Catalytic upgrading of Biomass derived Oxygenate on Copper based Catalysts.

Abstract

Renewable production of propylene glycol (PG) has great interest. This can be produced from biomass derived chemicals instead of today s production, where PG is conventionally produced from petroleum derived chemicals.

Acetol, a product from biomass pyrolysis, was hydrogenated over different copper supported catalysts in order to produce propyleneglycol. Catalysts were prepared by impregnation and co-precipitation and consisted of copper on silica-, alumina-, ceria-, zirconiaand zinc-alumina oxide in addition to a hydrolatcate support. All catalysts were characterized with Temperature programmed reductio (TPR), X-ray diffraction (XRD), x-Ray fluorescence(XRF),Brunaer-Emmett-Teller(BET)method and Temperature gravimethirc analysis(TGA). Activity test were performed in a fixed bed reactorat 300◦C.

The reaction network is wide in range, as PC can further reacts to a variety of byproducts. Silica and aluminaoxide supported copper showed poor activity towards PG and suffered form overhydrogenolysis and deactivation. The remaining catalysts were further studied at different hydrogen partial pressure at a total pressure of 1.5 bar. Hydrogen positively influenced acetol conversion, but selectivity towards PG varied a lot between the supports, from 5 % to 70 % at 1 bar hydrogen. A few higher pressure experiments were conducted on zincalumina and hydrotalcite supported copper catalyst.

The 2 wt % copper on hydrotalcite was selected for further experiments. A basic catalyst isneededtoavoidfurtherreactionstopredominantlyacetone,whichmainlytakesplaceon the catalyst acid sites supported by the support. Acetone can further react to acetone condensationproducts(ACP),whichwasdominantwhensilica,aluminaorzirconiawasused as support. A kinetic study was performed and experiments were repeated at 200◦C and 250◦C. At 200◦C and 250◦C the PG selectivity increased to 95 %. As overhydroenolysys occurred at high temperature. Activation energy for acetol hydrogenation was found to be 48.5 kJ/mol, in reasonable agreement with previous reported literature.