Catalytic behaviour of transition metal carbides of group 5 in the methanol steam reforming

Transition metal carbides of group 5 (G5TMC=VC, NbC and TaC) with similar crystallite sizes were prepared by a sol-gel route. The catalysts were characterized and studied in the methanol steam reforming (MSR) reaction in the temperature range of 573–723 K at atmospheric pressure and using a stoichiometric CH3OH/H2O = 1/1 mole ratio mixture. Under the MSR reaction conditions used, the route of methanol transformation depends on the G5TMC used as catalyst. The catalytic behaviour of VC differs from that of NbC and TaC, which in turn show a similar behaviour. Over VC, methanol is mainly converted to a mixture of H2+CH4, whereas over NbC and TaC the major product obtained is HCHO, formed from the dehydrogenation of methanol

An in-situ DRIFTS-MS study of the photocatalytic H2 production from ethanol(aq) vapor over Pt/TiO2 and Pt-Ga/TiO2 catalysts

In this paper, Pt/TiO2 and Ptsingle bondGa/TiO2 catalysts with similar Pt dispersion and similar structural and morphological characteristics were compared in the H2 production from the phototransformation of aqueous solutions of ethanol. Catalysts were characterized by means of N2 adsorption-desorption, XRD, Raman, H2-TPR, UV–Vis diffuse reflectance spectroscopy, XPS and CO chemisorption. The photocatalytic reaction was carried out in liquid and vapour phase. The photocatalytic transformation of ethanol(aq) vapour over Pt/TiO2 and Ptsingle bondGa/TiO2 catalysts was studied by in situ DRIFTS-MS. Differences in the photocatalytic transformation of ethanol(aq) over Pt/TiO2 and Ptsingle bondGa/TiO2 were determined. The effect of Ga is analysed in the light of the evolution of surface species under photocatalytic reaction conditions

CO2 reduction over Cu-ZnGaMO (M = Al, Zr) catalysts prepared by a sol-gel method: Unique performance for the RWGS reaction

Cu-ZnGaMO (M = Al, Zr) catalysts prepared by a surfactant-free sol-gel method were characterized and tested in the reverse water-gas shift (RWGS) reaction. Their catalytic behavior was analyzed under 0.1–3 MPa at 250–325 °C and using a reactant mixture of CO2/H2 = 1/3. The catalytic results are analyzed in the light of the characteristics of the catalysts. The Cu-ZnGaZrO catalysts were highly selective for the RWGS reaction; a major role of surface copper and interface oxygen vacancies is proposed. CO2 conversion and CO selectivity increased on increasing the reaction temperature. CO2 conversion reaches 16.8% with 99.7% selectivity for CO under 0.1 MPa at 325 °C over the Cu-ZnGaZrO1 catalyst. It is suggested that CO and methanol production proceed via independent reaction pathways

Preparation and characterization of bulk Mo⁠xC catalysts and their use in the reverse water-gas shift reaction

In this work, different routes for the preparation of molybdenum carbides through sol-gel methods were studied; several parameters such as molybdenum precursor, carbon source and Mo/C ratios were explored. The materials were characterized using different techniques, such as adsorption/desorption of N2, XRD, Raman spectroscopy, SEM-EDX, TEM-EELS, H2-TPR and XPS. Depending on the preparation method used, the presence of different MoxC crystalline phases, Mo2C and/or MoC cubic and/or hexagonal, were determined. The catalytic behaviour in CO2 conversion for CO production through the reverse water gas shift reaction was tested using a reactant mixture CO2/H2 = 1/3 (molar ratio) at 0.1 MPa and a gas hourly space velocity of 3000 h-1. Values of CO2 conversion up to 26 %, with nearly 100 % selectivity to CO were achieved as a function of the reaction temperature and the catalyst used

Monitoring the insertion of Pt into Cu2−xSe nanocrystals: a combined structural and chemical approach for the analysis of new ternary phases

The tuning of the chemical composition in nanostructures is a key aspect to control for the preparation of new multifunctional and highly performing materials. The modification of Cu2−xSe nanocrystals with Pt could provide a good way to tune both optical and catalytic properties of the structure. Although the heterogeneous nucleation of metallic Pt domains on semiconductor chalcogenides has been frequently reported, the insertion of Pt into chalcogenide materials has not been conceived so far. In this work we have explored the experimental conditions to facilitate and enhance the insertion of Pt into the Cu2−xSe nanocrystalline lattice, forming novel ternary phases that show a high degree of miscibility and compositional variability. Our results show that Pt is mainly found as a pure metal or a CuPt alloy at high Pt loads (Pt : Cu atomic ratio in reaction medium >1). However, two main ternary CuPtSe phases with cubic and monoclinic symmetry can be identified when working at lower Pt : Cu atomic ratios. Their structure and chemical composition have been studied by local STEM-EDS and HRTEM analyses. The samples containing ternary domains have been loaded on graphite-like C3N4 (g-C3N4) semiconductor layers, and the resulting nanocomposite materials have been tested as promising photocatalysts for the production of H2 from aqueous ethanolic solutions

Effective and highly selective CO generation from CO2 using a polycrystalline α‑Mo2C catalyst

Present experiments show that synthesized polycrystalline hexagonal α-Mo2C is a highly efficient and selective catalyst for CO2 uptake and conversion to CO through the reverse water gas shift reaction. The CO2 conversion is ~16% at 673 K, with selectivity towards CO > 99%. CO2 and CO adsorption is monitored by DRIFTS, TPD, and microcalorimetry, and a series of DFT based calculations including the contribution of dispersion terms. The DFT calculations on most stable model surfaces allow for identifying numerous binding sites present on the catalyst surface, leading to a high complexity in measured and interpreted IR- and TPD-spectra. The computational results also explain ambient temperature CO2 dissociation towards CO as resulting from the presence of surface facets such as Mo2C(201)-Mo/C ¿displaying Mo and C surface atoms¿ and Mo-terminated Mo2C(001)-Mo. An ab initio thermodynamics consideration of reaction conditions however demonstrates that these facets bind CO2 and CO + O intermediates too strong for a subsequent removal, whereas the Mo2C(101)-Mo/C exhibits balanced binding properties, serving a possible explanation of the observed reactivity. In summary, results show that polycrystalline α-Mo2C is an economically viable, highly efficient, and selective catalyst for CO generation using CO2 as a feedstock

Autoimmune Diseases and COVID-19 as Risk Factors for Poor Outcomes: Data on 13,940 Hospitalized Patients from the Spanish Nationwide SEMI-COVID-19 Registry

(1) Objectives: To describe the clinical characteristics and clinical course of hospitalized patients with COVID-19 and autoimmune diseases (ADs) compared to the general population. (2) Methods: We used information available in the nationwide Spanish SEMI-COVID-19 Registry, which retrospectively compiles data from the first admission of adult patients with COVID-19. We selected all patients with ADs included in the registry and compared them to the remaining patients. The primary outcome was all-cause mortality during admission, readmission, and subsequent admissions, and secondary outcomes were a composite outcome including the need for intensive care unit (ICU) admission, invasive and non-invasive mechanical ventilation (MV), or death, as well as in-hospital complications. (3) Results: A total of 13,940 patients diagnosed with COVID-19 were included, of which 362 (2.6%) had an AD. Patients with ADs were older, more likely to be female, and had greater comorbidity. On the multivariate logistic regression analysis, which involved the inverse propensity score weighting method, AD as a whole was not associated with an increased risk of any of the outcome variables. Habitual treatment with corticosteroids (CSs), age, Barthel Index score, and comorbidity were associated with poor outcomes. Biological disease-modifying anti-rheumatic drugs (bDMARDs) were associated with a decrease in mortality in patients with AD. (4) Conclusions: The analysis of the SEMI-COVID-19 Registry shows that ADs do not lead to a different prognosis, measured by mortality, complications, or the composite outcome. Considered individually, it seems that some diseases entail a different prognosis than that of the general population. Immunosuppressive/immunoregulatory treatments (IST) prior to admission had variable effects

Ti-containing hybrid mesoporous organosilicas as photocatalysts for H2 production from ethanol

A series of complex organic-inorganic mesoporous materials were successfully synthesized by a microwave-assisted method that allowed the preparation of periodic mesoporous organosilicas (PMOs) with Ti (IV) forming part of the structure (Ti-PMOs). Materials were characterized using N2 adsorptionedesorption isotherms, powder X-ray diffraction (XRD), transmission and high resolution transmission electron microscopy (TEM and HRTEM), Raman, infrared, UVevisible diffuse reflectance (UVevis RDS), X-ray photoelectron (XPS), photoluminescence (PL) and electrochemical impedance (EIS) spectroscopy, and transient photocurrent measurements. Samples labeled Ti10-PMO, Ti20-PMO and Ti40- PMO (with Si/Ti molar ratio of about 10, 20 and 40), showed crystal-like characteristics and high specific surface area (742e829 m2 g-1). Ti-PMOs were studied in the photocatalytic H2 evolution from an aqueous ethanol solution under UVevisible irradiation. Ti-PMOs showed a better photocatalytic behavior than PMO and this is related with the presence of tetrahedral Ti(IV) in the PMOs network. Ti-PMOs displayed a lower barrier for the electron transfer and a more efficient charge separation than PMO. The highest H2 production was obtained with Ti20-PMO photocatalyst; after 4 h of irradiation, 2042 mmol H2 gcat 1 were obtained, which was about 20 times higher than that obtained with a reference commercial TiO2 (P25)

Behaviour of Pt/TiO2 catalysts with different morphological and structural characteristics in the photocatalytic conversion of ethanol aqueous solutions

Pt/TiO2 catalysts with a similar Pt dispersion and different morphological and structural characteristics were prepared, characterized and used in the photocatalytic transformation of aqueous ethanol solutions at room temperature. The characteristics of the catalysts allowed the comparison of their catalytic behaviour as a function their structural and morphological properties, which determined both the amount of hydrogen produced and the nature of the carbon-containing products. The characterization techniques used include N2 physisorption, XRD, TEM, Raman, UV–vis and XP spectroscopies, H2-TPR and CO chemisorption. Temperature programmed desorption of post-reaction catalysts was followed by DRIFTS-MS. The Pt/TiO2 catalysts contained only anatase (Pt/A catalysts) or both anatase and rutile (Pt/AR catalysts), and had surface area from approximately 50 m2·g−1 to 100 m2·g−1 with mean pore sizes varying from 5 to 43 nm. Pt/TiO2 catalysts having surface area of approximately 50 m2·g−1 and mean pore size of 30–40 nm produced more H2 than the other catalysts, with Pt/A50 being the catalyst which produced the most. In all cases, the major carbon-containing products in the liquid phase were acetaldehyde, 2,3-butanediol and acetic acid. A relationship between the mean pore size and the yield of 2,3-butanediol was established with most being produced over Pt/A100 which had the smallest pore size