DRIFT Spectroscopy Research Articles

IR spectroscopy of coal 2. Analysis of ash content from the difference spectra of minerals

Difference spectra obtained after subtraction of the model spectrum for the organic mass are used to analyze the ash content of coal-mineral mixtures by DRIFT spectroscopy in the intermediate IR range. For quantitative determination of the ash content, calibration is based on projection onto latent structures (PLS), with preliminary screening. The resulting model is simple and robust.

Estimation of the fractions of different nuclear iron species in uniformly metal-exchanged Fe-ZSM-5 samples based on a Poisson distribution

A simple calculation method is presented which allows for estimation of the fractions of different iron species in Fe-ZSM-5 based on statistical considerations. Under the assumption of uniformly distributed iron, the probability with which Fe–O–Fe bridged and higher nuclear Fe-species are formed in a Fe-ZSM-5 sample may be calculated based on a simple Poisson distribution. The results of these calculations were compared with DR-UV/vis and DRIFT spectroscopy measurements on a variety of Fe-ZSM-5 samples with different Fe/Al ratios. Moreover, the calculated concentration profiles were checked with literature data from other studies. It is shown that the fractions of different iron species in Fe-ZSM-5 can be estimated by this calculation method with satisfactory accuracy, provided that the metal-exchange process resulted in a uniform distribution of iron in the zeolite. The method may be useful for verifying of analytical results, understanding of observed activity patterns and may facilitate the identification of activity–structure relationships.

Solid State Mechanochemical Activation of Silybum marianum Dry Extract With Betacyclodextrins: Characterization and Bioavailability of the Coground Systems

Silybum marianum dry extract, whose therapeutic use is partially restricted by the insolubility in water of its main flavonolignans, was subjected to a mechanochemical activation process in planetary mill using betacyclodextrins as carriers. After optimization of the operating conditions according to an established theoretical model, the best active-to-carrier proportion was selected from the preliminary trials. When using the optimized conditions, the mechanochemical process permits an improvement of the physico-chemical properties of the active, which reaches an “activated” solid state, that is stable for at least 1 year. In fact, XRD, DRIFT and Raman spectroscopy analyses showed that the main extract component, Silybin, completely lost its crystalline structure after co-grinding with betacyclodextrins and formed weak interactions with the carrier. The powder characteristics remarkably changed after co-grinding, leading to a sample with a very small mean diameter and with a twofold increase of the specific surface area in comparison to the dry extract. The activated solid state of the coground systems remarkably enhanced the in vitro drug dissolution kinetics with consequent improved oral bioavailability. Furthermore, the in vivo studies on rats revealed a 6.6-fold bioavailability increase respect to the S. marianum Italian commercial product used as reference (Silirex® 200 capsules). © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:4119–4129, 2009

IR spectroscopic study of the basicity of aminated silica gels

The aminated silica gels SiO2/SOCl2/NH3 (I), SiO2/SiCl4/NH3 (II), SiO2/BCl3/NH3 (III), and SiO2/γ-aminopropyltriethoxysilane (SiO2/APTES, IV) have been synthesized. According to DRIFT spectroscopy and chemical analysis data, the surface amino groups of I–III are “free,” while those of IV interact with the surface OH groups of the silica gel and with one another. The strength of basic sites has been measured on the proton affinity (PA) scale as the shift of the ν(CD) band of adsorbed deuterochloroform. The basicity of an aminated silica gel depends on its chemical composition. Silica gel IV (PA = 938 kJ/mol) is a stronger base than I–III (PA = 829 kJ/mol). As the basicity of the NH2 group decreases, the N-H stretching band shifts to higher frequencies.

Chemical characterization of municipal wastewater sludges produced by two-phase anaerobic digestion for biogas production

In the present study, the chemical features of municipal wastewater sludges treated in two-phase separate digesters (one for acetogenesis and the other one for methanogenesis), were characterized by using chemical analysis, stable carbon isotope ratios (delta(13)C), HS-SPME-GC-MS, TG-DTA analysis and DRIFT spectroscopy. The results obtained showed that sludges from acetogenesis and methanogenesis differed from each other, as well as from influent raw sludges. Both processes exhibited a diverse chemical pattern in term of VFA and VOC. Additional variations were observed for delta(13)C values that changed from acetogenesis to methanogenesis, as a consequence of fermentation processes that led to a greater fractionation of (12)C with respect to the (13)C isotope. Similarly, the thermal profiles of acetogenesis and methanogenesis sludges greatly differed in terms of heat combustion produced. These changes were also supported by higher lipid content (probably fatty acids) in acetogenesis than in methanogenesis, as also shown by DRIFT spectroscopy.

DRIFTS study of the interaction of the internal donor in TiCl 4/di-n-butyl phthalate/MgCl 2 catalysts with AlEt 3 cocatalyst

The interaction of di-n-butyl phthalate (DBP as the internal donor) with AlEt 3 cocatalyst was studied by DRIFT spectroscopy for the DBP/MgCl 2 sample and supported TiCl 4/DBP/MgCl 2 catalysts. For DBP/MgCl 2 sample, it was shown that AlEt 3 partially removes all types of DBP complexes from the MgCl 2 surface and adsorbs on surface sites released by the removal of DBP. In the case of supported catalysts, the cocatalyst predominantly removes more weak DBP complexes. In addition, the cocatalyst completely removes loosely coordinated DBP and surface complexes of phthaloyl chlorides formed at the catalyst preparation. A part of removed DBP can adsorb again on the catalyst surface as complexes with surface alkylaluminum chloride compounds. The external donor alkylalkoxysilane does not markedly influence the removal of DBP complexes from the catalyst surface.

Simultaneous quantitative analysis of mebendazole polymorphs A–C in powder mixtures by DRIFTS spectroscopy and ANN modeling

In the present study, a simple method, based on diffuse reflectance FTIR spectroscopy (DRIFTS) and artificial neural network (ANN) modeling is developed for the simultaneous quantitative analysis of mebendazole polymorphs A–C in powder mixtures. Spectral differences between the polymorphs are elucidated by computationally assisted band assignments on the basis of quantum chemical calculations, and subsequently, the spectra are preprocessed by calculation of 1st and 2nd derivatives. Then ANN models are fitted after PCA compression of the input space. Finally the predictive performance of the ANNs is compared with that of PLS regression. It was found that simultaneous quantitative analysis of forms A–C in powder mixtures is possible by fitting an ANN model to the 2nd derivative spectra even after PCA compression of the data (RMSEP of 1.75% for form A, 1.85% for B, and 1.65% for C), while PLS regression, applied for comparison purposes, results in acceptable predictions only within the 700–1750 cm −1 spectral range and after direct orthogonal signal correction (DOSC), with RMSEP values of 2.69%, 2.68%, and 3.40% for forms A, B, and C, respectively. Application of the ANN to commercial samples of raw material and formulation (suspension) proved its suitability for the prediction of polymorphic content.

Thermally Induced Radical Hydrosilylation for Synthesis of C18 HPLC phases from Highly Condensed SiH Terminated Silica Surfaces

Silicon hydride terminated silica surfaces were prepared at high temperatures by a chlorination-reduction sequence. SiH groups are desired for further surface modification as an alternative to the native silanol groups which are unfavorable for RPLC applications. Only few silanol groups remain in these materials and mostly SiH moieties with the highest degree of cross-linking are obtained. The retention properties of basic analytes on the SiH terminated material confirm that the surfaces is mostly free of silanols and that therefore the remaining SiOH groups are bulk species. A reagentless, radical initiated hydrosilylation reaction is introduced for the functionalization of the hydride terminated surface with 1-octadecene. (13)C CP/MAS NMR and DRIFT spectroscopy demonstrate the reaction of the carbon-carbon double bond and the SiH group as well as the linkage of C18 groups to the silica surface. These novel C18 materials show promising performance in RPLC separation, especially for the separation of organic bases.

拡散反射FT-IRおよびXAFS用高圧セルの開発とそれを用いた触媒表面のin-situ観察

拡散反射FT-IRおよびXAFS用高圧セルの開発とそれを用いた触媒表面のin-situ観察

Aspects of the Role of Hydrogen in H2-Assisted HC–SCR Over Ag–Al2O3

The role of hydrogen in H-2-assisted HC-SCR of NOx over Ag-Al2O3 is investigated by XPS and in situ DRIFT spectroscopy. Hydrogen does not reduce the surface silver species to metallic silver, however direct reduction of surface nitrates by hydrogen is observed. It is proposed that one important role of hydrogen is the removal of nitrates from the Ag-Al2O3 surface.

Structural differences of Chernozem soil humic acids SEC–PAGE fractions revealed by thermal (TG–DTA) and spectroscopic (DRIFT) analyses

Humic acid extracted from the A horizon of a Chernozem soil and their different molecular size (MS) fractions obtained by SEC–PAGE were investigated using thermal (TG–DTA), spectroscopic (DRIFT) and isotopic (δ 13C) analyses. Moreover, the molecular structure of the high temperature stable fraction (residues above 400 °C) was studied by DRIFT spectroscopy. The lowest MS fraction (C + D) was characterized by the highest content of aromatic compounds and by the lowest content of aliphatic and carboxyl groups, carbohydrates and amino acids with respect to the other fractions. Nevertheless, the aromatic structure of A and B fractions seems to be more complex. The δ 13C values which indicated the presence of urea traces in the lowest MS fractions (B and C + D) may be due to the purification process.

Synthesis of higher alcohols from syngas over alkali promoted MoS 2 catalysts supported on multi-walled carbon nanotubes

An extensive study of higher alcohol synthesis from synthesis gas using potassium (K) promoted molybdenum sulfide supported on multi-wall carbon nanotubes (MWCNT) catalysts is reported. Up to 20 wt.% of Mo and 9 wt.% of K are added to the MWCNT by incipient wetness impregnation method. The catalysts are extensively characterized by different methods and the activity and selectivity of the catalysts are assessed in a fixed-bed micro-reactor. Increasing the amount of K from 3 to 9 wt.% increased K–Mo–O interactions, decreased the Mo particle sizes from 20.6 to 12.2 nm and increased the percentage dispersion from 20.2% to 30.9%. Most of the metal particles (∼80%) were homogeneously distributed inside the tubes and the rest on the outer surface of the MWCNT. Temperature programmed reduction (TPR) tests showed that increasing the amount of Mo increased the first and second TPR peak temperatures from 516 and 765 to 530 and 835 °C, respectively. However, addition of K decreased the peak temperatures from 534 and 825 to 519 and 787 °C, respectively. DRIFT spectroscopy of absorbed CO was used to study the nature of active species in the sulfided form of catalysts. Addition of K increased the formation of alcohols and suppressed the formation of hydrocarbons. Catalyst 15 wt.% Mo and 9 wt.% K supported on MWCNT showed the highest yield (0.11 g of total alcohol/g catalyst/h) and selectivity (25.6%) towards alcohols. The optimum conditions for producing the higher alcohols from synthesis gas (mole ratio of H 2 and CO is equal to 2) using gas hourly space velocity (GHSV) of 3.6 m 3 (STP)/h/kg of catalyst are determined to be 320 °C and 9.65 MPa (1400 psig).

Dynamic Characterization of the Intermediates for Low-Temperature PROX Reaction of CO in H2—Oxidation of CO with OH via HCOO Intermediate

The preferential oxidation (PROX) reaction of CO (CO + H2 + 1/2O2 → CO2) on a FeOx/Pt/TiO2 catalyst (∼140 wt % FeOx on 1 wt % Pt/TiO2) was studied at 60 °C by using in situ DRIFT spectroscopy. The PROX reaction of CO occurs via a HCOO intermediate and its oxidation with OH instead of oxygen, which is different from ordinary oxidation of CO with O2 (CO + 1/2O2 → CO2). The mechanism is as follows: (i) CO(a) + OH− → HCOO + e, (ii) O + e + H+ → OH, and (iii) HCOO + OH → CO2 + H2O, and step (iii) is the rate-determining step. Providing HCOO intermediates by a reaction of CO(a) with the OH− anion, step (i), was deduced by combining an electroconductive PROX catalyst (Pt/CNT(carbon nanotube)) with a hydrogen fuel cell. The oxidation of CO enhanced by H2 and H2O and the hydrogen isotope effect by H2/D2 and H2O/D2O on the FeOx/Pt/TiO2 catalyst are well explained by this mechanism.

Stability and maturity of a green waste and biowaste compost assessed on the basis of a molecular study using spectroscopy, thermal analysis, thermodesorption and thermochemolysis

The organic matter (OM) of a green waste and bio waste compost was characterised over 8 months and the observed evolution was correlated with physico-chemical parameters (temperature, pH, carbon content, C/N ratio). Thermochemolysis and thermodesorption were used to monitor bacterial activity (stability) whereas diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) and thermodifferential analysis (TDA) permitted to determine the degree of OM humification (maturity). DRIFT spectroscopy and TDA provide two indicators of maturity since, with these two techniques, the signals associated with the biodegradable organic matter decrease relatively to the signals associated with refractory organic matter. This increase in R TG and R IR ratios between aromatic to aliphatic signals constitutes a proof for OM complexification. It correlates with humic acids/fulvic acids ratio known to be a maturity index. Pyrolysates are mainly constituted of lignin moieties, terpenoids, nitrogen containing compounds, carbohydrates (furanosic moiety), mono- and diacids (as methyl esters), and methoxyesters. The R branched/linear ratio between branched to linear acids traduces the evolution of the bacterial activity during composting. Moreover the R di/mono ratio between aliphatic mono to diacids correlates with the latter showing that diacids can occur from the biological oxidation of monoacids. These two ratios determined by thermochemolysis are useful to monitor the stability of compost. VOC, observed by thermodesorption are mainly constituted of terpenes, light acids, aldehydes and ketone. An unexpected result was obtained since the amount of phytol increases relatively to the isoprenoid ketone considered to originate from the latter.

Chemistry and Microphysics of Atmospheric Aerosol Surfaces: Laboratory Techniques and Applications

Abstract A number of current techniques are presented by which the chemistry of interaction of selected gas phase species with atmospheric surfaces as well as the microphysical behaviour of such surfaces can be investigated. The techniques discussed include (i) the coated wall flow tube reactor, (ii) the Knudsen-cell / DRIFT spectroscopy, (iii) the surface aerosol microscopy and (iv) the molecular beam scattering technique. In each of these methods specific and robust information is deduced on the kinetics and thermodynamics of gas adsorption and reaction on surfaces. Specific examples include the adsorption of acetone on ice surfaces, the adsorption and reaction of SO2 on iron oxides, the hygroscopic and phase behaviour of binary and ternary salt solution droplets (ammonium sulphate and ammonium sulphate / dicarboxylic acids solutions) as well as on the dynamics of inelastic collisions of noble gases on super-cooled sulphuric acid surfaces. In addition we also show how quantum chemistry can be utilized to assist in interpreting absorption energies on structurally different ice surfaces. Whilst each example represents different aspects of heterogenous atmospheric interactions, they jointly represent significant progress in laboratory investigations of multi-phase atmospheric chemistry with substantial potential for application to other systems and/or problems.

Kinetics, equilibrium and mechanism of Cd 2+ removal from aqueous solution by mungbean husk

Mungbean husk ( mbh), an agrowaste material, was investigated as a new sorbent for the removal of Cd 2+ from aqueous solution. The maximum removal of Cd 2+ was found to be 35.41 mg g −1 at pH 5.0, 500 mg l −1 initial Cd 2+ concentration and 5 g l −1 sorbent dosage. Sorption kinetics and equilibria followed pseudo-second order and Langmuir isotherm equations. The mechanism of Cd 2+ adsorption on mbh was investigated by DRIFT spectroscopy, SEM–EDX analysis, and by monitoring the release of alkali and alkaline earth metal cations (Ca 2+, Mg 2+, K + and Na +) during the uptake of Cd 2+. DRIFT spectra of mbh showed the presence of amino, carboxyl, carbonyl and hydroxyl as the major functional groups involved in the sorption of Cd 2+. The sum of Ca 2+, Mg 2+, Na + and K + released from mbh with the quantitatively equivalent uptake of Cd 2+ indicated that the main mechanism of Cd 2+ adsorption was ion exchange. EDX analysis data supported the hypothesis of the involvement of ion exchange, as alkali and alkaline earth metal cations were noted to disappear in EDX spectrum of mbh after the uptake of Cd 2+. No significant loss in Cd 2+ sorption capacity of regenerated mbh was noted during reuse for five successive sorption–desorption cycles.

Novel supported catalysts for ethylene polymerization based on aluminohydride-zirconocene complexes

Ethylene polymerization using catalysts derived from activation of zirconocene aluminohydride complexes, supported on silica, pretreated with methylaluminoxane (MAO), is described. The novel catalyst compositions were compared to those using conventional zirconocene dichloride complexes and characterized by SEM/EDX and DRIFT spectroscopy. Supported catalysts were prepared which featured various surface Al:Zr ratios. When using excess MAO as both activator and scavenger, the catalysts containing the most Zr per g of support gave rise to the most active formulations; the high activities in the presence of excess MAO are due, in part, to catalyst leaching prior to and/or during polymerization. When tri-isobutylaluminum (TIBAL) was used as scavenger, the supported catalysts that featured a higher surface Al:Zr ratio had higher activity than those prepared at the lower Al:Zr ratios. The activity of the aluminohydride complexes was significantly higher than that of the corresponding dichloride complexes, when activated by MAO while the in the presence of TIBAL, there was little difference in performance between the two catalyst precursors.

Effect of anodic alumina pore diameter variation on template-initiated synthesis of carbon nanotube catalyst supports

Multi-walled carbon nanotubes (MWCNTs) are a potential alternative to commonly used heterogeneous catalyst supports due to their high surface area, structural integrity, and controllable dimensional characteristics. Synthesis of MWCNTs with specific pore diameters can be achieved by chemical vapor deposition (CVD) of a carbon source onto an anodic aluminum oxide (AAO) template. AAO films consist of pore channels in a uniform hexagonal arrangement that run parallel to the surface of the film. These films are created by the passivation of an aluminum anode within an electrolysis cell consisting of certain weak acid electrolytes. A two-step anodization method has been developed to produce these templates. Changing the concentration of the oxalic acid electrolyte and the electrical potential of the electrolysis cell altered the structural characteristics of these AAO films, specifically the diameter of their pore channels. The AAO characteristics were examined by SEM analysis. Controlling the pore diameter of these templates enabled the pore diameter of MWCNTs synthesized by CVD to be controlled as well. After considering their thermal and structural stability, the produced MWCNTs were characterized by SEM, TEM, TGA–DTA, BET N2 adsorption analysis, and DRIFT spectroscopy. Anodizing conditions of 0.40M oxalic acid concentration and 40.0V maximum anodizing potential were found to produce AAO films that resulted in MWCNTs with optimum surface characteristics for a catalyst support application. These MWCNTs with optimum pore diameters were synthesized for the purpose of being used as a support for NiMoS hydrotreating catalyst. This optimum grade of MWCNTs was found to produce the highest HDS and HDN activities when applied in the packed-bed processing of coker light gas oil.

How Gold Deposition Affects Anatase Performance in the Photo-catalytic Oxidation of Cyclohexane

Gold deposition on Hombikat UV100 was found to negatively affect the activity of this Anatase catalyst in selective photo-oxidation of cyclohexane. By ammonia TPD and DRIFT spectroscopy it was determined that the Au deposition procedure leads to a significant decrease in OH-group density (mol m−2 BET) on Hombikat, suggesting that the amount of surface OH-groups, rather than the presence or absence of Au, is determining the catalytic performance. The importance of surface OH-groups was demonstrated by comparing the performance of Hombikat (with and without Au deposition) to surface propoxylated TiO2, synthesized by a sol–gel method from titanium (IV) isopropoxide. The effect of the deposition recipe of noble metals on the surface composition of TiO2 should thus be taken into account in evaluating and explaining photocatalytic performance of TiO2 modified by noble metals (Au), in particular in non-aqueous phase reactions.

低温in-situ DRIFT分光法による高圧硫化NiMo触媒の表面構造解析

低温in-situ DRIFT分光法による高圧硫化NiMo触媒の表面構造解析