Use of silica catalyst for selective production of lactams

Abstract

A process for selective preparation of lactams which comprises contacting, in the vapor phase, an aliphatic or aromatic aminonitrile having the formula HR.sub.1 N--D--CN wherein D is a divalent organic moiety and wherein R.sub.1 is (C.sub.1 -C.sub.4) alkyl or hydrogen with an effective amount of a silica catalyst, in the form of substantially spherical beads having a BET surface area greater than about 250 m.sup.2 /g, preferably between 300 and 500 m.sup.2 /g, and an average pore diameter less than about 20 nanometers preferably 8-10 nanometers at a temperature in the range of about 200.degree. to about 400.degree. C. and at a hydrogen or inert gas flow with a pressure in the range of about 0 to about 300 kPa, in the presence of: (a) ammonia in an amount equal to from 0 to about 50 mole percent of the molar amount of aliphatic or aromatic aminonitrile present; and (b) water in an amount from at least about 1.0 to about 50 times the molar amount of aliphatic or aromatic aminonitrile present for a time sufficient to produce the corresponding lactam is disclosed. The preferred aminonitrile is .epsilon.-aminocapronitrile. A process for the selective conversion of aliphatic or aromatic aminonitriles having the formula HR.sub.1 N--D--CN into the corresponding lactam in the presence of alkyl or aryl mononitrile or alkylene or arylene dinitriles by use of a silica catalyst, preferably a spherical silica catalyst with recovery of substantially all the alkyl or aryl mononitrile or alkylene or arylene dinitrile originally present is also disclosed.