钯与氢(H_2,D_2)反应的热力学性质研究

Thermodynamic Investigation of Interaction between Palladium with Hydrogen (H_2, D_2)

采用PVT方法精确测定了 40～ 60目的海绵钯 (Pd)粉末在 5～ 5 0℃范围内吸放H2 ,D2 的P C T曲线。结果表明 :2 5℃ ,0 .1MPa时H2 ,D2 在Pd中的溶解度分别为 75 .8和 70 .4ml(STP)·g- 1 Pd;Pd与H2 ,D2 反应的坪台热力学函数分别为 :ΔHa=-18.7kJ·mol- 1 H ,-17.6kJ·mol- 1 D ,ΔSa=-4 6.4J·K- 1 ·mol- 1 H ,-4 9.6J·K- 1 ·mol- 1 D ;ΔHd=2 1.3kJ·mol- 1 H ,18.7kJ·mol- 1 D ,ΔSd=5 0 .8J·K- 1 ·mol- 1 H ,49.1J·K- 1 ·mol- 1 D。H ,D在α相的溶解热力学函数为 :ΔHr→ 0 =-6.5kJ·mol- 1 H ,-5 .6kJ·mol- 1 D ;ΔSr→ 0 =-5 3 .5J·K- 1 ·mol- 1 H ,-5 3 .7J·K- 1 ·mol- 1 D。Pd Q(Q =H ,D)体系存在明显的迟滞效应 ,升高温度可改善吸放氢循环的压力迟滞效应 ,但不能消除。伴随迟滞效应的吉布斯自由能损失 (ΔGloss)在低于 5 0℃时保持不变 ,对Pd H和Pd D体系分别为 1.2 8和 1.2 5kJ·mol- 1 H(D) ;当高于 5 0℃时ΔGloss分别减小约 4%和 11%。

The absorption and desorption pressure-composition isotherms of H 2 and D 2 in sponge palladium particle, which is of 40～60 mesh, were experimentally measured at the range of 5 to 50 ℃. The enthalpy and entropy in the plateau range and dilute phase were derived from the P-C-T curve using Vant′Hoff equation and the Sievert constant. The solubility of H 2 and D 2 is 75.8 and 70.4 ml(STP)·g -1 Pd at 0 1 MPa and 298 K, respectively. In the plateau range, ΔHa =-18.7, ΔHd=21.3 kJ·mol -1, ΔSa= -46 4, ΔSd=50.8 J·K -1·mol -1 for H and ΔHa= -17.6, ΔHd=18.7 kJ·mol -1, ΔSa=-49.6, ΔSd=49.1 J·K -1·mol -1 for D. But in the dilute phase, ΔH r→0= -6.5 kJ·mol -1, ΔS r→0=-53.5 J·K -1·mol -1 for H and ΔH r→0=-5.6 kJ·mol -1, ΔS r→0=-53.7 J·K -1·mol -1 for D, respectively. There is hysteresis effect in the palladium-hydrogen system. It can be decreased by ramping temperature, but cannot be eliminated. Accompanying with the hysteresis effect, the loss of Gibbs free energy is a constant below 50 ℃, which is 1.28 for H and 1.25 kJ·mol -1 for D, while the temperature is higher than 50 ℃, the loss of Gibbs free energy decreases by nearly 4% and 11%, respectively.