H-2 Adsorption on Cu(I)-SSZ-13

2018-01-11
İpek Torun, Bahar
Pollock, Rachel A.
Brown, Craig M.
Üner, Deniz
Lobo, Raul F.
We report H-2 adsorption capacities reaching 0.05 wt % at 303 K and at 1 atm H-2 pressure on solid-state CuCl-exchanged [Al]-SSZ-13 and [B]-SSZ-13 zeolites. Differential heat of H-2 adsorption is found in the range between 16 and 48 kJ mol H-2(-1) on Cu(I)-SSZ-13 at 323 K and isosteric heat of adsorption is found between 20 and 55 kJ mol H-2(-1) on Cu(I)-[B]-SSZ-13 at temperatures between 293 and 323 K. Strong interactions between H-2 and the copper cations in Cu(I)-SSZ-13 are evidenced using Rietveld refinements of neutron powder diffraction patterns revealing Cu-deuterium (D-2) distances of 2.3(2) and 2.41(1) angstrom. A temperature dependent Cu(I) migration-away from the six-membered ring (6MR) and eight-membered ring (8MR)-is related to the high adsorption capacities of the samples at 303 K. At 10 K, access to Cu(I) at 6MR is sterically hindered by framework oxygen atoms (Cu-O-framework distance of 2.196(5) angstrom), rationalizing the low H-2 adsorption capacities of Cu(I)-SSZ-13 samples as compared to Na-SSZ-13 at 77 K.