High-quality, oriented and mesostructured organosilica monolith as a potential UV sensor

We synthesized high-quality and oriented periodic mesoporous organosilica (PMO) monoliths through a solvent evaporation process using a wide range of mole ratios of the components: 0.17–0.56 1,2-bis(triethoxysilyl)ethane (BTSE): 0.2 cetyltrimethylammonium chloride (CTACl): 0–1.8 × 10⁻³ HCl: 0–80 EtOH: 5–400 H₂O. X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images indicated that the mesoporous channels within the monolith samples were oriented parallel to the flat external surface of the PMO monolith and possessed a hexagonal symmetry lattice (p6mm). The PMO monolith synthesized from a reactant composition of 0.35 BTSE: 0.2 CTACl: 1.8 × 10⁻⁶ HCl: 10 EtOH: 10 H₂O had a pore diameter, pore volume, and surface area – obtained from an N₂ sorption isotherm – of 25.0 Å, 0.96 cm³ g⁻¹ and 1231 m² g⁻¹, respectively. After calcination at 280 °C for 2 h in N₂ flow, the PMO monolith retained monolith-shape and mesostructure. Pore diameter and surface area of the calcined PMO monolith sample were 19.8 Å, 0.53 cm³ g⁻¹ and 1368 m² g⁻¹, respectively. We performed ²⁹Si and ¹³C CP MAS NMR spectroscopy experiments to confirm the presence of Si–C bonding within the framework of the PMO monoliths. We investigated the thermal stability of the PMO monoliths through thermogravimetric analysis (TGA). In addition, rare-earth ions (Eu³⁺, Tb³⁺ and Tm³⁺) were doped into the monoliths. Optical properties of those Eu³⁺, Tb³⁺ and Tm³⁺-doped PMO monoliths were investigated by photoluminescence (PL) spectra to evaluate their potential applicability as UV sensors.     

On-stream modification of MFI zeolite membranes for enhancing hydrogen separation at high temperature

-Alumina-supported MFI zeolite membranes were modified by on-stream catalytic thermal cracking of methyldiethoxysilane (MDES) molecules inside the zeolitic channels during the separation of H₂/CO₂ gas mixture at 450 °C and atmospheric pressure. The MDES vapor was carried by the H₂/CO₂ feed gas and the effect of modification was monitored continuously through online analysis of the permeate stream. The modified membrane exhibited a significant increase in H₂ selectivity over CO₂ with a moderate decrease in H₂ permeance. At 450 °C, the modified MFI membrane obtained a H₂/CO₂ permselectivity of 17.5 with H₂ single gas permeance of 1.86 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ as compared to a permselectivity of 2.78 and permeance of 2.75 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ for the membrane before modification. The modified membrane also showed good performance and stability in separation of H₂/CO₂ gas mixture containing up to 28.4% water vapor at 450 °C and atmospheric pressure.     

Sorption kinetics of ammonia and ammonium ions on gel and macroporous sulphonic acid cation exchangers

Diffusion of ammonia and ammonium ions in sulphonic acid cation exchangers (gel Purolite SGC 100 × 10 MBH and macroporous Purolite C 160 MBH) from the solutions, representing the composition of “caustic condensate” (waste of nitrogen fertilizers production) is affected by pH of initial solution and structure of the matrix of cation exchanger. In gel matrix the effective intraparticle diffusivity (D_ef) depends greatly on the solution pH because of shrinkage in alkaline and swelling in acidic medium: on decreasing the initial concentration of ammonia from 0.214 to 0.003 and increasing that of ammonium nitrate from 0 to 0.214 mol l⁻¹ instead, the effect of ion exchange leads to a decrease in pH, resulting in swelling and increase in D_ef from 0.1 to 0.34 × 10⁻¹⁰ for gel Purolite SGC 100 × 10 MBH and variation of 0.18–0.11 × 10⁻¹⁰ m² s⁻¹ for macroporous Purolite C 160 MBH (resistant to shrinkage and swelling).

In Purolite C 160 MBH both macropore diffusivity (0.07–0.29 × 10⁻¹⁰ m² s⁻¹) and gel (solid phase) diffusivity (0.06–0.19 × 10⁻¹⁰ m² s⁻¹) are higher than micropore diffusivity (0.28–0.56 × 10⁻¹⁸ m² s⁻¹).

With respect to the effective intraparticle diffusivity, resistance to nitric acid, used for the regeneration, and high concentration of ammonium nitrate in eluate (up to 110 g l⁻¹), Purolite C 160 MBH has been installed for the conversion of ammonia and ammonium ions to ammonium nitrate reusable in the fertilizers production. This allows minimizing the economic loss and preventing the environmental contamination.     

Synthesis and proton conductivity of sulfonic acid functionalized zeolite BEA nanocrystals

The objective of this study is to prepare sulfonic acid functionalized zeolite BEA nanocrystals, and determine the bulk proton conductivity of this new material. Phenethyl functionalized zeolite BEA nanocrystals are synthesized using a mixture of fumed silica and phenethyltrimethoxysilane as silica sources. Contact of the phenethyl zeolite BEA nanocrystals with concentrated sulfuric acid removes the organic structure-directing agent (SDA) and simultaneously sulfonates the phenethyl moieties. Detailed characterizations of the zeolite BEA nanocrystals are performed using dynamic light scattering (DLS), Fourier transform Raman spectroscopy (FT-Raman), ²⁹Si cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy (²⁹Si CPMAS NMR), ¹³C CPMAS NMR, ¹H MAS NMR, thermogravimetric (TGA) analyses, transmission electron microscopy (TEM) and powder X-ray diffraction (XRD). Sulfonic acid functionalized zeolite BEA nanocrystals have proton conductivities in the range of 1.2 × 10⁻³–1.2 × 10⁻² S/cm compared to 1.5 × 10⁻⁴ S/cm for unfunctionalizated zeolite BEA.     

Poly-(3-methylthiophene)/carbon nanotubes hybrid composite-modified electrodes

The preparation of poly-(3-methylthiophene)—multi-walled carbon nanotubes hybrid composite electrodes is reported. The hybrid electrode shows a synergic effect of the electrocatalytic properties, and high active surface area of both the conducting polymer and carbon nanotubes, which gives rise to a remarkable improvement of oxidation of NADH with respect to polymer-modified electrodes, and CNTs-modified electrodes. SEM showed that carbon nanotubes served as nanosized backbone for P3MT electropolymerization. The amperometric NADH detection at +300 mV provided fast responses, a range of linearity between 5.0 × 10⁻⁷ and 2.0 × 10⁻⁵ mol l⁻¹, and a detection limit of 1.7 × 10⁻⁷ mol l⁻¹, which compares advantageously with those reported for other NADH CNT-based amperometric sensors. Furthermore, the direct electrochemistry of cytochrome c and FAD at the hybrid electrode is also checked.     

Selective permeation and separation of steam from water–methanol–hydrogen gas mixtures through mordenite membrane

Separation properties of a mordenite membrane for water–methanol–hydrogen mixtures were studied in the temperature range from 423 to 523 K under pressurized conditions. The mordenite membrane was prepared on the outer surface of a porous alumina tubular support by a secondary-growth method. It was found that water was selectively permeated through the membrane. The separation factor of water/hydrogen and water/methanol were 49–156 and 73–101, respectively. Even when only hydrogen was fed at 0.5 MPa, its permeance was as low as 10⁻⁹ mol m⁻² s⁻¹ Pa⁻¹ up to 493 K, possibly suggesting that water pre-adsorbed in the micropores of mordenite hindered the permeation of hydrogen. The hydrogen permeance dramatically increased to 6.5 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ at 503 K and reached to 1.4 × 10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹ at 523 K because of the formation of cracks in the membrane. However, the membrane was thermally stabilized in the presence of steam and/or methanol.     

Decolorization of organic dyes on Pilkington Activ™ photocatalytic glass

The air–solid photocatalytic degradation of organic dye films Acid Blue 9 (AB9) and Reactive Black 5 (RBk5) is studied on Pilkington Activ™ glass. The Activ™ glass comprises of a colorless TiO₂ layer deposited on clear glass. The Activ™ glass is characterized using atomic force microscopy (AFM) and X-ray diffraction (XRD). Using AFM, the TiO₂ average agglomerate particle size is 95 nm, with an apparent TiO₂ thickness of 12 nm. The XRD results indicate the anatase phase of TiO₂, with a calculated crystallite size of 18 nm.

Dyes AB9 and RBk5 are deposited in a liquid film and dried on the Activ™ glass to test for photodecolorization in air, using eight UVA blacklight-blue fluorescent lamps with an average UVA irradiance of 1.4 mW/cm². A novel horizontal coat method is used for dye deposition, minimizing the amount of solution used while forming a fairly uniform dye layer. About 35–75 monolayers of dye are placed on the Activ™ glass, with a covered area of 7–10 cm². Dye degradation is observed visually and via UV–vis spectroscopy.

The kinetics of photodecolorization satisfactorily fit a two-step series reaction model, indicating that the dye degrades to a single colored intermediate compound before reaching its final colorless product(s). Each reaction step follows a simple irreversible first-order reaction rate form. The average k₁ is 0.017 and 0.021 min⁻¹ for AB9 and RBk5, respectively, and the corresponding average k₂ is 2.0 × 10⁻³ and 1.5 × 10⁻³ min⁻¹. Variable light intensity experiments reveal a p = 0.44 ± 0.02 exponent dependency of initial decolorization rate on the UV irradiance. Solar experiments are conducted outdoors with an average temperature, water vapor density, and UVA irradiance of 30.8 °C, 6.4 g water/m³ dry air, and 1.5 mW/cm², respectively. For AB9, the average solar k₁ is 0.041 min⁻¹ and k₂ is 5.7 × 10⁻³ min⁻¹.     

Electrodeposition of cesium at mercury electrodes in the tri-1-butylmethylammonium bis((trifluoromethyl)sulfonyl)imide room-temperature ionic liquid

The electrochemistry of cesium was investigated at mercury electrodes in the tri-1-butylmethylammonium bis((trifluoromethyl)sulfonyl)imide (Bu₃MeN⁺Tf₂N⁻) room-temperature ionic liquid (RTIL) by using cyclic staircase voltammetry, rotating disk electrode voltammetry, and chronoamperometry. The reduction of cesium ions at mercury exhibits quasireversible behavior with k⁰ = 9.8 × 10⁻⁵ cm s⁻¹ and = 0.36. The diffusion coefficient of Cs⁺ in this RTIL was 1.04 × 10⁻⁸ cm² s⁻¹ at 303 K. Bulk deposition/stripping experiments conducted at a rotating mercury film electrode gave an average recovery of 97% of the electrodeposited Cs. The density, absolute viscosity, and equivalent conductance of Bu₃MeN⁺Tf₂N⁻ were measured over the range of temperatures from 298 to 353 K. A polynomial equation describing the temperature dependence of the density is presented. Both the viscosity and conductance exhibited the non-Arrhenius temperature dependence typical of glass-forming liquids. The ideal glass transition temperature and the activation energies for viscosity and conductance were obtained by fitting the Vogel–Tammann–Fulcher (VTF) equation to the experimental data for these transport properties.     

Effect of Pt on the water resistance of Co-zeolites upon the SCR of NOx with CH4

The objective of this work was to study the promotional effect of Pt on Co-zeolite (viz. mordenite, ferrierite, ZSM-5 and Y-zeolite) and Co/Al₂O₃ on the selective catalytic reduction (SCR) of NO_x with CH₄ under dry and wet reaction stream. After being reduced in H₂ at 350°C, the PtCo bimetallic zeolites showed higher NO to N₂ conversion and selectivity than the monometallic samples, as well as a combination of the latter samples such as mechanical mixtures or two-stage catalysts. After the same pretreatment, under wet reaction stream, the bimetallic samples were also more active. Among the other catalysts studied with 5% of water in the feed, (NO = CH₄ = 1000 ppm, O₂ = 2%), the NO conversion dropped to zero over Co_2.0Mor at 500°C and GHSV = 30,000 h⁻¹, whereas it is 20% in Pt_0.5Co_2.0Mor. In Pt/Co/Al₂O₃ the NO_x conversion dropped below 5% with only 2% of water under the same reaction conditions. The specific activity given as molecules of NO converted per total metal atom per second were 16.5 × 10⁻⁴ s⁻¹ for Pt_0.5Co_2.0Fer, 13 × 10⁻⁴ s⁻¹ for Pt_0.5Co_2.0Mor, 4.33 × 10⁻⁴ s⁻¹ for Pt_0.5Co_2.0ZSM-5 and 0.5 × 10⁻⁴ s⁻¹ for Pt/Co/Al₂O₃. The Y-zeolite-based samples were inactive in both mono and bimetallic samples. The species initially present in the solid were Pt° and Co°, together with Co²⁺ and Pt²⁺ at exchange positions. Co° seems not to participate as an active site in the SCR of NO_x. Those species remained after the reaction but some reorganization occurred. A synergetic effect among the different species that enhances both the NO to NO₂ reaction, the activation of CH₄ and also the ability of the catalyst to adsorb NO, could be responsible for the high activity and selectivity of the bimetallic zeolites.     

The measurement of gas diffusivity in porous materials by temporal analysis of products (TAP)

The pulsing of argon in a temporal analysis of products (TAP) reactor and reactor modeling of the response curves were used to measure the effective intraparticle diffusivities in porous materials. The diffusivity that can be measured is limited: (1) at the low end by intraparticle diffusion being too slow such that just a small fraction of the pulse gets into the pores to give an indistinguishable tail, which only measures that the diffusivity is smaller than an upper limit and (2) at the high end by intraparticle diffusion being too fast such that it gives a constant concentration in the pores, which only measures that the diffusivity is larger than a lower limit. The limits and range are slightly different for different particle and bed dimensions. A 9 mm long packed bed has a sensitive range of about 300-fold where there are discernible changes in the normalized pulse shape due to diffusivity changes. If small particles of about 50 μm are used, the range is from 1 × 10⁻¹⁰ to 3 × 10⁻⁸ m²/s, and if large particles of about 500 μm are used, the range is from 2 × 10⁻⁹to 5 × 10⁻⁷ m²/s.     

Nano-gold supported on TiO2 coated glass-fiber for removing toxic CO gas from air

A process for coating a layer of TiO₂ on the surface of glass fiber (Pyrex) was developed to support nano-gold on the fiber. The sol–gel method was utilized. The solution was composed of tetrapropyl titanate (TPT), isopropanol (i-PrOH), HCl and H₂O. The XRD pattern indicated that TiO₂ was in its anatase form after the coated fiber was calcined at 450 °C. In the preparation of nano-gold on the fibers (coated with TiO₂), deposition was performed in a pH-adjusted gold chloride solution. The catalytic activities of the resulting fibers were examined by the oxidation of CO in an air stream at room temperature. The gold containing fibers dried at room temperature contained less metallic gold and exhibited poorer CO oxidation activity than did those dried at 60 °C Moreover, the catalytic activities of the fibers depended on the gold concentration during deposition. Therefore, the gold fibers from the solution with gold concentrations of 2 × 10⁻⁴ M exhibited better CO oxidation activity than those from the solutions with concentrations of 1 × 10⁻³ and 0.7 × 10⁻⁴ M. TEM and A.A. analysis show that different concentrations of the gold solution were associated with different particle sizes and different gold loadings on the fibers, and therefore different catalytic activities of the fibers (per unit weight of fibers). 0.1 g of fibers prepared from the 2 × 10⁻⁴ M gold solution removed all CO from the air stream (containing 1% CO at a flow rate 110 cm³/min) at room temperature, approximately meeting the European Community EN403 (1993) standard for a qualified CO gas mask material.     

Kinetics of hydrogen oxidation reaction on Nafion-coated Pt/C electrodes under high overpotentials

The influences of the Nafion film thickness and Pt loading on the kinetics of the hydrogen oxidation reaction on Nafion-coated 20 wt% Pt/C electrodes immersed in 0.5 M H₂SO₄ were investigated using a rotating disk electrode configuration. The coating of a Nafion film (8 μm) had a negligible effect on the electrochemical surface area of an electrode. The kinetic parameters were estimated at an overpotential of 0.4 V; the values obtained were shown to vary with the method of data treatment. The diffusional resistance for H₂ in the Nafion film was negligible when the film was thinner than 0.2 μm. The permeability of H₂ in the Nafion film ranged from 2.4 × 10⁻⁵ to 4.8 × 10⁻⁵ mM cm²/s. The error analysis demonstrated that the apparent kinetic current estimated was resulted from experimental errors, instead of resulting from a chemical process as proposed by some previous investigators.     

Reduction of nitrite by sulfamic acid and sodium azide from aqueous solutions treated by gliding arc discharge

Nitrous and nitric acids form in aqueous solutions exposed to a gliding arc discharge burning in humid air. The anions interfere when the concentration of particular solutes such as pollutants must be determined. In particular they falsify the COD measurements and spectral investigations and thus the efficiency of the plasma treatment in pollutant abatement. The nitrite anions must be thus removed, which require specific reagents. The influence of parameters such as solution pH and [reducers]/[NO₂⁻] ratio on the reduction reaction was evaluated. The reduction of nitrite into N₂ either by sulfamic acid or sodium azide is a first-order pH-dependant reaction with regard to nitrite and reducers (k₁ = 2.93 × 10⁻¹ m³ kmol⁻¹ s⁻¹; k₂ = 6.21 × 10⁻¹ m³ kmol⁻¹ s⁻¹, respectively). Sodium azide is thus more reactive than sulfamic acid.     

Dilute solution properties of carboxymethylchitins in high ionic-strength solvent

The hydrodynamic characteristics in aqueous solution at ionic strength I=0.2  of carboxymethylchitins of different degrees of chemical substitution have been determined. Experimental values varied over the following ranges: the translational diffusion coefficient (at 25.0°C), 1.1<10⁷×D<2.9 cm² s⁻¹; the sedimentation coefficient, 2.4<s<5.0 S; the Gralen coefficient (sedimentation concentration-dependence parameter), 130<k_s<680 mL g⁻¹; the intrinsic viscosity, 130<[η]<550 mL g⁻¹. Combination of s with D using the Svedberg equation yielded ‘sedimentation–diffusion' molecular weights in the range 40 000<M<240 000 g mol⁻¹. The corresponding Mark–Houwink–Kuhn–Sakurada (MHKS) relationships between the molecular weight and s, D and [η] were: [η]=5.58×10⁻³ M^0.94; D=1.87×10⁻⁴ M^−0.60; s=4.10×10⁻¹⁵ M^0.39. The equilibrium rigidity and hydrodynamic diameter of the carboxymethylchitin polymer chain is also investigated on the basis of wormlike coil theory without excluded volume effects. The significance of the Gralen k_s values for these substances is discussed.     

Effect of different calcination environments on the vanadium phosphate catalysts for selective oxidation of propane and n-butane

Vanadium phosphate catalysts were synthesized via VOPO₄·2H₂O and were calcined in two different hydrocarbon reaction environments, i.e. n-butane/air and propane/air. Both catalysts are denoted VPDB and VPDP, respectively. Both catalysts exhibited a good crystalline with characteristic peaks of pyrophosphate phase. However, the peaks for VPDP are shown to be more prominent than those of VPDB. BET surface area showed that VPDB gave higher surface area (23 m² g⁻¹) compared to VPDP (18 m² g⁻¹). The average V valence state for VPDP is 4.08 and the higher V valence state for VPDB is 4.26 due to higher amount of V^V for VPDB. Furthermore 14.2% of V^III was found for VPDP but none for VPDB. SEM micrographs clearly revealed that the morphologies of both catalysts composed of plate-like crystallite that was arranged into the characteristic of rosette cluster. However, the catalyst calcined in n-butane/air environment (VPDB) resulted in an increment of the amount of plate-like crystal formed in the rosette rosebud agglomerates. TPR in H₂ profiles of both catalysts gave two reduction peaks corresponding to two kinetically different oxygen species which were associated with V^V and V^IV phases, respectively. VPDB removed larger amount of active oxygen species linked to V^IV phase which eventually caused a higher conversion rate in the selective oxidation of n-butane and propane to maleic anhydride and acrylic acid, respectively.     

Effects of oxygen concentration on the electrical properties of ZnO films

In this paper, electrical characteristics by various oxygen content in ZnO films were studied. To control the oxygen content of ZnO films, post-thermal annealing was performed in N₂ and air ambient, led to improve crystallinity and optical properties of ZnO films. The oxygen concentration was measured by Auger electron spectroscopy. The ZnO films having the deficiency of oxygen showed the electron concentrations between 10²¹ and mid 6 × 10¹⁷ cm⁻³ and resistivity at 10⁻³–10⁻¹ Ω cm. On the other hand, when the oxygen concentration of the ZnO films was up to the stoichiometry with Zn, the ZnO films showed low electron concentration at −10¹⁷ cm⁻³ and resistivity at 10 Ω cm.     

Variation of the aerosol charge neutralization coefficient in the entire particle size range

The rate at which the mean charge on aerosol particles relaxes to its steady-state value under bipolar charging is characterized by the neutralization rate constant, β (s⁻¹). It is an important parameter for fixing the nt product in charge neutralizers as well as in the theory of charging-induced diffusion. Here we compute the neutralization coefficient, β/n (where n is the mean ion density), as a function of particle size through the use of ion-particle combination coefficients provided by the recent theories. The results indicate that β/n decreases from a continuum limit value of 3.1 × 10⁻⁶ cm³ s⁻¹, to a free molecular limit value of 1.4 × 10⁻⁶ cm³ s⁻¹. The changeover occurs rapidly in the transitional regime (10–100 nm). This clearly indicates that the nt product required to attain steady state is higher for nano particles than for larger ones. The paper also presents the variations of the mean square variance of charge, the coefficients of charging-induced drift and diffusion, as a function of particle size.     

Kinetics and mechanism of low-temperature ozone decomposition by Co-ions adsorbed on silica

Kinetics and mechanism of low-temperature ozone ((5–50) × 10⁻³ mol/m³ in the gas–air mixture) decomposition by Co-catalysts supported on silica have been studied. Co-ions adsorbed on silica react with surface oxygen species, thus resulting in an active catalyst. Low concentrations of Co-ions form a monolayer on the surface. Their specific catalytic activity remained constant, but sharply decreased at higher concentrations due to a formation of polynuclear Co-complexes. Ozone decomposition may occur either as a stoichiometric or catalytic process, depending on the ozone and catalyst concentrations. The turnover number increases with ozone concentration reaching a saturation point. It also increases with Co-concentration in the beginning, but drops at a concentration >1 × 10⁻⁴ mol/g. The mechanism of the reaction is discussed.     

Voltammetric behavior study of folic acid at phosphomolybdic-polypyrrole film modified electrode

The electrochemical behavior of folic acid at the Keggin-type phosphomolybdate (PMo₁₂) doped polypyrrole (PPy) film modified glassy carbon electrode (PMo₁₂-PPy/GCE) was studied. PMo₁₂ doped PPy modified electrodes were achieved during the electrochemical preparation of the polymer films in aqueous solution. The redox behavior of the modified electrode was described by cyclic voltammetry. The electrochemical behavior of folic acid at PMo₁₂-PPy/GCE was studied by 0.5 order differential voltammetry. Numerous factors affecting the reduction peak currents of folic acid at PMo₁₂-PPy/GCE were optimized to maximize the sensitivity. The results showed that folic acid had high inhibitory activity toward the reduction of modified electrode in 0.01 M H₂SO₄. The reduction peak currents were directly proportional to the concentration of folic acid from 1.0 × 10⁻⁸ to 1 × 10⁻⁷ M with correlation coefficient of 0.9976, a detection limit of 1.0 × 10⁻¹⁰ M of folic acid was estimated. From the inhibitory effect of folic acid on PMo₁₂-PPy/GCE, the apparent formation constant of folic acid with the modified film was estimated. This modified electrode showed excellent sensitivity and stability for the determination of folic acid. The response mechanism of folic acid at PMo₁₂-PPy/GCE was discussed in detail.     

Decomposition of NO over Cu-AITS-1 zeolites

H-AITS-1 zeolite with Si/Ti = 50 and Si/Al = 50 was employed in preparing catalyst samples by ion-exchange and impregnation with a copper nitrate solution to obtain 0.24–1.15 wt.% and 1.5, 2 and 2.5 wt.% Cu loading, respectively. The catalytic properties for the NO decomposition were compared with that of Cu-ZSM-5 (Si/Al = 25 with 2 wt.% Cu loading) and similarity was found between the AITS-1 based samples and Cu-ZSM-5. Due to the higher acidity, the activity at 500°C per total copper atoms (an apparent turnover frequency, TOF) was significantly higher over Cu based AITS-1 samples being 2–3 × 10⁻³ s⁻¹ as compared to 1 × 10⁻³ s⁻¹ measured on Cu-ZSM-5. For the ion-exchanged Cu-AITS-1 there was an increase in TOF with increasing copper content, whereas on the impregnated samples a decrease in TOF was found. On all catalysts there was a maximum in the NO conversion at 500–550°C. The amount of NO per copper atom measured by temperature programmed desorption (TPD) was about the same as that on Cu-ZSM-5 and the features of the TPD were also similar. At the first contact of the catalyst at 500°C with the 2 vol% NO/Ar gas a transient N₂O formation and a considerable delay in the O₂ formation was observed. This could, however, be reproduced only on fresh catalyst, while all further transients showed different but reproducible features using the same sample.