A METHOD FOR THE PURIFICATION OF ETHYLENE CYANOHYDRIN

Abstract

A process for purifying ethylene cyanohydrin involves incubating an industrial grade ethylene cyanohydrin product with at least one titanium(IV)alkoxide. Ethylene cyanohydrin products with purities of >99% contain less than 0.05% of ethylene glycol (EG), and/or contain a water content of less than 1000 ppm.

Claims

1. A process for purifying ethylene cyanohydrin (ECH), the process comprising: incubating industrial grade ethylene cyanohydrin with at least one titanium(IV) alkoxide.

2. The process according to claim 1, wherein the at least one titanium(IV) alkoxide in the incubation is present in amounts of between 1 wt. % and 15 wt. %.

3. The process according to claim 1, wherein the at least one titanium(IV) alkoxide is at least one titanium(IV) alkylalkoxide Ti(OR).sub.4 with R=C.sub.1-C.sub.20 linear or branched.

4. The process according to claim 1, wherein the alkyl titanate is Ti(O/Pr.sub.4).

5. The process according to claim 1, wherein the incubation is performed under stirring at a temperature between 20 C. and 70 C.

6. The process according to claim 1, wherein the incubation is performed under stirring at a temperature of between 2.5 C. and 50 C.

7. The process according to claim 1, wherein an incubation time is between 0.5 h and 20 h.

8. The process according to claim 1, wherein the industrial grade ethylene cyanohydrin is obtained by reacting ethylene oxide with hydrocyanic acid (HCN).

9. The process according to claim 1, wherein the industrial grade ethylene cyanohydrin is obtained by catalytic addition of water to acrylonitrile.

10. The process according to claim 1, further comprising a distillation.

11. Ethylene cyanohydrin (ECH), having a purity of >99% and comprising less than 0.05% of ethylene glycol (EG).

12. The ethylene cyanohydrin of claim 11, comprising less than 0.01% of EG.

13. The ethylene cyanohydrin of claim 11, comprising a water content of less than 1000 ppm.

14. The ethylene cyanohydrin of claim 11, comprising a water content of less than 500 ppm.

15. The ethylene cyanohydrin of claim 11, having an APHA color value (Pt/Co) of less than 5.

16. The process according to claim 3, wherein the at least one titanium alkoxide is Ti(OMe.sub.4), Ti(OEt.sub.4), Ti(O/Pr.sub.4), or Ti(OBu.sub.4).

Description

[0062] In summary, continuous distillation of crude ethylene cyanohydrin did not lead to a high pure ethylene cyanohydrin suitable for further reactions in biochemical applications.

[0063] FIG. 1 shows the ethylene glycol content in the sump.

[0064] FIG. 2 shows the ethylene cyanohydrin content in the sump.

COLUMN CHROMATOGRAPHIC PURIFICATION

[0065] Column chromatography is known in the art as method to purify chemical substances or to separate chemicals from each other.

[0066] Column chromatographic purification of large amounts of liquids (>>100 tons) is uneconomic compared to methods such as distillation. However, chromatographic purification of ethylene cyanohydrin was attempted.

[0067] Aluminum oxide: A column was charged with aluminium oxide (90). The column was charged with ethylene cyanohydrin using a feed pump (flow rate 2 mL/min, dwell time 5 minutes, 25 C.). 650 g crude ethylene cyanohydrin were chromatographed and 16 fractions (each roughly 40 g) were collected and analyzed.

TABLE-US-00008 Ethylene Ethylene glycol Water Colour cyanohydrin [%] [wt. %] [ppm] [APHA] Starting 99.47 0.26 294 115 Material Fraction 4 99.36 0.27 468 125 Fraction 7 99.40 0.27 436 122 Fraction 10 99.40 0.28 431 121 Fraction 13 99.42 0.28 484 120 Fraction 16 99.42 0.28 423 119

[0068] Discussion: Via column chromatography, an effective purification of ethylene cyanohydrin was not possible under applied conditions. In all fractions collected, increased water contents as well as an increased color value were observed. Additionally, no effect on the ethylene cyanohydrin and ethylene glycol content was observed.

[0069] Tonsil 312 FF: A column was charged with Tonsil 312 FF. The column was charged with ethylene cyanohydrin using a feed pump (flow rate 2 mL/min, dwell time 3.8 minutes, 25 C.).

[0070] Discussion: The column filling compressed/condensed so that no eluate could be obtained. Thus, chromatographic purification of ethylene cyanohydrin using clays as absorbents is not possible.

[0071] Molecular sieves (3 ): A column was charged molecular sieves (3 ). The column was charged with ethylene cyanohydrin using a feed pump (flow rate 2 mL/min, dwell time 4.7 minutes, 25 C.). 660 g crude ethylene cyanohydrin were chromatographed and 16 fractions (each roughly 40 g) were collected and analyzed.

TABLE-US-00009 Ethylene Ethylene glycol Water Colour cyanohydrin [%] [wt. %] [ppm] [APHA] Starting 99.47 0.26 294 115 Material Fraction 4 99.35 0.28 422 105 Fraction 7 99.42 0.27 522 108 Fraction 10 99.39 0.27 508 110 Fraction 13 99.39 0.28 521 110 Fraction 16 99.40 0.28 549 112

[0072] Discussion: Via column chromatography, an effective purification of ethylene cyanohydrin was not possible under applied conditions. In all fractions collected, increased water contents were observed, while the color value only slightly decreased. Additionally, no effect on the ethylene cyanohydrin and ethylene glycol content was observed. Additionally, the formation of acrylonitrile was observed.

[0073] Molecular sieves (4 ): A column was charged molecular sieves (4 ). The column was charged with ethylene cyanohydrin using a feed pump (flow rate 2 mL/min, dwell time 5.3 minutes, 25 C.). 655 g crude ethylene cyanohydrin were chromatographed and 16 fractions (each roughly 40 g) were collected and analyzed.

TABLE-US-00010 Ethylene Ethylene glycol Water Colour cyanohydrin [%] [wt. %] [ppm] [APHA] Starting 99.47 0.26 294 115 Material Fraction 4 99.28 0.28 436 108 Fraction 7 99.38 0.29 507 111 Fraction 10 99.39 0.28 521 114 Fraction 13 99.32 0.29 496 115 Fraction 16 99.36 0.28 553 113

[0074] Discussion: Via column chromatography, an effective purification of ethylene cyanohydrin was not possible under applied conditions. In all fractions collected, increased water contents were observed, while the color value only slightly decreased. Additionally, no effect on the ethylene cyanohydrin and ethylene glycol content was observed. Additionally, the formation of acrylonitrile was observed.

[0075] Molecular sieves (13): A column was charged molecular sieves (13). The column was charged with ethylene cyanohydrin using a feed pump (flow rate 2 mL/min, dwell time 5.2 minutes, 25 C.). 661 g crude ethylene cyanohydrin were chromatographed and 16 fractions (each roughly 40 g) were collected and analyzed.

TABLE-US-00011 Ethylene Ethylene glycol Water Colour cyanohydrin [%] [wt. %] [ppm] [APHA] Starting 99.47 0.26 294 115 Material Fraction 4 99.31 0.27 596 101 Fraction 7 99.36 0.28 600 105 Fraction 10 99.38 0.27 585 108 Fraction 13 99.35 0.27 605 109 Fraction 16 97.93 0.28 635 110

[0076] Discussion: Via column chromatography, an effective purification of ethylene cyanohydrin was not possible under applied conditions. In all fractions collected, increased water contents were observed, while the color value only slightly decreased. Additionally, no effect on the ethylene cyanohydrin and ethylene glycol content was observed. Additionally, the formation of acrylonitrile was observed.

[0077] Activated carbon (Epibon Y 1240 spezial (Donau Carbon)): A column was charged activated carbon. The column was charged with ethylene cyanohydrin using a feed pump (flow rate 2 mL/min, dwell time 5.4 minutes, 25 C.). 662 g crude ethylene cyanohydrin were chromatographed and 16 fractions (each roughly 40 g) were collected and analyzed.

TABLE-US-00012 Ethylene Ethylene glycol Water Colour cyanohydrin [%] [wt. %] [ppm] [APHA] Starting 99.47 0.26 294 115 Material Fraction 4 99.33 0.28 506 71 Fraction 7 99.35 0.28 502 82 Fraction 10 99.37 0.29 500 90 Fraction 13 99.40 0.28 573 94 Fraction 16 97.36 0.28 586 95

[0078] Discussion: Via column chromatography, an effective purification of ethylene cyanohydrin was not possible under applied conditions. In all fractions collected, increased water contents were observed, while the color value only slightly decreased, and only initially. Additionally, no effect on the ethylene cyanohydrin and ethylene glycol content was observed.

[0079] Silica gel (Silicagel 60, 0.060-0.2 nm): A column was charged silica gel. The column was charged with ethylene cyanohydrin using a feed pump (flow rate 2 mL/min, dwell time 3.8 minutes, 25 C.). 655 g crude ethylene cyanohydrin were chromatographed and 16 fractions (each roughly 40 g) were collected and analyzed.

TABLE-US-00013 Ethylene Ethylene glycol Water Colour cyanohydrin [%] [wt. %] [ppm] [APHA] Starting 99.47 0.26 294 115 Material Fraction 4 99.37 0.28 531 115 Fraction 7 99.38 0.28 547 121 Fraction 10 99.42 0.28 593 123 Fraction 13 99.40 0.28 646 124 Fraction 16 97.36 0.28 688 124

[0080] Discussion: Via column chromatography, an effective purification of ethylene cyanohydrin was not possible under applied conditions. In all fractions collected, increased water contents were observed, while the color value only slightly decreased, and only initially. Additionally, no effect on the ethylene cyanohydrin and ethylene glycol content was observed. Additionally, the formation of acrylonitrile was observed.

Recrystallisation

[0081] Recrystallisation as a method to purify substances is known in the art. However, recrystallisation of liquid ethylene cyanohydrin (mp: 46 C.) in order to purify the substance is not a viable process for obvious reasons.

EXAMPLES ACCORDING TO THE PRESENT INVENTION

Purification of ECH by Addition of Titanium(IV) Alkoxides

[0082] Esters of orthotitanic acid H.sub.4TiO.sub.4, such as Ti(OR.sub.4) (R=Me, Et, iPr, Bu, 2-Ethylhexyl, neopentyl etc.) are stirred with ethylene cyanohydrin for two hours at ambient conditions.

Example 1a

[0083] A 100 g industrial grade ethylene cyanohydrin sample was mixed with Ti(O/Pr).sub.4 (5 g, 5 wt.-%) and stirred for two hours at 25 C.

TABLE-US-00014 Prior to Ti(OiPr).sub.4 After Ti(OiPr).sub.4 Reduction addition addition (%) Water (ppm, Karl- 500 260 48.0 Fischer) Ethylene glycol (%, GC) 0.30 0.096 68.0

Example 1b

[0084] A 100 g industrial grade ethylene cyanohydrin sample was mixed with Ti(OMe).sub.4 (5 g, 5 wt.-%) and stirred for three hours at 50 C.

TABLE-US-00015 Prior to Ti(OMe).sub.4 After Ti(OMe).sub.4 Reduction addition addition (%) Ethylene glycol (%, GC) 0.30 0.082 72.6

Example 2

[0085] A 20 g industrial grade ethylene cyanohydrin sample was mixed with Ti(O/Pr).sub.4 (2 g, 10 wt.-%) and stirred for 18 hours at 25 C.

TABLE-US-00016 Prior to Ti(OiPr).sub.4 After Ti(OiPr).sub.4 Reduction addition addition (%) Water (ppm, Karl- 500 330 34.0 Fischer) Ethylene glycol 0.30 0.029 90.3 (%, GC)

Example 3

[0086] A 537 g industrial grade ethylene cyanohydrin sample was mixed with Ti(O/Pr).sub.4 (50 g, 10 wt.-%) and stirred for 18 hours at 25 C. Subsequently, the mixture was evaporated using a rotary evaporator. First, at temperatures between 25 C. and 150 C. and at a pressure range between 20 mbar and 60 mbar, a foreshot is collected (15 wt. %). At 150 C. at a pressure range between 10 mbar and 20 mbar, the main fraction is collected (65 wt. %). The residue (20 wt. %) is kept.

TABLE-US-00017 After Reduction After After distillation: (%) or Ti(OiPr).sub.4 distillation: Main Enrichment Initial addition Foreshot fraction (%) Water 300 430 2600 210 30 (ppm, Karl- Fischer) Ethylene 0.30 0.045 0.014 0.027 91.0 glycol (%, GC) Ethylene 99.2 85.75 36.84 99.50 +0.30 cyanohydrin (%, GC)

Example 4

[0087] A 516.5 g industrial grade ethylene cyanohydrin sample was mixed with Ti(O/Pr).sub.4 (51.7 g, 10 wt.-%), heated to 50 C. and stirred for 4 h-20 h. Subsequently, the mixture is fractionally distilled at elevated temperature (50 C. to 140 C., mostly between 90 C. and 130 C.) under vacuum (500 mbar to 1 mbar, mostly between 20 mbar and 5 mbar). The overall distillation yield of ethylene cyanohydrin is >90 C., typically >95%.

[0088] In order to ensure long-term stability of the distillate, the pH value of the product must be acidic and therefore below 7.

TABLE-US-00018 After distillation: Reduction (%) or Initial Relevant fraction Enrichment (%) Water 423 416 2 (ppm, Karl-Fischer) Ethylene glycol (%, GC) 0.34 <0.01 >>95.0 Ethylene cyanohydrin 99.39 99.60 +0.22 (%, GC) Color value (APHA, Pt/Co) 88 <5 >>90.0

[0089] In contrast to all previous attempts, ethylene cyanohydrin was obtained with decreased ethylene glycol and water content, while coincidently increasing the ethylene cyanohydrin content and decreasing the colour value.