Open AccessSilica grain catalysis of methanol formation
Author(s) -
Goumans T. P. M.,
Wander Adrian,
Catlow C. Richard A.,
Brown Wendy A.
Publication year - 2007
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2007.12491.x
Subject(s) - adsorption , catalysis , quantum tunnelling , methanol , hydrogen , chemical physics , interstellar medium , physics , phase (matter) , chemistry , photochemistry , astrophysics , condensed matter physics , organic chemistry , quantum mechanics , galaxy
The specific catalytic effect of a silica grain on the formation of methanol via the sequential addition of H atoms to CO adsorbed on the surface is investigated. A negatively charged defect on a siliceous edingtonite surface is found to reduce the gas phase barriers for the H + CO ads and H + H 2 C=O ads reactions by 770 and 399 K, respectively, when compared to the same reactions in the gas phase. The catalytic effect of negatively charged surface sites could also be applicable to the hydrogenation of other adsorbed unsaturated species. However, the activation energies on the surface defect are still too large (1150 and 2230 K) for CH 3 OH to form efficiently at 10–20 K in the interstellar medium via a classical mechanism. It is therefore suggested that quantum mechanical tunnelling through the activation barrier is required for these hydrogen addition reactions to proceed at such temperatures. The calculations show that because the adsorption energies of CO and H 2 C=O on the negatively charged defect are substantial, CH 3 OH may form efficiently during the warm‐up period in star‐forming regions.