20.500.12556/DKUM-95456 Razvoj magnetno segrevanih katalizatorjev za kemijsko hrambo vodika doktorska disertacija Development of magnetically heated catalysts for chemical hydrogen storage Doktorska disertacija obravnava razvoj inovativnih magnetno odzivnih nanokompozitov, namenjenih uporabi kot nosilcev katalizatorjev za elektrificirane kemijske procese. Uporaba izmeničnega magnetnega polja omogoča lokalizirano, hitro in selektivno segrevanje katalitskega sloja, kar predstavlja alternativo klasičnim načinom gretja ter prispeva k večji energetski učinkovitosti in združljivosti procesov z obnovljivimi viri energije. Glavni cilj doktorske disertacije je bil razvoj in karakterizacija novih magnetnih materialov za tehnologijo magnetno segrevane katalize ter preizkus njihove aktivnosti v procesih, ki omogočajo pretvorbo električne energije v kemijsko, kot je shranjevanje energije v molekulah, bogatih z vodikom. Preučili smo dva ključna primera: shranjevanje energije v obliki amonijaka (NH₃) ter v tekočih organskih nosilcih vodika (LOHC). Za ta namen smo razvili postopek priprave CoxNi1-x-Al₂O₃ nanokompozitov, prenosljiv na večjo skalo, v katerih so zlitinski nanodelci CoNi (~ 15 nm) homogeno porazdeljeni po porozni matrici iz aluminijevega oksida. Ti materiali imajo visoko specifično površino (~150 m² g⁻¹), so stabilni in se učinkovito segrevajo (≥ 500 °C, 25 mT), ko so izpostavljeni izmeničnemu magnetnemu polju. Nanos rutenijevih nanodelcev (1 ut.%, 2-7 nm) in njihova promocija z barijem (4,5 ut.%) sta omogočila pripravo katalizatorjev z visoko disperzijo (54 %) ter dobro pokritostjo (52 %) aktivnih mest. Eksperimenti sinteze in razgradnje amonijaka so potekali v namensko izdelanem kvarčnem reaktorju, ki omogoča obratovanje pri povišanih tlakih. Rezultati kažejo, da z barijem promoviran rutenijev katalizator pri sintezi NH₃ doseže reakcijsko hitrost 1600 mmol NH₃ gRu⁻¹ h⁻¹ pri 400 °C in 5,5 MPa, medtem ko nepromoviran katalizator doseže pri enakih pogojih zgolj 158 mmol NH₃ gRu⁻¹ h⁻¹. Podoben trend je prav tako pri razgradnji, kjer je popolna pretvorba s promoviranim katalizatorjem pri 50 °C nižja kot pri nepromoviranem. Poskusi, kjer smo dinamično vklapljali in izklapljali izmenično magnetno polje, so pokazali doseganje stacionarnih stanj v približno 10-15 min. Kvantnomehanski izračuni in modeliranje mikrokinetike so pokazali, da stična površina med barijevim oksidom in rutenijem bistveno olajša hitrost določujočo stopnjo, ki je razklop N2, kar pojasni opaženo povečano aktivnost z barijem promoviranih katalizatorjev. Aktivnost pripravljenih magnetnih katalizatorjev smo testirali tudi v šaržnem sistemu v procesih hidrogenacije tekočih organskih nosilcev vodika, in sicer na toluenu in dibenziltoluenu. Pri nizkem tlaku (1 MPa) in zmernih temperaturah (120–150 °C) smo dosegli visoke stopnje pretvorbe. Pri toluenu je bila 100-odstotna pretvorba dosežena že po dveh urah pri 120 °C, medtem ko je bil pri 150 °C za popolnoma hidrogeniranem dibenziltoluen dosežen izkoristek 37,6 % po 7,4 urah reakcije. Disertacija uvaja nov koncept katalitskih procesov, ki temeljijo na magnetnem segrevanju katalitskega sloja. Ta inovativni pristop predstavlja izviren znanstveni prispevek, saj omogoča učinkovitejšo izrabo energije, hitrejši odziv sistema in odpira možnosti za razvoj prilagodljivih, nizkoogljičnih tehnologij, združljivih z obnovljivimi viri energije. Doseženi rezultati potrjujejo uporabnost razvitih materialov za dolgoročno shranjevanje energije v kemijski obliki in s tem pomembno prispevajo k trajnostnemu razvoju alternativnih tehnologij. This dissertation focuses on the development of innovative magnetically responsive nanocomposites to serve as catalyst carriers for electrified chemical processes. The use of an alternating magnetic field enables localised, rapid and selective heating of the active sites of the catalyst, which represents an alternative to conventional heating methods and contributes to improved energy efficiency and compatibility with renewable energy sources. The main objective of this work was to develop and characterise new magnetic materials for magnetically heated catalysis. Furthermore, we evaluated their performance in processes that enable the conversion of electrical energy into chemical energy, such as energy storage in hydrogen-rich molecules. Two important case studies were investigated: energy storage in the form of ammonia (NH₃) and hydrogen storage in liquid organic hydrogen carriers (LOHC). To this end, a scalable synthesis route for CoxNi₁₋ₓ-Al₂O₃ nanocomposites was developed in which the CoNi-alloy nanoparticles (~15 nm) are homogeneously dispersed in a porous aluminium oxide matrix. These materials exhibit a high specific surface area (~150 m² g⁻¹), good stability and efficient heating (≥500 °C, 25 mT) when exposed to an alternating magnetic field. The deposition of ruthenium nanoparticles (1 wt%, 2–7 nm) and their promotion with barium (4.5 wt%) resulted in catalysts with high dispersion of ruthenium (54 %) and good coverage of the ruthenium active sites with barium species (52 %). The ammonia synthesis and decomposition experiments were carried out in a custom-designed high-pressure reactor. The results show that the barium-promoted ruthenium catalyst achieves an ammonia synthesis rate of 1600 mmol NH₃ gRu⁻¹ h⁻¹ at 400 °C and 5.5 MPa. In contrast, the non-promoted catalyst only achieved 158 mmol NH₃gRu⁻¹ h⁻¹ under the same conditions. A similar trend was observed for ammonia decomposition, where complete conversion was achieved 50 °C lower with the promoted catalyst compared to the non-promoted catalyst. Dynamic experiments, in which the alternating magnetic field was switched on and off at regular intervals, showed that the steady state is reached within 10–15 minutes. Quantum chemical calculations and microkinetic modelling revealed that the interface between barium oxide and ruthenium significantly lowers the energy barrier for nitrogen dissociative adsorption. The latter explains the observed increased activity of the barium-promoted catalysts. The activity of the prepared magnetic catalysts was also tested in batch hydrogenation processes of liquid organic hydrogen carriers, in particular toluene and dibenzyltoluene. High conversion rates were achieved at low pressure (1 MPa) and moderate temperatures (120–150 °C). For toluene, complete conversion was achieved within two hours at 120 °C, while a yield of 37.6 % was achieved for H18-dibenzyltoluene after 7.4 hours at 150 °C. The dissertation presents a novel concept for catalytic processes based on magnetic heating. This innovative approach represents a significant scientific contribution as it enables more efficient energy utilisation, faster system response and opens up new possibilities for the development of flexible, low-carbon technologies compatible with renewable energy sources. The results confirm the applicability of the developed materials for long-term renewable energy storage in chemical form and thus make an important contribution to the development of sustainable technologies. magnetna kataliza katalizator elektrifikacija amoniak LOHC obnovljivi viri energije magnetic catalysis catalyst electrification ammonia LOHC renewable energy sources true true false [A. Sedminek] Slovenski jezik Angleški jezik Doktorsko delo/naloga 2025-09-19 09:59:49 2025-12-23 09:04:41 2026-01-06 03:18:23 0000-00-00 00:00:00 2025 0 Maribor 0 Maribor XVI, 117 str. 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 544.478.032.53:621.355(043.3) 263388163 DOK_Sedminek_Anja_2025.pdf DOK_Sedminek_Anja_2025.pdf 1 66BB76927C632E46DD5EDF8B093EAAF6 4915a2357607e5a374f17a31f599340fba26e315c20feff72143f451d38a4943 af98df73-df50-11f0-8504-00155d580e02 https://dk.um.si/Dokument.php?lang=slv&id=201634 Fakulteta za kemijo in kemijsko tehnologijo 0 0 0