A novel approach is described for preparing Ga-promoted Pt particles for the dehydrogenation of light alkanes to alkenes. The modifying element, Ga, was introduced by transference from the support, a calcined Mg(Ga)(Al)O hydrotalcite-like material. Pt nanoparticles were dispersed onto the calcined Mg(Ga)(Al)O starting from an organometallic precursor, followed by reduction. The formation of PtGa alloy particles is dependent on reduction temperature. Reduction at 723 K produces mainly metallic Pt particles. The average diameter of the Pt nanoparticles increased from 1.4 nm to 2.2 nm with increasing Ga content, and decreasing Al content of the support, demonstrating the importance of support Al atoms in stabilizing the dispersion of Pt. After reduction at 773-873 K, PtGa alloys were observed. It is proposed that at high reduction temperatures. H atoms formed on the surface of the metal particles spill over onto the support where they reduce Ga3+ cation to atomic Ga, which then interacts with the supported Pt to form PtGa alloys. The activity, selectivity and stability of Pt/Mg(Ga)(Al)O catalysts for ethane and propane dehydrogenation are described in the second part of this study (G. Siddiqi, P. Sun, V. Galvita, A.T. Bell, Journal of catalysis (2010), doi:10.1016/j.jcat.2010.06.016 [40]). (C) 2010 Elsevier Inc. All rights reserved.