Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D201/00—Preparation, separation, purification or stabilisation of unsubstituted lactams
  • C07D201/02—Preparation of lactams
  • C07D201/10—Preparation of lactams from cycloaliphatic compounds by simultaneous nitrosylation and rearrangement
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C249/00—Preparation of compounds containing nitrogen atoms doubly-bound to a carbon skeleton
  • C07C249/04—Preparation of compounds containing nitrogen atoms doubly-bound to a carbon skeleton of oximes
  • C07C249/06—Preparation of compounds containing nitrogen atoms doubly-bound to a carbon skeleton of oximes by nitrosation of hydrocarbons or substituted hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D201/00—Preparation, separation, purification or stabilisation of unsubstituted lactams
  • C07D201/02—Preparation of lactams
  • C07D201/04—Preparation of lactams from or via oximes by Beckmann rearrangement
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D225/00—Heterocyclic compounds containing rings of more than seven members having one nitrogen atom as the only ring hetero atom
  • C07D225/02—Heterocyclic compounds containing rings of more than seven members having one nitrogen atom as the only ring hetero atom not condensed with other rings
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D227/00—Heterocyclic compounds containing rings having one nitrogen atom as the only ring hetero atom, according to more than one of groups C07D203/00 - C07D225/00
  • C07D227/02—Heterocyclic compounds containing rings having one nitrogen atom as the only ring hetero atom, according to more than one of groups C07D203/00 - C07D225/00 with only hydrogen or carbon atoms directly attached to the ring nitrogen atom
  • C07D227/06—Heterocyclic compounds containing rings having one nitrogen atom as the only ring hetero atom, according to more than one of groups C07D203/00 - C07D225/00 with only hydrogen or carbon atoms directly attached to the ring nitrogen atom with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
  • C07D227/08—Oxygen atoms
  • C07D227/087—One doubly-bound oxygen atom in position 2, e.g. lactams
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2601/00—Systems containing only non-condensed rings
  • C07C2601/18—Systems containing only non-condensed rings with a ring being at least seven-membered
  • C07C2601/20—Systems containing only non-condensed rings with a ring being at least seven-membered the ring being twelve-membered

Definitions

• the present invention relates to a process for preparing lactams, comprising, in particular, a step of photonitrosation of cycloalkanes in the presence of light-emitting diodes, referred to as LEDs in the rest of the text, followed by a Beckmann rearrangement step carried out in a microreactor, preferably in a glass microreactor.
• lactams The industrial usefulness of lactams is known.
• caprolactam and lauryllactam are precursors of polyamides 6 and 12, respectively.
• a process for synthesizing a lactam from a cycloalkane can successively implement the following two reaction steps:
• the process described above comprising a photonitrosation step is more rapid, but has drawbacks.
• the photonitrosation step is particularly expensive.
• this photonitrosation step is not very selective and generates from 5% to 10% of chlorinated derivatives, in particular chlorooxime hydrochlorides, which are extracted by the sulfuric acid together with the desired oxime hydrochloride, and also 5% to 10% of other impurities.
• Such chlorinated derivatives are converted—reactions subsequently referred to as dechlorination reactions—during the second reaction step relating to the Beckmann rearrangement, which decreases the yield of this rearrangement.
• dechlorination is intended to mean any chemical reaction which makes it possible to eliminate the chlorine atom(s) bonded to a carbon backbone.
• Beckmann rearrangement reaction which is generally carried out in concentrated sulfuric acid at temperatures above 100° C., is extremely exothermic.
• patent WO0174758 describes the use of a microreactor for the Beckmann rearrangement of acetophenone oxime (free base); in this case, there are no dechlorination reactions to be carried out simultaneously with the Beckmann rearrangement, and it is therefore easy to optimize the reaction yield.
• the present invention relates to a process for preparing lactams, in which a photonitrosation of a cycloalkane is carried out using nitrosyl chloride (NOCl), this photonitrosation being carried out by means of LEDs emitting a monochromatic light.
• NOCl nitrosyl chloride
• the combination of several LEDs of various wavelengths is not excluded in the context of the invention, provided that each of the LEDs has a monochromatic emission spectrum.
• LEDs have many advantages; in particular, said use is less expensive than the use of mercury or sodium lamps. This is because LEDs have a longer lifetime than the lifetime of these lamps and require less cooling and energy consumption.
• LEDs do not contain any mercury, which is an extremely toxic product, the use and the complex recycling of which further increases the cost of use.
• LEDs also have the advantage of being a source of monochromatic light, with a relatively narrow emission spectrum, thereby making it possible to improve, surprisingly, the selectivity of the photonitrosation reaction.
• LEDs having a wavelength of 590 nm makes it possible to increase the selectivity for the photonitrosation reaction by 1 to 2%.
• body of the microreactor is intended to mean the part of the reactor which is in contact with the reaction medium, of the photonitrosation step and/or of the Beckmann rearrangement step.
• the invention also relates to a process for preparing lactams, comprising a step of Beckmann rearrangement of an oxime hydrochloride generated during a prior photonitrosation of a cycloalkane and of simultaneous dechlorination, subsequently denoted Beckmann rearrangement/dechlorination, in which a microreactor, the body of which comprises tantalum, a fluoropolymer, a glass steel or glass, is used to carry out this Beckmann rearrangement/dechlorination.
• the dechlorination yield and the Beckmann rearrangement yield are simultaneously improved, independently of the conditions for carrying out the prior cycloalkane photonitrosation step, whether said conditions use LEDs or mercury or sodium lamps of the prior art.
• microreactor makes it possible to provide optimum safety conditions owing to the small volumes of reactants used and to the excellent control of the exothermicity of the reaction.
• a microreactor made of glass which is less expensive.
• a process for preparing lactams in accordance with the invention comprises the use of LEDs for carrying out the photonitrosation of a cycloalkane, followed by a Beckmann rearrangement/dechlorination step carried out in a microreactor, preferably in a glass microreactor.
• microreactor will subsequently be used for any assembly of microstructured reactors mounted in series or in parallel, and the term “micro structured reactors” or simply “microstructure” will subsequently be used for any chemical reactor, at least one of the characteristic dimensions of which is between 1 micron and 15 millimeters and which is characterized by:
• the LEDs have a size and a power which allow them to be used in a microreactor for increasing the selectivity of reactions.
• the LEDs used in this embodiment have an electric power of greater than approximately 1 Watt and are characterized by a luminous efficacy of greater than 10 lumens/W.
• LEDs are available from many suppliers, such as Philips Lurnileds (Luxeon® range, for example), Cree Inc. or Nichia Corporation.
• microreactor allows homogeneous stirring of the reactive medium and provides, in particular, better transfer of the oxime hydrochloride from the organic phase to the sulfuric acid phase.
• At least one of the two steps, on the one hand photonitrosation and, on the other hand, Beckmann rearrangement/dechlorination, is carried out in such a microreactor.
• each of the two reaction steps on the one hand photonitrosation and, on the other hand, Beckmann rearrangement/dechlorination, is carried out in such a microreactor.
• the photonitrosation of a cycloalkane is carried out using nitrosyl chloride (NOCl).
• NOCl nitrosyl chloride
• This photonitrosation is carried out in an organic solvent/sulfuric acid two-phase medium under temperature and concentration conditions well known to those skilled in the art, such as those described, for example, in document EP 0 993 438.
• An oxime is thus generated in an organic phase, this oxime being subsequently extracted in the form of oxime hydrochloride by the sulfuric acid phase.
• the cycloalkane is cyclododecane; cyclododecanone oxime hydrochloride is then obtained by photonitrosation, according to the reaction:
• the source of photons (hv) consists of LEDs which emit monochromatically, i.e. mainly according to a wavelength range or spectrum which is significantly narrower than the emission range of mercury or sodium lamps, typically about 15 to 30 nm.
• this LED emission spectrum is characterized by an average wavelength having a value which is typically in a range of from 550 to 650 rim in the case of the photonitrosation carried out in accordance with the invention.
• an average wavelength value may be from 585 to 595 nm.
• the use of a microreactor allows better spatial distribution of the photons emitted by the LEDs in the reaction medium, which is an advantage for a photochemical reaction such as photonitrosation.
• a Beckmann rearrangement/dechlorination of the oxime hydrochloride resulting from the first, photonitrosation step is carried out in a concentrated sulfuric acid medium.
• microreactors for the Beckmann rearrangement/dechlorination step allows a surprising improvement in both the yield from dechlorination and the yield from Beckmann rearrangement per se, by virtue of the precise control of the temperatures and the residence times, which makes it possible to significantly reduce the side reactions (hydrolysis of the oxime hydrochloride and of the lactam).
• Beckmann rearrangement being carried out at temperatures of between 100 and 160° C. and residence times of between 2 seconds and 10 minutes according to the number of reactors combined; the second, corresponding in the majority to the dechlorination reactions, being carried out at temperatures of between 160 and 240° C. and residence times of between 2 seconds and 8 minutes according to the number of microreactors combined.
• microreactors markedly improves the safety of the process owing to the small volumes used and to the particularly precise control of the exothermicity.
• the microreactors used can be in the form of a plate of which the surface area is between 100 and 2500 cm 2 ; they have channels of which the diameter is between 50 microns and 10 mm and a system of heating by means of a heat-transfer fluid which makes it possible to achieve temperatures that can reach 250° C.
• All types of glasses can be used to manufacture these microreactors, such as borosilicate glasses (Pyrex®, for example), soda-lime glasses, lead glasses, silica glasses or glass-ceramics.
• borosilicate glasses Pyrex®, for example
• soda-lime glasses soda-lime glasses
• lead glasses lead glasses
• silica glasses glass-ceramics.
• 3806 g of a solution containing 32% by mass of cyclododecane in carbon tetrachloride and 200 g of sulfuric acid at 90% are introduced, with stirring, into a two-liter reactor equipped at its center with a bundle of 80 Luxeon LXML-PL01-0030 LEDs from the company Philips Lumileds, each supplying 30 lumens (for a current of 350 mA) and emitting a monochromatic light centered at 590 nm, the lamps are turned on, and then 10 l/h of anhydrous hydrochloric acid gas and 10 l/h of nitrosyl chloride are introduced continuously for 3 h, while cooling the reaction medium such that the temperature does not exceed 25° C.
• the selectivity of the reaction expressed by the ratio of the percentage of cyclododecanone oxime to the sum of the percentage of cyclododecanone oxime and of by-products of the reaction, assayed by HPLC in the sulfuric acid phase, is 89%, and therefore greater than that observed when using the mercury-vapor or sodium-vapor lamps of the prior art.
• Lactam 30.2% (by mass).
• the chlorine percentages in the solid lactams and oximes obtained by precipitation and washing of the sulfuric solutions of oxime and of lactam are, respectively, 2.18% and 0.65%; the dechlorination yield is therefore 70%.
• the chlorine percentages in the solid lactams and oximes obtained by precipitation and washing of the sulfuric solutions of oxime and of lactam are, respectively, 2.62% and 0.48%; the dechlorination yield is therefore 81.7%.
• microreactors therefore shows that, compared with the prior art, an improvement in the Beckmann rearrangement yield (95.1% compared with 90% in the prior art), for a dechlorination yield of 70%, or an improvement in the dechlorination (81.7% compared with 70% in the prior art), for a Beckmann rearrangement yield of 91.3%, are observed.

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• 2008
  • 2008-05-26 FR FR0853419A patent/FR2931478B1/fr active Active
• 2009
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