Sinteza in karakterizacija mezoporoznih delcev Al2O3 z različnim premerom por

Šparlek, Klara (avtor), Švara Fabjan, Erika (mentor), Meden, Anton (komentor)

Mezoporozni materiali so definirani kot porozni materiali, ki vsebujejo kanale por s premerom med 2 nm in 50 nm. Mezoporozni materiali Al2O3 imajo visoko kemijsko, mehansko in termično stabilnost, zato se uporabljajo na področjih katalize, adsorpcije in senzorike. Z izbiro sinteznega postopka in variacijo sinteznih parametrov lahko pripravimo mezoporozne materiale z različnimi lastnostmi, na primer različno sestavo in morfološkimi lastnostmi, kot so velikost delcev, orientacija, premer in periodika kanalov por. V magistrskem delu sem preučevala možnosti priprave mezoporoznih delcev Al2O3 z različnim premerom por. Za pripravo sem uporabila dve različni sintezni poti, hidrotermalno metodo in metodo s samourejanjem z izparevanjem topila s solvotermalnim korakom (metoda SA-EISA). Pri hidrotermalni metodi sem variirala sintezne parametre, kot je uporaba različnih baz – etanolaminov (monoetanolamin, dietanolamin in trietanolamin) in vrednosti pH, do katere je bila reakcijska zmes z njimi uravnana (pH 6,5, 7,5 ali 8,5). Pri metodi SA-EISA pa sem pri sintezi uporabila različne količine dodatka za uravnavo velikosti por. Pri obeh metodah sem izbrana materiala termično obdelala pri 500 °C, 700 °C, 900 °C in 1300 °C ter raziskovala vpliv termične obdelave na lastnosti materialov. Za karakterizacijo sem uporabila dušikovo fizisorpcijo, rentgensko praškovno difrakcijo, elektronsko mikroskopijo, termično analizo in infrardečo spektroskopijo s Fourierjevo transformacijo. Po sintezi materialov po hidrotermalni metodi sem ugotovila, da je bil pred termično obdelavo prisoten aluminijev oksid hidroksid, pri materialih, pripravljenih s trietanolaminom, pa tudi trietanolamin hidroklorid. Po termični obdelavi pri 500 °C je nastal mezoporozen material γ-Al2O3, sestavljen iz kristalov in porami med njimi. Materiali, ki so bili pripravljeni s trietanolaminom, so imeli najožjo porazdelitev velikosti por, specifična površina je bila višja pri materialih, pri katerih je bil pH, do katerega so bili materiali uravnani, med sintezo višji. Po termični obdelavi do vključno 900 °C je bil v vseh materialih prisoten γ-Al2O3 z mezoporozno strukturo, medtem ko so se pri 1300 °C pretvorili v neporozni α-Al2O3. Po metodi SA-EISA sem sintetizirala materiale z različnimi količinami cikloheksana, ki je deloval kot snov za uravnavanje velikosti por. Pred termično obdelavo je bil v materialih prisoten kristalinični aluminijev klorid hidrat. Pri 500 °C je nastal mezoporozni material s porami v delcih, ki so bile večje ob večjem dodatku cikloheksana, pri čemer se je specifična površina zmanjšala. Material je bil amorfen do 900 °C, kjer je prešel v γ-Al2O3, pri 1250 °C pa v neporozni α-Al₂O₃. Z višanjem temperature termične obdelave se je premer por zmanjšal. Ugotovila sem, da na premer por vplivajo vsi izbrani sintezni parametri in izbira sintezne metode. Pri tem ima največji vpliv na premer por temperatura termične obdelave, pri hidrotermalni metodi so se z višanjem temperature termične obdelave pore povečale, pri metodi SA-EISA pa zmanjšale

• Jezik: Slovenski jezik
• Ključne besede: mezoporozni materiali, aluminijev oksid, premer por, hidrotermalna metoda, metoda SA-EISA
• Vrsta gradiva: Magistrsko delo/naloga
• Organizacija: FKKT - Fakulteta za kemijo in kemijsko tehnologijo
• Leto izida: 2024
• PID: 20.500.12556/RUL-164317
• Datum objave v RUL: 22.10.2024

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Synthesis and characterisation of mesoporous Al2O3 particles with different pore diameter

Izvleček

Mesoporous materials are defined as porous materials containing pore channels with diameters between 2 nm and 50 nm. Mesoporous Al₂O₃ materials exhibit high chemical, mechanical, and thermal stability, making them useful in fields such as catalysis, adsorption, and sensing. By selecting a specific synthesis method and varying synthesis parameters, mesoporous materials with various properties can be prepared, including different compositions and morphological characteristics, such as particle size, orientation, pore diameter, and pore periodicity. In my master's thesis, I investigated the possibilities of preparing mesoporous Al₂O₃ particles with different pore diameters. I employed two different synthesis routes: the hydrothermal method and the solvent evaporation-induced self-assembly method with a solvothermal step (SA-EISA method). For the hydrothermal method, I varied synthesis parameters, such as the use of different bases–ethanolamines (monoethanolamine, diethanolamine, and triethanolamine) and the pH value to which the reaction mixture was adjusted (pH 6.5, 7.5, or 8.5). In the SA-EISA method, different amounts of pore size-controlling additives were used in the synthesis. For both methods, I thermally treated the selected materials at 500 °C, 700 °C, 900 °C, and 1300 °C and studied the effects of thermal treatment on the material properties. Characterization was carried out using nitrogen physisorption, X-ray powder diffraction, electron microscopy, thermal analysis, and Fourier-transform infrared spectroscopy. After synthesizing the materials using the hydrothermal method, I found that aluminum oxide hydroxide was present before thermal treatment. Additionally, materials prepared with triethanolamine contained triethanolamine hydrochloride. After thermal treatment at 500 °C, mesoporous γ-Al₂O₃ material was formed, consisting of crystals with pores between them. Materials synthesized with triethanolamine exhibited the narrowest pore size distribution, and their specific surface area was higher when the pH during synthesis was adjusted to a higher value. Up to 900 °C, γ-Al₂O₃ was present in all the materials, retaining the mesoporous structure, while at 1300 °C, they transformed into non-porous α-Al₂O₃. Using the SA-EISA method, I synthesized materials with varying amounts of cyclohexane as a pore-size-controlling agent. Before thermal treatment, crystalline aluminum chloride hydrate was present in the materials. At 500 °C, a mesoporous material with intra-particle pores was formed, where pore size increased with higher amounts of cyclohexane, leading to a decrease in the specific surface area. The material remained amorphous up to 900 °C, after which it transformed into γ-Al₂O₃, and at 1250 °C, it converted into non-porous α-Al₂O₃. As the thermal treatment temperature increased, the pore diameter decreased. I concluded that all selected synthesis parameters and the choice of synthesis method influence the pore diameter. Among these, the temperature of thermal treatment had the most significant effect on the pore diameter: for the hydrothermal method, the pores increased with rising thermal treatment temperature, while for the SA-EISA method, they decreased

• Ključne besede: mesoporous materials, aluminum oxide, pore diameter, hydrothermal method, SA-EISA method