Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2001-11-13
2004-05-18
Killos, Paul J. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S545000
Reexamination Certificate
active
06737546
ABSTRACT:
FIELD OF THE INVENTION
The field of this invention relates to continuous processes for recovery of acid values from hot gaseous mixtures which are obtained by catalytic oxidation of hydrocarbon compounds with a dioxygen containing gas. More particularly, this invention relates to recovery and refining acid values of at least acrylic acid from a gaseous mixture such as is obtainable by gas-phase catalytic oxidation of propylene. Processes of the invention include quenching the gaseous mixture with an aqueous quench liquid to obtain an aqueous solution comprising the acid values; contacting the aqueous solution with an immiscible extraction solvent; and an integrated sequence of distillations and phase separations to recover for recycle organic components of the extraction solvent, and obtain valuable acrylic acid and acetic acid products. Advantageously, according to the invention the immiscible extraction solvent is substantially free of aromatic compounds such as benzene and toluene.
BACKGROUND OF THE INVENTION
As is well known, most of the commercial acrylic acid is produced from propylene by heterogeneous catalytic oxidation of propylene and/or acrolein in the vapor phase with air and steam. Generally, the two methods for the vapor phase oxidation of propylene are one-stage and two-stage processes. Typically, the process is carried out in two stages giving first acrolein and then acrylic acid. Higher selectivity is possible by using different catalyst compositions and reaction conditions for each of the two stages.
Acrylic acid and esters thereof undergo reactions characteristic of both unsaturated organic compounds and aliphatic carboxylic acids or esters. Acrylic acid and its esters polymerize very easily. Acrylates and acrylic acid are primarily used to prepare emulsion and solution polymers. Emulsion polymerization processes provide high yields of polymers in a form suitable for a variety of applications. Acrylate polymer emulsions are useful as coatings, finishes, and binders for leather, textiles, and paper. Acrylate emulsions are used in the preparation of both interior and exterior paints, floor polishes, and adhesives. Solution polymers of acrylates, frequently with minor concentrations of other monomers, are employed in the preparation of industrial coatings. Polymers of acrylic acid can be used as super-absorbents in disposable diapers, as well as in formulation of superior, reduced-phosphate-level detergents.
Polymerization of acrylic acid and its esters is catalyzed by heat, light, and peroxides and inhibited by compounds such as the monomethyl ether of hydroquinone or hydroquinone, provided oxygen in present. The spontaneous polymerization of acrylic acid is extremely violent.
Commercial production of organic acids is typically accomplished by catalytic oxidation of hydrocarbon compounds having at least one double bond with an oxygen. In particular, production of acrylic acid through gas-phase catalytic oxidation of propylene and/or acrolein is a widely practiced industrial process. This process normally consists of an oxidation step to catalytically oxidize propylene and/or acrolein using molecular oxygen in gaseous phase, a collection step of contacting an aqueous liquid with an acrylic acid-containing gas resulting from the gas-phase catalytic oxidation, and a recovery step to isolate and refine acrylic acid from the aqueous solution of the acrylic acid which is obtained in the collection step.
Unavoidably the acrylic acid-containing gas also contains such co-products as acetaldehyde, formaldehyde, formic acid, and acetic acid, among which acetic acid is in relatively large quantity. For producing high purity acrylic acid, therefore, acetic acid must be removed. Attempts to remove the acetic acid in the acrylic acid by means of distillation, however, tend to induce polymerization of acrylic acid because of the required high distillation temperature. (Boiling point of acetic acid is about 118° C.) There is also another problem that the small specific volatility values of acrylic acid and acetic acid render their separation by simple distillation difficult.
Consequently, with the view to isolate and recover high purity acrylic acid from said aqueous acrylic acid solution, that is, to separate acrylic acid from acetic acid and water to recover high purity acrylic acid which is substantially free from acetic acid and water, normally a method of distilling the aqueous acrylic acid solution in an azeotropic separation column in the presence of an azeotropic solvent is adopted.
A process for isolating acrylic acid from aqueous crude acrylic acid by extraction with a ketone and a complex system of distillations is described in U.S. Pat. No. 3,689,541 in the name of Kurt Sennewald, Heinz Erpenbach, Heinz Handte and Winfried Lork. In this process a liquid—liquid extraction of the aqueous stream uses 3,3,5-trimethylcyclohexanone and/or isophorone as the extractant(s). The extract, containing acrylic acid, acetic acid, high boilers and minor proportions of water which are dissolved in the extractant, is introduced into a first distilling column, which is operated under reduced pressure; the bottom product of the first distilling column, containing the high boilers and the extractant(s) is recycled to the extraction; distillate containing acrylic acid, acetic acid, water and minor proportions of extractant(s) is fed to a second distilling column, which is operated under reduced pressure; a mixture of water and extractant(s) is distilled off; the bottom product of the second distilling column, containing acrylic acid and acetic acid is fed to a third distilling column, which is operated under reduced pressure; and acetic acid is separated as a distillate and acrylic acid is recovered as a bottom product.
Later, U.S. Pat. No. 3,781,192 in the name of Kurt Sennewald, Heinz Erpenbach, Heinz Handte, Georg Kohl and Winfried Lork, describes an extractive azeotropic distillation of aqueous crude acrylic acid using 3,3,5-trimethylcyclohexanone as the distillation aid under a pressure between 20 an 80 mm mercury. The bottom product is said to contain acrylic acid, acetic acid and minor proportions of 3,3,5-trimethylcyclohexanone, residual formaldehyde and higher boiling constituents. Acrylic acid contaminated with 3,3,5-trimethylcyclohexanone is recovered as a distillate, which is separated by further distillations.
Several other organic mixtures have been said to be useful to extract acrylic acid from aqueous solution. For example, U.S. Pat. No. 3,962,074 in the name of Wilhelm Karl Schropp describes acrylic acid separation from aqueous solution by extraction of the solution with a mixture of from 1 to 50 parts by weight of butanol and from 1 to 10 parts by weight of butyl acrylate. U.S. Pat. No. 3,968,153 in the name of Tetsuya Ohrui, Yasuhito Sakakibara, Yukinaga Aono, Michio Kato, Hiroshi Takao and Masami Ayano describes extraction of acrylic acid from aqueous solution with methylethylketone containing from 5 to 20 percent by weight of a xylene or ethylbenzene.
U.S. Pat. No. 5,315,037 in the name of Kazuhiko Sakamoto, Hiroaki Tanaka, Masatoshi Ueoka, Yoji Akazawa and Masao Baba assigned to Nippon Shokubai Co., Osaka, Japan states that a process for producing acrylic acid wherein a mixed gas of acrylic acid and by-products produced by catalytic gas phase oxidation of propylene and/or acrolein is contacted with water to obtain an aqueous solution for azeotropic distillation may be improved by using a mixed solvent consisting of A at least one member selected from the group consisting of diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl-tert-butyl ketone and n-propyl acetate and B at least one member selected from the group consisting of toluene, heptane and methylcyclohexane. According to this process the mixing ratio between A and B must be the range of 50:50 to 75:25 of the weight basis. If the amount of A exceeds the above range, the concentration of acetic acid at the bottom of the azeotropic distillation tower is said to become too high. On the contrary
Miko Steve J.
Wagner David R.
Killos Paul J.
Lurgi AG
Norris & McLaughlin & Marcus
Reyes Hector M.
LandOfFree
Extraction process for recovery of acrylic acid does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Extraction process for recovery of acrylic acid, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Extraction process for recovery of acrylic acid will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3193169