A highly CO2-selective high-silica SSZ-13 zeolite membrane was used for H-2 production by separating CO2 from syngas (CO2/H-2 mixture). High-silica SSZ-13 zeolite membranes were fabricated using outside asymmetric alumina tubes by secondary growth of ball-milled SSZ-13 seeds. The composition of membrane gel and synthesis time were modified. The Si/Al ratio in framework of the membrane was as high as 42 when SiO2/Al2O3 ratio of the gel increased to 140. The effects of test parameters such as pressure drop, temperature, feed flow rate and concentration on membrane performance were investigated. The test pressure drop was up to 2 MPa. The ultra-high CO2/H-2 selectivity of 161 with excellent CO2 permeances of similar to 6.3 x 10(-7) mol/(m(2) s Pa) (=3760 GPU) were observed for the best membrane at 243 K and pressure drop of 0.2 MPa. Carbon dioxide permeance through high-silica SSZ13 zeolite membrane was 4.2 x 10(-7) mol/(m(2) s Pa) (=2500 GPU) at 298 K and pressure drop of 2.0 MPa, and the CO2/H-2 selectivity was 17.4. The current high-silica SSZ-13 zeolite membranes exceeded the upper bound of polymeric membranes and other inorganic membranes in CO2/H-2 plots and owned great potentials for H-2 production from syngas. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.