Abstract
Residual biomass shows potential to be used as a feedstock for fast pyrolysis bio-oil production for energetic and chemical use. Although environmentally advantageous, further catalytic upgrading is required in order to increase the bio-oil stability, by reducing reactive compounds, functional oxygen-containing groups and water content. However, bio-oils may separate in fractions either spontaneously after ageing or by fractionated condensation. Therefore the effects of upgrading on different fast pyrolysis bio-oil (FPBO) fractions obtained from a commercially available FPBO were studied by elemental analysis, GC-MS and 1H-NMR. Not only the FPBO was upgraded by catalytic hydrotreatment, but also the heavy phase fraction formed after intentional aging and phase separation. The reactions were conducted between 175 and 325 °C and 80–100 bar by using a nickel–chromium catalyst in batch experiments. The influence of the hydrotreatment conditions correlated with the composition of the upgraded products. Higher oxygen removal was obtained at higher temperatures, whereas higher pressures resulted in higher hydrogen consumption with no significant influence on deoxygenation. At 325 °C and 80 bar 42% of the oxygen content was removed from the FPBO. Compounds attributed to pyrolysis oil instability, such as ketones and furfural were completely converted while the number of alcohols detected in the upgraded products increased. Coke formation was observed after all reactions, especially for the reaction with the fraction rich in lignin derivatives, likely formed by polymerization of phenolic compounds mainly concentrated in this phase. Independently of the feedstock used, the upgraded bio-oils were very similar in composition, with reduced oxygen and water content, higher energy density and higher carbon content.
Highlights
The use of lignocellulosic biomass, especially residual biomass as a potential replacement for fossil resources has attracted the attention of the scientific community in the1 3 Vol.:(0123456789)Topics in Catalysis (2018) 61:1769–1782 last years
Comparing firstly the reaction performed at 175, 225 and 275 °C with fast pyrolysis bio-oil (FPBO), the oil yield slightly increased with the increase of temperature for reactions performed at 80 bars whereas a small reduction in the oil yield was observed at 100 bars
The complete beech wood pyrolysis-oil and the isolated heavy phase were upgraded at different conditions of temperature and pressure applying a nickel chromium catalyst
Summary
The use of lignocellulosic biomass, especially residual biomass as a potential replacement for fossil resources has attracted the attention of the scientific community in the. Various lignin derivative compounds i.e. phenol and guaiacol are present, limiting its direct application as fossil fuel replacement [5,6,7]. The amount of these compounds is dependent on various parameters, in particular, the selected biomass as well as its moisture content. Very convenient, considering the current application of these catalysts in refineries [7], sulphided catalysts are rapidly deactivated by water and coke formation [6, 13] and may introduce sulfur into the product Another category of catalysts that has been in the focus of many studies are heterogeneous non-noble metal catalysts. Using a nickel chromium based catalyst we report the influence of temperature and pressure on the HDO activity
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