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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.

[EN] The application of Metal-Organic Frameworks (MOFs) in gas phase heterogeneous catalysis is still not widely spread because of their limited stability under reaction conditions. Obtaining stable acidic MOFs to be used in reactions that demand strong acid sites remains a challenge up to the present time. In this work, it is shown that nanocrystals of Zirconium MOF UiO-66 can be conveniently and easily functionalized through a simple one-pot synthetic approach, i.e. the direct treatment of UiO-66 with ammonium sulfate followed by an adequate thermal treatment, giving rise to a highly acidic and thermally stable material (named as S-UiO-66). This material can act as catalyst in the gas phase isobutene dimerization demonstrating high catalytic activity at moderate temperatures while maintaining the structural integrity of the MOF after several catalytic evaluations and/or after reuse cycles. The S-UiO-66 material represents a novel alternative in the search of robust MOF-based catalysts to be applied in gas phase heterogeneous catalytic reactions that demand strong acid sites.

[EN] The catalytic performance of a series of Ru-based catalysts was evaluated for the selective aerobic oxidation of benzyl alcohol to benzaldehyde under base-free mild conditions. The effect of metal precursor (RuCl, RuNO(NO) and Ru(CO)) and support on catalyst performance was investigated by comparing undoped (rGO) and N-doped (NrGO) reduced graphene oxide with commercial activated carbon and high surface area graphite supports. The surface chemistry and structure of materials were characterized by nitrogen physisorption (BET), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The average Ru nanoparticle sizes were in the range from 1.4 to 2.4 nm, with the smallest particle sizes obtained on rGO support owing to its highest surface area. Catalysts prepared from RuNO(NO) and Ru(CO) precursors exhibit the highest benzyl alcohol conversion to the corresponding aldehyde, with highest conversions observed when NrGO support is employed. Catalysts prepared from Ru(CO) on NrGO support exhibit the highest activity for benzaldehyde formation, which is over three times that of commercial activated carbon supported Ru catalysts. The differences in catalytic performance are attributed to interactions between the acidic product of the reaction and the basic surface sites of the NrGO support, and modification of the surface hydrophobicity. These factors confer a significant rate enhancement in the selective oxidation of benzyl alcohol over Ru/NrGO compared to Ru/rGO. Ru/NrGO is stable under reaction conditions, however progressive deactivation is observed owing to water accumulation at the active site. Catalysts are easily reactivated via heating, with >90% of the original activity recovered on reuse.

[EN] In the present study, the catalytic coupling of ethanol into 1-butanol through the Guerbet reaction was studied in a fixed bed reactor over different catalytic systems based on Cu and/or Ni as a hydrogenating/dehydrogenating components, and manganese oxide incorporating acid/base properties over a carbonaceous support, high surface area graphite (HSAG). The catalysts were prepared by wetness impregnation of the support with the corresponding metal nitrates and the resulting material was then reduced in-situ with hydrogen at 573 K for 1 h before reaction. The catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), specific surface area, NH temperature-programmed desorption, CO chemisorption, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). From all these techniques it can be deduced that the dimensions of the catalytic ingredients (Cu, Ni, Mn)are in the nanometric scale and homogeneously dispersed on the support. The reactions were performed in a continuous-flow fixed-bed reactor in gas phase with these bifunctional catalysts at 503 K and 50 bar using a stream of helium and ethanol. The bimetallic catalyst 2.5Cu2.5Ni-Mn/HSAG, treated in helium at 723 K prior reduction with hydrogen, exhibited the best catalytic performance in terms of 1-butanol selectivity (39%), presumably due to the synergetic effect of the weak strength acid sites and the strong base sites related to manganese oxide and the Cu-Ni nanoparticles.

[EN] The possible pathways of sugars transformation into 1,2-propanediol (PDO)have been studied, using new bifunctional catalysts for this catalytic multistep reaction. The catalysts are based on an acidic active phase (polyoxometalates, POMs)and a metallic function (Ru nanoparticles)supported over activated carbon (AC, S = 1190 m/g). This support was loaded with 15 wt% of polyoxometalate, either phosphotungstic acid (TPA)or tungstosilicic acid (STA), while the amount of loaded ruthenium was close to 2 wt%. The catalytic materials were characterized by X-ray diffraction and electron microscopy techniques (SEM and TEM), while the surface active sites were evaluated using model reaction tests: cyclohexane dehydrogenation for metallic surface sites and isomerization of 3,3-dimethyl-1-butene for acid sites. For different sugars (sucrose, pentoses or hexoses)hydrogenation/hydrogenolysis using these catalysts in batch reactor was studied. The higher PDO selectivity was obtained in ethanol:water media and this study aims to establish the possible ways that sugars follow to achieve this transformation. The best catalytic material, 2%Ru-15%STA supported on AC, yields up to 50% of PDO selectivity when fructose is used as reactant, under moderate reaction conditions (413 K and 30 bar H).

N-doped (NrGO) and non-doped (rGO) graphenic materials are prepared by oxidation and further thermal treatment under ammonia and inert atmospheres, respectively, of natural graphites of different particle sizes. An extensive characterization of graphene materials points out that the physical properties of synthesized materials, as well as the nitrogen species introduced, depend on the particle size of the starting graphite, the reduction atmospheres, and the temperature conditions used during the exfoliation treatment. These findings indicate that it is possible to tailor properties of non-doped and N-doped reduced graphene oxide, such as the number of layers, surface area, and nitrogen content, by using a simple strategy based on selecting adequate graphite sizes and convenient experimental conditions during thermal exfoliation. Additionally, the graphenic materials are successfully applied as electrocatalysts for the demanding oxygen reduction reaction (ORR). Nitrogen doping together with the starting graphite of smaller particle size (NrGO325-4) resulted in a more efficient ORR electrocatalyst with more positive onset potentials (Eonset = 0.82 V versus RHE), superior diffusion-limiting current density (jL, 0.26V, 1600rpm = −4.05 mA cm−2), and selectivity to the direct four-electron pathway. Moreover, all NrGOm-4 show high tolerance to methanol poisoning in comparison with the state-of-the-art ORR electrocatalyst Pt/C and good stability.

Formic acid, a major product of biomass processing, is regarded as a potential liquid carrier for hydrogen storage and delivery. The catalytic dehydrogenation of FA to generate hydrogen using heterogeneous catalysts is of great interest. Ni based catalysts supported on silica were synthesized by incipient wet impregnation. The effect of doping with an alkaline earth metal (calcium) was studied, and the solids were tested in the formic acid decomposition reaction to produce hydrogen. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and programmed temperature surface reaction (TPSR). The catalyst doped with 19.3 wt.% of Ca showed 100% conversion of formic acid at 160 °C, with a 92% of selectivity to hydrogen. In addition, all the tested materials were promising for their application, since they showed catalytic behaviors (conversion and selectivity to hydrogen) comparable to those of noble metals reported in the literature.

[EN] The physicochemical and catalytic properties of bimetallic AgCu catalysts and their monometallic counterparts supported on a high surface area graphite have been comparatively evaluated in the ethanol dehydrogenation reaction, performed in a continuous-flow reactor. While Cu was incorporated by the incipient wetness impregnation technique, for Ag catalysts two synthesis procedures were explored: incipient wetness impregnation and adsorption of Tollens’ reagent. The catalysts prepared by wetness impregnation exhibited higher metal dispersion, being improved for the bimetallic catalysts in comparison with the monometallic counterparts. The results obtained in the catalytic tests revealed that Cu catalysts is nearly two orders of magnitude more active than Ag catalyst in the dehydrogenation reaction of ethanol on either a turnover frequency or a weight basis, but at the same time both catalysts were 100% selective to acetaldehyde. Whereas selectivity was not affected by the bimetallic composition, there was a substantial decrease in the reaction rate among the bimetallic catalysts as the Cu/Ag ratio diminished, due to blockage of copper surface active sites by silver. Both silver and copper, and the bimetallic catalysts, suffered from deactivation at 523 K, caused by blocking of active sites by adsorbed hydrocarbons on the catalyst surface (fouling). Carbonaceous deposits were removed through a thermal treatment under H flow, which allowed the total recovery of the initial catalytic activity.