Process simulation of the integration of molecular distillation with fast pyrolysis of biomass for sustainable fuel production

Biofuel produced from the fast pyrolysis of biomass waste can be used both to replace depleting fossil fuels and reduce environmental pollution. To improve biofuel properties, bio-oil produced by pyrolysis is fractionated using molecular distillation, which removes oxygen and converts the heavier components into lighter hydrocarbons appropriate for transportation fuels. Molecular distillation is a highly efficient separation technique widely used in industries requiring high-purity products. An increase in temperature generally enhances recovery rates but may reduce purity due to thermal degradation, while higher pressure improves purity by minimizing volatile losses but can slightly lower recovery rates. Here for the first time, we have investigated the integration of molecular distillation with fast pyrolysis of biomass as a promising route to upgrading bio-oil using process simulations to determine the optimal operating conditions that enhance product yield, purity, and recovery of specific chemicals of interest. A fast pyrolysis model was integrated with molecular distillation using ASPEN Plus software V12. The complex fast pyrolysis reactive system was analyzed and valuable insights into optimizing fast pyrolysis operating parameters and selectively isolating specific valuable chemicals was achieved. The effect of the temperature, pressure, and biomass types on the pyrolysis product yields and bio-oil compounds was also studied. Purity of up to 99.45% and recovery of 98.72% was achieved at the optimal operating conditions for levoglucosan. The molecular distillation unit selectively separated valuable bio-oil compounds of interest including levoglucosan, 4-vinyphenol, and p-hydroquinone. The mean free paths of the isolated compounds decreased with an increase in pressure and molecular diameter but increased slightly with temperature. By integrating biomass-fast pyrolysis with molecular distillation, there is an increase in process efficiency and selective prediction of the final product's yield. Moreover, it permits more precise isolation of chosen bio-oil compounds for different biomass waste and facilitates personalization in response to market needs.