Abstract: Hydroxytyrosol extracted from olives and/or from the solid residues of olives after the extraction of olive oil, by acid hydrolysis and purification on resin columns eluted with water contains hydroxytyrosol and tyrosol, is free from sugars, has a residual content of Benzo[a]pyrene that is less than 2 microg/Kg (weight BaP/weight of extract as dry matter), containing a weight ratio of hydroxytyrosol to hydroxymethylfurfural of between 45:1 and 10000:1, and the content of hydroxytyrosol in the extract is at least 0.5% (w/w) with purity of at least 40% (by HPLC 280 nm).

Abstract: Disclosed is a process for recovering a water-soluble complex mixture of organic compounds from an aqueous stream through extraction and/or through contact of the aqueous stream with a sorbent or sorbents selected from the group consisting of polymeric microreticular sorbent resins, zeolite-based adsorbents, clay-based adsorbents, activated carbon-based sorbents, and mixtures thereof; and including methods to recover the removed organic compounds.

Abstract: 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.

Abstract: A method for cultivating Monarda fistulosa for production of thymoquinone includes planting seeds at rates between about 2.5 and about 5 pounds per acre, preferably about 4 pounds per acre. The heavy rate of planting produces plants bearing oil without weed contamination and reduces herbicide use due to production of natural herbicides by the monarda plants. Seeding and mowing the first season, and harvesting in seasons thereafter reduce costs. The method results in increased production of essential oils including thymoquinone and thymohydroquinone at levels up to about 5% of recovered oils, and which may be distilled from the plant.

Abstract: Novel hydroquinone flakes are prepared from a powder thereof, by, if necessary, melting the hydroquinone powder, depositing the hydroquinone in the liquid state as a film on a support made of a material or coated with a material which conducts heat, solidifying the hydroquinone by adjusting the support to an appropriate temperature, and recovering the solidified product in the form of flakes.

Abstract: A purification method of dihydroxybenzene comprising the following steps, for obtaining purified dihydroxybenzene from crude dihydroxybenzene containing at least isopropenylphenol and hydroxyacetophenone as impurities: first extraction step, distillation step, second extraction step, and recovery step.

Abstract: The present invention is directed to a composition comprising a tris-hydroxyaryl compound having a metal ion impurity content of less than 10 ppm and to a process for the purification of tris-hydroxyaryl compound having a metal ion impurity, comprising at least the following steps: a) conditioning a sulphonic acid group-containing active ion exchanger with a solvent which is suitable for the handling of the tris-hydroxyaryl compounds, b) producing a solution of the tris-hydroxyaryl compounds to be purified in a solvent which is suitable for the handling of the tris-hydroxyaryl compounds, c) contacting the tris-hydroxyaryl compound-containing solution from b) with the conditioned ion exchanger from a), d) separating the tris-hydroxyaryl compound-containing solution from c) from the conditioned ion exchanger, e) removing at least part of the solvent from the solution of the tris-hydroxyaryl compound separated in d) under low temperature stress.

Abstract: In a method of recovering phenol and acetone from a feed stream containing bisphenol-A and isomers thereof, the feed stream is contacted with water and a source of hydroxyl ions under conditions effective to decompose at least part of said bisphenol-A and isomers thereof to phenol and acetone. The conditions include a temperature of about 150° C. to about 300° C., a pressure sufficient to keep the water substantially in the liquid phase at said temperature, and a molar ratio of hydroxyl ions to hydroxyphenyl groups in the residue stream from about 0.3:1 to about 0.9:1.

Abstract: Separation and purification of hydroquinone from crude mixtures thereof essentially containing hydroquinone in combination with very small amounts of impurities including resorcinol and pyrogallol, include a topping distillation allowing the resorcinol to be removed as the distillation top product, and allowing a crude mixture essentially containing hydroquinone and the heavy impurities to be recovered at the column bottom, such mixture then being subjected to a bottoming distillation which allows the pyrogallol to be removed at the column bottom and allows hydroquinone in a purified form to be recovered at the column top.

Abstract: In a method of recovering phenol and acetone from a feed stream containing bisphenol-A and isomers thereof, the feed stream is contacted with water and a source of hydroxyl ions under conditions effective to decompose at least part of said bisphenol-A and isomers thereof to phenol and acetone. The conditions include a temperature of about 150° C. to about 300° C., a pressure sufficient to keep the water substantially in the liquid phase at said temperature, and a molar ratio of hydroxyl ions to hydroxyphenyl groups in the residue stream from about 0.3:1 to about 0.9:1.

Abstract: 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.

Abstract: Hydroxytyrosol is extracted from olives and/or from the solid residues of olives after the extraction of olive oil, by carrying out acid hydrolysis at a temperature within the range of 110° C. to 140° C. and at a pH within the range of 1.0 to 6.0, and by purifying the obtained solution on a column containing acid activated anion exchange resins, and a column containing an adsorbent non-ionic resin; both columns being eluted with water to recover the hydroxytyrosol.

Abstract: 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.

Abstract: The present invention relates to a method for extracting phenolic compounds with low molecular weights from olive fruit water; the invention also relates to compositions enriched with phenolic compounds including at least 40% of dry matter, said dry matter consisting of at least 30% hydroxytyrosol; the invention also relates to a method for drying said compositions by spraying using grape polyphenol extracts as a drying medium as well as to powders titrated with phenolic compounds of olives and grapes obtained after drying.

Abstract: Process for purifying 3,4-dihydroxyphenylglycol (DHPG) from any part of the plant, from the products or by-products derived from olive trees or any other vegetable product of the families Oleaceae, Orobanchaceae, Plantaginaceae, Compositae, Lamiaceae, Acanthaceae and/or Scrophulariaceae, and which comprises 1 or more steps wherein the initial product is introduced into at least one ion-exchange resin column, and in potentially subsequent steps the product eluted in the preceding column is introduced into an ion-exchange resin and/or a non-ionic adsorption resin column. Moreover, it relates to the DHPG extract obtainable by means of the process disclosed and to the applications thereof.

Abstract: A purification method of dihydroxybenzene comprising the following steps, for obtaining purified dihydroxybenzene from crude dihydroxybenzene containing at least isopropenylphenol and hydroxyacetophenone as impurities: first extraction step: water is added to crude dihydroxybenzene to prepare a dihydroxybenzene aqueous solution A, then, the solution is subjected to extraction by allowing it to contact with an extraction solvent (1), to be separated into a first fraction containing dihydroxybenzene, hydroxyacetophenone and water and a second fraction containing isopropenylphenol and the extraction solvent (1), distillation step: the first fraction obtained in the first extraction step is subjected to distillation, to be separated into a third fraction containing water and a fourth fraction containing dihydroxybenzene and hydroxyacetophenone, then, the fourth fraction is subjected to distillation, to be separated into a fifth fraction as purified dihydroxybenzene and a sixth fraction as dihydroxybenzene contain

Abstract: Purified hydroquinone is prepared and formed from raw compounds essentially containing hydroquinone associated with very small quantities of impurities including resorcinol and pyrogallol, and includes a distillation purification step in which the resorcinol and pyrogallol are eliminated, directly followed by a step in which the purified hydroquinone is formed.

Abstract: The invention relates to a process for the preparation of a liquid composition of an ortho-dihydroxybenzyl compound of high purity characterized in that it consists inpurifying the initial ortho-dihydroxybenzyl compound by distillation and recovering the condensed ortho-dihydroxybenzyl compound in an apparatus resistant to corrosion by the latter, and then mixing it with an organic solvent in a storage tank which is lined or made of a material which does not lead to metallic pollution. The invention also relates to a liquid composition of an ortho-dihydroxybenzyl compound of high purity comprising said compound and an organic solvent of said compound obtained according to said process.

Abstract: Disclosed is a method for preparing an alkali metal salt of a hydroxy-substituted hydrocarbon which comprises the steps of (i) contacting in solvent media at least one hydroxy-substituted hydrocarbon with a base comprising an alkali metal cation; and (ii) devolatilizing the solvent media comprising alkali metal salt by adding or spraying the solvent media into a substantially water-immiscible organic solvent, said solvent being at a temperature greater than the boiling point of solvent media at the prevailing pressure. In one embodiment the solvent media comprises water, and optionally at least one water-soluble protic organic solvent.

Abstract: A method for treating tar separated from a liquid containing an aromatic hydroxybenzene obtained by acidolysis of a liquid containing an aromatic hydroperoxide, which comprises dissolving the tar with an alkaline aqueous solution.

Abstract: The present invention provides a production method of a compound of the formula wherein X is chlorine atom, bromine atom or iodine atom, as well as a production method of citalopram and intermediates therefor.

Abstract: A method and installation for separating and purifying a crude mixture containing hydroquinone, resorcinol and possibly tars and/or catechol, comprising the following steps: —a possible distillation stage (I) in order to obtain a catechol head, —the foot (I) or crude mixture undergoes distillation (II) in order to obtain a fraction that is rich in resorcinol, —the foot of (II) undergoes distillation (III) in order to obtain a fraction that is rich in hydroquinone, whereupon said rich fractions are refined (IV or V). Preferably, one or several stages in which tar is removed (I,I?) precede stage (I) or (II).

Abstract: A refined dihydroxyaryl compound, for example, catechol, having a high degree of purity and a very low metal content is produced by evaporating a starting dihydroxyaryl compound in a distillation column, condensing the vapor fraction in a condenser connected to a top outlet of the distillation column, and collecting the condensed fraction from the condenser into a storage tank through a conduit, wherein the condenser and optionally the conduit and/or the storage tank have inside surfaces thereof formed from a metal material containing at least 25% by weight of nickel, and the condensed dihydroxyaryl compound fraction is brought into contact with the specific nickel (25% or more)-containing metal inside surface.

Abstract: A process for producing an aromatic hydroxy compound having hydroxyl group at the para-position with respect to a hydroxy or an alkoxy substituent group present in the aromatic ring at a high yield and at a high selectivity, using a novel and useful hydroxylation catalyst which can afford to introduce hydroxyl group directly into aromatic ring at the para-position with respect to a hydroxy or an alkoxy substituent group, by reacting at least one compound selected from the group consisting of phenols, alkoxybenzenes and derivatives of them with hydrogen peroxide in the presence of the catalyst, wherein the hydroxylation catalyst is constituted of an oleophilized crystalline titanosilicate.

Abstract: A method is disclosed for preparing a fluorogenic phenolic compound with improved optical qualities for use in formulating a substrate solution for assay of peroxidase or peroxide activity. The method involves forming a solution under anoxic conditions which contains the phenolic compound and an aminopolycarboxylic acid or aminopolyphosphonic acid, or salt thereof, metal chelating agent and, while the solution is maintained under anoxic conditions, recovering the compound from the solution in an optically enhanced condition. A composition of matter is also disclosed which includes the fluorogenic phenolic compound in crystal form and a trace quantity of the metal chelating agent.

Abstract: The present invention relates to a method of making purified monotertiarybutyl hydroquinone containing less than 0.2% (wt.) of 2,5 ditertiarybutyl hydroquinone. This method includes heating a composition of monotertiarybutyl hydroquinone and 2,5 ditertiarybutyl hydroquinone in a solvent mixture of a polar solvent and a non-polar solvent. During this step, the non-polar solvent is substantially stripped-off and at least part of the 2,5 ditertiarybutyl hydroquinone is solidified, which is separated from the non-solidified composition. The remaining non-solidified composition and polar solvent are mixed with a non-polar solvent of the same type as was previously stripped-off. The polar solvent, which contains the purified monotertiarybutyl hydroquinone, is separated from the non-polar solvent. This purified monotertiarybutyl hydroquinone is separated the from the polar solvent to produce purified monotertiarybutyl hydroquinone containing less than 0.2% (wt.) of 2,5 ditertiarybutyl hydroquinone.

Abstract: The present invention provides a process for the production of two molecules of 4-aryl-2 butanols having the general formula 1 given below: Wherein R═H or glucose from the leaves of Taxus wallichiana, which comprises: (a) defatting air dried, pulverized leaves with aliphatic hydrocarbon solvents, (b) extracting the defatted leaves with chlorinated solvents and polar solvent successively at room temperature, (b) concentrating the chlorinated solvent soluble faction to a residue and treating the residue with aqueous solution of alkali and extracting with chlorinated solvents, (d) acidifying the alkali layer with mineral acid and extracting with ethyl acetate and concentrating the ethyl acetate phase to give compound of formula 1 where R═H, (e) concentrating the polar solvent fraction from step (b) to a residue and treating the residue with aqueous solution of alkali and extracting with chlorinated solvent, and (f) acidifying the alkali phase with mineral acid and extracting wit

Abstract: A class of asymmetric monobenzoxanthene compounds useful as fluorescent dyes are disclosed having the structure ##STR1## wherein Y.sub.1, and Y.sub.2 are individually hydroxyl, amino, imminium, or oxygen, R.sub.1 -R.sub.8 are hydrogen, fluorine, chlorine, alkyl alkene, alkyne, sulfonate, amino, amido, nitrile, alkoxy, linking group, and combinations thereof, and R.sub.9 is acetylene, alkane, alkene, cyano, substituted phenyl and combinations thereof The invention ftrther includes novel intermediate compounds useful for the synthesis of asymmetric benzoxanthene compounds having the general structure ##STR2## where substituents R.sub.3 -R.sub.7 correspond to like-referenced substituents in the structure of described above, and Y.sub.2 is hydroxyl or amine. In another aspect, the invention includes methods for synthesizing the above dye compounds and intermediates.

Abstract: An extractive distillation process using a high boiling polyol such as glycerol is employed for separating high purity catechol, 3-methylcatechol and 4-methylcatechol from a high boiling, pitch-like dihydric phenol fraction. Fractional distillation first separates an impure overhead mixture of the catechol and 3-methylcatechol and an impure 4-methylcatechol bottoms. The impure overhead is extractively distilled to remove impurities and then extractively distilled again to separate the catechol and 3-methylcatechol. This produces a pure overhead of 3-methylcatechol and a bottoms of catechol and polyol which is distilled to recover the catechol and recycle the polyol. The impure 4-methylcatechol is distilled to remove residual material and then extractively distilled to remove impurities. The resulting mixture of 4-methylcatechol and polyol is distilled to recover the pure 4-methylcatechol and to recycle the polyol.

Abstract: A process for the purification of a crude bisphenol comprises the following steps:(1) preparing a mixture comprising from about 35 to about 70% of a crude bisphenol and from about 65 to about 30% of water, by the total weight of bisphenol and water, without addition of a substantial amount of an organic solvent or an alkaline compound, at a pressure above atmospheric and a temperature above about 100.degree. C.,(2) crystallizing bisphenol at a pressure below atmospheric,(3) separating crystalline bisphenol from the mother liquor,(4) dividing at least a portion of the mother liquor into a bisphenol-rich oil phase and a water-rich phase,(5) preparing a mixture comprising at least a portion of the bisphenol-rich oil phase, water and optionally an additional amount of crude bisphenol at a pressure above atmospheric and a temperature above about 100.degree. C.,(6) cooling the mixture and crystallizing bisphenol; and(7) separating crystalline bisphenol from the mother liquor.

Abstract: A method is provided for depolymerizing scrap aromatic polycarbonate to salvage component monomers by initially effecting aromatic polycarbonate depolymerization by basic phenolysis to produce a mixture having dihydric phenol, and diarylcarbonate. Recovery of the dihydric phenol is effected by distillation of a crystalline dihydric phenol/phenol adduct. Diarylcarbonate is recovered by distillation of the resulting mother liquor after carboxylic acid treatment.

Abstract: The invention relates to a process for obtaining a high purity bisphenol from a post-reaction mixture resulting from the step of synthesis of phenol and acetone in the presence of a strong acid cation exhanger catalyst, by the way of crystallation and separation by distillation followed by recovery of bisphenol-A from the step of thermal catalytic decomposition of by product of the principal process technology in a multistage process.

Abstract: A process is described for the removal of guaiacol from naturally occurring cresylic acid feed by heating the feed with a strong acid, particularly hydrochloric acid or sulfuric acid, to produce a purified cresylic acid product essentially free of guaiacol and other methoxy aromatic compounds without significant loss of cresylic acid product.

Abstract: Acid contaminants leached from acidic ion-exchange resins and carried in process streams with phenol are separated from the phenol by passing the process stream in contact with an anionic exchange resin, whereby the acid contaminants react with and bond to the anionic exchange resin.

Abstract: A process for producing food-grade tertiary-butyl hydroquinone from impure montertiary butyl hydroquinone is provided. Impure monotertiary butyl hydroquinone crystals are agitated at an elevated temperature while in contact with a non-polar solvent under conditions to extract the majority of the impurities followed by separating purified monotertiary butyl hydroquinone crystals from the solvent at a temperature above the crystallization point of the impurities.

Abstract: 2,4-Xylenol can be obtained in high yield and high purity from a crude 2,4-xylenol isomer mixture containing 2,5-xylenol by selectively reacting the 2,5-xylenol with an aldehyde in the presence of an aromatic sulfonic acid, thereby converting the 2,5-xylenol into a xylenol-aldehyde condensate and, subsequently, separating the 2,4-xylenol, e.g., by distillation.

Abstract: This invention comprises a process for separating isomers of dihydroxybenzene (DHB) from a feed mixture comprising at least two of said isomers, which process comprises contacting the mixture at adsorption conditions with an adsorbent comprising a Y type zeolite cation exchanged with a cation in the group Ca, Ba or Li, thereby selectively adsorbing o-DHB (catechol), or K, thereby selectively adsorbing p-DHB (hydroquinone). In the case where all three isomers are present in the feed, a cation from the first group is used, the remainder of the feed mixture is removed from the adsorbent and o-DHB is recovered by desorption at desorption conditions with methanol. P-DHB is recovered from the remainder by adsorption with the same or other adsorbent listed above and desorption at desorption conditions with ethanol.

Abstract: A process for separating higher molecular weight constituents from phenol polymers, wherein the phenol polymer is dissolved in an organic solvent medium, the solution obtained is mixed at room temperature with ammonia or an amine such that there is a stoichiometric deficiency of ammonia or amine, the precipitate is separate, dried, if appropriate, and treated with aqueous acid, and the resulting sediment is filtered off, washed and dried as described. The starting phenol polymer preferably is a condensation product of optionally substituted phenol and formaldehyde. The process yields fractions possessing an increased osmometric molecular weight, a narrower molecular weight distribution range and an increased glass transition temperature.

Abstract: There is disclosed a process for the reduction of the diether impurities formed when a dihydroxy aromatic compound is reacted with an alkylating agent in an alcoholic solvent in the presence of two to three equivalents of base. The diether impurities are removed by removing a quantity of the alcoholic solvent and adding a solvent into which the diether impurities may be extracted.

Abstract: Anhydrous di-(alkali metal) (especially disodium) salts of dihydroxyaromatic compounds such as bisphenol A are prepared by first contacting the solid dihydroxyaromatic compound with an aqueous alkali metal hydroxide solution so as to convert it into the solid di-(alkali metal) salt or hydrate thereof and subsequently separating the solid salt or hydrate from the aqueous system and removing water therefrom, typically by mixing the same with an organic liquid and removing water, including water of hydration, by evaporation. The organic liquid is preferably one such as toluene or o-dichlorobenzene in which water and the anhydrous di-(alkali metal) salt are substantially insoluble. The process may be operated in batch or continuous fashion.

Abstract: 4-Hydroxydiphenyl (mono-OD) and 4,4'-dihydroxydiphenyl (DOD) are obtained simultaneously from a mixture which contains these two substances, if such a mixture is treated with an aqueous alkali, and the resulting solution and the solid phase formed are separated at a temperature from -28.degree. C. to +40.degree. C. and the solution and the solid phase are acidified separately in order to form the free mono-OD and DOD. Mono-OD and DOD can be present in the starting mixture in the free form or in the form of the alkali metal phenolates. After formation of the alkali metal phenolates, where this is required, the aqueous alkali still contains 1-15 mol of alkali metal hydroxide per mol of the diphenyl compounds. The concentration of alkali metal hydroxide should be 4-25% by weight, relative to the amount of water present. In this process, it is also possible to employ industrial mixtures of the alkali melts of the associated diphenyl-sulphonic acids.

Abstract: Polyethylene glycols have been found to be selective solvents for the extraction of phenolic compounds from admixture with hydrocarbons.

Abstract: A method for purifying phloroglucin wherein crude phloroglucin obtained by an acid-decomposition of 1,3,5-triisopropylbenzene trihydroperoxide in the presence of a solvent and removal of the formed acetone and the solvent by evaporation, is extraction-treated within a pH range of 7.5 to 12 in the coexistence of an aqueous alkali liquor of 4 to 25 times by weight based on the crude phloroglucin and an organic solvent of 0.05 to 6 times by weight based on said aqueous alkali liquor selected from ketones and esters which are separable from the aqueous alkali liquor, and after acidifying the separated aqueous alkali extract, the deposited crystal is recrystalized.The phloroglucin is useful as a starting material of medicines and photosensitizers.

Abstract: This invention relates to a process for the selective preparation of ortho-hydroxybenzyl alcohols and, in particular, ortho-hydroxybenzyl alcohol. According to the invention, the reaction of a phenol with an aldehyde in an initially anhydrous medium and in the presence of a catalytic amount of a metal phenate, results in the selective production of ortho-hydroxybenzyl alcohols.

Abstract: A process is disclosed for separating closely-boiling dihydric phenol compounds by treating a mixture of dihydric phenols with a metal halide salt. The metal halide salt preferentially forms a complex with one of the dihydric phenols over other related dihydric phenols in the mixture. The preferentially-formed complex of one of the dihydric phenols may then be isolated from the mixture and the complex decomposed to provide a product substantially enriched in, or substantially entirely composed of, one dihydric phenol. The process is particularly suitable for resolving a mixture comprising hydroquinone and catechol, or a mixture of hydroquinone and resorcinol, or a mixture of homocatechol and hydroquinone, or a mixture of catechol and resorcinol.

Abstract: A process is disclosed for selectively removing catechol from a mixture comprising catechol, 2-methallyloxyphenol, various salts, and by-products by treating the mixture with aqueous base, the aqueous phase being preferably saturated with respect to salts present; the catechol may then be recovered for recycle by acidifying the resulting aqueous phase and extracting the acidified aqueous phase with a suitable organic solvent.

Abstract: A process for the extraction of phenolic compounds from aqueous solutions is disclosed. The process comprises contacting said aqueous solution with an organic solution comprising at least one tertiary phosphine oxide and a high boiling organic solvent.

Abstract: An improved process for recovering high purity resorcinol produced by the rearrangement of m-diisopropylbenzene dihydroperoxide in which the rearranged product mixture is neutralized, the neutralized mixture being filtered, the filtrate being admixed with toluene, the acetone being removed by distillation and the acetone-free rearranged product/toluene mixture being steam distilled to provide an aqueous resorcinol containing phase from which the resorcinol is recovered.

Abstract: 4,4'-Dihydroxybiphenyl is purified to remove sulfur-containing impurities, color bodies and/or phenyl-substituted phenol compounds by heating in the presence of a mixture of water and a water-miscible organic compound selected from acetone and C.sub.1-6 alkanols or diols for a time sufficient to remove substantial quantities of the sulfur-containing impurity, color bodies and/or phenyl-substituted phenol compound and thereafter recovering the purified 4,4'-dihydroxybiphenyl.

Abstract: A process for the preparation of pyrocatechol and hydroquinone by reaction of phenol with a peroxidic hydroxylating reagent followed by working-up of the resultant reaction mixture is disclosed. The work-up procedure is carried out in a first rectification column operated under specified conditions and having specified separation stages in a rectification section and a stripping section whereby there is distilled overhead components which boil at a temperature lower than phenol. Taken off from the bottom is a mixture comprising phenol and materials of higher boiling point which are fed into a second rectification column which is also operated under very specified conditions whereby pure phenol is recovered overhead leaving a bottoms comprising phenol pyrocatechol and hydroquinone which are then processed to separate phenol from a mixture of pyrocatechol and hydroquinone.