Abstract: In a process for the recovery of N-ethylpiperazine by distillation from mixtures with N,N'-diethylpiperazine, piperazine, ethanol, water and accompanying substances, water is added in a manner such that, at the location of the addition of the water, the piperazine concentration is greater than the N-ethylpiperazine concentration. The water may be added to the reflux to the top of the column.

Abstract: Process for the preparation of 1,4-butanediol or tetrahydrofuran or both by the catalytic hydrogenation of maleic anhydride, succinic anhydride, maleic acid, succinic acid, fumaric acid, or the alkyl esters of these acids at temperatures of from 100.degree. C. to 350.degree. C. and pressures of from 50 bar to 350 bar over a catalyst containing cobalt as the active metal and one or both of the elements copper and phosphorus, if necessary in the presence of an aliphatic alcohol.

Abstract: 4-Pentenoates are prepared by isomerization by a process in which isomeric pentenoates are treated with a zeolite of the pentasil type at from 50.degree. to 300.degree. C., and the 4-pentenoate is distilled off from the reaction mixture.

Abstract: A catalyst containing copper and silica is prepared by a process in which an aqueous alkali metal silicate solution containing from 1 to 26% by weight of SiO.sub.2 is brought to a pH of from 0.5 to 2.0 with nitric acid, an aqueous copper nitrate solution containing from 5 to 15% by weight of Cu is added, after the addition of the nitric acid, so that a clear solution containing from 0.18 to 3.0 moles of Cu per mole of SiO.sub.2 is formed, the resulting solution is mixed with an aqueous alkali metal carbonate solution at from 40.degree. to 80.degree. C., the pH of the mixture being kept at from 7.5 to 8.5, and the precipitated material is separated off, dried, calcined by heating at from 250.degree. to 400.degree. C. and pressed in a conventional manner to give catalyst moldings. The catalyst thus obtained is used for the hydrogenation of dialkyl dicarboxylates to diols.

Abstract: 4-Pentenoates are prepared by isomerization by a process in which isomeric pentenoates are treated at elevated temperatures in the presence of a zeolite containing metals of group eight of the Periodic Table and the 4-pentenoate is distilled off from the reaction mixture, and the zeolite contains iron, cobalt and/or nickel.