THE EFFECT OF CRYSTAL SIZE ON THE METHYLAMINES SYNTHESIS PERFORMANCE OF ZK-5 ZEOLITES

ZK-5 zeolites of varying crystal size are obtained using various sourc es of K and Cs, as well as by the substitution of Sr for Cs or the add ition of HF to a K,Cs gel. The H-ZK-5 so prepared is used as a catalys t for methylamines synthesis from methanol and ammonia. We observe tha t the larger crystals obtained from K,Sr gels (2.0 mu m) and modified K,Cs gels (1.8-3.9 mu m) are less active than the smaller crystals of the standard K,Cs-derived zeolites (0.4 mu m). However, the larger cry stals give rise to extremely low selectivities of the undesired trimet hylamine (TMA) product (1C%). This is the first demonstration of such low TMA selectivities at the molar N/C feed ratio of unity and at meth anol conversions of 90C% without the use of zeolite modification. (C) 1998 Elsevier Science B.V. All rights reserved.