The active phase of NaCo/ZnO catalyst for ethanol steam reforming: EXAFS and in situ XANES studies

The NaCo/ZnO catalyst was prepared by a co-precipitation method and the active phase for the catalyst was studied. Extended X-ray absorption fine structure (EXAFS) studies were used to obtain structural parameters of the active phase of the catalyst. In situ X-ray absorption near edge structure (XANES) studies were also employed to better understand the phase transition of the catalyst in the course of H₂-temperature-programmed reduction followed by ethanol steam reforming. The XANES analysis confirmed that the oxidic precursor of Co₃O₄ phase was transformed to CoO followed by Co metal in the course of H₂-TPR, and the Co metal phase remained stable during the reaction. The EXAFS analysis for the fresh and spent catalyst samples revealed that the characteristic features corresponding to Co–Co distance of Co metallic phase were being developed during reaction, which demonstrated that Co phase is most likely the active phase of NaCo/ZnO catalyst for the ethanol steam reforming. The catalytic activity in ethanol steam reforming for hydrogen production over the oxidized and reduced catalyst samples was measured at 773 K and 1 atm in a fixed bed reactor using a model liquid feed containing 21 vol% ethanol in water. The prereduced NaCo/ZnO catalyst gave high ethanol conversion of 99% with product distributions of 73.0% H₂, 2.2% CO, 22.1% CO₂, and 2.7% CH₄, while the calcined oxidic one exhibited poor ethanol conversion below 44% at 773 K.     

A Traffic Accident Recording and Reporting Model at Intersections

In this paper, we suggested a vision-based traffic accident detection algorithm and developed a system for automatically detecting, recording, and reporting traffic accidents at intersections. A system with these properties would be beneficial in determining the cause of accidents and the features of an intersection that impact safety. This model first extracts the vehicles from the video image of the charge-couple-device camera, tracks the moving vehicles (MVs), and extracts features such as the variation rate of the velocity, position, area, and direction of MVs. The model then makes decisions on the traffic accident based on the extracted features. In a field test, the suggested model achieved a correct detection rate (CDR) of 50% and a detection rate of 60%. Considering that a sound-based accident detection system showed a CDR of 1% and a DR of 66.1%, our result is a remarkable achievement     

Factors influencing the formation of 2-hydroxy-6-naphthoic acid from carboxylation of naphthol

The synthesis of 2-hydroxy-6-naphthoic acid (2,6-HNA) from carboxylation of alkali-naphthoxide was studied with varying alkali cation types and reaction conditions such as reactant concentration, reaction time, temperature, and pressure. The product selectivity was strongly affected by the types of alkali cation, reaction time, and temperature, while the product yield was governed by reaction pressure. The maximum HNA yield, 28.6%, was achieved with 2,6-HNA selectivity of 81.6% at 6 atm of CO₂, 543 K, and 6 h of reaction. The addition of K₂CO₃ led to further increase in the productivity of 2,6-HNA via suppression of the decarboxylation of HNA.     

TPR and EXAFS Studies on Na-Promoted Co/ZnO Catalysts for Ethanol Steam Reforming

Na-promoted Co/ZnO catalysts were prepared and applied to ethanol steam reforming. TPR and EXAFS analysis demonstrated that Na promoter effectively enhanced the reducibility of Co phase on ZnO with better catalytic activity and selectivity towards H₂ than unpromoted Co/ZnO.     

Model for accurate speed measurement using double-loop detectors

Vehicle speed is an important parameter in measurements of road traffic. At present, double-loop detectors are generally used for vehicular speed measurement. However, these detectors incur errors caused by scanning time, spacing between double loops, irregular vehicle trajectories, and the presence of multiple vehicles in the detection zone. This paper suggests a new model that uses an error-filtering algorithm to improve the accuracy of speed measurements. In the field tests, all percent errors of the vehicular speeds measured by the proposed model were within the error tolerance limit (/spl plusmn/5%). Furthermore, the variance of percent errors was reduced. Therefore, it can be concluded that the proposed model significantly improves vehicle-speed-measuring accuracy.     

NOx Storage and Reduction Catalysts for Automotive Lean-Burn Engines: Effect of Parameters and Storage Materials on NOx Conversion

The effect of various parameters on the NO _x conversion over NO _x storage and reduction catalysts supported on alumina was investigated. The Pt/BaO/Al₂O₃ catalyst exhibited a higher NO _x reduction activity than the Pt/Al₂O₃ catalyst under the static and cycling conditions. The activity of Pt/BaO/Al₂O₃ catalyst was improved in the cycled feedstream. The Pt/SrO/Al₂O₃ was found to have as high activity as Pt/BaO/Al₂O₃ for NO _x reduction. In order to achieve effective reduction of NO _x , NO _x storage in the form of Me(NO₃)₂ (Me = Ba or Sr) is more favorable than other nitrates and the rich condition should be chosen in such a way that the sorption capacity can be fully regenerated at a fast rate and the inhibition effect by strongly adsorbed molecules derived from C₃H₆ and CO can be minimized.     

Formation mechanisms of Ni2P nanocrystals using XANES and EXAFS spectroscopy

Ni₂P nanocrystals have been synthesized by a ligand stabilization method with adopting nickel acetylacetonate (Ni(acac)₂) as a nickel precursor and trioctylphosphine (TOP) as a phosphorous precursor in the presence of trioctylphosphine oxide (TOPO) as a coordinating solvent. In order to better understand the formation of Ni₂P nanocrystals, various synthetic routes were employed with varying the mixing order of TOP or TOPO with Ni(acac)₂ in the complexation and nucleation steps, and the phosphidation temperatures of Ni-TOP solution in TOPO. In all cases the formation of Ni₂P nanocrystals having an average size in range of 5-11 nm was achieved, but with slightly larger particle distribution of ca. 11 nm being observed for the case where the TOP was injected after a nucleation of Ni-TOPO was formed. In particular, XAFS techniques of EXAXS and XANES which are effective to characterize either amorphous or crystalline materials were applied to examine the structural and electrical properties of the precursor, intermediate and final materials. This led to elucidate the role and the effect of TOP and TOPO on the formation of Ni₂P nanocrystals. It is concluded that the formation of Ni₂P nanocrystals proceeds through three consecutive steps of complexation, nucleation and phosphidation. In phosphidation, TOP works as a reducing agent on the Ni precursor as well as a phosphorous source through the cleavage of P-C bonds.     

Transalkylation of toluene and 1,2,4-trimethylbenzene over large pore zeolites

Large pore zeolites, H-beta, H-mordenite (H-MOR) and H-omega, were dealuminated by steam treatment followed by acid leaching and were applied for transalkylation of toluene and 1,2,4-trimethylbenzene. The acidic properties of catalysts were examined by using TPD of ammonia and in situ FT-IR spectroscopy in the OH stretching region as well as pyridine adsorbed catalysts. XRD, mid-infrared spectroscopy and and MAS-NMR techniques were employed to investigate the structural changes of zeolites during dealumination process. Among the parent zeolites, H-beta and H-MOR showed high activity for transalkylation. H-omega showed very low activity although its acidity turned out to be high compared to that of H-MOR or H-beta. Over dealuminated samples, the activity was in the order H-MOR>H-omega≈H-beta unlike over the parent zeolites. It was observed that a large number of Brønsted acid sites were present in small pores and cages in H-MOR and H-omega. After dealumination, the activity and stability were substantially improved for H-MOR and H-omega but decreased for H-beta. H-MOR and H-omega tended to have more open structure and some of occluded acid sites became exposed to the main channels of 12-MR by dealumination. Such structural changes are believed to compensate for the loss of total acid sites to bring about the enhanced activity and stability over H-MOR and H-omega. Dealuminated H-omega, however, was deactivated rather rapidly. Consequently, H-MOR could be considered as a good acid catalyst for transalkylation of toluene and 1,2,4-trimethylbenzene after treatment by steam followed by acid leaching.     

Hydrogen production from ethanol over Co/ZnO catalyst in a multi-layered reformer

A Co/ZnO catalyst was prepared by coprecipitation method, and was applied for ethanol steam reforming. The effect of reaction conditions on the ethanol steam reforming performance was studied in the temperature ranges from 400 °C to 600 °C and the space velocity ranges from 10,000 h⁻¹ to 120,000 h⁻¹ in a fixed bed reactor. The Co/ZnO showed high activity with an ethanol conversion of 97% and a H₂ concentration of 73% at a gas hourly space velocity of 40,000 h⁻¹ and a moderately low temperature of 450 °C. EXAFS analysis for fresh and spent samples confirms that Co phase maintains during reaction. The catalyst was then loaded into a multi-layered reformer of which the design concept allows for integrating endothermic steam reforming, exothermic combustion and evaporation in a reactor. The performance of the compact reformer demonstrated that the hydrogen production rate satisfy a PEMFC stack power level of 540 W suitable for portable power supplies.     

35-We polymer electrolyte membrane fuel cell system for notebook computer using a compact fuel processor

A polymer electrolyte membrane fuel cell (PEMFC) system is developed to power a notebook computer. The system consists of a compact methanol-reforming system with a CO preferential oxidation unit, a 16-cell PEMFC stack, and a control unit for the management of the system with a d.c.–d.c. converter. The compact fuel-processor system (260 cm³) generates about 1.2 L min⁻¹ of reformate, which corresponds to 35 We, with a low CO concentration (<30 ppm, typically 0 ppm), and is thus proven to be capable of being targetted at notebook computers.