NH3 Temperature-programmed Desorption Techniques Research Articles

ZnO nanostructures: comparative synthetic and characterisation studies

Tuneful behaviours of nano sized materials have been considered as challenge among researchers to explore the possibility of engaging in diverse applications. In particular, the zinc oxide (ZnO) nanostructured materials offer effective metallic behaviours to enhance the applications in the fuel oxidation, pigments, nonlinear optics and solar energy conversion. In the presented research, ZnO nanoparticles are successfully synthesised by (sol–gel and sol–gel and precipitation) techniques, respectively. The physicochemical behaviours of ZnO nanocrystals were inspected by x-ray diffraction, Fourier transform infrared, field-emission scanning electron microscopy, thermo-gravimetric analysis, N2 physisorption and NH3 temperature-programmed desorption techniques. The results revealed that Sol–gel method at lower pH produced smaller particle sizes with larger surface area and well-established morphology in shorter time at lower temperature conditions, in comparison to precipitation method with higher pH, time and temperature conditions, showed bigger particles with smaller surface area, respectively.

Biogasoline Production from Palm Oil: Optimization of Catalytic Cracking Parameters

Production of biogasoline from vegetable oil is one of the future directions in providing fuels for post-oil society. The catalytic cracking of refined bleached deodorized palm oil over a promoted ZSM-5 catalyst was carried out in a fixed-bed reactor. The fixed-bed catalytic process consists of three steps including reaction, stripping, and regeneration. The optimal catalytic cracking parameters were determined. The properties of catalyst were investigated by thermogravimetry analysis, differential scanning calorimetry, and N2 physisorption analysis while regeneration temperature effect toward catalyst acidity is being investigated by NH3 temperature programmed desorption technique. The apparent results show that the optimized reaction temperature was at 500 °C with a WHSV of 2.5 h−1 and the reaction time of 2 h. Meanwhile, the most effective regeneration temperature was found at 600 °C for three cycles of reaction–regeneration operation. During these cycles, 100% conversion of triglycerides and 48% selectivity to bio-naphtha can still be achieved.

The effect of different Ca precursors on the activity of manganese and cerium oxides supported on TiO2 for NO abatement

The different forms of Ca (CaCl2 and Ca(OH)2) poisoned manganese and cerium oxides supported on TiO2 catalysts were prepared by impregnation method and used for selective catalytic reduction (SCR) of NO with NH3. The Ca poisoning effects were investigated by many characterization methods including N2 adsorption/desorption, X-ray diffraction, X-ray photoelectron spectroscopy, H2-temperature programmed reduction and NH3-temperature programmed desorption techniques. The results showed that the addition of Ca led to greatly decrease of catalytic activity of catalysts and the catalytic activity was ranked in the order: CaCl2 poisoned catalyst < Ca(OH)2 poisoned catalyst < fresh catalyst, which indicated that the poisoning effect of different forms of Ca was different and the deactivation caused by CaCl2 was more serious. The characterization results demonstrated the addition of Ca greatly decreased the specific surface area of catalysts, the contents of surface active species (Mn4+ and Ce3+), the amounts of weak Bronsted acid sites and the low-temperature redox ability, especially for the CaCl2 poisoned catalyst, all of which led to the weaken of the catalytic activity of catalysts.

Preparation of γ-Al2O3 via Hydrothermal Synthesis Using ρ-Al2O3 as Raw Material for Propane Dehydrogenation

γ-Al2O3 was prepared by hydrothermal synthesis using ρ-Al2O3 and urea as raw materials. In this work, the effects of the molar ratio of CO(NH2)2/Al and reaction temperature were investigated, and a Pt–Sn–K/γ-Al2O3 catalyst was prepared. The ammonium aluminum carbonate hydroxide (AACH), γ-Al2O3, and Pt–Sn–K/γ-Al2O3 were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption–desorption, thermogravimetry–differential thermal analysis, and NH3 temperature-programmed desorption techniques. The reactivity of Pt–Sn–K/γ-Al2O3 for propane dehydrogenation was tested in a micro-fixed-bed reactor. The results show that γ-Al2O3 with a specific surface area of 358.1 m2/g and pore volume of 0.96 cm3/g was obtained when the molar ratio of CO(NH2)2/Al was 3:1 and the reaction temperature was 140 °C. The alumina obtained by calcination of AACH has a higher specific surface area and larger pore volume than the industrial pseudo-boehmite does. The catalyst prepared from AACH as precursor showed high selectivity and conversion, which can reach 96.1% and 37.6%, respectively, for propane dehydrogenation.

Diethyl Ether Production during Catalytic Dehydration of Ethanol over Ru- and Pt- modified H-beta Zeolite Catalysts.

In the present study, the catalytic dehydration of ethanol over H-beta zeolite (HBZ) catalyst with ruthenium (Ru-HBZ) and platinum (Pt-HBZ) modification was investigated. Upon the reaction temperature between 200 and 400°C, it revealed that ethanol conversion and ethylene selectivity increased with increasing temperature for both Ru and Pt modification. At lower temperature (200 to 250°C), diethyl ether (DEE) was the major product. It was found that Ru and Pt modification on HBZ catalyst can result in increased DEE yield at low reaction temperature due to increased ethanol conversion without a significant change in DEE selectivity. By comparing the DEE yield of all catalysts in this study, the Ru-HBZ catalyst apparently exhibited the highest DEE yield (ca. 47%) at 250°C. However, at temperature from 350 to 400°C, the effect of Ru and Pt was less pronounced on ethylene yield. With various characterization techniques, the effects of Ru and Pt modification on HBZ catalyst were elucidated. It revealed that Ru and Pt were present in the highly dispersed forms and well distributed in the catalyst granules. It appeared that the weak acid sites measured by NH3 temperature-programmed desorption technique also decreased with Ru and Pt promotion. Thus, the increased DEE yields with the Ru and Pt modification can be attributed to the presence of optimal weak acid sites leading to increased intrinsic activity of the catalysts. It can be concluded that the modification of Ru and Pt on HBZ catalyst can improve the DEE yields by ca. 10%.

Study on the Preparation and Catalytic Activities of SO4 2− Promoted Metal Oxide Solid Superacid Catalysts for Model Oil Desulfurization

A series of SO4 2− promoted metal oxide solid superacids: SO4 2−/ZrO2–WO3 (SZW), SO4 2−/ZrO2–MoO3 (SZM) and SO4 2−/ZrO2–Cr2O3 (SZC) were prepared by incorporating different metals into SO4 2−/ZrO2 (SZ). The above four catalysts were characterized by Fourier transformation infrared spectroscopy (FT-IR), X-ray diffraction and NH3-temperature programmed desorption techniques and scanning electron microscope. Then, they were respectively used as catalysts for oxidative desulfurization for model oil under the same mild conditions. The results exhibited that catalytic activities of SZW, SZM and SZC all increased to different degrees compared with SZ. Among them SZC performed best. Finally, the possible mechanism of this reaction was also presented.

Diatomite-entrapped hydrosulfate catalysts for the efficient nitration of toluene with nitric acid

Diatomite-entrapped hydrosulfate catalysts with the enhanced acidity were prepared by impregnation and 20 wt% KHSO4/diatomite was selected as a heterogeneous catalyst for the catalytic nitration of toluene. The characterization of the catalyst by X-ray diffraction, Scanning electron microscopy, Brunauer–Emmett–Teller, Fourier-transform infrared spectroscopy and NH3 temperature-programmed desorption technique presented that potassium sulfate could be properly dispersed on the surface of the diatomite, the analysis with back titration showed that the total acidity of the catalyst was 0.85 mmol/g, indicating an excellent catalytic activity for the nitration of toluene. The catalyst with outside surface processed by alkali improved the para-selectivity for the nitration of toluene besides the undiminished activity, due to the pore shape of the acidified diatomite to improve the para-selectivity of the nitration process. Under optimal conditions, the catalytic nitration of toluene obtains 88.21 % of total yield and 1.87 of para/ortho (p/o) ratio.

Fe‐Beta catalysts prepared by heating wet ion exchange and their catalytic performances on N2O catalytic decomposition and reduction

ABSTRACTA heating wet ion exchange method was successfully used to synthesize Fe‐beta catalysts by controlling preparation conditions. The iron loading of Fe‐beta catalysts increased from 0.88% to 16.56% with raising the ion exchange temperature from 20 to 90 °C. Their catalytic activities for N2O decomposition and N2O reduction by NH3 were evaluated. The activity results show that the catalyst prepared at 80 °C (Fe‐beta‐80 °C) could achieve complete N2O decomposition at 480 °C and N2O reduction by NH3 at 375 °C. The iron species of catalysts were further characterized by X‐ray diffraction, transmission electron microscopy (TEM), UV–vis, H2 temperature programmed reduction, and NH3 temperature programmed desorption techniques. The characterization results indicate that related high content of isolated Fe3+ ions and oligonuclear Fe3+xOy clusters existed in the Fe‐beta‐80 °C catalyst, which contributed to the high catalytic activity. Moreover, after the reaction of more than 100 h, Fe‐beta‐80 °C catalyst has no obvious deactivation under simulated emission conditions. The presence of O2 (5%) reduced N2O conversion only to a small extent, whereas NO (1000 ppm) promoted the N2O decomposition over Fe‐beta‐80 °C. © 2013 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Promoting effect of Ir on the catalytic property of Ru/ZnO catalysts for selective hydrogenation of crotonaldehyde

A series of ZnO supported Ru–Ir bimetal catalysts were prepared and tested for vapor-phase selective hydrogenation of crotonaldehyde. The addition of Ir could effectively promote the catalytic performance, especially the catalyst stability. A Ru–0.5Ir/ZnO catalyst showed the highest activity (a conversion of 63.3%) and selectivity to crotyl alcohol (94.4%) after 30h reaction. The enhanced stability was attributed to the modified electronic property of Ru by the formation of RuIr alloy as the X-ray photoelectron spectroscopy results showed charge transfer from Ru to Ir, as well as the weakened surface acidity in the Ru–Ir/ZnO catalyst as evidenced by NH3 temperature-programmed desorption technique. Besides, the deactivation of the catalysts was due to the strong chemisorption of CO on the metal surface via decarbonylation reaction and deposition of organic compounds on the catalyst surface, which was characterized by CO poisoning experiment, CO temperature-programmed desorption and temperature-programmed oxidation methods.

Effect of nonionic structure-directing agents on adsorption and structural properties of mesoporous alumina

Mesoporous aluminas (MAs) with tailored adsorption, framework, and surface basic–acidic properties were prepared using different structure-directing agents (SDAs) such as Brij®78, Pluronic F108, poly(ethylene oxide)–poly(butylene oxide)–poly(ethylene oxide) B50-6600 and Vorasurf™ 504 block copolymers, which so far were not explored for the synthesis of this important material viasolvent evaporation-induced self-assembly (EISA) strategy. Thermogravimetry, Fourier transform infrared spectroscopy, small-angle X-ray diffraction, nitrogen adsorption, transmission electron microscopy, and CO2 and NH3 temperature programmed desorption techniques were used to characterize the samples studied. Depending on the SDAs and aluminium precursors used in the EISA process, the BET surface area, pore volume and the average pore size of the MA samples were tailored in the range of 300–433 m2 g−1, 0.33–1.07 cm3 g−1, and 2.7–11.5 nm, respectively. Importantly, the use of F108 as a SDA and aluminium isopropoxide as an aluminium precursor gave a highly ordered MA with a large pore volume of 1.07 cm3 g−1 and enlarged mesopores centering at 11.5 nm, which are larger than those reported for the P123 and F127 Pluronic block copolymer-templated MA samples. However, the use of F108 as the SDA and AlCl3 as the aluminium precursor resulted in disordered MA with much smaller mesopores centering at 2.7 nm, enhancing the adsorption affinity towards CO2 (1261 μmol g−1) and NH3 (350 μmol g−1). This study shows that the EISA strategy does not require a stringent selection of SDA, and that the F108 block copolymer is an excellent SDA for the preparation of MA with a large pore volume and high adsorption capacity towards CO2, which exceeds substantially the value obtained for conventional alumina samples and for the previously reported ordered MA prepared in the presence of P123 and F127, which are commonly used as SDAs.

Complete oxidation of 2-propanol over gold-based catalysts supported on metal oxides

This paper concerns the preparation of metal oxide-supported gold catalysts and their application to 2-propanol abatement in order to lower the light off temperature. Catalytic oxidation of 2-propanol was investigated on Au/CeO2, Au/Fe2O3, Au/TiO2 and Au/Al2O3 catalysts prepared from the deposition–precipitation (DP) method. The catalysts are characterized by XRD (X-ray diffraction), BET (Brunner–Emmett–Teller), TEM (transmission electron microscopy), NH3-TPD (NH3-temperature programmed desorption), H2-TPR (H2-temperature programmed reduction), ICP-AES (inductively coupled plasma-atomic emission spectroscopy) and XPS (X-ray photoelectron spectroscopy) techniques. The catalytic activity of Au/metal oxide samples towards the deep oxidation of 2-propanol to CO2 and water has been found to be strongly dependent on the kind of supports, the amount of gold loading, the calcination temperature and the moisture content in the feed.