A zeolite membrane module composed of SAPO-34 hollow fibers for use in fluorinated gas enrichment

Abstract

A membrane module composed of SAPO-34 hollow fibers was constructed for the enrichment of NF3, a strong greenhouse gas with a 100-year global warming potential (GWP)(1) of> 17,000. Growth of the SAPO-34 membrane was investigated on the alumina hollow fibers using in-situ growth and secondary growth methods. Heterogeneous nucleation of SAPO-34 crystal took place on the surface because of hetero-atoms existing on the support, contributing to early development of continuous zeolite film. Zeolite membranes were successfully prepared from both in-situ and secondary growth. The membrane prepared by secondary growth presented N-2 permeance as high as 168.4 GPU with an N-2/NF3 gas selectivity of 580.7. A SAPO-34 membrane module was assembled using the hollow fiber membranes produced by secondary growth, but separation performance of the module was reduced to N-2 permeance of 136.4 GPU with an N-2/NF3 gas selectivity of 133.7. When used for the enrichment of NF3 gas, a superior yield (98%) and enrichment ratio (20) were obtained from the module at a stage-cut of 0.95.