CO2 reforming of methane combined with steam reforming or partial oxidation of methane to syngas over NdCoO3 perovskite-type mixed metal-oxide catalyst

CO₂ reforming with simultaneous steam reforming or partial oxidation of methane to syngas over NdCoO₃ perovskite-type mixed metal oxide catalyst (prereduced by H₂) at different process conditions has been investigated. In the simultaneous CO₂ and steam reforming, the conversion of methane and H₂O and also the H₂/CO product ratio are strongly influenced by the CO₂/H₂O feed-ratio. In the simultaneous CO₂ reforming and partial oxidation of methane, the conversion of methane and CO₂, H₂ selectivity and the net heat of reaction are strongly influenced by the process parameters (viz. temperature, space velocity and relative concentration of O₂ in the feed). In both cases, no carbon deposition on the catalyst was observed. The reduced NdCoO₃ perovskite-type mixed-oxide catalyst (Co dispersed on Nd₂O₃) is a highly promising catalyst for carbon-free CO₂ reforming combined with steam reforming or partial oxidation of methane to syngas.     

Si nanotubes and nanospheres with two-dimensional polycrystalline walls

We report on the characteristics of a new class of Si-based nanotubes and spherical nanoparticles synthesized by the dc-arc plasma method in a mixture of argon and hydrogen. These two nanostructures share common properties: they are hollow and possess very thin, highly polycrystalline and mainly oxidized walls. In particular, we get several hints indicating that their walls could constitute only one single Si oxidized layer. Moreover, we find that only the less oxidized nanotubes exhibit locally atomic ordered, snakeskin-like areas which possess a hexagonal arrangement which can be interpreted either as an sp(2) or sp(3) hybridized Si or Si-H layer. Their ability to not react with oxygen seems to suggest the presence of sp(2) configuration or the formation of silicon-hydrogen bonding.     

Direct formation of H2O2 from H2 and O2 and decomposition/hydrogenation of H2O2 in aqueous acidic reaction medium over halide-containing Pd/SiO2 catalytic system

Formation of H₂O₂ from H₂ and O₂ and decomposition/hydrogenation of H₂O₂ have been studied in aqueous acidic medium over Pd/SiO₂ catalyst in presence of different halide ions (viz. F⁻, Cl⁻ and Br⁻). The halide ions were introduced in the catalytic system via incorporating them in the catalyst or by adding into the reaction medium. The nature of the halide ions present in the catalytic system showed profound influence on the H₂O₂ formation selectivity in the H₂ to H₂O₂ oxidation over the catalyst. The H₂O₂ destruction via catalytic decomposition and by hydrogenation (in presence of hydrogen) was also found to be strongly dependent upon the nature of the halide ions present in the catalytic system. Among the different halides, Br⁻ was found to selectivity promote the conversion of H₂ to H₂O₂ by significantly reducing the H₂O₂ decomposition and hydrogenation over the catalyst. The other halides, on the other hand, showed a negative influence on the H₂O₂ formation by promoting the H₂ combustion to water and/or by increasing the rate of decomposition/hydrogenation of H₂O₂ over the catalyst. An optimum concentration of Br⁻ ions in the reaction medium or in the catalyst was found to be crucial for obtaining the higher H₂O₂ yield in the direct synthesis.     

Energy‐based predictive algorithm for semi‐active tuned mass dampers

There are various control strategies proposed and implemented for the protection of structures against different types of dynamic excitations. Currently, semi‐active control devices are very popular due to their adaptability and low power requirement. In this paper, a novel energy‐based predictive (EBP) algorithm is proposed, and its effectiveness is studied when applied to semi‐active tuned mass damper (SATMD). The mechanical energy of the primary structure is taken as the key parameter to be used by the algorithm to predict a suitable value of the manipulated variable, the damping of the tuned mass damper (TMD). The choice of the damping is made such that the damping used at a time interval leads to the least possible mechanical energy of the primary structure. The efficacy of the proposed control algorithm is studied by employing the EBP algorithm on single‐story and multistory structures equipped with the SATMD. The performance of the proposed algorithm when applied to the SATMD is also compared with that with the passive TMD for similar parameters. The results of the study show that the implementation of the EBP algorithm leads to significantly reduced dynamic response as compared with the passive TMD. Furthermore, numerical studies are conducted to gain insight into the effect of various parameters such as the mass ratio, the TMD damping ratio, and the flexibility of the structure.     

Cracking During Lateral Drying of Alumina Suspensions

The onset of cracking during drying of alumina suspensions cast onto a substrate has been studied experimentally. It is shown that the capillary pressure would impose a compressive stress on the particle array and cannot itself cause cracking. Based on experimental observations, it is proposed that the driving force for cracking arises from a misfit strain that occurs when repulsive layers between the particles collapse completely, after the particles have adhered to the substrate. This predicts that cracking should occur while the space between the particles is still filled with liquid, which is consistent with observations using laser speckle interferometry.     

Supported Nano-Gold Catalysts for Epoxidation of Styrene and Oxidation of Benzyl Alcohol to Benzaldehyde

Nano-gold particles supported on different alkaline earth oxides (viz. MgO, CaO, BaO and SrO), Gr. IIIa metal oxides (viz. Al₂O_3, Ga₂O_3, In₂O₃ and Tl₂O₃), transition metal oxides (viz. TiO_2, Cr₂O_3, MnO_2, Fe₂O_3, CoO_x, NiO, CuO, ZnO, Y₂O₃ and ZrO₂), rare earth metal oxides (viz. La₂O_3, Ce₂O_3, Nd₂O_3, Sm₂O_3, Eu₂O_3, Tb₂O_3, Er₂O₃ and Yb₂O₃) and U₃O₈ [all prepared by depositing gold on corresponding metal oxide support by deposition precipitation (DP) and/or homogeneous deposition precipitation (HDP) method] were evaluated for their catalytic performance in the liquid phase epoxidation of styrene by tert-butyl hydroperoxide (TBHP) to styrene oxide and also in the solvent-free benzyl alcohol-to-benzaldehyde oxidation (by molecular oxygen or TBHP) reactions. For the epoxidation, the catalytic performance (styrene oxide yield) of the most promising nano-gold catalysts prepared by the HDP method was in the following order: Au/MgO > Au/Tl₂O₃ > Au/Yb₂O₃ > Au/Tb₂O₃ > Au/CaO (or TiO₂). However, for the oxidation of benzyl alcohol to benzaldehyde by molecular oxygen, the order of choice for the most promising catalysts (based on benzaldehyde yield) was Au/U₃O₈ > Au/Al₂O₃ > Au/ZrO₂ > Au/MgO. Whereas, when TBHP was used as an oxidizing agent for the benzyl alcohol oxidation, the order of choice for the most promising catalysts was Au/U₃O₈ > Au/MgO > Au/TiO₂ > Au/ZrO₂ > Au/Al₂O₃. The catalytic performance of a particular supported nano-gold catalyst was thus found to depend on the reaction catalysed by them. Moreover, it is strongly influenced by a number of catalyst parameters, such as the metal oxide support, the method of gold depositon on the support, the gold loading and also on the catalyst calcination temperature. Nano-gold particles-support interactions seem to play an important role in controlling the deposition of gold (amount of gold deposited and size and morphology of gold particles), formation of different surface gold species (Au⁰, Au¹⁺ and Au³⁺) and electronic properties of gold particles and, consequently, control the catalytic performance (both the activity and selectivity) of the supported nano-gold catalysts in the reactions. The nano-gold catalysts prepared by the HDP method showed much better catalytic performance than those prepared by the DP, coprecipitation or impregnation method; in general, the HDP method provided supported gold catalysts with much higher gold loading and/or smaller size gold particles than that achieved by the DP and other methods.     

Alkylation of benzene by benzyl chloride over H-ZSM-5 zeolite with its framework Al completely or partially substituted by Fe or Ga

Liquid-phase benzylation of benzene by benzyl chloride to diphenylmethane over H-ZSM-5, H-gallosilicate(MFI), H-galloaluminosilicate(MFI), H-ferrosilicate(MFI) and H-ferroaluminosilicate(MFI) zeolites at 80°C has been investigated. A complete or partial substitution of Al in H-ZSM-5 zeolite by Fe or Ga results in a drastic increase in the catalytic activity of the zeolite in the benzylation process. The redox function of the zeolite is relatively more important than its acid function in the benzylation process.     

Excellent Field Emission Properties of Short Conical Carbon Nanotubes Prepared by Microwave Plasma Enhanced CVD Process

Randomly oriented short and low density conical carbon nanotubes (CNTs) were prepared on Si substrates by tubular microwave plasma enhanced chemical vapor deposition process at relatively low temperature (350–550 °C) by judiciously controlling the microwave power and growth time in C₂H₂ + NH₃ gas composition and Fe catalyst. Both length as well as density of the CNTs increased with increasing microwave power. CNTs consisted of regular conical compartments stacked in such a way that their outer diameter remained constant. Majority of the nanotubes had a sharp conical tip (5–20 nm) while its other side was either open or had a cone/pear-shaped catalyst particle. The CNTs were highly crystalline and had many open edges on the outer surface, particularly near the joints of the two compartments. These films showed excellent field emission characteristics. The best emission was observed for a medium density film with the lowest turn-on and threshold fields of 1.0 and 2.10 V/μm, respectively. It is suggested that not only CNT tip but open edges on the body also act as active emission sites in the randomly oriented geometry of such periodic structures.     

Combustion synthesis of PbO from lead carboxylate precursors relevant to developing a new method for recovering components from spent lead–acid batteries

BACKGROUND: In the conventional recycling process, lead battery pastes are recovered as metallic lead by using an energy intensive decomposition and reduction process. Decomposition of PbSO₄ requires the use of relatively high temperature and causes environmental pollution, i.e. emission of SO₂ and lead particulates. A new process for treating the pastes at low temperature has been developed. RESULTS: Three major lead compounds are individually reacted with an aqueous solution of citric acid in order to leach and to crystallize lead citrate precursors, which are then subjected to calcination at relatively low temperatures to recover the lead directly as PbO the most common active material for preparing pastes for a new battery. Characterization of the citrate precursors have been carried out using DSC, XRD, and SEM. The combustion products were characterized by XRD and SEM. CONCLUSION: Lead(II) oxides along with a small amount of lead metal are the combustion products, which can be produced at a relatively low temperature of 350 °C. Resulting morphologies show that combustion products are in the 100–200 nm size range, providing high‐surface‐area PbO for making new battery paste materials. The work is aimed to develop a sustainable process for recovering lead from spent lead battery paste. Copyright © 2012 Society of Chemical Industry     

Optimisation of CGO suspensions for inkjet-printed SOFC electrolytes

A detailed procedure for the preparation of gadolinium doped (10 mol%) cerium (IV) oxide (CGO) suspension for inkjet printing is described in this paper. The optimisation of inkjet printing parameters for the deposition of solid oxide fuel cell electrolytes was also performed using a custom-built drop visualisation system. Additionally, the uniformity of the deposited drop relics on porous substrates was evaluated. The ink used in this study was an evaporative type comprising a solvent mixture of terpineol and methanol, ethyl cellulose and CGO powder. Successful printing of regular drops was achieved after printing optimisation. It has been demonstrated that inkjet printing is a promising technique for high quality membrane fabrication for applications including solid oxide fuel cells. The ink formulation and optimisation procedure would also be applicable for other ceramic ink development.