Optimization of Biomass Pyrolysis Vapor Upgrading Using a Laminar Entrained-Flow Reactor System

Abstract

A custom bench-scale continuous-flow catalytic fast-pyrolysis (CFP) reactor system was implemented for the optimization of ex situ CFP and screening of catalysts to gain insight into commercial scale ex situ CFP processes across various reactor types. Operated in an ex situ configuration, tandem laminar entrained-flow pyrolyzer and vapor-phase upgrading reactors were optimized to successfully demonstrate CFP of pine over two different commercial zeolite catalysts. Mixing-enhancers within the vapor-phase upgrader induced laminar flow dynamics with larger Reynold’s numbers, thus enhancing heat and mass transfer and in turn CFP conversion. Real-time analysis of products was accomplished via molecular beam mass spectrometry (MBMS), while light gas yield was determined using nondispersive infrared (NDIR) analysis. The transfer of the pyrolysis vapors to the vapor-phase upgrader was investigated to gain insight into optimal transfer-line conditions for limiting secondary thermal cracking and preserving carbon in the ex situ CFP process. The products were comparable to those previously obtained from fixed bed and fluidized bed reactor systems as well as entrained-flow riser reactor systems (e.g., one-ring aromatics, polyaromatics, and phenolics). Replicate experiments demonstrated a good average mass balance closure: 14 wt % oil, 27 wt % aqueous, 26 wt % char, 12 wt % total coke (system and catalyst coke), and 21 wt % light gas (CO, CO2, and CH4) with overall closure of ∼100%. Similar trends in catalyst deactivation were observed for the laminar entrained-flow reactor system with decreasing catalyst-to-biomass ratio as reported in the literature. Under optimized continuous-flow conditions, constant catalyst activity was maintained, suggesting that the laminar entrained-flow reactor system was a viable option for the CFP of pine. Minor differences in catalytic activity were observed for the two catalysts tested.