Improving the stability and selectivity of furfural-to-aromatic catalytic process by co-feeding light alcohols

Abstract

This work demonstrates that green aromatics can be obtained with high selectivity by the gas-phase upgrading of furfural using ZSM-5. Furfural suffers a fast decarbonylation and cracking, yielding monoaromatics (benzene, toluene, xylene, BTX) and naphthalenes. The low stability of this system is significantly enhanced by co-feeding light alcohols (biomass derived platforms), also increasing the selectivity of aromatics. Ethanol increases the BTX production (up to 36.4 % at 550ºC), whereas maximum naphthalene selectivity is 14.9 % at 450ºC. Using methanol strongly promotes the naphthalenes production (40.7 % at 450ºC), without affecting the BTX one, yielding global selectivities up to 70 %. The stability of the catalytic process increases with the temperature, whereas the alkylation grade must be modulated to prevent both, undesired condensations of non-alkylated derivatives, and diffuse restrictions of polyalkylated derivatives (promoted when using methanol). The optimum equilibrium between these two opposite effects is reached with furfural-ethanol, achieving a stability 3.7 times higher than the one obtained when feeding only furfural. These results represent a significant improvement over the existing literature, both from the activity/selectivity and the stability points of view, describing a promising sustainable route for obtaining aromatics.