Browsing by Author "Karinen, Reetta, Dr., Aalto University, Department of Chemical and Metallurgical Engineering, Finland"

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  • Carbon Catalysts in Biofuel Production: from Furfural to 2-Methylfuran
    (2019) Jaatinen, Salla
     School of Chemical Engineering | Doctoral dissertation (article-based)
    Production of bio-based chemicals, fuels and energy are essential in the current climate environment. Hydrotreatment of renewable platform chemical furfural yields many valuable products, such as furfuryl alcohol and 2-methylfuran (MF). MF has excellent properties for use as a gasoline octane booster to replace current fossil methyl tert-butyl ether and ethyl tert-butyl ether. The current CuCr-catalyst in furfural hydrotreatment is toxic and new and selective catalysts are required. In this dissertation, noble metal free and non-toxic catalysts were prepared for production of MF. Metal catalyst options chosen for this work were copper, nickel and iron. High yields (up to 60%) of MF were achieved with the prepared catalysts in liquid phase batch reactor experiments in short reaction time (1 - 2 h). High temperature (230 °C) and high hydrogen partial pressure (40 bar) were optimal for MF produc-tion, and the most optimal metal combinations were copper-nickel and copper-iron. Active metals were tested in MF production on various activated carbon supports and a mesoporous carbon material (CMK-3). Deep characterization was performed to obtain data of beneficial catalyst characteristics for MF production. Production of MF was enhanced by small metal particle size, small pore volume and higher acidity. These enhancements suppressed the production of competitive products and side reactions, and increased the selectivity towards 2-methylfuran. Solvents may also react in furfural hydrotreatment. The applied 2-propanol can react through catalytic transfer hydrogenation (CTH) offering hydrogen for hydrotreatment reactions and producing acetone. The solvent can also dehydrogenate to acetone and hydrogen. Acetone formation mechanisms were studied with the prepared catalysts. The acetone formation was metal dependent: with nickel and copper acetone formation occurred through CTH while with iron also dehydrogenation took place. Hydrogen solubility in the reaction media is important for the process and especially in scaling up pro-cesses. Hydrogen solubilities in furfural and 2-propanol were measured and observed to increase as a function of temperature (50 - 200 °C) and pressure (50 - 125 bar). Hydrogen solubility in 2-propanol was observed almost three times higher to solubility in furfural. By way of example, at 200 °C and 125 bar hydrogen mole fraction in 2-propanol and furfural was measured to be 0.064 and 0.038 respectively. The solubility data was modelled with PC-SAFT model and the model predicted the hydrogen solubility data well. This dissertation offers a MF selectivity optimized and fast noble metal free catalyst alternative for the current catalyst, new data of hydrogen solubility in the reaction media and optimized carbon support characteristics for the production of MF.
  • Noble metal catalysts for the hydrodeoxygenation and hydrodenitrogenation of fatty amides
    (2024) Verkama, Emma
     School of Chemical Engineering | Doctoral dissertation (article-based)
    The development of active catalysts for simultaneous hydrodeoxygenation (HDO) and hydrodenitrogenation (HDN) is important for the processing of renewable feedstocks to fuels. In this thesis, the hydrotreatment of fatty amides and their derivatives was studied on supported noble metal catalysts. Studies on competitive HDO and HDN reactions in the co-hydrotreatment of palmitic acid and 1-tetradecylamine over Pt/ZrO2 indicated that HDO proceeded more efficiently than HDN on all studied feed compositions. The preferential HDO of the oxygen-containing compounds and formation of secondary amides and amines via condensation reactions inhibited the HDN of 1-tetradecylamine in the co-hydrotreating experiments. The hydrotreatment of n-hexadecanamide was studied in a batch reactor at 300 °C and 80 bar H2, over Pt catalysts supported on SiO2, Al2O3, SiO2-Al2O3, TiO2, Nb2O5, ZrO2 and CeO2-ZrO2, as well as Pd, Rh, Ru and Ni supported on ZrO2. The Lewis acid properties of the support influenced the activity and selectivity towards the initial n-hexadecanamide conversion route, and the conversion of the oxygen-containing intermediate products. The oxygen-containing intermediate products were converted particularly efficiently on Pt/CeO2-ZrO2, which was attributed to the weak Lewis acid sites on the reducible support. The active metal influenced the activity and selectivity for condensation reactions and for the formation of n-pentadecane and n-hexadecane from the intermediate products. HDO proceeded more efficiently than HDN on the studied catalysts. Finally, monometallic and bimetallic catalysts supported on CeO2-ZrO2 were prepared, characterized and tested for their activity in the hydrotreatment of n-hexadecanamide. The catalytic properties of the bimetallic catalysts were markedly different compared to the corresponding monometallic catalysts, which, based on the characterization, appeared to be due to interactions between the active metals. The combination of Ni with a noble metal was particularly beneficial for the catalytic activity, and the RuNi/CeO2-ZrO2 catalyst exhibited the highest activity and selectivity towards the formation of n-pentadecane out of the catalysts studied in this thesis. The results of this thesis brought new insights into the influence of the catalyst composition on the activity, selectivity and reaction network in the hydrotreatment of fatty amides to n-paraffins.