Computational Fluid Dynamics Investigation on Catalytic Hydrodeoxygenation of a Bio-Oil Model Compound in a Fluidized Bed Reactor

Abstract

Bio-oil produced from waste biomass by various thermochemical approaches possess several drawbacks primarily due to the presence of oxygenated compounds. These compounds render bio-oil difficult to be used as normal fuel for combustion. Thus, bio-oil must be processed to remove oxygenated compounds from it. One important process found suitable to deoxygenate bio-oil is the catalytic hydrodeoxygenation (HDO) using an appropriate catalyst. In literature, limited studies exist on the application of computational fluid dynamics (CFD) on hydrodeoxygenation of bio-oil model compounds. Therefore, authors utilized the computational fluid dynamics framework to delineate effect of process variables on the catalytic hydrodeoxygenation of 2-hydroxybenzaldehyde (2-HB) which is a bio-oil model compound in this study. The range of conditions considered herein are weight hourly space velocity (WHSV) = 1 h−1, 3 h−1, and 5 h−1; superficial hydrogen gas velocity, u = 0.075 m/s, 0.15 m/s, and 0.25 m/s; Pd/Al2O3 catalyst load = 0.06 kg and temperature, T = 498 K, 598 K, and 698 K. The present solution approach has also been applied to reproduce literature results on hydrodynamics of multiphase fluidized bed systems for comparison purpose. The hydrodynamics inside the fluidized bed reactor have been compared with and without HDO of 2-HB. The HDO of 2-HB yield phenol as the most dominant constitute of the products. Other products include benzene and benzaldehyde but in less fractions. Disclosing a few important results one can find that at constant low temperature (498 K), by increasing the values of WHSV the phenol fraction decreases, whereas those of benzene and benzaldehyde increases when u = 0.25 m/s. This effect becomes more rigorous at high constant temperature (698 K) especially in the case of phenol and benzene fractions. Moreover, most of the conversion of 2-HB and formation of products (phenol, benzene, and benzaldehyde) occurs within 2 s of fluidization time.