A novel facilitated transport membrane, a bulk flow liquid membrane (BFLM), was applied to ethylene/ethane separation using silver nitrate as a carrier. In this membrane system, a carrier solution is supplied to the feed gas side (high pressure side) of a UF membrane and is allowed to permeate to the permeate side (low pressure side). The transferred carrier solution is recycled to the feed side. The effect of such convective flow of the carrier solution through the membrane on ethylene permeance was investigated using a dead-end type filtration cell equipped with an ultrafiltration membrane. The C2H4 permeance, R-C2H4, increased with increasing the volumetric permeation flux of the carrier solution u, and when u was 4 x 10(-5) m s(-1) and the C2H4 partial pressure was 9 kPa, R-C2H4 was 4 x 10(-5) mol m(-2) s(-1) kPa(-1) and the selectivity of C2H4 over C2H6 was 1100. This value was approximate to 30 times that at u = 0. This type of membrane was very stable during intermittently performed experiments for more than 2 months. (C) 2002 Elsevier Science B.V. All rights reserved.