Abstract: A method for operating a heat exchanger, in which a first operating mode is carried out in first time periods, and a second operating mode is carried out in second time periods that alternate with the first time periods; in the first operating mode a first fluid flow is formed at a first temperature level, is fed into the heat exchanger in a first region at the first temperature level, and is partially or completely cooled in the heat exchanger; in the first operating mode a second fluid flow is formed at a second temperature level, is fed into the heat exchanger in a second region at the second temperature level, and is partially or completely heated in the heat exchanger. A corresponding arrangement and a system with such an arrangement are also covered by the present invention.

Abstract: The present invention relates to a process for the manufacture of cyclic thio esters (thiolactones) and related compounds by hydrogenation of cyclic thioanhydrides in the presence of metal catalysts.

Abstract: The present invention relates to a process for the manufacture of cyclic monocarboxylic esters (lactones) and related compounds by hydrogenation of cyclic dicarboxylic acid anhydrides in the presence of metal catalysts.

Abstract: The present invention relates to a process for the manufacture of cyclic thio esters (thiolactones) and related compounds by hydrogenation of cyclic thioanhydrides in the presence of metal catalysts.

Abstract: The present invention relates to a process for the manufacture of cyclic monocarboxylic esters (lactones) and related compounds by hydrogenation of cyclic dicarboxylic acid anhydrides in the presence of metal catalysts.

Abstract: A process for the modification of a hydrogenation catalyst of the Raney nickel, Raney cobalt, nickel-on-carrier or cobalt-on-carrier type, which process includes treating the hydrogenation catalyst at temperatures of about 0° C. to about 120° C. with carbon monoxide, carbon dioxide, formaldehyde, a lower aliphatic aldehyde, an aromatic aldehyde, an aliphatic ketone, an aromatic ketone, a mixed aliphatic/aromatic ketone, glyoxal, pyruvaldehyde or glyoxylic acid as the modification agent in a liquid dispersion medium consisting of water or an organic solvent for a duration of about 15 minutes to about 24 hours. When the thus-modified catalyst is used in the hydrogenation of a nitrile to the corresponding amine, the selectivity is increased, and significantly favors the amount of the primary amine vis-à-vis the undesired secondary amine in the hydrogenation product as compared to when the corresponding unmodified catalyst is employed.

Abstract: A process for the modification of a hydrogenation catalyst of the Raney nickel, Raney cobalt, nickel-on-carrier or cobalt-on-carrier type, which process includes treating the hydrogenation catalyst at temperatures of about 0° C. to about 120° C. with carbon monoxide, carbon dioxide, formaldehyde, a lower aliphatic aldehyde, an aromatic aldehyde, an aliphatic ketone, an aromatic ketone, a mixed aliphatic/aromatic ketone, glyoxal, pyruvaldehyde or glyoxylic acid as the modification agent in a liquid dispersion medium consisting of water or an organic solvent for a duration of about 15 minutes to about 24 hours. When the thus-modified catalyst is used in the hydrogenation of a nitrile to the corresponding amine, the selectivity is increased, and significantly favors the amount of the primary amine vis-à-vis the undesired secondary amine in the hydrogenation product as compared to when the corresponding unmodified catalyst is employed.

Abstract: There is disclosed a catalytic hydrogenation process resulting in compounds of the formula ##STR1## wherein the dotted line represents a facultative bond, by hydrogenating the compound of the formula ##STR2## in the presence of a platinum or a nickel catalyst.