23-5] or methyl in the case of trimethylolethane monocyclic formal (TME-MCF) CA Index Name 1,3-Dioxane-5-methanol, 5-methyl, CAS No. [1121-97-7]. The additional TMP and TMP-MCF or TME and TME-MCF produced by the process have considerably greater value than the TMP-BMLF or TME-BMLF consumed. In many instances the composition treated is a heavy ends residue obtained from a crude TMP or TME product in the course of a purification treatment after the bulk of water, excess formaldehyde, basic condensation agent, and purified TMP or TME have been separated.
DETAILED DESCRIPTION OF THE INVENTION
The composition subjected to the acid treatment of this convention will in many instances contain, for example, at least about 10 wt. %, preferably at least about 20-30 wt. % of TMP-BMLF or TME-BMLF, generally anhydrous to no more than about 5 wt. %, preferably no more than about 1.0 wt. % of water, and no more than about 0.5 wt. %, preferably no more than about 0.1 wt. % of methanol. In addition, the composition being treated will usually contain no more than about 5 wt. %, preferably no more than about 0.6 wt. % of any compound in free form having an atmospheric boiling below that of water, such as formaldehyde. The composition is contacted at an elevated temperature, e.g., about 30° C. to about 300° C. preferably about 90° C. to about 220° C., with a strong acid catalyst, for a period of time, e.g., of about 2 to about 8 hours, preferably about 1 to about 6 hours, sufficient to convert a significant amount of the TMP-BMLF or TME-BMLF to TMP and TMP-MCF or TME and TME-MCF respectively.
Any strong acid can be used as a catalyst for the process of the invention. While such acid may be an inorganic acid such as sulfuric or phosphoric, it is preferred in most instances to employ an alkanesulfonic acid such as methanesulfonic acid, an arylsulfonic acid such as toluenesulfonic acid, or a sulfonated cation-exchange resin in acid form, e.g., a sulfonated polystyrene-based cation exchange resin. The amount of acid may vary widely, but is often in an amount such that the acidity of conversion reaction is in the range, for example, equivalent to the acidity contributed by the strong acid, less than about 15 wt. %, preferably about 0.3 to about 1.3 wt. %.
Generally a strong acid is added in sufficient amount to result in a pH range of the reaction of less than about 4, and preferably between about 2 and 3, purified BMLF has been found to optimally convert to TMP at about 102° C., pH of about 2.35 in about 4 hours.
As suggested previously, a small amount of water under 5 wt. % may be present in the composition subjected to the acid treatment of this invention. Furthermore, an additional amount of water is produced by the conversion of TMP-BMLF or TME-BMLF to TMP-MCF or TME-MCF respectively. A
Broussard Jerry A.
Marks Tobin J.
Slinkard William E.
Supplee Carolyn
Zey Edwards G.
Barts Samuel
Celanese International Corporation
Prize Elvis O.
Spiering M. Susan
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