Catalytic conversion of ethane to aromatics (BTX) over metal/HZSM-5 catalysts involves significant catalyst deactivation due to coking. Consequently, true acidity/performance relationships are escaped if the intrinsic catalyst acidity was correlated to the "steady-state" performance. Here, the effect of acidity on the early-stage performance and time-dependent deactivation kinetics has been investigated. The early-stage ethane conversion and BTX selectivity both increased with decreasing Si/Al-2 ratios. Specifically, the space-time yields of BTX increase linearly with increasing Bronsted acidity, indicating Bronsted acids as the main active sites for BTX. Further evidence can be found from the transient experiment (C2H6/Ar <-> C2H6/NH3) and C2H4-TPSR. A promotion effect of the Zn(II) sites (mainly responsible for ethane dehydrogenation) on BTX formation was also observed. With time-on-stream, the catalytic performance attenuated due to coking, which can be modeled as "r(t) = r(0)/(1 + kt(alpha))" kinetically, and the parameters (for aromatics) k decreased and alpha increased with decreasing acidity.