ES2594501B2 - New E-caprolactam synthesis procedure - Google Patents

Abstract

The present invention relates to obtaining the {ep} -caprolactam by treating cyclohexanone oxime with salts derived from the guanidinium cation, and in particular with cyanoguanidinium tosylate ([CNG] [TsO]). This salt is also the subject of the invention of the present application. The {ep} -caprolactam is the direct precursor of the polyamide fiber called "nylon-6", becoming said fiber by a polymerization reaction.

Description

New E-caprolactam synthesis procedure

SECTOR OF THE TECHNIQUE

The present invention belongs to the synthetic fiber production sector, specifically nylon 6.

Nylon-6 is a polyamide fiber that offers particular and excellent properties for application in the textile industry, such as high strength-to-weight ratio, high flexibility, chemical and thermal stability, durability and abrasion resistance. The main object of the present invention refers in particular to a process for obtaining E-caprolactam, the industrial precursor of nylon-6.

BACKGROUND OF THE INVENTION

The t-caprolactam is a laclama that by means of a chemical polycondensation reaction is transformed into the polyamide fiber called "nylon ~".

The industrial procedure that is commonly used to obtain (caprolactam is Beckmann's transposition of cyclohexanone oxime, a reaction that requires high temperatures (130 OC) and high amounts of Bronsted acids, such as H, S04 or SOCI, (G. Dahlhoff et al. 2001, Catal. Rev. 43, p. 381) The use of excessive amounts of these reagents, the formation of a large number of secondary products and the corrosion problems they cause lead to serious problems. from an environmental point of view and production costs increase considerably.

eS Transposi <: Betkmann ion

HO

•

e..caprolactam

Or, cyclobcx8oone oma

Therefore, in order to be able to avoid all these inconveniences, work has been described in which this reaction is carried out by applying milder alternative methods, both in the vapor phase and in solvents and organic liquids.

In the vapor phase, good results have been obtained using solid catalysts (

Takahashi et al. 2004, Appl. Catal. A, 262, p. 137; M.J. Climent et al. 2005, J. Mol. Catal. 233, payment 308; M. Anilkumar et al. 2015, Appl. Catal. B, 165, p. 87). Without

However, these procedures require the use of very high temperatures (25010 300 OC), which results in a rapid deactivation of the catalyst and a high energy consumption.

Beckmann's transposition of cyclohexanone oxime has been studied

also in supercritical water (M. Boero et al. 2004, J. Am. Chem. Soco 126, p.

15 6280). obtaining good results in the selectivity of the reaction, but the conversion of the cyclohexanone oxime is very low (30%), so the method is not useful on an industrial scale.

In the liquid phase, the reaction has been described using organic solvents and different catalysts, such as sulfamic acid, antimony salts, oxalic acid, acid

metabolic or chlorosulfonic acid (D. Li et al. 2005, Tetrahedron Lett. 46, p. 671; J. Zhang et al. 2013, Ind. Eng. Chem. Res. 52, p. 6377), with good results in

conversion and selectivity of the reaction. However, the inevitable neutralization of acids and the consequent salt formation, make it difficult to isolate the (

25 caprolactam, decreasing the yield of the reaction. Organocatalysts such as 2,4,6-trichloro-1, 3,5-triazine have also been used (S. Deshpande et al. 2014, Inl. J. Res. Chem. Environ. 4, p. 93). with good conversion and selectivity results. but difficulties in separating the reaction product and the need to reactivate the catalyst, reduce its industrial implementation pathways.

Beckmann's transposition of cyclohexanone oxime has also been described using simple ionic liquids in the presence of Lewis acids (RX. Ren al.

2001, Telrahedron Lel!, 42, p. 8441; J. Peng al. 2001, Telrahedron Lel !. 42, p. 403; S. Guo al. 2005, Calal. Commun. 6, p. 225; K. Elango the al. 2007, Telrahedron Lel !. 48, p. 9059; A. licmanis al. 2009, Calal. Commun. 10, p. 614; X. lhang el al. 2015, Chem. Commun. 51, p. 1930), of acyl or sullonyl chlorides (P. Hong-Jun al. 2009, Telrahedron 65, p. 7790; Palenle CN 1919833 A 20070228; N. An el al. 2013, J. Org. Chem. 78, p. 4297) or organocalalizers (A.

Maia the al. 2012, Telrahedron 68, p. 1947), or using Ionic liquids

functionalized functions as solvents / calalizers (l. Du el al. 2005, J. Mol. Calal. 237, p. 80; J. Gui el al. 2004, Telrahedron Lel !. 45, p. 2681; Palenle WO 2008 / 145312 A1; S. Guo al. 2006, Green Chem. 8, p. 296); Palenle CN 1919834 A 20070228; D. Mao al. 2014, RSC Adv. 4, p. 15635; R. Kore al. 2013, J. Mol.

Catalysis A: Chem. 376, p. 90). However, to obtain good yields in the reaction, ionic liquids require anhydrous reaction conditions in an inert atmosphere and often present serious difficulties when extracting the (

caprolactam of the reaction medium, and therefore in the reuse of the medium of

reaction.

The reaction in the presence of 105yl chloride and a guanidinium-derived salt closely related to ionic liquids has also been described (M. Vilas et al. 2010, Tetrahedron Lel !. 51, p. 4125; Patent ES2359819). This procedure allows the

extraction of pure E-caprolactam, with good performance and using mild conditions (60 OC). Although this procedure improves the previous ones, it requires the use of tosyl chloride as a reaction promoter and large amounts of traditional volatile pollutant solvents; In addition, it results in the formation of p-toluenesulfonic acid as an unwanted by-product.

Although numerous procedures have been developed for the transformation of cyclohexanone oxime into E-caprolactam, to date, mild industrial reaction conditions that allow a clean and simple extraction of E-caprolactam have not yet been achieved. In the present invention a new method of preparing E-caprolaclam is described by the transposition of Beckman n of the cyclohexanone oxime, using as promoter of the

reaction only a new salt, N-cyanoguanidinium tosylate ([CNGJ [Cough]) and water (non-polluting solvent and low price) as reaction medium. The reaction temperature remains mild (60 OC) and the new salt [CNG) fTos). It can be recovered and reused. No secondary product is obtained. The new salt [CNG) [Cough] is very easy to prepare and its cost is not high. All these advantages make its industrial application feasible.

EXPLANATION OF THE INVENTION

The present invention is a process for obtaining E-caprolactam by treating cyclohexanone oxime with a salt derived from the guanidinium cation, meaning "derivative salt" - all those structural derivatives thereof, which maintain or enhance their functionality as reaction catalyst.

A preferred embodiment of the present invention is a process for obtaining e: -caprolactam comprising reacting the oxime of cyclohexanone with N-cyanoguanidinium tosylate ([CNG] [Cough]) in a protic or non-protic solvent medium, E-caprolactam isolation from the reaction medium and salt recovery.

A preferred embodiment of the invention is that the non-protic solvent medium is selected from acetone and dichloromethane, or mixtures thereof, and a more preferred embodiment as a medium is a practical solvent that is water.

The process of the present invention consists in obtaining Ecaprolactam by means of Beckmann Transposition, by treating cyclohexanone oxime using as a catalyst a guanidinium cation salt, in particular a new salt prepared by the inventor: N tosylate -cyanoguanidinium ([CNG] [OTs]).

N-cyanotetramethylguanidinium tosylate structure

This procedure is viable at very mild reaction temperatures (60 ° C) and does not require the use of any other catalyst. The catalyst used, the

,

r

[CNG] [TsO), is economical and non-corrosive, and can also be recovered and

reused E-caprolactam is obtained pure and with high performance. The middle of,

, The reaction used is water, economic solvent and non-polluting.

, l ·

,

,

.

I

¡:

l '

"

.

i

':

[CNGIIOTs) H20, 60 ° C

Another embodiment of the invention is that the reaction temperature is between 20 and 200 ° C, preferably between 20 and 100 ° C, and more preferably 60 ° C.

10 E-caprolactam. reaction product of the invention. It is easily insulated. It can be isolated by liquid-liquid extraction using a suitable slightly polar solvent, for example didoromelan or by sublimation. So another embodiment of the invention is that the final extraction of the E-caprolactam is

15 Perform conventionally by liquid-liquid extraction using slightly polar solvents, or by sublimation.

A very preferred embodiment of the present invention is Ncianoguanidinium tosylate salt ([CNG] [TsO]), or its derivatives. A more preferred embodiment is the

The use of said salt as a catalyst and a more preferred embodiment is its use as a catalyst in the synthesis reaction of E-caprolactam.

Thus, the most preferred embodiment of the present invention comprises the following steps:

25 - react the cyclohexanone oxime with N-cyanoguanidinium cough ([CNG) [TsO)) as a catalyst in H, O, at 60 "C, - the removal of H20 in a rotary evaporator and subsequent separation of said catalyst from N-cyanoguanidinium tosylate ([CNGJ [TsO)) by filtration, and -isolation of E-caprolactam by sublimation or liquid-liquid extraction with

30 CH, Ct.

The process of the invention has many advantages over the previously described procedures, both economically and environmentally. The use of highly toxic and corrosive Bronsted acids is avoided. The use of high temperatures, which involve high energy consumption, is also avoided. The solvent used, H20, is the optimal solvent due to its low cost and non-polluting properties. The only catalyst used, Ncianoguanidinium tosylalo ([CNG) [TsO)) is an easy-to-prepare, low-cost, non-corrosive reagent, and can be recovered for later reuse. No unwanted by-products are formed. E-caprolactam is obtained very pure and with good performance.

The process of the invention thus presents numerous technological, economic and environmental advantages over the current procedures of the technique, giving it inventive activity.

With the intention of showing the present invention in an illustrative manner but in no way limiting, the following examples are provided.

EXAMPLES Example 1: Obtaining N-cyanoguanidinium tosuate ([CNG] [TsO]) On a suspension of N-cyanoguanidine (2 g, 23.5 mmol) in acetone (20 ml) was added a solution of p-toluenesulfonic acid monohydrate ( 5 g, 23.5 mmol) in acetone (10 mL) and the resulting mixture was allowed to stir at 1.a for 12 h. The reaction was followed by c.c.f. using a mixture of CH, CI, / CH, OH (9: 1). Then, the white solid formed was filtered under vacuum, washed with cold acetone (5 x 10 ml) and dried under high vacuum for 8 h to give rise to N-cyanoguanidinium tosylate

(5.9 g, 98%). Its structure was confirmed by spectroscopy of lH and 13C, showing the following signals: NMR-'H (D, 0, 400 MHz): 7.53 (d, 2H, J = 7.7 Hz, Ar-2.6), 7.19 (d, 2H, J = 7.7 Hz, Ar-3, 5), 2.22 (s, 3H, Ar-CH,). NMR- "C (D, O, 0, 100.6 MHz): 162.6 (C = N), 142.4, 139.3, 129.3, 125.3, 119.4 (CN),

20.1 (CH,).

Example 2: Obtaining E: -caprolactam On a solution of N-cyanoguanidinium tosylate (117 mg) in H20 (7 ml) 1 equiv. of the cyclohexanone oxime (52 mg). The solution obtained is subjected to magnetic stirring at a Ta of 60 ° C for 6 h, observed by c.c.f.

(AcOEUHex = 3: 1) the formation of a single reaction product and the complete disappearance of the exemp. The solvent is then completely evaporated, dried acetone is added and cooled to -20 ° C for 2 h. The formation of a precipitate corresponding to [CNG] [OTs1, which is separated by vacuum filtration and

5 wash with acetone. The mother liquors are concentrated under reduced pressure by blending a mixture of E-caprolaclam and ICNG resins] IOTs]. The Ecaprolaclam is then isolated by sublimation (90-100 'C, 250 mbar) or H20 is added to the mixture and extracted with CH2CI2. obtaining a reaction yield of 95%.

Claims (11)

one.

Procedure for obtaining E-caprolactam from the cyclohexanone oxime, characterized in that in said process at least one salt derived from the guanidinium cation substituted with functional groups selected from those that exert an electron accept effect, such as the cyano, carbonyl, nitro or halide group.

2.

Process for obtaining E-caprolactam according to claim 1, comprising the following steps: a) reacting the oxime of the cyclohexanone in the presence of said catalyst in a protic or non-protic solvent medium, b) separation of the catalyst, and e) isolation of the E-caprolactam.

3.

Process for obtaining E-caprolactam according to claims 1 or 2, wherein said catalyst is N-cyanoguanidinium tosylate, or its derivatives or mixtures thereof.

Four.

Method of obtaining E-caprolactam according to claims 2 or 3, wherein the solvent medium is water.

5.

Process for obtaining E-caprolactam according to one of claims 2 to 4, wherein the temperature of said reaction in step a) is between 20 and 200 ° C.

6.

Process for obtaining E-caprolactam according to claim 5, wherein said reaction temperature is between 20 and 100 oC.

7.

Procedure for obtaining E-caprolactam according to 6, in which said reaction temperature is 60 oC.

8.

Method of obtaining E-caprolactam according to one of claims 2 to 4, wherein the separation of the catalyst from step b) is carried out by filtration.

9.

Method of obtaining E-caprolactam according to one of claims 2 to 4, wherein the isolation of the E-caprolactam of step e) is carried out by sublimation or liquid-liquid extraction with a medium

5 non-protic solvent. 10. Method of obtaining E.:- caprolactam according to claim 9, wherein said non-practical medium is dichloromelan. 10 11. Use of the salt according to claims 1 and 3, as catalyst. 12. Use of the salt according to claim 11, as catalyst in the synthesis reaction of E-caprolactam.