Advanced technologies for the reduction of the carbon footprint in the reforming of bio-oil over NiAl2O4 derived catalyst

Abstract

This Thesis focuses on the reduction of the carbon footprint in bio-oil reforming by two alternative strategies: i) sorption enhanced steam reforming (SESR), which minimises CO2 emissions by in situ CO2 capture and enhances H2 production, and ii) combined steam/dry reforming (CSDR, with H2O and CO2 as reactants) process for syngas (H2+CO) production with joint CO2 valorization. For the SESR of bio-oil, the selection of the most suitable sorbent (dolomite or CaO/mayenite) ¿ catalyst (Ni/Al2O3 derived from NiAl2O4 spinel or Ni/CeO2 prepared by wet-impregnation) pair was first studied. Then, for the optimum system (Ni/Al2O3+dolomite), the performance of packed-bed and fluidized-bed reactors and the effect of operating conditions (temperature, space time, sorbent/catalyst ratio) and cyclic operation (reaction-regeneration, with joint regeneration of the catalyst and sorbent) were studied. Regarding the CSDR, a thermodynamic study (with ProII software) of a simulated bio-oil and an experimental study of a real bio-oil with the Ni/Al2O3 catalyst were addressed, analysing the effect of temperature, feed composition (S/C and CO2/C molar ratios) and space time. As a preliminary step to better understand the results obtained with the previous strategies (SESR and CSDR) on catalyst deactivation, the role of individual oxygenated compounds in bio-oil reforming was studied both thermodynamically (using ProII software) and experimentally with the Ni/Al2O3 catalyst. As a relevant result, the importance of phenolic compounds (mainly guaiacol) in catalyst deactivation by amorphous coke deposition is highlighted.