CO2 methanation : effective Ni-based catalysts and mechanisms over Ru/Al2O3

Fluorine-modified Mg–Al mixed oxides: A solid base with variable basic sites and tunable basicity

The interactions of reactants and intermediates with the surfaces in ethanol steam reforming over Co catalysts supported on ZrO2 and CeO2 were investigated using Temperature Programmed Desorption, Thermogravimetric Analysis-Differential Scanning Calorimetry (TGA-DSC), in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and isotopic labeling techniques. Possible mechanistic steps are proposed that lead to acetaldehyde and acetone formation, steam reforming and coking. The role of the support versus active metal (i.e., Co) and the involvement of water in the reaction network are discussed. The interactions of reactants and intermediates with the surfaces were investigated in ethanol steam reforming over Co catalysts supported on ZrO2 and CeO2 were investigated using Temperature Programmed Desorption, Thermogravimetric Analysis-Differential Scanning Calorimetry (TGA-DSC), in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and isotopic labeling techniques.

Temperature-programmed diffuse reflectance infrared Fourier transform spectroscopy (TPDRIFTS) has been used to characterize a reacted selective catalytic reduction (SCR) vanadia/titania catalyst. At room temperature the reacted catalyst presents ammonium ions adsorbed on the surface. On heating under N 2 flow, a surface redox reaction takes place; ammonium ions are oxidized to bridged nitrosyls species, while V 5+ = O groups are reduced to V 3+ . Reduction of V 5+ species to V 3+ ions occurs at lower temperatures than those observed in conventional TPR processes under H 2 atmospheres. At higher temperatures, bridged nitrosyls species become monodentate, first in an angular configuration and then in a linear one. Previous data on the SCR reaction let us propose that they are desorbed from the surface as gaseous N 2 O.

Co-electrolysis of carbon dioxide and steam has been shown to be an efficient way to produce syngas, however further optimisation requires detailed understanding of the complex reactions, transport processes and degradation mechanisms occurring in the solid oxide cell (SOC) during operation. Whilst electrochemical measurements are currently conducted in situ, many analytical techniques can only be used ex situ and may even be destructive to the cell (e.g. SEM imaging of the microstructure). In order to fully understand and characterise co-electrolysis, in situ monitoring of the reactants, products and SOC is necessary. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) is ideal for in situ monitoring of co-electrolysis as both gaseous and adsorbed CO and CO2 species can be detected, however it has previously not been used for this purpose. The challenges of designing an experimental rig which allows optical access alongside electrochemical measurements at high temperature and operates in a dual atmosphere are discussed. The rig developed has thus far been used for symmetric cell testing at temperatures from 450 °C to 600 °C. Under a CO atmosphere, significant changes in spectra were observed even over a simple Au|10Sc1CeSZ|Au SOC. The changes relate to a combination of CO oxidation, the water gas shift reaction, carbonate formation and decomposition processes, with the dominant process being both potential and temperature dependent.

Chemometry-assisted Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) method for quantification of a novel antipsychotic agent in pharmaceuticals: A case study on ICH Q 14 concept

The low methanol selectivity of Cu/CeO₂ in CO₂ hydrogenation stems from weak metal–support interaction (MSI) and dominant reverse water gas shift (RWGS) pathways. Ga‐doped CeO₂ solid solutions are proposed to enhance MSI and oxygen vacancies, addressing insufficient CO₂ activation and H₂ dissociation in conventional Cu‐based catalysts. CuO‐CeGaₓOₓ (y = 0–0.3) catalysts were synthesized via co‐precipitation. Structural and catalytic properties were analyzed by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), temperature‐programmed H2 reduction (H₂‐TPR), temperature‐programmed desorption of adsorbed CO2 (CO₂‐TPD), and transmission electron microscopy (TEM). Ga doping (y = 0.2) optimized CeGaOₓ solid solution formation, achieving the highest specific surface area (142 m2/g), and Cu0 content (73.4%). At 260°C, CuO‐CeGa₀.₂Oₓ showed 12.6% XCO₂, 57% SCH₃OH, and STY = 308.8 gMeOH Kgcat−1 h−1. Enhanced oxygen vacancies and moderate basic sites suppressed RWGS, favouring methanol pathways. Stability tests confirmed 180 h performance retention without structural degradation. Ga doping strengthens MSI via CeGaOₓ solid solutions, promoting oxygen vacancies and Cu0 dispersion. This dual optimization enhances CO₂ adsorption, H₂ dissociation, and methanol selectivity while suppressing CO byproducts. The CuO‐CeGa₀.₂Oₓ catalyst demonstrates industrial potential, offering a design strategy for high‐performance CO₂ hydrogenation catalysts.

SummaryThis study assesses the effect of various drying procedures on water repellency measured by water drop penetration time (WDPT) and spectroscopic parameters gauged by Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFT) of two anthropogenically‐influenced soils at sites in Berlin. Wettable and water‐repellent samples were dried at various temperatures and at prescribed relative humidity. WDPT and DRIFT spectroscopic characteristics were obtained from both dried and field‐moist subsamples. Normalization of DRIFT spectral C–H band intensity (‘surface hydrophobicity’) against the integral absorption intensity over the wave number range 4000–400 cm−1 resulted in an apparent resolution between the effects of water content and changes in C‐H absorption at the surface. To our current knowledge, the latter could be best explained with changes in the three‐dimensional rearrangement of organic molecules or moieties on inner and outer soil organic matter (SOM) surfaces, whereas the former could be a direct consequence of the fraction of inner and outer soil surfaces covered with water and of the mean thickness of the respective water films. Further evidence for this model is required from other investigations focusing on the surfaces in soil, before drawing final conclusions. The results show that the method of drying affects WDPT to a greater extent than soil water content after drying. DRIFT spectra suggest that exposure to high temperature results in some reorganization of SOM in the outer layer. It is further suggested that short exposure may result in a heterogeneous distribution of water leading to localized variation and inconsistency in WDPTs. Drying for 4 weeks under controlled relative humidity at 20°C is suggested as a reference preparation method combining the benefits of an almost unchanged SOM surface compared with field‐moist samples with homogeneous moisture distribution.

Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) has been established as a good and relatively sensitive method for qualitative analysis of powders and rough surfaces. The technique is non-destructive and high quality spectra can be easily obtained without extensive sample preparation. The capacity of the method for qualitative analysis of functional groups has been demonstrated in numerous fields. The potential of DRIFTS for quantitative analysis was recognized quite early as well. However, many theoretical and practical problems do appear when the method is applied for this purpose, requiring very accurate sampling procedure. The effect on reflectance spectra of several parameters influencing sampling has been studied. Conventionally, a simplified relation derived from the phenomenological continuum theory of Kubelka-Munk is used in order to relate the concentration of a chromophore, dispersed in a sample, to the intensity of the diffusely reflected radiation. In practice however, this equation can be used only for ideal systems diluted in a non-absorbing scattering matrix and in a limited concentration range. Preparation of such idealized samples in a reproducible way is difficult. Quantitative analysis of opaque non-diluted systems such as those found in the real world is of high interest. In many fields, like for example in thin layer chromatography, stationary phase studies, environmental pollutant analysis, and industrial quality control or heterogeneous catalysis, it is desirable to quantitatively characterize samples as close as possible to their original state. In our own effort to do quantitative spectroscopy of powders, we have investigated the case of non-diluted samples. Model systems constituted of two types of silica powders (Cab-O-Sil and LiChrosorb) of very different morphology were prepared. The surface hydroxyl groups of SiO2 were exposed to a silylation reaction with an aminosilane containing a suitable chromophore. Known superficial concentrations of molecules carrying a cyano functional group were anchored by this way on the powder surface. A quantitative model of diffuse reflectance, derived from the general hyperbolic solutions of the Kubelka-Munk equations has been developed, taking into account different parameters such as the absorption of the silica substrate, finite thickness of the sample, specular reflection, as well as diffusion and absorption coefficients profiles within the depth of the scattering layer. Application of this model gives a quite good description of measured diffuse reflectance, in cases where the simple Kubelka-Munk relation fails. Use of a Mar quardt type non-linear least square adjustment method to the experimental data allows moreover the determination of other parameters of interest. A new FTIR analytical technique, based on a PVDF photo-pyroelectric film detector, has also been developed, which has enabled for the first time sequential measurement of diffuse reflectance and diffuse transmittance of the same sample without any change in the optical geometry and sample manipulation. Another multilayer discontinuum theory, more suited for particles of diameter larger than the radiation wavelength, has been developed and successfully applied to diffuse reflectance and transmittance measurements of sodium carbonate powders.

Methanation of CO2 over Ni/Al2O3 modified with alkaline earth metals: Impacts of oxygen vacancies on catalytic activity

Hydrogen production with high efficiency and low CO selectivity is the objective of developing methanol steam reforming (MSR) catalysts. The nature of the active sites and reaction mechanisms, however, has not been fully resolved, hampering the rational design of improved catalysts. Herein, we apply the isotope modulation excitation-phase sensitive detection-diffuse reflectance infrared Fourier transform spectroscopy (ME-PSD-DRIFTS) method to identify active surface species and determine the reaction pathway of the dynamic processes. The findings show that methoxy, hydroxyl, and formate species are the key reactive intermediates on the Cu/ZnO catalyst, while carbonate species formed at higher temperatures are spectators that do not participate in the reaction. In addition, the MSR reaction on Cu/ZnO undergoes a "formate" route. Typically, methanol absorbs and dissociates to surface methoxy, which then reacts with hydroxyl from the dissociation of water to form surface formate species and finally decomposes to form CO2 and H2. The interfacial sites play key roles in methoxy dehydrogenation and water dissociation. The results highlight the potential of ME-PSD-DRIFTS to provide a detailed molecular level understanding of the reaction mechanism(s) in the MSR reaction and the dynamics of surface catalytic processes for heterogeneous catalysts in general.

Interaction of mineral surfaces with simple organic molecules by diffuse reflectance IR spectroscopy (DRIFT)

Aldol condensation reaction of acetone on MgO nanoparticles surface: An in-situ drift investigation

CaO–NiO/Al2O3 catalysts were prepared by wet impregnation method, keeping the NiO composition constant at 25 wt.% and varying the CaO composition in the range 6–12 wt.%. The catalysts were evaluated for oxidative dehydrogenation (ODH) of ethane with CO2 at atmospheric pressure and in the temperature range of 600–700 °C. The physicochemical characterization of the catalysts was carried out using X-ray diffraction (XRD), BET surface area, Temperature programmed reduction (TPR), Temperature programmed desorption of CO2 (CO2-TPD), H2 chemisorption, Carbon analysis and Fourier transform infrared (FT-IR) spectroscopy. NiO/Al2O3 showed higher ethane and carbon dioxide conversions, but with lower ethene selectivity. The addition of CaO in NiO/Al2O3 reversed the course of reaction leading to high selectivity to ethene, although at reduced conversions. 9 wt.% CaO containing NiO/Al2O3 emerged as the most promising catalyst giving the highest yield of ethene. CaO addition increased the basicity and the coke resistance. The shift in selectivity with CaO addition is explained in terms of more probability for reverse water gas shift reaction on a basic site rather than the hydrocracking reaction on the acidic sites of Ni/Al2O3. The 9 wt.% CaO-25% NiO/Al2O3 catalysts were also prepared by changing the sequence of impregnation and by adopting simultaneous deposition of the two oxides on Al2O3. The activity of these catalysts was compared to identify the best method of catalyst preparation. Ca promotion of NiAl modifies the surface basic property increasing ethene/methane selectivity ratio from 1 to 4, and enhances coke resistance.

Catalyst Characterization and in situ FTIR Studies of Carbon Dioxide Methanation Over Ruthenium Supported on Titania

Ohmic-functionalized type I heterojunction: Improved alkaline water splitting and photocatalytic conversion from CO2 to C2H2