Catalytic fast pyrolysis of lignocellulosic biomass in a process development unit with continual catalyst addition and removal

Abstract

Catalytic fast pyrolysis (CFP) of wood was studied using a spray-dried ZSM-5 catalyst in a process development unit (PDU) consisting of a bubbling fluidized bed reactor with on-stream particle input and output. The PDU was capable of maintaining constant product yield of aromatics over an extended reaction period (6h) with continuous catalyst addition and removal. The yields and selectivity for aromatics and olefins were dependent on temperature, biomass weight hourly space velocity (WHSV), catalyst to biomass ratio, fluidization gas velocity, and catalyst bed weight. The overall aromatic yield increased up to 15.5 carbon% with decreasing gas velocities due to the increased vapor residence time and the improved mass transfer from smaller bubble sizes. A simulated recycle stream of CFP product gases consisting of CO, CO2 and olefins was used to test the viability of subsequent olefin aromatization in the presence of CO and CO2. Olefins were converted into additional aromatics while CO and CO2 remained inert during CFP. The spray-dried ZSM-5 catalyst was stable in a series of 30 reaction/regeneration cycles.