Colloids and Surfaces A: Physicochem. Eng. Aspects 233 (2004) 145–153 Sol–gel transition study and pyrolysis of alumina-based gels prepared from alumatrane precursor Bussarin Ksapabutr a , Erdogan Gulari b , Sujitra Wongkasemjit a,∗ a The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok 10330, Thailand b Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109-2136, USA Received 25 May 2003; accepted 18 November 2003 Abstract Alumina gels were prepared by the sol–gel method using alumatrane or tris(alumatranyloxy-i-propyl)amine as precursor synthesised directly from the reaction of inexpensive and readily available compounds, aluminium hydroxide and triisopropanolamine (TIS), via the one step process. Sol–gel process parameters, such as gel time, were correlated to variables of the initial stage of the process, such as pH, temperature of hydrolysis and hydrolysis ratio. The sol–gel transition of alcoholic alumatrane solutions was monitored by multiple waveform rheological measurements. The gel time could be determined from the evolution of the storage (G ′ ) and loss (G ′′ ) moduli versus time at different frequencies using the Winter Chambon criterion (convergence of the loss tangents at the gel point). Increasing pH values, hydrolysis ratio and/or temperature accelerated the kinetics of hydrolysis–condensation reactions and thus reduced the gel time. The apparent activation energy of the cross-linking leading to the gelation calculated from the gel times at various temperatures was found to be approximately 139 kJ mol -1 and independent of hydrolysis ratio. Alumina materials prepared from the heat treatment of obtained gel at 500 ◦ C were analysed using X-ray diffraction and the BET method. © 2003 Elsevier B.V. All rights reserved. Keywords: Sol–gel transition; Alumatrane precursor; Alumina; Rheology; Gel time 1. Introduction Alumina materials have a wide range of applications in a great number of industrial areas, particularly in cataly- sis, membrane separation processes, catalytic membrane reactors, adsorbent, composite, coating, fibre, electronic and optic fields [1–7]. Alumina prepared by sol–gel pro- cess is frequently used in such areas. In the development of soft chemistry, the sol–gel process is considered to be the most practical method for the synthesis of inorganic oxides. This process usually involves the hydrolysis and condensation of various metal alkoxide molecules under controlled conditions to form metal–oxygen–metal bridg- ing units. In many cases the metal alkoxide precursors are very sensitive to water and, therefore, cannot control the hydrolysis reaction [8,9]. Generally, the aluminium alkoxides, such as aluminium sec-butoxide and aluminium ∗ Corresponding author. Tel.: +66-2-218-4133; fax: +66-2-215-4459. E-mail address: dsujitra@chula.ac.th (S. Wongkasemjit). iso-propoxide, are used to prepare alumina by sol–gel method [10–12]. However, these usual precursors are ex- pensive and aluminium sec-butoxide can be rapidly hydrol- ysed to give the hydrolysis products dispersed in 2-butanol [13–17]. Alumatrane is aminoalkoxide derivatives of aluminium synthesised directly from the reaction of inexpensive and readily available compounds, aluminium hydroxide and triisopropanolamine (TIS), via the one step pro- cess. Its presence of trialkanoamine ligands is hydrolyt- ically stable, thus yielding more controllable chemistry and minimising special handling requirement. Therefore, it should be used as precursor in ceramic processing by sol–gel route. In this work, we investigate the dy- namic viscoelastic properties and FT-IR studies on sol–gel process of alumatrane under different conditions. This observation is mainly focused on the influence of pH, hydrolysis ratio and temperature on the cross-linking pro- cess. In addition, some preliminary thermal studies of an alumina obtained by the sol–gel technique are also observed. 0927-7757/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2003.11.019