Valorization of citric waste: use as support of heteropolyacid in the catalytic oxidation of sulfides

V. PALERMO; P.G. VÁZQUEZ.; M.B. COLOMBO MIGLIORERO

San José

Congreso; IV National Nanotechnology and Polymer Congress - 7th Workshop Green Chemistry and Nanotechnologies in Polymer Chemistry; 2016

Heteropolyacids (HPAs) is a field of increasing importance worldwide, especially in catalysis by replacement of inorganic acid catalysts such as sulfuric, hydrofluoric or hydrochloric acids, which produce toxic waste and require drastic reaction conditions. The use of Keggin and HPAs as catalysts has many advantages; for example, they are noncorrosive, cheap and environmentally friendly. HPAs possess a very strong acidity and appropriate redox properties. However, their solubility in polar solvents and the low specific area of bulk HPAs limit their use as heterogeneous catalysts. The utilization of heterogeneous catalysts is more advantageous over homogeneous catalysts, mainly because they can be easily recovered from the reaction mixture by simple filtration procedures and then reused after activation, thereby making the process economically viable. Our researched group has studied different ways to convert in a heterogeneous catalyst the HPAs1, being the inclusion of HPAs in a matrix silica, during the sol-gel process, one of the best strategies2. On the other hand, since a lot amount of citric waste are generated in the orange juice industry, here we present the valorization of these residues, including orange peel (OP) into the catalyst.Firstly, OP was thermally treated (100 and 200 ºC), and then incorporated during the silica synthesis, using TEOS, ethanol and water, by sol-gel method. Also, PMo (H3PMo12O40) was incorporated in this process. Therefore, SiO2-PMo, SiO2-OP100-PMo, and SiO2-OP200-PMo were obtained.The prepared solid were characterized by FT-IR, SBET, XRD, potentiometric titration, and were tested as heterogeneous catalyst in the selective oxidation of diphenyl sulfide to diphenyl sulfoxide (Scheme 1), in a greener process: aqueous H2O2 as oxidant, ethanol as solvent at room temperature.