Theoretical study of the stability of carbene intermediates formed during the hydrodechlorination reaction of the CFxCl4-x family on the Pd(110) surface

In the present work the stability of the species CCl2, CFCl, CF2 and CHF, which are produced during the hydrodechlorination reaction of the CFxCl4-x family, have been investigated on the Pd(110) surface by applying ab initio periodic Density Functional Theory. The most stable configuration for these carbenes on this surface is the short-bridge. Hollow positions have not been found as stationary points in most of the cases. For the chlorinated fragments, the optimisation of these hollow positions resulted in partial or full dechlorinated fragments. The most stable configuration for the carbenes (short-bridge) was compared to the least stable one (top) within different surface conditions in order to verify any change in this stability trend. Both geometries are equally affected by the surface modifications for most of the carbenes. The short-bridge is, however, more sensitive to the coverage increase in the CHF case. CHF has the strongest binding energy to the Pd(110) surface, whilst CF2 has the least one. The stability trend of CHF, CFCl and CF2 helped to better understand the selectivity of the hydrodechlorination reaction of the mono carbon CFC's, for example, the suggestion that CF2 is the most important intermediate on the hydrodechlorination of CF2Cl2 was confirmed by the calculations. © 2009 The Author(s)