Abstract: The catalytic dehydrogenation of piperidine to pyridine in the gas phase using hydrogen as the carrier gas is carried out with a silicon dioxide carrier activated with copper, nickel and chromium as the catalyst, the metals copper, nickel and chromium being present in an amount of 5-12:1-5:0.1-<0.7 parts by weight per 100 parts by weight of catalyst. The optimum hydrogen/piperidine molar ratio is 5:1, and purified and dried conversion gas from the dehydrogenation reaction is preferably recycled and used as the hydrogen.

Abstract: A process for the production of thionaphthene by dissociation of thionaphthene sulfonic acid such as obtained, for example, in the partial sulfonation of naphthalene fractions of coal tar, characterized in that the density of the reaction mixture is maintained essentially constant during the entire duration of the dissociation reaction and the thionaphthene formed is not removed by azeotropic distillation; a product of high purity is obtained in high yield in a substantially reduced reaction time.

Abstract: In a process for obtaining substantially sulfur free pure naphthalene from bituminous coal tar and thionaphthene as a by-product, a de-phenolized thionaphthene-containing naphthalene fraction from oxidative purification is extracted with concentrated sulfuric acid and acetic acid anhydride in benzene. The thionaphthene is converted into its sulfonic acid derivative and water washed from the benzene-naphthalene mixture. The benzene is distilled leaving pure naphthalene. The sulfonic acid group is cleaved from the thionaphthene with superheated steam to yield thionaphthene.