Patents by Inventor Otto Hallmann

Otto Hallmann has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 5391750
    Abstract: The present invention relates to a process for the preparation of 4-hydroxy-2,2,6,6-tetramethylpiperidine by heterogeneous catalytic hydrogenation of 4-oxo-2,2,6,6-tetramethylpiperidine in a melt or solution at temperatures of 60.degree. C. to 200.degree. C. and hydrogen pressures of 10 to 300 bar, in the presence of a catalyst comprisingfrom 20 to 68% by weight of copper,from 0 to 40% by weight of chromium,from 0 to 60% by weight of zinc,from 0 to 5% by weight of manganese,from 0 to 12% by weight of barium,from 0 to 15% by weight of silicon, andfrom 0 to 10% by weight of nickel,in each case based on the oxidic catalyst mass, and in which the catalyst is activated by hydrogen or a hydrogen-containing gas mixture, and separating the 4-hydroxy-2,2,6,6-tetramethylpiperidine from the catalyst.
    Type: Grant
    Filed: November 18, 1993
    Date of Patent: February 21, 1995
    Assignee: Huels Aktiengesellschaft
    Inventors: Gerhard Thelen, Guthard Mock, Otto Hallmann