Tailoring thermal development of gamma alumina sorbents material using combustion synthesis: the effect of amino acids (

  • PDF / 3,047,662 Bytes
  • 11 Pages / 595.276 x 790.866 pts Page_size
  • 35 Downloads / 210 Views

DOWNLOAD

REPORT


Tailoring thermal development of gamma alumina sorbents material using combustion synthesis: the effect of amino acids (G, A, N) and equivalence ratio Vilko Mandić1   · Stanislav Kurajica1 · Katarina Mužina1 · Filip Brleković1 · Ivana Katarina Munda1 Received: 30 November 2019 / Accepted: 14 September 2020 © Akadémiai Kiadó, Budapest, Hungary 2020

Abstract Using a combustion synthesis, the range of achievable textures is broader than using conventional synthesis methods and can be controlled more successfully. As a tool allowing the achievement and control of desired textures, here we bring about wet chemistry synthesis using aluminium nitrate nonahydrate (ANN) precursor systematically combined with different fuels (amino acids). The amino acids; glycine (G), alanine (A) and asparagine (N) have been specifically selected in order to show the role of gradual increase in their: (1) molar mass, (2) enthalpy of combustion, (3) amine groups content and (4) ratio to ANN. Detailed (micro) structural and thermal characterisations confirm that the nanocrystalline character and thermomechanical stability were not diminished in the course of this synthesis. The conditions leading to development of different morphologies from gels to powders were found to be heavily under the influence of fuel/oxygen ratio, i.e. of the smouldering versus flaming mechanism of the combustion. Higher content of nitrates (predominately from amino-rich amino acids) strongly promoted auto-combustion behaviour. As-derived alumina precursors have been thermally treated at various temperatures (quenched and soaked), to monitor γ- and α-alumina crystallisation, with respect to the development of morphology. Different texture types have been observed, such as porous wormhole, porous and porous expanded flakes. Higher fuel levels promote specific surface increase. This combustion synthesis allows facile tailoring of nanocrystalline γ-alumina with different morphological features, whereas samples having optimal parameters were suitable for catalyst support application on behalf of rapid sorption performance. Keywords  γ-Alumina · Combustion synthesis · Alanine · Asparagine · Glycine · Equivalence ratio

Introduction Porous materials are utilised in catalysis, separation, sensors, energy conversion and storage [1]. Most approaches to porous materials synthesis require the use of templates and thus are complex, time-consuming and costly. On the other hand, solution combustion synthesis is template-free, simple, rapid and affordable [2]. Combustion synthesis utilises a mixture of precursor salts (acting as oxidants) and a fuel (acting as reducing agent) to produce oxide powders [3]. This technique consists of heating a saturated aqueous solution of precursors to the point of ignition. Once initiated, * Vilko Mandić [email protected] 1



Faculty of Chemical Engineering and Technology, Marulićev trg 20, 10000 Zagreb, Croatia

a highly exothermic reaction becomes self-sustainable, whereas the fast combustion process is accompanied with the generation of many ga