Single-site Ga/SiO2 catalysts exhibit up to 99% C3H6 selectivity at 4% propane conversion with an initial rate of 5.4 x 10(-4) (mole C3H6) (mole Ga)(-1) s(-1) during propane dehydrogenation (PDH) at 550 A degrees C. Following pre-treatment in H-2 at 550 A degrees C, only four-coordinate, Ga3+-O Lewis acid sites are observed under reaction conditions. At 650 A degrees C in H-2, an additional isolated Ga site with lower Ga-O coordination (N (Ga-O) < 4) is formed and leads to a 30% decrease in the initial PDH rate per total moles of Ga. The PDH rates are equivalent when normalized by the amount of surface, four-coordinate Ga3+-O, regardless of catalyst pre-treatment conditions, which indicates that these isolated Ga3+ centers are the catalytically relevant sites. Isolated, Lewis acidic Ga3+ cations present as four-coordinate Ga3+-O centers exhibit up to 99% C3H6 selectivity during propane dehydrogenation (PDH) at 550 A degrees C. An additional isolated Ga site with lower Ga-O coordination is formed during H-2 treatment at elevated temperatures, but is inactive for PDH and reversibly decomposes under reaction conditions.