Conversion of 4-Methylanisole Catalyzed by Pt/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and by Pt/SiO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>: Reaction Networks and Evidence of Oxygen Removal

Abstract  

The conversion of 4-methylanisole, a prototypical bio-oil compound, was catalyzed by Pt/Al₂O₃, Pt/SiO₂-Al₂O₃, or HY zeolite at 573 K and atmospheric pressure. More than a dozen products were formed with each catalyst, the most abundant being 4-methylphenol, 2,4-dimethylphenol, and 2,4,6-trimethylphenol; toluene was also a major product when the catalyst was supported platinum with H₂ as a co-reactant. 4-Methylphenol was the only methylphenol isomer formed in significant yields, which indicates that migration of the methyl group on the aromatic ring is not significant under the selected reaction conditions. The data determine approximate reaction networks including reactions forming 4-methylphenol, 2,4-dimethylphenol, and toluene as primary products. The kinetically significant reaction classes were transalkylation, observed with all three catalysts, and hydrogenolysis (including hydrodeoxygenation) and hydrogenation, observed only with the platinum-containing catalysts operating in the presence of H₂. Data such as those reported here provide a starting point for predicting the conversion of whole bio-oils for removal of oxygen and upgrading of fuel properties.     

Short-range and long-range aggregation of particles in the γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> sol: I. Investigation of the aggregate stability of the negatively charged γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> sol

The electrical surface properties and aggregate stability of the negatively charged γ-Al₂O₃ (alundum) sol at pH 10.2 have been investigated over a wide range of KCl concentrations. The experimental data on the sol stability have been compared with the results of the calculations performed in the framework of the extended Derjaguin-Landau-Verwey-Overbeek theory. The parameters of the long-range structural forces for γ-Al₂O₃ particles have been evaluated.     

Short-range and long-range aggregation of particles in the γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> sol: II. Photometric and ultramicroscopic investigation of the aggregate stability of the positively charged γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> sol

The aggregate stability of the positively charged γ-Al₂O₃ (alundum) sol has been investigated using photometry and flow ultramicroscopy over a wide range of KCl concentrations. The data on the sol stability have been compared with the results of the calculations in the framework of the extended Derjaguin-Landau-Verwey-Overbeek theory. The parameters of the long-range structural forces for γ-Al₂O₃ particles have been evaluated. The role of the far potential minimum in the sol stability has been discussed.     

Enhancement of the Activities of γ-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts for Methane-SCR of NO by Treatment with NH<Subscript>3</Subscript>

Abstract  

The precursor particles for γ-Ga₂O₃–Al₂O₃ solid solutions were prepared by the coprecipitation method from aqueous solutions of Ga(NO₃)₃ and Al(NO₃)₃ with (NH₄)₂CO₃ as a precipitant. The γ-Ga₂O₃–Al₂O₃ solid solutions were obtained by calcination of the precursor at 700 °C. In this paper, the performance of the catalysts treated with NH₃ was investigated for the selective catalytic reduction (SCR) of NO with methane as a reducing agent, and it was found that γ-Ga₂O₃–Al₂O₃ catalysts treated with NH₃ and subsequently annealed in air showed higher activities than the γ-Ga₂O₃–Al₂O₃ catalysts without NH₃ treatment. NH₃ treatment of the catalyst caused partial rearrangement of Ga³⁺ and Al³⁺ ions and increased the population of tetrahedral Ga³⁺ ions in the defective spinel structure.     

Change of the thermal behavior of 55Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> ⋅ 45B<Subscript>2</Subscript>O<Subscript>3</Subscript> glass at annealing close to the vitrification temperature

The characteristic properties of relaxation processes for 55Bi₂O₃ ? 45B₂O₃ glass were described. The pattern of changes of the vitrification temperature (T _g ) is found to be quasi-periodic; the value of the endothermic effect near T _g (ΔC’ _p ) and the difference between the softening point and the vitrification temperature (T _m –T _g ) were determined. The temperature-time parameters of the transition from quasi-periodic to the continuous change of the properties were determined and an explanation of such behavior of the system was offered.     

Preparation of Biodiesel by Transesterification of Rapeseed Oil with Methanol Using Solid Base Catalyst Calcined K<Subscript>2</Subscript>CO<Subscript>3</Subscript>/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

We report here the preparation of biodiesel by transesterification of rapeseed oil with methanol using calcined K₂CO₃/γ-Al₂O₃ as a solid base catalyst. The prepared catalysts were characterized using SEM, IR and BET, and their catalytic activities were evaluated. The reaction conditions were optimized, and in particular, the conversion can be as high as 98.62% under the optimal reaction conditions. In addition, the effect of the presence of water in the reaction system on the catalytic activity was also studied.     

Role of CeO<Subscript>2</Subscript> in Rh/α-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts for CO<Subscript>2</Subscript> Reforming of Methane

Abstract  

The Rh/α-Al₂O₃ catalyst was modified by CeO₂ in order to improve the thermal stability and the carbon deposition resistance during the CO₂ reforming of methane The carbon formation was determined by TPO, TEM and Raman spectroscopy. Characterization results showed that the incorporation of Ce in the support inhibits the carbon deposition, increasing the useful life and the stability of the Rh base catalysts.     

Hydroisomerization of Benzene-Containing Gasoline Fraction on Pt/B<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Pt/WO<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts

The effect of the hydroisomerization conditions of the benzene-containing fraction of catalytic reforming gasoline on the yield and composition of products is studied on Pt/B₂O₃–Al₂O₃ and Pt/WO₃–Al₂O₃ catalysts. These catalysts allow benzene to be completely removed from the raw material. At the same time, the greatest yields of liquid products are obtained with minimal losses of the octane number at 2 MPa, a mass feedstock hourly space velocity (MFHSV) of 2 h^?1, and 325°C: 96.3 and 95.4 wt % on Pt/B₂O₃–Al₂O₃ and Pt/WO₃–Al₂O₃ catalysts, respectively. The activity of the catalysts is maintained for 100 h during their operation.     

Electrochromism in composite WO<Subscript>3</Subscript>–Nb<Subscript>2</Subscript>O<Subscript>5</Subscript> thin films synthesized by spray pyrolysis technique

Composite WO₃–Nb₂O₅ thin films were deposited on the glass and fluorine-doped tin oxide (FTO)-coated glass substrates using simple and inexpensive spray pyrolysis technique. The process parameters, like nozzle-to-substrate distance, spray rate, concentration of sprayed solution, etc., were optimized to good quality films. The films were characterized for the structural, morphological, optical, and electrochromic properties. Structural and morphological characterizations of the films were carried out using scanning electron microscopy and X-ray diffraction techniques. Electrochemical properties of the Composite WO₃–Nb2O₅ thin films were further studied using cyclic-voltammetry, chronoamperometry, chronocoulometry, and electrochemical Impedance spectroscopy.     

Synthesis of high surface area γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> as an efficient catalyst support for dehydrogenation of n-dodecane

In this work mesoporous nanocrystalline γ-Al₂O₃ has been synthesized by a three step (hydrolysis, condensation and hydrothermal treatment) sol–gel procedure in nitric acid medium with cationic surfactant (hexadecyltrimethyl ammonium bromide) as template. The prepared sample was employed as a carrier for the n-dodecane dehydrogenation catalyst. The synthesized samples were characterized by X-ray diffraction (XRD), N₂ adsorption (BET), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric (TG) and temperature programmed reduction (TPR) techniques. The nitrogen adsorption analysis showed that the samples possessed mesoporous structure with high specific surface areas larger than 370 m² g⁻¹ and pore volumes larger than 1.5 cm³ g⁻¹. The prepared samples also showed a high thermal stability up to 750 °C which is important for carrier of heterogeneous catalysts. The results of catalyst testing in the dehydrogenation reaction of n-dodecane confirmed that the synthesized support has a good potential to function as a carrier for n-dodecane dehydrogenation catalysts.     

Photon interaction parameters for some ZnO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

Some photon interaction parameters such as mass attenuation coefficient, effective atomic number, half value layer, mean free path and electron density for 15ZnO–(17.5–x)Al₂O₃–xFe₂O₃–67.5P₂O₅ glass system (x = 0, 7.5, 12.5, 17.5) and 15ZnO–(25–x)Al₂O₃–xFe₂O₃–60P₂O₅ glass system (x = 0, 25) have been investigated in the photon energy range of 1 keV to 100 GeV. It has been observed that all the photon interaction parameters for the selected glass systems vary with the photon energy. Among the selected glass systems, the sample 15ZnO–25Fe₂O₃–60P₂O₅ glass system shows maximum values for mass attenuation coefficients, effective atomic numbers, electron densities and minimum values for mean free path and half value layer in the entire energy grid.     

Investigating active centers of industrial catalysts for the oxidative chlorination of ethylene on a γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> surface

Selecting the best catalyst for large-scale industrial processes of the oxychlorination of ethylene (OCE) is a practical task of great importance. In such processes, even a slight reduction in selectivity results in considerable losses of raw materials. The enhancement of selectivity requires knowledge of the structure of the catalysts’ surfaces and the mechanism of the process of oxidative chlorination of ethylene into 1,2-dichloroethane (1,2-DCE). The structure of active sites of copper chloride catalysts on the surface of alumina was studied by physicochemical methods of IR spectroscopy and DTA. The structure was described for the active sites of catalysts for the oxidative chlorination of ethylene into (1,2-DCE) of two types, CuCl₂ and CuCl on γ-Al₂O₃: H1 (Harshow, United States) and OXYMAX-B (MEDC-B) (Sǜd-Chemie Catalysts, Germany). It was ascertained that complex compounds with [CuCl₄]⁻² and [CuCl₂]⁻¹ are formed upon interaction between the active phase of the catalyst (copper chlorides CuCl₂ or CuCl), and the surface groups of the support γ-Al₂O₃ (≡Al-OH) (this observation does not fall into the known theory of their structure). In accordance with the results from our study, a method was elaborated for synthesizing a catalyst with the optimum properties for OCE, and a pilot setup for the detailed investigation of this process was built. The possibility of cutting ethylene losses in half during deep oxidation and eliminating the formation of side products by a factor of 1.5–2 was demonstrated by the industrial production of 1,2-DCE and vinyl chloride at OOO Karpatnaftokhim in Kalush. The method for producing 1,2-DCE is protected by a Ukranian patent.     

Hydrogenation of CO on supported cobalt γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst in fixed bed and slurry bubble column reactors

Fischer-Tropsch synthesis for the production of C₅+ hydrocarbons from syngas was carried out in a tubular fixed bed reactor (TFBR) and in a slurry bubble column reactor (SBCR). The Co-based catalysts for FTS were prepared by the conventional wet-impregnation of γ-Al₂O₃. Effects of operating conditions such as GHSV (1,000–4,000 ml/g·hr), reaction temperature (220–250°C) and pressure (0.5–3.0MPa) on the CO conversion and product selectivity of Co/γ-Al₂O₃ catalyst were examined in the TFBR and SBCR. The C₅+ selectivity and olefin selectivity in an SBCR were found to be higher than that in a TFBR, whereas C₂–C₄ selectivity showed a reverse trend. The CO conversion and product distribution in an SBCR were less sensitive than that in a TFBR with variations of reaction conditions.     

Pd/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts on cellular supports for VOC vapor neutralization

The results from investigating the influence of temperature, concentration, and flow rate on the catalytic oxidation of vapors of volatile organic compounds (VOCs) in the presence of Pd/γ-Al₂O₃ catalyst on cellular supports are presented. The activity of Pd/γ-Al₂O₃ catalysts on ceramic and metal monolith supports with a cellular structure during the catalytic neutralization of VOC (ethanol, ethyl acetate) vapors under laboratory conditions was determined, and the most stable catalyst for the preliminary study of a large batch was chosen. A pilot unit was created to test a large batch of cellular monolith catalyst in neutralizing VOC vapors under conditions of flexographic production. It was established that a high rate of conversion (> 99 %) was achieved for VOC concentrations of 0.5 g/m³ at space velocities of up to ∼10⁴ h⁻¹, and for VOC concentrations of 5.0 g/m³ at space velocities of up to ∼5 × 10⁵ h⁻¹. The change in the activity of the catalysts on metal (nickel alloyed by aluminum) and ceramic cellular supports in service was investigated. After 300–500 min of operation, virtually complete deactivation of catalyst on a metal support was observed, accompanied by the formation of nickel oxide and acetate. Pilot unit tests with catalyst on cellular supports having a volume of 14.5 l in neutralizing the ventilation exhausts of flexographic production confirmed the possibility of more than 90% conversion at VOC concentrations of ∼0.1 g/m³ and more than 97% at VOC concentrations of over 1 g/m³. A consistently high conversion of VOC was observed during a 100 h test of the pilot unit. A system for recovering the heat released during VOC oxidation lowers the operating costs of the pilot unit.