氢气分离提纯用钯及钯合金膜的研究进展

伴随着煤、石油和天然气等传统化石能源在使用过程中产生的温室效应、能源危机等弊端,更清洁的氢能逐渐受到关注.氢能在能源、交通、工业等领域具有广阔的应用前景,尤其以燃料电池车为代表的交通领域是氢能初期应用的突破口与主要市场.而氢燃料电池对氢气浓度要求较高,氢气中即使微量的H2S和CO杂质也会严重降低电池性能.因此,需要对氢...

Progress in Pd and Pd Alloy Membranes for Hydrogen Separation and Purification

With the greenhouse effect and energy crisis caused by the use of traditional fossil energy,such as coal,oil and natural gas,cleaner hydrogen energy,especially high-purity hydrogen,has gradually attracted much attention.Hydrogen energy has wide application prospects in energy,transportation,industry,and other fields,especially the transportation field represented by fuel cell vehicles is the breakthrough and main market for the initial application of hydrogen energy.Hydrogen fuel cells have high requirements for hydrogen purity,and even traces of H2S and CO impurities in hydrogen will seriously deteriorate the performance of the cell.Therefore,it is essential to remove impurity gases to purify the hydrogen.Palladium and palladium alloy membranes have been used in the separation and purification of hydrogen due to their extremely high selective permeability to hydrogen,but the low chemical stability of palladium and palladium alloy membranes restricts their wide application.In the present paper,we reviewed the research progress and existing problems in hydrogen permeation and impurity gas poisoning resistance of pure Pd membranes,Pd-Ag,Pd-Y,Pd-Pt,Pd-Cu and Pd-Au binary alloy membranes,and Pd-Ag-M and Pd-Cu-M ternary alloy membranes,and forecasted the future research direction.Pure palladium membrane had good selective permeability to hydrogen,but its mechanical properties and chemical stability were poor.When the temperature was lower than 300℃,the transformation of a phase toβphase would cause the palladium membrane hydrogen embrittlement,and the membrane was easy to be poisoned by H2S,CO,etc.The competitive adsorption of H2S and CO on the membrane surface would occupy the dissociation site of hydrogen,thereby reducing the hydrogen permeability.Among them,the poisoning effect was more significant at low temperature and high CO concentration,but the poisoning effect was reversible.Compared with pure palladium membrane,the cost of palladium-based binary alloy membrane was lower.Pd-Ag and Pd-Y alloy membranes had better hydrogen permeability but poor resistance to impurity gas poisoning.In addition,during the hydrogen separation process,the Pd-Ag alloy membrane would form hydrogen bubbles along the grain boundaries,eventually forming pinholes and causing the membrane to fail;the Pd-Y alloy membrane was easily oxidized,resulting in the decrease of hydrogen permeability.Pd-Pt,Pd-Cu and PdAu alloy membranes had the opposite characteristics,and the anti-poisoning performance of impurity gas was excellent,but the hydrogen permeability was poor.Among them,Pd-Pt alloy membrane had good high temperature stability and sulfur poisoning resistance,but the hydrogen permeability was low.The application of Pd-Cu alloy membrane in large-scale H2 separation still had some problems,such as poor thermal stability and chemical stability,Cu segregation on the membrane surface,H2 permeation hysteresis,and imperfect alloy annealing process,etc.Although Pd-Cu alloy membrane could resist the poisoning of impurity gases to a certain extent,its inhibitory effect was limited,and it could not completely eliminate the influence caused by H2S,CO and other impurity poisons.It was still a difficult point to synthesize a Pd-Cu alloy membrane with both the high anti-poisoning performance of the fee structure and the high hydrogen permeability performance of the bcc structure.Au in the Pd-Au alloy membrane exhibited a strong tendency to surface segregation and greatly improved the solubility of hydrogen.These two characteristics made the stability of the membrane greatly reduced at higher temperatures.The existence of local cracks in the gold layer of the Pd-Au composite membrane reduced the selective permeability to hydrogen.And in the presence of H2S,the effect of temperature and exposure time on the hydrogen permeability of PdAu alloy membranes remained to be studied,and the mechanism of the poisoning effect of multi-element impurity gases was still unclear.Compared with the palladium-based binary alloy membrane,the palladium-based ternary alloy membrane improved both the anti-poisoning performance and the permeability performance.Adding a third alloying element such as Cu and Au with high anti-poisoning properties to the Pd-Ag binary alloy could significantly enhance the anti-poisoning properties of the Pd-Ag alloy and maintain or even enhance its hydrogen permeability.In order to improve the hydrogen permeability of Pd-Pt,Pd-Cu and Pd-Au alloy membranes,alloy elements with good hydrogen permeability such as Ag and Y were usually added to make palladium-based ternary alloy membranes,and for Pd-Cu alloy,adding Au and Zr could further improv its anti-poisoning performance.But palladium-based ternary alloy still had some problems,such as alloy element segregation,difficult to achieve precise control of the composition ratio of each component,etc.,moreover,the synthesis process of palladium-based ternary alloy membrane was more complex and more costly than that of binary alloy membrane.As to the future research direction of palladium alloy membrane,the problem of reduced membrane stability and durability caused by the poisoning of impurity gases such as CO and H₂S needed to be well solved.Especially,when the palladium membrane was exposed to CO atmosphere,the influence mechanism of PdC formed at high temperature relative to the palladium membrane should be clarified.In addition,the coupling poisoning mechanism of the palladium alloy membrane when multiple impurity gases coexist remained to be studied.Finally,we hoped to explore an evaluation method for predicting the service life of palladium and palladium alloy membrane by combining theoretical calculation with experiments.