Rhodia Operations

Rhodia Polyamide Intermediates

Jean-Claude Masson

Philippe Carvin

Hubert Gayet

Corine Cochennec

Jean-Claude Le-Thiesse

Jean-Louis Grieneisen

Olivier Giacomoni

A method for preparing an aromatic pulverulent composition having a melting point Tf, comprising: i) feeding at least two pulverulent elementary solids having organoleptic properties into a mixer, whose chamber has been preheated beforehand to a temperature T lower than Tf, such solids being separately fed into the mixer; ii) mixing the pulverulent elementary solids in the mixer, in the absence of any external liquid phase, at a temperature T lower than Tf, at least one of the pulverulent elementary solids being fed into the mixer at a temperature Ti, such that the mixing occurs under isothermal conditions at a temperature set at such temperature T; and iii) recovering the aromatic pulverulent composition. This method is particularly suitable for preparing a composition essentially including a vanillin and ethylvanillin compound.

Method for preparing an aromatic composition including a compound containing two solids having organoleptic properties

A method for separating and recovering an aromatic aldehyde from a mixture thereof that also contains tar and light and heavy impurities, includes feeding the liquid flow containing this mixture into an evaporator, vaporizing the mixture in order to separate, on the one hand, a gaseous flow containing the aromatic aldehyde, the light impurities, the heavy impurities that can be vaporized at the selected evaporation temperature and pressure and, on the other hand, a liquid flow essentially containing the tar, and recovering the aromatic aldehyde from the separated gaseous flow.

Separation of aromatic aldehydes

The subject of the present invention is a method for preparing pyrocatechol from which the impurities resulting from the method for the preparation thereof have been removed. The method for preparing purified pyrocatechol from a crude pyrocatechol containing essentially pyrocatechol, small amounts of impurities including dihydroxybenzoquinone, and traces of hydroquinone and of phenolic compounds, is characterized in that it comprises at least the following steps: dissolution of the crude pyrocatechol in water, crystallization of the pyrocatechol, separation of the purified pyrocatechol and, optionally, a step of drying the purified pyrocatechol. The method of the invention may include other steps and, depending on the embodiment chosen, that may comprise a different series of steps, it is possible to obtain pyrocatechol with various degrees of purity.

Method for preparing purified pyrocatechol

A process for preparing highly pure hydroquinone freed of the impurities resulting from the production thereof includes at least the following steps: a) the crude hydroquinone in a liquid form and comprising at least resorcin and pyrogallol as impurities is subjected to a controlled cooling ensuring the crystallization of pure hydroquinone, b) the pure hydroquinone crystals are separated from the mother liquors, c) heating and partial melting thereof is next is carried out, d) the purified hydroquinone is then completely melted, and e) the purified hydroquinone is recovered.

Production of highly pure hydroquinone

Hydroquinone devoid of impurities is prepared from a crude hydroquinone essentially containing hydroquinone and small amounts of impurities including at least resorcinol, pyrogallol and traces of pyrocatechol and comprises at least the following steps: dissolving the crude hydroquinone in water, crystallizing the hydroquinone, separating the purified hydroquinone, and, optionally, drying the purified hydroquinone.

Preparation of purified hydroquinone

A process is described for purifying lactams, in particular the lactams obtained by cyclizing hydrolysis of an aminoalkylnitrile, and more particularly to the purification by crystallization of &#x3b5;-caprolactam obtained by cyclizing hydrolysis of aminocapronitrile. This crystallization is carried out on the cyclization reaction medium after hydrogenation, removal of volatile compounds, and treatment with an ion-exchange resin.

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Lyons, France

Jean-Claude Masson