Based on the previous study in frontal displacement chromatography (FDC) packed with Pd-Al2O3, two groups of separation experiments were conducted to derive the rules how the two most significant factors, temperature and gas flow rate, to influence the separation performance. Separations of the first group were carried out at the feed gas flow rate of 15 mL/min and temperature of 303-213 K, and the second group at 253 K and 10-100 mL/min, with the identical composition of feedstock ((5 +/- 0.1)%H-2-(5 +/- 0.1)%D-2-(90 +/- 0.1)%Ar). The results indicate the derived rules are consistent with those from references: 1) the rules of temperature effects on separation efficiency lie in two aspects that the lower the temperature is, the larger the thermodynamic separation effect is, and the higher the temperature is, the quicker the hydrogen isotopes exchange dynamics becomes. As to FDC using palladium, 263-213 K will be an appropriate temperature range to have excellent separation performance achieved with the insight into these two aspects. 2) the rule of the influence of gas flow rate basically obeys the van Deemter equation, which means that it does exist an theoretically optimal gas flow rate, (u) over bar (opt), at a certain temperature and for a certain composition of feedstock, and considering the theoretics and efficiency, separations conducted at the gas flow rate of an suitable range that higher than (u) over bar (opt) but less than 10 (u) over bar (opt) can derive good separation performance. The results and discussion have verified the imperative impact of temperature and gas flow rate on the separation performance of this FDC method, and the derived desirable temperature and gas flow rate ranges would supply valuable supports and references for future applications of FDC in hydrogen isotopes separation and tritium recovery in fusion reactors. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.