Effect of the catalyst composition in the Ptx(Ru–Ir)1−x/C system on the electro-oxidation of methanol in acid media

The effect of variations in the composition for ternary catalysts of the type Pt_x(Ru–Ir)_1−x/C on the methanol oxidation reaction in acid media for x values of 0.25, 0.50 and 0.75 is reported. The catalysts were prepared by the sol–gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic absorption spectroscopy (AAS) and energy dispersive X-ray (EDX) analyses. The nanometric character (2.8–3.2 nm) of the sol–gel deposits was demonstrated by XRD and TEM while EDX and AAS analyses showed that the metallic ratio in the compounds was very near to the expected one. Cyclic voltammograms for methanol oxidation revealed that the reaction onset occur at less positive potentials in all the ternary catalysts tested here when compared to a Pt_0.75–Ru_0.25/C (E-Tek) commercial composite. Steady-state polarization experiments (Tafel plots) showed that the Pt_0.25(Ru–Ir)_0.75/C catalyst is the more active one for methanol oxidation as revealed by the shift of the reaction onset towards lower potentials. In addition, constant potential electrolyses suggest that the addition of Ru and Ir to Pt decreases the poisoning effect of the strongly adsorbed species generated during methanol oxidation. Consequently, the Pt_0.25(Ru–Ir)_0.75/C composite catalyst is a very promising one for practical applications.     

The PCDD/PCDF Dioxin Releases in the Climate of Environment of Jordan in the Period （2000-2008）

Many environment problems of the full using of several categories of processing include mining, heat generators, direct combustion of forest fires, cement production, power plant, transport, medical waste. Dioxin/furan releases from these categories are one of these environment problems. Possible lines of reducing the PCDD/ PCDF （Polychlorinated dibenzo-para-dioxins/Polychlorinated dibenzofurans） releases from these categories are eluci- dated. The contribution of this paper is present the identification and estimation of the latest figure of dioxin/furan releases in the climate of environment of Jordan in the period 2000-2008 from the following categories （cement, aluminum, ceramic, medical waste, power plant, land fill, ferrous and non- ferrous metals, uncontrolled combustion process （biomass burning, waste burning, accidental fires in house, transport）. These finding shows the sign of growth of estimated PCDD/PCDF releases from categories which did not calculated and followed after 2003. The result shows the highest PCDD/PCDF release from landfill fires （62.75 g TEQ/year）, medical waste （8.8264 g TEQ/year）, and transport （3.0145 g TEQ/year）. Jordan seeks by next years, a reduction in total releases of dioxins and furans from sources resulting from human activity. This challenge will apply to the aggregate of releases to the air nationwide and of releases to the water within the Jordan area. Jordan should conduct air monitoring for dioxin in order to track fluctuations in atmospheric deposition levels.     

Interaction in the Ce3Co8Si–H2 system

Interaction of hydrogen with Ce₃Co₈Si intermetallic compound (IMC) has been studied. IMC Ce₃Co₈Si absorbs hydrogen and forms a hydride phase at 11 atm and 50 °C. X-ray analysis of Ce₃Co₈Si H_10.2 saturated hydride phase lattice showed that it has the symmetry of the initial compound and is expanded with strong anisotropy due to increased c parameter. Analysis of hydrogen desorption isotherms in Ce₃Co₈Si–H₂ system has revealed that the decomposition of hydride phase occurred in one stage. The heat of hydride phase formation was calculated on the base of obtained equilibrium pressures data at 50, 60 and 70 °C. The results obtained demonstrate that Ce₃Co₈Si intermetallic compound may be used as reversible accumulator of hydrogen in medium temperatures interval.     

Electrocatalytic performance of Nicore@Ptshell/C core–shell nanoparticle with the Pt in nanoshell

The Ni₁@Pt_0.067 core–shell nanoparticles with a thin layer of Pt shell have been prepared by colloidal template method. The structure and composition of the prepared core–shell nanoparticles have been analyzed by using transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In addition, the electrochemical performance of the prepared nanoparticles has been analyzed by potentiodynamic polarization and cyclic voltammetry (CV), by testing their activity towards oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). Experimental results indicate that the Ni₁@Pt_0.067 particles are well distributed, with an average particle size of approximately 6 nm and shell thickness of approximately 0.5 nm–2.1 nm. Compared with Pt/C, the Ni₁@Pt_0.067/C nanoparticles prepared in this study show significantly improved catalytic activity towards ORR and MOR. However, with increase in methanol concentration in the electrolyte composed of 0.5 mol L⁻¹ H₂SO₄ + x mol L⁻¹ methanol (where, x = 0, 0.2, 0.5 and 1.0), the limiting current of MOR on Ni₁@Pt_0.067/C increase remarkably, whereas the ORR activity weakens. Based on the experimental data, we analyze the mechanism underlying the impact of methanol concentration on the ORR in Ni₁@Pt_0.067/C and find that the surface of Pt has a variety of activity sites.     

Studies in the transition from deflagration to detonation in granular explosives—II. Transitional characteristics and mechanisms observed in 91/9 RDX/Wax

The apparatus and instrumentation described in the previous paper have been used to observe the transitional behavior of burning to detonation for a 91/9 RDX/wax mixture. Transitions to detonation were observed for all densities between 67 and 95% TMD. The sequence of observed events following ignition of the explosives charge was: stable propagation of a convective flame front, compaction of the more porous burning charges, formation of a postconvective (compressive) wave in the ignition region, subsequent coalescence of compressive waves some distance beyond the ignition region, and the formation of a detonation wave 1 to 2 cm beyond the intersection of the convective and postconvective fronts. It is proposed that the shock to detonation sequence starts in the region of coalescence of compressive waves. The velocity of the convective flame front was observed to increase with increasing charge density in agreement with earlier results from ammonium picrate. The predetonation column length as a function of charge compaction exhibited a minimum; such minima have been reported by other workers for PETN, RDX, and HMX.     

Pd–Ag thin film membrane for H2 separation. Part 2. Carbon and oxygen diffusion in the presence of CO/CO2 in the feed and effect on the H2 permeability

The effect of CO and CO₂ on the performance and stability of Pd–Ag thin film membranes prepared by electroless plating deposition (EPD) was investigated, observing the presence of dissociation to carbon and oxygen which slowly diffuse in the membrane influencing also H₂ permeability. The effect of the two carbon oxides was investigated both separately and combined in the 400–450 °C temperature range over long-term cumulative experiments (up to over 350 h) on a membrane that already worked for over 350 h in H₂ or H₂–N₂ mixtures. An increase of the H₂ permeation flux was observed feeding only CO₂ in the range 10–20%. This effect was interpreted as deriving from the facilitated H₂ flux caused from oxygen diffusion (deriving from CO₂ dissociation) in the membrane. CO induces instead a partial inhibition on the H₂ flux deriving from the negative effect of CO competitive chemisorption as well as C diffusion in the membrane, which overcome the positive effect associated to oxygen diffusion in the membrane. Carbon and oxygen diffuse through the membrane with a rate two order of magnitude lower than hydrogen, and recombinate at the permeate side forming CO, CO₂ and CH₄ which amount increases with time-on-stream. The effect is reversible and not associated with the creation of cracks or defects in the membrane, as supported by leak tests.     

Decarbonising power generation in China—Is the answer blowing in the wind?

This paper examines the current situation of wind industry development, evaluates the potentials of GHG mitigation and identifies the key determinants of scaling up wind power deployment in China. China has doubled its wind capacity every year for the past 4 years, the total installed capacity reached 12 Gigawatts (GW) and surpassed the 10-GW target 2 years ahead of schedule in the national plan for renewable energy development [38], [71], [87],and would reach 100–120 GW by 2020 according to the government’s new energy plan. It may become the biggest wind power generation and wind turbines manufacturing country of the world in the next years if the abundant wind resources and enormous domestic market can be harnessed with appropriate policies and efficient technology. The recent positive move in vigorous development of wind power in China implies that the total installed capacity will far exceed the targets of the government’s 2007 renewable energy plan. However, the prosperous Chinese wind market has also revealed some worrisome signals and weakness [28], [58], such as low capacity factor and frequent outage of wind farms, inadequate grid infrastructure, long distance transmission, low quality of turbines, adverse price bidding, nepotism in wind farm developer selection process and regulatory uncertainty and policy inconsistency which all conspire to hinder effective power generation in the massively new installed wind capacities. A coherent policy framework is required for creating enabling environment for accelerating wind energy penetration and state-of-art technology deployment in the country. It is argued that institutional, financial and technical capacity will need to be cemented to exploit the huge potentials of wind resources to meet the rapidly growing demand for electricity in China in the coming decades with minimised environmental implications.     

Study of the influence of the amount of PBI–H3PO4 in the catalytic layer of a high temperature PEMFC

The influence of the amount of polybenzimidazole (PBI)-H₃PO₄ (normalized with respect to the PBI loading, which expressed as C/PBI weight ratio) content in both the anode and cathode has been studied for a PBI-based high temperature proton exchange membrane (PEM) fuel cell. The electrodes prepared with different amounts of PBI have been characterized physically, by measuring the pore size distribution, and visualizing the surface microstructure. Afterwards, the electrochemical behaviour of the electrodes has been evaluated. The catalytic electrochemical activity has been measured by voltamperometry for each electrode prepared with a different PBI content, and the cell performance results have been studied, supported by the impedance spectra, in order to determine the influence of the PBI loading in each electrode. The best results have been achieved with a C/PBI weight ratio of 20, for both the anode and the cathode. A lower C/PBI weight ratio (larger amount of PBI in the catalytic layer) reduced the electrocatalytic activity, and impaired the mass transport processes, due to the large amount of polymer covering the catalyst particle, lowering the cell performance. A higher C/PBI weight ratio (lower amount of PBI in the catalytic layer) reduced the electrocatalytic activity, and slightly increased the ohmic resistance. The low amount of the polymeric ionic carrier PBI–H₃PO₄ limited the proton mobility, despite of the presence of large amounts of “free” H₃PO₄ in the catalytic layer.     

Characteristics of the Mach Disk in the Underexpanded Jet in which the Back Pressure Continuously Changes with Time

When the high-pressure gas is exhausted to the vacuum chamber from the nozzle, the underexpanded supersonic jet contained with the Mach disk is generally formed. The eventual purpose of this study is to clarify the unsteady phenomenon of the underexpanded free jet when the back pressure continuously changes with time. The characteristic of the Mach disk has been clarified in consideration of the diameter and position of it by the numerical analysis in this paper. The sonic jet of the exit Mach number Me=1 is assumed and the axisymmetric conservational equation is solved by the TVD method in the numerical calculation. The diameter and position of the Mach disk differs with the results of a steady jet and the influence on the continuously changing of the back pressure is evidenced from the comparison with the case of steady supersonic jet.     

Apparent kinetics of the Bunsen reaction in I2/HI solution for the iodine–sulfur hydrogen production process

Massive hydrogen production featuring high efficiency, CO₂ free, and cost effectiveness is a crucial challenge for the hydrogen economy. Nuclear hydrogen production through thermochemical iodine–sulfur (IS) process is a potential candidate for this purpose. Chemical reaction kinetics data are indispensable for developing a high-performance reactor as well as the scaling up of the process. The apparent kinetics of the reaction under simulated recycling conditions of IS closed cycle operation was studied by initial rate method. The effects of key parameters, including agitation speed, SO₂ partial pressure, I₂ concentration, and reaction temperature, on reaction rate, were systematically investigated by measuring the variation in SO₂ pressure with reaction time. Initial rate analysis method indicated that the Bunsen reaction rates were 0.23 ± 0.01 and 0.77 ± 0.01 order with respect to SO₂ pressure and I₂ concentration. The apparent activation energy was 5.86 ± 0.21 kJ/mol. Based on these results, an exponential rate expression of the Bunsen reaction was established. In addition, a simplified method for calculation of kinetics parameters was proposed and compared with conventional techniques. Experimental results provide theoretical basis for design and development of Bunsen reactors and for elucidating the reaction process.     

Influence of the acid–base properties over NiSn/MgO–Al2O3 catalysts in the hydrogen production from glycerol steam reforming

In this work we have investigated the hydrogen production from glycerol steam reforming. The effect of the acid–base properties was evaluated using four catalysts based in an alloy Ni–Sn as active phase supported over γ-Al₂O₃ with different content in MgO, varying between 0 and 30 wt.% The incorporation of MgO results in the formation of MgAl₂O₄ spinel, which modifies the acid–base properties of the catalyst. Addition of MgO favored the glycerol conversion into gas, and the catalyst loaded with 10 wt.% MgO exhibited better catalytic performance and higher stability. A blank test with quartz was performed indicating that pyrolysis of glycerol takes place in the quartz.     

Renewables in Africa—meeting the energy needs of the poor

This paper presents estimates of renewables energy technologies disseminated in sub-Sahara Africa and evaluates the potential of renewables in meeting the energy needs of Africa's poor. Using data mainly from eastern and southern Africa, the paper examines five major renewable energy technologies, namely: (i) large-scale biomass energy; (ii) small-scale biomass energy (iii) solar photovoltaic; (iv) solar thermal; and (v) wind. It then evaluates how suitable each renewable energy technology is to meet the energy needs of the urban and rural poor. The paper ends with key measures that could encourage the large-scale dissemination of renewable energy technologies to the poor in Africa.     

Revision of the NaBO2–H2O phase diagram for optimized yield in the H2 generation through NaBH4 hydrolysis

The binary phase diagram NaBO₂–H₂O at ambient pressure, which defines the different phase equilibria that could be formed between borates, end-products of NaBH₄ hydrolysis, has been reviewed. Five different solid borates phases have been identified: NaBO₂·4H₂O (Na[B(OH)₄]·2H₂O), NaBO₂·2H₂O (Na[B(OH)₄]), NaBO₂·2/3H₂O (Na₃[B₃O₄(OH)₄]), NaBO₂·1/3H₂O (Na₃[B₃O₅(OH)₂]) and NaBO₂ (Na₃[B₃O₆]), and their thermal stabilities have been studied. The boundaries of the different Liquid + Solid equilibria for the temperature range from −10 to 80 °C have been determined, confirming literature data at low temperature (20–50 °C). Moreover the following eutectic transformation, Liq. → Ice + NaBO₂·4H₂O, occurring at −7 °C, has been determined by DSC. The Liquid–Vapour domain has been studied by ebullioscopy. The invariant transformation Liq. → Vap. + NaBO₂·2/3H₂O has been estimated at 131.6 °C. This knowledge is paramount in the field of hydrogen storage through NaBH₄ hydrolysis, in which borate compounds were obtained as hydrolysis reaction products. As a consequence, the authors propose a comparison with previous NaBO₂–H₂O binary phase diagrams and its consequence related to hydrogen storage through NaBH₄ hydrolysis.     

What causes the change in energy demand in the economy?: The role of technological change

This paper proposes a simple and theoretically clear approach to the estimation of technological change in a multisector general equilibrium framework. This study employs the Multiple Calibration Decomposition Analysis (MCDA) to evaluate technological change that is responsible for changes in energy use and carbon dioxide emissions in the Japanese economy in the oil crises period from 1970 to 1985. The MCDA serves as an elementary way of separating structural change due to technological change from that due to price substitution effects, capturing the interdependence among economic sectors. The empirical result provides a better understanding of the effects on the economy of technological change in that significant period.     

Assessing the Public Lighting with Solar Panels in the Sub Saharan Countries in Africa： Yaounde Case Study

Located in central Africa, Cameroon offers a wealth of solar power opportunity. The public lighting in the capital city Yaounde is an example of solar energy promotion. The purpose of this paper is among other things aiming at assessing the solar energy resources of central Africa and making sure it can be used optimally at least for public lighting. Based on the knowledge from data collected and field experience for three years, the authors will assess the implementation of the technology and show how the use of solar energy can solve some problems in the city of Yaounde even when the area is grid connected. This paper will also identify actions for improved access to sustainable, friendly, affordable solar energy services to users, as well as a significant improvement of energy infrastructure and energy efficiency in the city. The authors will also address issues on identified obstacles for the promotion of solar energy in order to help the cities in sub Saharan countries to develop a vision aiming at developing good solar energy policy and better contribute to fight against poverty and climate change.     

Marangoni Convection in the LiCaAIF_6 Crystal Growth by the Czochralski Technique

Numerical simulation of the mixed convection induced by buoyancy, crystal rotation, and also unbalanced surface tension at the melt-gas interface is conducted by means of the finite volume method in the model of the Czochralski crystal growth. The role of Marangoni convection in the heat and mass transfer is investigated by the comparison of the models with and without surface tension included, and our results indicate that Marangoni convection plays an important role in the heat and mass transfer near the interface of melt and crystal, and also the convection structure.     

Electrochemical investigation of the Bunsen reaction in the sulfur–iodine cycle

The Bunsen reaction, as a part of the sulfur–iodine thermochemical cycle, was studied using an electrochemical cell. The effects of current density, operating temperature, H₂SO₄ concentration in the anolyte, HI concentration and I₂/HI molar ratio in the catholyte were explored. Both the H₂SO₄ in anolyte and the HI in catholyte were concentrated during electrolysis. Increasing current density amplified this H₂SO₄ and HI concentration, while the other operating parameters also varied the anolyte and catholyte concentration. The transport properties of the cation exchange membrane were examined. The electrode current efficiency remained close to 100% for most runs except those at high current density. Both the average cell voltage and the heat equivalent of electric energy were determined at different conditions.     

The influence of the support composition and structure (MХZr1-XO2-δ) of bimetallic catalysts on the activity in methanol steam reforming

Metal oxide-stabilized zirconia supports (M_xZr_1-xO₂-_δ) with different dopants (M = Y, La, Ce) were prepared by coprecipitation method. Bimetallic CuNi and RuRh catalysts supported on M_xZr_1-xO₂-_δ were prepared by the sequential wetness impregnation method, for use in hydrogen production by methanol steam reforming. The effect of the nature and quantity of the dopant cation (M = Y, Ce) on the catalytic performance of zirconia supported metal catalysts was investigated. The activity of NiCu/Y_xZr_1-xO_2-(x/2) (x = 0.1–0.3) samples increases with an increase in yttrium concentration due to the formation of oxygen vacancies. The dependence of the catalytic activity on the ceria concentration was not monotonous. The sample containing 10% of cerium oxide showed the highest activity. The performance of a NiCu/La_0·1Zr_0,9O_1.95 sample was compared with the performance of a Y and Ce containing samples with the same quantity of dopant cation (10%). The La doped catalyst was more active than the yttria-containing composites, but its selectivity was lower. The catalyst based on RuRh alloy differed with significantly higher activity and lower selectivity compared with NiCu samples. The selectivity of the process was not less than 99.5% for all catalysts even at the high temperatures. At the same time, the improved activity of the catalyst also results in an increase in carbon monoxide formation while the hydrogen selectivity decreases. The optimal characteristics, such as rather high hydrogen yield, good selectivity and stability were shown by the catalyst with Ce_0·1Zr_0·9O_2-δ support.     

Cu/ZnO/Al2O3 water–gas shift catalysts for practical fuel cell applications: the performance in shut-down/start-up operation

The Cu/ZnO/Al₂O₃ catalysts were prepared by the coprecipitation method, and were evaluated in the water–gas shift (WGS) reaction. The effects of the calcination temperature on the BET surface area and crystallite size were characterized. In WGS reaction, the Cu/ZnO/Al₂O₃ catalysts suffered from continuous deactivation in shut-down/start-up operation – the daily requirement for mobile and residential fuel cell systems. Among them, the Cu/ZnO/Al₂O₃ catalyst prepared at the calcination temperature of 450 °C showed the best activity and stability, with the decrement of the CO conversion of only 12.8% after three shut-down/start-up cycles. Deactivation of the Cu/ZnO/Al₂O₃ catalysts is attributed to the blocking or deterioration of the active sites by Zn₆Al₂(OH)₁₆CO₃·4H₂O resulting from the degeneration of the oxides under cyclic operations. Removal of the hydroxycarbonate species by calcination in air followed by re-reduction could restore the steady-state WGS activity; however, the regenerated catalyst underwent much severe deactivation in subsequent shut-down/start-up operation.     

Effect of alumina on the enhancement of hydrogen production and the reduction of hydrogen peroxide in the γ-radiolysis of pure water and 0.4 M H2SO4 aqueous solution

The H₂ and H₂O₂ produced by ⁶⁰Co γ-radiation at room temperature were measured in pure water and 0.4 M H₂SO₄ aqueous solution with alumina powder. By increasing the addition of alumina powder, a strong reduction of H₂O₂ concentrations in the solutions was obtained, and the final product H₂ yields were correspondingly enhanced. These enhancement and reduction effects were diminished in the subsequent γ-radiation when irradiated alumina powder was used. The effects were reversibly restored by washing the irradiated powder with purified water. In 0.4 M H₂SO₄ solution with alumina powder, the H₂ yields increased by increasing the absorbed dose rate in the region of 1-5 kGy/h. The radiation-enhanced H₂ production correlated with the reduction of H₂O₂ concentration could be brought about by the reduction of H₂O₂ molecules and OH radicals in the solutions due to alumina powder.