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 cyanobydrin (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, wherein R=C.sub.1-C.sub.20 linear or branched alkyl.

4. The process according to claim 1, wherein the titanium (IV) alkoxide is Ti(OiPr).sub.4.

5. The process according to claim 1, wherein the incubation is performed under stirring at a temperature of 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 25 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 distillation.

11. The process according to claim 3, wherein the at least one titanium (IV) alkoxide is Ti(OMe).sub.4, Ti(OEt).sub.4, Ti(OiPr).sub.4, or Ti(OBu).sub.4.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the ethylene glycol content in the sump.

(2) FIG. 2 shows the ethylene cyanohydrin content in the sump.

DETAILED DESCRIPTION OF THE INVENTION

(3) The invention pertains to new processes for producing and/or purifying ECH comprising incubating an industrial grade ECH product with at least one titanium(IV) alkoxide; and to highly-pure ECH products obtainable by such processes.

(4) Titanium(IV) alkoxides are esters of orthotitanic acid H.sub.4TiO.sub.4.

(5) Suitable titanium(IV) alkoxides for the process according to the invention are e.g. titanium(IV) alkylalkoxides Ti(OR).sub.4 with R=C.sub.1-C.sub.20 linear or branched, consisting of e.g Ti(OMe.sub.4), Ti(OEt.sub.4), Ti(OiPr.sub.4), and Ti(OBu.sub.4). Ti(OiPr.sub.4) is particularly preferred.

(6) Advantageously, the titanium(IV) alkoxide used in the incubation step is present in amounts of between 1 wt. % and 15 wt. %, and preferably between 5 wt % and 10 wt. %.

(7) The incubation of the industrial grade ECH with the at least one titanium(IV) alkoxide can preferably take place upon stirring, with the stirring rate particularly preferably being in the range from 50 to 2000 rpm, very particularly preferably in the range from 100 to 500 rpm.

(8) The incubation temperature may be between 20 C. and 70 C., preferably between 25 C. and 50.

(9) The incubation time depends inter alia on the parameters selected, for example temperature. Generally, the incubation time should be between 0.5 h and 20 h, preferably between 2 h and 18 h. A person skilled in the art can find further information on the reaction times in the examples attached.

(10) The industrial grade ECH may be obtained from the reaction of ethylene oxide with hydrocyanic acid (HCN), or from the (catalytic) addition of water to acrylonitrile.

(11) In order to further increase ECH purity, a distillation step may follow after the incubation with titanium(IV) alkoxide. Distillation can be conducted via multiple techniques, such as using thin-film evaporators, short-poth evaporators, fractional distillation devices with or without columns.

(12) Distillation can be conducted at ambient or elevated temperatures and ambient or reduced pressure, both parameters adjusted to the physical properties of ECH.

(13) With the process of the present invention, ECH can be obtained in a purity of >99% and comprising less than 0.05% of ethylene glycol (EG), preferably comprising less than 0.01% of ethylene glycol (EG). The purity of ethylene cyanohydrin as well as impurities, such as EG content may be measured and quantified via gas chromatography (GC). For example, a gas chromatograph GC6890, 7890 (Agilent) or comparable devices with FID detectors may be used, in combination with quartz capillary columns (DB-FFAP, DB-WAX or other separation phases, 30 m). Helium may used as carrier gas, with injector and detector temperatures of 250 C. Area percent of components are determined (automatically) by area % reporting options of the chromatograph control systems. % are converted to ppm by multiplying with 10000.

(14) In one embodiment of the invention, the ECH has a water content of less than 1000 ppm. A water content of less than 500 ppm is of particular advantage. The water content of ethylene cyanohydrin may be determined via coulometric Karl Fischer titration, or, alternatively, by volumetric titration. A Karl Fischer coulometer (e.g. type 756 from Metrohm) is preferably used together with analytical balances, calibrated syringes and calibrated titration reagents.

(15) Preferably, the ECH has a APHA color value (Pt/Co) of less than 30, preferably less than 5. The color value may be determined photometrically. Therein, the visual comparison with standard color solutions of the platinum-cobalt scale is replaced by measurement of the extinction of the sample at wavelengths 460 and 620 nm. The extinction difference E.sub.480 nmE.sub.620 nmE is linearly related to the color unit of the platinum-cobalt standards. Plotting the color value against E provides a calibration line whose gradient serves as a factor for calculation of the color value, but only on the condition that the colorimetric specification for the sample to be analyzed, i.e. its hue, corresponds largely to the platinum-cobalt scale. A spectrophotometer or filter photometer with filters for the ranges 460 and 620 nm is used with 5 cm and 1 cm cuvettes. Calibration substances are potassium hexachloroplatinate (K.sub.2PtCl.sub.6), Cobalt(II) chloride hexahydrate (CoCl.sub.26H.sub.2O) and conc. hydrochloric acid p.a., 32%. Pt/Co standard solutions are prepared and are measured in 5 cm cuvettes at 460 and 620 nm by means of a spectrophotometer or filter photometer with suitable filters. (Reference cuvette contains demineralized water). The Pt/Co color values and the extinction coefficients established for these (E.sub.460nmE.sub.620nm) show a linear relationship. The gradient of this straight calibration line can be determined graphically or by regression and serves as a basis for calculation of the Pt/Co color value (b and m values).
Pt/Co color value=((E.sub.480nmE.sub.620nm)b)/m
(b=axis intercept, m=gradient)

(16) Synonyms for the platinum-cobalt color value are the APHA and Hazen number.

EXAMPLES

(17) Ethylene cyanohydrin was obtained directly from a production plant and used as received. Samples were analyzed via GC/GC-MS (purity), Karl-Fischer titration (water) and Pt/Co scale (APHA, color). Naturally, analytical data from different ECH production batches vary, which is why ranges are given.

(18) TABLE-US-00001 Ethylene cyanohydrin (%, GC) 98.5-99.5 Water (ppm, Karl-Fischer) 200-1000 Ethylene glycol (%, GC) 0.10-1.00 Color (Pt/Co, APHA) 20-500

Comparative Examples

(19) Attempts to purify ethylene cyanohydrin utilizing common methods known in the art with the requirements of simultaneous reduction of water content, ethylene glycol content, color value and enrichment of ethylene glycol content:

Azeotropic Eistillation with Cosolvents

(20) Removal of water and/or e.g. other polar substances from a reactor via azeotropic distillation is known in the art and was investigated.

(21) Under Dean-Stark conditions, 200 g ethylene cyanohydrin and 250 g toluene were heated to reflux for five hours. Subsequently, the mixture was brought to room temperature and after phase separation, ethylene cyanohydrin was obtained as a yellow liquid.

(22) TABLE-US-00002 Prior to After Reduction (%) or distillation distillation Enrichment (%) Water (ppm, Karl- 480 170 64.6 Fischer) Ethylene glycol (%, 0.265 0.279 +5.28 GC) Color value (APHA, 240 >500 + Pt/Co) >108

(23) Discussion: Via azeotropic distillation with cosolvents, a product is obtained, in which the water content is reduced, while the ethylene glycol is enriched. Simultaneous reduction of water and ethylene glycol content was not achieved. Additionally, the color value increased drastically. Additionally, the co-solvent also has to be distilled of the product.

Absorption

(24) Removal of water and/or e.g. other polar substances from a liquid (or a gas) with porous materials such as molecular sieves is known in the art and was investigated.

(25) 100 g ethylene cyanohydrin was mixed with thoroughly dried molecular sieves (4 , 10-20 wt. %) and left standing/drying for 10 days. Molecular sieve was removed via filtration.

(26) TABLE-US-00003 Prior to After Reduction (%) or absorption absorption Enrichment (%) Ethylene 99.494 99.471 0.024 cyanohydrin (%, GC) Water (ppm, Karl- 210 90 57.15 Fischer) Ethylene glycol (%, 0.27 0.20 25.93 GC) Color value (APHA, 9 22 +144.4 Pt/Co)

(27) Discussion: Via absorption with molecular sieves, the color value of ethylene cyanohydrin increases. The water content is reduced, and also the ethylene glycol content, but to a lesser extent. Simultaneous reduction of water and ethylene glycol content was achieved, but also the ethylene cyanohydrin content was reduced and the color value increased.

(28) Additionally, the formation of acrylonitrile was observed.

(29) Nota bene: Utilization of a larger amount of molecular sieves is not economical, and would not lead to improved purity and color as shown above.

Distillation 1

(30) Distillation as a purification method is known in the art and was investigated.

(31) Distillation was conducted under various conditions, e.g. between 50 C. and 150 C. and 1 mbar up to 500 mbar negative pressure. A representative sample is given below:

(32) 100 g ethylene cyanohydrin was distilled at 130 C.-150 C. at reduced pressure (10 30 mbar). 81 g clear colorless distillate was collected together with 18 g of a yellow-red residue.

(33) TABLE-US-00004 Prior to After Reduction (%) or distillation distillation Enrichment (%) Ethylene 99.278 99.266 0.012 cyanohydrin (%, GC) Water (ppm, Karl- 480 240 50.0 Fischer) Ethylene glycol (%, 0.265 0.411 +55.09 0GC) Color value (APHA, 240 <5 >97 Pt/Co)

(34) Discussion: Via distillation, a clear colorless distillate is obtained, thus effectively reducing the color value of ethylene cyanohydrin (removal of colorants via distillation). The water content was reduced, while ethylene glycol enriched in the distillate. Simultaneous reduction of water and ethylene glycol content was not achieved. Additionally, the ethylene cyanohydrin content was reduced.

Distillation 2

(35) A larger sample ethylene cyanohydrin (1.5 kg) was distilled with a column and 20 theoretical plate numbers. The sample was heated with total reflux first, and subsequently different distillate fractions (reflux ratio 2) were collected and analyzed, with intermediate total reflux between each fraction. The column pressure was set to 250 mbar. With each distillate fraction, one additional sump probe was collected.

(36) Observation: During the heating phase, a distinct color change of the sump is observed (from colorless to brown). With progressing distillation time, the color of the mixture increases. Additionally, an unexpectedly large amount of liquids was collected in the cooling trap (23% of the initially applied mass), which was also biphasic

(37) The mixture was analyzed and the water content was determined (via Karl Fischer method):

(38) TABLE-US-00005 Wt. % Water Mass % Feed 0.025 Trap 1st fraction 37.1 Sump after 1st 0.051 Trap 5th raction 45.0 fraction Sump at end of 1.65 Trap at End 40.0 distillation

(39) Obviously, water is formed during the distillation procedure, which enriches (as a low boiler) at the column head. Due to the good stripping effect of water, a large fraction of liquids is collected in the cooling trap. In order to exclude material incompatibility of the distillation apparatus with ethylene cyanohydrin, feed samples were separately heated in vials (>100 C.). A color change as well as an increasing water content (from 250 ppm to 510 ppm,+104%) is observed, which proves decomposition processes under distillation conditions and excludes material incompatibilities.

(40) Furthermore, the distillate as well as the sump was analyzed via GC and GC-MS. Results indicate the formation of new components during the distillation procedure, as peaks arise which were not observed in the starting material.

(41) TABLE-US-00006 TABLE 2 Portion ethylene cyanohydrin and ethylene glycol in the sump Portion evaporated Ethylene glycol Ethylene cyanohydrin [%] [ppm] [wt. %] Feed 0.00 4583 98.5258 Fraction 1 3.43 478 99.4258 Fraction 2 4.08 240 99.5121 Fraction 3 6.51 117 99.1834 Fraction 4 10.97 45 98.7654 Fraction 5 22.24 20 96.9994

(42) TABLE-US-00007 TABLE 3 Portion ethylene cyanohydrin and ethylene glycol in the distillate Portion evaporated Ethylene glycol Ethylene cyanohydrin [%] [wt. %] [wt. %] Fraction 1 3.43 9.6908 82.2246 Fraction 2 4.08 5.8213 85.8175 Fraction 3 6.51 1.598 89.0743 Fraction 4 10.97 0.3692 89.3493 Fraction 5 22.24 0.0892 89.5579

(43) While the ethylene glycol content in the sump decreases (and enriches in the distillate), the ethylene cyanohydrin content decreases as more side reactions take place and side products form. Additionally, the color value of the sump constantly increases. A high purity ethylene cyanohydrin as distillation residue, obtained via evaporation of contaminants, is therefore not possible.

(44) Additionally, the distillate obtained under these conditions shows a significantly decreased ethylene cyanohydrin content. It is also contaminated with ethylene glycol and water, which enrich in the gas phase. Also, as water is constantly formed during temperature exposure of the sump, an anhydrous distillate cannot be obtained.

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

(46) FIG. 1 shows the ethylene glycol content in the sump.

(47) FIG. 2 shows the ethylene cyanohydrin content in the sump.

COLUMN CHROMATOGRAPHIC PURIFICATION

(48) Column chromatography is known in the art as method to purify chemical substances or to separate chemicals from each other.

(49) 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.

(50) 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.

(51) 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

(52) 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.

(53) 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.).

(54) 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.

(55) 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.

(56) 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

(57) 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.

(58) 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.

(59) 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

(60) 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.

(61) 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.

(62) 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

(63) 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.

(64) 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.

(65) 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

(66) 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.

(67) 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.

(68) 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

(69) 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.

(70) Recrystallisation

(71) 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

(72) 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

(73) 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.

(74) 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

(75) 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.

(76) 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

(77) 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.

(78) 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

(79) 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.

(80) 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

(81) 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%.

(82) In order to ensure long-term stability of the distillate, the pH value of the product must be acidic and therefore below 7.

(83) 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

(84) 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.