Synopsis
The formaldehyde reduction activity of fired scallop-shell powder was investigated by means of
ab initio and density functional theory calculations. The two active components of fired scallop-shell powder are considered to be calcium oxide (CaO) and calcium hydroxide (Ca(OH)
2). In this study, finite-sized cluster models of these compounds were made and the interaction between each of them and formaldehyde (HCHO) was analyzed theoretically. Comparing the adsorption states of HCHO contained in the two models, one H atom of HCHO in the Ca(OH)
2-HCHO model was found to transfer to the adjacent O atom to form a Ca-OH-C-H-OH five-membered ring structure. This change would lead HCHO to decompose. By contrast, in the case of the CaO-HCHO model, HCHO attaches only through a Ca-O=CH
2-O bridged geometry and does not decompose. This result would indicate why Ca(OH)
2 is effective for HCHO reduction.
Key words: scallop shells, calcium oxide, calcium hydroxide, ab initio method, DFT method
