Comparison between Catalytic Fast Pyrolysis and Catalytic Fast Hydropyrolysis of Arundo Donax in a Fluidized Bed Reactor

Abstract

In this work, we report the use of catalytic fast pyrolysis with HZSM-5 to convert Arundo Donax into liquid transportation fuels in an inert atmosphere, varying the temperature, the weight hourly space velocity (abbreviated WHSV, and defined as the feed rate of biomass divided by the weight of catalyst), and the pressure. We also introduced hydrogen gas as a reactant and investigated its effects on the yields at 35 bar and 400°C. Additionally, we added nickel to the HZSM-5 catalyst at loadings from 0.6 to 1.5 wt.% and investigated its effects on both catalytic fast pyrolysis and catalytic fast hydropyrolysis. Finally, we used a nickel-molybdenum HZSM-5 catalyst to determine if the molybdenum prevents the hydrocarbons from cracking to permanent gases. The goal is to understand the effects of these variables on the products of pyrolysis and increase the yield of fuel-like hydrocarbons. The highest yield of hydrocarbons in an inert atmosphere at atmospheric pressure was obtained at 550°C (11.6 C%). As we increased the WHSV, the yields of all products remained the same until the highest WHSV tested, 3.3 hr-1, at which point the yield of hydrocarbons decreased to 6.9 C%. Increasing the pressure increased the char and gas yields. The addition of hydrogen decreased the yield of coke and increased the yield of hydrocarbons at 400°C from 4.3 to 6.2 C%. Nickel decreased the yield of liquid hydrocarbons to 1.5 C% in hydrogen gas while greatly increasing the yield of gaseous hydrocarbons, especially methane, and water, though it had little effect in inert gas. Finally, we used nickel-molybdenum HZSM-5 to increase the yield of liquid hydrocarbons in catalytic fast hydropyrolysis to 7.9 C% at 400°C.