Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process... – Preparing nitrogen-containing organic compound
Reexamination Certificate
2002-02-05
2003-12-30
Lilling, Herbert J. (Department: 1651)
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
Preparing nitrogen-containing organic compound
C435S136000, C435S252100
Reexamination Certificate
active
06670158
ABSTRACT:
FIELD OF THE INVENTION
The invention provides a process for the hydrolysis of acrylonitrile to acrylic acid, and for the hydrolysis of methacrylonitrile to methacrylic acid, in high yield and at high concentration with high specificity. Acrylonitrile or methacrylonitrile is hydrolyzed in a suitable aqueous reaction mixture by an enzyme catalyst characterized by the nitrile hydratase and amidase activities of
Comamonas testosteroni
5-MGAM-4D, producing the corresponding carboxylic acid. The acrylic acid or methacrylic acid is isolated as the acid or corresponding salt.
BACKGROUND OF THE INVENTION
Methacrylic acid and its esters are widely used to produce acrylic sheet, molding products, coatings and impact modifiers, and in applications that include use in detergent builders, rheology modifiers, oil additives, solventless inks, paints, polishes, and coatings. Although several manufacturing processes to produce methacrylic acid exist, the hydrolysis of methacrylamide sulfate (produced from acetone cyanohydrin) accounts for the majority of current commercial production worldwide (W. Bauer, Jr. “Methacrylic Acid and Derivatives” in: Ullmann's Encyclopedia of Industrial Chemistry, 5
th
Ed.; Eds: B. Elvers, S. Hawkins, G. Schulz; VCH, New York, 1990; vol. A 16, pp 441-452; A. W. Gross, J. C. Dobson, “Methacrylic Acid and Derivatives” in: Kirk-Othmer Encyclopedia of Chemical Technology, 4
th
Ed.; Eds: J. I. Kroschwitz, M. Howe-Grant; John Wiley and Sons, New York, 1995; vol. 16, pp 474-506). In this process, approximately 1.6 kg of sulfuric acid is required to produce 1 kg of methacrylic acid via methacrylamide sulfate. Therefore, alternative processes to eliminate sulfuric acid recycle and regeneration (and the significant energy resources required) in current commercial processes for methacrylic acid production are highly desirable.
Methacrylic acid may also be prepared via the ammoxidation of isobutylene to give methacrylonitrile, which is then hydrolyzed to methacrylamide by treatment with one equivalent of sulfuric acid. The methacrylamide can be hydrolyzed to methacrylic acid under conditions similar to those used in the acetone cyanohydrin-based process (Gross et al. supra).
Acrylic acid is primarily used as an intermediate in the production of acrylates, which in turn are used in the production of coatings, finishes, paints, adhesives, and in the manufacture of superabsorbents and detergent builders. Most commercial acrylic acid is produced by the oxidation of propylene. An alternate route to acrylic acid is based on the hydrolysis of acrylonitrile (produced by ammoxidation of propylene) by sulfuric acid. This process is not practiced commercially because of the costs associated with the large amounts of ammonium sulfate waste which is generated (T. Ohara et al., “Acrylic Acid and Derivatives” in: Ullmann's Encyclopedia of Industrial Chemistry, 5
th
Ed.; Ed: W. Gerhartz; VCH, New York, 1985; vol. A1, pp 161-176; W. Bauer, “Acrylic Acid and Derivatives” in: Kirk-Othmer Encyclopedia of Chemical Technology, 4
th
Ed.; Eds: J. I. Kroschwitz, M. Howe-Grant; John Wiley and Sons, New York, 1991; vol. 1, pp 287-314).
Microbial catalysts capable of hydrolyzing methacrylonitrile to methacrylic acid, or acrylonitrile to acrylic acid, do not produce the undesirable ammonium sulfate waste stream that results when using sulfuric acid for this purpose.
Rhodococcus rhodochrous
J1 nitrilase has been used to produce acrylic acid and methacrylic acid from acrylonitrile and methacrylonitrile, respectively (Nagasawa et al.,
Appl. Microbiol. Biotechnol
. 34:322-324 (1990)). This enzyme exhibited marked inhibition when the acrylonitrile concentration was higher than 200 mM, and the conversion rate of methacrylonitrile to methacrylic acid was low when compared to acrylic acid production; for hydrolysis of acrylonitrile, reactions were run with constant monitoring of acrylonitrile concentration, and periodic feeding of acrylonitrile over the course of the reaction was required to maintain the concentration below 200 mM. U.S. Pat. No. 5,135,858 describes the use of nitrilase enzyme from Rhodococcus to convert acrylonitrile to acrylic acid, and methacrylonitrile to methacrylic acid. The specific activity of
R. rhodochrous
J1 nitrilase for methacrylonitrile was only 8% of the specific activity for acrylonitrile.
U.S. Pat. Nos. 5,998,180 and 6,162,624 disclose the use of Rhodococcus nitrilase enzymes for the hydrolysis of acrylonitrile to acrylic acid, and methacrylonitrile to methacrylic acid, where the nitrilase enzymes each have a Km of 500 &mgr;M or below and a Ki of at least 100 mM. In U.S. Pat. No. 5,998,180, it is disclosed that the reaction is preferably performed by maintaining an upper concentration limit of acrylonitrile or methacrylonitrile of 175 mM over the course of the reaction by constant feeding of acrylonitrile. In U.S. Pat. No. 6,162,624, acrylonitrile or methacrylonitrile has an upper concentration limit of 1 or 2 wt % or less, often 0.5 wt % or less, and preferably 0.2 wt % or less, where acrylonitrile or methacrylonitrile is constantly fed over the course of the reaction. The very low concentration of (meth)acrylonitrile present in the reactor necessitates careful control of reactant concentration, in particular for fed batch, and especially for continuous processes.
A recent comparison of two Rhodococcus isolates as catalysts for ammonium acrylate production (one with only a nitrilase activity, and one with only a combination of nitrile hydratase and amidase activities) concluded that the catalyst having a combination of nitrile hydratase and amidase activities was less preferred due to (a) difficulty in inducing the two enzymes in the required ratio, (b) the susceptibility of the two enzymes (nitrile hydratase and amidase) to deactivation by acrylonitrile, and (c) inhibition of the two enzymes by the respective products (Webster et al.,
Biotechnology Letters
, 23:95-101 (2001)).
European Patent Appl. EP 187680 A2 discloses the hydrolysis of acrylonitrile and methacrylonitrile to the corresponding acids using Nocardia, Bacillus, Brevibacterium, Micrococcus, Bacteridium, and Corynebacterium, where light irradiation of the microbial catalysts was required to increase the reaction rate 10-20 fold. Hydrolysis of 200 mM methacrylonitrile by Rhodococcus sp. AJ270 gave the corresponding acid in almost quantitative yield, whereas hydrolysis of acrylonitrile produced acrylic acid in only ca. 70% yield under the same conditions (Meth-Cohn et al.,
J. Chem. Soc., Perkin Trans
. 1, 1099-1104 (1997)).
Microbial catalysts containing only a nitrile hydratase which have been used for the hydration of acrylonitrile to acrylamide are also often susceptible to inactivation by high concentrations of acrylonitrile. Padmakumar and Oriel (
Appl. Biochem. Biotechnol
., 77-79:671-679 (1999)) reported that Bacillus sp. BR449 expresses a thermostable nitrile hydratase, but when used for hydration of acrylonitrile to acrylamide, inactivation of the enzyme occurred at concentration of acrylonitrile of only 2 wt %, making this catalyst unsuitable for commercial applications. Nagasawa et al. (
Appl. Microbiol. Biotechnol
., 40:189-195 (1993)) compare the three microbial nitrile hydratase catalysts which have been used for commercial production of acrylamide from acrylonitrile. Compared to the nitrile hydratase activity of
Rhodococcus rhodochrous
J1, the nitrile hydratase activity of Brevibacterium R312 and
Pseudomonas chlororaphis
B23 catalysts was not stable above 10° C., and the nitrile hydratase activity of all three catalysts was sensitive to the concentration of acrylonitrile in the reaction, where inactivation of the nitrile hydratase occurs at higher concentrations. In commercial use, the concentration of acrylonitrile was maintained at 1.5-2 wt % when using Brevibacterium R312 and
P. chlororaphis
B23 catalysts, while a concentration of up to 7 wt % was used with
R. rhodochrous
J1.
Developing an industrial process using microbial catalysts having nitrilase or nitrile hydrata
Dicosimo Robert
Fallon Robert D.
Gavagan John E.
Manzer Leo Ernest
E. I. du Pont de Nemours and Company
Lilling Herbert J.
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