Synthesis and characterization of novel adsorbents and catalysts based on natural zeolite, applicable in use of biomass

Abstract

The thesis has two interconnected general goals. The first one was to develop novel, environmentally friendly and cost-efficient soil supplements using natural zeolite (clinoptilolite, CLI) which will retain plant nutrients (nitrogen, potassium and phosphorus) in different soil types and accordingly increase biomass production. The second one was to develop effective clinoptilolite-based catalysts for biomass conversion into industrial valuable chemicals. To achieve the first aim, nitrate and phosphate adsorption onto CLI modified with several oxides were studied. The obtained results showed that the oxide coverage of CLI surface makes it accessible for effective binding of nitrate and phosphate ions. The best adsorption ability was obtained for Fe(III)-enriched CLI (FeCLI). FeCLI shows significantly better retention effect than CLI but the leaching depends on soil types. Nitrate retention increases by the zeolite addition only for silty loam and silty clay soils whereas potassium retention increases in the following order: silty loam < silty clay << sandy soil. FeCLI shows a retention effect in phosphate leaching only from sandy soil. The second goal was development of a CLI-based catalyst effective in the esterification of levulinic acid (LA) which can be obtained from biomass. The catalysts were prepared from CLI and SnO2 or sulfated SnO2. Sulfated catalysts are more active than nonsulfated ones. Nonsulfated catalysts showed a high activity in the conversion of LA into octyl levulinate (55%) and moderate activity in the conversion into ethyl levulinate (22%), whereas sulfated catalysts led to a total conversion of LA to esters.

Teza ima dva međusobno povezana opšta cilja. Prvi cilj je dobijanje novog, ekološki prihvatljivog i jeftinog zemljišnog suplementa korišćenjem prirodnog zeolita (klinoptilolit, CLI) koji će zadržati biljne nutrijente (azot, kalijum i fosfor) u različitim vrstama zemljišta i shodno tome povećati proizvodnju biomase. Drugi cilj je dobijanje efikasnog katalizatora na bazi klinoptilolita za konverziju biomase u industrijski važne hemikalije. Za postizanje prvog cilja, proučavana je adsorpcija nitrata i fosfata na CLI koji je bio modifikovan sa nekoliko oksida. Dobijeni rezultati pokazali su da oksidna prevlaka na površini CLI omogućava efikasno vezanje nitrata i fosfata. Najbolja adsorpciona sposobnost dobijena je za Fe(III)-obogaćen CLI (FeCLI). FeCLI pokazuje značajno bolji efekat zadržavanja ispitivanih jona u odnosu na CLI, ali izluživanje zavisi od vrste zemljišta. Zadržavanje nitrata povećava se dodatkom zeolita u praškastu glinu i praškastu ilovaču, dok se zadržavanje kalijuma povećava sledećim redosledom: praškasta ilovača < praškasta glina << peskuša. FeCLI pokazuje efekat zadržavanja fosfata samo za peskuše. Drugi cilj teze bio je razvoj efikasnog katalizatora zasnovanog na CLI, za primenu u esterifikaciji levulinske kiseline (LA) koja se može dobiti iz biomase. Katalizator je pripremljen iz CLI i SnO2 ili sulfatiranog SnO2. Sulfatirani katalizatori pokazali su veću aktivnost u odnosu na nesulfatirane. Nesulfatirani katalizatori pokazali su aktivnost u konverziji LA u oktil levulinat (55%) i umerenu aktivnost u konverziji u etil levulinat (22%), dok su sulfatirani katalizatori LA u potpunosti konvertovali u estre.