CO2-to-propane hydrogenation over bifunctional catalysts composed of Pd-loaded ZnZrOx and SAPO-34

We conducted CO₂-to-propane hydrogenation using bifunctional catalysts composed of Pd-loaded Zn-doped ZrO₂ and SAPO-34, and investigated the effect of Pd loading and reaction conditions on propane production. Three catalysts with different Pd loadings (0–0.2 mol%) were prepared to evaluate the influence of Pd content on catalytic performance. A small amount of Pd significantly enhanced paraffin selectivity, increasing it from approximately 50 % to nearly 100 %, without affecting the total hydrocarbon yield. This effect is attributed to the hydrogenation of olefins over metallic Pd. In contrast, excess Pd loadings promoted the reverse water–gas shift reaction, leading to lower methanol and hydrocarbon production. The reaction was conducted at a larger scale than previously reported, under conditions of 4  MPa and 350 °C, using 850  mg of catalyst and a feed gas flow rate of 30  mL(STP) min⁻¹. Under these conditions, a propane yield of 5.0 %, a space–time yield of 0.95  mol kg⁻¹ h⁻¹. Of note, a propane formation rate of 0.80 mmol h⁻¹ were achieved, which is twice as high as values reported in earlier studies.