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Figure S1. Cyclic CO2 capture and hydrogenation at 250 ºC for the different catalysts: (a) Na-Ni/Al; (b) K-Ni/Al; (c) Ba-Ni/Al. Figure S2. Cyclic CO2 capture and hydrogenation at 350 ºC for the different catalysts: (a) Na-Ni/Al; (b) K-Ni/Al; (c) Ba-Ni/Al. Figure S3. Cyclic CO2 capture and hydrogenation at 400 ºC for the different catalysts: (a) Na-Ni/Al; (b) K-Ni/Al; (c) Ba-Ni/Al. Figure S4. Cyclic CO2 capture and hydrogenation at 450 ºC for the different catalysts: (a) Na-Ni/Al; (b) K-Ni/Al; (c) Ba-Ni/Al. Figure S5. produced CH4 (a) and CO (b) and released CO2 (c) within 100 s upon H2 admission at 250 ºC. Figure S6. Produced CH4 (a) and CO (b) and released CO2 (c) within 100 s upon H2 admission at 300 ºC. Figure S7. Produced CH4 (a) and CO (b) and released CO2 (c) within 100 s upon H2 admission at 350 ºC. Figure S8. Produced CH4 (a) and CO (b) and released CO2 (c) within 100 s upon H2 admission at 400 ºC. Figure S9. Produced CH4 (a) and CO (b) and released CO2 (c) within 100 s upon H2 admission at 450 ºC. Figure S10. HAADF-STEM images (a,c,e) and particle size distribution (b,d,f) of DFMs: (a,b) K-Ni/al; (c,d) Na-Ni/Al; (e,f) Ba-Ni/Al. Figure S11. Cyclic CO2 capture and hydrogenation at 350 ºC for the different catalysts using feed B (5% CO2, 11% H2O, 4.5% O2 in Ar): (a) K-Ni/Al; (b) Na-Ni/Al; (c) Ba-Ni/Al. Figure S12. Comparison of productivity switching the composition of the capture gas between feed A (5% CO2 in Ar), feed B (5% CO2, 11% H2O, 4.5% O2 in Ar) and feed A again. (a) cyclic CH4 productivity with feed B;Figure S13. Temperature programmed reaction of 15%Ni on alumina. Fitting of Ni 2p3/2: Table S1. Result of the Fitting of Ni 2p3/2 peaks for Ba-Ni. Table S2. Result of the Fitting of Ni 2p3/2 peaks for K-Ni. Table S3. Result of the Fitting of Ni 2p3/2 peaks for Na-Ni. Fitting of C 1s: Table S4. Result of the Fitting of C1s peaks for Ba-Ni. Table S5. Result of the Fitting of C1s and K2p peaks for K-Ni. Table S4. Result of the Fitting of C1s peaks for Na-N

Bimetallic catalysts consisting of nickel and one alkali or alkaline-earth metal (Na, K or Ba) on alumina support have been tested in the cyclic CO2 capture and subsequent methanation. The best performance was attained with a different material for cyclic tests (K-Ni/Al) than for Sabatier reaction (Ba-Ni/Al). In cyclic tests, the methane productivity shows different dependence with the temperature for each alkali and alkaline-earth metal. For temperature of 300 °C or above, the dual functional materials show stable cyclic performance when the capture is performed both from 5% CO2 in Ar and from simulated flue gas containing also O2 and H2O. Using the later feed, the CH4 productivity diminish reversibly compared to oxygen free conditions and nickel metal oxidises significantly. K-Ni/Al exhibited the best cyclic performance in terms of CH4 productivity and stability, which is associated to the highest reducibility of oxidised nickel species and the lowest formation of unreducible carbonates.

Bifunctional materials based on Ru nanoparticles and an alkaline metal (K, Na or Ba) have been scrutinized for several cycles of CO2 capture and subsequent methanation at different temperatures from 250 ºC to 450 ºC. The optimum performance in terms of stable cyclic operation, amount of captured CO2 and relevant methane productivity was attained at different temperature window for each material. For the materials here prepared, the limiting lower operation temperature of stable cyclic performance was determined by the methanation kinetics, which depended on reactivity of COx ad-species captured with each alkaline metal. The highest activity was found with Ba-containing materials, which exhibited a stable and relevant cyclic CH4 productivity at 250 ºC, being one of the lowest operation temperatures reported for a dual functional material to date. This material exhibited stable cyclic performance also in the presence of O2 and H2O, although the CH4 productivity decreases slightly and reversibly compared to that using CO2 containing gas free of O2 and H2O.

Ru and Ni on alumina catalysts have been promoted with a 10 wt% of alkali metal (K or Na) or alkaline earth metal (Ba) and tested in CO2 methanation. For the catalyst consisting of Ni and Ba, the variation of Ba loading while keeping Ni loading constant was studied. The promotion in terms of enhanced CH4 yield was found only for the addition of barium to 15 wt% Ni/Al2O3. In contrast, K and Na addition increased the selectivity to CO while decreasing conversion. For the Ru-based catalyst series, no enhancement in conversion or CH4 yield was attained by any of the alkaline metals. CO2 temperature-programed desorption (CO2-TPD) revealed that the amount of chemisorbed CO2 increased significantly after the addition of the base metal. The reactivity of COx ad-species for each catalyst was assessed by temperature-programed surface reaction (TPSR). The characterization revealed that the performance in the Sabatier reaction was a result of the interplay between the amount of chemisorbed CO2 and the reactivity of the COx ad-species, which was maximized for the (10%Ba)15%Ni/Al2O3 catalyst.

This work studies the catalytic properties of Cu and Ni catalysts, as well as the effect of Cu and Ni combination on the activity and selectivity during the aqueous phase hydrogenation of 5-hydroxymethylfurfural (HMF) in a batch reactor, at 60 °C under 30 bar H2. Catalysts with different Ni/Cu ratios (10 wt%) were synthesized over a high surface area graphite (HSAG). While Ni provides the bimetallic catalyst the capacity for hydrogenation of C[dbnd]O and C[dbnd]C groups, Cu contributes to suppress the hydrogenation of the furan ring, reaching a 99% of selectivity to the partial hydrogenated product, 2,5-di-hydroxymethylfuran (DHMF), over 5Cu5Ni/HSAG. The increase of reaction temperature (180 °C) conduced to the hydrolytic ring-opening and rearrangement of HMF. Under such reaction conditions, monometallic Ni afforded the highest yield towards the hydrogenative rearrangement product, 3-hydroxymethylcyclopentanone (81%). However, Cu and CuNi bimetallic catalysts were less reactive to the ring-rearrangement reaction and showed higher tendency to deactivation, especially when the HMF supplier contain sulfur impurities. © 2023 The Authors

1-butanol dehydration reaction has recently emerged as a sustainable route to produce butenes which can be further oligomerized to be applied as jet fuel. However, the high catalyst deactivation rates observed during this reaction due to coke deposition is still a pending matter. As promising catalysts for this reaction, we have supported two heteropolyacids (HPA), i.e. H4SiW12O40 (STA) and H3PW12O40 (TPA), on two commercial carbon materials: an activated carbon (AC) and a high surface area graphite (HSAG). Aiming to evaluate the role of HPA-support interactions, the STA was also dispersed over metallic oxides of different acidic nature, namely SiO2, Al2O3 and ZrO2. An exhaustive physicochemical characterization revealed that after the HPA dispersion thorough the support, the Keggin structure was maintained and an increase in the amount and strength of acid sites was provoked, but in different degree according to the HPA type and support's nature. While the TPA-based catalysts developed less quantity of total acid sites, but higher strength than their STA-carbon counterparts, the STA/AC and TPA/AC samples exhibited a slight major amount of acid sites than STA/HSAG and TPA/HSAG. The HPA-support interactions have ultimately modulated to some extent the activity, selectivity, stability and regeneration ability of the synthesized catalysts, when applied in the gas phase butanol dehydration reaction at 275 °C. The higher STA decomposition temperature prompted by the graphitic support, among other factors, allowed the total regeneration of the highly active (39 mmolBuOH∙min−1∙ga.p) and n-butenes selective (>98 %) STA/HSAG catalyst by means of combustion of carbon deposits at 400 °C. © 2023 The Authors

The synthesis of methanol by carbon dioxide hydrogenation has been studied using copper-molybdenum carbides supported on high surface area graphite, reduced graphene oxide and carbon nanotubes. The synthesis conditions and the effect of the support were studied. The catalysts were prepared in situ using H2 or He at 600 °C or 700 °C. Both molybdenum carbide and oxycarbide were obtained. A support with less reactive carbon resulted in lower proportion of carbide obtained. The best results were achieved over a 5 wt.% Cu and 10 wt.% Mo on high surface area graphite that reached 96.3% selectivity to methanol.

Dimerization of isobutene (IBE) to C8s olefins was evaluated over a range of solid acid catalysts of diverse nature, in a fixed bed reactor working in a continuous mode. All catalytic materials were studied in the title reaction performed between 50–250 C, being the reaction feed a mixture of IBE/helium (4:1 molar ratio). In all materials, both conversion and selectivity increased with increasing reaction temperature and at 180 C the best performance was recorded. Herein, we used thermogravimetry analysis (TGA) and temperature programmed desorption of adsorbed ammonia (NH3-TPD) for catalysts characterization. We place emphasis on the nature of acid sites that a ect the catalytic performance. High selectivity to C8s was achieved with all catalysts. Nicely, the catalyst with higher loading of Brønsted sites displayed brilliant catalytic performance in the course of the reaction (high IBE conversion). However, optimum selectivity towards C8 compounds led to low catalyst stability, this being attributed to the combined e ect between the nature of acidic sites and structural characteristics of the catalytic materials used. Therefore, this study would foment more research in the optimization of the activity and the selectivity for IBE dimerization reactions.