Diffuse Reflectance Infrared Fourier Transform Spectroscopy Spectra Research Articles

Evolution of functional group of lignocellulosic biomass and its delignified form during thermal conversion using synchrotron-based THz and laboratory-based in-situ DRIFT spectroscopy

In the industry, platform chemicals are traditionally synthesized from non-renewable resources. In order to determine the ideal temperature range and associated emissions for the production of platform chemicals from biomass, which is a renewable resource, mechanistic insights into the thermochemical conversion of biomass are needed. Here, the high-resolution synchrotron-based gas-phase THz (Far-IR) spectra and lab-based in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) spectra of both raw and delignified biomass have been studied to identify real-time evolution of the functional groups and any gas-phase secondary reactions during the thermochemical conversion as a function of temperature; these are linked to weight loss measurements through differential thermogravimetry. The high-resolution synchrotron-based technique and DRIFTS were used to acquire the spectra in two different wavenumber ranges of 50–600 cm−1 and 500–4500 cm−1, respectively. The synchrotron-based spectra were used to identify the major gaseous components between 300 and 500 °C of methane, ethane, acetylene and formaldehyde, and their generation followed the order 300 > 400 > 500 °C. The DRIFTS spectra showed that the covalent hydrogen bonds of both raw and delignified biomass was cleaved below 250 °C, between 250 and 300 °C the decarboxylation reaction took place, whereas between 300 and 400 °C platform chemicals (furan, levoglucosan, levoglucosenone) and aromatic compounds were formed from the dehydration of the cellulosic part of the biomass. No changes in the DRIFTS spectra were observed above 400 °C. These results suggest that 300–400 °C is the ideal temperature range for the thermochemical conversion of biomass to platform chemicals. Pyrolysis-gas chromatography/mass spectrometry (Py-GCMS) results demonstrated that the identification of platform chemicals laid the groundwork for large-scale operation.

Rapid and accurate determination of protein content in North Atlantic seaweed by NIR and FTIR spectroscopies

Seaweed is considered a potentially sustainable source of protein for human consumption, and rapid, accurate methods for determining seaweed protein contents are needed. Seaweeds contain substances which interfere with common protein estimation methods however. The present study compares the Lowry and BCA protein assays and protein determination by N-ratios to more novel spectroscopic methods. Linear regression of the height or the integrated area under the Amide II band of diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to predict seaweed protein with good prediction performance. Partial least squares regression (PLSR) was performed on both DRIFTS and near-infrared (NIR) spectra, with even higher prediction accuracy. Spectroscopy performed similar to or better than the calculated N-ratio of 4.14 for protein prediction. These spectral prediction methods require minimal sample preparation and chemical use, and are easy to perform, making them environmentally sustainable and economically viable for rapid estimation of seaweed protein.

Identifying Key Descriptors for the Single-Atom Catalyzed CO Oxidation

Identifying Key Descriptors for the Single-Atom Catalyzed CO Oxidation

Mixed Catalyst SmMn2O5/Cu-SAPO34 for NH3-Selective Catalytic Oxidation.

Low-temperature selective catalytic oxidation (SCO) is crucial for removing the NH3 slip from the upstream of NH3-selective catalytic reduction (NH3-SCR). Herein, combining zeolite Cu-SAPO34 and the active oxidant mullite SmMn2O5, we developed mixed-phase catalysts SmMn2O5/Cu-SAPO34 by grinding powder mixtures to achieve a low-temperature activity and a reasonable N2 selectivity. The physicochemical properties of the catalysts were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) measurement, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The evaluation of NH3 oxidation activity showed that for 30 wt % SmMn2O5/Cu-SAPO34, 90% NH3 conversion was at a temperature of 215 °C in the presence of 500 ppm NH3 and 21% O2 balanced with N2. The in situ DRIFTS spectra reveal the internal SCR mechanism (i-SCR), i.e., NH3 oxidizing to NOx on mullite and NOx subsequently to proceed with SCR reactions, leading to higher conversion and selectivity over the mixed catalysts. This work provides a strategy to design the compound catalyst to achieve low-temperature NH3 oxidation via synergistic utilization of the advantages of each individual catalyst.

DRIFTS investigation of toluene oxidation on CeO2 nanoparticles

The oxidation mechanism of toluene on the surface of heat-treated CeO2 nanoparticles was investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). When introduced to the CeO2 surface, toluene either chemisorbs to an oxygen bound to a single cerium atom creating monobound (m) benzyloxy or to an oxygen bound to two neighboring cerium atoms forming bridged (b) benzyloxy. From the DRIFTS analysis, benzoate production is directly dependent on the presence and oxidation of b-benzyloxy groups. Using temperature dependent peak height analysis of the DRIFTS spectra, the oxidation state of specific vs(OCO) bands of bidentate (bdt) benzoate groups are identified through pairing with their va(OCO) counterparts. Surface lattice oxygens and b‑hydroxyl groups are found to facilitate the chemisorption of toluene as the two surface benzyloxy groups. Once toluene reacts with the substrate, surface hydroxyls react with m-benzyloxy groups to create additional b-benzyloxy groups as well as enabling the transformation of b-benzyloxy groups to bdt-benzoate groups. The previously unclear intermediate transformation steps of toluene to bdt-benzoate on the surface of CeO2 and surface hydroxyls species role in said transformation is unveiled through the use of peak height analysis of the collected DRIFTS spectra.

DRIFTS investigation of methanol oxidation on CeO2 nanoparticles

The mechanism of the oxidation of methanol on the surface of heat treated CeO2 nanoparticles was studied using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The study was carried out under high vacuum to ensure no interference from unreacted physisorbed methanol and compared to a similar analysis under pseudo-flow conditions. When methanol reacts with the CeO2 surface, it either chemisorbs to a single cerium atom creating monobound (m) methoxy or to two neighboring cerium atoms forming bridged (b) methoxy groups. From the evacuated analysis, formate production depends directly on the presence and transformation of b-methoxy groups. Hydroxyls are found to facilitate the formation of the two surface methoxy groups, react with m-methoxy groups creating additional b-methoxy groups, and enable the transformation of b-methoxy groups to bidentate formate groups. The reaction mechanism is elucidated through the use of temperature dependent peak height analysis of the collected DRIFTS spectra which are correlated to the transforming surface bound species.

Properties of a formaldehyde-free tannin adhesive and mechanical strength of oriented bamboo scrimber board bonded with it

Abstract In this study, oriented bamboo scrimber board (OBSB) was manufactured with a synthesized formaldehyde-free tannin adhesive. The chemical properties of the tannin adhesive were analyzed with 13C nuclear magnetic resonance spectroscopy (13C-NMR) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT). Results revealed that 70% aqueous acetone extractives of Acacia confusa bark (AcBAE) contained abundant phenolic compounds and condensed tannins comprising mainly B-type flavonoid bonds. Moreover, cross polarization magic angle spinning (CP/MAS) 13C-NMR mapping of cured Acacia confusa bark tannin glue (AcBTanGlu) revealed that condensed tannin reacted with hexamethylenetetramine to form a polymer with a cross-link structure through a polymerization mechanism. According to the results obtained from gas chromatography-flame ionization detector (GC-FID) analysis, no formaldehyde was emitted from AcBTanGlu-glued OBSB. Thermogravimetric analysis indicated that AcBTanGlu significantly improved the thermal stability of AcBAE after the curing reaction. Comparison of the DRIFT spectra of bamboos before and after AcBTanGlu-glued treatment indicated AcBTanGlu did not impact the chemical functional properties of the bamboo. Compared to phenol formaldehyde (PF) and urea formaldehyde (UF)-glued OBSBs, AcBTanGlu-glued OBSBs statistically had lower modulus of elasticity (MOE) and modulus of rupture (MOR). As for the nail withdraw resistance, AcBTanGlu-glued OBSBs are statistically comparable to PF-glued OBSBs and higher than UF-glued OBSBs.

Visualization and Quantification of the Laser-Induced ART of TiO2 by Photoexcitation of Adsorbed Dyes

Dye-pretreated anatase TiO2 films, commonly used as photoanodes in dye sensitized solar cells (DSSC), were utilized as a model system to investigate the laser-induced anatase to rutile phase transformation (ART), using N719 dye, N749 dye, D149 dye, and MC540 dye as photo-sensitizers. The visible lasers (532 and 785 nm) used for Raman spectroscopy were able to transform pure anatase into rutile at the laser spot when excitation of the dye sensitizer caused an electron injection from the excited state of the dye molecule into the conduction band of the TiO2. The three dyes with carboxylic acid anchor groups (N719, N749 and D149 dyes) experienced ART upon dye excitation; diffuse reflectance infrared Fourier transform (DRIFTS) and Raman spectra validated that these dyes were chemisorbed to the semiconductor surface. The MC540 dye with a sulfonic acid anchor group did not experience ART and the DRIFTS and Raman spectra were inconclusive about the chemisorption of this dye to the TiO2. A TiO2 calibration curve and percent rutile contour plots developed for this project are able to quantify the amount of rutile created at the surface of the samples. These improved chemical images which map rutile concentration help to visualize how ART propagates from the center of the laser spot to the surroundings. Factors such as visible light absorption and anchor groups that covalently bind to the semiconductor play a key role in effective laser induced ART.

An in-situ DRIFTS study of acetone adsorption mechanism on TiO2 nanoparticles.

In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) has been used to investigate the adsorption and catalytic reaction of acetone on TiO2 surfaces. The adsorption of acetone has been investigated on hydrated (as-received from the provider) as well as dehydrated TiO2 nanoparticles. On both samples, acetone shows absorption bands results from the vibrational modes of acetone adsorbed molecules. The DRIFTS spectra indicate that acetone goes into a self-condensation reaction then it dehydrated yielding mesityl oxide. Formation of formaldehyde was observed only on as received sample and it was probably activated as a result to suppress mesityl oxide formation. This suppressed formation is a result of the existence of adsorbed H2O on the surface of as received TiO2. Adsorbed water is not favorable for aldolization/dehydration reaction because it can block the active sites for mesityl oxide formation. Outcomes of the current study provide fundamental insight into acetone adsorption and catalytic reaction on TiO2 nanoparticles. Specifically, this investigation demonstrates the adsorption mechanism of acetone on TiO2 surface and the role of presenting hydroxyl group on the TiO2 surface.

Combined spatially resolved operando spectroscopy: New insights into kinetic oscillations of CO oxidation on Pd/γ-Al2O3

Spatially resolved, combined energy dispersive EXAFS (EDE) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements have been performed over a fixed catalyst bed of Pd/γ-Al2O3 during kinetic oscillations of CO oxidation. The kinetic oscillations of CO oxidation over Pd (or for that matter Pt or Rh) catalysts are a complicated phenomenon that require characterisation techniques with high time resolution and spatial resolution in order to make links between catalyst structure and surface reactivity. By measuring the extent of Pd oxidation at the nanoparticle surface, from Pd K-edge EDE, and matching this with the CO coverage, from DRIFTS spectra, at multiple positions of the fixed bed reactor it is found that the majority of the catalyst undergoes a sharp transition from the CO poisoned catalyst to the highly active, oxidised Pd surface. This transition occurs initially at the end of the catalyst bed, nearest the outlet, and propagates upstream with increasing temperature of the reactor. The oscillations in Pd surface oxide formation and CO coverage are observed only in the first ∼1 mm of the bed, which gives rise to oscillations in CO2 and O2 concentrations observed by end-pipe mass spectrometry after the light-off temperature. The catalyst initially exists as less active, CO poisoned metallic Pd nanoparticles before light-off which transition to a highly active state after light-off when the Pd nanoparticle surface becomes dominated by chemisorbed oxygen. Kinetic oscillations only occur at the front of the catalyst bed where there is sufficient concentration of CO in the gas phase to compete with O2 for adsorption sites at the catalyst surface. We demonstrate the complex nature of the evolving catalyst structure and surface reactivity during catalytic operation and the need for spatially resolved operando methods for understanding and optimising catalyst technologies.

Influence of {111} nanofaceting on the dynamics of CO adsorption and oxidation over Au supported on CeO2 nanocubes: An operando DRIFT insight

Abstract CO adsorption and further reaction with O2 on two Au/CeO2 model systems have been investigated by operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) in order to unveil the active sites for CO oxidation. One of the ceria supports was constituted by crystallites depicting a nanocube shape bounded mostly by {100} planes, whilst the second one was consisted of nanocubes whose {110} surfaces were reconstructed into {111}-nanofacets with a zig-zag shape. The deconvolution of the CO adsorption bands and a detailed analysis of the time-evolution of these bands were also carried out. These studies evidenced a fast adsorption of CO over Au° and then Auδ--CO bands appeared during exposure to CO, in parallel with the appearance of Ce3+ features. Such changes suggest that CO adsorption process starts on Au sites on the low coordinated sites of the surface of the Au nanoparticles and their transfer to the interface sites. By comparing the nanostructure of the two catalysts, the Auδ--CO species could be fruitfully related to CO adsorption on sites located at the Au||CeO2 perimeter. The sample containing gold nanoparticles dispersed over the {111}-nanofaceted CeO2 nanocubes, which retained a higher amount of gold nanoparticles, depicts higher contribution of Auδ−−CO bands than the other Au catalyst in the DRIFT spectra. The dynamic DRIFT study clearly revealed that the CO species adsorbed on Auδ- sites were the most reactive ones in both gold supported systems for CO oxidation. This explains much higher TOF values observed on the catalyst prepared on the surface reconstructed support. A detailed analysis on the reactivity was performed by modulation excitation spectroscopy (MES). The presence of peroxide surface species (O22-) in nanofaceted {111} could lead to higher catalytic activity than that of gold on the non-reconstructed catalyst.

Capabilities and limitations of handheld Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for the analysis of colourants and binders in 20th-century reverse paintings on glass

A non-invasive method has been carried out to show the capabilities and limitations of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for identifying of colourants and binders in modern reverse glass paintings. For this purpose, the reverse glass paintings “Zwei Frauen am Tisch” (1920–22), “Bäume” (1946) (both by Heinrich Campendonk), “Lofoten” (1933) (Edith Campendonk-van Leckwyck) and “Ohne Titel” (1954) (Marianne Uhlenhuth), were measured. In contrast to other techniques (e.g. panel and mural painting), the paint layers are applied in reverse succession. In multi-layered paint systems, the front paint layer may no longer be accessible. The work points out the different spectral appearance of a given substance (gypsum, basic lead white) in reverse glass paintings. However, inverted bands, band overlapping and derivative-shaped spectral features can be interpreted by comparing the spectra from the paintings with spectra from pure powders and pigment/linseed oil mock-ups. Moreover, the work focuses on this method's capabilities in identifying synthetic organic pigments (SOP). Reference spectra of three common SOP (PG7, PY1, PR83) were obtained from powders and historical colour charts. We identified PR83 and PY1 in two reverse glass paintings, using the measured reference spectra. The recorded DRIFTS spectra of pure linseed oil, gum Arabic, mastic, polyvinyl acetate resin and bees wax can be used to classify the binding media of the measured paintings.

Morphology-Dependent Properties of Cu/CeO2 Catalysts for the Water-Gas Shift Reaction

CeO2 nanooctahedrons, nanorods, and nanocubes were prepared by the hydrothermal method and were then used as supports of Cu-based catalysts for the water-gas shift (WGS) reaction. The chemical and physical properties of these catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption/desorption, UV-Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR) and in situ diffuse reflectance infra-red fourier transform spectroscopy (DRIFTS) techniques. Characterization results indicate that the morphology of the CeO2 supports, originating from the selective exposure of different crystal planes, has a distinct impact on the dispersion of Cu and the catalytic properties. The nanooctahedron CeO2 catalyst (Cu-CeO2-O) showed the best dispersion of Cu, the largest amount of moderate copper oxide, and the strongest Cu-support interaction. Consequently, the Cu-CeO2-O catalyst exhibited the highest CO conversion at the temperature range of 150–250 °C when compared with the nanocube and nanorod Cu-CeO2 catalysts. The optimized Cu content of the Cu-CeO2-O catalysts is 10 wt % and the CO conversion reaches 91.3% at 300 °C. A distinctive profile assigned to the evolution of different types of carbonate species was observed in the 1000–1800 cm−1 region of the in situ DRIFTS spectra and a particular type of carbonate species was identified as a potential key reaction intermediate at low temperature.

Relationship between the CO sensing performance of micro-thermoelectric gas sensors and characteristics of PtPd/Co3O4 and PtPd/SnO2 catalysts

The sensing properties of CO over PtPd/Co3O4 and PtPd/SnO2 catalysts in a micro-thermoelectric gas sensor (micro-TGS) were investigated by in situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFT) and scanning transmission electron microscopy (STEM), in comparison with other catalysts (AuPtPd/Co3O4, AuPtPd/SnO2, Au/Co3O4, and Au/SnO2) which is reported in our previous works. The catalysts exhibited the following response of voltage signals to CO at 200°C: PtPd/Co3O4>PtPd/SnO2>AuPtPd/SnO2∼AuPtPd/Co3O4>Au/Co3O4>Au/SnO2. From DRIFT spectra, linear and bridge bonds corresponding to Pt–CO and Pd–CO were observed for PtPd/Co3O4 and PtPd/SnO2 catalysts, respectively. In contrast, the Au–CO interaction peak was not clearly observed in the AuPtPd-loaded catalysts. From the STEM observation of the PtPd- and AuPtPd-loaded catalysts, Pt and Pd nanoparticles were well dispersed on catalyst supports. On the other hand, Au nanoparticles formed aggregates with Pt or Pd nanoparticles having a diameter of 10–20nm. Au in the AuPtPd-loaded catalyst was considered to exhibit a low activity for CO oxidation, and the oxidation of CO mainly occurred over Pt and Pd particles. From these results, PtPd/Co3O4 and PtPd/SnO2 are suitable for use as combustion catalysts in micro-TGS for CO detection.

Interpretation of infrared spectra for OM characterization of soil structural surfaces of Bt‐horizons

AbstractThe surfaces of macropores or aggregates can act as hot spots for biogeochemical processes and solute transport during preferential flow. For the characterization of organic matter (OM) at macropore surfaces non‐destructive methods have been applied such as diffuse reflectance infrared Fourier transform spectroscopy (DRIFT). However, effects of organic components on DRIFT signal intensities are often difficult to distinguish from those of mineral components. Here, DRIFT spectra from intact earthworm burrow walls and coated cracks were re‐evaluated to improve the interpretation of C–H and C=O bands. We compared DRIFT and transmission Fourier transform infrared (FTIR) spectra of entire samples that were from the same pedogenetic soil horizon (Bt) but different in mineral composition and texture (i.e., glacial till vs. loess). Spectra of incinerated samples were subtracted from the original spectra. Transmission FTIR and DRIFT spectra were almost identical for entire soil samples. However, the DRIFT spectra were affected by the bulk mode bands (i.e., wavenumbers 2000 to 1700 cm−1). These bands affected spectral resolution and reproducibility. The ratios between C–H and C=O band intensities as indicator for OM quality obtained with DRIFT were smaller than those obtained from transmission FTIR. The results demonstrated that DRIFT and transmission FTIR data required separate interpretations. DRIFT spectroscopy as a non‐destructive method for analyzing OM composition at intact surfaces in structured soils could be calibrated with information obtained with the more detailed transmission FTIR and complementary methods. Spectral subtraction procedure was found useful to reduce effects of mineral absorption bands. The improved DRIFT data may be related to other soil properties (e.g., cation exchange capacity) of hot spots in structured soils.

Cell wall compositional changes during incubation of plant roots measured by mid-infrared diffuse reflectance spectroscopy and fiber analysis

Plant roots, particularly the constituents of root cell walls (hemicellulose, cellulose and lignin) are important contributors to soil organic matter. Little is known about the cell wall composition of many important crop species or compositional changes as roots decay. The objectives of this study were to quantify changes in root cell wall composition during a four week laboratory incubation by forage fiber analysis and characterize those changes using diffuse reflectance infrared fourier transform spectroscopy (DRIFTS). The roots of six important crop, forage and native grass species were incubated at 25°C and sampled weekly. Alfalfa lost 78% of initial mass over four weeks, while the remaining species lost between 19% and 38%. For all species the majority of this loss occurred during Week 1, and only alfalfa mass loss was significant (P<0.05) each week. The trends observed for whole root decomposition were paralleled by the decomposability of root cell walls. Significant changes in hemicellulose, cellulose and lignin concentrations over time were only observed in alfalfa roots. Significant changes in decomposability of these constituents was likewise only observed in alfalfa, with cellulose the most decomposable fraction, followed by hemicellulose and lignin. Analysis by DRIFTS supported the fiber analysis results and revealed important changes in root cell wall composition. The disappearance of peaks due to starch in the perennial alfalfa and switchgrass roots following Week 1 helped to explain the greater initial mass loss in both of these species relative to the roots of the annuals. The spectral data also illustrated the resistance of alfalfa lignin to decomposition, the preservation of carbonyl compounds and the degradation of readily decomposed proteins. Finally, changes potentially indicative of wax compound preservation were found in the DRIFTS spectra of alfalfa even though the amount of wax was too small to quantify by fiber analysis. This research study reveals differences in the rate at which crop roots decompose and important changes that can occur in readily decomposable roots over relatively short time scales. These results provide valuable information contributing to the understanding and prediction of short term soil organic matter dynamics which will help to predict possible impact of management changes or soil disturbance on soil health and productivity as well as long term organic C stabilization and the potential for C sequestration.

Introduction to the special issue ‘Tracer Applications in Sediment Research’

Introduction to the special issue ‘Tracer Applications in Sediment Research’

Discrimination between roasted coffee, roasted corn and coffee husks by Diffuse Reflectance Infrared Fourier Transform Spectroscopy

Coffee has been the target of fraudulent admixtures with cheaper materials, including coffee husks and other roasted grains. Given the successful application of spectroscopic methods in the field of food adulteration as fast and reliable routine techniques, the objective of this work was to evaluate the feasibility of employing Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for discrimination between roasted coffee and common adulterants (roasted corn and coffee husks). Arabica coffee beans, coffee husks and ground corn kernels were submitted to light, medium and dark roasts at temperatures ranging from 200 to 260 °C. Principal Components Analysis of the DRIFTS spectra provided separation of the samples into three groups: coffee, coffee husks and corn. Classification models were developed based on Linear Discriminant Analysis, and such models provided complete discrimination (100% recognition and prediction) between roasted coffee, pure adulterants (corn and coffee husks) and adulterated coffee samples. Such results indicate that DRIFTS can be employed for discrimination between coffee and its common adulterants.

In situ studies of CeO2-supported Pt, Ru, and Pt–Ru alloy catalysts for the water–gas shift reaction: Active phases and reaction intermediates

The activity and structure of three CeO2-based catalysts (Pt–CeO2, Ru–CeO2, and Pt–Ru alloy-CeO2) active for water–gas shift reaction (WGSR) are studied by in situ X-ray diffraction (XRD), operando X-ray absorption near edge spectroscopy (XANES), operando diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS), and high-resolution transmission electron microscopy (HRTEM) in order to understand and thus correlate both bulk and surface dynamics with performance. All systems investigated displayed a high WGS activity. Temperature-resolved XRD (under CO or H2 environment) indicated an additional expansion of the CeO2 crystal lattice at 100–250°C for the catalysts compared to pure CeO2. This extra lattice expansion is due to additional oxygen removal from CeO2 promoted by the deposited Pt, Ru, or Pt–Ru alloy particles; CO showed an accelerated expansion when compared to that of H2. DRIFTS spectra revealed the formation of substantial amounts of formates (HCOO–) on Pt–CeO2 during WGSR, while formates on PtRu–CeO2 and Ru–CeO2 were at a much lower level. For all catalysts, formate species totally disappeared by 350°C. The inhibition of formate formation on PtRu–CeO2 points to a modification of the chemical properties of Pt by alloying with Ru. The fact that the inhibition of Pt-bound formate species does not affect the catalytic activity implies that they are probably merely spectators on Pt, or at least not involved in the main reaction pathway. While the Pt–Ru alloy was not more active than Pt–CeO2, the alloyed catalyst did show a reduced generation of methane under WGSR conditions compared to Ru–CeO2. Pt XANES data confirmed the reduction of Pt in both Pt–CeO2 and PtRu–CeO2 with increasing temperature in the WGSR environment. HRTEM showed that the reduced PtRu–CeO2 catalyst was composed of a Pt–Ru alloy with a mean particle size of 2nm well dispersed over the CeO2 support. Overall, the work indicates that a Pt–Ru alloy supported on CeO2 is an active and selective catalyst for WGSR.

Discrimination between defective and non-defective roasted coffees by diffuse reflectance infrared Fourier transform spectroscopy

The objective of this work was to evaluate the feasibility of employing Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for discrimination between defective and non-defective coffees after roasting and grinding. Defective (black, immature and sour) and non-defective Arabica coffee beans were submitted to light, medium and dark roasts at 220, 235 and 250 °C. Principal Components Analysis of the DRIFTS spectra (normalized or not) and of the first derivatives of the spectra provided separation of the samples into four groups: non-defective, black, dark sour and light sour, with immature beans scattered among the sour samples. Classification models were developed based on Linear Discriminant Analysis and recognition and prediction abilities of these models ranged from 95 to 100%. Such results indicate that DRIFTS presents potential for the development of a fast and reliable analytical methodology for discrimination between defective and non-defective coffee after roasting and grinding.