Fig. 3.

The results of selectivity optimization for CO₂ hydrogenation. a The effect of H₂/CO₂ ratio over ZnAlO_x&H-ZSM-5. Reaction conditions: Space velocity = 6000 ml g⁻¹ h⁻¹, 3.0 MPa, 593 K. b The effect of CO introduction over ZnAlO_x&H-ZSM-5. Reaction conditions: catalyst weight = 667 mg, 3.0 MPa, 593 K, inlet gas containing 66.7 ml min⁻¹ mixed gas (H₂/CO₂/Ar = 3/1/0.2) and 0–26.6 ml min⁻¹ CO. c Comparisons of catalytic behaviors over ZnAlO_x&H-ZSM-5 and ZnAlO_x&Si-H-ZSM-5. Reaction conditions: Space velocity = 6000 ml g⁻¹ h⁻¹, 3.0 MPa, 593 K, H₂/CO₂/Ar = 3/1/0.2. A9 and A10 are representative of aromatics containing 9 and 10 carbon atoms, respectively