Gas Phase Transformation of (Bio) - Polyols into Carboxylic Acids by Means of Multifunctional Catalysis

The research activity carried out during the Ph.D aimed at the development of new synthetic routes for the production of acrylic and methacrylic acid using bio-alcohols as raw materials, respectively glycerol and propylene glycol. The first chapter of the thesis concerns the one-pot transformation of glycerol into acrylic acid, performed by using multifunctional catalysts. The overall process formally consists in two reaction steps: i) glycerol dehydration to acrolein, promoted by acid catalysis, and ii) acrolein oxidation to acrylic acid, promoted by redox catalysis. The design of suitable multifunctional catalysts is a complex matter and, so far, fundamental understanding behind the catalytic phenomenon remains unclear. In this context, the research work here reported aimed to shed light on the molecular-level relations that lie behind the catalytic results shown by several types of V-containing catalysts. The second chapter of the thesis concerns the study of a new synthetic route for the production of methacrylic acid starting from bio-propylene glycol. The overall process formally consists in three reaction steps: i) propylene glycol dehydration to propanal, ii) propanal oxidation to propionic acid, and iii) propionic acid condensation with formaldehyde, generated in-situ from methanol. Referring to reactions i) and ii), the research activity focussed on the possibility to perform the single-step gas-phase transformation of propylene glycol into propionic acid, by means of multifunctional catalysis (as previously done for glycerol one-pot transformation to acrylic acid). Finally, the study of the latter stage of the overall process to produce methacrylic acid was started, that is the condensation reaction between propionic acid and formaldehyde, generated in-situ from methanol. In particular, the catalytic activity of aluminium phosphate was fully investigated, so as to define the reactions that may occur when feeding propionic acid and methanol on pure acid catalysts.