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Employing renewable sources from vegetal oil to produce chemicals and energy appears to be one of the most important technological approaches to solve the need for replacement of oil. In this way, the new concept of bio-refineries to produce energy and derivatives from biomass comes into the picture. When obtaining biodiesel from biomass conversion, about 10 % of the reaction by-product is glycerol. Thus, it is accepted that glycerol will play a very important role in bio-refineries future and it is, therefore, mandatory to search for new processes to upgrade this by-product into more valuable chemicals.
Glycerol is a highly functionalized compound which could be used as a starting material for a great variety of chemical products of industrial interest. One of the interesting upgrades for glycerol is to produce propylene glycol by dehydration followed by hydrogenation. In another aspect, glycerol can be selectively oxidized, in acid or basic conditions, to different products of interest depending if the targeted hydroxyl is in primary or secondary position. Furthermore, glycerol can be reacted with metal catalysts to obtain H2 and CO (reforming reactions).
We have studied the chemistry of glycerol on Pd(111) as a model metal catalyst for the aforementioned reactions. Using a combination of IRAS, XPS and TPD, we study the adsorption and further decomposition of the polyol and are able to distinguish adsorbed intermediates in-situ. When the polyalcohol is adsorbed on the metallic surface it is found that it primarily decomposes into H2 and CO, as expected when using Pd as a reforming catalyst, with traces amount of formaldehyde and methane. Preliminary results regarding influence on the chemistry observed in the presence of chemisorbed oxygen or surface oxide thin film will be presented. These later results are of interest to understand the mechanistic processes of selective catalytic oxidation of glycerol.
