کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
74860 | 49103 | 2009 | 6 صفحه PDF | دانلود رایگان |

Neutron Rietveld refinement of a natural heulandite (Si/Al = 3.1) in its deuterium form was performed in space group C2/m. Two Brønsted acid sites were identified. One was on framework oxygen O1, occupied to 20% and headed toward the center of the 8-membered ring channel running parallel to [1 0 2]; the other was on O6, occupied to 30% and headed toward the 10-membered ring channel running parallel to the c-axis. Three other extraframework sites, located around a distance of 3 Å from the framework oxygens, were attributed to reabsorbed H2O molecules. On the whole, about 3.2 Brønsted acid sites were located representing about 37% of the value expected on the basis of the aluminium content. This discrepancy is attributed to proton transfer from the Brønsted site to reabsorbed H2O molecules, forming either a hydroxonium ion (H3O+) or charged clusters such as (H5O2)+ and (H7O3)+.
Journal: Microporous and Mesoporous Materials - Volume 123, Issues 1–3, 1 July 2009, Pages 15–20