Aaltodoc Repository :: Browsing by Author "Puurunen, Riikka L., Assoc. Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland"

Browsing by Author "Puurunen, Riikka L., Assoc. Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland"

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Catalytic Aqueous-Phase Reforming of Biorefinery Water Fractions
(Aalto University, 2021) Coronado, Irene; Reinikainen, Matti, Dr., VTT Technical Research Centre of Finland, Finland; Lehtonen, Juha, Prof., VTT Technical Research Centre of Finland, Finland; Kemian tekniikan ja metallurgian laitos; Department of Chemical and Metallurgical Engineering; Kemian tekniikan korkeakoulu; School of Chemical Technology; Puurunen, Riikka L., Assoc. Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland
Biorefineries can produce renewable fuels and chemicals through processes such as pyrolysis of lignocellulosic biomass or Fischer-Tropsch (FT) synthesis using syngas derived from biomass gasification. Although commercial-scale plants exist, the production costs of renewable fuels and chemicals are usually higher than the production costs of fossil-based fuels and chemicals. To improve the competitiveness of biorefineries, this thesis proposes processing the water fractions derived from biorefineries to optimise the production of renewable fuels and chemicals. Biorefinery water fractions include diluted oxygenated hydrocarbons that can be processed using aqueous-phase reforming (APR) technology to produce hydrogen, which is the main desired product, and other gases such as carbon dioxide, carbon monoxide and alkanes. This study tested different Ni-based catalysts, first in the APR of model compounds representative of pyrolysis liquid aqueous fraction (PLAF) and FT waters, and finally, in the APR of a real water fraction derived from FT synthesis. The APR of model compounds representative of PLAF, i.e. solutions of acetic acid, ethanol, 1-hydroxypropan-2-one and benzene-1,2-diol, resulted in low hydrogen yields and significant deactivation of different Ni-based catalysts. The hydrogen yield was around 10% from ethanol and close to 1% from the other oxygenates. The APR of FT water model compounds, i.e. solutions of C1-C4 alcohols over Ni-based catalysts, yielded relatively high amounts of hydrogen, ranging from 13% to above 100%, and 11% in the APR of real FT water. A copper-doped nickel catalyst supported on ceria-zirconia was selected to conduct the APR of real FT water under different operation conditions. The results were utilised to develop a kinetic model that could be applied through concept development to integrate APR into a FT synthesis process.The hydrogen produced in the APR of FT water could be used in the production of renewable fuels and chemicals to improve their production efficiency. Nickel-copper/ceria-zirconia catalyst is a suitable catalyst to process FT waters. Nonetheless, the catalyst composition should be further optimised to increase the hydrogen yield.
Conformality of atomic layer deposition analysed via experiments and modelling: case study of zinc oxide for catalytic applications
(Aalto University, 2024) Yim, Jihong; Puurunen, Riikka L., Assoc. Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland; Karinen, Reetta, D.Sc. (Tech.), Aalto University, Department of Chemical and Metallurgical Engineering, Finland; Kemian tekniikan ja metallurgian laitos; Department of Chemical and Metallurgical Engineering; Catalysis Research; Kemian tekniikan korkeakoulu; School of Chemical Technology; Puurunen, Riikka L., Assoc. Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland
Atomic layer deposition (ALD) has been used in various applications including microelectronics and heterogeneous catalysts. Ideally, ALD enables the growth of homogeneously distributed materials on solid supports including high aspect ratio (HAR) structures. However, to ob-tain conformal ALD coatings on HAR structures, process conditions should be optimized. The goals of this work were (i) to develop and apply a zinc oxide ALD process to prepare diverse copper-zinc oxide on zirconia catalysts for carbon dioxide hydrogenation into methanol and (ii) to investigate the effect of various process parameters on ALD conformality. Zinc oxide was added on mesoporous zirconia and alumina particles by the reaction of zinc acetylacetonate in a fixed bed ALD reactor. After the reaction, the remaining acac ligands were oxidatively removed in synthetic air at elevated temperatures. The reaction of zinc acetylacetonate on zirconia showed self-terminating behavior with the areal number density of zinc of approximately two atoms per square nanometer. The steric hindrance of bulky acac ligands was likely a saturation-determining factor for zinc obtained by ALD. Meanwhile, an eggshell-type zinc coating was obtained on alumina, and the zinc loading increased when the reactant dose increased. A diffusion–reaction model adapted to spherical supports was used to simulate the effect of reactant exposure on zinc loading. In the simulation, the zinc loading increased with an increase in the reactant exposure. The simulation results fit well with the experimental results. The zinc-after-copper catalyst was superior compared to other copper-after-zinc or copper-only catalysts for carbon dioxide hydrogenation into methanol. The current research showed the importance of tuning of the interaction of zinc and copper for catalytic performance and demonstrated the potential of zinc acetylacetonate as an ALD reactant. For future ALD conformality studies, a benchmark was proposed using an archetypical trimethylaluminum-water process on lateral HAR microchannels. The effect of process parameters on ALD thickness profiles was investigated using a diffusion–reaction model. For example, penetration depth into microchannels decreased with an increase in the molar mass of ALD reactant and growth per cycle (GPC). The trends of ALD thickness profiles in the free molecular flow regime and transition flow regime were illustrated. This work proposes that the free molecular flow regime and channel filling of less than 5% are the conditions required to obtain fingerprint thickness profile characteristics.
Hydrotreatment of lignocellulose-derived molecules to renewable fuels and chemicals
(Aalto University, 2021) Mäkelä, Eveliina; Karinen, Reetta, Dr., Aalto University, Finland; Lindblad, Marina, Dr., Neste Corporation, Finland; Kemian tekniikan ja metallurgian laitos; Department of Chemical and Metallurgical Engineering; Catalysis Research Group; Kemian tekniikan korkeakoulu; School of Chemical Technology; Puurunen, Riikka L., Assoc. Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland
Lignocellulose is an abundant, non-edible source of biofuels and biochemicals. It can be processed into several platform molecules, such as furfural, levulinic acid (LA), and phenols. In this thesis, the hydrotreatment of lignocellulose-derived molecules to obtain biofuels and renewable chemicals was studied using batch reactors. Instead of traditional hydrotreatment catalysts (sulfided NiMo and CoMo on γ-Al2O3) and toxic copper chromite (industrial furfural hydrotreatment), noble and base metal catalysts on metal oxides as well as on bio-based carbon supports were used. Furfural hydrotreatment to 2-methylfuran (MF) was conducted using Pt, Ru, and Ni catalysts on wood-based activated carbons (ACs) from spruce and birch and with Cu/Ni catalysts on bio-based activated carbon foams (ACFs) from tannic acid and pine bark extracts and on spruce-based AC. The highest MF yields of 49%–58% were obtained with 1.5–3 wt.% Pt and Ru catalysts and with 5/5 wt.% Cu/Ni catalyst on ACs in liquid phase at 230–240 °C and 40 bar H2 pressure. The suitability of ACFs as catalyst supports was also confirmed, and MF selectivity was increased by acid treatments. The important catalytic factors affecting the MF selectivity were metal particle size and dispersion as well as the support's porosity and surface groups. Hydrotreatment of LA dimers was first studied with a model compound, γ-nonalactone, using 3 wt.% Pt, Pd, Ru, and Rh catalysts on ZrO2 at 280 °C and at an average pressure of 57.5 bar H2. The highest selectivity to hydrocarbons (nearly 24%) was obtained with the Ru catalyst. The initial conversion of the catalysts (Rh >> Ru) correlated with the amount of detected surface metal atoms. Further, the hydrotreatment of LA dimers was demonstrated with a 3.6 wt.% Ru/ZrO2 catalyst at 250–300 °C and 47.5 bar average H2 pressure to obtain increased carbon-chain-length (>C6) products. Deoxygenation, the formation of volatile products, and the formation of aromatics increased at high temperature. The volatile products mainly comprised not only acids, esters, and ketones but also linear, branched, and cyclic hydrocarbons. Hydrotreatment of 4-propylphenol to propylbenzene was studied with 3 wt.% Pt catalysts on Nb2O5, TiO2, and ZrO2 supports in liquid organic phase at 350 °C and 20 bar H2 pressure. The highest selectivity of 77% at 98% conversion level was obtained with the Pt/Nb2O5 catalyst. Nb2O5- and TiO2-supported catalysts had activity superior to ZrO2-supported catalyst, which was thought to be attributable to oxophilic sites created during catalyst reduction. In this thesis, high MF yields were obtained using catalysts on wood-based ACs. To the best of the author's knowledge, AFCs were tested as catalyst supports, for the first time. Moreover, the hydrotreatment of LA dimers with Ru catalyst was demonstrated, which offers a new route from lignocellulosic sugars to increased carbon-chain-length products. Finally, high selectivity to propylbenzene was obtained from 4-propylphenol; this is among the best results reported in the liquid-phase hydrotreatment of phenols.
Noble metal catalysts for the hydrodeoxygenation and hydrodenitrogenation of fatty amides
(Aalto University, 2024) Verkama, Emma; Karinen, Reetta, Dr., Aalto University, Department of Chemical and Metallurgical Engineering, Finland; Tiitta, Marja, Dr., Neste Corporation, Finland; Kemian tekniikan ja metallurgian laitos; Department of Chemical and Metallurgical Engineering; Catalysis Research Group; Kemian tekniikan korkeakoulu; School of Chemical Technology; Puurunen, Riikka L., Assoc. Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland
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.
Structured microreactors for the heterogeneously catalyzed gas-phase dehydration and partial oxidation of 1-butanol
(Aalto University, 2020) Khan, Yaseen; Karinen, Reetta, Dr., Aalto University, Finland; Lehtonen, Juha, Prof., VTT Technical Research Center of Finland, Finland; Kemian tekniikan ja metallurgian laitos; Department of Chemical and Metallurgical Engineering; Industrial Chemistry and Catalysis; Kemian tekniikan korkeakoulu; School of Chemical Technology; Puurunen, Riikka L., Assoc. Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland
Structured microreactors are considered as a tool to study catalytic activity and intrinsic kinetics because of their characteristic mass and heat transfer advantages. In this thesis, microreactor structures coated with catalysts (γ-Al2O3, Au/TiO2, Pd/TiO2 and Au-Pd/TiO2) were applied to study the activity and to investigate the kinetics of the heterogeneously catalyzed gas-phase reactions in dehydration and partial oxidation of 1-butanol. In addition, the morphology and durability of the prepared noble metal catalyst coatings (Au/TiO2, Pd/TiO2 and Au-Pd/TiO2) were studied. A structured microreactor coated with γ-Al2O3 catalyst having a layer thickness of 15-30 µm was used for the heterogeneously catalyzed gas-phase dehydration of 1-butanol. The kinetic parameters were estimated from the produced experimental data. A dynamic 2D plug ﬂow reactor type model with diffusion-reaction in the catalyst layer conﬁrmed insigniﬁcant internal mass transfer resistances and prevalence of the kinetic regime. A computational ﬂuid dynamics study using 3D and 2D-axisymmetric models incorporating ﬂuid ﬂow non-idealities, revealed the presence of axial and radial concentration gradients. The insights from the simulations revealed the catalyst layer thickness and the microchannel dimensions as key parameters to improve the performance of microreactors applied for the heterogeneously catalyzed gas-phase reactions. New heterogeneous catalyst coatings of titania-supported mono- and bimetallic gold and palladium were prepared and tested for the 1-butanol partial oxidation. A sol-immobilization method was used for catalyst preparation and coatings were prepared via a suspension method. A layer thickness of 17±7 µm with an average metal nanoparticle size of 3.6 nm was achieved. The Au/TiO2 catalyst coatings were most selective towards n-butyraldehyde, whereas Pd/TiO2 and Au-Pd/TiO2 catalysts were more selective towards propene, CO and CO2. The kinetic experiments were performed using Au/TiO2 coated catalyst. Kinetic modeling was performed by applying 1D-pseudohomogeneous plug ﬂow reactor type model and dynamic 2D model incorporating axial dispersion effects in gas-phase. The model simulations reproduced the experimental data. In this thesis, preparation of active, selective and durable Au/TiO2 coated catalysts was demonstrated. The activity of the prepared Au/TiO2 coated catalyst was reproducible for 57 tested runs that is reported, in the author's knowledge, for the ﬁrst time for the nanogold catalyst. In addition, kinetic modeling and reactor simulations were performed successfully to describe the system dynamics of both the dehydration and partial oxidation reactions of 1-butanol.

Browsing by Author "Puurunen, Riikka L., Assoc. Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland"

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