METHOD FOR PREPARING AN AQUEOUS ACRYLAMIDE SOLUTION HAVING A LOW ACRYLIC ACID CONCENTRATION

Abstract

The present invention relates to methods for preparing an aqueous acrylamide solution having a low acrylic acid concentration. In addition, the present invention relates to methods for reducing the acrylic acid concentration of an aqueous acrylamide solution. The methods involve a bioconversion of acrylonitrile to acrylamide in the presence of a biocatalyst, wherein during the bioconversion the content of acrylonitrile is maintained at 0.3 w/w % or more referred to the total weight of the composition in the reactor. Also provided is an aqueous acrylamide solution which is obtained by the methods of the present invention. Furthermore, the present invention is related to an acrylamide homopolymer or copolymer obtained by polymerizing the acrylamide of the aqueous solution.

Claims

1. A method for preparing an aqueous acrylamide solution, the method comprising: (a) adding acrylonitrile, water, and a biocatalyst capable of converting acrylonitrile to acrylamide to a reactor to obtain a composition for bioconversion; (b) performing a bioconversion of the acrylonitrile to acrylamide in the reactor; and (c) adding further acrylonitrile such that a content of acrylonitrile during the bioconversion is maintained at 0.3 w/w % or more, relative to the total weight of the composition in the reactor, for 10 minutes to 48 hours.

2. A method for preparing an aqueous acrylamide solution, the method comprising: (a) adding acrylonitrile, water, and a biocatalyst capable of converting acrylonitrile to acrylamide to a reactor to obtain a composition for bioconversion; (b) performing a bioconversion of the acrylonitrile to acrylamide in the reactor; and (c) adding further acrylonitrile such that a content of acrylonitrile during the bioconversion is maintained at 0.3 w/w % or more until an acrylamide content reaches at least 20 w/w %, relative to the total weight of the composition in the reactor.

3. A method for reducing an acrylic acid concentration of an aqueous acrylamide solution prepared by converting acrylonitrile to acrylamide using a biocatalyst, the method comprising: (a) adding acrylonitrile, water, and a biocatalyst capable of converting acrylonitrile to acrylamide to a reactor to obtain a composition for bioconversion; (b) performing a bioconversion of the acrylonitrile to acrylamide in the reactor; and (c) adding further acrylonitrile such that a content of acrylonitrile during the bioconversion is maintained at 0.3 w/w % or more, relative to the total weight of the composition in the reactor.

4. The method according to claim 1, wherein an acrylic acid concentration of the composition at the end of the bioconversion is 1500 ppm or less, relative to the total weight of the composition at the end of the bioconversion.

5. A method for preparing an aqueous acrylamide solution, comprising: (a) adding acrylonitrile, water, and a biocatalyst capable of converting acrylonitrile to acrylamide to a reactor to obtain a composition for bioconversion; (b) performing a bioconversion of the acrylonitrile to acrylamide in the reactor; (c) adding further acrylonitrile such that a content of acrylonitrile during the bioconversion is maintained at 0.3 w/w % or more, relative to the total weight of the composition in the reactor; and (d) obtaining a composition at the end of the bioconversion, which has an acrylic acid concentration of 1500 ppm or less, relative to the total weight of the composition at the end of the bioconversion.

6. The method of claim 1, wherein a weight ratio of the biocatalyst, acrylonitrile and water added during the (a) to (c) is 0.001 to 0.5 w/w % of the biocatalyst, 22 to 45 w/w % of acrylonitrile and a balance to 100 w/w % of water, relative to the total weight (100 w/w %) of the combined weights of the biocatalyst, acrylonitrile and water added during the (a) to (c).

7. The method of claim 1, wherein the bioconversion is performed at a temperature of from 5° C. to 40° C. for 10 minutes to 48 hours.

8. The method of claim 1, wherein the content of acrylonitrile during the bioconversion is maintained at 6 w/w % or less, relative to the total weight of the composition in the reactor.

9. The method of claim 1, wherein the adding of further acrylonitrile comprises: (i) maintaining an acrylonitrile content in a first range for a first period of time; (ii) decreasing the acrylonitrile content from the first range to a second range; and (iii) maintaining an acrylonitrile content in the second range for a second period of time.

10. The method of claim 9, wherein the first range is from 1.2 w/w % to 6 w/w % relative to the total weight of the composition in the reactor, the first period of time is from 30 minutes to 4 hours, the second range is from 0.3 w/w % to 1.2 w/w % relative to the total weight of the composition in the reactor, and the second period of time is from 30 minutes to 24 hours.

11. The method of claim 10, wherein the first range is from 1.2 w/w % to 4 w/w % relative to the total weight of the composition in the reactor, the first period of time is from 30 minutes to 3 hours, the second range is from 0.5 w/w % to 1.1 w/w % relative to the total weight of the composition in the reactor, and the second period of time is from 30 minutes to 12 hours.

12. The method of claim 11, wherein the first range is from 1.3 w/w % to 3 w/w % relative to the total weight of the composition in the reactor, the first period of time is from 30 minutes to 2 hours, the second range is from 0.6 w/w % to 1.0 w/w % relative to the total weight of the composition in the reactor, and the second period of time is from 1 hour to 8 hours.

13. The method of claim 1, wherein the method is carried out using a semi-batch process.

14. The method of claim 1, wherein the content of acrylonitrile is measured using Fourier Transform Infrared Spectroscopy (FTIR).

15. The method of claim 1, wherein the biocatalyst encodes the enzyme nitrile hydratase.

16. The method of claim 1, wherein the biocatalyst is at least one selected from the group consisting of Rhodococcus, Aspergillus, Acidovorax, Agrobacterium, Bacillus, Bradyrhizobium, Burkholderia, Escherichia, Geobacillus, Klebsiella, Mesorhizobium, Moraxella, Pantoea, Pseudomonas, Rhizobium, Rhodopseudomonas, Serratia, Amycolatopsis, Arthrobacter, Brevibacterium, Corynebacterium, Microbacterium, Micrococcus, Nocardia, Pseudonocardia, Trichoderma, Myrothecium, Aureobasidium, Candida, Cryptococcus, Debaryomyces, Geotrichum, Hanseniaspora, Kluyveromyces, Pichia, Rhodotorula, Comomonasz, and Pyrococcus.

17. The method of claim 16, wherein the biocatalyst is at least one selected from the group consisting of Rhodococcus, Pseudomonas, Escherichia and Geobacillus.

18. The method of claim 1, wherein the biocatalyst is at least one selected from the group consisting of Rhodococcus rhodochrous, Rhodococcus pyridinovorans, Rhodococcus erythropolis, Rhodococcus equi, Rhodococcus ruber, Rhodococcus opacus, Aspergillus niger, Acidovorax avenae, Acidovorax facilis, Agrobacterium tumefaciens, Agrobacterium radiobacter, Bacillus subtilis, Bacillus pallidus, Bacillus smithii, Bacillus sp BR449, Bradyrhizobium oligotrophicum, Bradyrhizobium diazoefficiens, Bradyrhizobium japonicum, Burkholderia cenocepacia, Burkholderia gladioli, Escherichia coli, Geobacillus sp. RAPc8, Klebsiella oxytoca, Klebsiella pneumonia, Klebsiella variicola, Mesorhizobium ciceri, Mesorhizobium opportunistum, Mesorhizobium sp F28, Moraxella, Pantoea endophytica, Pantoea agglomerans, Pseudomonas chlororaphis, Pseudomonas putida, Rhizobium, Rhodopseudomonas palustris, Serratia liquefaciens, Serratia marcescens, Amycolatopsis, Arthrobacter, Brevibacterium sp CH1, Brevibacterium sp CH2, Brevibacterium sp R312, Brevibacterium imperiale, Brevibacterium casei, Corynebacterium nitrilophilus, Corynebacterium pseudodiphteriticum, Corynebacterium glutamicum, Corynebacterium hoffmanii, Microbacterium imperiale, Microbacterium smegmatis, Micrococcus luteus, Nocardia globerula, Nocardia rhodochrous, Nocardia sp 163, Pseudonocardia thermophila, Trichoderma, Myrothecium verrucaria, Aureobasidium pullulans, Candida famata, Candida guilliermondii, Candida tropicalis, Cryptococcus flavus, Cryptococcus sp UFMG-Y28, Debaryomyces hanseii, Geotrichum candidum, Geotrichum sp JR1, Hanseniaspora, Kluyveromyces thermotolerans, Pichia kluyveri, Rhodotorula glutinis, Comomonas testosteroni, Pyrococcus abyssi, Pyrococcus furiosus, and Pyrococcus horikoshii.

19. The method of claim 18, wherein the biocatalyst is Rhodococcus rhodochrous.

20. The method of claim 18, wherein the biocatalyst is Rhodococcus pyridinovorans.

21. The method of claim 1, wherein the biocatalyst has been dried before being added to the reactor.

22. The method of claim 21, wherein the biocatalyst has been dried by freeze-drying, spray drying, heat drying, vacuum drying, fluidized bed drying, spray granulation, or a combination thereof.

23. The method of claim 21, wherein the dried biocatalyst is added to the reactor.

24. The method of claim 21, wherein the dried biocatalyst is reconstituted before being added to the reactor.

25. The method of claim 24, wherein the biocatalyst is reconstituted by suspending in an aqueous composition.

26. An aqueous acrylamide solution, obtained by the method of claim 1.

27. The aqueous acrylamide solution according to claim 26, containing 35 to 65 w/w % of acrylamide having an acrylic acid concentration of not more than 1500 ppm, relative to the total weight of the solution.

28. The aqueous acrylamide solution of claim 26, wherein the acrylamide content, the acrylic acid concentration, or both, are determined using HPLC.

29. An acrylamide homopolymer or copolymer, obtained by polymerizing acrylamide of the aqueous acrylamide solution of claim 26.

30. The acrylamide homopolymer or copolymer of claim 29, having an acrylic acid content of 60,000 ppm or less, relative to the total weight of the solid acrylamide homopolymer or copolymer.

31. The acrylamide homopolymer or copolymer of claim 29, wherein the acrylamide copolymer is a cationic polyacrylamide.

32. The acrylamide homopolymer or copolymer of claim 30, wherein the acrylic acid content is determined using NMR spectroscopy.

33. A solution, comprising: the acrylamide homopolymer or copolymer of claim 29; and seawater.

Description

EXAMPLES

Example 1

[0102] In a semi-batch process acrylonitrile and 2446 g of water were placed in a glass reactor, wherein the acrylonitrile was in each run added such that a concentration of acrylonitrile was reached in the reactor as set out below in Table 1. Then the dried biocatalyst Rhodococcus rhodochrous, strain NCIMB 41164 was added to initiate the bioconversion. During the bioconversion further acrylonitrile was added at a controlled rate while the content of acrylonitrile was constantly maintained at the initial value outlined in Table 1. With this respect, the contents of acrylonitrile and acrylamide were measured online during the bioconversion using Fourier Transform Infrared Spectroscopy (FTIR). All in all, 1553 g of acrylonitrile, which is the total amount of acrylonitrile placed in the reactor before starting the bioconversion and added during the reaction, was converted into acrylamide. At the end of the reaction 4 kg of an aqueous acrylamide solution having a content of 52 w/w % acrylamide based on the total weight of the composition in the reactor was obtained.

[0103] The following Table 1 shows different runs of the method as described in the preceding paragraph at temperatures of 20° C. and 26° C., respectively, wherein different amounts of the biocatalyst were used and the acrylonitrile content was maintained at different values during the bioconversion.

TABLE-US-00005 TABLE 1 Content of Concentration Amount acrylonitrile End of of acrylic acid Temper- of bio- maintained during biocon- at end of ature catalyst the bioconversion version bioconversion Run [° C.] [g] [w/w %]* [h] [ppm]** 1 20 1.3 0.5 6.7 287 2 2 6.4 130 3 1.47 0.5 4.9 246 4 5 10.2 44 5 1.84 0.5 5 202 6 2 3.8 154 7 2.75 2.8 80 8 2.21 0.5 3.2 111 9 5 2.7 59 10 26 1.3 0.5 4.7 297 11 2 5.1 206 12 1.84 0.5 3.3 308 13 2 2.5 164 14 2.75 2.2 68 15 2.2 74 16 2.3 69 *measured online during the bioconversion using Fourier Transform Infrared Spectroscopy (FTIR) **determined using HPLC according to the method provided below

[0104] The results outlined in Table 1 show that by maintaining the acrylonitrile content during the bioconversion at 0.3 w/w % or more aqueous acrylamide solutions are produced having low concentrations of acrylic acid. In particular, the results indicate that by increasing the content of acrylonitrile, which is maintained during the bioconversion, the concentration of acrylic acid in the obtained aqueous acrylamide solutions is reduced.

Example 2

[0105] The runs of the bioconversion of acrylonitrile to acrylamide were carried out under the same conditions as of Example 1, except:

(i) a higher content of acrylonitrile was maintained from the beginning of the bioconversion for 1 hour;
(ii) after 1 hour from the beginning of the bioconversion the acrylonitrile content was decreased to a lower acrylonitrile content; and
(iii) the lower acrylonitrile content was maintained until the end of the bioconversion, i.e. until conversion of 1553 g acrylonitrile to form 4 kg of an aqueous acrylamide solution having a content of 52 w/w % acrylamide based on the total weight of the composition in the reactor.

[0106] The specific conditions and results are shown in Table 2.

TABLE-US-00006 TABLE 2 Content of Concentration Amount acrylonitrile End of of acrylic acid Temper- of bio- maintained during biocon- at end of ature catalyst the bioconversion version bioconversion Run [° C.] [g] [w/w %]* [h] [ppm]** 1 26 0.91 0.8 (maintained over 5.73 482 whole time of the bioconversion) 2 1.5 (maintained over 5.94 273 1 hour from beginning of bioconversion), then 0.8 (maintained until end of bioconversion) 3 2 (maintained over 1 5.79 202 hour from beginning of bioconversion), then 0.8 (maintained until end of bioconversion) *measured online during the bioconversion using Fourier Transform Infrared Spectroscopy (FTIR) **determined using HPLC according to the method provided below

[0107] In run 1 of Table 2 the content of acrylonitrile was maintained at 0.8 w/w % during the whole bioconversion. In runs 2 and 3 a higher content of 1.5 and 2 w/w % of acrylonitrile, respectively, was maintained until one hour from the beginning of the bioconversion. After one hour, the content of acrylonitrile was decreased to 0.8 w/w % and maintained at this value until the end of the bioconversion.

[0108] The results show that, at comparable times required until the end of the bioconversion, the concentration of acrylic acid in the obtained aqueous acrylamide solutions is further reduced in case that a higher content of acrylonitrile is maintained over a certain period of time, then the content of acrylonitrile is decreased to a lower content of acrylonitrile and this lower content of acrylonitrile is maintained until the end of the bioconversion.

Example 3

[0109] Water and 18 g of acrylonitrile were placed in a reactor. The amount of water was adjusted so that the total amount of water and biocatalyst was 1835 g. Two different forms (i) and (ii) of a biocatalyst were used in independent runs as set forth in the following:

(i) a fermentation broth containing cells of Rhodococcus rhodochrous, strain J1 (FERM-BP 1478), with a NHase acticvity of 1512 kU/kg and a water content of 96.1 w/w %; and
(ii) a dry powder obtained by concentration of (i) by centrifugation up to a water content of 83.6 w/w % and then freeze drying of the concentrate. The water content of the dry powder was 13 w/w % and the NHase activity was 211 kU/g.

[0110] The biocatalyst was added to the reactor, whereby the reaction started. During the bioconversion 1147 g of additional acrylonitrile was added so that the overall reaction batch size at the end was 3000 g. The temperature was kept constant at 23° C. during the reaction. The content of acrylonitrile was measured online during the bioconversion using Fourier Transform Infrared Spectroscopy (FTIR), and the rate of addition of acrylonitrile was adjusted so that the acrylonitrile content in the reaction mixture was kept constant at 1.0±0.1 w/w % or 0.3 w/w % until the entire acrylonitrile had been added to the reactor. The reaction was stopped after the acrylonitrile content had decreased to <100 ppm due to conversion. At the end of the reaction, the acrylamide concentration in every run was 51 w/w %.

[0111] The conditions and results are shown in Table 3 below.

TABLE-US-00007 TABLE 3 Content of Concentra- acrylonitrile tion of Amount maintained Re- acrylic acid of bio- during the action at end of Biocatalyst catalyst bioconversion time bioconversion Run form [g] [w/w %]* [h] [ppm]** 1 Fermentation 143 0.3 7.5 885 broth (i) 2 Fermentation 143 1 5.7 604 broth (i) 3 Freeze-dried 0.92 0.3 6.6 568 powder (ii) 4 Freeze-dried 0.92 1 5.0 305 powder (ii) *measured online during the bioconversion using Fourier Transform Infrared Spectroscopy (FTIR) **determined using HPLC according to the method provided below

[0112] The results of Table 3 show that by using a dried biocatalyst in a bioconversion in which the acrylonitrile content is kept constant the concentration of acrylic acid in the obtained aqueous acrylamide solutions is reduced compared to employing a biocatalyst which has not been subjected to drying.

[0113] In the aforementioned examples the concentration of acrylic acid in the obtained aqueous acrylamide solutions was determined using HPLC. The following conditions were applied in order to determine the contents of acrylamide, acrylic acid and acrylonitrile:

[0114] Column: Aqua C18, 250*4.6 mm (Phenomenex)

[0115] Guard column: C18 Aqua

[0116] Temperature: 40° C.

[0117] Flow rate: 1.00 ml/min

[0118] Injection volume: 1.0 μl

[0119] Detection: UV detector, wavelength 210 nm

[0120] Stop time: 8.0 minutes

[0121] Post time: 0.0 minutes

[0122] Maximum pressure: 250 bar

[0123] Eluent A: 10 mM KH.sub.2PO.sub.4, pH 2.5

[0124] Eluent B: Acetonitrile

[0125] Gradient:

TABLE-US-00008 Time [min] A [%] B [%] Flow [ml/min] 0.0 90.0 10.0 1.00 8.0 90.0 10.0 1.00

[0126] Matrix: Fermentation broths, bioconversion mixtures [0127] Sample is filtered through 0.22 μm

[0128] Analytes:

TABLE-US-00009 Retention time [min] Acrylamide 3.29 Acrylic acid 3.91 Acrylonitrile 4.35