Abstract: The invention provides a method for producing terephthalic acid, characterized by including subjecting a p-phenylene compound to liquid-phase oxidation reaction by use of a molecular-oxygen-containing gas in the presence of a catalyst at least containing a heavy metal compound and a bromine compound, and hydrous acetic acid having a water content of 1 to 15 mass %, to thereby yield a slurry; regulating the temperature of the slurry to 35 to 140° C., to thereby cause terephthalic acid to precipitate; removing the terephthalic acid through solid-liquid separation, to thereby recover a mother liquor; and recovering the catalyst from the mother liquor through a series of the following steps (1) to (4) for reusing at least a portion of the catalyst in the liquid-phase oxidation reaction: (1) an adsorption step including regulating the ratio “amount by mole of bromide ions in the mother liquor/total amount by mole of heavy metal ions in the mother liquor” to 0.

Abstract: A method of replacing a first dispersion medium in a starting slurry composed of the first dispersion medium and isophthalic acid crystals with a second dispersion medium. The starting slurry is tangentially fed to a vertically extending cylindrical portion of a cyclone-shaped nozzle disposed at an upper portion of a replacement tank of a dispersion medium replacement apparatus, from a tangential direction of the cylindrical portion. The fed starting slurry moves circularly along an inner wall of the cylindrical portion. The slurry circularly moving is then discharged from an opening which is disposed at a vertically lower end of the cylindrical portion and dispersed in a second dispersion medium which is fed from a lower portion of the replacement tank. The replaced slurry composed of isophthalic acid crystals and the second dispersion medium is mainly discharged from the lower portion of the replacement tank, and the first dispersion medium is mainly withdrawn from the upper portion of the replacement tank.

Abstract: The present invention relates to a multi-stage crystallization process which comprises the steps of feeding a solution of terephthalic acid or a slurry (raw slurry) containing terephthalic acid partially precipitated to a first crystallization vessel to precipitate the terephthalic acid therein; and feeding a slurry (crystallization slurry) containing the thus precipitated terephthalic acid sequentially to second and subsequent crystallization vessels, wherein while continuously supplying a cleaning solvent to a delivery conduit connecting the former-stage crystallization vessel and the next latter-stage crystallization vessel to each other, the crystallization slurry is fed through the delivery conduit.

Abstract: In the production of an alicyclic aldehyde, a starting aromatic aldehyde is converted into an aromatic acetal for protecting the formyl group. The aromatic ring of the aromatic acetal is then hydrogenated to convert the aromatic acetal into an alicyclic acetal, which is then hydrolyzed to cleave the acetal protecting group to obtain the aimed alicyclic aldehyde.

Abstract: Disclosed are processes for industrially advantageously producing at a good yield respectively, a hydrogenated aromatic polycarboxylic acid and an acid anhydride thereof each having a high purity. The present invention provides processes for producing a hydrogenated aromatic polycarboxylic acid by (1) hydrogenating an aromatic polycarboxylic acid at a hydrogen partial pressure of 1 MPa or more by a batch system in the presence of a catalyst containing rhodium and palladium in a proportion of 0.

Abstract: In the production of an alicyclic aldehyde, a starting aromatic aldehyde is converted into an aromatic acetal for protecting the formyl group. The aromatic ring of the aromatic acetal is then hydrogenated to convert the aromatic acetal into an alicyclic acetal, which is then hydrolyzed to cleave the acetal protecting group to obtain the aimed alicyclic aldehyde.

Abstract: Disclosed are processes for industrially advantageously producing at a good yield respectively, a hydrogenated aromatic polycarboxylic acid and an acid anhydride thereof each having a high purity. The present invention provides processes for producing a hydrogenated aromatic polycarboxylic acid by (1) hydrogenating an aromatic polycarboxylic acid at a hydrogen partial pressure of 1 MPa or more by a batch system in the presence of a catalyst containing rhodium and palladium in a proportion of 0.

Abstract: A process for producing a hydrogenation product of aromatic carboxylic acid which comprises continuously producing the hydrogenation product of aromatic carboxylic acid by hydrogenating an aromatic carboxylic acid having a melting point of 250° C. or higher in a solvent in the presence of a solid catalyst, wherein the hydrogenation is conducted in a condition such that substantially the entire amount of the aromatic carboxylic acid of a raw material is dissolved in the solvent by recycling a portion of a reaction liquid taken out of a reactor into the reactor. An aromatic carboxylic acid having a high melting point and hardly soluble in solvents can be hydrogenated at a suitable reaction temperature in accordance with a continuous process without using a great amount of a solvent and the reaction product of the object compound can be produced very efficiently.

Abstract: A process for producing a hydrogenation product of aromatic carboxylic acid which comprises continuously producing the hydrogenation product of aromatic carboxylic acid by hydrogenating an aromatic carboxylic acid having a melting point of 250° C. or higher in a solvent in the presence of a solid catalyst, wherein the hydrogenation is conducted in a condition such that substantially the entire amount of the aromatic carboxylic acid of a raw material is dissolved in the solvent by recycling a portion of a reaction liquid taken out of a reactor into the reactor.

Abstract: Dialkylnaphthalene is oxidized to naphthalenedicarboxylic acid in a lower aliphatic carboxylic acid solvent in the presence of a catalyst comprising a cobalt compound, a manganese compound and a bromine compound having an atomic ratio of manganese to cobalt of 0.03 to 0.5. The catalyst is supplied to the oxidation reaction zone so that the total amount of cobalt and manganese is 0.025 to 0.1 gram atom based on 1 gram mol of the dialkylnaphthalene. An oxidation product slurry is subjected to solid-liquid separation when the concentration of the naphthalenedicarboxylic acid in the slurry is 8 to 30% by weight. The process prevents the by-production of benzotricarboxylic acid such as trimellitic acid, thereby drastically reducing the incorporation of heavy metal complexes with trimellitic acid into naphthalenedicarboxylic acid crystals.

Abstract: A process for the production of high-purity dimethyl 2,6-naphthalenedicarboxylate, which comprises esterifying 2,6-naphthalenedicarboxylic acid obtained by liquid phase oxidation of 2,6-dialkylnaphthalene with molecular oxygen in the presence of an oxidation catalyst, with methanol and then purifying a crude ester formed by the esterification, the crude ester being purified in the presence of an aromatic hydrocarbon as a solvent, in which impurities contained in a reaction product obtained by the esterification of 2,6-naphthalenedicarboxylic acid prepared by the liquid phase oxidation of 2,6-dialkylnaphthalene are effectively removed with simple procedures, oxidation catalyst metals are recovered, a crystal of naphthalenedicarboxylic acid formed by the oxidation of dialkylnaphthalene and/or its oxide derivative can be easily separated, and the oxidation catalyst to be brought into the step of producing dimethyl naphthalenedicarboxylate is recovered in the process of the production of naphthalenedicarboxylic a

Abstract: A process for continuously producing an aromatic carboxylic acid comprising oxidizing an aromatic compound substituted with alkyl groups with molecular oxygen gas in the liquid phase in a solvent containing a lower aliphatic carboxylic acid in the presence of a catalyst comprising heavy metal compounds and a bromine compound, wherein a mother liquor which is obtained after removal of crystals from a reaction liquid of the liquid phase oxidation and contains heavy metal ions and bromine ion as catalyst components is brought into contact with a chelate resin of an anion exchange type to recover the catalyst components.The catalyst components are efficiently recovered, and auxiliary agents in an amount exceeding the equivalent amount and excessive labor are not necessary.

Abstract: There are disclosed a method for replacing a dispersion medium wherein an original slurry comprising solid particles and an original dispersion medium is introduced in a dispersion medium replacement column at the top thereof, a replacing dispersion medium is introduced in the column at the bottom thereof to replace the original dispersion medium with the replacing dispersion medium, the resultant replaced slurry comprising the solid particles and the replacing dispersion medium is taken out from the column at the bottom thereof, and the original dispersion medium is taken out from the column at the top thereof, which method comprises dividing the fluid in the intermediate portion into a plurality of parallel streams, stirring the slurry in the bottom of the column to uniformize the slurry, and controlling the feed rates of the replacing dispersion medium and the replaced slurry to maintain the slurry in the bottom portion of the column at a concentration higher than that of the slurry in the intermediate por

Abstract: A process for producing highly pure terephthalic acid comprising: (a) oxidizing a p-phenylene compound in the liquid phase in the presence of acetic acid, to produce a liquid-phase oxidation product, (b) separating the liquid-phase oxidation product into the following: (i) a first mother liquid containing acetic acid and (ii) a crude terephthalic acid, (c) evaporating, in whole or in part, the first mother liquid, to produce a vapor, (d) feeding the vapor, or a condensate thereof, to an intermediate stage of a distillation tower, carrying out an azeotropic distillation and withdrawing through a bottom of the distillation tower a concentrated acetic acid, (e) subjecting the crude terephthalic acid to a refining treatment, which is a catalytic hydrotreatment, a catalytic treatment or a recrystallization, which is carried out in the presence of is water, (f) cooling and crystallizing the resultant liquid from step (e), to produce a pure terephthalic acid and a second mother liquor, (g) subjecting the second moth

Abstract: There is disclosed a process for producing highly pure terephthalic acid by converting a slurry of terephthalic acid crystals in acetic acid solvent which crystals are obtained by liquid-phase oxidation of p-alkylbenzene, into a slurry thereof in water solvent by mother liquor replacement and then subjecting the latter slurry to a catalytic hydrogenation treatment which process comprises the steps of introducing the slurry of terephthalic acid crystals in acetic acid into a mother liquor replacement column at the top portion; forming an accumulation layer of the terephthalic acid crystals at the bottom portion by the sedimentation of the crystals; feeding replacing water sufficient for the formation of upward rising stream of water to the inside of the column at the bottom portion; and withdrawing the accumulation layer of the crystals from the bottom portion of the column.

Abstract: There is disclosed a process for producing terephthalic acid which comprises oxidizing in a liquid-phase a starting raw material comprising p-xylene incorporated with 3 to 35% by weight of p-tolualdehyde based on the same at a temperature in the range of 120.degree. to 240.degree. C. by means of a molecular oxygen-containing gas by using a lower aliphatic monocarboxylic acid as a solvent in the presence of a catalyst comprising a manganese compound having 50 to 1000 ppm by weight of manganese atoms, a cobalt compound having 50 to 2000 ppm by weight of cobalt atoms and a bromine compound having 100 to 4000 ppm by weight of bromine atoms, each based on the solvent. By virtue of the above specific constitution, it is made possible to produce high-quality terephthalic acid with a high residual rate of the lower aliphatic monocarboxylic acid as a solvent minimized in its loss, thereby enabling the production of high-quality polyester with high whiteness from the above terephthalic acid and a glycol.

Abstract: A process for producing a carboxylated compound, which comprises reacting a carbonyl compound with hydrogen peroxide in the presence of an organo-arsenic acid of the formula (1), ##STR1## wherein: R.sup.1 is a C.sub.1 -C.sub.12 alkyl group which may be substituted or an aryl group which may be substituted,R.sup.2 is a hydroxyl group or the same group as that which defines R.sup.1,or alternatively, R.sup.1 and R.sup.2 may bond to each other to form a five-membered or six-membered ring together with As atoms to which these groups are bonded, andthe substituent(s) substituted on the above groups is/are selected from hydroxyl, carboxyl, carbonyl, sulfonyl, sulfonium, an amino group, an ammonium group, an alkyl group, an alkoxyl group and a halogen atom,while a water concentration in a reaction system is maintained at not more than 2% by weight, thereby to form a corresponding carboxylated compound.

Abstract: Novel methylthiophenol derivatives of the formula (I') and of the formula (IV) and processes for producing said derivatives ##STR1## wherein R is a tert-butyloxy group, a tert-amyloxy group, a p-methoxybenzyloxy group, a 2-(trimethylsilyl)ethoxy group, a 1-adamantyloxy group, a bornyloxy group, or an isobornyloxy group.

Abstract: A process for producing sulfonium compounds represented by the general formula (III) which comprises reacting alkylthiophenol derivatives represented by the general formula (I) and dialkyl sulfate represented by the general formula (II).General Formula (I): ##STR1## General Formula (II): (R.sup.2).sub.2 SO.sub.

Abstract: Disclosed is process for producing a sulfonium compound of the general formula (III), comprising reacting alkylthiophenol derivative of the general formula (I) and dialkyl sulfate of the general formula (II) in the presence of at least one inorganic compound selected from the group consisting of alkali metal carbonate, alkali metal hydrogencarbonate, alkaline earth metal hydroxide, alkaline earth metal carbonate, and oxides of Group II metals of the Periodic Table. ##STR1## wherein all the symbols are as defined in the appended claims.