The Pt function in Pt,Sn/Mg(Al)O and in Pt/Mg(Al)O catalysts has been studied by a combination of catalytic testing for ethane dehydrogenation at 450−650 °C under a C2H6/H2/CO2/N2/Ar = 10:1.6:6.8:5.9:75.7 flow and Fourier transform infrared spectroscopy (FT-IR), using CO as a probe molecule. The acid−base properties of the support were also investigated by FT-IR, using CH3CN as a probe molecule. CO adsorption experiments revealed the presence of Pt terraces, as well as Pt sites with low coordination number (steps, edges, corners, or defects) on Pt/Mg(Al)O. The same experiments on Pt,Sn/Mg(Al)O revealed that Sn covers the steps, corners, edges, and defects of the Pt particles, thus developing simultaneously a geometric and a chemical effect on the surface properties of the exposed Pt atoms. Accordingly, the ethane dehydrogenation reaction proceeds with a lower activation energy over Pt,Sn/Mg(Al)O compared to Pt/Mg(Al)O. Further, Sn addition leads to more selective and more stable ethane dehydrogenation catalysts. The higher dehydrogenation selectivity of Pt,Sn catalysts was correlated to the masking of low-coordinated Pt sites. The Pt/Mg(Al)O and Pt,Sn/Mg(Al)O catalysts were subjected to an activation procedure consisting of several test−regeneration cycles. Good correlation was found between the number of accessible Pt sites and the catalytic activity after each cycle.

Morphological, textural, and surface properties of a NSR (NO x storage reduction) Pt-K/Al 2 O 3 model catalyst (Pt 1 wt %; K 5.4 wt %) were characterized by means of XRD, HRTEM, and FT-IR spectroscopy. Thin crystalline K-containing layers, in the form of cubic K 2 O and monoclinic K 2 CO 3 and very small roundish Pt particles with a mean diameter of 1.5 nm, have been observed. Monoclinic K 2 CO 3 disappears, and a certain degree of Pt sintering occurs (d Pt ≈ 3.4 nm) after use. However, the presence of potassium limits the Pt sintering which occurs on the Pt/Al 2 O 3 reference sample (Pt 1 wt %). FT-IR spectra of CO adsorbed at RT, compared with those recorded for Pt/Al 2 O 3 , revealed a marked interaction between the Pt and K phases that is much higher than the interaction between the Pt and Ba phases observed for the classic Pt-Ba/Al 2 O 3 catalyst. CO 2 adsorption at RT indicated a high heterogeneity of the K phase, evidenced by the formation of a variety of surface-carbonate-like species (mainly bridging carbonates on K sites). Minor amounts of nitrites and nitrates were formed at RT under NO admission, while the uptake was sensibly higher under NO/O 2 or NO 2 admission; nitrites (mono-and bidentate) and nitrates (ionic and bidentates) were formed in different amounts, both relative and absolute, and the nitrate to nitrite ratio increased in parallel with the NO/O 2 ratio. Also, at each contact time, the amount of the stored NO x species increased upon increasing the NO/O 2 ratio.

The production of carbon-rich hydrocarbons via CO 2 valorization is essential for the transition to renewable, non-fossil-fuel-based energy sources. However, most of the recent works in the state of the art are devoted to the formation of olefins and aromatics, ignoring the rest of the hydrocarbon commodities that, like propane, are essential to our economy. Hence, in this work, we have developed a highly active and selective PdZn/ZrO 2 +SAPO-34 multifunctional catalyst for the direct conversion of CO 2 to propane. Our multifunctional system displays a total selectivity to propane higher than 50% (with 20% CO, 6% C 1 , 13% C 2 , 10% C 4 , and 1% C 5 ) and a CO 2 conversion close to 40% at 350 °C, 50 bar, and 1500 mL g –1 h –1 . We attribute these results to the synergy between the intimately mixed PdZn/ZrO 2 and SAPO-34 components that shifts the overall reaction equilibrium, boosting CO 2 conversion and minimizing CO selectivity. Comparison to a PdZn/ZrO 2 +ZSM-5 system showed that propane selectivity is further boosted by the topology of SAPO-34. The presence of Pd in the catalyst drives paraffin production via hydrogenation, with more than 99.9% of the products being saturated hydrocarbons, offering very important advantages for the purification of the products.