In-situ DRIFT spectroscopy

Following the transient concentration of gaseous and adsorbed carbon containing species during the cycle by in situ DRIFT spectroscopy lead to a preliminary but quantitative description of the main steps which control the various sequences of the process [6]. In order to further investigate this mechanism of C storage assisted by support, a modeling study was initiated on the basis of the experimental evidences reported in [6] and summarized below. 

Demoulin O, Navez M, Ruiz P. Investigation of the behaviour of a Pd/Y-Al203 catalyst during methane combustion reaction using in situ DRIFT spectroscopy. Appl Catal A. 2005 295 59. 

The commercial Pd/Al203 catalyst used in this pilot scale study was characterized via DRIFT spectroscopy. In situ DRIFT spectra of carbon monoxide, MIBK, acetone... 

The heterogenization of MAO-activated Nd(z 3-C3H5)3 dioxane on MAO-functionalized Si(>2 was reported by T. Riihmer et al. [307]. In situ DRIFT (= diffuse reflectance infrared Fourier transform) spectroscopy and TPRS (= temperature-programmed reaction spectroscopy) were employed... 

Keywords Hydroialciie-likc compounds Hydroxylation of Phenol Selective oxidation Structure-activity relationships In situ powder X-ray diffraction In situ DRIFT FT-IR spectroscopy Thermal analysis (TGA-DTA-EGA-TPRO) Synthesis methodology Influence of reaction parameters Ordered network Synergism... 

Olefin reactions were, among other reactions, also studied in situ by DRIFT spectroscopy as described in an review article by Maroni et al. [883], where a cell was used similar to that mentioned in Sect. 4.2 (cf. [176]). Salzer et al. [884] described in-situ DRIFT experiments of activation of zeolite catalysts, for instance, NH4-erionite, where they also employed the commercially available, heatable DRIFT cell mentioned in Sect. 4.2. 

Both chemical and physical processes take place during calcination and activation. Ligand decomposition from the metal complex can be monitored with in situ vibrational spectroscopy, for example, using diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS). In the case of a transition metal ion, the metal oxidation state can be tracked as a function of time and temperature using in situ UV-vis spectroscopy. Finally, the formation of metal clusters and nanoparticles can be monitored using XRD, similar to that described for the synthesis of silicalite-1. 

The study of the dynamics of N isotope transfer under adsorption-desorption equilibrium (NO -1- O2 + He) revealed two types of NOx complexes, and their concentrations and formation rates (depending on NO and O2 concentrations) were estimated. According to in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) data, these complexes are assigned to nitrite-nitrate (1520 cm" ) and N02 species (2130 cm" ). Note that nitrite-nitrates and N02 differ clearly in the rates of their formation. Under the reaction conditions, the concentrations of both active species drop considerably. Therefore, two parallel reaction pathways were proposed that involve both active complexes. The rates of NOx complexes interaction with methane were also calculated, and the reaction with participation of N02 species was shown to proceed about 2.5 times faster than that of nitrite-nitrate. The N02 species was determined to form at the interface between CoO clusters and acid OH groups in zeolite (or at the paired Co -OH sites). This finding agrees well with in situ DRIFTS data that indicates that the N02 formation correlates with a drop in the acid OH group band intensity. 

The experimental system consists of three sections (i) a gas metering section with interconnected 4-port and 6-port valves, (ii) a reactor section including an in-situ diffused reflectance infrared Fourier transform spectroscopy reactor (DRIFTS) connected to tubular quartz reactor, (iii) an effluent gas analysis section including a mass spectrometer or a gas chromatograph (9). 

DRIFT spectroscopy was used to determine Av0h shifts, induced by adsorption of N2 and hexane for zeolite H-ZSM-5 (ZSM-a and ZSM-b, Si/Al=15.5 and 26), H-mordenite (Mor-a and Mor-b, Si/AI— 6.8 and 10) and H-Y (Y-a and Y-b, Si/Al=2.5 and 10.4) samples. Catalysts were activated in 02 flow at 773 K in situ in the DRIFTS cell and contacted than with N2 at pressures up to 9 bar at 298 K or with 6.1% hexane/He mixture at 553 K, i.e., under reaction conditions. Catalytic activities of the solids were measured in a flow-through microreactor and kapp was obtained as slope of -ln(l-X0) vs. W/F plots. The concentration of Bronsted acid sites was determined by measuring the NH4+ ion-exchange capacity of the zeolite. The site specific apparent rate constant, TOFBapp, was obtained as the ratio of kapp and the concentration of Bronsted acid sites. 

Diffuse refleetance infrared spectroscopy (DRIFTS) provides useful information about the degree of ineorporation and nature of the immobilized eomplex in supported reagents. We have studied the supports as well as the supported reagents containing the immobilized eomplexes by this form of infrared spectroscopy where samples in the solid state are examined to determine the nature species under examination. We discuss here the infrared speetral evidenee of two supported materials - Co(III)-CMS3, prepared by the in-situ method and Co(III)-CMS4 whieh has been prepared by the ligand substitution route. 

Infrared spectroscopy of adsorbed CO is a useful characterization tool for dendrimer-templated supported nanoparticles, because it directly probes particle surface features. In these experiments, which are performed in a standard infrared spectrometer using an in-situ transmission or DRIFTS cell, a sample of supported DENs is first treated to remove the organic dendrimer. Samples are often reduced under H2 at elevated temperature, flushed with He, and cooled to room temperature. Dosing with CO followed by flushing to remove the gas-phase CO allows for the spectrum of surface-bound CO to be collected and evaluated. Because adsorbed CO stretching frequencies are sensitive to surface geometric and electronic effects, it is potentially possible to evaluate the relative effects of each on nanoparticle properties. 

Ferri D, Kumar MS, Wirz R, et al. First steps in combining modulation excitation spectroscopy with synchronous dispersive EXAFS/DRIFTS/mass spectrometry for in situ time resolved study of heterogeneous catalysts. Phys Chem Chem Phys. 2010 12 5634. 

High quality IR spectra of different carbon surfaces were obtained by photo-thermal beam deflection spectroscopy (IR-PBDS) [123,124]. This technique was developed with the intention of providing an IR technique that could be used to study the surface properties of materials that are difficult or impossible to examine by conventional means. Recently, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) has been successfully applied to study the effect of different pretreatments on the surface functional groups of carbon materials [101,125-128]. Several studies aiming to improve the characterization of the carbon electrode surface and the electrode-electrolyte interface have been carried out using various in situ IR techniques [14,128-132]. The development of in situ spec-troelectrochemical methods has made it possible to detect changes in the surface oxides in electrolyte solutions during electrochemical actions. 

The catalysts were characterized by N2 adsorption-desorption isotherms, thermogravimetric analysis (TGA), temperature-programmed desorption of ammonia (NH3-TPD), X-ray diffraction (XRD), Raman spectroscopy, in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X-ray photoelectron spectroscopy (XPS). The procedures and experimental conditions have been detailed elsewhere [9]. 

Accordingly, transient kinetic techniques which are able to provide unique information on the actual state of a working catalyst within a very short period of time [13,14] were applied to this complex and unstable catalytic system. Non-steady-state and steady-state isotopic transient kinetics (NSSTK and SSITK) combined with in situ diffuse reflectance infrared Fourier transformed spectroscopy (DRIFT) and temporal analysis of product (TAP) were performed in order to analyse some of the above mentioned key steps of the aromatisation process. 

In fresh conditions the catalyst was analyzed by diffuse reflectance infrared Fourier transform (DRIFT-) spectroscopy to determine the NO adsorption state. The DRIFT spectra were measured in the wavelength range of 1500-2300 cm l on a Bruker IFS 88 spectrometer equipped with a Spectra-Tech in situ cell. The spectra resolution was 2 cm T The spectra were recorded in situ at 225°C in flowing 2% NO in Helium (50 cm /min) after preconditioning for 0.5 h at 400°C in hydrogen (50 cm /min). 

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