Customized Atmospheric Catalytic Hydropyrolysis of Biomass to High-Quality Bio-Oil Suitable for Coprocessing in Refining Units

Abstract

This study aimed to investigate the critical elements of the biomass ex situ catalytic hydropyrolysis (CHP) concept to improve the quality of fast pyrolysis bio-oil (FPBO) for further coprocessing in a fluid catalytic cracking (FCC) refining unit. Generally, the high oxygen and low hydrogen contents of biomass result in a bio-oil with low quality, necessitating its upgrading, which can be performed as integrated in the pyrolysis process via in situ or ex situ configuration. In this work, the quality of stem wood-derived pyrolyzates (520 °C) was improved via ex situ CHP (400 °C) using a continuous bench-scale drop tube pyrolyzer (60 g h −1 ), and then the produced FPBO was coprocessed with vacuum gas oil (VGO) fossil oil using a lab-scale FCC unit (525 °C). CHP of stem wood was carried out using different metalacid catalysts such as Ni/HZSM-5, Ni/HBeta, Mo/TiO 2 , and Pt/TiO 2 at atmospheric pressure. FCC runs were performed using an equilibrium FCC catalyst and conventional fossil FCC feedstock cofed with 20 wt % stem woodderived bio-oil in a fluidized bed reactor. Cofeeding the nonupgraded FPBO with fossil oil into the FCC unit decreased the generation of hydrocarbons in the range of gasoline and naphtha, indicating that bio-oil needs to be upgraded for further coprocessing in the FCC unit. Experimental results showed that different catalysts significantly affected the product composition and yield; Ni-based catalysts were strongly active tending to generate a high yield of gas, while Mo-and Pt-based catalysts seemed better for production of liquid with improved quality. The quality of FPBO was improved by reducing the formation of reactive oxygenates through the atmospheric CHP process. The composition of oil obtained from hydropyrolysis also showed that the yields of phenols and aromatic hydrocarbons were enhanced.