DFT screening of adsorption of biodiesel molecules on aluminum and stainless steel surfaces

We present a Density Functional Theory (DFT) study of the adsorption of small organic molecules, taken as models of biodiesel autoxidation products, on stainless steel and aluminum surfaces. The anhydrous and fully wetted (0001) α-Al2O3 and α-Cr2O3 surfaces were taken as models for aluminum and stainless steel surfaces, respectively. Only on the anhydrous surfaces, a clear ranking in adsorption energy is observed: carboxylic acid > methyl esters > alcohol ∼ketone > aromatics > alkanes. The different surfaces reactivity range in the order anhydrous Al2O3 > anhydrous Cr2O3 > ∼hydroxylated Al2O3 and Cr2O3. Calculated desorption temperatures show that only on aluminum-based surfaces some of the investigated organic molecules remain adsorbed at operational conditions (500 K).