Advisor(s)
Abstract(s)
tLignin can be depolymerised and used as a feedstock to obtain renewable raw-materials,providing a green alternative to fossil counterparts. Among others, C4dicarboxylic acids(DCA), like succinic, malic, maleic and fumaric acids, which can find applications in phar-maceuticals, food industry, and act as solvents, can be obtained from lignin oxidation. Toinvestigate their formation, the oxidation of vanillic acid (VA), a lignin model compound, wasstudied under catalytic wet peroxide oxidation (CWPO) conditions, using titanium silicalite-1 (TS-1) as the catalyst. The effect of temperature, pH, and reaction time were studied. Ina second phase, catalyst modification with transition metal oxides (Fe, Co, Cu) was tested.Results showed that oxidation under pH = 10.5 gives rise to complete VA conversion withhydroxylated DCA, namely malic (15 mol%) and tartaric (5 mol%) acids, as the main products.At pH = 4.0, the production of succinic acid was improved (7.4 mol%), with VA conversionachieving 78% after 2.0 h of reaction. At alkaline pH, H2O2reactivity is higher, leading to C4-DCA degradation to low-molecular weight compounds. Catalyst desilication was observed,pointed out for the convenience of using neutral and acidic pH. In acidic pH, Fe and Cu cat-alysts enhanced VA conversion, and Fe catalyst was more selective towards succinic acidproduction.
Description
Keywords
Dicarboxylic acids Lignin oxidation Succinic acid Titanium silicalite-1 Wet peroxide oxidation
Citation
Vega-Aguilar, Carlos A.; Barreiro, M. Filomena; Rodrigues, Alírio E. (2020). Catalytic wet peroxide oxidation of vanillic acid as a lignin model compound towards the renewable production of dicarboxylic acids. Chemical Engineering Research and Design. ISSN 0263-8762. 159, p. 115-124