Praktické výstupy (přehled)

Europe legislative requirements contain three major targets for the next three decades: reducing greenhouse gas emission, generating renewable energy and increasing energy efficiency. Biomass transformation to required biofuels is affording to reach these demands. Industrial production of hydrocarbons suitable for biodiesel already inquires revision of some technical aspects such as substitution of noble-based or sulphur containing catalysts. Hydrotreating of vegetable oils includes deoxygenation stage as the most important which adapts produced fuels for direct use in diesel engines. Hydrodeoxygenation (HDO) of stearic acid (SA) as a model reaction is commonly used to investigate chemical transformations of biomass when developing new catalytic systems. Transition metal nitrides, carbides, and phosphides exhibit properties similar to noble metals due to increasing the metal-metal bond distance by incorporation of corresponding ions into a MeOx framework. In this study, bulk molybdenum-based materials were prepared by the temperature-programmed reduction method (H2/N2 or CH4/N2 flow at 700-900 °C) followed by passivation with oxygen. Influence of various precursors on phase composition and catalytic activity of produced samples was examined in HDO of SA under H2 pressure (50 bar) in batch conditions using a Parr autoclave (360 °C, 700 RPM). Catalytic results and product distribution were correlated with physicochemical and textural properties analysed by XRD, N2-adsorption, H2-TPR, TEM, and SEM techniques and compared to traditional catalysts. The presence of hexamethylenetetramine in the precursor mixture positively influenced the phase composition and ensured the synthesis of pure Mo2N, Mo2C, and MoP. The total degree of deoxygenation over the fresh catalysts decreased in the order Mo2C > Mo2N > MoP where the carbide, characterized by the largest surface area, reached 91% deoxygenation at 98 % SA conversion after 4 h, however reusing the phosphide sample in the second catalytic cycle exhibited >99% at a total feedstock conversion. The obtained results suggest a high potential of molybdenum-based systems as alternative catalysts for application in hydrodeoxygenation processes essential for biomass upgrading.