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Polyamide Synthesis from 6‐Aminocapronitrile, Part 2: Heterogeneously Catalyzed Nitrile Hydrolysis with Consecutive Amine Amidation
Author(s) -
van Dijk Adrianus J. M.,
Duchateau Robbert,
Hensen Emiel J. M.,
Meuldijk Jan,
Koning Cor E.
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200601898
Subject(s) - nitrile , catalysis , polyamide , chemistry , hydrolysis , zirconium , polymer chemistry , amide , adsorption , metal , organic chemistry
To test the potential of heterogeneous catalysts for the nylon‐6 synthesis from 6‐aminocapronitrile, a number of zeolites, aluminum silicate, and metal oxides were tested as catalysts for the model reaction of pentanenitrile with water and hexylamine to N ‐hexylpentanamide. All zeolitic and aluminum silicate systems showed an insufficient performance, while the metal oxides (TiO 2 , ZrO 2 , Nb 2 O 5 ) showed very promising results. The kinetic behavior of the metal oxides was further investigated. First the nitrile was catalytically hydrolyzed to the terminal amide and subsequently the amidation of the hexylamine occurred. To polymerize 6‐aminocapronitrile into nylon‐6, more than 99 % nitrile conversion was required to obtain a high‐molecular‐weight polymer. Pentanenitrile conversions larger than 99 % can be obtained within six hours, at 230 °C, by using ZrO 2 as the catalyst. A kinetic study (by using IR spectroscopy) on the behavior of the metal oxides demonstrated that the adsorbed nitrile was catalytically hydrolyzed at the surface, but remained tightly bound to the surface. Zirconia‐catalyzed polymerizations of 6‐amino‐capronitrile demonstrated that high‐molecular‐weight nylon‐6 is feasible by using this route.