Catalytic hydrodeoxygenation of pyrolysis oil over nickel-based catalysts under H2/CO2 atmosphere

Abstract

Background: Renewable feedstocks and bio-refinery concepts are the key to a successful transition to a sustainable chemical industry. One conceivable refinery concept is based on pyrolysis oils from biomass, though these oils are quite difficult to handle. A well investigated approach to upgrade pyrolysis oil and turn it into a valuable products is catalytic hydrodeoxygenation (HDO). However, this process has to be optimized and new ideas are needed to make the hydrodeoxygenation process attractive sustainable and economically competitive. With regard to the many successful applications of gas-expanded liquids in heterogeneous catalysis, the expansion of pyrolysis oil with carbon dioxide was applied in the context of a hydrodeoxygenation reaction. The catalyst used for HDO was Ni/Al 2 O 3 (nickel loading 20 %wt). Results:The influence of CO 2 on the viscosity was found to be quite strong at low temperature. At 52 °C and a CO 2 pressure of 0.5 MPa the viscosity is reduced by 30 %. With 4.0 MPa of CO 2 the viscosity decreases by 60 %. With supercritical CO 2 a volume expansion of 5 % was observed. The hydrodeoxygenation showed best results at 340 °C and autogenous pressure. The experiments were started at a total pressure of 8.0 MPa at room temperature (H 2 + CO 2 ), with a respective partial pressure of CO 2 of 0 MPa, 2.0 MPa or 4.0 MPa. A deoxygenation degree of around 70 % could be reached (dry basis) under each atmosphere. The analysis of the upgraded products by different techniques indicated a slight decrease of hydrogenation with increasing the pressure of CO 2 .Conclusions: Despite we observed a change in the physical properties when expanding the pyrolysis oil with CO 2 , no real improvement of the catalytic hydrodeoxygenation reaction (e.g. deoxygenation degree) could be found yet. Possible reasons for the absence of gas-expanded liquid effects could be the polar nature of the used pyrolysis oil and the high temperature. We assume that a viscous and more tar-like, but less polar pyrolysis oil will be more influenced. Gas-expansion with CO 2 tends to be less effective with polar liquids due to the unpolar nature of CO 2 . The only observed effect in our actual system was a decrease of the hydrogenation with decreasing partial pressure of hydrogen.

Biofuels for Maritime Transportation: A Spatial, Techno-Economic, and Logistic Analysis in Brazil, Europe, South Africa, and the USA

“…In all regions, the highest biofuel production volumes were observed for HDPO. Notwithstanding, HDPO has not achieved commercial stage and is less mature than other biofuel technologies (Figure 21) [88][89][90][91][92][93]. Thus, investing in technologies that are closer to the commercialization stage in the near-to mid-term, may accelerate the uptake of maritime biofuels, despite their lower yields.…”

Catalytic decarboxylation of fatty acids to hydrocarbons over non‐noble metal catalysts: the state of the art

“…Hence, among the non‐noble monometallic catalysts studied for the DCX of fatty acids, Ni is the most interesting metal, as it is actually simultaneously active and selective. In addition, Ni‐based materials are cheap compared with other metal‐based catalysts, explaining the fact that they are the most commonly reported ones in the literature …”