Development of carbon alloy for selective recovery of hydrogen gas under low pressure and for hydrogen-isotope separation

为促进碱金属掺杂碳材料作为氢回收和同位素分离剂的应用，测定了碱金属掺杂碳在77K下的吸氢等温线。由RbC24组成的掺Rb玻璃箔在低压下表现出较高的吸氢能力。考虑到吸附-脱附是快速和可逆的，并且在半覆盖下的平衡压力很低，即40Pa.因此，以石榴石为原料制备的RbC24是一种很有前途的低压氢气回收试剂.测定了由多壁碳纳米管(MWCNT)制备的含钾多壁碳纳米管(MWCNT)和热处理温度分别为1000℃和1500℃的石油焦炭的氢(H_2)/氢(D_2)吸附等温线。根据这些等温线估算了同位素分离系数。与热处理温度为1000℃或1500℃的炭相比，MWCNT制备的KC10具有很大的同位素效应，但KC10(MWCNT)存在一个严重的问题，即重复吸附-解吸循环导致H2和D2的吸附量减少。

Hydrogen-sorption isotherms of alkali metal-doped carbons at 77 K were determined for promoting application of these materials as hydrogen-recovery and isotope-separation agent. The hydrogen-sorption behavior of rubidium-doped Grafoil, with composition of RbC24, showed high sorption ability against hydrogen at low pressure. Taking into account the fact that sorption-desorption was fast and reversible, and the equilibrium pressure at half coverage was very low, i. e. 40 Pa, RbC24 prepared from Grafoil is promising as a recovery agent for hydrogen gas at low pressure. The hydrogen(H2)/deuterium(D2)-sorption isotherms of potassium-doped carbons with composition of KC10, prepared from multi wall carbon nanotube(MWCNT) and carbons derived from petroleum cokes with heat-treatment temperatures of 1000 and 1500°C, were also determined. Isotope separation coefficient was estimated from those isotherms. A very large isotope effect was found for KC10 prepared from MWCNT, compared with those prepared from carbons with heat-treatment temperatures of 1000 or 1500°C. However, a severe problem was found for KC10(MWCNT) that repetition of the sorption-desorption cycles resulted in the decrease of the sorbed amount of H2 and D2.