Vpliv dopiranja CuO/ZnO/Al2O3 katalizatorjev na sintezo metanola in izvajanje obratne reakcije vodnega plina.

• Main Author: Knez, Tjaša
• Other Authors: Likozar, Blaž
• Format: Bachelor Thesis
• Language: Slovenian
• Published: 2021
• Subjects: sinteza metanola; hidrogenacija CO2; heterogena kataliza; učinkovitost katalizatorjev; reakcija vodnega plina; methanol synthesis; CO2 hydrogenation; heterogeneous catalysis; catalysts efficiency; water gas shift reaction; sami
• Online Access: https://repozitorij.uni-lj.si/IzpisGradiva.php?id=129970; https://repozitorij.uni-lj.si/Dokument.php?id=147019&dn=; https://plus.si.cobiss.net/opac7/bib/81984259?lang=sl

Naraščanje koncentracije CO2 v ozračju zaradi sodobnega načina življenja, predstavlja negativen vpliv na okolje. V zadnjih letih je prišlo do znatnega povečanja števila tehnologij, ki bi lahko prispevale k znižanju emisij. Ena od teh metod predstavlja sintezo metanola, ki se začne z ogljikovim dioksidom in vodikom. Ta tehnologija je uporabna zaradi dveh razlogov znižanja škodljivih emisij ogljikovega dioksida v atmosferi in proizvodnjo snovi, ki se lahko uporabijo kot alternativno gorivo ali kot vhodna snov organskih sintez. Metanol se lahko uporablja tudi za druge namene, saj je eden izmed najbolj uporabljenih komponent v kemijski industriji. Pretvorba CO2 je zelo zahtevna, saj je ta molekula termodinamsko stabilna in ima zelo nizko reaktivnost. Zaradi teh razlogov je v učinkovito pretvorbo potrebno vložiti dovolj energije, zagotoviti ustrezne reakcijske pogoje in uporabiti učinkovit katalizator. V tem raziskovalnem delu smo preučevali vpliv dopiranja CuO/ZnO/Al2O3 katalizatorjev na sintezo metanola. Na komercialen katalizator CZA smo dopirali tri kovine, rodij, nikelj in platino. Količina dopiranih kovin mora biti minimalna, da so stroški čim nižji in da je število neželenih reakcij čim manjše. Zaradi močne interakcije med kovino in kovinskim oksidom lahko pride do znižanja navidezne aktivacijske energije katalizatorja in pa nastanka večjega deleža metanola. Na katalizatorje smo dopirali različne količine kovin z impregnacijsko metodo, ter jih testirali pri enakih reakcijskih pogojih. Rezultati testiranj so pokazali, da največji delež nastalega metanola dobimo s katalizatorji na katerih ni nanešene kovine. Ti katalizatorji pa imajo tudi najnižjo aktivacijsko energijo. Iz rezultatov je razvidno tudi, da s katalizatorji na katerih sta nikelj in platina, dobimo večji delež nastalega ogljikovega monoksida kot pa metanola. To nam pove da imajo ti katalizatorji višjo selektivnost za ogljikov monoksid. Sklepamo lahko, da pri teh katalizatorjih ni prišlo do željene močne interakcije med kovino in kovinskim oksidom. S pomočjo podatkov, ki smo jih dobili iz EDS analize, smo izračunali povprečne deleže kovin ter njihovo razporejenost. Na katalizatorje smo dopirali zadosten delež kovin in tudi njihova razporejenost je ustrezna. Predvidevamo, da kovina ni v celoti v porah katalizatorja pač pa se nahaja tudi na sami površini katalizatorja. Zanimivo bi bilo pogledati vpliv dopiranja istih kovin na katalizator z drugačno metodo priprave katalizatorja. Increasing the concentration of CO2 in the atmosphere due to modern way of life has a negative impact on the environment. In recent years, there has been a significant increase in technologies that contribute to reducing emissions. One of those methods involves the synthesis of methanol, starting with carbon dioxide and hydrogen. This technology is useful for two reasons, it reduces emissions of carbon dioxide in the air and the produce of a substance that can be used as an alternative fuel or as a starting material for organic synthesis. Methanol can also be used for other purposes as it is one of the most widely used components in the chemical industry. The conversion of CO2 is very difficult, as this molecule is thermodynamically stable and has very low reactivity. Because of these reasons, for efficient conversion it is necessary to invest sufficient energy, to ensure appropriate reaction conditions and to use an efficient catalyst. In this research work we studied the influence of doping CuO/ZnO/Al2O3 catalyst on methanol synthesis. Three metals, rhodium, nickel, and platinum were added to the CZA commercial catalyst. The amount, of metals doped should be kept to a minimum, to reduce the expenses and to reduce unwanted side reactions. Due to the strong interaction between the metal and the metal oxide, the apparent activation energy of the catalyst may decrease, and a higher production of methanol may be formed. Different amounts of metals were doped to the catalysts by the impregnation method and then tested under the same reaction conditions. The results showed that the largest share of the formed methanol is produced with catalysts on which no metal was dopped. These catalysts also have the lowest activation energy. The results also show that with catalysts with nickel and platinum, we get higher share of carbon monoxide than methanol. This tells us that these catalysts have higher selectivity for carbon monoxide. It can be concluded that the strong interaction between metal and metal oxide did not occur with these catalysts. Using the data obtained from the EDS analysis, we calculated the average proportions of metals and their distribution. A sufficient proportion of metals was applied to the catalysts, and their distribution is adequate. We can conclude that the metal is not entirely in the pores of the catalyst but is also on the surface of the catalyst. It would be interesting to look at the effect of metals doped to the catalyst with a different method of catalyst preparation.