Interaction between the LaNi 5-type intermetallic compound and hydrogen sulfide

Abstract

H 2S interaction with powdered La 0.95Ce 0.05Ni 4.98Al 0.02 has been studied in the temperature range 293–973 K. Sorption experiments were carried out using a flow system with gas stream 3 vol% H 2S in Ar, 1.5 vol% H 2S in Ar and 3% H 2S/60% H 2/37% Ar. Structural changes and surface morphology were studied by X-ray diffraction and scanning electron microscopy. At T = 293 K, large amounts of H 2S were absorbed by the sample without significant changes in its structure, corresponding to x = 4. 5 for La 0.95Ce 0.05Ni 4.98Al 0.02(H 2S) x. At T = 353 K, hydrogen sulfide was also absorbed; however, after the first 100 min of total absorption without any products in the outlet gas, 10–20% H 2 was registered (with regard to amount of H 2S in the initial gas stream). X-ray patterns show the beginning of the formation of Ni 3S 2 and amorphous phase with a diffuse maximum in the range 24–32 ° (2θ, Cu-K α). With T increasing, H 2 content increases and equals 30–40% at T = 433 K and 50% at T = 773 and 973 K. According to XRD, Ni 3S 2. La 2S 3 and initial phase are present. After prolonged testing at 773 K, LaH 2 peaks appeared in X-ray patterns. Electron micrographs show large particle formation with porous flaky sulfides distributed over them. Experimental data for a 3% H 2S/60%/H 2/37% Ar mixture are in agreement with those described above. H 2S is removed from the mixture at T = 773 K while the amount of H 2 is constant. This research was carried out in connection with the problem of refining H 2 produced from natural gas containing H 2S.