J.R.B. Gomes and J.A.N.F. Gomes

CEQUP/Faculdade de Ci�ncias da Universidade do Porto

Rua do Campo Alegre, 687

4150 Porto - Portugal

email: [email protected]

Heterogeneous catalysis is permanently relevant and it continues to be deeply enigmatic. More than 90% of the chemical manufacturing processes in use throughout the world use catalysts; for example, almost all the fuels used by transport facilities (cars, planes, etc.) are produced by heterogeneously catalysed reactions. The science and technology of catalysis are therefore of central practical importance. However, when we recall that, until recently, the majority of commercially significant catalysts were discovered and developed principally by empirical methods, we appreciate how much more remains to be learned about the principles and manifestations of catalysis. Rational design of certain kinds of catalysts and chemical engineering processes, thanks to very recent advances, is now a reality. These advances result from several experimental and theoretical studies.

One key feature of theoretical chemistry is that, possibly alone among all other techniques, it can in principle cope with the structural elucidation of surface intermediates with lifetimes and concentrations too small for direct experimental study. Theoretical chemistry has made its impact in other ways, specially in offering unifying interpretative frameworks for rationalising the performance of known catalysts and in attempting to design new ones. Organic reactions catalysed by transition metal surfaces are a case to notice. The effect of surfaces composed by more than one element (oxides, alloys, etc.), different Miller indices, coadsorbed species, etc., are still subject of an intense study.

The aim of our work is the elucidation of how methanol (CH3OH) oxidation takes place. For that purpose, we use quantum chemical calculations with the density functional theory (DFT) methodology to study the adsorption of small CO-containing molecules on copper, silver and gold surfaces. We have studied how molecules such as the methoxy radical (CH3O), formaldehyde (H2CO), dioxymethylene (H2CO2), formate (HCO2) and, of course, methanol, adsorb on these surfaces. The interest on the copper group is due to the use in chemical industry of a copper/zinc oxide catalyst to obtain methanol from syn-gas and of a silver catalyst to the production of formaldehyde from methanol.

In this poster, results from DFT calculations using the B3LYP hybrid method will be presented and compared, where possible, with experimental data.

We thank JNICT and PRAXIS XXI for financial support.