Separation performance of foils from Pd-In(6%)-Ru(0.5%), Pd-Ru(6%), and Pd-Ru(10%) alloys and influence of CO2, CH4, and water vapor on the H2 flow rate through the test membranes

The H-2 flow rate through the 30-mu m thick foil from Pd-Ru(6%) and Pd-Ru(10%) alloys at 673 and 773 K was found to be controlled by the diffusion of H atoms in the foil bulk. The interrelation between hydrogen permeability through the Pd-In(6%)-Ru(0.5%), Pd-Ru(10%), Pd-Ru(6%), and Pd-Ag(23%) membranes and the permeability pre-expo-nential factors in the Sieverts equation in the 573-773 K temperature interval indicated that the hydrogen permeability depended on the structural characteristics of palladium alloys. The influence of the CO2, CH4, and water vapor impurities on the H-2 flow rate through the studied membranes depended on the driving force nature (the sweep gas or transmembrane pressure) used for the development of the partial hydrogen pressure difference across the membrane. The negative influence of CH4 and CO2 was observed only when using a transmembrane pressure and at the impurity content of 20% or more. This effect increased with increasing temperature in the 573-773 K range, with the influence of CO2 being more pronounced due to its reaction with hydrogen leading to the formation of CO. The influence of water vapor was studied at its 11-23% content in hydrogen and at 573 and 773 K of temperature. The negative influence of water vapor was found to subside as its content in the hydrogen mixture decreased and the temperature increased. It was shown that water vapor can be used as a sweep gas and at T = 773 K its influence on the H-2 flow rate through the membrane was almost the same as that of N-2.