28 KB102 KB23 KB199219991998Batista, JurkaJenko, MonikaMandrino, ĐorđePintar, Albinletnik:32številka:6str. 527-532ISSN:1318-0010COBISSID:93866URN:URN:NBN:SI:doc-E07DO57VenInštitut za kovinske materiale in tehnologijeŽelezarna JeseniceŽelezarna RavneŽelezarna ŠtoreKovine zlitine tehnologijealuminijev oksidbakerhidrogeniranjekatalizatorjikemijska kinetikapaladijCharacterization of Pd-Cu/gamma-Al2O3 catalysts by XPS and catalytic measurements| Karakterizacija Pd-Cu/gama-Al2O3 katalizatorjev z XPS metodo in kinetičnimi testi|Liquid-proces hydrogenaation using a solid catalyst provides a potential technique for the removal of nitrates from waters. Various Pd-Cu bimetallic catalysts were prepared according to different impregnation sequences of ?$\gamma-Al_2O_3$? support, and tested for the selective hydrogenation of aqueous nitrate solutions to nitrogen. Measurements were performed in a semi-batch slurry reactor at T=293 K. The results show that the nitrate-to-nitrate reduction step undergoes a structure-insensitive hydrogenation with a heterolytic electron transfer. The most suitable distribution of metallic copper and palladium phases, which results in the minimum formation of ammonium ions, was obtained for the catalyst preparation procedures, in which the alumina is impregnated first by copper salt. XPS examination of mono- and bimetallic catalysts revealed that in all examined samples Pd is present in the metallic form. On the other hand, in a Cu/?$\gamma-Al_2O_3$? sample previously reduced at T=773 K in hydrogen atmosphere, copper is found in +1 and +2 oxidation states. In the presence of both elements on the catalyst surface, copper is detected in low oxidation states (i.e., 0 and +1)Heterogeno katalizirana hidrogenacija vodnih raztopin nitratnih ionov predstavlja potencialno metodo za čiščenje z nitratnim ionom kontaminirane pitne vode. Pd-Cu bimetalni katalizatorji, pripravljeni z različnimi impregnacijskimi nanosi kovinskih prekurzorjev na ?$\gamma-Al_2O_3$? kot nosilec, so bili testirani na selektivno pretvorbo v vodi raztopljenega nitratnega iona v dušik. Poskusi so bili opravljeni v semišaržnem reaktorju z goščo, obratujočem pri T=293 K in atmosferskem tlaku. Rezultati meritev kažejo, da je redukcija nitratnega v nitritni ion strukturno neselktivna reakcija s heterolitskim prenosom elektronov. Za minimalno produkcijo amonijevega iona kot stranskega produkta procesa katalitske redukcije vodnih raztopin nitratnega iona je prednostna tista prostorska porazdelitev Pd in Cu specij, pri kateri se na zunanji strani delca katalizatorja nahaja kovinska faza, na kateri se vodik adsorbira disociativno. Rezultati XPS analize monometalnih in bimetalnih katalizatorjev kažejo, da se Pd v vseh testiranih vzorcih nahaja v kovinskem stanju. Baker je v Cu/?$\gamma-Al_2O_3$? katalizatorju prisoten v oksidaacijskih stanjih +1 in +2, medtem ko se v Pd-Cu bimetalnih katalizatorjih nahaja bodisi v kovinskem stanju bodisi v +1 oksidacijski oblikiNadaljuje se kot: Materiali in tehnologijeTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaInštitut za kovinske materiale in tehnologije