Fig. 6. Effect of proximity of Zn-doped ZrO₂ and SSZ-13 on catalytic behaviours of the bifunctional catalyst. (a) Dual bed (0.20 g Zn–ZrO₂ + 0.40 g SSZ-13–45H); (b) mixing of granules of two components with sizes of 250–600 μm; (c) Zn–ZrO₂ (8.9 nm)/micro-SSZ-13–45H; (d) Zn–ZrO₂ (8.9 nm)/nano-SSZ-13; (e) Zn–ZrO₂ (4.8 nm)/nano-SSZ-13. The selectivity of CO₂ was in the range of 41–45% for each type of proximity. Reaction conditions: catalyst, 0.60 g; H₂/CO = 2; P = 3 MPa; T = 673 K; F = 30 mL min^–1; time on stream, 10 h.