To develop an efficient Cr-based catalyst for CO2-oxydehydrogenation of ethane, H-ZSM-5 was modified with a series amount of ZrO2 (0–30 wt%) via the one-pot hydrothermal method and then, impregnated with aqueous solution of Cr(NO3)3. Several techniques including XRD, FESEM, EDX, TEM, BET, ICP, FTIR and H2-TPR were applied to characterize the physicochemical properties of as-synthesized samples. The successful synthesis of ZrO2-doped ZSM-5 supports was verified by XRD, EDX and ICP results. It was found that the existence of ZrO2 promoted the dispersion of Cr species, leading to smaller particle size of chromium oxide, which enhanced the catalyst reducibility and strengthened the interaction of the modified support with Cr species, thus facilitating a faster reduction-oxidation cycle. However, the excessive loadings of ZrO2 alleviate its synergetic effect due to the significant decrease of surface area, appearance of more number of agglomerations and surface coverage of ZSM-5. The results revealed that the highest catalytic activity was reached on Cr supported ZrO2-doped ZSM-5 containing 10 wt% zirconia. Besides, it exhibited stable activity during the course of running the reaction for about 5 h at 700 °C, suggesting that the presence of ZrO2 modifier not only boost the Cr/ZSM-5 activity but also makes it less sensitive to the deactivation. Accordingly, the optimum zirconia content in the ZrO2-doped ZSM-5 support of Cr-based catalysts seems to be 10 wt%.
