Synthesis of Chitosan:UiO-67 Beads and Preliminary Catalytic Testing using Methanol Conversion

Abstract

Composites of chitosan (CS), an abundant biopolymer derived from the exoskeletons of crustaceans, and UiO-67, a metal organic framework (MOF) which exhibits high chemical and thermal stability, were drop-casted in different ratios using an acetic acid solution in an attempt to produce stable beads which may be used for useful applications such as catalysis. The CS, MOF, and composite beads were characterised using ATR-IR spectroscopy, XRD, SEM-EDX, and N2 physisorption. CO-IR was used to identify the presence of catalytic acid sites on the MOF while TGA was used to study the thermal properties of the MOF, CS and composite beads. The results of these characterisations indicated that bead drop-casting using the acetic acid solution was degrading the MOF structure. Stability tests in acetic acid were conducted to study the effects of acetic acid on the MOF structure. Methanol (MeOH) conversion was chosen as a test reaction which was carried out on the pure MOF and CS:MOF beads to study the catalytic acid sites of the MOF and how they are affected when combined with CS in a bead. MeOH conversion is also an environmentally relevant process since MeOH can be converted into dimethyl ether (DME) which can be used as an alternative fuel source to conventional liquid petroleum gases. Mechanical degradation was seen when preparing the MOF for catalysis. MeOH conversion was observed in the MOF and a 1:4 CS:MOF ratio bead. Two unknown products were formed during MeOH conversion most likely as a consequence of the MOF being degraded by the acetic acid solution in drop-casting. Further in-situ data of these products and the effects of catalysis are needed, however.