Synthesis of cyclic carbonate from vinyl cyclohexene oxide and CO2 using ionic liquids as catalysts

Synthesis of cyclic carbonate from 4-vinyl-1-cyclohexene-1,2-epoxide (VCHO) and carbon dioxide was investigated without using any solvent in the presence of ionic liquid as a catalyst. Ionic liquids based on 1-alkylmethylimidazolium salts of different alkyl groups (ethyl, butyl, hexyl, octyl) and different anions (Cl⁻, BF₄⁻, PF₆⁻) were used as catalysts. The conversion of VCHO was affected by the structure of the imidazolium salt ionic liquids; the ones with the cations of bulkier alkyl chain length and with more nucleophilic anion showed better reactivity. Reaction temperature, carbon dioxide pressure, and zinc halide cocatalyst enhanced the addition of CO₂ to VCHO. Semi-batch operation with continuous supply of carbon dioxide showed higher VCHO conversion than batch operation did.     

The effect of reaction conditions on the oxidation of veratryl alcohol catalyzed by cobalt salen-complexes

Cobalt salen-type [salen=N,N′-bis(salicylidene)ethylenediamine] complexes 1–6 were studied as catalysts for dioxygen activation in the oxidation of veratryl alcohol in basic aqueous conditions. The complexes Co(salen) (1), Co(CH₃salen) (2) [CH₃salen=N,N′-bis(methylsalicylidene)ethylenediamine], Co(4OHsalen) (3) [4OHsalen=N,N′-bis(4-hydroxosalicylidene)ethylenediamine], Co(sulfosalen) (4) [sulfosalen=N,N′-bis(5-sulfonatosalicylidene)ethylenediamine], Co(acacen) (5) [acacen=N,N′-bis(acetylacetone)ethylenediamine) and Co(N-Me-salpr) (6) [N-Me-salpr=bis(salicylideniminato-3-propyl)methylamine] were chosen to examine the influence of ligand structure on the catalytic activity. The effect of reaction conditions on the oxidation of veratryl alcohol was studied by varying temperature, pH, time or the nature and amount of the axial base needed to enhance the activity of complexes 1–5. The catalytic behaviour of the studied complexes was shown to be very depended on the applied conditions and distinct differences could be observed among the complexes. In all reactions, veratraldehyde was the only product observed. The unsubstituted complex 1 was the most efficient catalyst in the studied system achieving turnover numbers of up to 28 at 80 °C and pH 12.5.     

In situ FTIR study on NO reduction by C3H6 over Pd-based catalysts

The reaction mechanism of the reduction of NO by propene over Pd-based catalysts was studied by FTIR spectroscopy. It was observed that the reaction between NO and propene most probably goes via isocyanate (2256–2230 cm⁻¹), nitrate (1310–1250 cm⁻¹) and acetate (1560 and 1460 cm⁻¹) intermediates formation. Other possible intermediates such as partially oxidized hydrocarbons, NO₂, and formates were also detected. The reaction between nitrates and acetates or carbonates reduced nitrates to N₂ and oxidized carbon compounds to CO₂. In situ DRIFT provides quick and rather easily elucidated data from adsorbed compounds and reaction intermediates on the catalyst surface. The activity experiments were carried out to find out the possible reaction mechanism and furthermore the kinetic equation for NO reduction by propene.     

In situ IR and pulse reaction studies on the active oxygen species over SrF2/Nd2O3 catalyst for oxidative coupling of methane

Pulse reaction method and in situ IR spectroscopy were used to characterize the active oxygen species for oxidative coupling of methane (OCM) over SrF₂/Nd₂O₃ catalyst. It was found that OCM activity of the catalyst was very low in the absence of gas phase oxygen, which indicated that lattice oxygen species contributed little to the yield of C₂ hydrocarbons. IR band of superoxide species (O₂⁻) was detected on the O₂-preadsorbed SrF₂/Nd₂O₃. The substitution of ¹⁸O₂ isotope for ¹⁶O₂ caused the IR band of O₂⁻ at 1128 cm⁻¹ to shift to lower wavenumbers (1094 and 1062 cm⁻¹), consistent with the assignment of the spectra to the O₂⁻ species. A good correlation between the rate of disappearance of surface O₂⁻ and the rate of formation of gas phase C₂H₄ was observed upon interaction of CH₄ with O₂-preadsorbed catalyst at 700 °C. The O₂⁻ species was also observed on the catalyst under working condition. These results suggest that O₂⁻ species is the active oxygen species for OCM reaction on SrF₂/Nd₂O₃ catalyst.     

Kinetic studies of CH4 oxidation over Pt–NiO/δ-Al2O3 in a fluidised bed reactor

The oxidation of CH₄ over Pt–NiO/δ-Al₂O₃ has been studied in a fluidised bed reactor as part of a major project on an autothermal (combined oxidation–steam reforming) system for CH₄ conversion. The kinetic data were collected between 773 and 893 K and 101 kPa total pressure using CH₄ and O₂ compositions of 10–35% and 8–30%, respectively. Rate–temperature data were also obtained over alumina-supported monometallic catalysts, Pt and NiO. The bimetallic Pt–NiO system has a lower activation energy (80.8 kJ mol⁻¹) than either Pt (86.45 kJ mol⁻¹) and NiO (103.73 kJ mol⁻¹). The superior performance of the bimetallic catalyst was attributed to chemical synergy. The reaction rate over the Pt–NiO catalyst increased monotonically with CH₄ partial pressure but was inhibited by O₂. At low partial pressures (<30 kPa), H₂O has a detrimental effect on CH₄ conversion, whilst above 30 kPa, the rate increased dramatically with water content.     

Alkali metal ions transfer across a water/1,2-dichloroethane interface facilitated by a novel monoaza-B15C5 derivative

In this paper, a novel monoaza-B15C5 derivative, N-(2-tosylamino)-isopentyl-monoaza-15-crown-5 (L), is used as an ionophore to facilitate alkali metal cations transfer across a water/1,2-dichloroethane (W/DCE) interface. Well-defined voltammetric behaviors are observed at the polarized W/DCE interfaces supported at micro- and nano-pipets except Cs⁺. The diffusion coefficient of this ionophore in the DCE phase is calculated to be equal to (3.3±0.2)×10⁻⁶ cm² s⁻¹. The experimental results indicate that a 1:1 (metal:ionophore) complex is formed at the interface with a TIC/TID mechanism. The selectivity of this ionophore towards alkali ions follows the sequence Na⁺>Li⁺>K⁺>Rb⁺>Cs⁺. The logarithm of the association constants (log β₁^o) of the LiL⁺, NaL⁺, KL⁺ and RbL⁺ complexes in the DCE phase are calculated to be 10.6, 11.6, 9.0 and 7.1, respectively. The kinetic parameters are determined by steady-state voltammograms using nanopipets. The standard rate constants (k⁰) for Li⁺, Na⁺, K⁺ and Rb⁺ transfers facilitated by L are 0.54±0.05, 0.63±0.09, 0.51±0.04 and 0.46±0.06 cm s⁻¹, respectively. The pH values of aqueous solution have little effect on the electrochemical behaviors of these facilitated processes. The results predicate that this new type of ionophore might be useful to fabricate electrochemical sensor of sodium ion.     

Catalytic oxidation of naphthalene using a Pt/Al2O3 catalyst

Polycylic aromatic hydrocarbons (PAHs) are listed as carcinogenic and mutagenic priority pollutants, belonging to the environmental endocrine disrupters. Most PAHs in the environment stem from the atmospheric deposition and diesel emission. Consequently, the elimination of PAHs in the off-gases is one of the priority and emerging challenges. Catalytic oxidation has been widely used in the destruction of organic compounds due to its high efficiency (or conversion of reactants), its economic benefits and good applicability.

This study investigates the application of the catalytic oxidation using Pt/γ-Al₂O₃ catalysts to decompose PAHs and taking naphthalene (the simplest and least toxic PAH) as a target compound. It studies the relationships between conversion, operating parameters and relevant factors such as treatment temperatures, catalyst sizes and space velocities. Also, a related reaction kinetic expression is proposed to provide a simplified expression of the relevant kinetic parameters.

The results indicate that the Pt/γ-Al₂O₃ catalyst used accelerates the reaction rate of the decomposition of naphthalene and decreases the reaction temperature. A high conversion (over 95%) can be achieved at a moderate reaction temperature of 480 K and space velocity below 35,000 h⁻¹. Non-catalytic (thermal) oxidation achieves the same conversion at a temperature beyond 1000 K. The results also indicate that Rideal–Eley mechanism and Arrhenius equation can be reasonably applied to describe the data by using the pseudo-first-order reaction kinetic equation with activation energy of 149.97 kJ/mol and frequency factor equal to 3.26 × 10¹⁷ s⁻¹.     

Modelling formation and growth of H2SO4-H2O aerosols: Uncertainty analysis and experimental evaluation

An aerosol dynamics model, AERO2, is presented, which describes the formation of H₂SO₄-H₂O aerosol in a smog chamber. The model is used to analyse how the uncertainties on four input parameters are propagated through an aerosol dynamics model. The input parameters are: the rate of the reaction between SO₂ and OH (k₁), the ratio between the nucleation rate used in AERO2 and that derived from classical nucleation theory (t_n), the H₂SO₄ mass accommodation coefficient () and a measure of the turbulence intensity in the reactor (k_e). Uncertainties for these parameters are taken from the literature. One of the results of the analysis is that AERO2 and aerosol dynamics models in general can only predict upper bounds for the total number (N_tot) and total volume (V_tot) concentrations of the particles. The uncertainties on N_tot and V_tot are mainly due to the uncertainties on k₁, and t_n. An uncertainty factor of 20–100 still remains when the uncertainty on k₁, is reduced to ±5%. Aerosol measurements from three smog chamber experiments have therefore been used, in an attempt to reduce the uncertainty on k₁ and t_n. Values for k₁ are obtained in the reduced range 7.8 × 10⁻¹³ to 1.0 × 10⁻¹² cm³ s⁻¹, which is within the range found in the literature. For t_n, values in the range 10⁴–10⁷ are obtained, which is close to the upper bound of the range in literature. These values for t_n are in marked contrast with a recent set of experiments on nucleation in H₂SO₄-H₂O mixtures, which suggests a value for t_n of at most 10⁻⁵.     

Time resolved impedance spectroscopy as a probe of electrochemical kinetics: The ferro/ferricyanide redox reaction in the presence of anion adsorption on thin film gold

In this work, we use the time resolved technique of Fourier transform electrochemical impedance spectroscopy (FT-EIS) for quantitative kinetic analyses of Faradaic and nonfardaic, as well as heterogeneous and adsorption reactions. As a model system, we investigate the Fe(CN)₆^3−/4− redox reaction on a thin film Au electrode in the presence of nonfaradaically adsorbing ClO₄⁻ or Cl⁻ in neutral electrolytes. The redox process indicates a predominantly Faradaic outer sphere reaction, with nearly negligible adsorption of reactants on Au. dc voltage dependent kinetic parameters for both the anion and redox reactions are obtained by FT-EIS in real time during cyclic voltammetry. Equilibrium values of reaction rate constants, adsorption resistances and pseudocapacitances for the redox couple are also obtained. The theoretical background and working principles of these measurements are discussed, and the experimental findings are compared with previously published data.     

A comparison on the catalytic activity of Zn1−xCoxFe2O4 (x = 0, 0.2, 0.5, 0.8 and 1.0)-type ferrospinels prepared via. a low temperature route for the alkylation of aniline and phenol using methanol as the alkylating agent

Depending on the variation of the Zn²⁺/Co²⁺ ratio in the Zn_1−xCo_xFe₂O₄ (x=0, 0.2, 0.5, 0.8 and 1.0)-type ferrospinels, the systems showed different activity trends for aniline and phenol methylation using methanol as the alkylating agent. An increase in Zn²⁺/Co²⁺ ratio increased the rate of N-monomethylation of aniline, whereas, a decrease in the ratio favored the rate of ortho methylation of phenol. An attempt has been made to interpret the observed trends based on the variation of surface acid–base properties of the catalyst surface with changes in the spinel composition. The efficiency of adsorption of aniline, phenol or methanol depends not only on the catalyst surface acid–base properties but also on the polarity of the adsorbing molecules. A controlled interplay of surface acid–base properties and polarity of the respective reacting molecules determines the efficiency of a particular reaction. In the case of aniline methylation, surface basicity plays a dominating role, whereas for phenol methylation surface acidity plays a dominating role.     

Catalytic decomposition of nitrous oxide over Ru-exchanged zeolites

We report that ultrastable faujasite-based ruthenium zeolites are highly active catalysts for N₂O decomposition at low temperature (120–200°C). The faujasite-based ruthenium catalysts showed activity for the decomposition of N₂O per Ru³⁺ cation equivalent to the ZSM-5 based ruthenium catalysts at much lower temperatures (TOF at 0.05 vol.-% N₂O: 5.132 × 10⁻⁴ s⁻¹ Ru⁻¹ of Ru-HNaUSY at 200°C versus 5.609 × 10⁻⁴ s⁻¹ Ru⁻¹ of Ru-NaZSM-5 at 300°C). The kinetics of decomposition of N₂O over a Ru-NaZSM-5 (Ru: 0.99 wt.-%), a Ru-HNaUSY (Ru: 1.45 wt.-%) and a Ru-free, Na-ZSM-5 catalyst were studied over the temperature range from 40 to 700°C using a temperature-programmed micro-reactor system. With partial pressures of N₂O and O₂ up to 0.5 vol.-% and 5 vol.-%, respectively, the decomposition rate data are represented by: −dN₂O/dt=itk(P_N2O) (P_O2)^−0.5 for Ru-HNaUSY, −dN₂O/dt=k(P_N2O) (P_O2)^−0.1 for Ru-NaZSM-5, and −dN₂O/dt=k(P_N2O)^−0.2 (P_O2)^−0.1 for Na-ZSM-5. Oxygen had a stronger inhibition effect on the Ru-HNaUSY catalyst than on Ru-NaZSM-5. The oxygen inhibition effect was more pronounced at low temperature than at high temperature. We propose that the negative effect of oxygen on the rate of N₂O decomposition over Ru-HNaUSY is stronger than Ru-NaZSM-5 because at the lower temperatures (<200°C) the desorption of oxygen is a rate-limiting step over the faujasite-based catalyst. The apparent activation energy for N₂O decomposition in the absence of oxygen is much lower on Ru-HNaUSY (E_a: 46 kJ mol⁻¹) than on Ru-NaZSM-5 (E_a: 220 kJ mol⁻¹).     

Characterisation of the adsorption sites of hydrogen on Pt/C fuel cell catalysts

A key component of a hydrogen fuel cell is a catalyst to dissociate dihydrogen to hydrogen atoms. In the present study, the adsorption of hydrogen on Pt/C fuel cell catalysts has been investigated by inelastic neutron scattering spectroscopy.

Monitoring a clean Pt(50%)/C catalyst with low energy neutron spectroscopy, after exposure to dihydrogen at 20 K, as it was heated to room temperature, showed three distinct temperature regimes: (i) a decrease in intensity from 10 to 60 K, (ii) a rise to a maximum between 60 and 120 K and then (iii) a slow fall-off towards room temperature. We assign the three regions as: (i) desorption of physisorbed dihydrogen, (ii) dissociation of dihydrogen to give an adsorbed layer and (iii) damping of the response by an increasing Debye–Waller factor.

The vibrational INS spectra of a series of Pt/C catalysts prepared under varying conditions were similar indicating that the same types of site are common to all the catalysts, although the relative proportions of each site are sample dependent. Features at 520, 950 and part of the intensity at 1300 cm⁻¹ are assigned to hydrogen on (1 1 1) faces, in good agreement with single crystal data. The mode at 640 cm⁻¹ is assigned as the doubly degenerate asymmetric stretch of Pt(1 0 0) faces with the symmetric stretch near 550 cm⁻¹.

We assign the bending mode of the on-top site to the feature at 470 cm⁻¹. The Pt–H stretch mode was observed at 2079 cm⁻¹. This is a significant result: this is the first time that hydrogen on the on-top sites has been observed on nanosized platinum particles supported on high surface area carbon black. The width of the INS peak is surprisingly large and may give additional information on the type and relative proportions of the crystallographic faces present on the catalyst particles.     

Effect of pH, inorganic ions, organic matter and H2O2 on E. coli K12 photocatalytic inactivation by TiO2: Implications in solar water disinfection

The effect of different chemical parameters on photocatalytic inactivation of E. coli K12 is discussed. Illumination was produced by a solar lamp and suspended TiO₂ P-25 Degussa was used as catalyst. Modifications of initial pH between 4.0 and 9.0 do not affect the inactivation rate in the absence or presence of the catalyst. Addition of H₂O₂ affects positively the E. coli inactivation rate of both photolytic (only light) and photocatalytic (light plus TiO₂) disinfection processes. Addition of some inorganic ions (0.2 mmol/l) like HCO₃⁻, HPO₄²⁻, Cl⁻, NO₃⁻ and SO₄²⁻ to the suspension affects the sensitivity of bacteria to sunlight in the presence and in absence of TiO₂. Addition of HCO₃⁻ and HPO₄²⁻ resulted in a meaningful decrease in photocatalytic bactericidal effect while it was noted a weak influence of Cl⁻, SO₄²⁻ and NO₃⁻. The effect of counter ion (Na⁺ and K⁺) is not negligible and can modify the photocatalytic process as the anions. Bacteria inactivation was affected even at low concentrations (0.2 mmol/l) of SO₄²⁻ and HCO₃⁻, but the same concentration does not affect the resorcinol photodegradation, suggesting that disinfection is more sensitive to the presence of natural anions than photocatalytic degradation of organic compounds. The presence of organic substances naturally present in water like dihydroxybenzenes isomers shows a negative effect on photocatalytic disinfection. The effect of a mixture of chemical substances on photocatalytic disinfection was also studied by adding to the bacterial suspension nutrient broth, phosphate buffer and tap water.     

Oxidative conversion of methane to syngas over NiO/MgO solid solution supported on low surface area catalyst carrier

Influence of time-on-stream (0.5–15 h), CH₄/O₂ ratio in feed (1.8–8.0), space velocity (6000–510,000 cm³ g⁻¹ h⁻¹), catalyst particle size (22–70 mesh), and catalyst dilution by inert solid particles (diluent/catalyst weight ratio=4) on the performance at different temperatures (600–900°C) of the NiO/MgO solid solution deposited on SA-5205 [which is a low surface area macroporous silica-alumina catalyst carrier] in the oxidative conversion of methane to syngas (a mixture of CO and H₂) has been investigated. The dependence of conversion and selectivity on the space velocity is strongly influenced by the temperature. Both the conversion and selectivity for H₂ and CO are decreased markedly by increasing the CH₄/O₂ ratio in the feed. The catalyst dilution resulted in a small but significant decrease in both the conversion and selectivity for H₂ and CO. The increase in the catalyst particle size had also a small but significant effect on both the conversion and selectivity in the oxidative conversion process. Both the heat and mass transfer processes seem to play significant roles in the oxidative conversion of methane to syngas at a very low contact time or very high space velocity (5.1×10⁵ cm³ g⁻¹ h⁻¹).     

Synthesis of methanol and isobutanol from syngas over ZrO2-based catalysts

The effects of reaction conditions on the synthesis of isobutanol and methanol from syngas over Zr---K and Zr---Mn---K catalysts have been investigated, with the reactions carried out at pressures between 8 and 16 MPa, temperatures between 380 and 440 °C, and gas hourly space velocity (GHSV) between 3 000 and 8 000 h⁻¹. It was found that the Zr---K catalyst exhibited the highest activity and selectivity at 420 °C, 10.0 MPa, and 5 000 h⁻¹, and that the Mn-promoted catalyst increased the yield of isobutanol with the corresponding optimum temperature being 400 °C. Moreover, the higher pressure and GHSV favored isobutanol synthesis. At 16. 0 MPa, 400 °C, 5 000 h⁻¹, the space time yield of isobutanol was about 21.5 ml per ml cat. h⁻¹, and selectivity reached 98% over the Zr---Mn---K catalyst.     

Fe/Fe cycling promoted by Ta3N5 under visible irradiation in Fenton degradation of organic pollutants

Ta₃N₅ was synthesized by nitridation of Ta₂O₅ under NH₃ flow at 700 °C. The catalyst was pure Ta₃N₅ according to X-ray diffraction (XRD), and was about 5 nm in size with a BET specific surface area 52.8 m²/g. When Ta₃N₅ was added to Fe³⁺/H₂O₂ solution (known as Fenton-like system), most Fe³⁺ were adsorbed on the Ta₃N₅ surface and could not react with H₂O₂ in the dark, which is different from the general Fenton reaction. Under visible light irradiation, adsorbed Fe³⁺ ions were reduced to Fe²⁺ rapidly and Fe²⁺ were reoxidized by H₂O₂ on the Ta₃N₅ surface, thus a fast Fe³⁺/Fe²⁺ cycling was established. Kinetics and ESR measurements supported this mechanism. The Ta₃N₅/Fe³⁺/H₂O₂ system could efficiently decompose H₂O₂ to generate hydroxyl radicals driven by visible light, which could accelerate significantly the degradation of organic molecules such as N,N-dimethylaniline (DMA), and 2,4-dichlorophenol (DCP). A mechanism was proposed for iron cycling on the basis of experimental results.     

CoMo/MgO–Al2O3 supported catalysts: An alternative approach to prepare HDS catalysts

Three different supports were prepared with distinct magnesia–alumina ratio x = MgO/(MgO + Al₂O₃) = 0.01, 0.1 and 0.5. Synthesized supports were impregnated with Co and Mo salts by the incipient wetness method along with 1,2-cyclohexanediamine-N,N,N′,N′-tetraacetic acid (CyDTA) as chelating agent. Catalysts were characterized by BET surface area, Raman spectroscopy, SEM-EDX and HRTEM (STEM) spectroscopy techniques. The catalysts were evaluated for the thiophene hydrodesulfurization reaction and its activity results are discussed in terms of using chelating agent during the preparation of catalyst. A comparison of the activity between uncalcined and calcined catalysts was made and a higher activity was obtained with calcined MgO–Al₂O₃ supported catalysts. Two different MgO containing calcined catalysts were tested at micro-plant with industrial feedstocks of heavy Maya crude oil. The effect of support composition was observed for hydrodesulfurization (HDS), hydrodemetallization (HDM), hydrodeasphaltenization (HDAs) and hydrodenitrogenation (HDN) reactions, which were reported at temperature of 380 °C, pressure of 7 MPa and space-velocity of 1.0 h⁻¹ during 204 h of time-on-stream (TOS).     

Additive effects of trialkylaluminum on propene polymerization with (t-BuNSiMe2Flu)TiMe2-based catalysts

Propene polymerization was conducted by [η³:η¹-tert-butyl(dimethylfluorenylsilyl)amido]dimethyltitanium combined with B(C₆F₅)₃ or methylaluminoxane (MAO) as a cocatalyst in the presence or absence of various trialkylaluminums: Me₃Al, Et₃Al, ⁱBu₃Al (triisobutylaluminum) and Oct₃Al (trioctylaluminum). In the case of living polymerization with B(C₆F₅)₃ at −50°C, addition of Oct₃Al and Et₃Al increased the propagation rate. Et₃Al also acted as a chain transfer reagent and selectively gave Al-terminated polymers, while Oct₃Al induced chain transfer reaction only in high concentration. Little polymer was obtained in the presence of Me₃Al or ⁱBu₃Al. When MAO was used as a cocatalyst, polymerization did not proceed at −50°C. The MAO system, however, showed high activity at 40°C and selectively gave low molecular weight polymers terminated with Al–C bonds. Contrary to the low temperature polymerization with B(C₆F₅)₃ at −50°C, the polymer yield was enhanced by the addition of Me₃Al and ⁱBu₃Al, while the molecular weight was reduced by Me₃Al and enlarged by ⁱBu₃Al. On the other hand, Et₃Al and Oct₃Al significantly decreased both the polymer yield and the molecular weight under these conditions. It was found that additive effects of trialkylaluminums were strongly dependent on polymerization temperature as well as on the structure of the alkyl group.     

Solid electrolyte based on silicate matrix functionalised with tetraalkylammonium group solvated by organic solvent

Solid electrolyte composed of hybrid organic–inorganic silicate matrix functionalised with tetraalkylammonium group, solvated by viscous organic polar solvent (propylene carbonate (PC) or sulpholane (TMS)), was prepared by the sol–gel method under controlled drying conditions. Tetramethoxysilane (TMOS), N-trimethoxysilylpropyl-N,N,N-tributylammonium chloride (TMOSPTBACl) and organic solvent were principal sol components. Gel formed within 2 h and 2 days depending on substrate ratio and the solvent additive. The obtained material was transparent and it loosed about 15% of its mass during first 30 days of ageing. It was characterised by thermogravimetry (TGA), differential scanning calorimetry (DSC), NMR, FT-IR spectroscopy, small angle X-ray scattering (SAXS), and impedance spectroscopy. The transport of redox active molecules was studied by electrochemical methods. The porosity of samples dried in supercritical CO₂ was also estimated. The shape of TGA and DSC curve appeared to be similar to that of pure solvent. The IR spectra indicated the silicate network formation with some silanol groups left. The NMR spectrum of the solution used to wash crushed sample indicated that all organic substrate is embedded in silicate matrix. The magnitude of electrical conductivity was close to 10⁻⁴ to 10⁻⁵ S cm⁻¹, i.e. least more than one order of magnitude larger than that of TMOS based silicate matrix modified with a pure solvent. This conductivity is high enough for electrochemical experiments. Both conductivity and diffusion coefficient of redox probe-ferrocene (Fc) depended on time elapsed after gelation. Their most substantial decrease was observed during first 10 days after gelation and it correlated with mass loss.     

Isobutene hydration over Amberlyst-15 in a slurry reactor

The synthesis of tertiary butyl alcohol (TBA) via isobutene (iB) hydration was studied over Amberlyst-15 sulfonic acid catalyst particles using pure water and aqueous TBA solutions in a bubbling slurry reactor. Preliminary studies to investigate mass transfer effects showed that pore diffusion was present for catalyst particles greater than 165 μm in diameter. Therefore, intrinsic kinetic measurements were made using 90.5 μm catalyst particles and a catalyst loading of 10 kg m⁻³. The kinetic measurements revealed that iB hydration is a pseudo-first-order reaction with an activation energy of 69 kJ mol⁻¹. Isobutene hydration experiments using TBA concentrations in water revealed a hindering effect of TBA, which indicates that separation of TBA formed by iB hydration in three-phase reactors using catalytic distillation is promising from a process design perspective.