This invention relates to the selective conversion of aliphatic and aromatic aminonitriles such as .epsilon.-aminocapronitrile into the corresponding lactams such as .epsilon.-caprolactam by employing a silica catalyst particularly a silica catalyst in the form of spherical beads having high BET surface area, narrow pore and grain size distributions.
N-substituted amides, especially 5, 6 and 7 membered lactams, are important raw materials for nylon 4, 5 and 6.
U.S. Pat. No. 2,357,484 (E. L. Martin) discloses a vapor phase process for preparing compounds containing the N-substituted amide group, for example, .epsilon.-caprolactam, by passing a vaporized mixture of water and an aliphatic amino-hydrogen-containing aminonitrile, or a vaporized mixture of water and a nitrile and amino-hydrogen-containing amine over a dehydration catalyst such as activated alumina, silica gel titanium oxide or borophosphoric acid. U.S. Pat. No. 2,357,484 also discloses that diamides are produced by passing a vaporized mixture of water and dinitriles and monoamines over the dehydration catalyst.