This invention relates to an iron-sulfur complex that is capable of efficiently catalyzing formation of hydrogen, and a method for producing hydrogen using the complex as a catalyst. The iron-sulfur complex provided herein comprises: a structure of formula (I) ##STR00001## wherein the ligands L.sup.1 to L.sup.3, L.sup.5 and L.sup.6 and the groups X.sup.1 to X.sup.3 are each selected from the group consisting of alkyl, alkenyl, alkynyl and aryl that are substituted or unsubstituted, hydroxyl, carbonyl, aldehyde, and so on; L.sup.4 is a bridging ligand selected from the group consisting of hydroxyl, carbonyl, and so on; and the symbol z means the charge, which is an integer with the range of 3 to +2. X.sup.1 and X.sup.2 may join together to form a bridging group between the two sulfur atoms. X.sup.3 may alternatively be a vacant site.

A catalyst composition for hydrogenation including (A) to (D), in which a mass ratio ((C)/(A)) is 0.1 to 4.0 and a mass ratio ((D)/(A)) is 0.01 to 1.00, (A): a titanocene compound represented by formula (1), ##STR00001## (wherein R.sup.5 and R.sup.6 are any group selected from hydrogen, a hydrocarbon group having 1 to 12 carbon atoms, an aryloxy group, an alkoxy group, a halogen group, and a carbonyl group. R.sup.1 and R.sup.2 are any group selected from the group consisting of hydrogen and a hydrocarbon group having 1 to 12 carbon atoms, and R.sup.1 and R.sup.2 are not all hydrogen atoms or all a hydrocarbon group having 1 to 12 carbon atoms), (B): a reductant formed from a compound containing an element selected from the elements Li, Na, K, Mg, Zn, Al, and Ca, (C): an unsaturated compound having a molecular weight of 400 or less, and (D): a polar compound.

Processes for manufacturing a purified aromatic carboxylic acid include contacting crude aromatic carboxylic acid with hydrogen in the presence of a catalyst in a hydrogenation reactor to form a purified aromatic carboxylic acid; separating vapor effluent from the purified aromatic carboxylic acid; scrubbing the vapor effluent to form a scrubber effluent; treating the scrubber effluent vapor to form a gaseous treated scrubber effluent and a liquid treated scrubber effluent; and removing at least a portion of organic impurities from the liquid treated scrubber effluent.

A catalyst includes a mixed metal oxide; an alumina; silica, and calcium, where the mixed metal oxide includes Cu and at least one of Mn, Zn, Ni, or Co. Such catalysts exhibit enhanced tolerance sulfur-containing compounds and free fatty acids.

The present invention relates to self-regenerating antioxidant catalysts and methods of using the same.

The invention comprises a process for the preparation of a [Ru(OAc).sub.2(Ligand)] catalysts of the formula I

##STR00001##

wherein R.sup.1 is C.sub.1-6 alkyl and R.sup.3 is hydrogen or C.sub.1-6 alkyl and R.sup.4 is hydrogen or C.sub.1-6-alkoxy.

[Ru(OAc).sub.2(Ligand)] catalysts are versatile hydrogenation catalysts.

A catalytic reaction method of the present invention is a method in which a starting compound is caused to react in the presence of a solvent using a catalyst. The solvent includes an organic solvent, an aqueous solvent, and an antioxidant. The reaction of the starting compound is performed in a two-phase system in which the organic solvent and the aqueous solvent are separate. A method for producing an organic compound according to the present invention includes causing a starting compound to react in the presence of a solvent using a catalyst, to synthesize an organic compound from the starting compound. The solvent includes an organic solvent, an aqueous solvent, and an antioxidant. The reaction of the starting compound is performed in a two-phase system in which the organic solvent and the aqueous solvent are separate.