Abstract
In the last decade, exploration of transition alumina phases with good adsorption properties has attracted a great research interest from both a fundamental and a practical point of view. The transition phases of alumina are metastable polymorphs of aluminum oxide formed through the thermal dehydration of aluminum trihydroxide and aluminum oxyhydroxide. Powder X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and low-temperature nitrogen absorption studies were employed to trace the formation of the transition phases of alumina. In this work transition alumina powders were synthesized starting from sodium aluminate solution prepared from Bayer liquor. The neutralization of sodium aluminate solution was performed with the use of sulphuric acid, while glucose was added in the starting solution. In this way, the single phase nanocrystalline boehmite was obtained. As-synthesized boehmite powders have high surface area (above 360 m2/g) and the average crystallite size less than 5 nm. The results showed that the properties of the powders (structure, morphology) are strongly influenced by the initial pH value of sodium aluminate solution, as well as by the duration of neutralization step.
Highlights
Vreme sinteze ima veći uticaj na morfologiju sintetisanih prahova od samog pH područja sinteze, s obzirom da se produžavanjem vremena neutralizacije na 120 min, slika 4, postiže homogenija struktura sa sfernim aglomeratima manjih veličina u odnosu na prahove dobijene pri vremenu sinteze od 30 min, slika 3
The results showed that the properties of the powders (structure, morphology) are strongly influenced by the initial pH value of sodium aluminate solution, as well as by the duration of neutralization step
Summary
Prelazne Al2O3 faze zbog svojih strukturnih karakteristika, a pre svega velike specifične površine, velike ukupne zapremine pora i uniformne raspodele pora, imaju izuzetno velike mogućnosti industrijske primene kao adsorbenti, katalizatori, membrane [1,2]. Za dobijanje nanokristalnog bemita u ovom radu odabrana je metoda neutralizacije rastvora natrijum-aluminata sumpornom kiselinom. Kao organski aditiv ima raznovrsnu ulogu pri sintezi raznih tipova materijala, međutim, podaci o njenoj primeni pri sintezi različitih Al2O3 faza prilično su ograničeni [13]. U ovom radu glukoza je korišćena na temperaturi od 70 °C, što je mnogo niža temperatura od onih koje se primenjuju pri hidrotermalnim uslovima dobijanja bemita i Al2O3 faza. Pokazalo se da je primena glukoze, pri uslovima sinteze koji su karakteristični za dobijanje gibsita i bajerita [12], dovela do neočekivanog efekta, odnosno do dobijanja nanokristalnog bemita. Cilj ovog rada je bio da se ispita uticaj procesnih parametara, pre svega pH područja neutralizacije rastvora natrijum-aluminata i vremena sinteze na fazni sastav i morfološke karakteristike sintetisanih prahova nanokristalnog bemita
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