fig5

Figure 5. (A) Schematized representation of the catalytic transformation of propane to propylene via non-oxidative and oxidative dehydrogenation routes on V-HAP samples with Ca²⁺-O^2- surface acid-base pairs generated due to proton migration process close to VO₄ tetrahedra. The square box represents oxygen vacancy and the squiggly arrow refers to the proton migration process. Reproduced from Ref.^[69] with permission from Wiley-VCH GmbH. (B) Product selectivity for OCM reactions over HAP-based catalysts at 23% conversion under 973 K and 101 kPa pressure conditions and a space velocity of 8,800 mL·gcat^-1·h^-1. Reproduced from Ref.^[58] with permission from Elsevier. (C) c-surface HAP (i), a-surface HAP (ii), the CH₄ conversion rate of the Pb-HAP catalyst with different orientations for OCM reaction. Reproduced from Ref.^[60] with permission from American Chemical Society.