Microfibrous-structured Pd/brass-fiber catalysts are developed for the selective hydrogenation of acetylene in the front-end configuration. The brass fibers are pre-calcined in air to create an endogenously growing ZnO-CuOx composite layer, and 0.25 wt% Pd is loaded on the brass fibers via the impregnation method. The activity and selectivity of our Pd/brass-fiber catalysts are primarily governed by the alloying degree of active sites regarded as Pd-Zn-Cu ensembles with the PdCu(alloy)-PdZnCu(alloy) twin structure, which are strongly sensitive to both the brass-fiber calcination and the catalyst reduction temperatures. For the preferred catalyst obtained using brass fibers calcined at 500 degrees C and reduced in H-2 at 250 degrees C, over 90% selectivity is achieved at nearly 100% acetylene conversion with promising stability. Additionally, due to the weakened ethylene hydrogenation ability at high reaction temperature over the Pd-Zn-Cu ensembles, the catalysts tend to present higher ethylene selectivity as the reaction temperature increases. (C) 2019 Elsevier Inc. All rights reserved.